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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * Implementation of the Transmission Control Protocol(TCP).
8 *
9 * Authors: Ross Biro
10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 * Mark Evans, <evansmp@uhura.aston.ac.uk>
12 * Corey Minyard <wf-rch!minyard@relay.EU.net>
13 * Florian La Roche, <flla@stud.uni-sb.de>
14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
15 * Linus Torvalds, <torvalds@cs.helsinki.fi>
16 * Alan Cox, <gw4pts@gw4pts.ampr.org>
17 * Matthew Dillon, <dillon@apollo.west.oic.com>
18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
19 * Jorge Cwik, <jorge@laser.satlink.net>
20 */
21
22/*
23 * Changes:
24 * Pedro Roque : Fast Retransmit/Recovery.
25 * Two receive queues.
26 * Retransmit queue handled by TCP.
27 * Better retransmit timer handling.
28 * New congestion avoidance.
29 * Header prediction.
30 * Variable renaming.
31 *
32 * Eric : Fast Retransmit.
33 * Randy Scott : MSS option defines.
34 * Eric Schenk : Fixes to slow start algorithm.
35 * Eric Schenk : Yet another double ACK bug.
36 * Eric Schenk : Delayed ACK bug fixes.
37 * Eric Schenk : Floyd style fast retrans war avoidance.
38 * David S. Miller : Don't allow zero congestion window.
39 * Eric Schenk : Fix retransmitter so that it sends
40 * next packet on ack of previous packet.
41 * Andi Kleen : Moved open_request checking here
42 * and process RSTs for open_requests.
43 * Andi Kleen : Better prune_queue, and other fixes.
44 * Andrey Savochkin: Fix RTT measurements in the presence of
45 * timestamps.
46 * Andrey Savochkin: Check sequence numbers correctly when
47 * removing SACKs due to in sequence incoming
48 * data segments.
49 * Andi Kleen: Make sure we never ack data there is not
50 * enough room for. Also make this condition
51 * a fatal error if it might still happen.
52 * Andi Kleen: Add tcp_measure_rcv_mss to make
53 * connections with MSS<min(MTU,ann. MSS)
54 * work without delayed acks.
55 * Andi Kleen: Process packets with PSH set in the
56 * fast path.
57 * J Hadi Salim: ECN support
58 * Andrei Gurtov,
59 * Pasi Sarolahti,
60 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
61 * engine. Lots of bugs are found.
62 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
63 */
64
65#define pr_fmt(fmt) "TCP: " fmt
66
67#include <linux/mm.h>
68#include <linux/slab.h>
69#include <linux/module.h>
70#include <linux/sysctl.h>
71#include <linux/kernel.h>
72#include <linux/prefetch.h>
73#include <net/dst.h>
74#include <net/tcp.h>
75#include <net/inet_common.h>
76#include <linux/ipsec.h>
77#include <asm/unaligned.h>
78#include <linux/errqueue.h>
79#include <trace/events/tcp.h>
80#include <linux/jump_label_ratelimit.h>
81#include <net/busy_poll.h>
82#include <net/mptcp.h>
83
84int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
85
86#define FLAG_DATA 0x01 /* Incoming frame contained data. */
87#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
88#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
89#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
90#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
91#define FLAG_DATA_SACKED 0x20 /* New SACK. */
92#define FLAG_ECE 0x40 /* ECE in this ACK */
93#define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
94#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
95#define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
96#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
97#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
98#define FLAG_SET_XMIT_TIMER 0x1000 /* Set TLP or RTO timer */
99#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
100#define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
101#define FLAG_NO_CHALLENGE_ACK 0x8000 /* do not call tcp_send_challenge_ack() */
102#define FLAG_ACK_MAYBE_DELAYED 0x10000 /* Likely a delayed ACK */
103#define FLAG_DSACK_TLP 0x20000 /* DSACK for tail loss probe */
104
105#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
106#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
107#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE|FLAG_DSACKING_ACK)
108#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
109
110#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
111#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
112
113#define REXMIT_NONE 0 /* no loss recovery to do */
114#define REXMIT_LOST 1 /* retransmit packets marked lost */
115#define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */
116
117#if IS_ENABLED(CONFIG_TLS_DEVICE)
118static DEFINE_STATIC_KEY_DEFERRED_FALSE(clean_acked_data_enabled, HZ);
119
120void clean_acked_data_enable(struct inet_connection_sock *icsk,
121 void (*cad)(struct sock *sk, u32 ack_seq))
122{
123 icsk->icsk_clean_acked = cad;
124 static_branch_deferred_inc(&clean_acked_data_enabled);
125}
126EXPORT_SYMBOL_GPL(clean_acked_data_enable);
127
128void clean_acked_data_disable(struct inet_connection_sock *icsk)
129{
130 static_branch_slow_dec_deferred(&clean_acked_data_enabled);
131 icsk->icsk_clean_acked = NULL;
132}
133EXPORT_SYMBOL_GPL(clean_acked_data_disable);
134
135void clean_acked_data_flush(void)
136{
137 static_key_deferred_flush(&clean_acked_data_enabled);
138}
139EXPORT_SYMBOL_GPL(clean_acked_data_flush);
140#endif
141
142#ifdef CONFIG_CGROUP_BPF
143static void bpf_skops_parse_hdr(struct sock *sk, struct sk_buff *skb)
144{
145 bool unknown_opt = tcp_sk(sk)->rx_opt.saw_unknown &&
146 BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk),
147 BPF_SOCK_OPS_PARSE_UNKNOWN_HDR_OPT_CB_FLAG);
148 bool parse_all_opt = BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk),
149 BPF_SOCK_OPS_PARSE_ALL_HDR_OPT_CB_FLAG);
150 struct bpf_sock_ops_kern sock_ops;
151
152 if (likely(!unknown_opt && !parse_all_opt))
153 return;
154
155 /* The skb will be handled in the
156 * bpf_skops_established() or
157 * bpf_skops_write_hdr_opt().
158 */
159 switch (sk->sk_state) {
160 case TCP_SYN_RECV:
161 case TCP_SYN_SENT:
162 case TCP_LISTEN:
163 return;
164 }
165
166 sock_owned_by_me(sk);
167
168 memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
169 sock_ops.op = BPF_SOCK_OPS_PARSE_HDR_OPT_CB;
170 sock_ops.is_fullsock = 1;
171 sock_ops.sk = sk;
172 bpf_skops_init_skb(&sock_ops, skb, tcp_hdrlen(skb));
173
174 BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
175}
176
177static void bpf_skops_established(struct sock *sk, int bpf_op,
178 struct sk_buff *skb)
179{
180 struct bpf_sock_ops_kern sock_ops;
181
182 sock_owned_by_me(sk);
183
184 memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
185 sock_ops.op = bpf_op;
186 sock_ops.is_fullsock = 1;
187 sock_ops.sk = sk;
188 /* sk with TCP_REPAIR_ON does not have skb in tcp_finish_connect */
189 if (skb)
190 bpf_skops_init_skb(&sock_ops, skb, tcp_hdrlen(skb));
191
192 BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
193}
194#else
195static void bpf_skops_parse_hdr(struct sock *sk, struct sk_buff *skb)
196{
197}
198
199static void bpf_skops_established(struct sock *sk, int bpf_op,
200 struct sk_buff *skb)
201{
202}
203#endif
204
205static __cold void tcp_gro_dev_warn(const struct sock *sk, const struct sk_buff *skb,
206 unsigned int len)
207{
208 struct net_device *dev;
209
210 rcu_read_lock();
211 dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif);
212 if (!dev || len >= READ_ONCE(dev->mtu))
213 pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n",
214 dev ? dev->name : "Unknown driver");
215 rcu_read_unlock();
216}
217
218/* Adapt the MSS value used to make delayed ack decision to the
219 * real world.
220 */
221static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
222{
223 struct inet_connection_sock *icsk = inet_csk(sk);
224 const unsigned int lss = icsk->icsk_ack.last_seg_size;
225 unsigned int len;
226
227 icsk->icsk_ack.last_seg_size = 0;
228
229 /* skb->len may jitter because of SACKs, even if peer
230 * sends good full-sized frames.
231 */
232 len = skb_shinfo(skb)->gso_size ? : skb->len;
233 if (len >= icsk->icsk_ack.rcv_mss) {
234 /* Note: divides are still a bit expensive.
235 * For the moment, only adjust scaling_ratio
236 * when we update icsk_ack.rcv_mss.
237 */
238 if (unlikely(len != icsk->icsk_ack.rcv_mss)) {
239 u64 val = (u64)skb->len << TCP_RMEM_TO_WIN_SCALE;
240
241 do_div(val, skb->truesize);
242 tcp_sk(sk)->scaling_ratio = val ? val : 1;
243 }
244 icsk->icsk_ack.rcv_mss = min_t(unsigned int, len,
245 tcp_sk(sk)->advmss);
246 /* Account for possibly-removed options */
247 DO_ONCE_LITE_IF(len > icsk->icsk_ack.rcv_mss + MAX_TCP_OPTION_SPACE,
248 tcp_gro_dev_warn, sk, skb, len);
249 /* If the skb has a len of exactly 1*MSS and has the PSH bit
250 * set then it is likely the end of an application write. So
251 * more data may not be arriving soon, and yet the data sender
252 * may be waiting for an ACK if cwnd-bound or using TX zero
253 * copy. So we set ICSK_ACK_PUSHED here so that
254 * tcp_cleanup_rbuf() will send an ACK immediately if the app
255 * reads all of the data and is not ping-pong. If len > MSS
256 * then this logic does not matter (and does not hurt) because
257 * tcp_cleanup_rbuf() will always ACK immediately if the app
258 * reads data and there is more than an MSS of unACKed data.
259 */
260 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_PSH)
261 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
262 } else {
263 /* Otherwise, we make more careful check taking into account,
264 * that SACKs block is variable.
265 *
266 * "len" is invariant segment length, including TCP header.
267 */
268 len += skb->data - skb_transport_header(skb);
269 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) ||
270 /* If PSH is not set, packet should be
271 * full sized, provided peer TCP is not badly broken.
272 * This observation (if it is correct 8)) allows
273 * to handle super-low mtu links fairly.
274 */
275 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
276 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
277 /* Subtract also invariant (if peer is RFC compliant),
278 * tcp header plus fixed timestamp option length.
279 * Resulting "len" is MSS free of SACK jitter.
280 */
281 len -= tcp_sk(sk)->tcp_header_len;
282 icsk->icsk_ack.last_seg_size = len;
283 if (len == lss) {
284 icsk->icsk_ack.rcv_mss = len;
285 return;
286 }
287 }
288 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
289 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
290 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
291 }
292}
293
294static void tcp_incr_quickack(struct sock *sk, unsigned int max_quickacks)
295{
296 struct inet_connection_sock *icsk = inet_csk(sk);
297 unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
298
299 if (quickacks == 0)
300 quickacks = 2;
301 quickacks = min(quickacks, max_quickacks);
302 if (quickacks > icsk->icsk_ack.quick)
303 icsk->icsk_ack.quick = quickacks;
304}
305
306static void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks)
307{
308 struct inet_connection_sock *icsk = inet_csk(sk);
309
310 tcp_incr_quickack(sk, max_quickacks);
311 inet_csk_exit_pingpong_mode(sk);
312 icsk->icsk_ack.ato = TCP_ATO_MIN;
313}
314
315/* Send ACKs quickly, if "quick" count is not exhausted
316 * and the session is not interactive.
317 */
318
319static bool tcp_in_quickack_mode(struct sock *sk)
320{
321 const struct inet_connection_sock *icsk = inet_csk(sk);
322 const struct dst_entry *dst = __sk_dst_get(sk);
323
324 return (dst && dst_metric(dst, RTAX_QUICKACK)) ||
325 (icsk->icsk_ack.quick && !inet_csk_in_pingpong_mode(sk));
326}
327
328static void tcp_ecn_queue_cwr(struct tcp_sock *tp)
329{
330 if (tp->ecn_flags & TCP_ECN_OK)
331 tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
332}
333
334static void tcp_ecn_accept_cwr(struct sock *sk, const struct sk_buff *skb)
335{
336 if (tcp_hdr(skb)->cwr) {
337 tcp_sk(sk)->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
338
339 /* If the sender is telling us it has entered CWR, then its
340 * cwnd may be very low (even just 1 packet), so we should ACK
341 * immediately.
342 */
343 if (TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq)
344 inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
345 }
346}
347
348static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp)
349{
350 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
351}
352
353static void __tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb)
354{
355 struct tcp_sock *tp = tcp_sk(sk);
356
357 switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) {
358 case INET_ECN_NOT_ECT:
359 /* Funny extension: if ECT is not set on a segment,
360 * and we already seen ECT on a previous segment,
361 * it is probably a retransmit.
362 */
363 if (tp->ecn_flags & TCP_ECN_SEEN)
364 tcp_enter_quickack_mode(sk, 2);
365 break;
366 case INET_ECN_CE:
367 if (tcp_ca_needs_ecn(sk))
368 tcp_ca_event(sk, CA_EVENT_ECN_IS_CE);
369
370 if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {
371 /* Better not delay acks, sender can have a very low cwnd */
372 tcp_enter_quickack_mode(sk, 2);
373 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
374 }
375 tp->ecn_flags |= TCP_ECN_SEEN;
376 break;
377 default:
378 if (tcp_ca_needs_ecn(sk))
379 tcp_ca_event(sk, CA_EVENT_ECN_NO_CE);
380 tp->ecn_flags |= TCP_ECN_SEEN;
381 break;
382 }
383}
384
385static void tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb)
386{
387 if (tcp_sk(sk)->ecn_flags & TCP_ECN_OK)
388 __tcp_ecn_check_ce(sk, skb);
389}
390
391static void tcp_ecn_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th)
392{
393 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
394 tp->ecn_flags &= ~TCP_ECN_OK;
395}
396
397static void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th)
398{
399 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
400 tp->ecn_flags &= ~TCP_ECN_OK;
401}
402
403static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th)
404{
405 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
406 return true;
407 return false;
408}
409
410/* Buffer size and advertised window tuning.
411 *
412 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
413 */
414
415static void tcp_sndbuf_expand(struct sock *sk)
416{
417 const struct tcp_sock *tp = tcp_sk(sk);
418 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
419 int sndmem, per_mss;
420 u32 nr_segs;
421
422 /* Worst case is non GSO/TSO : each frame consumes one skb
423 * and skb->head is kmalloced using power of two area of memory
424 */
425 per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
426 MAX_TCP_HEADER +
427 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
428
429 per_mss = roundup_pow_of_two(per_mss) +
430 SKB_DATA_ALIGN(sizeof(struct sk_buff));
431
432 nr_segs = max_t(u32, TCP_INIT_CWND, tcp_snd_cwnd(tp));
433 nr_segs = max_t(u32, nr_segs, tp->reordering + 1);
434
435 /* Fast Recovery (RFC 5681 3.2) :
436 * Cubic needs 1.7 factor, rounded to 2 to include
437 * extra cushion (application might react slowly to EPOLLOUT)
438 */
439 sndmem = ca_ops->sndbuf_expand ? ca_ops->sndbuf_expand(sk) : 2;
440 sndmem *= nr_segs * per_mss;
441
442 if (sk->sk_sndbuf < sndmem)
443 WRITE_ONCE(sk->sk_sndbuf,
444 min(sndmem, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[2])));
445}
446
447/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
448 *
449 * All tcp_full_space() is split to two parts: "network" buffer, allocated
450 * forward and advertised in receiver window (tp->rcv_wnd) and
451 * "application buffer", required to isolate scheduling/application
452 * latencies from network.
453 * window_clamp is maximal advertised window. It can be less than
454 * tcp_full_space(), in this case tcp_full_space() - window_clamp
455 * is reserved for "application" buffer. The less window_clamp is
456 * the smoother our behaviour from viewpoint of network, but the lower
457 * throughput and the higher sensitivity of the connection to losses. 8)
458 *
459 * rcv_ssthresh is more strict window_clamp used at "slow start"
460 * phase to predict further behaviour of this connection.
461 * It is used for two goals:
462 * - to enforce header prediction at sender, even when application
463 * requires some significant "application buffer". It is check #1.
464 * - to prevent pruning of receive queue because of misprediction
465 * of receiver window. Check #2.
466 *
467 * The scheme does not work when sender sends good segments opening
468 * window and then starts to feed us spaghetti. But it should work
469 * in common situations. Otherwise, we have to rely on queue collapsing.
470 */
471
472/* Slow part of check#2. */
473static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb,
474 unsigned int skbtruesize)
475{
476 const struct tcp_sock *tp = tcp_sk(sk);
477 /* Optimize this! */
478 int truesize = tcp_win_from_space(sk, skbtruesize) >> 1;
479 int window = tcp_win_from_space(sk, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2])) >> 1;
480
481 while (tp->rcv_ssthresh <= window) {
482 if (truesize <= skb->len)
483 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
484
485 truesize >>= 1;
486 window >>= 1;
487 }
488 return 0;
489}
490
491/* Even if skb appears to have a bad len/truesize ratio, TCP coalescing
492 * can play nice with us, as sk_buff and skb->head might be either
493 * freed or shared with up to MAX_SKB_FRAGS segments.
494 * Only give a boost to drivers using page frag(s) to hold the frame(s),
495 * and if no payload was pulled in skb->head before reaching us.
496 */
497static u32 truesize_adjust(bool adjust, const struct sk_buff *skb)
498{
499 u32 truesize = skb->truesize;
500
501 if (adjust && !skb_headlen(skb)) {
502 truesize -= SKB_TRUESIZE(skb_end_offset(skb));
503 /* paranoid check, some drivers might be buggy */
504 if (unlikely((int)truesize < (int)skb->len))
505 truesize = skb->truesize;
506 }
507 return truesize;
508}
509
510static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb,
511 bool adjust)
512{
513 struct tcp_sock *tp = tcp_sk(sk);
514 int room;
515
516 room = min_t(int, tp->window_clamp, tcp_space(sk)) - tp->rcv_ssthresh;
517
518 if (room <= 0)
519 return;
520
521 /* Check #1 */
522 if (!tcp_under_memory_pressure(sk)) {
523 unsigned int truesize = truesize_adjust(adjust, skb);
524 int incr;
525
526 /* Check #2. Increase window, if skb with such overhead
527 * will fit to rcvbuf in future.
528 */
529 if (tcp_win_from_space(sk, truesize) <= skb->len)
530 incr = 2 * tp->advmss;
531 else
532 incr = __tcp_grow_window(sk, skb, truesize);
533
534 if (incr) {
535 incr = max_t(int, incr, 2 * skb->len);
536 tp->rcv_ssthresh += min(room, incr);
537 inet_csk(sk)->icsk_ack.quick |= 1;
538 }
539 } else {
540 /* Under pressure:
541 * Adjust rcv_ssthresh according to reserved mem
542 */
543 tcp_adjust_rcv_ssthresh(sk);
544 }
545}
546
547/* 3. Try to fixup all. It is made immediately after connection enters
548 * established state.
549 */
550static void tcp_init_buffer_space(struct sock *sk)
551{
552 int tcp_app_win = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_app_win);
553 struct tcp_sock *tp = tcp_sk(sk);
554 int maxwin;
555
556 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
557 tcp_sndbuf_expand(sk);
558
559 tcp_mstamp_refresh(tp);
560 tp->rcvq_space.time = tp->tcp_mstamp;
561 tp->rcvq_space.seq = tp->copied_seq;
562
563 maxwin = tcp_full_space(sk);
564
565 if (tp->window_clamp >= maxwin) {
566 tp->window_clamp = maxwin;
567
568 if (tcp_app_win && maxwin > 4 * tp->advmss)
569 tp->window_clamp = max(maxwin -
570 (maxwin >> tcp_app_win),
571 4 * tp->advmss);
572 }
573
574 /* Force reservation of one segment. */
575 if (tcp_app_win &&
576 tp->window_clamp > 2 * tp->advmss &&
577 tp->window_clamp + tp->advmss > maxwin)
578 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
579
580 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
581 tp->snd_cwnd_stamp = tcp_jiffies32;
582 tp->rcvq_space.space = min3(tp->rcv_ssthresh, tp->rcv_wnd,
583 (u32)TCP_INIT_CWND * tp->advmss);
584}
585
586/* 4. Recalculate window clamp after socket hit its memory bounds. */
587static void tcp_clamp_window(struct sock *sk)
588{
589 struct tcp_sock *tp = tcp_sk(sk);
590 struct inet_connection_sock *icsk = inet_csk(sk);
591 struct net *net = sock_net(sk);
592 int rmem2;
593
594 icsk->icsk_ack.quick = 0;
595 rmem2 = READ_ONCE(net->ipv4.sysctl_tcp_rmem[2]);
596
597 if (sk->sk_rcvbuf < rmem2 &&
598 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
599 !tcp_under_memory_pressure(sk) &&
600 sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) {
601 WRITE_ONCE(sk->sk_rcvbuf,
602 min(atomic_read(&sk->sk_rmem_alloc), rmem2));
603 }
604 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
605 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
606}
607
608/* Initialize RCV_MSS value.
609 * RCV_MSS is an our guess about MSS used by the peer.
610 * We haven't any direct information about the MSS.
611 * It's better to underestimate the RCV_MSS rather than overestimate.
612 * Overestimations make us ACKing less frequently than needed.
613 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
614 */
615void tcp_initialize_rcv_mss(struct sock *sk)
616{
617 const struct tcp_sock *tp = tcp_sk(sk);
618 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
619
620 hint = min(hint, tp->rcv_wnd / 2);
621 hint = min(hint, TCP_MSS_DEFAULT);
622 hint = max(hint, TCP_MIN_MSS);
623
624 inet_csk(sk)->icsk_ack.rcv_mss = hint;
625}
626EXPORT_SYMBOL(tcp_initialize_rcv_mss);
627
628/* Receiver "autotuning" code.
629 *
630 * The algorithm for RTT estimation w/o timestamps is based on
631 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
632 * <https://public.lanl.gov/radiant/pubs.html#DRS>
633 *
634 * More detail on this code can be found at
635 * <http://staff.psc.edu/jheffner/>,
636 * though this reference is out of date. A new paper
637 * is pending.
638 */
639static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
640{
641 u32 new_sample = tp->rcv_rtt_est.rtt_us;
642 long m = sample;
643
644 if (new_sample != 0) {
645 /* If we sample in larger samples in the non-timestamp
646 * case, we could grossly overestimate the RTT especially
647 * with chatty applications or bulk transfer apps which
648 * are stalled on filesystem I/O.
649 *
650 * Also, since we are only going for a minimum in the
651 * non-timestamp case, we do not smooth things out
652 * else with timestamps disabled convergence takes too
653 * long.
654 */
655 if (!win_dep) {
656 m -= (new_sample >> 3);
657 new_sample += m;
658 } else {
659 m <<= 3;
660 if (m < new_sample)
661 new_sample = m;
662 }
663 } else {
664 /* No previous measure. */
665 new_sample = m << 3;
666 }
667
668 tp->rcv_rtt_est.rtt_us = new_sample;
669}
670
671static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
672{
673 u32 delta_us;
674
675 if (tp->rcv_rtt_est.time == 0)
676 goto new_measure;
677 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
678 return;
679 delta_us = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcv_rtt_est.time);
680 if (!delta_us)
681 delta_us = 1;
682 tcp_rcv_rtt_update(tp, delta_us, 1);
683
684new_measure:
685 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
686 tp->rcv_rtt_est.time = tp->tcp_mstamp;
687}
688
689static s32 tcp_rtt_tsopt_us(const struct tcp_sock *tp)
690{
691 u32 delta, delta_us;
692
693 delta = tcp_time_stamp_ts(tp) - tp->rx_opt.rcv_tsecr;
694 if (tp->tcp_usec_ts)
695 return delta;
696
697 if (likely(delta < INT_MAX / (USEC_PER_SEC / TCP_TS_HZ))) {
698 if (!delta)
699 delta = 1;
700 delta_us = delta * (USEC_PER_SEC / TCP_TS_HZ);
701 return delta_us;
702 }
703 return -1;
704}
705
706static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
707 const struct sk_buff *skb)
708{
709 struct tcp_sock *tp = tcp_sk(sk);
710
711 if (tp->rx_opt.rcv_tsecr == tp->rcv_rtt_last_tsecr)
712 return;
713 tp->rcv_rtt_last_tsecr = tp->rx_opt.rcv_tsecr;
714
715 if (TCP_SKB_CB(skb)->end_seq -
716 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss) {
717 s32 delta = tcp_rtt_tsopt_us(tp);
718
719 if (delta >= 0)
720 tcp_rcv_rtt_update(tp, delta, 0);
721 }
722}
723
724/*
725 * This function should be called every time data is copied to user space.
726 * It calculates the appropriate TCP receive buffer space.
727 */
728void tcp_rcv_space_adjust(struct sock *sk)
729{
730 struct tcp_sock *tp = tcp_sk(sk);
731 u32 copied;
732 int time;
733
734 trace_tcp_rcv_space_adjust(sk);
735
736 tcp_mstamp_refresh(tp);
737 time = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcvq_space.time);
738 if (time < (tp->rcv_rtt_est.rtt_us >> 3) || tp->rcv_rtt_est.rtt_us == 0)
739 return;
740
741 /* Number of bytes copied to user in last RTT */
742 copied = tp->copied_seq - tp->rcvq_space.seq;
743 if (copied <= tp->rcvq_space.space)
744 goto new_measure;
745
746 /* A bit of theory :
747 * copied = bytes received in previous RTT, our base window
748 * To cope with packet losses, we need a 2x factor
749 * To cope with slow start, and sender growing its cwin by 100 %
750 * every RTT, we need a 4x factor, because the ACK we are sending
751 * now is for the next RTT, not the current one :
752 * <prev RTT . ><current RTT .. ><next RTT .... >
753 */
754
755 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf) &&
756 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
757 u64 rcvwin, grow;
758 int rcvbuf;
759
760 /* minimal window to cope with packet losses, assuming
761 * steady state. Add some cushion because of small variations.
762 */
763 rcvwin = ((u64)copied << 1) + 16 * tp->advmss;
764
765 /* Accommodate for sender rate increase (eg. slow start) */
766 grow = rcvwin * (copied - tp->rcvq_space.space);
767 do_div(grow, tp->rcvq_space.space);
768 rcvwin += (grow << 1);
769
770 rcvbuf = min_t(u64, tcp_space_from_win(sk, rcvwin),
771 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]));
772 if (rcvbuf > sk->sk_rcvbuf) {
773 WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);
774
775 /* Make the window clamp follow along. */
776 tp->window_clamp = tcp_win_from_space(sk, rcvbuf);
777 }
778 }
779 tp->rcvq_space.space = copied;
780
781new_measure:
782 tp->rcvq_space.seq = tp->copied_seq;
783 tp->rcvq_space.time = tp->tcp_mstamp;
784}
785
786static void tcp_save_lrcv_flowlabel(struct sock *sk, const struct sk_buff *skb)
787{
788#if IS_ENABLED(CONFIG_IPV6)
789 struct inet_connection_sock *icsk = inet_csk(sk);
790
791 if (skb->protocol == htons(ETH_P_IPV6))
792 icsk->icsk_ack.lrcv_flowlabel = ntohl(ip6_flowlabel(ipv6_hdr(skb)));
793#endif
794}
795
796/* There is something which you must keep in mind when you analyze the
797 * behavior of the tp->ato delayed ack timeout interval. When a
798 * connection starts up, we want to ack as quickly as possible. The
799 * problem is that "good" TCP's do slow start at the beginning of data
800 * transmission. The means that until we send the first few ACK's the
801 * sender will sit on his end and only queue most of his data, because
802 * he can only send snd_cwnd unacked packets at any given time. For
803 * each ACK we send, he increments snd_cwnd and transmits more of his
804 * queue. -DaveM
805 */
806static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
807{
808 struct tcp_sock *tp = tcp_sk(sk);
809 struct inet_connection_sock *icsk = inet_csk(sk);
810 u32 now;
811
812 inet_csk_schedule_ack(sk);
813
814 tcp_measure_rcv_mss(sk, skb);
815
816 tcp_rcv_rtt_measure(tp);
817
818 now = tcp_jiffies32;
819
820 if (!icsk->icsk_ack.ato) {
821 /* The _first_ data packet received, initialize
822 * delayed ACK engine.
823 */
824 tcp_incr_quickack(sk, TCP_MAX_QUICKACKS);
825 icsk->icsk_ack.ato = TCP_ATO_MIN;
826 } else {
827 int m = now - icsk->icsk_ack.lrcvtime;
828
829 if (m <= TCP_ATO_MIN / 2) {
830 /* The fastest case is the first. */
831 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
832 } else if (m < icsk->icsk_ack.ato) {
833 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
834 if (icsk->icsk_ack.ato > icsk->icsk_rto)
835 icsk->icsk_ack.ato = icsk->icsk_rto;
836 } else if (m > icsk->icsk_rto) {
837 /* Too long gap. Apparently sender failed to
838 * restart window, so that we send ACKs quickly.
839 */
840 tcp_incr_quickack(sk, TCP_MAX_QUICKACKS);
841 }
842 }
843 icsk->icsk_ack.lrcvtime = now;
844 tcp_save_lrcv_flowlabel(sk, skb);
845
846 tcp_ecn_check_ce(sk, skb);
847
848 if (skb->len >= 128)
849 tcp_grow_window(sk, skb, true);
850}
851
852/* Called to compute a smoothed rtt estimate. The data fed to this
853 * routine either comes from timestamps, or from segments that were
854 * known _not_ to have been retransmitted [see Karn/Partridge
855 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
856 * piece by Van Jacobson.
857 * NOTE: the next three routines used to be one big routine.
858 * To save cycles in the RFC 1323 implementation it was better to break
859 * it up into three procedures. -- erics
860 */
861static void tcp_rtt_estimator(struct sock *sk, long mrtt_us)
862{
863 struct tcp_sock *tp = tcp_sk(sk);
864 long m = mrtt_us; /* RTT */
865 u32 srtt = tp->srtt_us;
866
867 /* The following amusing code comes from Jacobson's
868 * article in SIGCOMM '88. Note that rtt and mdev
869 * are scaled versions of rtt and mean deviation.
870 * This is designed to be as fast as possible
871 * m stands for "measurement".
872 *
873 * On a 1990 paper the rto value is changed to:
874 * RTO = rtt + 4 * mdev
875 *
876 * Funny. This algorithm seems to be very broken.
877 * These formulae increase RTO, when it should be decreased, increase
878 * too slowly, when it should be increased quickly, decrease too quickly
879 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
880 * does not matter how to _calculate_ it. Seems, it was trap
881 * that VJ failed to avoid. 8)
882 */
883 if (srtt != 0) {
884 m -= (srtt >> 3); /* m is now error in rtt est */
885 srtt += m; /* rtt = 7/8 rtt + 1/8 new */
886 if (m < 0) {
887 m = -m; /* m is now abs(error) */
888 m -= (tp->mdev_us >> 2); /* similar update on mdev */
889 /* This is similar to one of Eifel findings.
890 * Eifel blocks mdev updates when rtt decreases.
891 * This solution is a bit different: we use finer gain
892 * for mdev in this case (alpha*beta).
893 * Like Eifel it also prevents growth of rto,
894 * but also it limits too fast rto decreases,
895 * happening in pure Eifel.
896 */
897 if (m > 0)
898 m >>= 3;
899 } else {
900 m -= (tp->mdev_us >> 2); /* similar update on mdev */
901 }
902 tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */
903 if (tp->mdev_us > tp->mdev_max_us) {
904 tp->mdev_max_us = tp->mdev_us;
905 if (tp->mdev_max_us > tp->rttvar_us)
906 tp->rttvar_us = tp->mdev_max_us;
907 }
908 if (after(tp->snd_una, tp->rtt_seq)) {
909 if (tp->mdev_max_us < tp->rttvar_us)
910 tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2;
911 tp->rtt_seq = tp->snd_nxt;
912 tp->mdev_max_us = tcp_rto_min_us(sk);
913
914 tcp_bpf_rtt(sk);
915 }
916 } else {
917 /* no previous measure. */
918 srtt = m << 3; /* take the measured time to be rtt */
919 tp->mdev_us = m << 1; /* make sure rto = 3*rtt */
920 tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk));
921 tp->mdev_max_us = tp->rttvar_us;
922 tp->rtt_seq = tp->snd_nxt;
923
924 tcp_bpf_rtt(sk);
925 }
926 tp->srtt_us = max(1U, srtt);
927}
928
929static void tcp_update_pacing_rate(struct sock *sk)
930{
931 const struct tcp_sock *tp = tcp_sk(sk);
932 u64 rate;
933
934 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
935 rate = (u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3);
936
937 /* current rate is (cwnd * mss) / srtt
938 * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
939 * In Congestion Avoidance phase, set it to 120 % the current rate.
940 *
941 * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
942 * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
943 * end of slow start and should slow down.
944 */
945 if (tcp_snd_cwnd(tp) < tp->snd_ssthresh / 2)
946 rate *= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_pacing_ss_ratio);
947 else
948 rate *= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_pacing_ca_ratio);
949
950 rate *= max(tcp_snd_cwnd(tp), tp->packets_out);
951
952 if (likely(tp->srtt_us))
953 do_div(rate, tp->srtt_us);
954
955 /* WRITE_ONCE() is needed because sch_fq fetches sk_pacing_rate
956 * without any lock. We want to make sure compiler wont store
957 * intermediate values in this location.
958 */
959 WRITE_ONCE(sk->sk_pacing_rate,
960 min_t(u64, rate, READ_ONCE(sk->sk_max_pacing_rate)));
961}
962
963/* Calculate rto without backoff. This is the second half of Van Jacobson's
964 * routine referred to above.
965 */
966static void tcp_set_rto(struct sock *sk)
967{
968 const struct tcp_sock *tp = tcp_sk(sk);
969 /* Old crap is replaced with new one. 8)
970 *
971 * More seriously:
972 * 1. If rtt variance happened to be less 50msec, it is hallucination.
973 * It cannot be less due to utterly erratic ACK generation made
974 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
975 * to do with delayed acks, because at cwnd>2 true delack timeout
976 * is invisible. Actually, Linux-2.4 also generates erratic
977 * ACKs in some circumstances.
978 */
979 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp);
980
981 /* 2. Fixups made earlier cannot be right.
982 * If we do not estimate RTO correctly without them,
983 * all the algo is pure shit and should be replaced
984 * with correct one. It is exactly, which we pretend to do.
985 */
986
987 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
988 * guarantees that rto is higher.
989 */
990 tcp_bound_rto(sk);
991}
992
993__u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst)
994{
995 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
996
997 if (!cwnd)
998 cwnd = TCP_INIT_CWND;
999 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
1000}
1001
1002struct tcp_sacktag_state {
1003 /* Timestamps for earliest and latest never-retransmitted segment
1004 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1005 * but congestion control should still get an accurate delay signal.
1006 */
1007 u64 first_sackt;
1008 u64 last_sackt;
1009 u32 reord;
1010 u32 sack_delivered;
1011 int flag;
1012 unsigned int mss_now;
1013 struct rate_sample *rate;
1014};
1015
1016/* Take a notice that peer is sending D-SACKs. Skip update of data delivery
1017 * and spurious retransmission information if this DSACK is unlikely caused by
1018 * sender's action:
1019 * - DSACKed sequence range is larger than maximum receiver's window.
1020 * - Total no. of DSACKed segments exceed the total no. of retransmitted segs.
1021 */
1022static u32 tcp_dsack_seen(struct tcp_sock *tp, u32 start_seq,
1023 u32 end_seq, struct tcp_sacktag_state *state)
1024{
1025 u32 seq_len, dup_segs = 1;
1026
1027 if (!before(start_seq, end_seq))
1028 return 0;
1029
1030 seq_len = end_seq - start_seq;
1031 /* Dubious DSACK: DSACKed range greater than maximum advertised rwnd */
1032 if (seq_len > tp->max_window)
1033 return 0;
1034 if (seq_len > tp->mss_cache)
1035 dup_segs = DIV_ROUND_UP(seq_len, tp->mss_cache);
1036 else if (tp->tlp_high_seq && tp->tlp_high_seq == end_seq)
1037 state->flag |= FLAG_DSACK_TLP;
1038
1039 tp->dsack_dups += dup_segs;
1040 /* Skip the DSACK if dup segs weren't retransmitted by sender */
1041 if (tp->dsack_dups > tp->total_retrans)
1042 return 0;
1043
1044 tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
1045 /* We increase the RACK ordering window in rounds where we receive
1046 * DSACKs that may have been due to reordering causing RACK to trigger
1047 * a spurious fast recovery. Thus RACK ignores DSACKs that happen
1048 * without having seen reordering, or that match TLP probes (TLP
1049 * is timer-driven, not triggered by RACK).
1050 */
1051 if (tp->reord_seen && !(state->flag & FLAG_DSACK_TLP))
1052 tp->rack.dsack_seen = 1;
1053
1054 state->flag |= FLAG_DSACKING_ACK;
1055 /* A spurious retransmission is delivered */
1056 state->sack_delivered += dup_segs;
1057
1058 return dup_segs;
1059}
1060
1061/* It's reordering when higher sequence was delivered (i.e. sacked) before
1062 * some lower never-retransmitted sequence ("low_seq"). The maximum reordering
1063 * distance is approximated in full-mss packet distance ("reordering").
1064 */
1065static void tcp_check_sack_reordering(struct sock *sk, const u32 low_seq,
1066 const int ts)
1067{
1068 struct tcp_sock *tp = tcp_sk(sk);
1069 const u32 mss = tp->mss_cache;
1070 u32 fack, metric;
1071
1072 fack = tcp_highest_sack_seq(tp);
1073 if (!before(low_seq, fack))
1074 return;
1075
1076 metric = fack - low_seq;
1077 if ((metric > tp->reordering * mss) && mss) {
1078#if FASTRETRANS_DEBUG > 1
1079 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
1080 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
1081 tp->reordering,
1082 0,
1083 tp->sacked_out,
1084 tp->undo_marker ? tp->undo_retrans : 0);
1085#endif
1086 tp->reordering = min_t(u32, (metric + mss - 1) / mss,
1087 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering));
1088 }
1089
1090 /* This exciting event is worth to be remembered. 8) */
1091 tp->reord_seen++;
1092 NET_INC_STATS(sock_net(sk),
1093 ts ? LINUX_MIB_TCPTSREORDER : LINUX_MIB_TCPSACKREORDER);
1094}
1095
1096 /* This must be called before lost_out or retrans_out are updated
1097 * on a new loss, because we want to know if all skbs previously
1098 * known to be lost have already been retransmitted, indicating
1099 * that this newly lost skb is our next skb to retransmit.
1100 */
1101static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
1102{
1103 if ((!tp->retransmit_skb_hint && tp->retrans_out >= tp->lost_out) ||
1104 (tp->retransmit_skb_hint &&
1105 before(TCP_SKB_CB(skb)->seq,
1106 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)))
1107 tp->retransmit_skb_hint = skb;
1108}
1109
1110/* Sum the number of packets on the wire we have marked as lost, and
1111 * notify the congestion control module that the given skb was marked lost.
1112 */
1113static void tcp_notify_skb_loss_event(struct tcp_sock *tp, const struct sk_buff *skb)
1114{
1115 tp->lost += tcp_skb_pcount(skb);
1116}
1117
1118void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb)
1119{
1120 __u8 sacked = TCP_SKB_CB(skb)->sacked;
1121 struct tcp_sock *tp = tcp_sk(sk);
1122
1123 if (sacked & TCPCB_SACKED_ACKED)
1124 return;
1125
1126 tcp_verify_retransmit_hint(tp, skb);
1127 if (sacked & TCPCB_LOST) {
1128 if (sacked & TCPCB_SACKED_RETRANS) {
1129 /* Account for retransmits that are lost again */
1130 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1131 tp->retrans_out -= tcp_skb_pcount(skb);
1132 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT,
1133 tcp_skb_pcount(skb));
1134 tcp_notify_skb_loss_event(tp, skb);
1135 }
1136 } else {
1137 tp->lost_out += tcp_skb_pcount(skb);
1138 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1139 tcp_notify_skb_loss_event(tp, skb);
1140 }
1141}
1142
1143/* Updates the delivered and delivered_ce counts */
1144static void tcp_count_delivered(struct tcp_sock *tp, u32 delivered,
1145 bool ece_ack)
1146{
1147 tp->delivered += delivered;
1148 if (ece_ack)
1149 tp->delivered_ce += delivered;
1150}
1151
1152/* This procedure tags the retransmission queue when SACKs arrive.
1153 *
1154 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1155 * Packets in queue with these bits set are counted in variables
1156 * sacked_out, retrans_out and lost_out, correspondingly.
1157 *
1158 * Valid combinations are:
1159 * Tag InFlight Description
1160 * 0 1 - orig segment is in flight.
1161 * S 0 - nothing flies, orig reached receiver.
1162 * L 0 - nothing flies, orig lost by net.
1163 * R 2 - both orig and retransmit are in flight.
1164 * L|R 1 - orig is lost, retransmit is in flight.
1165 * S|R 1 - orig reached receiver, retrans is still in flight.
1166 * (L|S|R is logically valid, it could occur when L|R is sacked,
1167 * but it is equivalent to plain S and code short-curcuits it to S.
1168 * L|S is logically invalid, it would mean -1 packet in flight 8))
1169 *
1170 * These 6 states form finite state machine, controlled by the following events:
1171 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1172 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1173 * 3. Loss detection event of two flavors:
1174 * A. Scoreboard estimator decided the packet is lost.
1175 * A'. Reno "three dupacks" marks head of queue lost.
1176 * B. SACK arrives sacking SND.NXT at the moment, when the
1177 * segment was retransmitted.
1178 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1179 *
1180 * It is pleasant to note, that state diagram turns out to be commutative,
1181 * so that we are allowed not to be bothered by order of our actions,
1182 * when multiple events arrive simultaneously. (see the function below).
1183 *
1184 * Reordering detection.
1185 * --------------------
1186 * Reordering metric is maximal distance, which a packet can be displaced
1187 * in packet stream. With SACKs we can estimate it:
1188 *
1189 * 1. SACK fills old hole and the corresponding segment was not
1190 * ever retransmitted -> reordering. Alas, we cannot use it
1191 * when segment was retransmitted.
1192 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1193 * for retransmitted and already SACKed segment -> reordering..
1194 * Both of these heuristics are not used in Loss state, when we cannot
1195 * account for retransmits accurately.
1196 *
1197 * SACK block validation.
1198 * ----------------------
1199 *
1200 * SACK block range validation checks that the received SACK block fits to
1201 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1202 * Note that SND.UNA is not included to the range though being valid because
1203 * it means that the receiver is rather inconsistent with itself reporting
1204 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1205 * perfectly valid, however, in light of RFC2018 which explicitly states
1206 * that "SACK block MUST reflect the newest segment. Even if the newest
1207 * segment is going to be discarded ...", not that it looks very clever
1208 * in case of head skb. Due to potentional receiver driven attacks, we
1209 * choose to avoid immediate execution of a walk in write queue due to
1210 * reneging and defer head skb's loss recovery to standard loss recovery
1211 * procedure that will eventually trigger (nothing forbids us doing this).
1212 *
1213 * Implements also blockage to start_seq wrap-around. Problem lies in the
1214 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1215 * there's no guarantee that it will be before snd_nxt (n). The problem
1216 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1217 * wrap (s_w):
1218 *
1219 * <- outs wnd -> <- wrapzone ->
1220 * u e n u_w e_w s n_w
1221 * | | | | | | |
1222 * |<------------+------+----- TCP seqno space --------------+---------->|
1223 * ...-- <2^31 ->| |<--------...
1224 * ...---- >2^31 ------>| |<--------...
1225 *
1226 * Current code wouldn't be vulnerable but it's better still to discard such
1227 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1228 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1229 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1230 * equal to the ideal case (infinite seqno space without wrap caused issues).
1231 *
1232 * With D-SACK the lower bound is extended to cover sequence space below
1233 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1234 * again, D-SACK block must not to go across snd_una (for the same reason as
1235 * for the normal SACK blocks, explained above). But there all simplicity
1236 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1237 * fully below undo_marker they do not affect behavior in anyway and can
1238 * therefore be safely ignored. In rare cases (which are more or less
1239 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1240 * fragmentation and packet reordering past skb's retransmission. To consider
1241 * them correctly, the acceptable range must be extended even more though
1242 * the exact amount is rather hard to quantify. However, tp->max_window can
1243 * be used as an exaggerated estimate.
1244 */
1245static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack,
1246 u32 start_seq, u32 end_seq)
1247{
1248 /* Too far in future, or reversed (interpretation is ambiguous) */
1249 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
1250 return false;
1251
1252 /* Nasty start_seq wrap-around check (see comments above) */
1253 if (!before(start_seq, tp->snd_nxt))
1254 return false;
1255
1256 /* In outstanding window? ...This is valid exit for D-SACKs too.
1257 * start_seq == snd_una is non-sensical (see comments above)
1258 */
1259 if (after(start_seq, tp->snd_una))
1260 return true;
1261
1262 if (!is_dsack || !tp->undo_marker)
1263 return false;
1264
1265 /* ...Then it's D-SACK, and must reside below snd_una completely */
1266 if (after(end_seq, tp->snd_una))
1267 return false;
1268
1269 if (!before(start_seq, tp->undo_marker))
1270 return true;
1271
1272 /* Too old */
1273 if (!after(end_seq, tp->undo_marker))
1274 return false;
1275
1276 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1277 * start_seq < undo_marker and end_seq >= undo_marker.
1278 */
1279 return !before(start_seq, end_seq - tp->max_window);
1280}
1281
1282static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
1283 struct tcp_sack_block_wire *sp, int num_sacks,
1284 u32 prior_snd_una, struct tcp_sacktag_state *state)
1285{
1286 struct tcp_sock *tp = tcp_sk(sk);
1287 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
1288 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
1289 u32 dup_segs;
1290
1291 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
1292 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKRECV);
1293 } else if (num_sacks > 1) {
1294 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
1295 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
1296
1297 if (after(end_seq_0, end_seq_1) || before(start_seq_0, start_seq_1))
1298 return false;
1299 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKOFORECV);
1300 } else {
1301 return false;
1302 }
1303
1304 dup_segs = tcp_dsack_seen(tp, start_seq_0, end_seq_0, state);
1305 if (!dup_segs) { /* Skip dubious DSACK */
1306 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKIGNOREDDUBIOUS);
1307 return false;
1308 }
1309
1310 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPDSACKRECVSEGS, dup_segs);
1311
1312 /* D-SACK for already forgotten data... Do dumb counting. */
1313 if (tp->undo_marker && tp->undo_retrans > 0 &&
1314 !after(end_seq_0, prior_snd_una) &&
1315 after(end_seq_0, tp->undo_marker))
1316 tp->undo_retrans = max_t(int, 0, tp->undo_retrans - dup_segs);
1317
1318 return true;
1319}
1320
1321/* Check if skb is fully within the SACK block. In presence of GSO skbs,
1322 * the incoming SACK may not exactly match but we can find smaller MSS
1323 * aligned portion of it that matches. Therefore we might need to fragment
1324 * which may fail and creates some hassle (caller must handle error case
1325 * returns).
1326 *
1327 * FIXME: this could be merged to shift decision code
1328 */
1329static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
1330 u32 start_seq, u32 end_seq)
1331{
1332 int err;
1333 bool in_sack;
1334 unsigned int pkt_len;
1335 unsigned int mss;
1336
1337 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1338 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1339
1340 if (tcp_skb_pcount(skb) > 1 && !in_sack &&
1341 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1342 mss = tcp_skb_mss(skb);
1343 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1344
1345 if (!in_sack) {
1346 pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
1347 if (pkt_len < mss)
1348 pkt_len = mss;
1349 } else {
1350 pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
1351 if (pkt_len < mss)
1352 return -EINVAL;
1353 }
1354
1355 /* Round if necessary so that SACKs cover only full MSSes
1356 * and/or the remaining small portion (if present)
1357 */
1358 if (pkt_len > mss) {
1359 unsigned int new_len = (pkt_len / mss) * mss;
1360 if (!in_sack && new_len < pkt_len)
1361 new_len += mss;
1362 pkt_len = new_len;
1363 }
1364
1365 if (pkt_len >= skb->len && !in_sack)
1366 return 0;
1367
1368 err = tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
1369 pkt_len, mss, GFP_ATOMIC);
1370 if (err < 0)
1371 return err;
1372 }
1373
1374 return in_sack;
1375}
1376
1377/* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1378static u8 tcp_sacktag_one(struct sock *sk,
1379 struct tcp_sacktag_state *state, u8 sacked,
1380 u32 start_seq, u32 end_seq,
1381 int dup_sack, int pcount,
1382 u64 xmit_time)
1383{
1384 struct tcp_sock *tp = tcp_sk(sk);
1385
1386 /* Account D-SACK for retransmitted packet. */
1387 if (dup_sack && (sacked & TCPCB_RETRANS)) {
1388 if (tp->undo_marker && tp->undo_retrans > 0 &&
1389 after(end_seq, tp->undo_marker))
1390 tp->undo_retrans = max_t(int, 0, tp->undo_retrans - pcount);
1391 if ((sacked & TCPCB_SACKED_ACKED) &&
1392 before(start_seq, state->reord))
1393 state->reord = start_seq;
1394 }
1395
1396 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1397 if (!after(end_seq, tp->snd_una))
1398 return sacked;
1399
1400 if (!(sacked & TCPCB_SACKED_ACKED)) {
1401 tcp_rack_advance(tp, sacked, end_seq, xmit_time);
1402
1403 if (sacked & TCPCB_SACKED_RETRANS) {
1404 /* If the segment is not tagged as lost,
1405 * we do not clear RETRANS, believing
1406 * that retransmission is still in flight.
1407 */
1408 if (sacked & TCPCB_LOST) {
1409 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1410 tp->lost_out -= pcount;
1411 tp->retrans_out -= pcount;
1412 }
1413 } else {
1414 if (!(sacked & TCPCB_RETRANS)) {
1415 /* New sack for not retransmitted frame,
1416 * which was in hole. It is reordering.
1417 */
1418 if (before(start_seq,
1419 tcp_highest_sack_seq(tp)) &&
1420 before(start_seq, state->reord))
1421 state->reord = start_seq;
1422
1423 if (!after(end_seq, tp->high_seq))
1424 state->flag |= FLAG_ORIG_SACK_ACKED;
1425 if (state->first_sackt == 0)
1426 state->first_sackt = xmit_time;
1427 state->last_sackt = xmit_time;
1428 }
1429
1430 if (sacked & TCPCB_LOST) {
1431 sacked &= ~TCPCB_LOST;
1432 tp->lost_out -= pcount;
1433 }
1434 }
1435
1436 sacked |= TCPCB_SACKED_ACKED;
1437 state->flag |= FLAG_DATA_SACKED;
1438 tp->sacked_out += pcount;
1439 /* Out-of-order packets delivered */
1440 state->sack_delivered += pcount;
1441
1442 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1443 if (tp->lost_skb_hint &&
1444 before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq))
1445 tp->lost_cnt_hint += pcount;
1446 }
1447
1448 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1449 * frames and clear it. undo_retrans is decreased above, L|R frames
1450 * are accounted above as well.
1451 */
1452 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
1453 sacked &= ~TCPCB_SACKED_RETRANS;
1454 tp->retrans_out -= pcount;
1455 }
1456
1457 return sacked;
1458}
1459
1460/* Shift newly-SACKed bytes from this skb to the immediately previous
1461 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1462 */
1463static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *prev,
1464 struct sk_buff *skb,
1465 struct tcp_sacktag_state *state,
1466 unsigned int pcount, int shifted, int mss,
1467 bool dup_sack)
1468{
1469 struct tcp_sock *tp = tcp_sk(sk);
1470 u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */
1471 u32 end_seq = start_seq + shifted; /* end of newly-SACKed */
1472
1473 BUG_ON(!pcount);
1474
1475 /* Adjust counters and hints for the newly sacked sequence
1476 * range but discard the return value since prev is already
1477 * marked. We must tag the range first because the seq
1478 * advancement below implicitly advances
1479 * tcp_highest_sack_seq() when skb is highest_sack.
1480 */
1481 tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
1482 start_seq, end_seq, dup_sack, pcount,
1483 tcp_skb_timestamp_us(skb));
1484 tcp_rate_skb_delivered(sk, skb, state->rate);
1485
1486 if (skb == tp->lost_skb_hint)
1487 tp->lost_cnt_hint += pcount;
1488
1489 TCP_SKB_CB(prev)->end_seq += shifted;
1490 TCP_SKB_CB(skb)->seq += shifted;
1491
1492 tcp_skb_pcount_add(prev, pcount);
1493 WARN_ON_ONCE(tcp_skb_pcount(skb) < pcount);
1494 tcp_skb_pcount_add(skb, -pcount);
1495
1496 /* When we're adding to gso_segs == 1, gso_size will be zero,
1497 * in theory this shouldn't be necessary but as long as DSACK
1498 * code can come after this skb later on it's better to keep
1499 * setting gso_size to something.
1500 */
1501 if (!TCP_SKB_CB(prev)->tcp_gso_size)
1502 TCP_SKB_CB(prev)->tcp_gso_size = mss;
1503
1504 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1505 if (tcp_skb_pcount(skb) <= 1)
1506 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1507
1508 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1509 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
1510
1511 if (skb->len > 0) {
1512 BUG_ON(!tcp_skb_pcount(skb));
1513 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTED);
1514 return false;
1515 }
1516
1517 /* Whole SKB was eaten :-) */
1518
1519 if (skb == tp->retransmit_skb_hint)
1520 tp->retransmit_skb_hint = prev;
1521 if (skb == tp->lost_skb_hint) {
1522 tp->lost_skb_hint = prev;
1523 tp->lost_cnt_hint -= tcp_skb_pcount(prev);
1524 }
1525
1526 TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1527 TCP_SKB_CB(prev)->eor = TCP_SKB_CB(skb)->eor;
1528 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1529 TCP_SKB_CB(prev)->end_seq++;
1530
1531 if (skb == tcp_highest_sack(sk))
1532 tcp_advance_highest_sack(sk, skb);
1533
1534 tcp_skb_collapse_tstamp(prev, skb);
1535 if (unlikely(TCP_SKB_CB(prev)->tx.delivered_mstamp))
1536 TCP_SKB_CB(prev)->tx.delivered_mstamp = 0;
1537
1538 tcp_rtx_queue_unlink_and_free(skb, sk);
1539
1540 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKMERGED);
1541
1542 return true;
1543}
1544
1545/* I wish gso_size would have a bit more sane initialization than
1546 * something-or-zero which complicates things
1547 */
1548static int tcp_skb_seglen(const struct sk_buff *skb)
1549{
1550 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
1551}
1552
1553/* Shifting pages past head area doesn't work */
1554static int skb_can_shift(const struct sk_buff *skb)
1555{
1556 return !skb_headlen(skb) && skb_is_nonlinear(skb);
1557}
1558
1559int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from,
1560 int pcount, int shiftlen)
1561{
1562 /* TCP min gso_size is 8 bytes (TCP_MIN_GSO_SIZE)
1563 * Since TCP_SKB_CB(skb)->tcp_gso_segs is 16 bits, we need
1564 * to make sure not storing more than 65535 * 8 bytes per skb,
1565 * even if current MSS is bigger.
1566 */
1567 if (unlikely(to->len + shiftlen >= 65535 * TCP_MIN_GSO_SIZE))
1568 return 0;
1569 if (unlikely(tcp_skb_pcount(to) + pcount > 65535))
1570 return 0;
1571 return skb_shift(to, from, shiftlen);
1572}
1573
1574/* Try collapsing SACK blocks spanning across multiple skbs to a single
1575 * skb.
1576 */
1577static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
1578 struct tcp_sacktag_state *state,
1579 u32 start_seq, u32 end_seq,
1580 bool dup_sack)
1581{
1582 struct tcp_sock *tp = tcp_sk(sk);
1583 struct sk_buff *prev;
1584 int mss;
1585 int pcount = 0;
1586 int len;
1587 int in_sack;
1588
1589 /* Normally R but no L won't result in plain S */
1590 if (!dup_sack &&
1591 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
1592 goto fallback;
1593 if (!skb_can_shift(skb))
1594 goto fallback;
1595 /* This frame is about to be dropped (was ACKed). */
1596 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1597 goto fallback;
1598
1599 /* Can only happen with delayed DSACK + discard craziness */
1600 prev = skb_rb_prev(skb);
1601 if (!prev)
1602 goto fallback;
1603
1604 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
1605 goto fallback;
1606
1607 if (!tcp_skb_can_collapse(prev, skb))
1608 goto fallback;
1609
1610 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1611 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1612
1613 if (in_sack) {
1614 len = skb->len;
1615 pcount = tcp_skb_pcount(skb);
1616 mss = tcp_skb_seglen(skb);
1617
1618 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1619 * drop this restriction as unnecessary
1620 */
1621 if (mss != tcp_skb_seglen(prev))
1622 goto fallback;
1623 } else {
1624 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
1625 goto noop;
1626 /* CHECKME: This is non-MSS split case only?, this will
1627 * cause skipped skbs due to advancing loop btw, original
1628 * has that feature too
1629 */
1630 if (tcp_skb_pcount(skb) <= 1)
1631 goto noop;
1632
1633 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1634 if (!in_sack) {
1635 /* TODO: head merge to next could be attempted here
1636 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1637 * though it might not be worth of the additional hassle
1638 *
1639 * ...we can probably just fallback to what was done
1640 * previously. We could try merging non-SACKed ones
1641 * as well but it probably isn't going to buy off
1642 * because later SACKs might again split them, and
1643 * it would make skb timestamp tracking considerably
1644 * harder problem.
1645 */
1646 goto fallback;
1647 }
1648
1649 len = end_seq - TCP_SKB_CB(skb)->seq;
1650 BUG_ON(len < 0);
1651 BUG_ON(len > skb->len);
1652
1653 /* MSS boundaries should be honoured or else pcount will
1654 * severely break even though it makes things bit trickier.
1655 * Optimize common case to avoid most of the divides
1656 */
1657 mss = tcp_skb_mss(skb);
1658
1659 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1660 * drop this restriction as unnecessary
1661 */
1662 if (mss != tcp_skb_seglen(prev))
1663 goto fallback;
1664
1665 if (len == mss) {
1666 pcount = 1;
1667 } else if (len < mss) {
1668 goto noop;
1669 } else {
1670 pcount = len / mss;
1671 len = pcount * mss;
1672 }
1673 }
1674
1675 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1676 if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una))
1677 goto fallback;
1678
1679 if (!tcp_skb_shift(prev, skb, pcount, len))
1680 goto fallback;
1681 if (!tcp_shifted_skb(sk, prev, skb, state, pcount, len, mss, dup_sack))
1682 goto out;
1683
1684 /* Hole filled allows collapsing with the next as well, this is very
1685 * useful when hole on every nth skb pattern happens
1686 */
1687 skb = skb_rb_next(prev);
1688 if (!skb)
1689 goto out;
1690
1691 if (!skb_can_shift(skb) ||
1692 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
1693 (mss != tcp_skb_seglen(skb)))
1694 goto out;
1695
1696 if (!tcp_skb_can_collapse(prev, skb))
1697 goto out;
1698 len = skb->len;
1699 pcount = tcp_skb_pcount(skb);
1700 if (tcp_skb_shift(prev, skb, pcount, len))
1701 tcp_shifted_skb(sk, prev, skb, state, pcount,
1702 len, mss, 0);
1703
1704out:
1705 return prev;
1706
1707noop:
1708 return skb;
1709
1710fallback:
1711 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
1712 return NULL;
1713}
1714
1715static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
1716 struct tcp_sack_block *next_dup,
1717 struct tcp_sacktag_state *state,
1718 u32 start_seq, u32 end_seq,
1719 bool dup_sack_in)
1720{
1721 struct tcp_sock *tp = tcp_sk(sk);
1722 struct sk_buff *tmp;
1723
1724 skb_rbtree_walk_from(skb) {
1725 int in_sack = 0;
1726 bool dup_sack = dup_sack_in;
1727
1728 /* queue is in-order => we can short-circuit the walk early */
1729 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1730 break;
1731
1732 if (next_dup &&
1733 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
1734 in_sack = tcp_match_skb_to_sack(sk, skb,
1735 next_dup->start_seq,
1736 next_dup->end_seq);
1737 if (in_sack > 0)
1738 dup_sack = true;
1739 }
1740
1741 /* skb reference here is a bit tricky to get right, since
1742 * shifting can eat and free both this skb and the next,
1743 * so not even _safe variant of the loop is enough.
1744 */
1745 if (in_sack <= 0) {
1746 tmp = tcp_shift_skb_data(sk, skb, state,
1747 start_seq, end_seq, dup_sack);
1748 if (tmp) {
1749 if (tmp != skb) {
1750 skb = tmp;
1751 continue;
1752 }
1753
1754 in_sack = 0;
1755 } else {
1756 in_sack = tcp_match_skb_to_sack(sk, skb,
1757 start_seq,
1758 end_seq);
1759 }
1760 }
1761
1762 if (unlikely(in_sack < 0))
1763 break;
1764
1765 if (in_sack) {
1766 TCP_SKB_CB(skb)->sacked =
1767 tcp_sacktag_one(sk,
1768 state,
1769 TCP_SKB_CB(skb)->sacked,
1770 TCP_SKB_CB(skb)->seq,
1771 TCP_SKB_CB(skb)->end_seq,
1772 dup_sack,
1773 tcp_skb_pcount(skb),
1774 tcp_skb_timestamp_us(skb));
1775 tcp_rate_skb_delivered(sk, skb, state->rate);
1776 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1777 list_del_init(&skb->tcp_tsorted_anchor);
1778
1779 if (!before(TCP_SKB_CB(skb)->seq,
1780 tcp_highest_sack_seq(tp)))
1781 tcp_advance_highest_sack(sk, skb);
1782 }
1783 }
1784 return skb;
1785}
1786
1787static struct sk_buff *tcp_sacktag_bsearch(struct sock *sk, u32 seq)
1788{
1789 struct rb_node *parent, **p = &sk->tcp_rtx_queue.rb_node;
1790 struct sk_buff *skb;
1791
1792 while (*p) {
1793 parent = *p;
1794 skb = rb_to_skb(parent);
1795 if (before(seq, TCP_SKB_CB(skb)->seq)) {
1796 p = &parent->rb_left;
1797 continue;
1798 }
1799 if (!before(seq, TCP_SKB_CB(skb)->end_seq)) {
1800 p = &parent->rb_right;
1801 continue;
1802 }
1803 return skb;
1804 }
1805 return NULL;
1806}
1807
1808static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
1809 u32 skip_to_seq)
1810{
1811 if (skb && after(TCP_SKB_CB(skb)->seq, skip_to_seq))
1812 return skb;
1813
1814 return tcp_sacktag_bsearch(sk, skip_to_seq);
1815}
1816
1817static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
1818 struct sock *sk,
1819 struct tcp_sack_block *next_dup,
1820 struct tcp_sacktag_state *state,
1821 u32 skip_to_seq)
1822{
1823 if (!next_dup)
1824 return skb;
1825
1826 if (before(next_dup->start_seq, skip_to_seq)) {
1827 skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq);
1828 skb = tcp_sacktag_walk(skb, sk, NULL, state,
1829 next_dup->start_seq, next_dup->end_seq,
1830 1);
1831 }
1832
1833 return skb;
1834}
1835
1836static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache)
1837{
1838 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1839}
1840
1841static int
1842tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
1843 u32 prior_snd_una, struct tcp_sacktag_state *state)
1844{
1845 struct tcp_sock *tp = tcp_sk(sk);
1846 const unsigned char *ptr = (skb_transport_header(ack_skb) +
1847 TCP_SKB_CB(ack_skb)->sacked);
1848 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
1849 struct tcp_sack_block sp[TCP_NUM_SACKS];
1850 struct tcp_sack_block *cache;
1851 struct sk_buff *skb;
1852 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
1853 int used_sacks;
1854 bool found_dup_sack = false;
1855 int i, j;
1856 int first_sack_index;
1857
1858 state->flag = 0;
1859 state->reord = tp->snd_nxt;
1860
1861 if (!tp->sacked_out)
1862 tcp_highest_sack_reset(sk);
1863
1864 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
1865 num_sacks, prior_snd_una, state);
1866
1867 /* Eliminate too old ACKs, but take into
1868 * account more or less fresh ones, they can
1869 * contain valid SACK info.
1870 */
1871 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
1872 return 0;
1873
1874 if (!tp->packets_out)
1875 goto out;
1876
1877 used_sacks = 0;
1878 first_sack_index = 0;
1879 for (i = 0; i < num_sacks; i++) {
1880 bool dup_sack = !i && found_dup_sack;
1881
1882 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
1883 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
1884
1885 if (!tcp_is_sackblock_valid(tp, dup_sack,
1886 sp[used_sacks].start_seq,
1887 sp[used_sacks].end_seq)) {
1888 int mib_idx;
1889
1890 if (dup_sack) {
1891 if (!tp->undo_marker)
1892 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO;
1893 else
1894 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD;
1895 } else {
1896 /* Don't count olds caused by ACK reordering */
1897 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
1898 !after(sp[used_sacks].end_seq, tp->snd_una))
1899 continue;
1900 mib_idx = LINUX_MIB_TCPSACKDISCARD;
1901 }
1902
1903 NET_INC_STATS(sock_net(sk), mib_idx);
1904 if (i == 0)
1905 first_sack_index = -1;
1906 continue;
1907 }
1908
1909 /* Ignore very old stuff early */
1910 if (!after(sp[used_sacks].end_seq, prior_snd_una)) {
1911 if (i == 0)
1912 first_sack_index = -1;
1913 continue;
1914 }
1915
1916 used_sacks++;
1917 }
1918
1919 /* order SACK blocks to allow in order walk of the retrans queue */
1920 for (i = used_sacks - 1; i > 0; i--) {
1921 for (j = 0; j < i; j++) {
1922 if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
1923 swap(sp[j], sp[j + 1]);
1924
1925 /* Track where the first SACK block goes to */
1926 if (j == first_sack_index)
1927 first_sack_index = j + 1;
1928 }
1929 }
1930 }
1931
1932 state->mss_now = tcp_current_mss(sk);
1933 skb = NULL;
1934 i = 0;
1935
1936 if (!tp->sacked_out) {
1937 /* It's already past, so skip checking against it */
1938 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1939 } else {
1940 cache = tp->recv_sack_cache;
1941 /* Skip empty blocks in at head of the cache */
1942 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
1943 !cache->end_seq)
1944 cache++;
1945 }
1946
1947 while (i < used_sacks) {
1948 u32 start_seq = sp[i].start_seq;
1949 u32 end_seq = sp[i].end_seq;
1950 bool dup_sack = (found_dup_sack && (i == first_sack_index));
1951 struct tcp_sack_block *next_dup = NULL;
1952
1953 if (found_dup_sack && ((i + 1) == first_sack_index))
1954 next_dup = &sp[i + 1];
1955
1956 /* Skip too early cached blocks */
1957 while (tcp_sack_cache_ok(tp, cache) &&
1958 !before(start_seq, cache->end_seq))
1959 cache++;
1960
1961 /* Can skip some work by looking recv_sack_cache? */
1962 if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
1963 after(end_seq, cache->start_seq)) {
1964
1965 /* Head todo? */
1966 if (before(start_seq, cache->start_seq)) {
1967 skb = tcp_sacktag_skip(skb, sk, start_seq);
1968 skb = tcp_sacktag_walk(skb, sk, next_dup,
1969 state,
1970 start_seq,
1971 cache->start_seq,
1972 dup_sack);
1973 }
1974
1975 /* Rest of the block already fully processed? */
1976 if (!after(end_seq, cache->end_seq))
1977 goto advance_sp;
1978
1979 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
1980 state,
1981 cache->end_seq);
1982
1983 /* ...tail remains todo... */
1984 if (tcp_highest_sack_seq(tp) == cache->end_seq) {
1985 /* ...but better entrypoint exists! */
1986 skb = tcp_highest_sack(sk);
1987 if (!skb)
1988 break;
1989 cache++;
1990 goto walk;
1991 }
1992
1993 skb = tcp_sacktag_skip(skb, sk, cache->end_seq);
1994 /* Check overlap against next cached too (past this one already) */
1995 cache++;
1996 continue;
1997 }
1998
1999 if (!before(start_seq, tcp_highest_sack_seq(tp))) {
2000 skb = tcp_highest_sack(sk);
2001 if (!skb)
2002 break;
2003 }
2004 skb = tcp_sacktag_skip(skb, sk, start_seq);
2005
2006walk:
2007 skb = tcp_sacktag_walk(skb, sk, next_dup, state,
2008 start_seq, end_seq, dup_sack);
2009
2010advance_sp:
2011 i++;
2012 }
2013
2014 /* Clear the head of the cache sack blocks so we can skip it next time */
2015 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
2016 tp->recv_sack_cache[i].start_seq = 0;
2017 tp->recv_sack_cache[i].end_seq = 0;
2018 }
2019 for (j = 0; j < used_sacks; j++)
2020 tp->recv_sack_cache[i++] = sp[j];
2021
2022 if (inet_csk(sk)->icsk_ca_state != TCP_CA_Loss || tp->undo_marker)
2023 tcp_check_sack_reordering(sk, state->reord, 0);
2024
2025 tcp_verify_left_out(tp);
2026out:
2027
2028#if FASTRETRANS_DEBUG > 0
2029 WARN_ON((int)tp->sacked_out < 0);
2030 WARN_ON((int)tp->lost_out < 0);
2031 WARN_ON((int)tp->retrans_out < 0);
2032 WARN_ON((int)tcp_packets_in_flight(tp) < 0);
2033#endif
2034 return state->flag;
2035}
2036
2037/* Limits sacked_out so that sum with lost_out isn't ever larger than
2038 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
2039 */
2040static bool tcp_limit_reno_sacked(struct tcp_sock *tp)
2041{
2042 u32 holes;
2043
2044 holes = max(tp->lost_out, 1U);
2045 holes = min(holes, tp->packets_out);
2046
2047 if ((tp->sacked_out + holes) > tp->packets_out) {
2048 tp->sacked_out = tp->packets_out - holes;
2049 return true;
2050 }
2051 return false;
2052}
2053
2054/* If we receive more dupacks than we expected counting segments
2055 * in assumption of absent reordering, interpret this as reordering.
2056 * The only another reason could be bug in receiver TCP.
2057 */
2058static void tcp_check_reno_reordering(struct sock *sk, const int addend)
2059{
2060 struct tcp_sock *tp = tcp_sk(sk);
2061
2062 if (!tcp_limit_reno_sacked(tp))
2063 return;
2064
2065 tp->reordering = min_t(u32, tp->packets_out + addend,
2066 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering));
2067 tp->reord_seen++;
2068 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRENOREORDER);
2069}
2070
2071/* Emulate SACKs for SACKless connection: account for a new dupack. */
2072
2073static void tcp_add_reno_sack(struct sock *sk, int num_dupack, bool ece_ack)
2074{
2075 if (num_dupack) {
2076 struct tcp_sock *tp = tcp_sk(sk);
2077 u32 prior_sacked = tp->sacked_out;
2078 s32 delivered;
2079
2080 tp->sacked_out += num_dupack;
2081 tcp_check_reno_reordering(sk, 0);
2082 delivered = tp->sacked_out - prior_sacked;
2083 if (delivered > 0)
2084 tcp_count_delivered(tp, delivered, ece_ack);
2085 tcp_verify_left_out(tp);
2086 }
2087}
2088
2089/* Account for ACK, ACKing some data in Reno Recovery phase. */
2090
2091static void tcp_remove_reno_sacks(struct sock *sk, int acked, bool ece_ack)
2092{
2093 struct tcp_sock *tp = tcp_sk(sk);
2094
2095 if (acked > 0) {
2096 /* One ACK acked hole. The rest eat duplicate ACKs. */
2097 tcp_count_delivered(tp, max_t(int, acked - tp->sacked_out, 1),
2098 ece_ack);
2099 if (acked - 1 >= tp->sacked_out)
2100 tp->sacked_out = 0;
2101 else
2102 tp->sacked_out -= acked - 1;
2103 }
2104 tcp_check_reno_reordering(sk, acked);
2105 tcp_verify_left_out(tp);
2106}
2107
2108static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
2109{
2110 tp->sacked_out = 0;
2111}
2112
2113void tcp_clear_retrans(struct tcp_sock *tp)
2114{
2115 tp->retrans_out = 0;
2116 tp->lost_out = 0;
2117 tp->undo_marker = 0;
2118 tp->undo_retrans = -1;
2119 tp->sacked_out = 0;
2120 tp->rto_stamp = 0;
2121 tp->total_rto = 0;
2122 tp->total_rto_recoveries = 0;
2123 tp->total_rto_time = 0;
2124}
2125
2126static inline void tcp_init_undo(struct tcp_sock *tp)
2127{
2128 tp->undo_marker = tp->snd_una;
2129 /* Retransmission still in flight may cause DSACKs later. */
2130 tp->undo_retrans = tp->retrans_out ? : -1;
2131}
2132
2133static bool tcp_is_rack(const struct sock *sk)
2134{
2135 return READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
2136 TCP_RACK_LOSS_DETECTION;
2137}
2138
2139/* If we detect SACK reneging, forget all SACK information
2140 * and reset tags completely, otherwise preserve SACKs. If receiver
2141 * dropped its ofo queue, we will know this due to reneging detection.
2142 */
2143static void tcp_timeout_mark_lost(struct sock *sk)
2144{
2145 struct tcp_sock *tp = tcp_sk(sk);
2146 struct sk_buff *skb, *head;
2147 bool is_reneg; /* is receiver reneging on SACKs? */
2148
2149 head = tcp_rtx_queue_head(sk);
2150 is_reneg = head && (TCP_SKB_CB(head)->sacked & TCPCB_SACKED_ACKED);
2151 if (is_reneg) {
2152 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
2153 tp->sacked_out = 0;
2154 /* Mark SACK reneging until we recover from this loss event. */
2155 tp->is_sack_reneg = 1;
2156 } else if (tcp_is_reno(tp)) {
2157 tcp_reset_reno_sack(tp);
2158 }
2159
2160 skb = head;
2161 skb_rbtree_walk_from(skb) {
2162 if (is_reneg)
2163 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
2164 else if (tcp_is_rack(sk) && skb != head &&
2165 tcp_rack_skb_timeout(tp, skb, 0) > 0)
2166 continue; /* Don't mark recently sent ones lost yet */
2167 tcp_mark_skb_lost(sk, skb);
2168 }
2169 tcp_verify_left_out(tp);
2170 tcp_clear_all_retrans_hints(tp);
2171}
2172
2173/* Enter Loss state. */
2174void tcp_enter_loss(struct sock *sk)
2175{
2176 const struct inet_connection_sock *icsk = inet_csk(sk);
2177 struct tcp_sock *tp = tcp_sk(sk);
2178 struct net *net = sock_net(sk);
2179 bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery;
2180 u8 reordering;
2181
2182 tcp_timeout_mark_lost(sk);
2183
2184 /* Reduce ssthresh if it has not yet been made inside this window. */
2185 if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
2186 !after(tp->high_seq, tp->snd_una) ||
2187 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
2188 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2189 tp->prior_cwnd = tcp_snd_cwnd(tp);
2190 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2191 tcp_ca_event(sk, CA_EVENT_LOSS);
2192 tcp_init_undo(tp);
2193 }
2194 tcp_snd_cwnd_set(tp, tcp_packets_in_flight(tp) + 1);
2195 tp->snd_cwnd_cnt = 0;
2196 tp->snd_cwnd_stamp = tcp_jiffies32;
2197
2198 /* Timeout in disordered state after receiving substantial DUPACKs
2199 * suggests that the degree of reordering is over-estimated.
2200 */
2201 reordering = READ_ONCE(net->ipv4.sysctl_tcp_reordering);
2202 if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
2203 tp->sacked_out >= reordering)
2204 tp->reordering = min_t(unsigned int, tp->reordering,
2205 reordering);
2206
2207 tcp_set_ca_state(sk, TCP_CA_Loss);
2208 tp->high_seq = tp->snd_nxt;
2209 tcp_ecn_queue_cwr(tp);
2210
2211 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
2212 * loss recovery is underway except recurring timeout(s) on
2213 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
2214 */
2215 tp->frto = READ_ONCE(net->ipv4.sysctl_tcp_frto) &&
2216 (new_recovery || icsk->icsk_retransmits) &&
2217 !inet_csk(sk)->icsk_mtup.probe_size;
2218}
2219
2220/* If ACK arrived pointing to a remembered SACK, it means that our
2221 * remembered SACKs do not reflect real state of receiver i.e.
2222 * receiver _host_ is heavily congested (or buggy).
2223 *
2224 * To avoid big spurious retransmission bursts due to transient SACK
2225 * scoreboard oddities that look like reneging, we give the receiver a
2226 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
2227 * restore sanity to the SACK scoreboard. If the apparent reneging
2228 * persists until this RTO then we'll clear the SACK scoreboard.
2229 */
2230static bool tcp_check_sack_reneging(struct sock *sk, int *ack_flag)
2231{
2232 if (*ack_flag & FLAG_SACK_RENEGING &&
2233 *ack_flag & FLAG_SND_UNA_ADVANCED) {
2234 struct tcp_sock *tp = tcp_sk(sk);
2235 unsigned long delay = max(usecs_to_jiffies(tp->srtt_us >> 4),
2236 msecs_to_jiffies(10));
2237
2238 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2239 delay, TCP_RTO_MAX);
2240 *ack_flag &= ~FLAG_SET_XMIT_TIMER;
2241 return true;
2242 }
2243 return false;
2244}
2245
2246/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2247 * counter when SACK is enabled (without SACK, sacked_out is used for
2248 * that purpose).
2249 *
2250 * With reordering, holes may still be in flight, so RFC3517 recovery
2251 * uses pure sacked_out (total number of SACKed segments) even though
2252 * it violates the RFC that uses duplicate ACKs, often these are equal
2253 * but when e.g. out-of-window ACKs or packet duplication occurs,
2254 * they differ. Since neither occurs due to loss, TCP should really
2255 * ignore them.
2256 */
2257static inline int tcp_dupack_heuristics(const struct tcp_sock *tp)
2258{
2259 return tp->sacked_out + 1;
2260}
2261
2262/* Linux NewReno/SACK/ECN state machine.
2263 * --------------------------------------
2264 *
2265 * "Open" Normal state, no dubious events, fast path.
2266 * "Disorder" In all the respects it is "Open",
2267 * but requires a bit more attention. It is entered when
2268 * we see some SACKs or dupacks. It is split of "Open"
2269 * mainly to move some processing from fast path to slow one.
2270 * "CWR" CWND was reduced due to some Congestion Notification event.
2271 * It can be ECN, ICMP source quench, local device congestion.
2272 * "Recovery" CWND was reduced, we are fast-retransmitting.
2273 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2274 *
2275 * tcp_fastretrans_alert() is entered:
2276 * - each incoming ACK, if state is not "Open"
2277 * - when arrived ACK is unusual, namely:
2278 * * SACK
2279 * * Duplicate ACK.
2280 * * ECN ECE.
2281 *
2282 * Counting packets in flight is pretty simple.
2283 *
2284 * in_flight = packets_out - left_out + retrans_out
2285 *
2286 * packets_out is SND.NXT-SND.UNA counted in packets.
2287 *
2288 * retrans_out is number of retransmitted segments.
2289 *
2290 * left_out is number of segments left network, but not ACKed yet.
2291 *
2292 * left_out = sacked_out + lost_out
2293 *
2294 * sacked_out: Packets, which arrived to receiver out of order
2295 * and hence not ACKed. With SACKs this number is simply
2296 * amount of SACKed data. Even without SACKs
2297 * it is easy to give pretty reliable estimate of this number,
2298 * counting duplicate ACKs.
2299 *
2300 * lost_out: Packets lost by network. TCP has no explicit
2301 * "loss notification" feedback from network (for now).
2302 * It means that this number can be only _guessed_.
2303 * Actually, it is the heuristics to predict lossage that
2304 * distinguishes different algorithms.
2305 *
2306 * F.e. after RTO, when all the queue is considered as lost,
2307 * lost_out = packets_out and in_flight = retrans_out.
2308 *
2309 * Essentially, we have now a few algorithms detecting
2310 * lost packets.
2311 *
2312 * If the receiver supports SACK:
2313 *
2314 * RFC6675/3517: It is the conventional algorithm. A packet is
2315 * considered lost if the number of higher sequence packets
2316 * SACKed is greater than or equal the DUPACK thoreshold
2317 * (reordering). This is implemented in tcp_mark_head_lost and
2318 * tcp_update_scoreboard.
2319 *
2320 * RACK (draft-ietf-tcpm-rack-01): it is a newer algorithm
2321 * (2017-) that checks timing instead of counting DUPACKs.
2322 * Essentially a packet is considered lost if it's not S/ACKed
2323 * after RTT + reordering_window, where both metrics are
2324 * dynamically measured and adjusted. This is implemented in
2325 * tcp_rack_mark_lost.
2326 *
2327 * If the receiver does not support SACK:
2328 *
2329 * NewReno (RFC6582): in Recovery we assume that one segment
2330 * is lost (classic Reno). While we are in Recovery and
2331 * a partial ACK arrives, we assume that one more packet
2332 * is lost (NewReno). This heuristics are the same in NewReno
2333 * and SACK.
2334 *
2335 * Really tricky (and requiring careful tuning) part of algorithm
2336 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2337 * The first determines the moment _when_ we should reduce CWND and,
2338 * hence, slow down forward transmission. In fact, it determines the moment
2339 * when we decide that hole is caused by loss, rather than by a reorder.
2340 *
2341 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2342 * holes, caused by lost packets.
2343 *
2344 * And the most logically complicated part of algorithm is undo
2345 * heuristics. We detect false retransmits due to both too early
2346 * fast retransmit (reordering) and underestimated RTO, analyzing
2347 * timestamps and D-SACKs. When we detect that some segments were
2348 * retransmitted by mistake and CWND reduction was wrong, we undo
2349 * window reduction and abort recovery phase. This logic is hidden
2350 * inside several functions named tcp_try_undo_<something>.
2351 */
2352
2353/* This function decides, when we should leave Disordered state
2354 * and enter Recovery phase, reducing congestion window.
2355 *
2356 * Main question: may we further continue forward transmission
2357 * with the same cwnd?
2358 */
2359static bool tcp_time_to_recover(struct sock *sk, int flag)
2360{
2361 struct tcp_sock *tp = tcp_sk(sk);
2362
2363 /* Trick#1: The loss is proven. */
2364 if (tp->lost_out)
2365 return true;
2366
2367 /* Not-A-Trick#2 : Classic rule... */
2368 if (!tcp_is_rack(sk) && tcp_dupack_heuristics(tp) > tp->reordering)
2369 return true;
2370
2371 return false;
2372}
2373
2374/* Detect loss in event "A" above by marking head of queue up as lost.
2375 * For RFC3517 SACK, a segment is considered lost if it
2376 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2377 * the maximum SACKed segments to pass before reaching this limit.
2378 */
2379static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
2380{
2381 struct tcp_sock *tp = tcp_sk(sk);
2382 struct sk_buff *skb;
2383 int cnt;
2384 /* Use SACK to deduce losses of new sequences sent during recovery */
2385 const u32 loss_high = tp->snd_nxt;
2386
2387 WARN_ON(packets > tp->packets_out);
2388 skb = tp->lost_skb_hint;
2389 if (skb) {
2390 /* Head already handled? */
2391 if (mark_head && after(TCP_SKB_CB(skb)->seq, tp->snd_una))
2392 return;
2393 cnt = tp->lost_cnt_hint;
2394 } else {
2395 skb = tcp_rtx_queue_head(sk);
2396 cnt = 0;
2397 }
2398
2399 skb_rbtree_walk_from(skb) {
2400 /* TODO: do this better */
2401 /* this is not the most efficient way to do this... */
2402 tp->lost_skb_hint = skb;
2403 tp->lost_cnt_hint = cnt;
2404
2405 if (after(TCP_SKB_CB(skb)->end_seq, loss_high))
2406 break;
2407
2408 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2409 cnt += tcp_skb_pcount(skb);
2410
2411 if (cnt > packets)
2412 break;
2413
2414 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_LOST))
2415 tcp_mark_skb_lost(sk, skb);
2416
2417 if (mark_head)
2418 break;
2419 }
2420 tcp_verify_left_out(tp);
2421}
2422
2423/* Account newly detected lost packet(s) */
2424
2425static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
2426{
2427 struct tcp_sock *tp = tcp_sk(sk);
2428
2429 if (tcp_is_sack(tp)) {
2430 int sacked_upto = tp->sacked_out - tp->reordering;
2431 if (sacked_upto >= 0)
2432 tcp_mark_head_lost(sk, sacked_upto, 0);
2433 else if (fast_rexmit)
2434 tcp_mark_head_lost(sk, 1, 1);
2435 }
2436}
2437
2438static bool tcp_tsopt_ecr_before(const struct tcp_sock *tp, u32 when)
2439{
2440 return tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2441 before(tp->rx_opt.rcv_tsecr, when);
2442}
2443
2444/* skb is spurious retransmitted if the returned timestamp echo
2445 * reply is prior to the skb transmission time
2446 */
2447static bool tcp_skb_spurious_retrans(const struct tcp_sock *tp,
2448 const struct sk_buff *skb)
2449{
2450 return (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) &&
2451 tcp_tsopt_ecr_before(tp, tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb));
2452}
2453
2454/* Nothing was retransmitted or returned timestamp is less
2455 * than timestamp of the first retransmission.
2456 */
2457static inline bool tcp_packet_delayed(const struct tcp_sock *tp)
2458{
2459 return tp->retrans_stamp &&
2460 tcp_tsopt_ecr_before(tp, tp->retrans_stamp);
2461}
2462
2463/* Undo procedures. */
2464
2465/* We can clear retrans_stamp when there are no retransmissions in the
2466 * window. It would seem that it is trivially available for us in
2467 * tp->retrans_out, however, that kind of assumptions doesn't consider
2468 * what will happen if errors occur when sending retransmission for the
2469 * second time. ...It could the that such segment has only
2470 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2471 * the head skb is enough except for some reneging corner cases that
2472 * are not worth the effort.
2473 *
2474 * Main reason for all this complexity is the fact that connection dying
2475 * time now depends on the validity of the retrans_stamp, in particular,
2476 * that successive retransmissions of a segment must not advance
2477 * retrans_stamp under any conditions.
2478 */
2479static bool tcp_any_retrans_done(const struct sock *sk)
2480{
2481 const struct tcp_sock *tp = tcp_sk(sk);
2482 struct sk_buff *skb;
2483
2484 if (tp->retrans_out)
2485 return true;
2486
2487 skb = tcp_rtx_queue_head(sk);
2488 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
2489 return true;
2490
2491 return false;
2492}
2493
2494static void DBGUNDO(struct sock *sk, const char *msg)
2495{
2496#if FASTRETRANS_DEBUG > 1
2497 struct tcp_sock *tp = tcp_sk(sk);
2498 struct inet_sock *inet = inet_sk(sk);
2499
2500 if (sk->sk_family == AF_INET) {
2501 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2502 msg,
2503 &inet->inet_daddr, ntohs(inet->inet_dport),
2504 tcp_snd_cwnd(tp), tcp_left_out(tp),
2505 tp->snd_ssthresh, tp->prior_ssthresh,
2506 tp->packets_out);
2507 }
2508#if IS_ENABLED(CONFIG_IPV6)
2509 else if (sk->sk_family == AF_INET6) {
2510 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2511 msg,
2512 &sk->sk_v6_daddr, ntohs(inet->inet_dport),
2513 tcp_snd_cwnd(tp), tcp_left_out(tp),
2514 tp->snd_ssthresh, tp->prior_ssthresh,
2515 tp->packets_out);
2516 }
2517#endif
2518#endif
2519}
2520
2521static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss)
2522{
2523 struct tcp_sock *tp = tcp_sk(sk);
2524
2525 if (unmark_loss) {
2526 struct sk_buff *skb;
2527
2528 skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
2529 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2530 }
2531 tp->lost_out = 0;
2532 tcp_clear_all_retrans_hints(tp);
2533 }
2534
2535 if (tp->prior_ssthresh) {
2536 const struct inet_connection_sock *icsk = inet_csk(sk);
2537
2538 tcp_snd_cwnd_set(tp, icsk->icsk_ca_ops->undo_cwnd(sk));
2539
2540 if (tp->prior_ssthresh > tp->snd_ssthresh) {
2541 tp->snd_ssthresh = tp->prior_ssthresh;
2542 tcp_ecn_withdraw_cwr(tp);
2543 }
2544 }
2545 tp->snd_cwnd_stamp = tcp_jiffies32;
2546 tp->undo_marker = 0;
2547 tp->rack.advanced = 1; /* Force RACK to re-exam losses */
2548}
2549
2550static inline bool tcp_may_undo(const struct tcp_sock *tp)
2551{
2552 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
2553}
2554
2555static bool tcp_is_non_sack_preventing_reopen(struct sock *sk)
2556{
2557 struct tcp_sock *tp = tcp_sk(sk);
2558
2559 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
2560 /* Hold old state until something *above* high_seq
2561 * is ACKed. For Reno it is MUST to prevent false
2562 * fast retransmits (RFC2582). SACK TCP is safe. */
2563 if (!tcp_any_retrans_done(sk))
2564 tp->retrans_stamp = 0;
2565 return true;
2566 }
2567 return false;
2568}
2569
2570/* People celebrate: "We love our President!" */
2571static bool tcp_try_undo_recovery(struct sock *sk)
2572{
2573 struct tcp_sock *tp = tcp_sk(sk);
2574
2575 if (tcp_may_undo(tp)) {
2576 int mib_idx;
2577
2578 /* Happy end! We did not retransmit anything
2579 * or our original transmission succeeded.
2580 */
2581 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
2582 tcp_undo_cwnd_reduction(sk, false);
2583 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
2584 mib_idx = LINUX_MIB_TCPLOSSUNDO;
2585 else
2586 mib_idx = LINUX_MIB_TCPFULLUNDO;
2587
2588 NET_INC_STATS(sock_net(sk), mib_idx);
2589 } else if (tp->rack.reo_wnd_persist) {
2590 tp->rack.reo_wnd_persist--;
2591 }
2592 if (tcp_is_non_sack_preventing_reopen(sk))
2593 return true;
2594 tcp_set_ca_state(sk, TCP_CA_Open);
2595 tp->is_sack_reneg = 0;
2596 return false;
2597}
2598
2599/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2600static bool tcp_try_undo_dsack(struct sock *sk)
2601{
2602 struct tcp_sock *tp = tcp_sk(sk);
2603
2604 if (tp->undo_marker && !tp->undo_retrans) {
2605 tp->rack.reo_wnd_persist = min(TCP_RACK_RECOVERY_THRESH,
2606 tp->rack.reo_wnd_persist + 1);
2607 DBGUNDO(sk, "D-SACK");
2608 tcp_undo_cwnd_reduction(sk, false);
2609 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
2610 return true;
2611 }
2612 return false;
2613}
2614
2615/* Undo during loss recovery after partial ACK or using F-RTO. */
2616static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo)
2617{
2618 struct tcp_sock *tp = tcp_sk(sk);
2619
2620 if (frto_undo || tcp_may_undo(tp)) {
2621 tcp_undo_cwnd_reduction(sk, true);
2622
2623 DBGUNDO(sk, "partial loss");
2624 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
2625 if (frto_undo)
2626 NET_INC_STATS(sock_net(sk),
2627 LINUX_MIB_TCPSPURIOUSRTOS);
2628 inet_csk(sk)->icsk_retransmits = 0;
2629 if (tcp_is_non_sack_preventing_reopen(sk))
2630 return true;
2631 if (frto_undo || tcp_is_sack(tp)) {
2632 tcp_set_ca_state(sk, TCP_CA_Open);
2633 tp->is_sack_reneg = 0;
2634 }
2635 return true;
2636 }
2637 return false;
2638}
2639
2640/* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2641 * It computes the number of packets to send (sndcnt) based on packets newly
2642 * delivered:
2643 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2644 * cwnd reductions across a full RTT.
2645 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2646 * But when SND_UNA is acked without further losses,
2647 * slow starts cwnd up to ssthresh to speed up the recovery.
2648 */
2649static void tcp_init_cwnd_reduction(struct sock *sk)
2650{
2651 struct tcp_sock *tp = tcp_sk(sk);
2652
2653 tp->high_seq = tp->snd_nxt;
2654 tp->tlp_high_seq = 0;
2655 tp->snd_cwnd_cnt = 0;
2656 tp->prior_cwnd = tcp_snd_cwnd(tp);
2657 tp->prr_delivered = 0;
2658 tp->prr_out = 0;
2659 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
2660 tcp_ecn_queue_cwr(tp);
2661}
2662
2663void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int newly_lost, int flag)
2664{
2665 struct tcp_sock *tp = tcp_sk(sk);
2666 int sndcnt = 0;
2667 int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp);
2668
2669 if (newly_acked_sacked <= 0 || WARN_ON_ONCE(!tp->prior_cwnd))
2670 return;
2671
2672 tp->prr_delivered += newly_acked_sacked;
2673 if (delta < 0) {
2674 u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +
2675 tp->prior_cwnd - 1;
2676 sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out;
2677 } else {
2678 sndcnt = max_t(int, tp->prr_delivered - tp->prr_out,
2679 newly_acked_sacked);
2680 if (flag & FLAG_SND_UNA_ADVANCED && !newly_lost)
2681 sndcnt++;
2682 sndcnt = min(delta, sndcnt);
2683 }
2684 /* Force a fast retransmit upon entering fast recovery */
2685 sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1));
2686 tcp_snd_cwnd_set(tp, tcp_packets_in_flight(tp) + sndcnt);
2687}
2688
2689static inline void tcp_end_cwnd_reduction(struct sock *sk)
2690{
2691 struct tcp_sock *tp = tcp_sk(sk);
2692
2693 if (inet_csk(sk)->icsk_ca_ops->cong_control)
2694 return;
2695
2696 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2697 if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH &&
2698 (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR || tp->undo_marker)) {
2699 tcp_snd_cwnd_set(tp, tp->snd_ssthresh);
2700 tp->snd_cwnd_stamp = tcp_jiffies32;
2701 }
2702 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
2703}
2704
2705/* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2706void tcp_enter_cwr(struct sock *sk)
2707{
2708 struct tcp_sock *tp = tcp_sk(sk);
2709
2710 tp->prior_ssthresh = 0;
2711 if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
2712 tp->undo_marker = 0;
2713 tcp_init_cwnd_reduction(sk);
2714 tcp_set_ca_state(sk, TCP_CA_CWR);
2715 }
2716}
2717EXPORT_SYMBOL(tcp_enter_cwr);
2718
2719static void tcp_try_keep_open(struct sock *sk)
2720{
2721 struct tcp_sock *tp = tcp_sk(sk);
2722 int state = TCP_CA_Open;
2723
2724 if (tcp_left_out(tp) || tcp_any_retrans_done(sk))
2725 state = TCP_CA_Disorder;
2726
2727 if (inet_csk(sk)->icsk_ca_state != state) {
2728 tcp_set_ca_state(sk, state);
2729 tp->high_seq = tp->snd_nxt;
2730 }
2731}
2732
2733static void tcp_try_to_open(struct sock *sk, int flag)
2734{
2735 struct tcp_sock *tp = tcp_sk(sk);
2736
2737 tcp_verify_left_out(tp);
2738
2739 if (!tcp_any_retrans_done(sk))
2740 tp->retrans_stamp = 0;
2741
2742 if (flag & FLAG_ECE)
2743 tcp_enter_cwr(sk);
2744
2745 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
2746 tcp_try_keep_open(sk);
2747 }
2748}
2749
2750static void tcp_mtup_probe_failed(struct sock *sk)
2751{
2752 struct inet_connection_sock *icsk = inet_csk(sk);
2753
2754 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
2755 icsk->icsk_mtup.probe_size = 0;
2756 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMTUPFAIL);
2757}
2758
2759static void tcp_mtup_probe_success(struct sock *sk)
2760{
2761 struct tcp_sock *tp = tcp_sk(sk);
2762 struct inet_connection_sock *icsk = inet_csk(sk);
2763 u64 val;
2764
2765 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2766
2767 val = (u64)tcp_snd_cwnd(tp) * tcp_mss_to_mtu(sk, tp->mss_cache);
2768 do_div(val, icsk->icsk_mtup.probe_size);
2769 DEBUG_NET_WARN_ON_ONCE((u32)val != val);
2770 tcp_snd_cwnd_set(tp, max_t(u32, 1U, val));
2771
2772 tp->snd_cwnd_cnt = 0;
2773 tp->snd_cwnd_stamp = tcp_jiffies32;
2774 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2775
2776 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
2777 icsk->icsk_mtup.probe_size = 0;
2778 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
2779 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMTUPSUCCESS);
2780}
2781
2782/* Do a simple retransmit without using the backoff mechanisms in
2783 * tcp_timer. This is used for path mtu discovery.
2784 * The socket is already locked here.
2785 */
2786void tcp_simple_retransmit(struct sock *sk)
2787{
2788 const struct inet_connection_sock *icsk = inet_csk(sk);
2789 struct tcp_sock *tp = tcp_sk(sk);
2790 struct sk_buff *skb;
2791 int mss;
2792
2793 /* A fastopen SYN request is stored as two separate packets within
2794 * the retransmit queue, this is done by tcp_send_syn_data().
2795 * As a result simply checking the MSS of the frames in the queue
2796 * will not work for the SYN packet.
2797 *
2798 * Us being here is an indication of a path MTU issue so we can
2799 * assume that the fastopen SYN was lost and just mark all the
2800 * frames in the retransmit queue as lost. We will use an MSS of
2801 * -1 to mark all frames as lost, otherwise compute the current MSS.
2802 */
2803 if (tp->syn_data && sk->sk_state == TCP_SYN_SENT)
2804 mss = -1;
2805 else
2806 mss = tcp_current_mss(sk);
2807
2808 skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
2809 if (tcp_skb_seglen(skb) > mss)
2810 tcp_mark_skb_lost(sk, skb);
2811 }
2812
2813 tcp_clear_retrans_hints_partial(tp);
2814
2815 if (!tp->lost_out)
2816 return;
2817
2818 if (tcp_is_reno(tp))
2819 tcp_limit_reno_sacked(tp);
2820
2821 tcp_verify_left_out(tp);
2822
2823 /* Don't muck with the congestion window here.
2824 * Reason is that we do not increase amount of _data_
2825 * in network, but units changed and effective
2826 * cwnd/ssthresh really reduced now.
2827 */
2828 if (icsk->icsk_ca_state != TCP_CA_Loss) {
2829 tp->high_seq = tp->snd_nxt;
2830 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2831 tp->prior_ssthresh = 0;
2832 tp->undo_marker = 0;
2833 tcp_set_ca_state(sk, TCP_CA_Loss);
2834 }
2835 tcp_xmit_retransmit_queue(sk);
2836}
2837EXPORT_SYMBOL(tcp_simple_retransmit);
2838
2839void tcp_enter_recovery(struct sock *sk, bool ece_ack)
2840{
2841 struct tcp_sock *tp = tcp_sk(sk);
2842 int mib_idx;
2843
2844 if (tcp_is_reno(tp))
2845 mib_idx = LINUX_MIB_TCPRENORECOVERY;
2846 else
2847 mib_idx = LINUX_MIB_TCPSACKRECOVERY;
2848
2849 NET_INC_STATS(sock_net(sk), mib_idx);
2850
2851 tp->prior_ssthresh = 0;
2852 tcp_init_undo(tp);
2853
2854 if (!tcp_in_cwnd_reduction(sk)) {
2855 if (!ece_ack)
2856 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2857 tcp_init_cwnd_reduction(sk);
2858 }
2859 tcp_set_ca_state(sk, TCP_CA_Recovery);
2860}
2861
2862static void tcp_update_rto_time(struct tcp_sock *tp)
2863{
2864 if (tp->rto_stamp) {
2865 tp->total_rto_time += tcp_time_stamp_ms(tp) - tp->rto_stamp;
2866 tp->rto_stamp = 0;
2867 }
2868}
2869
2870/* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2871 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2872 */
2873static void tcp_process_loss(struct sock *sk, int flag, int num_dupack,
2874 int *rexmit)
2875{
2876 struct tcp_sock *tp = tcp_sk(sk);
2877 bool recovered = !before(tp->snd_una, tp->high_seq);
2878
2879 if ((flag & FLAG_SND_UNA_ADVANCED || rcu_access_pointer(tp->fastopen_rsk)) &&
2880 tcp_try_undo_loss(sk, false))
2881 return;
2882
2883 if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2884 /* Step 3.b. A timeout is spurious if not all data are
2885 * lost, i.e., never-retransmitted data are (s)acked.
2886 */
2887 if ((flag & FLAG_ORIG_SACK_ACKED) &&
2888 tcp_try_undo_loss(sk, true))
2889 return;
2890
2891 if (after(tp->snd_nxt, tp->high_seq)) {
2892 if (flag & FLAG_DATA_SACKED || num_dupack)
2893 tp->frto = 0; /* Step 3.a. loss was real */
2894 } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
2895 tp->high_seq = tp->snd_nxt;
2896 /* Step 2.b. Try send new data (but deferred until cwnd
2897 * is updated in tcp_ack()). Otherwise fall back to
2898 * the conventional recovery.
2899 */
2900 if (!tcp_write_queue_empty(sk) &&
2901 after(tcp_wnd_end(tp), tp->snd_nxt)) {
2902 *rexmit = REXMIT_NEW;
2903 return;
2904 }
2905 tp->frto = 0;
2906 }
2907 }
2908
2909 if (recovered) {
2910 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2911 tcp_try_undo_recovery(sk);
2912 return;
2913 }
2914 if (tcp_is_reno(tp)) {
2915 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2916 * delivered. Lower inflight to clock out (re)transmissions.
2917 */
2918 if (after(tp->snd_nxt, tp->high_seq) && num_dupack)
2919 tcp_add_reno_sack(sk, num_dupack, flag & FLAG_ECE);
2920 else if (flag & FLAG_SND_UNA_ADVANCED)
2921 tcp_reset_reno_sack(tp);
2922 }
2923 *rexmit = REXMIT_LOST;
2924}
2925
2926static bool tcp_force_fast_retransmit(struct sock *sk)
2927{
2928 struct tcp_sock *tp = tcp_sk(sk);
2929
2930 return after(tcp_highest_sack_seq(tp),
2931 tp->snd_una + tp->reordering * tp->mss_cache);
2932}
2933
2934/* Undo during fast recovery after partial ACK. */
2935static bool tcp_try_undo_partial(struct sock *sk, u32 prior_snd_una,
2936 bool *do_lost)
2937{
2938 struct tcp_sock *tp = tcp_sk(sk);
2939
2940 if (tp->undo_marker && tcp_packet_delayed(tp)) {
2941 /* Plain luck! Hole if filled with delayed
2942 * packet, rather than with a retransmit. Check reordering.
2943 */
2944 tcp_check_sack_reordering(sk, prior_snd_una, 1);
2945
2946 /* We are getting evidence that the reordering degree is higher
2947 * than we realized. If there are no retransmits out then we
2948 * can undo. Otherwise we clock out new packets but do not
2949 * mark more packets lost or retransmit more.
2950 */
2951 if (tp->retrans_out)
2952 return true;
2953
2954 if (!tcp_any_retrans_done(sk))
2955 tp->retrans_stamp = 0;
2956
2957 DBGUNDO(sk, "partial recovery");
2958 tcp_undo_cwnd_reduction(sk, true);
2959 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
2960 tcp_try_keep_open(sk);
2961 } else {
2962 /* Partial ACK arrived. Force fast retransmit. */
2963 *do_lost = tcp_force_fast_retransmit(sk);
2964 }
2965 return false;
2966}
2967
2968static void tcp_identify_packet_loss(struct sock *sk, int *ack_flag)
2969{
2970 struct tcp_sock *tp = tcp_sk(sk);
2971
2972 if (tcp_rtx_queue_empty(sk))
2973 return;
2974
2975 if (unlikely(tcp_is_reno(tp))) {
2976 tcp_newreno_mark_lost(sk, *ack_flag & FLAG_SND_UNA_ADVANCED);
2977 } else if (tcp_is_rack(sk)) {
2978 u32 prior_retrans = tp->retrans_out;
2979
2980 if (tcp_rack_mark_lost(sk))
2981 *ack_flag &= ~FLAG_SET_XMIT_TIMER;
2982 if (prior_retrans > tp->retrans_out)
2983 *ack_flag |= FLAG_LOST_RETRANS;
2984 }
2985}
2986
2987/* Process an event, which can update packets-in-flight not trivially.
2988 * Main goal of this function is to calculate new estimate for left_out,
2989 * taking into account both packets sitting in receiver's buffer and
2990 * packets lost by network.
2991 *
2992 * Besides that it updates the congestion state when packet loss or ECN
2993 * is detected. But it does not reduce the cwnd, it is done by the
2994 * congestion control later.
2995 *
2996 * It does _not_ decide what to send, it is made in function
2997 * tcp_xmit_retransmit_queue().
2998 */
2999static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
3000 int num_dupack, int *ack_flag, int *rexmit)
3001{
3002 struct inet_connection_sock *icsk = inet_csk(sk);
3003 struct tcp_sock *tp = tcp_sk(sk);
3004 int fast_rexmit = 0, flag = *ack_flag;
3005 bool ece_ack = flag & FLAG_ECE;
3006 bool do_lost = num_dupack || ((flag & FLAG_DATA_SACKED) &&
3007 tcp_force_fast_retransmit(sk));
3008
3009 if (!tp->packets_out && tp->sacked_out)
3010 tp->sacked_out = 0;
3011
3012 /* Now state machine starts.
3013 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
3014 if (ece_ack)
3015 tp->prior_ssthresh = 0;
3016
3017 /* B. In all the states check for reneging SACKs. */
3018 if (tcp_check_sack_reneging(sk, ack_flag))
3019 return;
3020
3021 /* C. Check consistency of the current state. */
3022 tcp_verify_left_out(tp);
3023
3024 /* D. Check state exit conditions. State can be terminated
3025 * when high_seq is ACKed. */
3026 if (icsk->icsk_ca_state == TCP_CA_Open) {
3027 WARN_ON(tp->retrans_out != 0 && !tp->syn_data);
3028 tp->retrans_stamp = 0;
3029 } else if (!before(tp->snd_una, tp->high_seq)) {
3030 switch (icsk->icsk_ca_state) {
3031 case TCP_CA_CWR:
3032 /* CWR is to be held something *above* high_seq
3033 * is ACKed for CWR bit to reach receiver. */
3034 if (tp->snd_una != tp->high_seq) {
3035 tcp_end_cwnd_reduction(sk);
3036 tcp_set_ca_state(sk, TCP_CA_Open);
3037 }
3038 break;
3039
3040 case TCP_CA_Recovery:
3041 if (tcp_is_reno(tp))
3042 tcp_reset_reno_sack(tp);
3043 if (tcp_try_undo_recovery(sk))
3044 return;
3045 tcp_end_cwnd_reduction(sk);
3046 break;
3047 }
3048 }
3049
3050 /* E. Process state. */
3051 switch (icsk->icsk_ca_state) {
3052 case TCP_CA_Recovery:
3053 if (!(flag & FLAG_SND_UNA_ADVANCED)) {
3054 if (tcp_is_reno(tp))
3055 tcp_add_reno_sack(sk, num_dupack, ece_ack);
3056 } else if (tcp_try_undo_partial(sk, prior_snd_una, &do_lost))
3057 return;
3058
3059 if (tcp_try_undo_dsack(sk))
3060 tcp_try_keep_open(sk);
3061
3062 tcp_identify_packet_loss(sk, ack_flag);
3063 if (icsk->icsk_ca_state != TCP_CA_Recovery) {
3064 if (!tcp_time_to_recover(sk, flag))
3065 return;
3066 /* Undo reverts the recovery state. If loss is evident,
3067 * starts a new recovery (e.g. reordering then loss);
3068 */
3069 tcp_enter_recovery(sk, ece_ack);
3070 }
3071 break;
3072 case TCP_CA_Loss:
3073 tcp_process_loss(sk, flag, num_dupack, rexmit);
3074 if (icsk->icsk_ca_state != TCP_CA_Loss)
3075 tcp_update_rto_time(tp);
3076 tcp_identify_packet_loss(sk, ack_flag);
3077 if (!(icsk->icsk_ca_state == TCP_CA_Open ||
3078 (*ack_flag & FLAG_LOST_RETRANS)))
3079 return;
3080 /* Change state if cwnd is undone or retransmits are lost */
3081 fallthrough;
3082 default:
3083 if (tcp_is_reno(tp)) {
3084 if (flag & FLAG_SND_UNA_ADVANCED)
3085 tcp_reset_reno_sack(tp);
3086 tcp_add_reno_sack(sk, num_dupack, ece_ack);
3087 }
3088
3089 if (icsk->icsk_ca_state <= TCP_CA_Disorder)
3090 tcp_try_undo_dsack(sk);
3091
3092 tcp_identify_packet_loss(sk, ack_flag);
3093 if (!tcp_time_to_recover(sk, flag)) {
3094 tcp_try_to_open(sk, flag);
3095 return;
3096 }
3097
3098 /* MTU probe failure: don't reduce cwnd */
3099 if (icsk->icsk_ca_state < TCP_CA_CWR &&
3100 icsk->icsk_mtup.probe_size &&
3101 tp->snd_una == tp->mtu_probe.probe_seq_start) {
3102 tcp_mtup_probe_failed(sk);
3103 /* Restores the reduction we did in tcp_mtup_probe() */
3104 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
3105 tcp_simple_retransmit(sk);
3106 return;
3107 }
3108
3109 /* Otherwise enter Recovery state */
3110 tcp_enter_recovery(sk, ece_ack);
3111 fast_rexmit = 1;
3112 }
3113
3114 if (!tcp_is_rack(sk) && do_lost)
3115 tcp_update_scoreboard(sk, fast_rexmit);
3116 *rexmit = REXMIT_LOST;
3117}
3118
3119static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us, const int flag)
3120{
3121 u32 wlen = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen) * HZ;
3122 struct tcp_sock *tp = tcp_sk(sk);
3123
3124 if ((flag & FLAG_ACK_MAYBE_DELAYED) && rtt_us > tcp_min_rtt(tp)) {
3125 /* If the remote keeps returning delayed ACKs, eventually
3126 * the min filter would pick it up and overestimate the
3127 * prop. delay when it expires. Skip suspected delayed ACKs.
3128 */
3129 return;
3130 }
3131 minmax_running_min(&tp->rtt_min, wlen, tcp_jiffies32,
3132 rtt_us ? : jiffies_to_usecs(1));
3133}
3134
3135static bool tcp_ack_update_rtt(struct sock *sk, const int flag,
3136 long seq_rtt_us, long sack_rtt_us,
3137 long ca_rtt_us, struct rate_sample *rs)
3138{
3139 const struct tcp_sock *tp = tcp_sk(sk);
3140
3141 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
3142 * broken middle-boxes or peers may corrupt TS-ECR fields. But
3143 * Karn's algorithm forbids taking RTT if some retransmitted data
3144 * is acked (RFC6298).
3145 */
3146 if (seq_rtt_us < 0)
3147 seq_rtt_us = sack_rtt_us;
3148
3149 /* RTTM Rule: A TSecr value received in a segment is used to
3150 * update the averaged RTT measurement only if the segment
3151 * acknowledges some new data, i.e., only if it advances the
3152 * left edge of the send window.
3153 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3154 */
3155 if (seq_rtt_us < 0 && tp->rx_opt.saw_tstamp &&
3156 tp->rx_opt.rcv_tsecr && flag & FLAG_ACKED)
3157 seq_rtt_us = ca_rtt_us = tcp_rtt_tsopt_us(tp);
3158
3159 rs->rtt_us = ca_rtt_us; /* RTT of last (S)ACKed packet (or -1) */
3160 if (seq_rtt_us < 0)
3161 return false;
3162
3163 /* ca_rtt_us >= 0 is counting on the invariant that ca_rtt_us is
3164 * always taken together with ACK, SACK, or TS-opts. Any negative
3165 * values will be skipped with the seq_rtt_us < 0 check above.
3166 */
3167 tcp_update_rtt_min(sk, ca_rtt_us, flag);
3168 tcp_rtt_estimator(sk, seq_rtt_us);
3169 tcp_set_rto(sk);
3170
3171 /* RFC6298: only reset backoff on valid RTT measurement. */
3172 inet_csk(sk)->icsk_backoff = 0;
3173 return true;
3174}
3175
3176/* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
3177void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req)
3178{
3179 struct rate_sample rs;
3180 long rtt_us = -1L;
3181
3182 if (req && !req->num_retrans && tcp_rsk(req)->snt_synack)
3183 rtt_us = tcp_stamp_us_delta(tcp_clock_us(), tcp_rsk(req)->snt_synack);
3184
3185 tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, rtt_us, -1L, rtt_us, &rs);
3186}
3187
3188
3189static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
3190{
3191 const struct inet_connection_sock *icsk = inet_csk(sk);
3192
3193 icsk->icsk_ca_ops->cong_avoid(sk, ack, acked);
3194 tcp_sk(sk)->snd_cwnd_stamp = tcp_jiffies32;
3195}
3196
3197/* Restart timer after forward progress on connection.
3198 * RFC2988 recommends to restart timer to now+rto.
3199 */
3200void tcp_rearm_rto(struct sock *sk)
3201{
3202 const struct inet_connection_sock *icsk = inet_csk(sk);
3203 struct tcp_sock *tp = tcp_sk(sk);
3204
3205 /* If the retrans timer is currently being used by Fast Open
3206 * for SYN-ACK retrans purpose, stay put.
3207 */
3208 if (rcu_access_pointer(tp->fastopen_rsk))
3209 return;
3210
3211 if (!tp->packets_out) {
3212 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
3213 } else {
3214 u32 rto = inet_csk(sk)->icsk_rto;
3215 /* Offset the time elapsed after installing regular RTO */
3216 if (icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT ||
3217 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
3218 s64 delta_us = tcp_rto_delta_us(sk);
3219 /* delta_us may not be positive if the socket is locked
3220 * when the retrans timer fires and is rescheduled.
3221 */
3222 rto = usecs_to_jiffies(max_t(int, delta_us, 1));
3223 }
3224 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
3225 TCP_RTO_MAX);
3226 }
3227}
3228
3229/* Try to schedule a loss probe; if that doesn't work, then schedule an RTO. */
3230static void tcp_set_xmit_timer(struct sock *sk)
3231{
3232 if (!tcp_schedule_loss_probe(sk, true))
3233 tcp_rearm_rto(sk);
3234}
3235
3236/* If we get here, the whole TSO packet has not been acked. */
3237static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
3238{
3239 struct tcp_sock *tp = tcp_sk(sk);
3240 u32 packets_acked;
3241
3242 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
3243
3244 packets_acked = tcp_skb_pcount(skb);
3245 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3246 return 0;
3247 packets_acked -= tcp_skb_pcount(skb);
3248
3249 if (packets_acked) {
3250 BUG_ON(tcp_skb_pcount(skb) == 0);
3251 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
3252 }
3253
3254 return packets_acked;
3255}
3256
3257static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
3258 const struct sk_buff *ack_skb, u32 prior_snd_una)
3259{
3260 const struct skb_shared_info *shinfo;
3261
3262 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3263 if (likely(!TCP_SKB_CB(skb)->txstamp_ack))
3264 return;
3265
3266 shinfo = skb_shinfo(skb);
3267 if (!before(shinfo->tskey, prior_snd_una) &&
3268 before(shinfo->tskey, tcp_sk(sk)->snd_una)) {
3269 tcp_skb_tsorted_save(skb) {
3270 __skb_tstamp_tx(skb, ack_skb, NULL, sk, SCM_TSTAMP_ACK);
3271 } tcp_skb_tsorted_restore(skb);
3272 }
3273}
3274
3275/* Remove acknowledged frames from the retransmission queue. If our packet
3276 * is before the ack sequence we can discard it as it's confirmed to have
3277 * arrived at the other end.
3278 */
3279static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb,
3280 u32 prior_fack, u32 prior_snd_una,
3281 struct tcp_sacktag_state *sack, bool ece_ack)
3282{
3283 const struct inet_connection_sock *icsk = inet_csk(sk);
3284 u64 first_ackt, last_ackt;
3285 struct tcp_sock *tp = tcp_sk(sk);
3286 u32 prior_sacked = tp->sacked_out;
3287 u32 reord = tp->snd_nxt; /* lowest acked un-retx un-sacked seq */
3288 struct sk_buff *skb, *next;
3289 bool fully_acked = true;
3290 long sack_rtt_us = -1L;
3291 long seq_rtt_us = -1L;
3292 long ca_rtt_us = -1L;
3293 u32 pkts_acked = 0;
3294 bool rtt_update;
3295 int flag = 0;
3296
3297 first_ackt = 0;
3298
3299 for (skb = skb_rb_first(&sk->tcp_rtx_queue); skb; skb = next) {
3300 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
3301 const u32 start_seq = scb->seq;
3302 u8 sacked = scb->sacked;
3303 u32 acked_pcount;
3304
3305 /* Determine how many packets and what bytes were acked, tso and else */
3306 if (after(scb->end_seq, tp->snd_una)) {
3307 if (tcp_skb_pcount(skb) == 1 ||
3308 !after(tp->snd_una, scb->seq))
3309 break;
3310
3311 acked_pcount = tcp_tso_acked(sk, skb);
3312 if (!acked_pcount)
3313 break;
3314 fully_acked = false;
3315 } else {
3316 acked_pcount = tcp_skb_pcount(skb);
3317 }
3318
3319 if (unlikely(sacked & TCPCB_RETRANS)) {
3320 if (sacked & TCPCB_SACKED_RETRANS)
3321 tp->retrans_out -= acked_pcount;
3322 flag |= FLAG_RETRANS_DATA_ACKED;
3323 } else if (!(sacked & TCPCB_SACKED_ACKED)) {
3324 last_ackt = tcp_skb_timestamp_us(skb);
3325 WARN_ON_ONCE(last_ackt == 0);
3326 if (!first_ackt)
3327 first_ackt = last_ackt;
3328
3329 if (before(start_seq, reord))
3330 reord = start_seq;
3331 if (!after(scb->end_seq, tp->high_seq))
3332 flag |= FLAG_ORIG_SACK_ACKED;
3333 }
3334
3335 if (sacked & TCPCB_SACKED_ACKED) {
3336 tp->sacked_out -= acked_pcount;
3337 } else if (tcp_is_sack(tp)) {
3338 tcp_count_delivered(tp, acked_pcount, ece_ack);
3339 if (!tcp_skb_spurious_retrans(tp, skb))
3340 tcp_rack_advance(tp, sacked, scb->end_seq,
3341 tcp_skb_timestamp_us(skb));
3342 }
3343 if (sacked & TCPCB_LOST)
3344 tp->lost_out -= acked_pcount;
3345
3346 tp->packets_out -= acked_pcount;
3347 pkts_acked += acked_pcount;
3348 tcp_rate_skb_delivered(sk, skb, sack->rate);
3349
3350 /* Initial outgoing SYN's get put onto the write_queue
3351 * just like anything else we transmit. It is not
3352 * true data, and if we misinform our callers that
3353 * this ACK acks real data, we will erroneously exit
3354 * connection startup slow start one packet too
3355 * quickly. This is severely frowned upon behavior.
3356 */
3357 if (likely(!(scb->tcp_flags & TCPHDR_SYN))) {
3358 flag |= FLAG_DATA_ACKED;
3359 } else {
3360 flag |= FLAG_SYN_ACKED;
3361 tp->retrans_stamp = 0;
3362 }
3363
3364 if (!fully_acked)
3365 break;
3366
3367 tcp_ack_tstamp(sk, skb, ack_skb, prior_snd_una);
3368
3369 next = skb_rb_next(skb);
3370 if (unlikely(skb == tp->retransmit_skb_hint))
3371 tp->retransmit_skb_hint = NULL;
3372 if (unlikely(skb == tp->lost_skb_hint))
3373 tp->lost_skb_hint = NULL;
3374 tcp_highest_sack_replace(sk, skb, next);
3375 tcp_rtx_queue_unlink_and_free(skb, sk);
3376 }
3377
3378 if (!skb)
3379 tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
3380
3381 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
3382 tp->snd_up = tp->snd_una;
3383
3384 if (skb) {
3385 tcp_ack_tstamp(sk, skb, ack_skb, prior_snd_una);
3386 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
3387 flag |= FLAG_SACK_RENEGING;
3388 }
3389
3390 if (likely(first_ackt) && !(flag & FLAG_RETRANS_DATA_ACKED)) {
3391 seq_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, first_ackt);
3392 ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, last_ackt);
3393
3394 if (pkts_acked == 1 && fully_acked && !prior_sacked &&
3395 (tp->snd_una - prior_snd_una) < tp->mss_cache &&
3396 sack->rate->prior_delivered + 1 == tp->delivered &&
3397 !(flag & (FLAG_CA_ALERT | FLAG_SYN_ACKED))) {
3398 /* Conservatively mark a delayed ACK. It's typically
3399 * from a lone runt packet over the round trip to
3400 * a receiver w/o out-of-order or CE events.
3401 */
3402 flag |= FLAG_ACK_MAYBE_DELAYED;
3403 }
3404 }
3405 if (sack->first_sackt) {
3406 sack_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, sack->first_sackt);
3407 ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, sack->last_sackt);
3408 }
3409 rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt_us, sack_rtt_us,
3410 ca_rtt_us, sack->rate);
3411
3412 if (flag & FLAG_ACKED) {
3413 flag |= FLAG_SET_XMIT_TIMER; /* set TLP or RTO timer */
3414 if (unlikely(icsk->icsk_mtup.probe_size &&
3415 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
3416 tcp_mtup_probe_success(sk);
3417 }
3418
3419 if (tcp_is_reno(tp)) {
3420 tcp_remove_reno_sacks(sk, pkts_acked, ece_ack);
3421
3422 /* If any of the cumulatively ACKed segments was
3423 * retransmitted, non-SACK case cannot confirm that
3424 * progress was due to original transmission due to
3425 * lack of TCPCB_SACKED_ACKED bits even if some of
3426 * the packets may have been never retransmitted.
3427 */
3428 if (flag & FLAG_RETRANS_DATA_ACKED)
3429 flag &= ~FLAG_ORIG_SACK_ACKED;
3430 } else {
3431 int delta;
3432
3433 /* Non-retransmitted hole got filled? That's reordering */
3434 if (before(reord, prior_fack))
3435 tcp_check_sack_reordering(sk, reord, 0);
3436
3437 delta = prior_sacked - tp->sacked_out;
3438 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
3439 }
3440 } else if (skb && rtt_update && sack_rtt_us >= 0 &&
3441 sack_rtt_us > tcp_stamp_us_delta(tp->tcp_mstamp,
3442 tcp_skb_timestamp_us(skb))) {
3443 /* Do not re-arm RTO if the sack RTT is measured from data sent
3444 * after when the head was last (re)transmitted. Otherwise the
3445 * timeout may continue to extend in loss recovery.
3446 */
3447 flag |= FLAG_SET_XMIT_TIMER; /* set TLP or RTO timer */
3448 }
3449
3450 if (icsk->icsk_ca_ops->pkts_acked) {
3451 struct ack_sample sample = { .pkts_acked = pkts_acked,
3452 .rtt_us = sack->rate->rtt_us };
3453
3454 sample.in_flight = tp->mss_cache *
3455 (tp->delivered - sack->rate->prior_delivered);
3456 icsk->icsk_ca_ops->pkts_acked(sk, &sample);
3457 }
3458
3459#if FASTRETRANS_DEBUG > 0
3460 WARN_ON((int)tp->sacked_out < 0);
3461 WARN_ON((int)tp->lost_out < 0);
3462 WARN_ON((int)tp->retrans_out < 0);
3463 if (!tp->packets_out && tcp_is_sack(tp)) {
3464 icsk = inet_csk(sk);
3465 if (tp->lost_out) {
3466 pr_debug("Leak l=%u %d\n",
3467 tp->lost_out, icsk->icsk_ca_state);
3468 tp->lost_out = 0;
3469 }
3470 if (tp->sacked_out) {
3471 pr_debug("Leak s=%u %d\n",
3472 tp->sacked_out, icsk->icsk_ca_state);
3473 tp->sacked_out = 0;
3474 }
3475 if (tp->retrans_out) {
3476 pr_debug("Leak r=%u %d\n",
3477 tp->retrans_out, icsk->icsk_ca_state);
3478 tp->retrans_out = 0;
3479 }
3480 }
3481#endif
3482 return flag;
3483}
3484
3485static void tcp_ack_probe(struct sock *sk)
3486{
3487 struct inet_connection_sock *icsk = inet_csk(sk);
3488 struct sk_buff *head = tcp_send_head(sk);
3489 const struct tcp_sock *tp = tcp_sk(sk);
3490
3491 /* Was it a usable window open? */
3492 if (!head)
3493 return;
3494 if (!after(TCP_SKB_CB(head)->end_seq, tcp_wnd_end(tp))) {
3495 icsk->icsk_backoff = 0;
3496 icsk->icsk_probes_tstamp = 0;
3497 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
3498 /* Socket must be waked up by subsequent tcp_data_snd_check().
3499 * This function is not for random using!
3500 */
3501 } else {
3502 unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX);
3503
3504 when = tcp_clamp_probe0_to_user_timeout(sk, when);
3505 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, when, TCP_RTO_MAX);
3506 }
3507}
3508
3509static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag)
3510{
3511 return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
3512 inet_csk(sk)->icsk_ca_state != TCP_CA_Open;
3513}
3514
3515/* Decide wheather to run the increase function of congestion control. */
3516static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
3517{
3518 /* If reordering is high then always grow cwnd whenever data is
3519 * delivered regardless of its ordering. Otherwise stay conservative
3520 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3521 * new SACK or ECE mark may first advance cwnd here and later reduce
3522 * cwnd in tcp_fastretrans_alert() based on more states.
3523 */
3524 if (tcp_sk(sk)->reordering >
3525 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reordering))
3526 return flag & FLAG_FORWARD_PROGRESS;
3527
3528 return flag & FLAG_DATA_ACKED;
3529}
3530
3531/* The "ultimate" congestion control function that aims to replace the rigid
3532 * cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction).
3533 * It's called toward the end of processing an ACK with precise rate
3534 * information. All transmission or retransmission are delayed afterwards.
3535 */
3536static void tcp_cong_control(struct sock *sk, u32 ack, u32 acked_sacked,
3537 int flag, const struct rate_sample *rs)
3538{
3539 const struct inet_connection_sock *icsk = inet_csk(sk);
3540
3541 if (icsk->icsk_ca_ops->cong_control) {
3542 icsk->icsk_ca_ops->cong_control(sk, rs);
3543 return;
3544 }
3545
3546 if (tcp_in_cwnd_reduction(sk)) {
3547 /* Reduce cwnd if state mandates */
3548 tcp_cwnd_reduction(sk, acked_sacked, rs->losses, flag);
3549 } else if (tcp_may_raise_cwnd(sk, flag)) {
3550 /* Advance cwnd if state allows */
3551 tcp_cong_avoid(sk, ack, acked_sacked);
3552 }
3553 tcp_update_pacing_rate(sk);
3554}
3555
3556/* Check that window update is acceptable.
3557 * The function assumes that snd_una<=ack<=snd_next.
3558 */
3559static inline bool tcp_may_update_window(const struct tcp_sock *tp,
3560 const u32 ack, const u32 ack_seq,
3561 const u32 nwin)
3562{
3563 return after(ack, tp->snd_una) ||
3564 after(ack_seq, tp->snd_wl1) ||
3565 (ack_seq == tp->snd_wl1 && (nwin > tp->snd_wnd || !nwin));
3566}
3567
3568static void tcp_snd_sne_update(struct tcp_sock *tp, u32 ack)
3569{
3570#ifdef CONFIG_TCP_AO
3571 struct tcp_ao_info *ao;
3572
3573 if (!static_branch_unlikely(&tcp_ao_needed.key))
3574 return;
3575
3576 ao = rcu_dereference_protected(tp->ao_info,
3577 lockdep_sock_is_held((struct sock *)tp));
3578 if (ao && ack < tp->snd_una)
3579 ao->snd_sne++;
3580#endif
3581}
3582
3583/* If we update tp->snd_una, also update tp->bytes_acked */
3584static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
3585{
3586 u32 delta = ack - tp->snd_una;
3587
3588 sock_owned_by_me((struct sock *)tp);
3589 tp->bytes_acked += delta;
3590 tcp_snd_sne_update(tp, ack);
3591 tp->snd_una = ack;
3592}
3593
3594static void tcp_rcv_sne_update(struct tcp_sock *tp, u32 seq)
3595{
3596#ifdef CONFIG_TCP_AO
3597 struct tcp_ao_info *ao;
3598
3599 if (!static_branch_unlikely(&tcp_ao_needed.key))
3600 return;
3601
3602 ao = rcu_dereference_protected(tp->ao_info,
3603 lockdep_sock_is_held((struct sock *)tp));
3604 if (ao && seq < tp->rcv_nxt)
3605 ao->rcv_sne++;
3606#endif
3607}
3608
3609/* If we update tp->rcv_nxt, also update tp->bytes_received */
3610static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
3611{
3612 u32 delta = seq - tp->rcv_nxt;
3613
3614 sock_owned_by_me((struct sock *)tp);
3615 tp->bytes_received += delta;
3616 tcp_rcv_sne_update(tp, seq);
3617 WRITE_ONCE(tp->rcv_nxt, seq);
3618}
3619
3620/* Update our send window.
3621 *
3622 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3623 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3624 */
3625static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack,
3626 u32 ack_seq)
3627{
3628 struct tcp_sock *tp = tcp_sk(sk);
3629 int flag = 0;
3630 u32 nwin = ntohs(tcp_hdr(skb)->window);
3631
3632 if (likely(!tcp_hdr(skb)->syn))
3633 nwin <<= tp->rx_opt.snd_wscale;
3634
3635 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
3636 flag |= FLAG_WIN_UPDATE;
3637 tcp_update_wl(tp, ack_seq);
3638
3639 if (tp->snd_wnd != nwin) {
3640 tp->snd_wnd = nwin;
3641
3642 /* Note, it is the only place, where
3643 * fast path is recovered for sending TCP.
3644 */
3645 tp->pred_flags = 0;
3646 tcp_fast_path_check(sk);
3647
3648 if (!tcp_write_queue_empty(sk))
3649 tcp_slow_start_after_idle_check(sk);
3650
3651 if (nwin > tp->max_window) {
3652 tp->max_window = nwin;
3653 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
3654 }
3655 }
3656 }
3657
3658 tcp_snd_una_update(tp, ack);
3659
3660 return flag;
3661}
3662
3663static bool __tcp_oow_rate_limited(struct net *net, int mib_idx,
3664 u32 *last_oow_ack_time)
3665{
3666 /* Paired with the WRITE_ONCE() in this function. */
3667 u32 val = READ_ONCE(*last_oow_ack_time);
3668
3669 if (val) {
3670 s32 elapsed = (s32)(tcp_jiffies32 - val);
3671
3672 if (0 <= elapsed &&
3673 elapsed < READ_ONCE(net->ipv4.sysctl_tcp_invalid_ratelimit)) {
3674 NET_INC_STATS(net, mib_idx);
3675 return true; /* rate-limited: don't send yet! */
3676 }
3677 }
3678
3679 /* Paired with the prior READ_ONCE() and with itself,
3680 * as we might be lockless.
3681 */
3682 WRITE_ONCE(*last_oow_ack_time, tcp_jiffies32);
3683
3684 return false; /* not rate-limited: go ahead, send dupack now! */
3685}
3686
3687/* Return true if we're currently rate-limiting out-of-window ACKs and
3688 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3689 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3690 * attacks that send repeated SYNs or ACKs for the same connection. To
3691 * do this, we do not send a duplicate SYNACK or ACK if the remote
3692 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3693 */
3694bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
3695 int mib_idx, u32 *last_oow_ack_time)
3696{
3697 /* Data packets without SYNs are not likely part of an ACK loop. */
3698 if ((TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) &&
3699 !tcp_hdr(skb)->syn)
3700 return false;
3701
3702 return __tcp_oow_rate_limited(net, mib_idx, last_oow_ack_time);
3703}
3704
3705/* RFC 5961 7 [ACK Throttling] */
3706static void tcp_send_challenge_ack(struct sock *sk)
3707{
3708 struct tcp_sock *tp = tcp_sk(sk);
3709 struct net *net = sock_net(sk);
3710 u32 count, now, ack_limit;
3711
3712 /* First check our per-socket dupack rate limit. */
3713 if (__tcp_oow_rate_limited(net,
3714 LINUX_MIB_TCPACKSKIPPEDCHALLENGE,
3715 &tp->last_oow_ack_time))
3716 return;
3717
3718 ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit);
3719 if (ack_limit == INT_MAX)
3720 goto send_ack;
3721
3722 /* Then check host-wide RFC 5961 rate limit. */
3723 now = jiffies / HZ;
3724 if (now != READ_ONCE(net->ipv4.tcp_challenge_timestamp)) {
3725 u32 half = (ack_limit + 1) >> 1;
3726
3727 WRITE_ONCE(net->ipv4.tcp_challenge_timestamp, now);
3728 WRITE_ONCE(net->ipv4.tcp_challenge_count,
3729 get_random_u32_inclusive(half, ack_limit + half - 1));
3730 }
3731 count = READ_ONCE(net->ipv4.tcp_challenge_count);
3732 if (count > 0) {
3733 WRITE_ONCE(net->ipv4.tcp_challenge_count, count - 1);
3734send_ack:
3735 NET_INC_STATS(net, LINUX_MIB_TCPCHALLENGEACK);
3736 tcp_send_ack(sk);
3737 }
3738}
3739
3740static void tcp_store_ts_recent(struct tcp_sock *tp)
3741{
3742 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
3743 tp->rx_opt.ts_recent_stamp = ktime_get_seconds();
3744}
3745
3746static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3747{
3748 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3749 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3750 * extra check below makes sure this can only happen
3751 * for pure ACK frames. -DaveM
3752 *
3753 * Not only, also it occurs for expired timestamps.
3754 */
3755
3756 if (tcp_paws_check(&tp->rx_opt, 0))
3757 tcp_store_ts_recent(tp);
3758 }
3759}
3760
3761/* This routine deals with acks during a TLP episode and ends an episode by
3762 * resetting tlp_high_seq. Ref: TLP algorithm in draft-ietf-tcpm-rack
3763 */
3764static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag)
3765{
3766 struct tcp_sock *tp = tcp_sk(sk);
3767
3768 if (before(ack, tp->tlp_high_seq))
3769 return;
3770
3771 if (!tp->tlp_retrans) {
3772 /* TLP of new data has been acknowledged */
3773 tp->tlp_high_seq = 0;
3774 } else if (flag & FLAG_DSACK_TLP) {
3775 /* This DSACK means original and TLP probe arrived; no loss */
3776 tp->tlp_high_seq = 0;
3777 } else if (after(ack, tp->tlp_high_seq)) {
3778 /* ACK advances: there was a loss, so reduce cwnd. Reset
3779 * tlp_high_seq in tcp_init_cwnd_reduction()
3780 */
3781 tcp_init_cwnd_reduction(sk);
3782 tcp_set_ca_state(sk, TCP_CA_CWR);
3783 tcp_end_cwnd_reduction(sk);
3784 tcp_try_keep_open(sk);
3785 NET_INC_STATS(sock_net(sk),
3786 LINUX_MIB_TCPLOSSPROBERECOVERY);
3787 } else if (!(flag & (FLAG_SND_UNA_ADVANCED |
3788 FLAG_NOT_DUP | FLAG_DATA_SACKED))) {
3789 /* Pure dupack: original and TLP probe arrived; no loss */
3790 tp->tlp_high_seq = 0;
3791 }
3792}
3793
3794static inline void tcp_in_ack_event(struct sock *sk, u32 flags)
3795{
3796 const struct inet_connection_sock *icsk = inet_csk(sk);
3797
3798 if (icsk->icsk_ca_ops->in_ack_event)
3799 icsk->icsk_ca_ops->in_ack_event(sk, flags);
3800}
3801
3802/* Congestion control has updated the cwnd already. So if we're in
3803 * loss recovery then now we do any new sends (for FRTO) or
3804 * retransmits (for CA_Loss or CA_recovery) that make sense.
3805 */
3806static void tcp_xmit_recovery(struct sock *sk, int rexmit)
3807{
3808 struct tcp_sock *tp = tcp_sk(sk);
3809
3810 if (rexmit == REXMIT_NONE || sk->sk_state == TCP_SYN_SENT)
3811 return;
3812
3813 if (unlikely(rexmit == REXMIT_NEW)) {
3814 __tcp_push_pending_frames(sk, tcp_current_mss(sk),
3815 TCP_NAGLE_OFF);
3816 if (after(tp->snd_nxt, tp->high_seq))
3817 return;
3818 tp->frto = 0;
3819 }
3820 tcp_xmit_retransmit_queue(sk);
3821}
3822
3823/* Returns the number of packets newly acked or sacked by the current ACK */
3824static u32 tcp_newly_delivered(struct sock *sk, u32 prior_delivered, int flag)
3825{
3826 const struct net *net = sock_net(sk);
3827 struct tcp_sock *tp = tcp_sk(sk);
3828 u32 delivered;
3829
3830 delivered = tp->delivered - prior_delivered;
3831 NET_ADD_STATS(net, LINUX_MIB_TCPDELIVERED, delivered);
3832 if (flag & FLAG_ECE)
3833 NET_ADD_STATS(net, LINUX_MIB_TCPDELIVEREDCE, delivered);
3834
3835 return delivered;
3836}
3837
3838/* This routine deals with incoming acks, but not outgoing ones. */
3839static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
3840{
3841 struct inet_connection_sock *icsk = inet_csk(sk);
3842 struct tcp_sock *tp = tcp_sk(sk);
3843 struct tcp_sacktag_state sack_state;
3844 struct rate_sample rs = { .prior_delivered = 0 };
3845 u32 prior_snd_una = tp->snd_una;
3846 bool is_sack_reneg = tp->is_sack_reneg;
3847 u32 ack_seq = TCP_SKB_CB(skb)->seq;
3848 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3849 int num_dupack = 0;
3850 int prior_packets = tp->packets_out;
3851 u32 delivered = tp->delivered;
3852 u32 lost = tp->lost;
3853 int rexmit = REXMIT_NONE; /* Flag to (re)transmit to recover losses */
3854 u32 prior_fack;
3855
3856 sack_state.first_sackt = 0;
3857 sack_state.rate = &rs;
3858 sack_state.sack_delivered = 0;
3859
3860 /* We very likely will need to access rtx queue. */
3861 prefetch(sk->tcp_rtx_queue.rb_node);
3862
3863 /* If the ack is older than previous acks
3864 * then we can probably ignore it.
3865 */
3866 if (before(ack, prior_snd_una)) {
3867 u32 max_window;
3868
3869 /* do not accept ACK for bytes we never sent. */
3870 max_window = min_t(u64, tp->max_window, tp->bytes_acked);
3871 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3872 if (before(ack, prior_snd_una - max_window)) {
3873 if (!(flag & FLAG_NO_CHALLENGE_ACK))
3874 tcp_send_challenge_ack(sk);
3875 return -SKB_DROP_REASON_TCP_TOO_OLD_ACK;
3876 }
3877 goto old_ack;
3878 }
3879
3880 /* If the ack includes data we haven't sent yet, discard
3881 * this segment (RFC793 Section 3.9).
3882 */
3883 if (after(ack, tp->snd_nxt))
3884 return -SKB_DROP_REASON_TCP_ACK_UNSENT_DATA;
3885
3886 if (after(ack, prior_snd_una)) {
3887 flag |= FLAG_SND_UNA_ADVANCED;
3888 icsk->icsk_retransmits = 0;
3889
3890#if IS_ENABLED(CONFIG_TLS_DEVICE)
3891 if (static_branch_unlikely(&clean_acked_data_enabled.key))
3892 if (icsk->icsk_clean_acked)
3893 icsk->icsk_clean_acked(sk, ack);
3894#endif
3895 }
3896
3897 prior_fack = tcp_is_sack(tp) ? tcp_highest_sack_seq(tp) : tp->snd_una;
3898 rs.prior_in_flight = tcp_packets_in_flight(tp);
3899
3900 /* ts_recent update must be made after we are sure that the packet
3901 * is in window.
3902 */
3903 if (flag & FLAG_UPDATE_TS_RECENT)
3904 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
3905
3906 if ((flag & (FLAG_SLOWPATH | FLAG_SND_UNA_ADVANCED)) ==
3907 FLAG_SND_UNA_ADVANCED) {
3908 /* Window is constant, pure forward advance.
3909 * No more checks are required.
3910 * Note, we use the fact that SND.UNA>=SND.WL2.
3911 */
3912 tcp_update_wl(tp, ack_seq);
3913 tcp_snd_una_update(tp, ack);
3914 flag |= FLAG_WIN_UPDATE;
3915
3916 tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE);
3917
3918 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPACKS);
3919 } else {
3920 u32 ack_ev_flags = CA_ACK_SLOWPATH;
3921
3922 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
3923 flag |= FLAG_DATA;
3924 else
3925 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPUREACKS);
3926
3927 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
3928
3929 if (TCP_SKB_CB(skb)->sacked)
3930 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
3931 &sack_state);
3932
3933 if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) {
3934 flag |= FLAG_ECE;
3935 ack_ev_flags |= CA_ACK_ECE;
3936 }
3937
3938 if (sack_state.sack_delivered)
3939 tcp_count_delivered(tp, sack_state.sack_delivered,
3940 flag & FLAG_ECE);
3941
3942 if (flag & FLAG_WIN_UPDATE)
3943 ack_ev_flags |= CA_ACK_WIN_UPDATE;
3944
3945 tcp_in_ack_event(sk, ack_ev_flags);
3946 }
3947
3948 /* This is a deviation from RFC3168 since it states that:
3949 * "When the TCP data sender is ready to set the CWR bit after reducing
3950 * the congestion window, it SHOULD set the CWR bit only on the first
3951 * new data packet that it transmits."
3952 * We accept CWR on pure ACKs to be more robust
3953 * with widely-deployed TCP implementations that do this.
3954 */
3955 tcp_ecn_accept_cwr(sk, skb);
3956
3957 /* We passed data and got it acked, remove any soft error
3958 * log. Something worked...
3959 */
3960 WRITE_ONCE(sk->sk_err_soft, 0);
3961 icsk->icsk_probes_out = 0;
3962 tp->rcv_tstamp = tcp_jiffies32;
3963 if (!prior_packets)
3964 goto no_queue;
3965
3966 /* See if we can take anything off of the retransmit queue. */
3967 flag |= tcp_clean_rtx_queue(sk, skb, prior_fack, prior_snd_una,
3968 &sack_state, flag & FLAG_ECE);
3969
3970 tcp_rack_update_reo_wnd(sk, &rs);
3971
3972 if (tp->tlp_high_seq)
3973 tcp_process_tlp_ack(sk, ack, flag);
3974
3975 if (tcp_ack_is_dubious(sk, flag)) {
3976 if (!(flag & (FLAG_SND_UNA_ADVANCED |
3977 FLAG_NOT_DUP | FLAG_DSACKING_ACK))) {
3978 num_dupack = 1;
3979 /* Consider if pure acks were aggregated in tcp_add_backlog() */
3980 if (!(flag & FLAG_DATA))
3981 num_dupack = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
3982 }
3983 tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
3984 &rexmit);
3985 }
3986
3987 /* If needed, reset TLP/RTO timer when RACK doesn't set. */
3988 if (flag & FLAG_SET_XMIT_TIMER)
3989 tcp_set_xmit_timer(sk);
3990
3991 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
3992 sk_dst_confirm(sk);
3993
3994 delivered = tcp_newly_delivered(sk, delivered, flag);
3995 lost = tp->lost - lost; /* freshly marked lost */
3996 rs.is_ack_delayed = !!(flag & FLAG_ACK_MAYBE_DELAYED);
3997 tcp_rate_gen(sk, delivered, lost, is_sack_reneg, sack_state.rate);
3998 tcp_cong_control(sk, ack, delivered, flag, sack_state.rate);
3999 tcp_xmit_recovery(sk, rexmit);
4000 return 1;
4001
4002no_queue:
4003 /* If data was DSACKed, see if we can undo a cwnd reduction. */
4004 if (flag & FLAG_DSACKING_ACK) {
4005 tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
4006 &rexmit);
4007 tcp_newly_delivered(sk, delivered, flag);
4008 }
4009 /* If this ack opens up a zero window, clear backoff. It was
4010 * being used to time the probes, and is probably far higher than
4011 * it needs to be for normal retransmission.
4012 */
4013 tcp_ack_probe(sk);
4014
4015 if (tp->tlp_high_seq)
4016 tcp_process_tlp_ack(sk, ack, flag);
4017 return 1;
4018
4019old_ack:
4020 /* If data was SACKed, tag it and see if we should send more data.
4021 * If data was DSACKed, see if we can undo a cwnd reduction.
4022 */
4023 if (TCP_SKB_CB(skb)->sacked) {
4024 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
4025 &sack_state);
4026 tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
4027 &rexmit);
4028 tcp_newly_delivered(sk, delivered, flag);
4029 tcp_xmit_recovery(sk, rexmit);
4030 }
4031
4032 return 0;
4033}
4034
4035static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
4036 bool syn, struct tcp_fastopen_cookie *foc,
4037 bool exp_opt)
4038{
4039 /* Valid only in SYN or SYN-ACK with an even length. */
4040 if (!foc || !syn || len < 0 || (len & 1))
4041 return;
4042
4043 if (len >= TCP_FASTOPEN_COOKIE_MIN &&
4044 len <= TCP_FASTOPEN_COOKIE_MAX)
4045 memcpy(foc->val, cookie, len);
4046 else if (len != 0)
4047 len = -1;
4048 foc->len = len;
4049 foc->exp = exp_opt;
4050}
4051
4052static bool smc_parse_options(const struct tcphdr *th,
4053 struct tcp_options_received *opt_rx,
4054 const unsigned char *ptr,
4055 int opsize)
4056{
4057#if IS_ENABLED(CONFIG_SMC)
4058 if (static_branch_unlikely(&tcp_have_smc)) {
4059 if (th->syn && !(opsize & 1) &&
4060 opsize >= TCPOLEN_EXP_SMC_BASE &&
4061 get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC) {
4062 opt_rx->smc_ok = 1;
4063 return true;
4064 }
4065 }
4066#endif
4067 return false;
4068}
4069
4070/* Try to parse the MSS option from the TCP header. Return 0 on failure, clamped
4071 * value on success.
4072 */
4073u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss)
4074{
4075 const unsigned char *ptr = (const unsigned char *)(th + 1);
4076 int length = (th->doff * 4) - sizeof(struct tcphdr);
4077 u16 mss = 0;
4078
4079 while (length > 0) {
4080 int opcode = *ptr++;
4081 int opsize;
4082
4083 switch (opcode) {
4084 case TCPOPT_EOL:
4085 return mss;
4086 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
4087 length--;
4088 continue;
4089 default:
4090 if (length < 2)
4091 return mss;
4092 opsize = *ptr++;
4093 if (opsize < 2) /* "silly options" */
4094 return mss;
4095 if (opsize > length)
4096 return mss; /* fail on partial options */
4097 if (opcode == TCPOPT_MSS && opsize == TCPOLEN_MSS) {
4098 u16 in_mss = get_unaligned_be16(ptr);
4099
4100 if (in_mss) {
4101 if (user_mss && user_mss < in_mss)
4102 in_mss = user_mss;
4103 mss = in_mss;
4104 }
4105 }
4106 ptr += opsize - 2;
4107 length -= opsize;
4108 }
4109 }
4110 return mss;
4111}
4112EXPORT_SYMBOL_GPL(tcp_parse_mss_option);
4113
4114/* Look for tcp options. Normally only called on SYN and SYNACK packets.
4115 * But, this can also be called on packets in the established flow when
4116 * the fast version below fails.
4117 */
4118void tcp_parse_options(const struct net *net,
4119 const struct sk_buff *skb,
4120 struct tcp_options_received *opt_rx, int estab,
4121 struct tcp_fastopen_cookie *foc)
4122{
4123 const unsigned char *ptr;
4124 const struct tcphdr *th = tcp_hdr(skb);
4125 int length = (th->doff * 4) - sizeof(struct tcphdr);
4126
4127 ptr = (const unsigned char *)(th + 1);
4128 opt_rx->saw_tstamp = 0;
4129 opt_rx->saw_unknown = 0;
4130
4131 while (length > 0) {
4132 int opcode = *ptr++;
4133 int opsize;
4134
4135 switch (opcode) {
4136 case TCPOPT_EOL:
4137 return;
4138 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
4139 length--;
4140 continue;
4141 default:
4142 if (length < 2)
4143 return;
4144 opsize = *ptr++;
4145 if (opsize < 2) /* "silly options" */
4146 return;
4147 if (opsize > length)
4148 return; /* don't parse partial options */
4149 switch (opcode) {
4150 case TCPOPT_MSS:
4151 if (opsize == TCPOLEN_MSS && th->syn && !estab) {
4152 u16 in_mss = get_unaligned_be16(ptr);
4153 if (in_mss) {
4154 if (opt_rx->user_mss &&
4155 opt_rx->user_mss < in_mss)
4156 in_mss = opt_rx->user_mss;
4157 opt_rx->mss_clamp = in_mss;
4158 }
4159 }
4160 break;
4161 case TCPOPT_WINDOW:
4162 if (opsize == TCPOLEN_WINDOW && th->syn &&
4163 !estab && READ_ONCE(net->ipv4.sysctl_tcp_window_scaling)) {
4164 __u8 snd_wscale = *(__u8 *)ptr;
4165 opt_rx->wscale_ok = 1;
4166 if (snd_wscale > TCP_MAX_WSCALE) {
4167 net_info_ratelimited("%s: Illegal window scaling value %d > %u received\n",
4168 __func__,
4169 snd_wscale,
4170 TCP_MAX_WSCALE);
4171 snd_wscale = TCP_MAX_WSCALE;
4172 }
4173 opt_rx->snd_wscale = snd_wscale;
4174 }
4175 break;
4176 case TCPOPT_TIMESTAMP:
4177 if ((opsize == TCPOLEN_TIMESTAMP) &&
4178 ((estab && opt_rx->tstamp_ok) ||
4179 (!estab && READ_ONCE(net->ipv4.sysctl_tcp_timestamps)))) {
4180 opt_rx->saw_tstamp = 1;
4181 opt_rx->rcv_tsval = get_unaligned_be32(ptr);
4182 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
4183 }
4184 break;
4185 case TCPOPT_SACK_PERM:
4186 if (opsize == TCPOLEN_SACK_PERM && th->syn &&
4187 !estab && READ_ONCE(net->ipv4.sysctl_tcp_sack)) {
4188 opt_rx->sack_ok = TCP_SACK_SEEN;
4189 tcp_sack_reset(opt_rx);
4190 }
4191 break;
4192
4193 case TCPOPT_SACK:
4194 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
4195 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
4196 opt_rx->sack_ok) {
4197 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
4198 }
4199 break;
4200#ifdef CONFIG_TCP_MD5SIG
4201 case TCPOPT_MD5SIG:
4202 /* The MD5 Hash has already been
4203 * checked (see tcp_v{4,6}_rcv()).
4204 */
4205 break;
4206#endif
4207 case TCPOPT_FASTOPEN:
4208 tcp_parse_fastopen_option(
4209 opsize - TCPOLEN_FASTOPEN_BASE,
4210 ptr, th->syn, foc, false);
4211 break;
4212
4213 case TCPOPT_EXP:
4214 /* Fast Open option shares code 254 using a
4215 * 16 bits magic number.
4216 */
4217 if (opsize >= TCPOLEN_EXP_FASTOPEN_BASE &&
4218 get_unaligned_be16(ptr) ==
4219 TCPOPT_FASTOPEN_MAGIC) {
4220 tcp_parse_fastopen_option(opsize -
4221 TCPOLEN_EXP_FASTOPEN_BASE,
4222 ptr + 2, th->syn, foc, true);
4223 break;
4224 }
4225
4226 if (smc_parse_options(th, opt_rx, ptr, opsize))
4227 break;
4228
4229 opt_rx->saw_unknown = 1;
4230 break;
4231
4232 default:
4233 opt_rx->saw_unknown = 1;
4234 }
4235 ptr += opsize-2;
4236 length -= opsize;
4237 }
4238 }
4239}
4240EXPORT_SYMBOL(tcp_parse_options);
4241
4242static bool tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th)
4243{
4244 const __be32 *ptr = (const __be32 *)(th + 1);
4245
4246 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
4247 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
4248 tp->rx_opt.saw_tstamp = 1;
4249 ++ptr;
4250 tp->rx_opt.rcv_tsval = ntohl(*ptr);
4251 ++ptr;
4252 if (*ptr)
4253 tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset;
4254 else
4255 tp->rx_opt.rcv_tsecr = 0;
4256 return true;
4257 }
4258 return false;
4259}
4260
4261/* Fast parse options. This hopes to only see timestamps.
4262 * If it is wrong it falls back on tcp_parse_options().
4263 */
4264static bool tcp_fast_parse_options(const struct net *net,
4265 const struct sk_buff *skb,
4266 const struct tcphdr *th, struct tcp_sock *tp)
4267{
4268 /* In the spirit of fast parsing, compare doff directly to constant
4269 * values. Because equality is used, short doff can be ignored here.
4270 */
4271 if (th->doff == (sizeof(*th) / 4)) {
4272 tp->rx_opt.saw_tstamp = 0;
4273 return false;
4274 } else if (tp->rx_opt.tstamp_ok &&
4275 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
4276 if (tcp_parse_aligned_timestamp(tp, th))
4277 return true;
4278 }
4279
4280 tcp_parse_options(net, skb, &tp->rx_opt, 1, NULL);
4281 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
4282 tp->rx_opt.rcv_tsecr -= tp->tsoffset;
4283
4284 return true;
4285}
4286
4287#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
4288/*
4289 * Parse Signature options
4290 */
4291int tcp_do_parse_auth_options(const struct tcphdr *th,
4292 const u8 **md5_hash, const u8 **ao_hash)
4293{
4294 int length = (th->doff << 2) - sizeof(*th);
4295 const u8 *ptr = (const u8 *)(th + 1);
4296 unsigned int minlen = TCPOLEN_MD5SIG;
4297
4298 if (IS_ENABLED(CONFIG_TCP_AO))
4299 minlen = sizeof(struct tcp_ao_hdr) + 1;
4300
4301 *md5_hash = NULL;
4302 *ao_hash = NULL;
4303
4304 /* If not enough data remaining, we can short cut */
4305 while (length >= minlen) {
4306 int opcode = *ptr++;
4307 int opsize;
4308
4309 switch (opcode) {
4310 case TCPOPT_EOL:
4311 return 0;
4312 case TCPOPT_NOP:
4313 length--;
4314 continue;
4315 default:
4316 opsize = *ptr++;
4317 if (opsize < 2 || opsize > length)
4318 return -EINVAL;
4319 if (opcode == TCPOPT_MD5SIG) {
4320 if (opsize != TCPOLEN_MD5SIG)
4321 return -EINVAL;
4322 if (unlikely(*md5_hash || *ao_hash))
4323 return -EEXIST;
4324 *md5_hash = ptr;
4325 } else if (opcode == TCPOPT_AO) {
4326 if (opsize <= sizeof(struct tcp_ao_hdr))
4327 return -EINVAL;
4328 if (unlikely(*md5_hash || *ao_hash))
4329 return -EEXIST;
4330 *ao_hash = ptr;
4331 }
4332 }
4333 ptr += opsize - 2;
4334 length -= opsize;
4335 }
4336 return 0;
4337}
4338EXPORT_SYMBOL(tcp_do_parse_auth_options);
4339#endif
4340
4341/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
4342 *
4343 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
4344 * it can pass through stack. So, the following predicate verifies that
4345 * this segment is not used for anything but congestion avoidance or
4346 * fast retransmit. Moreover, we even are able to eliminate most of such
4347 * second order effects, if we apply some small "replay" window (~RTO)
4348 * to timestamp space.
4349 *
4350 * All these measures still do not guarantee that we reject wrapped ACKs
4351 * on networks with high bandwidth, when sequence space is recycled fastly,
4352 * but it guarantees that such events will be very rare and do not affect
4353 * connection seriously. This doesn't look nice, but alas, PAWS is really
4354 * buggy extension.
4355 *
4356 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
4357 * states that events when retransmit arrives after original data are rare.
4358 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
4359 * the biggest problem on large power networks even with minor reordering.
4360 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
4361 * up to bandwidth of 18Gigabit/sec. 8) ]
4362 */
4363
4364/* Estimates max number of increments of remote peer TSval in
4365 * a replay window (based on our current RTO estimation).
4366 */
4367static u32 tcp_tsval_replay(const struct sock *sk)
4368{
4369 /* If we use usec TS resolution,
4370 * then expect the remote peer to use the same resolution.
4371 */
4372 if (tcp_sk(sk)->tcp_usec_ts)
4373 return inet_csk(sk)->icsk_rto * (USEC_PER_SEC / HZ);
4374
4375 /* RFC 7323 recommends a TSval clock between 1ms and 1sec.
4376 * We know that some OS (including old linux) can use 1200 Hz.
4377 */
4378 return inet_csk(sk)->icsk_rto * 1200 / HZ;
4379}
4380
4381static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
4382{
4383 const struct tcp_sock *tp = tcp_sk(sk);
4384 const struct tcphdr *th = tcp_hdr(skb);
4385 u32 seq = TCP_SKB_CB(skb)->seq;
4386 u32 ack = TCP_SKB_CB(skb)->ack_seq;
4387
4388 return /* 1. Pure ACK with correct sequence number. */
4389 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
4390
4391 /* 2. ... and duplicate ACK. */
4392 ack == tp->snd_una &&
4393
4394 /* 3. ... and does not update window. */
4395 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
4396
4397 /* 4. ... and sits in replay window. */
4398 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <=
4399 tcp_tsval_replay(sk);
4400}
4401
4402static inline bool tcp_paws_discard(const struct sock *sk,
4403 const struct sk_buff *skb)
4404{
4405 const struct tcp_sock *tp = tcp_sk(sk);
4406
4407 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
4408 !tcp_disordered_ack(sk, skb);
4409}
4410
4411/* Check segment sequence number for validity.
4412 *
4413 * Segment controls are considered valid, if the segment
4414 * fits to the window after truncation to the window. Acceptability
4415 * of data (and SYN, FIN, of course) is checked separately.
4416 * See tcp_data_queue(), for example.
4417 *
4418 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4419 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4420 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4421 * (borrowed from freebsd)
4422 */
4423
4424static enum skb_drop_reason tcp_sequence(const struct tcp_sock *tp,
4425 u32 seq, u32 end_seq)
4426{
4427 if (before(end_seq, tp->rcv_wup))
4428 return SKB_DROP_REASON_TCP_OLD_SEQUENCE;
4429
4430 if (after(seq, tp->rcv_nxt + tcp_receive_window(tp)))
4431 return SKB_DROP_REASON_TCP_INVALID_SEQUENCE;
4432
4433 return SKB_NOT_DROPPED_YET;
4434}
4435
4436/* When we get a reset we do this. */
4437void tcp_reset(struct sock *sk, struct sk_buff *skb)
4438{
4439 trace_tcp_receive_reset(sk);
4440
4441 /* mptcp can't tell us to ignore reset pkts,
4442 * so just ignore the return value of mptcp_incoming_options().
4443 */
4444 if (sk_is_mptcp(sk))
4445 mptcp_incoming_options(sk, skb);
4446
4447 /* We want the right error as BSD sees it (and indeed as we do). */
4448 switch (sk->sk_state) {
4449 case TCP_SYN_SENT:
4450 WRITE_ONCE(sk->sk_err, ECONNREFUSED);
4451 break;
4452 case TCP_CLOSE_WAIT:
4453 WRITE_ONCE(sk->sk_err, EPIPE);
4454 break;
4455 case TCP_CLOSE:
4456 return;
4457 default:
4458 WRITE_ONCE(sk->sk_err, ECONNRESET);
4459 }
4460 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4461 smp_wmb();
4462
4463 tcp_write_queue_purge(sk);
4464 tcp_done(sk);
4465
4466 if (!sock_flag(sk, SOCK_DEAD))
4467 sk_error_report(sk);
4468}
4469
4470/*
4471 * Process the FIN bit. This now behaves as it is supposed to work
4472 * and the FIN takes effect when it is validly part of sequence
4473 * space. Not before when we get holes.
4474 *
4475 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4476 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4477 * TIME-WAIT)
4478 *
4479 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4480 * close and we go into CLOSING (and later onto TIME-WAIT)
4481 *
4482 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4483 */
4484void tcp_fin(struct sock *sk)
4485{
4486 struct tcp_sock *tp = tcp_sk(sk);
4487
4488 inet_csk_schedule_ack(sk);
4489
4490 WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | RCV_SHUTDOWN);
4491 sock_set_flag(sk, SOCK_DONE);
4492
4493 switch (sk->sk_state) {
4494 case TCP_SYN_RECV:
4495 case TCP_ESTABLISHED:
4496 /* Move to CLOSE_WAIT */
4497 tcp_set_state(sk, TCP_CLOSE_WAIT);
4498 inet_csk_enter_pingpong_mode(sk);
4499 break;
4500
4501 case TCP_CLOSE_WAIT:
4502 case TCP_CLOSING:
4503 /* Received a retransmission of the FIN, do
4504 * nothing.
4505 */
4506 break;
4507 case TCP_LAST_ACK:
4508 /* RFC793: Remain in the LAST-ACK state. */
4509 break;
4510
4511 case TCP_FIN_WAIT1:
4512 /* This case occurs when a simultaneous close
4513 * happens, we must ack the received FIN and
4514 * enter the CLOSING state.
4515 */
4516 tcp_send_ack(sk);
4517 tcp_set_state(sk, TCP_CLOSING);
4518 break;
4519 case TCP_FIN_WAIT2:
4520 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4521 tcp_send_ack(sk);
4522 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4523 break;
4524 default:
4525 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4526 * cases we should never reach this piece of code.
4527 */
4528 pr_err("%s: Impossible, sk->sk_state=%d\n",
4529 __func__, sk->sk_state);
4530 break;
4531 }
4532
4533 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4534 * Probably, we should reset in this case. For now drop them.
4535 */
4536 skb_rbtree_purge(&tp->out_of_order_queue);
4537 if (tcp_is_sack(tp))
4538 tcp_sack_reset(&tp->rx_opt);
4539
4540 if (!sock_flag(sk, SOCK_DEAD)) {
4541 sk->sk_state_change(sk);
4542
4543 /* Do not send POLL_HUP for half duplex close. */
4544 if (sk->sk_shutdown == SHUTDOWN_MASK ||
4545 sk->sk_state == TCP_CLOSE)
4546 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
4547 else
4548 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
4549 }
4550}
4551
4552static inline bool tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
4553 u32 end_seq)
4554{
4555 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
4556 if (before(seq, sp->start_seq))
4557 sp->start_seq = seq;
4558 if (after(end_seq, sp->end_seq))
4559 sp->end_seq = end_seq;
4560 return true;
4561 }
4562 return false;
4563}
4564
4565static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
4566{
4567 struct tcp_sock *tp = tcp_sk(sk);
4568
4569 if (tcp_is_sack(tp) && READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_dsack)) {
4570 int mib_idx;
4571
4572 if (before(seq, tp->rcv_nxt))
4573 mib_idx = LINUX_MIB_TCPDSACKOLDSENT;
4574 else
4575 mib_idx = LINUX_MIB_TCPDSACKOFOSENT;
4576
4577 NET_INC_STATS(sock_net(sk), mib_idx);
4578
4579 tp->rx_opt.dsack = 1;
4580 tp->duplicate_sack[0].start_seq = seq;
4581 tp->duplicate_sack[0].end_seq = end_seq;
4582 }
4583}
4584
4585static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
4586{
4587 struct tcp_sock *tp = tcp_sk(sk);
4588
4589 if (!tp->rx_opt.dsack)
4590 tcp_dsack_set(sk, seq, end_seq);
4591 else
4592 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
4593}
4594
4595static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb)
4596{
4597 /* When the ACK path fails or drops most ACKs, the sender would
4598 * timeout and spuriously retransmit the same segment repeatedly.
4599 * If it seems our ACKs are not reaching the other side,
4600 * based on receiving a duplicate data segment with new flowlabel
4601 * (suggesting the sender suffered an RTO), and we are not already
4602 * repathing due to our own RTO, then rehash the socket to repath our
4603 * packets.
4604 */
4605#if IS_ENABLED(CONFIG_IPV6)
4606 if (inet_csk(sk)->icsk_ca_state != TCP_CA_Loss &&
4607 skb->protocol == htons(ETH_P_IPV6) &&
4608 (tcp_sk(sk)->inet_conn.icsk_ack.lrcv_flowlabel !=
4609 ntohl(ip6_flowlabel(ipv6_hdr(skb)))) &&
4610 sk_rethink_txhash(sk))
4611 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDUPLICATEDATAREHASH);
4612
4613 /* Save last flowlabel after a spurious retrans. */
4614 tcp_save_lrcv_flowlabel(sk, skb);
4615#endif
4616}
4617
4618static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
4619{
4620 struct tcp_sock *tp = tcp_sk(sk);
4621
4622 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4623 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4624 NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4625 tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
4626
4627 if (tcp_is_sack(tp) && READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_dsack)) {
4628 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4629
4630 tcp_rcv_spurious_retrans(sk, skb);
4631 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
4632 end_seq = tp->rcv_nxt;
4633 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
4634 }
4635 }
4636
4637 tcp_send_ack(sk);
4638}
4639
4640/* These routines update the SACK block as out-of-order packets arrive or
4641 * in-order packets close up the sequence space.
4642 */
4643static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
4644{
4645 int this_sack;
4646 struct tcp_sack_block *sp = &tp->selective_acks[0];
4647 struct tcp_sack_block *swalk = sp + 1;
4648
4649 /* See if the recent change to the first SACK eats into
4650 * or hits the sequence space of other SACK blocks, if so coalesce.
4651 */
4652 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
4653 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
4654 int i;
4655
4656 /* Zap SWALK, by moving every further SACK up by one slot.
4657 * Decrease num_sacks.
4658 */
4659 tp->rx_opt.num_sacks--;
4660 for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
4661 sp[i] = sp[i + 1];
4662 continue;
4663 }
4664 this_sack++;
4665 swalk++;
4666 }
4667}
4668
4669void tcp_sack_compress_send_ack(struct sock *sk)
4670{
4671 struct tcp_sock *tp = tcp_sk(sk);
4672
4673 if (!tp->compressed_ack)
4674 return;
4675
4676 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
4677 __sock_put(sk);
4678
4679 /* Since we have to send one ack finally,
4680 * substract one from tp->compressed_ack to keep
4681 * LINUX_MIB_TCPACKCOMPRESSED accurate.
4682 */
4683 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
4684 tp->compressed_ack - 1);
4685
4686 tp->compressed_ack = 0;
4687 tcp_send_ack(sk);
4688}
4689
4690/* Reasonable amount of sack blocks included in TCP SACK option
4691 * The max is 4, but this becomes 3 if TCP timestamps are there.
4692 * Given that SACK packets might be lost, be conservative and use 2.
4693 */
4694#define TCP_SACK_BLOCKS_EXPECTED 2
4695
4696static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
4697{
4698 struct tcp_sock *tp = tcp_sk(sk);
4699 struct tcp_sack_block *sp = &tp->selective_acks[0];
4700 int cur_sacks = tp->rx_opt.num_sacks;
4701 int this_sack;
4702
4703 if (!cur_sacks)
4704 goto new_sack;
4705
4706 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
4707 if (tcp_sack_extend(sp, seq, end_seq)) {
4708 if (this_sack >= TCP_SACK_BLOCKS_EXPECTED)
4709 tcp_sack_compress_send_ack(sk);
4710 /* Rotate this_sack to the first one. */
4711 for (; this_sack > 0; this_sack--, sp--)
4712 swap(*sp, *(sp - 1));
4713 if (cur_sacks > 1)
4714 tcp_sack_maybe_coalesce(tp);
4715 return;
4716 }
4717 }
4718
4719 if (this_sack >= TCP_SACK_BLOCKS_EXPECTED)
4720 tcp_sack_compress_send_ack(sk);
4721
4722 /* Could not find an adjacent existing SACK, build a new one,
4723 * put it at the front, and shift everyone else down. We
4724 * always know there is at least one SACK present already here.
4725 *
4726 * If the sack array is full, forget about the last one.
4727 */
4728 if (this_sack >= TCP_NUM_SACKS) {
4729 this_sack--;
4730 tp->rx_opt.num_sacks--;
4731 sp--;
4732 }
4733 for (; this_sack > 0; this_sack--, sp--)
4734 *sp = *(sp - 1);
4735
4736new_sack:
4737 /* Build the new head SACK, and we're done. */
4738 sp->start_seq = seq;
4739 sp->end_seq = end_seq;
4740 tp->rx_opt.num_sacks++;
4741}
4742
4743/* RCV.NXT advances, some SACKs should be eaten. */
4744
4745static void tcp_sack_remove(struct tcp_sock *tp)
4746{
4747 struct tcp_sack_block *sp = &tp->selective_acks[0];
4748 int num_sacks = tp->rx_opt.num_sacks;
4749 int this_sack;
4750
4751 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4752 if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
4753 tp->rx_opt.num_sacks = 0;
4754 return;
4755 }
4756
4757 for (this_sack = 0; this_sack < num_sacks;) {
4758 /* Check if the start of the sack is covered by RCV.NXT. */
4759 if (!before(tp->rcv_nxt, sp->start_seq)) {
4760 int i;
4761
4762 /* RCV.NXT must cover all the block! */
4763 WARN_ON(before(tp->rcv_nxt, sp->end_seq));
4764
4765 /* Zap this SACK, by moving forward any other SACKS. */
4766 for (i = this_sack+1; i < num_sacks; i++)
4767 tp->selective_acks[i-1] = tp->selective_acks[i];
4768 num_sacks--;
4769 continue;
4770 }
4771 this_sack++;
4772 sp++;
4773 }
4774 tp->rx_opt.num_sacks = num_sacks;
4775}
4776
4777/**
4778 * tcp_try_coalesce - try to merge skb to prior one
4779 * @sk: socket
4780 * @to: prior buffer
4781 * @from: buffer to add in queue
4782 * @fragstolen: pointer to boolean
4783 *
4784 * Before queueing skb @from after @to, try to merge them
4785 * to reduce overall memory use and queue lengths, if cost is small.
4786 * Packets in ofo or receive queues can stay a long time.
4787 * Better try to coalesce them right now to avoid future collapses.
4788 * Returns true if caller should free @from instead of queueing it
4789 */
4790static bool tcp_try_coalesce(struct sock *sk,
4791 struct sk_buff *to,
4792 struct sk_buff *from,
4793 bool *fragstolen)
4794{
4795 int delta;
4796
4797 *fragstolen = false;
4798
4799 /* Its possible this segment overlaps with prior segment in queue */
4800 if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq)
4801 return false;
4802
4803 if (!mptcp_skb_can_collapse(to, from))
4804 return false;
4805
4806#ifdef CONFIG_TLS_DEVICE
4807 if (from->decrypted != to->decrypted)
4808 return false;
4809#endif
4810
4811 if (!skb_try_coalesce(to, from, fragstolen, &delta))
4812 return false;
4813
4814 atomic_add(delta, &sk->sk_rmem_alloc);
4815 sk_mem_charge(sk, delta);
4816 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE);
4817 TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq;
4818 TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq;
4819 TCP_SKB_CB(to)->tcp_flags |= TCP_SKB_CB(from)->tcp_flags;
4820
4821 if (TCP_SKB_CB(from)->has_rxtstamp) {
4822 TCP_SKB_CB(to)->has_rxtstamp = true;
4823 to->tstamp = from->tstamp;
4824 skb_hwtstamps(to)->hwtstamp = skb_hwtstamps(from)->hwtstamp;
4825 }
4826
4827 return true;
4828}
4829
4830static bool tcp_ooo_try_coalesce(struct sock *sk,
4831 struct sk_buff *to,
4832 struct sk_buff *from,
4833 bool *fragstolen)
4834{
4835 bool res = tcp_try_coalesce(sk, to, from, fragstolen);
4836
4837 /* In case tcp_drop_reason() is called later, update to->gso_segs */
4838 if (res) {
4839 u32 gso_segs = max_t(u16, 1, skb_shinfo(to)->gso_segs) +
4840 max_t(u16, 1, skb_shinfo(from)->gso_segs);
4841
4842 skb_shinfo(to)->gso_segs = min_t(u32, gso_segs, 0xFFFF);
4843 }
4844 return res;
4845}
4846
4847static void tcp_drop_reason(struct sock *sk, struct sk_buff *skb,
4848 enum skb_drop_reason reason)
4849{
4850 sk_drops_add(sk, skb);
4851 kfree_skb_reason(skb, reason);
4852}
4853
4854/* This one checks to see if we can put data from the
4855 * out_of_order queue into the receive_queue.
4856 */
4857static void tcp_ofo_queue(struct sock *sk)
4858{
4859 struct tcp_sock *tp = tcp_sk(sk);
4860 __u32 dsack_high = tp->rcv_nxt;
4861 bool fin, fragstolen, eaten;
4862 struct sk_buff *skb, *tail;
4863 struct rb_node *p;
4864
4865 p = rb_first(&tp->out_of_order_queue);
4866 while (p) {
4867 skb = rb_to_skb(p);
4868 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4869 break;
4870
4871 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
4872 __u32 dsack = dsack_high;
4873 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
4874 dsack_high = TCP_SKB_CB(skb)->end_seq;
4875 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack);
4876 }
4877 p = rb_next(p);
4878 rb_erase(&skb->rbnode, &tp->out_of_order_queue);
4879
4880 if (unlikely(!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))) {
4881 tcp_drop_reason(sk, skb, SKB_DROP_REASON_TCP_OFO_DROP);
4882 continue;
4883 }
4884
4885 tail = skb_peek_tail(&sk->sk_receive_queue);
4886 eaten = tail && tcp_try_coalesce(sk, tail, skb, &fragstolen);
4887 tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
4888 fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
4889 if (!eaten)
4890 __skb_queue_tail(&sk->sk_receive_queue, skb);
4891 else
4892 kfree_skb_partial(skb, fragstolen);
4893
4894 if (unlikely(fin)) {
4895 tcp_fin(sk);
4896 /* tcp_fin() purges tp->out_of_order_queue,
4897 * so we must end this loop right now.
4898 */
4899 break;
4900 }
4901 }
4902}
4903
4904static bool tcp_prune_ofo_queue(struct sock *sk, const struct sk_buff *in_skb);
4905static int tcp_prune_queue(struct sock *sk, const struct sk_buff *in_skb);
4906
4907static int tcp_try_rmem_schedule(struct sock *sk, struct sk_buff *skb,
4908 unsigned int size)
4909{
4910 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
4911 !sk_rmem_schedule(sk, skb, size)) {
4912
4913 if (tcp_prune_queue(sk, skb) < 0)
4914 return -1;
4915
4916 while (!sk_rmem_schedule(sk, skb, size)) {
4917 if (!tcp_prune_ofo_queue(sk, skb))
4918 return -1;
4919 }
4920 }
4921 return 0;
4922}
4923
4924static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
4925{
4926 struct tcp_sock *tp = tcp_sk(sk);
4927 struct rb_node **p, *parent;
4928 struct sk_buff *skb1;
4929 u32 seq, end_seq;
4930 bool fragstolen;
4931
4932 tcp_save_lrcv_flowlabel(sk, skb);
4933 tcp_ecn_check_ce(sk, skb);
4934
4935 if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
4936 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFODROP);
4937 sk->sk_data_ready(sk);
4938 tcp_drop_reason(sk, skb, SKB_DROP_REASON_PROTO_MEM);
4939 return;
4940 }
4941
4942 /* Disable header prediction. */
4943 tp->pred_flags = 0;
4944 inet_csk_schedule_ack(sk);
4945
4946 tp->rcv_ooopack += max_t(u16, 1, skb_shinfo(skb)->gso_segs);
4947 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
4948 seq = TCP_SKB_CB(skb)->seq;
4949 end_seq = TCP_SKB_CB(skb)->end_seq;
4950
4951 p = &tp->out_of_order_queue.rb_node;
4952 if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
4953 /* Initial out of order segment, build 1 SACK. */
4954 if (tcp_is_sack(tp)) {
4955 tp->rx_opt.num_sacks = 1;
4956 tp->selective_acks[0].start_seq = seq;
4957 tp->selective_acks[0].end_seq = end_seq;
4958 }
4959 rb_link_node(&skb->rbnode, NULL, p);
4960 rb_insert_color(&skb->rbnode, &tp->out_of_order_queue);
4961 tp->ooo_last_skb = skb;
4962 goto end;
4963 }
4964
4965 /* In the typical case, we are adding an skb to the end of the list.
4966 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
4967 */
4968 if (tcp_ooo_try_coalesce(sk, tp->ooo_last_skb,
4969 skb, &fragstolen)) {
4970coalesce_done:
4971 /* For non sack flows, do not grow window to force DUPACK
4972 * and trigger fast retransmit.
4973 */
4974 if (tcp_is_sack(tp))
4975 tcp_grow_window(sk, skb, true);
4976 kfree_skb_partial(skb, fragstolen);
4977 skb = NULL;
4978 goto add_sack;
4979 }
4980 /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
4981 if (!before(seq, TCP_SKB_CB(tp->ooo_last_skb)->end_seq)) {
4982 parent = &tp->ooo_last_skb->rbnode;
4983 p = &parent->rb_right;
4984 goto insert;
4985 }
4986
4987 /* Find place to insert this segment. Handle overlaps on the way. */
4988 parent = NULL;
4989 while (*p) {
4990 parent = *p;
4991 skb1 = rb_to_skb(parent);
4992 if (before(seq, TCP_SKB_CB(skb1)->seq)) {
4993 p = &parent->rb_left;
4994 continue;
4995 }
4996 if (before(seq, TCP_SKB_CB(skb1)->end_seq)) {
4997 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4998 /* All the bits are present. Drop. */
4999 NET_INC_STATS(sock_net(sk),
5000 LINUX_MIB_TCPOFOMERGE);
5001 tcp_drop_reason(sk, skb,
5002 SKB_DROP_REASON_TCP_OFOMERGE);
5003 skb = NULL;
5004 tcp_dsack_set(sk, seq, end_seq);
5005 goto add_sack;
5006 }
5007 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
5008 /* Partial overlap. */
5009 tcp_dsack_set(sk, seq, TCP_SKB_CB(skb1)->end_seq);
5010 } else {
5011 /* skb's seq == skb1's seq and skb covers skb1.
5012 * Replace skb1 with skb.
5013 */
5014 rb_replace_node(&skb1->rbnode, &skb->rbnode,
5015 &tp->out_of_order_queue);
5016 tcp_dsack_extend(sk,
5017 TCP_SKB_CB(skb1)->seq,
5018 TCP_SKB_CB(skb1)->end_seq);
5019 NET_INC_STATS(sock_net(sk),
5020 LINUX_MIB_TCPOFOMERGE);
5021 tcp_drop_reason(sk, skb1,
5022 SKB_DROP_REASON_TCP_OFOMERGE);
5023 goto merge_right;
5024 }
5025 } else if (tcp_ooo_try_coalesce(sk, skb1,
5026 skb, &fragstolen)) {
5027 goto coalesce_done;
5028 }
5029 p = &parent->rb_right;
5030 }
5031insert:
5032 /* Insert segment into RB tree. */
5033 rb_link_node(&skb->rbnode, parent, p);
5034 rb_insert_color(&skb->rbnode, &tp->out_of_order_queue);
5035
5036merge_right:
5037 /* Remove other segments covered by skb. */
5038 while ((skb1 = skb_rb_next(skb)) != NULL) {
5039 if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
5040 break;
5041 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
5042 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
5043 end_seq);
5044 break;
5045 }
5046 rb_erase(&skb1->rbnode, &tp->out_of_order_queue);
5047 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
5048 TCP_SKB_CB(skb1)->end_seq);
5049 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
5050 tcp_drop_reason(sk, skb1, SKB_DROP_REASON_TCP_OFOMERGE);
5051 }
5052 /* If there is no skb after us, we are the last_skb ! */
5053 if (!skb1)
5054 tp->ooo_last_skb = skb;
5055
5056add_sack:
5057 if (tcp_is_sack(tp))
5058 tcp_sack_new_ofo_skb(sk, seq, end_seq);
5059end:
5060 if (skb) {
5061 /* For non sack flows, do not grow window to force DUPACK
5062 * and trigger fast retransmit.
5063 */
5064 if (tcp_is_sack(tp))
5065 tcp_grow_window(sk, skb, false);
5066 skb_condense(skb);
5067 skb_set_owner_r(skb, sk);
5068 }
5069}
5070
5071static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb,
5072 bool *fragstolen)
5073{
5074 int eaten;
5075 struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
5076
5077 eaten = (tail &&
5078 tcp_try_coalesce(sk, tail,
5079 skb, fragstolen)) ? 1 : 0;
5080 tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
5081 if (!eaten) {
5082 __skb_queue_tail(&sk->sk_receive_queue, skb);
5083 skb_set_owner_r(skb, sk);
5084 }
5085 return eaten;
5086}
5087
5088int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
5089{
5090 struct sk_buff *skb;
5091 int err = -ENOMEM;
5092 int data_len = 0;
5093 bool fragstolen;
5094
5095 if (size == 0)
5096 return 0;
5097
5098 if (size > PAGE_SIZE) {
5099 int npages = min_t(size_t, size >> PAGE_SHIFT, MAX_SKB_FRAGS);
5100
5101 data_len = npages << PAGE_SHIFT;
5102 size = data_len + (size & ~PAGE_MASK);
5103 }
5104 skb = alloc_skb_with_frags(size - data_len, data_len,
5105 PAGE_ALLOC_COSTLY_ORDER,
5106 &err, sk->sk_allocation);
5107 if (!skb)
5108 goto err;
5109
5110 skb_put(skb, size - data_len);
5111 skb->data_len = data_len;
5112 skb->len = size;
5113
5114 if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) {
5115 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP);
5116 goto err_free;
5117 }
5118
5119 err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size);
5120 if (err)
5121 goto err_free;
5122
5123 TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;
5124 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size;
5125 TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1;
5126
5127 if (tcp_queue_rcv(sk, skb, &fragstolen)) {
5128 WARN_ON_ONCE(fragstolen); /* should not happen */
5129 __kfree_skb(skb);
5130 }
5131 return size;
5132
5133err_free:
5134 kfree_skb(skb);
5135err:
5136 return err;
5137
5138}
5139
5140void tcp_data_ready(struct sock *sk)
5141{
5142 if (tcp_epollin_ready(sk, sk->sk_rcvlowat) || sock_flag(sk, SOCK_DONE))
5143 sk->sk_data_ready(sk);
5144}
5145
5146static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
5147{
5148 struct tcp_sock *tp = tcp_sk(sk);
5149 enum skb_drop_reason reason;
5150 bool fragstolen;
5151 int eaten;
5152
5153 /* If a subflow has been reset, the packet should not continue
5154 * to be processed, drop the packet.
5155 */
5156 if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb)) {
5157 __kfree_skb(skb);
5158 return;
5159 }
5160
5161 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
5162 __kfree_skb(skb);
5163 return;
5164 }
5165 skb_dst_drop(skb);
5166 __skb_pull(skb, tcp_hdr(skb)->doff * 4);
5167
5168 reason = SKB_DROP_REASON_NOT_SPECIFIED;
5169 tp->rx_opt.dsack = 0;
5170
5171 /* Queue data for delivery to the user.
5172 * Packets in sequence go to the receive queue.
5173 * Out of sequence packets to the out_of_order_queue.
5174 */
5175 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
5176 if (tcp_receive_window(tp) == 0) {
5177 reason = SKB_DROP_REASON_TCP_ZEROWINDOW;
5178 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP);
5179 goto out_of_window;
5180 }
5181
5182 /* Ok. In sequence. In window. */
5183queue_and_out:
5184 if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) {
5185 /* TODO: maybe ratelimit these WIN 0 ACK ? */
5186 inet_csk(sk)->icsk_ack.pending |=
5187 (ICSK_ACK_NOMEM | ICSK_ACK_NOW);
5188 inet_csk_schedule_ack(sk);
5189 sk->sk_data_ready(sk);
5190
5191 if (skb_queue_len(&sk->sk_receive_queue)) {
5192 reason = SKB_DROP_REASON_PROTO_MEM;
5193 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP);
5194 goto drop;
5195 }
5196 sk_forced_mem_schedule(sk, skb->truesize);
5197 }
5198
5199 eaten = tcp_queue_rcv(sk, skb, &fragstolen);
5200 if (skb->len)
5201 tcp_event_data_recv(sk, skb);
5202 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
5203 tcp_fin(sk);
5204
5205 if (!RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
5206 tcp_ofo_queue(sk);
5207
5208 /* RFC5681. 4.2. SHOULD send immediate ACK, when
5209 * gap in queue is filled.
5210 */
5211 if (RB_EMPTY_ROOT(&tp->out_of_order_queue))
5212 inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
5213 }
5214
5215 if (tp->rx_opt.num_sacks)
5216 tcp_sack_remove(tp);
5217
5218 tcp_fast_path_check(sk);
5219
5220 if (eaten > 0)
5221 kfree_skb_partial(skb, fragstolen);
5222 if (!sock_flag(sk, SOCK_DEAD))
5223 tcp_data_ready(sk);
5224 return;
5225 }
5226
5227 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
5228 tcp_rcv_spurious_retrans(sk, skb);
5229 /* A retransmit, 2nd most common case. Force an immediate ack. */
5230 reason = SKB_DROP_REASON_TCP_OLD_DATA;
5231 NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
5232 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
5233
5234out_of_window:
5235 tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
5236 inet_csk_schedule_ack(sk);
5237drop:
5238 tcp_drop_reason(sk, skb, reason);
5239 return;
5240 }
5241
5242 /* Out of window. F.e. zero window probe. */
5243 if (!before(TCP_SKB_CB(skb)->seq,
5244 tp->rcv_nxt + tcp_receive_window(tp))) {
5245 reason = SKB_DROP_REASON_TCP_OVERWINDOW;
5246 goto out_of_window;
5247 }
5248
5249 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
5250 /* Partial packet, seq < rcv_next < end_seq */
5251 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
5252
5253 /* If window is closed, drop tail of packet. But after
5254 * remembering D-SACK for its head made in previous line.
5255 */
5256 if (!tcp_receive_window(tp)) {
5257 reason = SKB_DROP_REASON_TCP_ZEROWINDOW;
5258 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP);
5259 goto out_of_window;
5260 }
5261 goto queue_and_out;
5262 }
5263
5264 tcp_data_queue_ofo(sk, skb);
5265}
5266
5267static struct sk_buff *tcp_skb_next(struct sk_buff *skb, struct sk_buff_head *list)
5268{
5269 if (list)
5270 return !skb_queue_is_last(list, skb) ? skb->next : NULL;
5271
5272 return skb_rb_next(skb);
5273}
5274
5275static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
5276 struct sk_buff_head *list,
5277 struct rb_root *root)
5278{
5279 struct sk_buff *next = tcp_skb_next(skb, list);
5280
5281 if (list)
5282 __skb_unlink(skb, list);
5283 else
5284 rb_erase(&skb->rbnode, root);
5285
5286 __kfree_skb(skb);
5287 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
5288
5289 return next;
5290}
5291
5292/* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */
5293void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
5294{
5295 struct rb_node **p = &root->rb_node;
5296 struct rb_node *parent = NULL;
5297 struct sk_buff *skb1;
5298
5299 while (*p) {
5300 parent = *p;
5301 skb1 = rb_to_skb(parent);
5302 if (before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb1)->seq))
5303 p = &parent->rb_left;
5304 else
5305 p = &parent->rb_right;
5306 }
5307 rb_link_node(&skb->rbnode, parent, p);
5308 rb_insert_color(&skb->rbnode, root);
5309}
5310
5311/* Collapse contiguous sequence of skbs head..tail with
5312 * sequence numbers start..end.
5313 *
5314 * If tail is NULL, this means until the end of the queue.
5315 *
5316 * Segments with FIN/SYN are not collapsed (only because this
5317 * simplifies code)
5318 */
5319static void
5320tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root,
5321 struct sk_buff *head, struct sk_buff *tail, u32 start, u32 end)
5322{
5323 struct sk_buff *skb = head, *n;
5324 struct sk_buff_head tmp;
5325 bool end_of_skbs;
5326
5327 /* First, check that queue is collapsible and find
5328 * the point where collapsing can be useful.
5329 */
5330restart:
5331 for (end_of_skbs = true; skb != NULL && skb != tail; skb = n) {
5332 n = tcp_skb_next(skb, list);
5333
5334 /* No new bits? It is possible on ofo queue. */
5335 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
5336 skb = tcp_collapse_one(sk, skb, list, root);
5337 if (!skb)
5338 break;
5339 goto restart;
5340 }
5341
5342 /* The first skb to collapse is:
5343 * - not SYN/FIN and
5344 * - bloated or contains data before "start" or
5345 * overlaps to the next one and mptcp allow collapsing.
5346 */
5347 if (!(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) &&
5348 (tcp_win_from_space(sk, skb->truesize) > skb->len ||
5349 before(TCP_SKB_CB(skb)->seq, start))) {
5350 end_of_skbs = false;
5351 break;
5352 }
5353
5354 if (n && n != tail && mptcp_skb_can_collapse(skb, n) &&
5355 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(n)->seq) {
5356 end_of_skbs = false;
5357 break;
5358 }
5359
5360 /* Decided to skip this, advance start seq. */
5361 start = TCP_SKB_CB(skb)->end_seq;
5362 }
5363 if (end_of_skbs ||
5364 (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
5365 return;
5366
5367 __skb_queue_head_init(&tmp);
5368
5369 while (before(start, end)) {
5370 int copy = min_t(int, SKB_MAX_ORDER(0, 0), end - start);
5371 struct sk_buff *nskb;
5372
5373 nskb = alloc_skb(copy, GFP_ATOMIC);
5374 if (!nskb)
5375 break;
5376
5377 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
5378#ifdef CONFIG_TLS_DEVICE
5379 nskb->decrypted = skb->decrypted;
5380#endif
5381 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
5382 if (list)
5383 __skb_queue_before(list, skb, nskb);
5384 else
5385 __skb_queue_tail(&tmp, nskb); /* defer rbtree insertion */
5386 skb_set_owner_r(nskb, sk);
5387 mptcp_skb_ext_move(nskb, skb);
5388
5389 /* Copy data, releasing collapsed skbs. */
5390 while (copy > 0) {
5391 int offset = start - TCP_SKB_CB(skb)->seq;
5392 int size = TCP_SKB_CB(skb)->end_seq - start;
5393
5394 BUG_ON(offset < 0);
5395 if (size > 0) {
5396 size = min(copy, size);
5397 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
5398 BUG();
5399 TCP_SKB_CB(nskb)->end_seq += size;
5400 copy -= size;
5401 start += size;
5402 }
5403 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
5404 skb = tcp_collapse_one(sk, skb, list, root);
5405 if (!skb ||
5406 skb == tail ||
5407 !mptcp_skb_can_collapse(nskb, skb) ||
5408 (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
5409 goto end;
5410#ifdef CONFIG_TLS_DEVICE
5411 if (skb->decrypted != nskb->decrypted)
5412 goto end;
5413#endif
5414 }
5415 }
5416 }
5417end:
5418 skb_queue_walk_safe(&tmp, skb, n)
5419 tcp_rbtree_insert(root, skb);
5420}
5421
5422/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
5423 * and tcp_collapse() them until all the queue is collapsed.
5424 */
5425static void tcp_collapse_ofo_queue(struct sock *sk)
5426{
5427 struct tcp_sock *tp = tcp_sk(sk);
5428 u32 range_truesize, sum_tiny = 0;
5429 struct sk_buff *skb, *head;
5430 u32 start, end;
5431
5432 skb = skb_rb_first(&tp->out_of_order_queue);
5433new_range:
5434 if (!skb) {
5435 tp->ooo_last_skb = skb_rb_last(&tp->out_of_order_queue);
5436 return;
5437 }
5438 start = TCP_SKB_CB(skb)->seq;
5439 end = TCP_SKB_CB(skb)->end_seq;
5440 range_truesize = skb->truesize;
5441
5442 for (head = skb;;) {
5443 skb = skb_rb_next(skb);
5444
5445 /* Range is terminated when we see a gap or when
5446 * we are at the queue end.
5447 */
5448 if (!skb ||
5449 after(TCP_SKB_CB(skb)->seq, end) ||
5450 before(TCP_SKB_CB(skb)->end_seq, start)) {
5451 /* Do not attempt collapsing tiny skbs */
5452 if (range_truesize != head->truesize ||
5453 end - start >= SKB_WITH_OVERHEAD(PAGE_SIZE)) {
5454 tcp_collapse(sk, NULL, &tp->out_of_order_queue,
5455 head, skb, start, end);
5456 } else {
5457 sum_tiny += range_truesize;
5458 if (sum_tiny > sk->sk_rcvbuf >> 3)
5459 return;
5460 }
5461 goto new_range;
5462 }
5463
5464 range_truesize += skb->truesize;
5465 if (unlikely(before(TCP_SKB_CB(skb)->seq, start)))
5466 start = TCP_SKB_CB(skb)->seq;
5467 if (after(TCP_SKB_CB(skb)->end_seq, end))
5468 end = TCP_SKB_CB(skb)->end_seq;
5469 }
5470}
5471
5472/*
5473 * Clean the out-of-order queue to make room.
5474 * We drop high sequences packets to :
5475 * 1) Let a chance for holes to be filled.
5476 * This means we do not drop packets from ooo queue if their sequence
5477 * is before incoming packet sequence.
5478 * 2) not add too big latencies if thousands of packets sit there.
5479 * (But if application shrinks SO_RCVBUF, we could still end up
5480 * freeing whole queue here)
5481 * 3) Drop at least 12.5 % of sk_rcvbuf to avoid malicious attacks.
5482 *
5483 * Return true if queue has shrunk.
5484 */
5485static bool tcp_prune_ofo_queue(struct sock *sk, const struct sk_buff *in_skb)
5486{
5487 struct tcp_sock *tp = tcp_sk(sk);
5488 struct rb_node *node, *prev;
5489 bool pruned = false;
5490 int goal;
5491
5492 if (RB_EMPTY_ROOT(&tp->out_of_order_queue))
5493 return false;
5494
5495 goal = sk->sk_rcvbuf >> 3;
5496 node = &tp->ooo_last_skb->rbnode;
5497
5498 do {
5499 struct sk_buff *skb = rb_to_skb(node);
5500
5501 /* If incoming skb would land last in ofo queue, stop pruning. */
5502 if (after(TCP_SKB_CB(in_skb)->seq, TCP_SKB_CB(skb)->seq))
5503 break;
5504 pruned = true;
5505 prev = rb_prev(node);
5506 rb_erase(node, &tp->out_of_order_queue);
5507 goal -= skb->truesize;
5508 tcp_drop_reason(sk, skb, SKB_DROP_REASON_TCP_OFO_QUEUE_PRUNE);
5509 tp->ooo_last_skb = rb_to_skb(prev);
5510 if (!prev || goal <= 0) {
5511 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
5512 !tcp_under_memory_pressure(sk))
5513 break;
5514 goal = sk->sk_rcvbuf >> 3;
5515 }
5516 node = prev;
5517 } while (node);
5518
5519 if (pruned) {
5520 NET_INC_STATS(sock_net(sk), LINUX_MIB_OFOPRUNED);
5521 /* Reset SACK state. A conforming SACK implementation will
5522 * do the same at a timeout based retransmit. When a connection
5523 * is in a sad state like this, we care only about integrity
5524 * of the connection not performance.
5525 */
5526 if (tp->rx_opt.sack_ok)
5527 tcp_sack_reset(&tp->rx_opt);
5528 }
5529 return pruned;
5530}
5531
5532/* Reduce allocated memory if we can, trying to get
5533 * the socket within its memory limits again.
5534 *
5535 * Return less than zero if we should start dropping frames
5536 * until the socket owning process reads some of the data
5537 * to stabilize the situation.
5538 */
5539static int tcp_prune_queue(struct sock *sk, const struct sk_buff *in_skb)
5540{
5541 struct tcp_sock *tp = tcp_sk(sk);
5542
5543 NET_INC_STATS(sock_net(sk), LINUX_MIB_PRUNECALLED);
5544
5545 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
5546 tcp_clamp_window(sk);
5547 else if (tcp_under_memory_pressure(sk))
5548 tcp_adjust_rcv_ssthresh(sk);
5549
5550 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
5551 return 0;
5552
5553 tcp_collapse_ofo_queue(sk);
5554 if (!skb_queue_empty(&sk->sk_receive_queue))
5555 tcp_collapse(sk, &sk->sk_receive_queue, NULL,
5556 skb_peek(&sk->sk_receive_queue),
5557 NULL,
5558 tp->copied_seq, tp->rcv_nxt);
5559
5560 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
5561 return 0;
5562
5563 /* Collapsing did not help, destructive actions follow.
5564 * This must not ever occur. */
5565
5566 tcp_prune_ofo_queue(sk, in_skb);
5567
5568 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
5569 return 0;
5570
5571 /* If we are really being abused, tell the caller to silently
5572 * drop receive data on the floor. It will get retransmitted
5573 * and hopefully then we'll have sufficient space.
5574 */
5575 NET_INC_STATS(sock_net(sk), LINUX_MIB_RCVPRUNED);
5576
5577 /* Massive buffer overcommit. */
5578 tp->pred_flags = 0;
5579 return -1;
5580}
5581
5582static bool tcp_should_expand_sndbuf(struct sock *sk)
5583{
5584 const struct tcp_sock *tp = tcp_sk(sk);
5585
5586 /* If the user specified a specific send buffer setting, do
5587 * not modify it.
5588 */
5589 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
5590 return false;
5591
5592 /* If we are under global TCP memory pressure, do not expand. */
5593 if (tcp_under_memory_pressure(sk)) {
5594 int unused_mem = sk_unused_reserved_mem(sk);
5595
5596 /* Adjust sndbuf according to reserved mem. But make sure
5597 * it never goes below SOCK_MIN_SNDBUF.
5598 * See sk_stream_moderate_sndbuf() for more details.
5599 */
5600 if (unused_mem > SOCK_MIN_SNDBUF)
5601 WRITE_ONCE(sk->sk_sndbuf, unused_mem);
5602
5603 return false;
5604 }
5605
5606 /* If we are under soft global TCP memory pressure, do not expand. */
5607 if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0))
5608 return false;
5609
5610 /* If we filled the congestion window, do not expand. */
5611 if (tcp_packets_in_flight(tp) >= tcp_snd_cwnd(tp))
5612 return false;
5613
5614 return true;
5615}
5616
5617static void tcp_new_space(struct sock *sk)
5618{
5619 struct tcp_sock *tp = tcp_sk(sk);
5620
5621 if (tcp_should_expand_sndbuf(sk)) {
5622 tcp_sndbuf_expand(sk);
5623 tp->snd_cwnd_stamp = tcp_jiffies32;
5624 }
5625
5626 INDIRECT_CALL_1(sk->sk_write_space, sk_stream_write_space, sk);
5627}
5628
5629/* Caller made space either from:
5630 * 1) Freeing skbs in rtx queues (after tp->snd_una has advanced)
5631 * 2) Sent skbs from output queue (and thus advancing tp->snd_nxt)
5632 *
5633 * We might be able to generate EPOLLOUT to the application if:
5634 * 1) Space consumed in output/rtx queues is below sk->sk_sndbuf/2
5635 * 2) notsent amount (tp->write_seq - tp->snd_nxt) became
5636 * small enough that tcp_stream_memory_free() decides it
5637 * is time to generate EPOLLOUT.
5638 */
5639void tcp_check_space(struct sock *sk)
5640{
5641 /* pairs with tcp_poll() */
5642 smp_mb();
5643 if (sk->sk_socket &&
5644 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
5645 tcp_new_space(sk);
5646 if (!test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
5647 tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
5648 }
5649}
5650
5651static inline void tcp_data_snd_check(struct sock *sk)
5652{
5653 tcp_push_pending_frames(sk);
5654 tcp_check_space(sk);
5655}
5656
5657/*
5658 * Check if sending an ack is needed.
5659 */
5660static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
5661{
5662 struct tcp_sock *tp = tcp_sk(sk);
5663 unsigned long rtt, delay;
5664
5665 /* More than one full frame received... */
5666 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
5667 /* ... and right edge of window advances far enough.
5668 * (tcp_recvmsg() will send ACK otherwise).
5669 * If application uses SO_RCVLOWAT, we want send ack now if
5670 * we have not received enough bytes to satisfy the condition.
5671 */
5672 (tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat ||
5673 __tcp_select_window(sk) >= tp->rcv_wnd)) ||
5674 /* We ACK each frame or... */
5675 tcp_in_quickack_mode(sk) ||
5676 /* Protocol state mandates a one-time immediate ACK */
5677 inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOW) {
5678 /* If we are running from __release_sock() in user context,
5679 * Defer the ack until tcp_release_cb().
5680 */
5681 if (sock_owned_by_user_nocheck(sk) &&
5682 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_backlog_ack_defer)) {
5683 set_bit(TCP_ACK_DEFERRED, &sk->sk_tsq_flags);
5684 return;
5685 }
5686send_now:
5687 tcp_send_ack(sk);
5688 return;
5689 }
5690
5691 if (!ofo_possible || RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
5692 tcp_send_delayed_ack(sk);
5693 return;
5694 }
5695
5696 if (!tcp_is_sack(tp) ||
5697 tp->compressed_ack >= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr))
5698 goto send_now;
5699
5700 if (tp->compressed_ack_rcv_nxt != tp->rcv_nxt) {
5701 tp->compressed_ack_rcv_nxt = tp->rcv_nxt;
5702 tp->dup_ack_counter = 0;
5703 }
5704 if (tp->dup_ack_counter < TCP_FASTRETRANS_THRESH) {
5705 tp->dup_ack_counter++;
5706 goto send_now;
5707 }
5708 tp->compressed_ack++;
5709 if (hrtimer_is_queued(&tp->compressed_ack_timer))
5710 return;
5711
5712 /* compress ack timer : 5 % of rtt, but no more than tcp_comp_sack_delay_ns */
5713
5714 rtt = tp->rcv_rtt_est.rtt_us;
5715 if (tp->srtt_us && tp->srtt_us < rtt)
5716 rtt = tp->srtt_us;
5717
5718 delay = min_t(unsigned long,
5719 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_delay_ns),
5720 rtt * (NSEC_PER_USEC >> 3)/20);
5721 sock_hold(sk);
5722 hrtimer_start_range_ns(&tp->compressed_ack_timer, ns_to_ktime(delay),
5723 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_slack_ns),
5724 HRTIMER_MODE_REL_PINNED_SOFT);
5725}
5726
5727static inline void tcp_ack_snd_check(struct sock *sk)
5728{
5729 if (!inet_csk_ack_scheduled(sk)) {
5730 /* We sent a data segment already. */
5731 return;
5732 }
5733 __tcp_ack_snd_check(sk, 1);
5734}
5735
5736/*
5737 * This routine is only called when we have urgent data
5738 * signaled. Its the 'slow' part of tcp_urg. It could be
5739 * moved inline now as tcp_urg is only called from one
5740 * place. We handle URGent data wrong. We have to - as
5741 * BSD still doesn't use the correction from RFC961.
5742 * For 1003.1g we should support a new option TCP_STDURG to permit
5743 * either form (or just set the sysctl tcp_stdurg).
5744 */
5745
5746static void tcp_check_urg(struct sock *sk, const struct tcphdr *th)
5747{
5748 struct tcp_sock *tp = tcp_sk(sk);
5749 u32 ptr = ntohs(th->urg_ptr);
5750
5751 if (ptr && !READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_stdurg))
5752 ptr--;
5753 ptr += ntohl(th->seq);
5754
5755 /* Ignore urgent data that we've already seen and read. */
5756 if (after(tp->copied_seq, ptr))
5757 return;
5758
5759 /* Do not replay urg ptr.
5760 *
5761 * NOTE: interesting situation not covered by specs.
5762 * Misbehaving sender may send urg ptr, pointing to segment,
5763 * which we already have in ofo queue. We are not able to fetch
5764 * such data and will stay in TCP_URG_NOTYET until will be eaten
5765 * by recvmsg(). Seems, we are not obliged to handle such wicked
5766 * situations. But it is worth to think about possibility of some
5767 * DoSes using some hypothetical application level deadlock.
5768 */
5769 if (before(ptr, tp->rcv_nxt))
5770 return;
5771
5772 /* Do we already have a newer (or duplicate) urgent pointer? */
5773 if (tp->urg_data && !after(ptr, tp->urg_seq))
5774 return;
5775
5776 /* Tell the world about our new urgent pointer. */
5777 sk_send_sigurg(sk);
5778
5779 /* We may be adding urgent data when the last byte read was
5780 * urgent. To do this requires some care. We cannot just ignore
5781 * tp->copied_seq since we would read the last urgent byte again
5782 * as data, nor can we alter copied_seq until this data arrives
5783 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5784 *
5785 * NOTE. Double Dutch. Rendering to plain English: author of comment
5786 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5787 * and expect that both A and B disappear from stream. This is _wrong_.
5788 * Though this happens in BSD with high probability, this is occasional.
5789 * Any application relying on this is buggy. Note also, that fix "works"
5790 * only in this artificial test. Insert some normal data between A and B and we will
5791 * decline of BSD again. Verdict: it is better to remove to trap
5792 * buggy users.
5793 */
5794 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
5795 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
5796 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
5797 tp->copied_seq++;
5798 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
5799 __skb_unlink(skb, &sk->sk_receive_queue);
5800 __kfree_skb(skb);
5801 }
5802 }
5803
5804 WRITE_ONCE(tp->urg_data, TCP_URG_NOTYET);
5805 WRITE_ONCE(tp->urg_seq, ptr);
5806
5807 /* Disable header prediction. */
5808 tp->pred_flags = 0;
5809}
5810
5811/* This is the 'fast' part of urgent handling. */
5812static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th)
5813{
5814 struct tcp_sock *tp = tcp_sk(sk);
5815
5816 /* Check if we get a new urgent pointer - normally not. */
5817 if (unlikely(th->urg))
5818 tcp_check_urg(sk, th);
5819
5820 /* Do we wait for any urgent data? - normally not... */
5821 if (unlikely(tp->urg_data == TCP_URG_NOTYET)) {
5822 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
5823 th->syn;
5824
5825 /* Is the urgent pointer pointing into this packet? */
5826 if (ptr < skb->len) {
5827 u8 tmp;
5828 if (skb_copy_bits(skb, ptr, &tmp, 1))
5829 BUG();
5830 WRITE_ONCE(tp->urg_data, TCP_URG_VALID | tmp);
5831 if (!sock_flag(sk, SOCK_DEAD))
5832 sk->sk_data_ready(sk);
5833 }
5834 }
5835}
5836
5837/* Accept RST for rcv_nxt - 1 after a FIN.
5838 * When tcp connections are abruptly terminated from Mac OSX (via ^C), a
5839 * FIN is sent followed by a RST packet. The RST is sent with the same
5840 * sequence number as the FIN, and thus according to RFC 5961 a challenge
5841 * ACK should be sent. However, Mac OSX rate limits replies to challenge
5842 * ACKs on the closed socket. In addition middleboxes can drop either the
5843 * challenge ACK or a subsequent RST.
5844 */
5845static bool tcp_reset_check(const struct sock *sk, const struct sk_buff *skb)
5846{
5847 const struct tcp_sock *tp = tcp_sk(sk);
5848
5849 return unlikely(TCP_SKB_CB(skb)->seq == (tp->rcv_nxt - 1) &&
5850 (1 << sk->sk_state) & (TCPF_CLOSE_WAIT | TCPF_LAST_ACK |
5851 TCPF_CLOSING));
5852}
5853
5854/* Does PAWS and seqno based validation of an incoming segment, flags will
5855 * play significant role here.
5856 */
5857static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
5858 const struct tcphdr *th, int syn_inerr)
5859{
5860 struct tcp_sock *tp = tcp_sk(sk);
5861 SKB_DR(reason);
5862
5863 /* RFC1323: H1. Apply PAWS check first. */
5864 if (tcp_fast_parse_options(sock_net(sk), skb, th, tp) &&
5865 tp->rx_opt.saw_tstamp &&
5866 tcp_paws_discard(sk, skb)) {
5867 if (!th->rst) {
5868 if (unlikely(th->syn))
5869 goto syn_challenge;
5870 NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
5871 if (!tcp_oow_rate_limited(sock_net(sk), skb,
5872 LINUX_MIB_TCPACKSKIPPEDPAWS,
5873 &tp->last_oow_ack_time))
5874 tcp_send_dupack(sk, skb);
5875 SKB_DR_SET(reason, TCP_RFC7323_PAWS);
5876 goto discard;
5877 }
5878 /* Reset is accepted even if it did not pass PAWS. */
5879 }
5880
5881 /* Step 1: check sequence number */
5882 reason = tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
5883 if (reason) {
5884 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5885 * (RST) segments are validated by checking their SEQ-fields."
5886 * And page 69: "If an incoming segment is not acceptable,
5887 * an acknowledgment should be sent in reply (unless the RST
5888 * bit is set, if so drop the segment and return)".
5889 */
5890 if (!th->rst) {
5891 if (th->syn)
5892 goto syn_challenge;
5893 if (!tcp_oow_rate_limited(sock_net(sk), skb,
5894 LINUX_MIB_TCPACKSKIPPEDSEQ,
5895 &tp->last_oow_ack_time))
5896 tcp_send_dupack(sk, skb);
5897 } else if (tcp_reset_check(sk, skb)) {
5898 goto reset;
5899 }
5900 goto discard;
5901 }
5902
5903 /* Step 2: check RST bit */
5904 if (th->rst) {
5905 /* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a
5906 * FIN and SACK too if available):
5907 * If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or
5908 * the right-most SACK block,
5909 * then
5910 * RESET the connection
5911 * else
5912 * Send a challenge ACK
5913 */
5914 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt ||
5915 tcp_reset_check(sk, skb))
5916 goto reset;
5917
5918 if (tcp_is_sack(tp) && tp->rx_opt.num_sacks > 0) {
5919 struct tcp_sack_block *sp = &tp->selective_acks[0];
5920 int max_sack = sp[0].end_seq;
5921 int this_sack;
5922
5923 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;
5924 ++this_sack) {
5925 max_sack = after(sp[this_sack].end_seq,
5926 max_sack) ?
5927 sp[this_sack].end_seq : max_sack;
5928 }
5929
5930 if (TCP_SKB_CB(skb)->seq == max_sack)
5931 goto reset;
5932 }
5933
5934 /* Disable TFO if RST is out-of-order
5935 * and no data has been received
5936 * for current active TFO socket
5937 */
5938 if (tp->syn_fastopen && !tp->data_segs_in &&
5939 sk->sk_state == TCP_ESTABLISHED)
5940 tcp_fastopen_active_disable(sk);
5941 tcp_send_challenge_ack(sk);
5942 SKB_DR_SET(reason, TCP_RESET);
5943 goto discard;
5944 }
5945
5946 /* step 3: check security and precedence [ignored] */
5947
5948 /* step 4: Check for a SYN
5949 * RFC 5961 4.2 : Send a challenge ack
5950 */
5951 if (th->syn) {
5952syn_challenge:
5953 if (syn_inerr)
5954 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
5955 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);
5956 tcp_send_challenge_ack(sk);
5957 SKB_DR_SET(reason, TCP_INVALID_SYN);
5958 goto discard;
5959 }
5960
5961 bpf_skops_parse_hdr(sk, skb);
5962
5963 return true;
5964
5965discard:
5966 tcp_drop_reason(sk, skb, reason);
5967 return false;
5968
5969reset:
5970 tcp_reset(sk, skb);
5971 __kfree_skb(skb);
5972 return false;
5973}
5974
5975/*
5976 * TCP receive function for the ESTABLISHED state.
5977 *
5978 * It is split into a fast path and a slow path. The fast path is
5979 * disabled when:
5980 * - A zero window was announced from us - zero window probing
5981 * is only handled properly in the slow path.
5982 * - Out of order segments arrived.
5983 * - Urgent data is expected.
5984 * - There is no buffer space left
5985 * - Unexpected TCP flags/window values/header lengths are received
5986 * (detected by checking the TCP header against pred_flags)
5987 * - Data is sent in both directions. Fast path only supports pure senders
5988 * or pure receivers (this means either the sequence number or the ack
5989 * value must stay constant)
5990 * - Unexpected TCP option.
5991 *
5992 * When these conditions are not satisfied it drops into a standard
5993 * receive procedure patterned after RFC793 to handle all cases.
5994 * The first three cases are guaranteed by proper pred_flags setting,
5995 * the rest is checked inline. Fast processing is turned on in
5996 * tcp_data_queue when everything is OK.
5997 */
5998void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
5999{
6000 enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
6001 const struct tcphdr *th = (const struct tcphdr *)skb->data;
6002 struct tcp_sock *tp = tcp_sk(sk);
6003 unsigned int len = skb->len;
6004
6005 /* TCP congestion window tracking */
6006 trace_tcp_probe(sk, skb);
6007
6008 tcp_mstamp_refresh(tp);
6009 if (unlikely(!rcu_access_pointer(sk->sk_rx_dst)))
6010 inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
6011 /*
6012 * Header prediction.
6013 * The code loosely follows the one in the famous
6014 * "30 instruction TCP receive" Van Jacobson mail.
6015 *
6016 * Van's trick is to deposit buffers into socket queue
6017 * on a device interrupt, to call tcp_recv function
6018 * on the receive process context and checksum and copy
6019 * the buffer to user space. smart...
6020 *
6021 * Our current scheme is not silly either but we take the
6022 * extra cost of the net_bh soft interrupt processing...
6023 * We do checksum and copy also but from device to kernel.
6024 */
6025
6026 tp->rx_opt.saw_tstamp = 0;
6027
6028 /* pred_flags is 0xS?10 << 16 + snd_wnd
6029 * if header_prediction is to be made
6030 * 'S' will always be tp->tcp_header_len >> 2
6031 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
6032 * turn it off (when there are holes in the receive
6033 * space for instance)
6034 * PSH flag is ignored.
6035 */
6036
6037 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
6038 TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
6039 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
6040 int tcp_header_len = tp->tcp_header_len;
6041
6042 /* Timestamp header prediction: tcp_header_len
6043 * is automatically equal to th->doff*4 due to pred_flags
6044 * match.
6045 */
6046
6047 /* Check timestamp */
6048 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
6049 /* No? Slow path! */
6050 if (!tcp_parse_aligned_timestamp(tp, th))
6051 goto slow_path;
6052
6053 /* If PAWS failed, check it more carefully in slow path */
6054 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
6055 goto slow_path;
6056
6057 /* DO NOT update ts_recent here, if checksum fails
6058 * and timestamp was corrupted part, it will result
6059 * in a hung connection since we will drop all
6060 * future packets due to the PAWS test.
6061 */
6062 }
6063
6064 if (len <= tcp_header_len) {
6065 /* Bulk data transfer: sender */
6066 if (len == tcp_header_len) {
6067 /* Predicted packet is in window by definition.
6068 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
6069 * Hence, check seq<=rcv_wup reduces to:
6070 */
6071 if (tcp_header_len ==
6072 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
6073 tp->rcv_nxt == tp->rcv_wup)
6074 tcp_store_ts_recent(tp);
6075
6076 /* We know that such packets are checksummed
6077 * on entry.
6078 */
6079 tcp_ack(sk, skb, 0);
6080 __kfree_skb(skb);
6081 tcp_data_snd_check(sk);
6082 /* When receiving pure ack in fast path, update
6083 * last ts ecr directly instead of calling
6084 * tcp_rcv_rtt_measure_ts()
6085 */
6086 tp->rcv_rtt_last_tsecr = tp->rx_opt.rcv_tsecr;
6087 return;
6088 } else { /* Header too small */
6089 reason = SKB_DROP_REASON_PKT_TOO_SMALL;
6090 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
6091 goto discard;
6092 }
6093 } else {
6094 int eaten = 0;
6095 bool fragstolen = false;
6096
6097 if (tcp_checksum_complete(skb))
6098 goto csum_error;
6099
6100 if ((int)skb->truesize > sk->sk_forward_alloc)
6101 goto step5;
6102
6103 /* Predicted packet is in window by definition.
6104 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
6105 * Hence, check seq<=rcv_wup reduces to:
6106 */
6107 if (tcp_header_len ==
6108 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
6109 tp->rcv_nxt == tp->rcv_wup)
6110 tcp_store_ts_recent(tp);
6111
6112 tcp_rcv_rtt_measure_ts(sk, skb);
6113
6114 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPHITS);
6115
6116 /* Bulk data transfer: receiver */
6117 skb_dst_drop(skb);
6118 __skb_pull(skb, tcp_header_len);
6119 eaten = tcp_queue_rcv(sk, skb, &fragstolen);
6120
6121 tcp_event_data_recv(sk, skb);
6122
6123 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
6124 /* Well, only one small jumplet in fast path... */
6125 tcp_ack(sk, skb, FLAG_DATA);
6126 tcp_data_snd_check(sk);
6127 if (!inet_csk_ack_scheduled(sk))
6128 goto no_ack;
6129 } else {
6130 tcp_update_wl(tp, TCP_SKB_CB(skb)->seq);
6131 }
6132
6133 __tcp_ack_snd_check(sk, 0);
6134no_ack:
6135 if (eaten)
6136 kfree_skb_partial(skb, fragstolen);
6137 tcp_data_ready(sk);
6138 return;
6139 }
6140 }
6141
6142slow_path:
6143 if (len < (th->doff << 2) || tcp_checksum_complete(skb))
6144 goto csum_error;
6145
6146 if (!th->ack && !th->rst && !th->syn) {
6147 reason = SKB_DROP_REASON_TCP_FLAGS;
6148 goto discard;
6149 }
6150
6151 /*
6152 * Standard slow path.
6153 */
6154
6155 if (!tcp_validate_incoming(sk, skb, th, 1))
6156 return;
6157
6158step5:
6159 reason = tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT);
6160 if ((int)reason < 0) {
6161 reason = -reason;
6162 goto discard;
6163 }
6164 tcp_rcv_rtt_measure_ts(sk, skb);
6165
6166 /* Process urgent data. */
6167 tcp_urg(sk, skb, th);
6168
6169 /* step 7: process the segment text */
6170 tcp_data_queue(sk, skb);
6171
6172 tcp_data_snd_check(sk);
6173 tcp_ack_snd_check(sk);
6174 return;
6175
6176csum_error:
6177 reason = SKB_DROP_REASON_TCP_CSUM;
6178 trace_tcp_bad_csum(skb);
6179 TCP_INC_STATS(sock_net(sk), TCP_MIB_CSUMERRORS);
6180 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
6181
6182discard:
6183 tcp_drop_reason(sk, skb, reason);
6184}
6185EXPORT_SYMBOL(tcp_rcv_established);
6186
6187void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb)
6188{
6189 struct inet_connection_sock *icsk = inet_csk(sk);
6190 struct tcp_sock *tp = tcp_sk(sk);
6191
6192 tcp_mtup_init(sk);
6193 icsk->icsk_af_ops->rebuild_header(sk);
6194 tcp_init_metrics(sk);
6195
6196 /* Initialize the congestion window to start the transfer.
6197 * Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
6198 * retransmitted. In light of RFC6298 more aggressive 1sec
6199 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
6200 * retransmission has occurred.
6201 */
6202 if (tp->total_retrans > 1 && tp->undo_marker)
6203 tcp_snd_cwnd_set(tp, 1);
6204 else
6205 tcp_snd_cwnd_set(tp, tcp_init_cwnd(tp, __sk_dst_get(sk)));
6206 tp->snd_cwnd_stamp = tcp_jiffies32;
6207
6208 bpf_skops_established(sk, bpf_op, skb);
6209 /* Initialize congestion control unless BPF initialized it already: */
6210 if (!icsk->icsk_ca_initialized)
6211 tcp_init_congestion_control(sk);
6212 tcp_init_buffer_space(sk);
6213}
6214
6215void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
6216{
6217 struct tcp_sock *tp = tcp_sk(sk);
6218 struct inet_connection_sock *icsk = inet_csk(sk);
6219
6220 tcp_ao_finish_connect(sk, skb);
6221 tcp_set_state(sk, TCP_ESTABLISHED);
6222 icsk->icsk_ack.lrcvtime = tcp_jiffies32;
6223
6224 if (skb) {
6225 icsk->icsk_af_ops->sk_rx_dst_set(sk, skb);
6226 security_inet_conn_established(sk, skb);
6227 sk_mark_napi_id(sk, skb);
6228 }
6229
6230 tcp_init_transfer(sk, BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB, skb);
6231
6232 /* Prevent spurious tcp_cwnd_restart() on first data
6233 * packet.
6234 */
6235 tp->lsndtime = tcp_jiffies32;
6236
6237 if (sock_flag(sk, SOCK_KEEPOPEN))
6238 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
6239
6240 if (!tp->rx_opt.snd_wscale)
6241 __tcp_fast_path_on(tp, tp->snd_wnd);
6242 else
6243 tp->pred_flags = 0;
6244}
6245
6246static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
6247 struct tcp_fastopen_cookie *cookie)
6248{
6249 struct tcp_sock *tp = tcp_sk(sk);
6250 struct sk_buff *data = tp->syn_data ? tcp_rtx_queue_head(sk) : NULL;
6251 u16 mss = tp->rx_opt.mss_clamp, try_exp = 0;
6252 bool syn_drop = false;
6253
6254 if (mss == tp->rx_opt.user_mss) {
6255 struct tcp_options_received opt;
6256
6257 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
6258 tcp_clear_options(&opt);
6259 opt.user_mss = opt.mss_clamp = 0;
6260 tcp_parse_options(sock_net(sk), synack, &opt, 0, NULL);
6261 mss = opt.mss_clamp;
6262 }
6263
6264 if (!tp->syn_fastopen) {
6265 /* Ignore an unsolicited cookie */
6266 cookie->len = -1;
6267 } else if (tp->total_retrans) {
6268 /* SYN timed out and the SYN-ACK neither has a cookie nor
6269 * acknowledges data. Presumably the remote received only
6270 * the retransmitted (regular) SYNs: either the original
6271 * SYN-data or the corresponding SYN-ACK was dropped.
6272 */
6273 syn_drop = (cookie->len < 0 && data);
6274 } else if (cookie->len < 0 && !tp->syn_data) {
6275 /* We requested a cookie but didn't get it. If we did not use
6276 * the (old) exp opt format then try so next time (try_exp=1).
6277 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
6278 */
6279 try_exp = tp->syn_fastopen_exp ? 2 : 1;
6280 }
6281
6282 tcp_fastopen_cache_set(sk, mss, cookie, syn_drop, try_exp);
6283
6284 if (data) { /* Retransmit unacked data in SYN */
6285 if (tp->total_retrans)
6286 tp->fastopen_client_fail = TFO_SYN_RETRANSMITTED;
6287 else
6288 tp->fastopen_client_fail = TFO_DATA_NOT_ACKED;
6289 skb_rbtree_walk_from(data)
6290 tcp_mark_skb_lost(sk, data);
6291 tcp_xmit_retransmit_queue(sk);
6292 NET_INC_STATS(sock_net(sk),
6293 LINUX_MIB_TCPFASTOPENACTIVEFAIL);
6294 return true;
6295 }
6296 tp->syn_data_acked = tp->syn_data;
6297 if (tp->syn_data_acked) {
6298 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
6299 /* SYN-data is counted as two separate packets in tcp_ack() */
6300 if (tp->delivered > 1)
6301 --tp->delivered;
6302 }
6303
6304 tcp_fastopen_add_skb(sk, synack);
6305
6306 return false;
6307}
6308
6309static void smc_check_reset_syn(struct tcp_sock *tp)
6310{
6311#if IS_ENABLED(CONFIG_SMC)
6312 if (static_branch_unlikely(&tcp_have_smc)) {
6313 if (tp->syn_smc && !tp->rx_opt.smc_ok)
6314 tp->syn_smc = 0;
6315 }
6316#endif
6317}
6318
6319static void tcp_try_undo_spurious_syn(struct sock *sk)
6320{
6321 struct tcp_sock *tp = tcp_sk(sk);
6322 u32 syn_stamp;
6323
6324 /* undo_marker is set when SYN or SYNACK times out. The timeout is
6325 * spurious if the ACK's timestamp option echo value matches the
6326 * original SYN timestamp.
6327 */
6328 syn_stamp = tp->retrans_stamp;
6329 if (tp->undo_marker && syn_stamp && tp->rx_opt.saw_tstamp &&
6330 syn_stamp == tp->rx_opt.rcv_tsecr)
6331 tp->undo_marker = 0;
6332}
6333
6334static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
6335 const struct tcphdr *th)
6336{
6337 struct inet_connection_sock *icsk = inet_csk(sk);
6338 struct tcp_sock *tp = tcp_sk(sk);
6339 struct tcp_fastopen_cookie foc = { .len = -1 };
6340 int saved_clamp = tp->rx_opt.mss_clamp;
6341 bool fastopen_fail;
6342 SKB_DR(reason);
6343
6344 tcp_parse_options(sock_net(sk), skb, &tp->rx_opt, 0, &foc);
6345 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
6346 tp->rx_opt.rcv_tsecr -= tp->tsoffset;
6347
6348 if (th->ack) {
6349 /* rfc793:
6350 * "If the state is SYN-SENT then
6351 * first check the ACK bit
6352 * If the ACK bit is set
6353 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
6354 * a reset (unless the RST bit is set, if so drop
6355 * the segment and return)"
6356 */
6357 if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
6358 after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
6359 /* Previous FIN/ACK or RST/ACK might be ignored. */
6360 if (icsk->icsk_retransmits == 0)
6361 inet_csk_reset_xmit_timer(sk,
6362 ICSK_TIME_RETRANS,
6363 TCP_TIMEOUT_MIN, TCP_RTO_MAX);
6364 goto reset_and_undo;
6365 }
6366
6367 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
6368 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
6369 tcp_time_stamp_ts(tp))) {
6370 NET_INC_STATS(sock_net(sk),
6371 LINUX_MIB_PAWSACTIVEREJECTED);
6372 goto reset_and_undo;
6373 }
6374
6375 /* Now ACK is acceptable.
6376 *
6377 * "If the RST bit is set
6378 * If the ACK was acceptable then signal the user "error:
6379 * connection reset", drop the segment, enter CLOSED state,
6380 * delete TCB, and return."
6381 */
6382
6383 if (th->rst) {
6384 tcp_reset(sk, skb);
6385consume:
6386 __kfree_skb(skb);
6387 return 0;
6388 }
6389
6390 /* rfc793:
6391 * "fifth, if neither of the SYN or RST bits is set then
6392 * drop the segment and return."
6393 *
6394 * See note below!
6395 * --ANK(990513)
6396 */
6397 if (!th->syn) {
6398 SKB_DR_SET(reason, TCP_FLAGS);
6399 goto discard_and_undo;
6400 }
6401 /* rfc793:
6402 * "If the SYN bit is on ...
6403 * are acceptable then ...
6404 * (our SYN has been ACKed), change the connection
6405 * state to ESTABLISHED..."
6406 */
6407
6408 tcp_ecn_rcv_synack(tp, th);
6409
6410 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
6411 tcp_try_undo_spurious_syn(sk);
6412 tcp_ack(sk, skb, FLAG_SLOWPATH);
6413
6414 /* Ok.. it's good. Set up sequence numbers and
6415 * move to established.
6416 */
6417 WRITE_ONCE(tp->rcv_nxt, TCP_SKB_CB(skb)->seq + 1);
6418 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
6419
6420 /* RFC1323: The window in SYN & SYN/ACK segments is
6421 * never scaled.
6422 */
6423 tp->snd_wnd = ntohs(th->window);
6424
6425 if (!tp->rx_opt.wscale_ok) {
6426 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
6427 tp->window_clamp = min(tp->window_clamp, 65535U);
6428 }
6429
6430 if (tp->rx_opt.saw_tstamp) {
6431 tp->rx_opt.tstamp_ok = 1;
6432 tp->tcp_header_len =
6433 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
6434 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
6435 tcp_store_ts_recent(tp);
6436 } else {
6437 tp->tcp_header_len = sizeof(struct tcphdr);
6438 }
6439
6440 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
6441 tcp_initialize_rcv_mss(sk);
6442
6443 /* Remember, tcp_poll() does not lock socket!
6444 * Change state from SYN-SENT only after copied_seq
6445 * is initialized. */
6446 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
6447
6448 smc_check_reset_syn(tp);
6449
6450 smp_mb();
6451
6452 tcp_finish_connect(sk, skb);
6453
6454 fastopen_fail = (tp->syn_fastopen || tp->syn_data) &&
6455 tcp_rcv_fastopen_synack(sk, skb, &foc);
6456
6457 if (!sock_flag(sk, SOCK_DEAD)) {
6458 sk->sk_state_change(sk);
6459 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
6460 }
6461 if (fastopen_fail)
6462 return -1;
6463 if (sk->sk_write_pending ||
6464 READ_ONCE(icsk->icsk_accept_queue.rskq_defer_accept) ||
6465 inet_csk_in_pingpong_mode(sk)) {
6466 /* Save one ACK. Data will be ready after
6467 * several ticks, if write_pending is set.
6468 *
6469 * It may be deleted, but with this feature tcpdumps
6470 * look so _wonderfully_ clever, that I was not able
6471 * to stand against the temptation 8) --ANK
6472 */
6473 inet_csk_schedule_ack(sk);
6474 tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
6475 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
6476 TCP_DELACK_MAX, TCP_RTO_MAX);
6477 goto consume;
6478 }
6479 tcp_send_ack(sk);
6480 return -1;
6481 }
6482
6483 /* No ACK in the segment */
6484
6485 if (th->rst) {
6486 /* rfc793:
6487 * "If the RST bit is set
6488 *
6489 * Otherwise (no ACK) drop the segment and return."
6490 */
6491 SKB_DR_SET(reason, TCP_RESET);
6492 goto discard_and_undo;
6493 }
6494
6495 /* PAWS check. */
6496 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
6497 tcp_paws_reject(&tp->rx_opt, 0)) {
6498 SKB_DR_SET(reason, TCP_RFC7323_PAWS);
6499 goto discard_and_undo;
6500 }
6501 if (th->syn) {
6502 /* We see SYN without ACK. It is attempt of
6503 * simultaneous connect with crossed SYNs.
6504 * Particularly, it can be connect to self.
6505 */
6506#ifdef CONFIG_TCP_AO
6507 struct tcp_ao_info *ao;
6508
6509 ao = rcu_dereference_protected(tp->ao_info,
6510 lockdep_sock_is_held(sk));
6511 if (ao) {
6512 WRITE_ONCE(ao->risn, th->seq);
6513 ao->rcv_sne = 0;
6514 }
6515#endif
6516 tcp_set_state(sk, TCP_SYN_RECV);
6517
6518 if (tp->rx_opt.saw_tstamp) {
6519 tp->rx_opt.tstamp_ok = 1;
6520 tcp_store_ts_recent(tp);
6521 tp->tcp_header_len =
6522 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
6523 } else {
6524 tp->tcp_header_len = sizeof(struct tcphdr);
6525 }
6526
6527 WRITE_ONCE(tp->rcv_nxt, TCP_SKB_CB(skb)->seq + 1);
6528 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
6529 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
6530
6531 /* RFC1323: The window in SYN & SYN/ACK segments is
6532 * never scaled.
6533 */
6534 tp->snd_wnd = ntohs(th->window);
6535 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
6536 tp->max_window = tp->snd_wnd;
6537
6538 tcp_ecn_rcv_syn(tp, th);
6539
6540 tcp_mtup_init(sk);
6541 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
6542 tcp_initialize_rcv_mss(sk);
6543
6544 tcp_send_synack(sk);
6545#if 0
6546 /* Note, we could accept data and URG from this segment.
6547 * There are no obstacles to make this (except that we must
6548 * either change tcp_recvmsg() to prevent it from returning data
6549 * before 3WHS completes per RFC793, or employ TCP Fast Open).
6550 *
6551 * However, if we ignore data in ACKless segments sometimes,
6552 * we have no reasons to accept it sometimes.
6553 * Also, seems the code doing it in step6 of tcp_rcv_state_process
6554 * is not flawless. So, discard packet for sanity.
6555 * Uncomment this return to process the data.
6556 */
6557 return -1;
6558#else
6559 goto consume;
6560#endif
6561 }
6562 /* "fifth, if neither of the SYN or RST bits is set then
6563 * drop the segment and return."
6564 */
6565
6566discard_and_undo:
6567 tcp_clear_options(&tp->rx_opt);
6568 tp->rx_opt.mss_clamp = saved_clamp;
6569 tcp_drop_reason(sk, skb, reason);
6570 return 0;
6571
6572reset_and_undo:
6573 tcp_clear_options(&tp->rx_opt);
6574 tp->rx_opt.mss_clamp = saved_clamp;
6575 return 1;
6576}
6577
6578static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
6579{
6580 struct tcp_sock *tp = tcp_sk(sk);
6581 struct request_sock *req;
6582
6583 /* If we are still handling the SYNACK RTO, see if timestamp ECR allows
6584 * undo. If peer SACKs triggered fast recovery, we can't undo here.
6585 */
6586 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss && !tp->packets_out)
6587 tcp_try_undo_recovery(sk);
6588
6589 /* Reset rtx states to prevent spurious retransmits_timed_out() */
6590 tcp_update_rto_time(tp);
6591 tp->retrans_stamp = 0;
6592 inet_csk(sk)->icsk_retransmits = 0;
6593
6594 /* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,
6595 * we no longer need req so release it.
6596 */
6597 req = rcu_dereference_protected(tp->fastopen_rsk,
6598 lockdep_sock_is_held(sk));
6599 reqsk_fastopen_remove(sk, req, false);
6600
6601 /* Re-arm the timer because data may have been sent out.
6602 * This is similar to the regular data transmission case
6603 * when new data has just been ack'ed.
6604 *
6605 * (TFO) - we could try to be more aggressive and
6606 * retransmitting any data sooner based on when they
6607 * are sent out.
6608 */
6609 tcp_rearm_rto(sk);
6610}
6611
6612/*
6613 * This function implements the receiving procedure of RFC 793 for
6614 * all states except ESTABLISHED and TIME_WAIT.
6615 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
6616 * address independent.
6617 */
6618
6619int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
6620{
6621 struct tcp_sock *tp = tcp_sk(sk);
6622 struct inet_connection_sock *icsk = inet_csk(sk);
6623 const struct tcphdr *th = tcp_hdr(skb);
6624 struct request_sock *req;
6625 int queued = 0;
6626 bool acceptable;
6627 SKB_DR(reason);
6628
6629 switch (sk->sk_state) {
6630 case TCP_CLOSE:
6631 SKB_DR_SET(reason, TCP_CLOSE);
6632 goto discard;
6633
6634 case TCP_LISTEN:
6635 if (th->ack)
6636 return 1;
6637
6638 if (th->rst) {
6639 SKB_DR_SET(reason, TCP_RESET);
6640 goto discard;
6641 }
6642 if (th->syn) {
6643 if (th->fin) {
6644 SKB_DR_SET(reason, TCP_FLAGS);
6645 goto discard;
6646 }
6647 /* It is possible that we process SYN packets from backlog,
6648 * so we need to make sure to disable BH and RCU right there.
6649 */
6650 rcu_read_lock();
6651 local_bh_disable();
6652 acceptable = icsk->icsk_af_ops->conn_request(sk, skb) >= 0;
6653 local_bh_enable();
6654 rcu_read_unlock();
6655
6656 if (!acceptable)
6657 return 1;
6658 consume_skb(skb);
6659 return 0;
6660 }
6661 SKB_DR_SET(reason, TCP_FLAGS);
6662 goto discard;
6663
6664 case TCP_SYN_SENT:
6665 tp->rx_opt.saw_tstamp = 0;
6666 tcp_mstamp_refresh(tp);
6667 queued = tcp_rcv_synsent_state_process(sk, skb, th);
6668 if (queued >= 0)
6669 return queued;
6670
6671 /* Do step6 onward by hand. */
6672 tcp_urg(sk, skb, th);
6673 __kfree_skb(skb);
6674 tcp_data_snd_check(sk);
6675 return 0;
6676 }
6677
6678 tcp_mstamp_refresh(tp);
6679 tp->rx_opt.saw_tstamp = 0;
6680 req = rcu_dereference_protected(tp->fastopen_rsk,
6681 lockdep_sock_is_held(sk));
6682 if (req) {
6683 bool req_stolen;
6684
6685 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
6686 sk->sk_state != TCP_FIN_WAIT1);
6687
6688 if (!tcp_check_req(sk, skb, req, true, &req_stolen)) {
6689 SKB_DR_SET(reason, TCP_FASTOPEN);
6690 goto discard;
6691 }
6692 }
6693
6694 if (!th->ack && !th->rst && !th->syn) {
6695 SKB_DR_SET(reason, TCP_FLAGS);
6696 goto discard;
6697 }
6698 if (!tcp_validate_incoming(sk, skb, th, 0))
6699 return 0;
6700
6701 /* step 5: check the ACK field */
6702 acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
6703 FLAG_UPDATE_TS_RECENT |
6704 FLAG_NO_CHALLENGE_ACK) > 0;
6705
6706 if (!acceptable) {
6707 if (sk->sk_state == TCP_SYN_RECV)
6708 return 1; /* send one RST */
6709 tcp_send_challenge_ack(sk);
6710 SKB_DR_SET(reason, TCP_OLD_ACK);
6711 goto discard;
6712 }
6713 switch (sk->sk_state) {
6714 case TCP_SYN_RECV:
6715 tp->delivered++; /* SYN-ACK delivery isn't tracked in tcp_ack */
6716 if (!tp->srtt_us)
6717 tcp_synack_rtt_meas(sk, req);
6718
6719 if (req) {
6720 tcp_rcv_synrecv_state_fastopen(sk);
6721 } else {
6722 tcp_try_undo_spurious_syn(sk);
6723 tp->retrans_stamp = 0;
6724 tcp_init_transfer(sk, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB,
6725 skb);
6726 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
6727 }
6728 tcp_ao_established(sk);
6729 smp_mb();
6730 tcp_set_state(sk, TCP_ESTABLISHED);
6731 sk->sk_state_change(sk);
6732
6733 /* Note, that this wakeup is only for marginal crossed SYN case.
6734 * Passively open sockets are not waked up, because
6735 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
6736 */
6737 if (sk->sk_socket)
6738 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
6739
6740 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
6741 tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
6742 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
6743
6744 if (tp->rx_opt.tstamp_ok)
6745 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
6746
6747 if (!inet_csk(sk)->icsk_ca_ops->cong_control)
6748 tcp_update_pacing_rate(sk);
6749
6750 /* Prevent spurious tcp_cwnd_restart() on first data packet */
6751 tp->lsndtime = tcp_jiffies32;
6752
6753 tcp_initialize_rcv_mss(sk);
6754 tcp_fast_path_on(tp);
6755 break;
6756
6757 case TCP_FIN_WAIT1: {
6758 int tmo;
6759
6760 if (req)
6761 tcp_rcv_synrecv_state_fastopen(sk);
6762
6763 if (tp->snd_una != tp->write_seq)
6764 break;
6765
6766 tcp_set_state(sk, TCP_FIN_WAIT2);
6767 WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | SEND_SHUTDOWN);
6768
6769 sk_dst_confirm(sk);
6770
6771 if (!sock_flag(sk, SOCK_DEAD)) {
6772 /* Wake up lingering close() */
6773 sk->sk_state_change(sk);
6774 break;
6775 }
6776
6777 if (READ_ONCE(tp->linger2) < 0) {
6778 tcp_done(sk);
6779 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
6780 return 1;
6781 }
6782 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
6783 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
6784 /* Receive out of order FIN after close() */
6785 if (tp->syn_fastopen && th->fin)
6786 tcp_fastopen_active_disable(sk);
6787 tcp_done(sk);
6788 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
6789 return 1;
6790 }
6791
6792 tmo = tcp_fin_time(sk);
6793 if (tmo > TCP_TIMEWAIT_LEN) {
6794 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
6795 } else if (th->fin || sock_owned_by_user(sk)) {
6796 /* Bad case. We could lose such FIN otherwise.
6797 * It is not a big problem, but it looks confusing
6798 * and not so rare event. We still can lose it now,
6799 * if it spins in bh_lock_sock(), but it is really
6800 * marginal case.
6801 */
6802 inet_csk_reset_keepalive_timer(sk, tmo);
6803 } else {
6804 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
6805 goto consume;
6806 }
6807 break;
6808 }
6809
6810 case TCP_CLOSING:
6811 if (tp->snd_una == tp->write_seq) {
6812 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
6813 goto consume;
6814 }
6815 break;
6816
6817 case TCP_LAST_ACK:
6818 if (tp->snd_una == tp->write_seq) {
6819 tcp_update_metrics(sk);
6820 tcp_done(sk);
6821 goto consume;
6822 }
6823 break;
6824 }
6825
6826 /* step 6: check the URG bit */
6827 tcp_urg(sk, skb, th);
6828
6829 /* step 7: process the segment text */
6830 switch (sk->sk_state) {
6831 case TCP_CLOSE_WAIT:
6832 case TCP_CLOSING:
6833 case TCP_LAST_ACK:
6834 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
6835 /* If a subflow has been reset, the packet should not
6836 * continue to be processed, drop the packet.
6837 */
6838 if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb))
6839 goto discard;
6840 break;
6841 }
6842 fallthrough;
6843 case TCP_FIN_WAIT1:
6844 case TCP_FIN_WAIT2:
6845 /* RFC 793 says to queue data in these states,
6846 * RFC 1122 says we MUST send a reset.
6847 * BSD 4.4 also does reset.
6848 */
6849 if (sk->sk_shutdown & RCV_SHUTDOWN) {
6850 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
6851 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
6852 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
6853 tcp_reset(sk, skb);
6854 return 1;
6855 }
6856 }
6857 fallthrough;
6858 case TCP_ESTABLISHED:
6859 tcp_data_queue(sk, skb);
6860 queued = 1;
6861 break;
6862 }
6863
6864 /* tcp_data could move socket to TIME-WAIT */
6865 if (sk->sk_state != TCP_CLOSE) {
6866 tcp_data_snd_check(sk);
6867 tcp_ack_snd_check(sk);
6868 }
6869
6870 if (!queued) {
6871discard:
6872 tcp_drop_reason(sk, skb, reason);
6873 }
6874 return 0;
6875
6876consume:
6877 __kfree_skb(skb);
6878 return 0;
6879}
6880EXPORT_SYMBOL(tcp_rcv_state_process);
6881
6882static inline void pr_drop_req(struct request_sock *req, __u16 port, int family)
6883{
6884 struct inet_request_sock *ireq = inet_rsk(req);
6885
6886 if (family == AF_INET)
6887 net_dbg_ratelimited("drop open request from %pI4/%u\n",
6888 &ireq->ir_rmt_addr, port);
6889#if IS_ENABLED(CONFIG_IPV6)
6890 else if (family == AF_INET6)
6891 net_dbg_ratelimited("drop open request from %pI6/%u\n",
6892 &ireq->ir_v6_rmt_addr, port);
6893#endif
6894}
6895
6896/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
6897 *
6898 * If we receive a SYN packet with these bits set, it means a
6899 * network is playing bad games with TOS bits. In order to
6900 * avoid possible false congestion notifications, we disable
6901 * TCP ECN negotiation.
6902 *
6903 * Exception: tcp_ca wants ECN. This is required for DCTCP
6904 * congestion control: Linux DCTCP asserts ECT on all packets,
6905 * including SYN, which is most optimal solution; however,
6906 * others, such as FreeBSD do not.
6907 *
6908 * Exception: At least one of the reserved bits of the TCP header (th->res1) is
6909 * set, indicating the use of a future TCP extension (such as AccECN). See
6910 * RFC8311 §4.3 which updates RFC3168 to allow the development of such
6911 * extensions.
6912 */
6913static void tcp_ecn_create_request(struct request_sock *req,
6914 const struct sk_buff *skb,
6915 const struct sock *listen_sk,
6916 const struct dst_entry *dst)
6917{
6918 const struct tcphdr *th = tcp_hdr(skb);
6919 const struct net *net = sock_net(listen_sk);
6920 bool th_ecn = th->ece && th->cwr;
6921 bool ect, ecn_ok;
6922 u32 ecn_ok_dst;
6923
6924 if (!th_ecn)
6925 return;
6926
6927 ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield);
6928 ecn_ok_dst = dst_feature(dst, DST_FEATURE_ECN_MASK);
6929 ecn_ok = READ_ONCE(net->ipv4.sysctl_tcp_ecn) || ecn_ok_dst;
6930
6931 if (((!ect || th->res1) && ecn_ok) || tcp_ca_needs_ecn(listen_sk) ||
6932 (ecn_ok_dst & DST_FEATURE_ECN_CA) ||
6933 tcp_bpf_ca_needs_ecn((struct sock *)req))
6934 inet_rsk(req)->ecn_ok = 1;
6935}
6936
6937static void tcp_openreq_init(struct request_sock *req,
6938 const struct tcp_options_received *rx_opt,
6939 struct sk_buff *skb, const struct sock *sk)
6940{
6941 struct inet_request_sock *ireq = inet_rsk(req);
6942
6943 req->rsk_rcv_wnd = 0; /* So that tcp_send_synack() knows! */
6944 tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
6945 tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
6946 tcp_rsk(req)->snt_synack = 0;
6947 tcp_rsk(req)->last_oow_ack_time = 0;
6948 req->mss = rx_opt->mss_clamp;
6949 req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
6950 ireq->tstamp_ok = rx_opt->tstamp_ok;
6951 ireq->sack_ok = rx_opt->sack_ok;
6952 ireq->snd_wscale = rx_opt->snd_wscale;
6953 ireq->wscale_ok = rx_opt->wscale_ok;
6954 ireq->acked = 0;
6955 ireq->ecn_ok = 0;
6956 ireq->ir_rmt_port = tcp_hdr(skb)->source;
6957 ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
6958 ireq->ir_mark = inet_request_mark(sk, skb);
6959#if IS_ENABLED(CONFIG_SMC)
6960 ireq->smc_ok = rx_opt->smc_ok && !(tcp_sk(sk)->smc_hs_congested &&
6961 tcp_sk(sk)->smc_hs_congested(sk));
6962#endif
6963}
6964
6965struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
6966 struct sock *sk_listener,
6967 bool attach_listener)
6968{
6969 struct request_sock *req = reqsk_alloc(ops, sk_listener,
6970 attach_listener);
6971
6972 if (req) {
6973 struct inet_request_sock *ireq = inet_rsk(req);
6974
6975 ireq->ireq_opt = NULL;
6976#if IS_ENABLED(CONFIG_IPV6)
6977 ireq->pktopts = NULL;
6978#endif
6979 atomic64_set(&ireq->ir_cookie, 0);
6980 ireq->ireq_state = TCP_NEW_SYN_RECV;
6981 write_pnet(&ireq->ireq_net, sock_net(sk_listener));
6982 ireq->ireq_family = sk_listener->sk_family;
6983 req->timeout = TCP_TIMEOUT_INIT;
6984 }
6985
6986 return req;
6987}
6988EXPORT_SYMBOL(inet_reqsk_alloc);
6989
6990/*
6991 * Return true if a syncookie should be sent
6992 */
6993static bool tcp_syn_flood_action(const struct sock *sk, const char *proto)
6994{
6995 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
6996 const char *msg = "Dropping request";
6997 struct net *net = sock_net(sk);
6998 bool want_cookie = false;
6999 u8 syncookies;
7000
7001 syncookies = READ_ONCE(net->ipv4.sysctl_tcp_syncookies);
7002
7003#ifdef CONFIG_SYN_COOKIES
7004 if (syncookies) {
7005 msg = "Sending cookies";
7006 want_cookie = true;
7007 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDOCOOKIES);
7008 } else
7009#endif
7010 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
7011
7012 if (!READ_ONCE(queue->synflood_warned) && syncookies != 2 &&
7013 xchg(&queue->synflood_warned, 1) == 0) {
7014 if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
7015 net_info_ratelimited("%s: Possible SYN flooding on port [%pI6c]:%u. %s.\n",
7016 proto, inet6_rcv_saddr(sk),
7017 sk->sk_num, msg);
7018 } else {
7019 net_info_ratelimited("%s: Possible SYN flooding on port %pI4:%u. %s.\n",
7020 proto, &sk->sk_rcv_saddr,
7021 sk->sk_num, msg);
7022 }
7023 }
7024
7025 return want_cookie;
7026}
7027
7028static void tcp_reqsk_record_syn(const struct sock *sk,
7029 struct request_sock *req,
7030 const struct sk_buff *skb)
7031{
7032 if (tcp_sk(sk)->save_syn) {
7033 u32 len = skb_network_header_len(skb) + tcp_hdrlen(skb);
7034 struct saved_syn *saved_syn;
7035 u32 mac_hdrlen;
7036 void *base;
7037
7038 if (tcp_sk(sk)->save_syn == 2) { /* Save full header. */
7039 base = skb_mac_header(skb);
7040 mac_hdrlen = skb_mac_header_len(skb);
7041 len += mac_hdrlen;
7042 } else {
7043 base = skb_network_header(skb);
7044 mac_hdrlen = 0;
7045 }
7046
7047 saved_syn = kmalloc(struct_size(saved_syn, data, len),
7048 GFP_ATOMIC);
7049 if (saved_syn) {
7050 saved_syn->mac_hdrlen = mac_hdrlen;
7051 saved_syn->network_hdrlen = skb_network_header_len(skb);
7052 saved_syn->tcp_hdrlen = tcp_hdrlen(skb);
7053 memcpy(saved_syn->data, base, len);
7054 req->saved_syn = saved_syn;
7055 }
7056 }
7057}
7058
7059/* If a SYN cookie is required and supported, returns a clamped MSS value to be
7060 * used for SYN cookie generation.
7061 */
7062u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
7063 const struct tcp_request_sock_ops *af_ops,
7064 struct sock *sk, struct tcphdr *th)
7065{
7066 struct tcp_sock *tp = tcp_sk(sk);
7067 u16 mss;
7068
7069 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_syncookies) != 2 &&
7070 !inet_csk_reqsk_queue_is_full(sk))
7071 return 0;
7072
7073 if (!tcp_syn_flood_action(sk, rsk_ops->slab_name))
7074 return 0;
7075
7076 if (sk_acceptq_is_full(sk)) {
7077 NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
7078 return 0;
7079 }
7080
7081 mss = tcp_parse_mss_option(th, tp->rx_opt.user_mss);
7082 if (!mss)
7083 mss = af_ops->mss_clamp;
7084
7085 return mss;
7086}
7087EXPORT_SYMBOL_GPL(tcp_get_syncookie_mss);
7088
7089int tcp_conn_request(struct request_sock_ops *rsk_ops,
7090 const struct tcp_request_sock_ops *af_ops,
7091 struct sock *sk, struct sk_buff *skb)
7092{
7093 struct tcp_fastopen_cookie foc = { .len = -1 };
7094 __u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
7095 struct tcp_options_received tmp_opt;
7096 struct tcp_sock *tp = tcp_sk(sk);
7097 struct net *net = sock_net(sk);
7098 struct sock *fastopen_sk = NULL;
7099 struct request_sock *req;
7100 bool want_cookie = false;
7101 struct dst_entry *dst;
7102 struct flowi fl;
7103 u8 syncookies;
7104
7105#ifdef CONFIG_TCP_AO
7106 const struct tcp_ao_hdr *aoh;
7107#endif
7108
7109 syncookies = READ_ONCE(net->ipv4.sysctl_tcp_syncookies);
7110
7111 /* TW buckets are converted to open requests without
7112 * limitations, they conserve resources and peer is
7113 * evidently real one.
7114 */
7115 if ((syncookies == 2 || inet_csk_reqsk_queue_is_full(sk)) && !isn) {
7116 want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name);
7117 if (!want_cookie)
7118 goto drop;
7119 }
7120
7121 if (sk_acceptq_is_full(sk)) {
7122 NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
7123 goto drop;
7124 }
7125
7126 req = inet_reqsk_alloc(rsk_ops, sk, !want_cookie);
7127 if (!req)
7128 goto drop;
7129
7130 req->syncookie = want_cookie;
7131 tcp_rsk(req)->af_specific = af_ops;
7132 tcp_rsk(req)->ts_off = 0;
7133 tcp_rsk(req)->req_usec_ts = false;
7134#if IS_ENABLED(CONFIG_MPTCP)
7135 tcp_rsk(req)->is_mptcp = 0;
7136#endif
7137
7138 tcp_clear_options(&tmp_opt);
7139 tmp_opt.mss_clamp = af_ops->mss_clamp;
7140 tmp_opt.user_mss = tp->rx_opt.user_mss;
7141 tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0,
7142 want_cookie ? NULL : &foc);
7143
7144 if (want_cookie && !tmp_opt.saw_tstamp)
7145 tcp_clear_options(&tmp_opt);
7146
7147 if (IS_ENABLED(CONFIG_SMC) && want_cookie)
7148 tmp_opt.smc_ok = 0;
7149
7150 tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
7151 tcp_openreq_init(req, &tmp_opt, skb, sk);
7152 inet_rsk(req)->no_srccheck = inet_test_bit(TRANSPARENT, sk);
7153
7154 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
7155 inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb);
7156
7157 dst = af_ops->route_req(sk, skb, &fl, req);
7158 if (!dst)
7159 goto drop_and_free;
7160
7161 if (tmp_opt.tstamp_ok) {
7162 tcp_rsk(req)->req_usec_ts = dst_tcp_usec_ts(dst);
7163 tcp_rsk(req)->ts_off = af_ops->init_ts_off(net, skb);
7164 }
7165 if (!want_cookie && !isn) {
7166 int max_syn_backlog = READ_ONCE(net->ipv4.sysctl_max_syn_backlog);
7167
7168 /* Kill the following clause, if you dislike this way. */
7169 if (!syncookies &&
7170 (max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
7171 (max_syn_backlog >> 2)) &&
7172 !tcp_peer_is_proven(req, dst)) {
7173 /* Without syncookies last quarter of
7174 * backlog is filled with destinations,
7175 * proven to be alive.
7176 * It means that we continue to communicate
7177 * to destinations, already remembered
7178 * to the moment of synflood.
7179 */
7180 pr_drop_req(req, ntohs(tcp_hdr(skb)->source),
7181 rsk_ops->family);
7182 goto drop_and_release;
7183 }
7184
7185 isn = af_ops->init_seq(skb);
7186 }
7187
7188 tcp_ecn_create_request(req, skb, sk, dst);
7189
7190 if (want_cookie) {
7191 isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
7192 if (!tmp_opt.tstamp_ok)
7193 inet_rsk(req)->ecn_ok = 0;
7194 }
7195
7196#ifdef CONFIG_TCP_AO
7197 if (tcp_parse_auth_options(tcp_hdr(skb), NULL, &aoh))
7198 goto drop_and_release; /* Invalid TCP options */
7199 if (aoh) {
7200 tcp_rsk(req)->used_tcp_ao = true;
7201 tcp_rsk(req)->ao_rcv_next = aoh->keyid;
7202 tcp_rsk(req)->ao_keyid = aoh->rnext_keyid;
7203
7204 } else {
7205 tcp_rsk(req)->used_tcp_ao = false;
7206 }
7207#endif
7208 tcp_rsk(req)->snt_isn = isn;
7209 tcp_rsk(req)->txhash = net_tx_rndhash();
7210 tcp_rsk(req)->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
7211 tcp_openreq_init_rwin(req, sk, dst);
7212 sk_rx_queue_set(req_to_sk(req), skb);
7213 if (!want_cookie) {
7214 tcp_reqsk_record_syn(sk, req, skb);
7215 fastopen_sk = tcp_try_fastopen(sk, skb, req, &foc, dst);
7216 }
7217 if (fastopen_sk) {
7218 af_ops->send_synack(fastopen_sk, dst, &fl, req,
7219 &foc, TCP_SYNACK_FASTOPEN, skb);
7220 /* Add the child socket directly into the accept queue */
7221 if (!inet_csk_reqsk_queue_add(sk, req, fastopen_sk)) {
7222 reqsk_fastopen_remove(fastopen_sk, req, false);
7223 bh_unlock_sock(fastopen_sk);
7224 sock_put(fastopen_sk);
7225 goto drop_and_free;
7226 }
7227 sk->sk_data_ready(sk);
7228 bh_unlock_sock(fastopen_sk);
7229 sock_put(fastopen_sk);
7230 } else {
7231 tcp_rsk(req)->tfo_listener = false;
7232 if (!want_cookie) {
7233 req->timeout = tcp_timeout_init((struct sock *)req);
7234 inet_csk_reqsk_queue_hash_add(sk, req, req->timeout);
7235 }
7236 af_ops->send_synack(sk, dst, &fl, req, &foc,
7237 !want_cookie ? TCP_SYNACK_NORMAL :
7238 TCP_SYNACK_COOKIE,
7239 skb);
7240 if (want_cookie) {
7241 reqsk_free(req);
7242 return 0;
7243 }
7244 }
7245 reqsk_put(req);
7246 return 0;
7247
7248drop_and_release:
7249 dst_release(dst);
7250drop_and_free:
7251 __reqsk_free(req);
7252drop:
7253 tcp_listendrop(sk);
7254 return 0;
7255}
7256EXPORT_SYMBOL(tcp_conn_request);
1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Authors: Ross Biro
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
19 */
20
21/*
22 * Changes:
23 * Pedro Roque : Fast Retransmit/Recovery.
24 * Two receive queues.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
28 * Header prediction.
29 * Variable renaming.
30 *
31 * Eric : Fast Retransmit.
32 * Randy Scott : MSS option defines.
33 * Eric Schenk : Fixes to slow start algorithm.
34 * Eric Schenk : Yet another double ACK bug.
35 * Eric Schenk : Delayed ACK bug fixes.
36 * Eric Schenk : Floyd style fast retrans war avoidance.
37 * David S. Miller : Don't allow zero congestion window.
38 * Eric Schenk : Fix retransmitter so that it sends
39 * next packet on ack of previous packet.
40 * Andi Kleen : Moved open_request checking here
41 * and process RSTs for open_requests.
42 * Andi Kleen : Better prune_queue, and other fixes.
43 * Andrey Savochkin: Fix RTT measurements in the presence of
44 * timestamps.
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
47 * data segments.
48 * Andi Kleen: Make sure we never ack data there is not
49 * enough room for. Also make this condition
50 * a fatal error if it might still happen.
51 * Andi Kleen: Add tcp_measure_rcv_mss to make
52 * connections with MSS<min(MTU,ann. MSS)
53 * work without delayed acks.
54 * Andi Kleen: Process packets with PSH set in the
55 * fast path.
56 * J Hadi Salim: ECN support
57 * Andrei Gurtov,
58 * Pasi Sarolahti,
59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
60 * engine. Lots of bugs are found.
61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
62 */
63
64#define pr_fmt(fmt) "TCP: " fmt
65
66#include <linux/mm.h>
67#include <linux/slab.h>
68#include <linux/module.h>
69#include <linux/sysctl.h>
70#include <linux/kernel.h>
71#include <net/dst.h>
72#include <net/tcp.h>
73#include <net/inet_common.h>
74#include <linux/ipsec.h>
75#include <asm/unaligned.h>
76#include <net/netdma.h>
77
78int sysctl_tcp_timestamps __read_mostly = 1;
79int sysctl_tcp_window_scaling __read_mostly = 1;
80int sysctl_tcp_sack __read_mostly = 1;
81int sysctl_tcp_fack __read_mostly = 1;
82int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
83EXPORT_SYMBOL(sysctl_tcp_reordering);
84int sysctl_tcp_dsack __read_mostly = 1;
85int sysctl_tcp_app_win __read_mostly = 31;
86int sysctl_tcp_adv_win_scale __read_mostly = 1;
87EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
88
89/* rfc5961 challenge ack rate limiting */
90int sysctl_tcp_challenge_ack_limit = 100;
91
92int sysctl_tcp_stdurg __read_mostly;
93int sysctl_tcp_rfc1337 __read_mostly;
94int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
95int sysctl_tcp_frto __read_mostly = 2;
96
97int sysctl_tcp_thin_dupack __read_mostly;
98
99int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
100int sysctl_tcp_early_retrans __read_mostly = 3;
101
102#define FLAG_DATA 0x01 /* Incoming frame contained data. */
103#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
104#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
105#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
106#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
107#define FLAG_DATA_SACKED 0x20 /* New SACK. */
108#define FLAG_ECE 0x40 /* ECE in this ACK */
109#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
110#define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
111#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
112#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
113#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
114#define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
115
116#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
117#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
118#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
119#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
120
121#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
122#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
123
124/* Adapt the MSS value used to make delayed ack decision to the
125 * real world.
126 */
127static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
128{
129 struct inet_connection_sock *icsk = inet_csk(sk);
130 const unsigned int lss = icsk->icsk_ack.last_seg_size;
131 unsigned int len;
132
133 icsk->icsk_ack.last_seg_size = 0;
134
135 /* skb->len may jitter because of SACKs, even if peer
136 * sends good full-sized frames.
137 */
138 len = skb_shinfo(skb)->gso_size ? : skb->len;
139 if (len >= icsk->icsk_ack.rcv_mss) {
140 icsk->icsk_ack.rcv_mss = len;
141 } else {
142 /* Otherwise, we make more careful check taking into account,
143 * that SACKs block is variable.
144 *
145 * "len" is invariant segment length, including TCP header.
146 */
147 len += skb->data - skb_transport_header(skb);
148 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) ||
149 /* If PSH is not set, packet should be
150 * full sized, provided peer TCP is not badly broken.
151 * This observation (if it is correct 8)) allows
152 * to handle super-low mtu links fairly.
153 */
154 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
155 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
156 /* Subtract also invariant (if peer is RFC compliant),
157 * tcp header plus fixed timestamp option length.
158 * Resulting "len" is MSS free of SACK jitter.
159 */
160 len -= tcp_sk(sk)->tcp_header_len;
161 icsk->icsk_ack.last_seg_size = len;
162 if (len == lss) {
163 icsk->icsk_ack.rcv_mss = len;
164 return;
165 }
166 }
167 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
168 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
169 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
170 }
171}
172
173static void tcp_incr_quickack(struct sock *sk)
174{
175 struct inet_connection_sock *icsk = inet_csk(sk);
176 unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
177
178 if (quickacks == 0)
179 quickacks = 2;
180 if (quickacks > icsk->icsk_ack.quick)
181 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
182}
183
184static void tcp_enter_quickack_mode(struct sock *sk)
185{
186 struct inet_connection_sock *icsk = inet_csk(sk);
187 tcp_incr_quickack(sk);
188 icsk->icsk_ack.pingpong = 0;
189 icsk->icsk_ack.ato = TCP_ATO_MIN;
190}
191
192/* Send ACKs quickly, if "quick" count is not exhausted
193 * and the session is not interactive.
194 */
195
196static inline bool tcp_in_quickack_mode(const struct sock *sk)
197{
198 const struct inet_connection_sock *icsk = inet_csk(sk);
199
200 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
201}
202
203static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp)
204{
205 if (tp->ecn_flags & TCP_ECN_OK)
206 tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
207}
208
209static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb)
210{
211 if (tcp_hdr(skb)->cwr)
212 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
213}
214
215static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp)
216{
217 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
218}
219
220static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *skb)
221{
222 if (!(tp->ecn_flags & TCP_ECN_OK))
223 return;
224
225 switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) {
226 case INET_ECN_NOT_ECT:
227 /* Funny extension: if ECT is not set on a segment,
228 * and we already seen ECT on a previous segment,
229 * it is probably a retransmit.
230 */
231 if (tp->ecn_flags & TCP_ECN_SEEN)
232 tcp_enter_quickack_mode((struct sock *)tp);
233 break;
234 case INET_ECN_CE:
235 if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {
236 /* Better not delay acks, sender can have a very low cwnd */
237 tcp_enter_quickack_mode((struct sock *)tp);
238 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
239 }
240 /* fallinto */
241 default:
242 tp->ecn_flags |= TCP_ECN_SEEN;
243 }
244}
245
246static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th)
247{
248 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
249 tp->ecn_flags &= ~TCP_ECN_OK;
250}
251
252static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th)
253{
254 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
255 tp->ecn_flags &= ~TCP_ECN_OK;
256}
257
258static bool TCP_ECN_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th)
259{
260 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
261 return true;
262 return false;
263}
264
265/* Buffer size and advertised window tuning.
266 *
267 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
268 */
269
270static void tcp_sndbuf_expand(struct sock *sk)
271{
272 const struct tcp_sock *tp = tcp_sk(sk);
273 int sndmem, per_mss;
274 u32 nr_segs;
275
276 /* Worst case is non GSO/TSO : each frame consumes one skb
277 * and skb->head is kmalloced using power of two area of memory
278 */
279 per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
280 MAX_TCP_HEADER +
281 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
282
283 per_mss = roundup_pow_of_two(per_mss) +
284 SKB_DATA_ALIGN(sizeof(struct sk_buff));
285
286 nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd);
287 nr_segs = max_t(u32, nr_segs, tp->reordering + 1);
288
289 /* Fast Recovery (RFC 5681 3.2) :
290 * Cubic needs 1.7 factor, rounded to 2 to include
291 * extra cushion (application might react slowly to POLLOUT)
292 */
293 sndmem = 2 * nr_segs * per_mss;
294
295 if (sk->sk_sndbuf < sndmem)
296 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
297}
298
299/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
300 *
301 * All tcp_full_space() is split to two parts: "network" buffer, allocated
302 * forward and advertised in receiver window (tp->rcv_wnd) and
303 * "application buffer", required to isolate scheduling/application
304 * latencies from network.
305 * window_clamp is maximal advertised window. It can be less than
306 * tcp_full_space(), in this case tcp_full_space() - window_clamp
307 * is reserved for "application" buffer. The less window_clamp is
308 * the smoother our behaviour from viewpoint of network, but the lower
309 * throughput and the higher sensitivity of the connection to losses. 8)
310 *
311 * rcv_ssthresh is more strict window_clamp used at "slow start"
312 * phase to predict further behaviour of this connection.
313 * It is used for two goals:
314 * - to enforce header prediction at sender, even when application
315 * requires some significant "application buffer". It is check #1.
316 * - to prevent pruning of receive queue because of misprediction
317 * of receiver window. Check #2.
318 *
319 * The scheme does not work when sender sends good segments opening
320 * window and then starts to feed us spaghetti. But it should work
321 * in common situations. Otherwise, we have to rely on queue collapsing.
322 */
323
324/* Slow part of check#2. */
325static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
326{
327 struct tcp_sock *tp = tcp_sk(sk);
328 /* Optimize this! */
329 int truesize = tcp_win_from_space(skb->truesize) >> 1;
330 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1;
331
332 while (tp->rcv_ssthresh <= window) {
333 if (truesize <= skb->len)
334 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
335
336 truesize >>= 1;
337 window >>= 1;
338 }
339 return 0;
340}
341
342static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
343{
344 struct tcp_sock *tp = tcp_sk(sk);
345
346 /* Check #1 */
347 if (tp->rcv_ssthresh < tp->window_clamp &&
348 (int)tp->rcv_ssthresh < tcp_space(sk) &&
349 !sk_under_memory_pressure(sk)) {
350 int incr;
351
352 /* Check #2. Increase window, if skb with such overhead
353 * will fit to rcvbuf in future.
354 */
355 if (tcp_win_from_space(skb->truesize) <= skb->len)
356 incr = 2 * tp->advmss;
357 else
358 incr = __tcp_grow_window(sk, skb);
359
360 if (incr) {
361 incr = max_t(int, incr, 2 * skb->len);
362 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr,
363 tp->window_clamp);
364 inet_csk(sk)->icsk_ack.quick |= 1;
365 }
366 }
367}
368
369/* 3. Tuning rcvbuf, when connection enters established state. */
370static void tcp_fixup_rcvbuf(struct sock *sk)
371{
372 u32 mss = tcp_sk(sk)->advmss;
373 int rcvmem;
374
375 rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) *
376 tcp_default_init_rwnd(mss);
377
378 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
379 * Allow enough cushion so that sender is not limited by our window
380 */
381 if (sysctl_tcp_moderate_rcvbuf)
382 rcvmem <<= 2;
383
384 if (sk->sk_rcvbuf < rcvmem)
385 sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]);
386}
387
388/* 4. Try to fixup all. It is made immediately after connection enters
389 * established state.
390 */
391void tcp_init_buffer_space(struct sock *sk)
392{
393 struct tcp_sock *tp = tcp_sk(sk);
394 int maxwin;
395
396 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
397 tcp_fixup_rcvbuf(sk);
398 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
399 tcp_sndbuf_expand(sk);
400
401 tp->rcvq_space.space = tp->rcv_wnd;
402 tp->rcvq_space.time = tcp_time_stamp;
403 tp->rcvq_space.seq = tp->copied_seq;
404
405 maxwin = tcp_full_space(sk);
406
407 if (tp->window_clamp >= maxwin) {
408 tp->window_clamp = maxwin;
409
410 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
411 tp->window_clamp = max(maxwin -
412 (maxwin >> sysctl_tcp_app_win),
413 4 * tp->advmss);
414 }
415
416 /* Force reservation of one segment. */
417 if (sysctl_tcp_app_win &&
418 tp->window_clamp > 2 * tp->advmss &&
419 tp->window_clamp + tp->advmss > maxwin)
420 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
421
422 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
423 tp->snd_cwnd_stamp = tcp_time_stamp;
424}
425
426/* 5. Recalculate window clamp after socket hit its memory bounds. */
427static void tcp_clamp_window(struct sock *sk)
428{
429 struct tcp_sock *tp = tcp_sk(sk);
430 struct inet_connection_sock *icsk = inet_csk(sk);
431
432 icsk->icsk_ack.quick = 0;
433
434 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
435 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
436 !sk_under_memory_pressure(sk) &&
437 sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) {
438 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
439 sysctl_tcp_rmem[2]);
440 }
441 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
442 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
443}
444
445/* Initialize RCV_MSS value.
446 * RCV_MSS is an our guess about MSS used by the peer.
447 * We haven't any direct information about the MSS.
448 * It's better to underestimate the RCV_MSS rather than overestimate.
449 * Overestimations make us ACKing less frequently than needed.
450 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
451 */
452void tcp_initialize_rcv_mss(struct sock *sk)
453{
454 const struct tcp_sock *tp = tcp_sk(sk);
455 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
456
457 hint = min(hint, tp->rcv_wnd / 2);
458 hint = min(hint, TCP_MSS_DEFAULT);
459 hint = max(hint, TCP_MIN_MSS);
460
461 inet_csk(sk)->icsk_ack.rcv_mss = hint;
462}
463EXPORT_SYMBOL(tcp_initialize_rcv_mss);
464
465/* Receiver "autotuning" code.
466 *
467 * The algorithm for RTT estimation w/o timestamps is based on
468 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
469 * <http://public.lanl.gov/radiant/pubs.html#DRS>
470 *
471 * More detail on this code can be found at
472 * <http://staff.psc.edu/jheffner/>,
473 * though this reference is out of date. A new paper
474 * is pending.
475 */
476static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
477{
478 u32 new_sample = tp->rcv_rtt_est.rtt;
479 long m = sample;
480
481 if (m == 0)
482 m = 1;
483
484 if (new_sample != 0) {
485 /* If we sample in larger samples in the non-timestamp
486 * case, we could grossly overestimate the RTT especially
487 * with chatty applications or bulk transfer apps which
488 * are stalled on filesystem I/O.
489 *
490 * Also, since we are only going for a minimum in the
491 * non-timestamp case, we do not smooth things out
492 * else with timestamps disabled convergence takes too
493 * long.
494 */
495 if (!win_dep) {
496 m -= (new_sample >> 3);
497 new_sample += m;
498 } else {
499 m <<= 3;
500 if (m < new_sample)
501 new_sample = m;
502 }
503 } else {
504 /* No previous measure. */
505 new_sample = m << 3;
506 }
507
508 if (tp->rcv_rtt_est.rtt != new_sample)
509 tp->rcv_rtt_est.rtt = new_sample;
510}
511
512static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
513{
514 if (tp->rcv_rtt_est.time == 0)
515 goto new_measure;
516 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
517 return;
518 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rcv_rtt_est.time, 1);
519
520new_measure:
521 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
522 tp->rcv_rtt_est.time = tcp_time_stamp;
523}
524
525static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
526 const struct sk_buff *skb)
527{
528 struct tcp_sock *tp = tcp_sk(sk);
529 if (tp->rx_opt.rcv_tsecr &&
530 (TCP_SKB_CB(skb)->end_seq -
531 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
532 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
533}
534
535/*
536 * This function should be called every time data is copied to user space.
537 * It calculates the appropriate TCP receive buffer space.
538 */
539void tcp_rcv_space_adjust(struct sock *sk)
540{
541 struct tcp_sock *tp = tcp_sk(sk);
542 int time;
543 int copied;
544
545 time = tcp_time_stamp - tp->rcvq_space.time;
546 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
547 return;
548
549 /* Number of bytes copied to user in last RTT */
550 copied = tp->copied_seq - tp->rcvq_space.seq;
551 if (copied <= tp->rcvq_space.space)
552 goto new_measure;
553
554 /* A bit of theory :
555 * copied = bytes received in previous RTT, our base window
556 * To cope with packet losses, we need a 2x factor
557 * To cope with slow start, and sender growing its cwin by 100 %
558 * every RTT, we need a 4x factor, because the ACK we are sending
559 * now is for the next RTT, not the current one :
560 * <prev RTT . ><current RTT .. ><next RTT .... >
561 */
562
563 if (sysctl_tcp_moderate_rcvbuf &&
564 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
565 int rcvwin, rcvmem, rcvbuf;
566
567 /* minimal window to cope with packet losses, assuming
568 * steady state. Add some cushion because of small variations.
569 */
570 rcvwin = (copied << 1) + 16 * tp->advmss;
571
572 /* If rate increased by 25%,
573 * assume slow start, rcvwin = 3 * copied
574 * If rate increased by 50%,
575 * assume sender can use 2x growth, rcvwin = 4 * copied
576 */
577 if (copied >=
578 tp->rcvq_space.space + (tp->rcvq_space.space >> 2)) {
579 if (copied >=
580 tp->rcvq_space.space + (tp->rcvq_space.space >> 1))
581 rcvwin <<= 1;
582 else
583 rcvwin += (rcvwin >> 1);
584 }
585
586 rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER);
587 while (tcp_win_from_space(rcvmem) < tp->advmss)
588 rcvmem += 128;
589
590 rcvbuf = min(rcvwin / tp->advmss * rcvmem, sysctl_tcp_rmem[2]);
591 if (rcvbuf > sk->sk_rcvbuf) {
592 sk->sk_rcvbuf = rcvbuf;
593
594 /* Make the window clamp follow along. */
595 tp->window_clamp = rcvwin;
596 }
597 }
598 tp->rcvq_space.space = copied;
599
600new_measure:
601 tp->rcvq_space.seq = tp->copied_seq;
602 tp->rcvq_space.time = tcp_time_stamp;
603}
604
605/* There is something which you must keep in mind when you analyze the
606 * behavior of the tp->ato delayed ack timeout interval. When a
607 * connection starts up, we want to ack as quickly as possible. The
608 * problem is that "good" TCP's do slow start at the beginning of data
609 * transmission. The means that until we send the first few ACK's the
610 * sender will sit on his end and only queue most of his data, because
611 * he can only send snd_cwnd unacked packets at any given time. For
612 * each ACK we send, he increments snd_cwnd and transmits more of his
613 * queue. -DaveM
614 */
615static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
616{
617 struct tcp_sock *tp = tcp_sk(sk);
618 struct inet_connection_sock *icsk = inet_csk(sk);
619 u32 now;
620
621 inet_csk_schedule_ack(sk);
622
623 tcp_measure_rcv_mss(sk, skb);
624
625 tcp_rcv_rtt_measure(tp);
626
627 now = tcp_time_stamp;
628
629 if (!icsk->icsk_ack.ato) {
630 /* The _first_ data packet received, initialize
631 * delayed ACK engine.
632 */
633 tcp_incr_quickack(sk);
634 icsk->icsk_ack.ato = TCP_ATO_MIN;
635 } else {
636 int m = now - icsk->icsk_ack.lrcvtime;
637
638 if (m <= TCP_ATO_MIN / 2) {
639 /* The fastest case is the first. */
640 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
641 } else if (m < icsk->icsk_ack.ato) {
642 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
643 if (icsk->icsk_ack.ato > icsk->icsk_rto)
644 icsk->icsk_ack.ato = icsk->icsk_rto;
645 } else if (m > icsk->icsk_rto) {
646 /* Too long gap. Apparently sender failed to
647 * restart window, so that we send ACKs quickly.
648 */
649 tcp_incr_quickack(sk);
650 sk_mem_reclaim(sk);
651 }
652 }
653 icsk->icsk_ack.lrcvtime = now;
654
655 TCP_ECN_check_ce(tp, skb);
656
657 if (skb->len >= 128)
658 tcp_grow_window(sk, skb);
659}
660
661/* Called to compute a smoothed rtt estimate. The data fed to this
662 * routine either comes from timestamps, or from segments that were
663 * known _not_ to have been retransmitted [see Karn/Partridge
664 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
665 * piece by Van Jacobson.
666 * NOTE: the next three routines used to be one big routine.
667 * To save cycles in the RFC 1323 implementation it was better to break
668 * it up into three procedures. -- erics
669 */
670static void tcp_rtt_estimator(struct sock *sk, long mrtt_us)
671{
672 struct tcp_sock *tp = tcp_sk(sk);
673 long m = mrtt_us; /* RTT */
674 u32 srtt = tp->srtt_us;
675
676 /* The following amusing code comes from Jacobson's
677 * article in SIGCOMM '88. Note that rtt and mdev
678 * are scaled versions of rtt and mean deviation.
679 * This is designed to be as fast as possible
680 * m stands for "measurement".
681 *
682 * On a 1990 paper the rto value is changed to:
683 * RTO = rtt + 4 * mdev
684 *
685 * Funny. This algorithm seems to be very broken.
686 * These formulae increase RTO, when it should be decreased, increase
687 * too slowly, when it should be increased quickly, decrease too quickly
688 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
689 * does not matter how to _calculate_ it. Seems, it was trap
690 * that VJ failed to avoid. 8)
691 */
692 if (srtt != 0) {
693 m -= (srtt >> 3); /* m is now error in rtt est */
694 srtt += m; /* rtt = 7/8 rtt + 1/8 new */
695 if (m < 0) {
696 m = -m; /* m is now abs(error) */
697 m -= (tp->mdev_us >> 2); /* similar update on mdev */
698 /* This is similar to one of Eifel findings.
699 * Eifel blocks mdev updates when rtt decreases.
700 * This solution is a bit different: we use finer gain
701 * for mdev in this case (alpha*beta).
702 * Like Eifel it also prevents growth of rto,
703 * but also it limits too fast rto decreases,
704 * happening in pure Eifel.
705 */
706 if (m > 0)
707 m >>= 3;
708 } else {
709 m -= (tp->mdev_us >> 2); /* similar update on mdev */
710 }
711 tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */
712 if (tp->mdev_us > tp->mdev_max_us) {
713 tp->mdev_max_us = tp->mdev_us;
714 if (tp->mdev_max_us > tp->rttvar_us)
715 tp->rttvar_us = tp->mdev_max_us;
716 }
717 if (after(tp->snd_una, tp->rtt_seq)) {
718 if (tp->mdev_max_us < tp->rttvar_us)
719 tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2;
720 tp->rtt_seq = tp->snd_nxt;
721 tp->mdev_max_us = tcp_rto_min_us(sk);
722 }
723 } else {
724 /* no previous measure. */
725 srtt = m << 3; /* take the measured time to be rtt */
726 tp->mdev_us = m << 1; /* make sure rto = 3*rtt */
727 tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk));
728 tp->mdev_max_us = tp->rttvar_us;
729 tp->rtt_seq = tp->snd_nxt;
730 }
731 tp->srtt_us = max(1U, srtt);
732}
733
734/* Set the sk_pacing_rate to allow proper sizing of TSO packets.
735 * Note: TCP stack does not yet implement pacing.
736 * FQ packet scheduler can be used to implement cheap but effective
737 * TCP pacing, to smooth the burst on large writes when packets
738 * in flight is significantly lower than cwnd (or rwin)
739 */
740static void tcp_update_pacing_rate(struct sock *sk)
741{
742 const struct tcp_sock *tp = tcp_sk(sk);
743 u64 rate;
744
745 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
746 rate = (u64)tp->mss_cache * 2 * (USEC_PER_SEC << 3);
747
748 rate *= max(tp->snd_cwnd, tp->packets_out);
749
750 if (likely(tp->srtt_us))
751 do_div(rate, tp->srtt_us);
752
753 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
754 * without any lock. We want to make sure compiler wont store
755 * intermediate values in this location.
756 */
757 ACCESS_ONCE(sk->sk_pacing_rate) = min_t(u64, rate,
758 sk->sk_max_pacing_rate);
759}
760
761/* Calculate rto without backoff. This is the second half of Van Jacobson's
762 * routine referred to above.
763 */
764static void tcp_set_rto(struct sock *sk)
765{
766 const struct tcp_sock *tp = tcp_sk(sk);
767 /* Old crap is replaced with new one. 8)
768 *
769 * More seriously:
770 * 1. If rtt variance happened to be less 50msec, it is hallucination.
771 * It cannot be less due to utterly erratic ACK generation made
772 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
773 * to do with delayed acks, because at cwnd>2 true delack timeout
774 * is invisible. Actually, Linux-2.4 also generates erratic
775 * ACKs in some circumstances.
776 */
777 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp);
778
779 /* 2. Fixups made earlier cannot be right.
780 * If we do not estimate RTO correctly without them,
781 * all the algo is pure shit and should be replaced
782 * with correct one. It is exactly, which we pretend to do.
783 */
784
785 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
786 * guarantees that rto is higher.
787 */
788 tcp_bound_rto(sk);
789}
790
791__u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst)
792{
793 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
794
795 if (!cwnd)
796 cwnd = TCP_INIT_CWND;
797 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
798}
799
800/*
801 * Packet counting of FACK is based on in-order assumptions, therefore TCP
802 * disables it when reordering is detected
803 */
804void tcp_disable_fack(struct tcp_sock *tp)
805{
806 /* RFC3517 uses different metric in lost marker => reset on change */
807 if (tcp_is_fack(tp))
808 tp->lost_skb_hint = NULL;
809 tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED;
810}
811
812/* Take a notice that peer is sending D-SACKs */
813static void tcp_dsack_seen(struct tcp_sock *tp)
814{
815 tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
816}
817
818static void tcp_update_reordering(struct sock *sk, const int metric,
819 const int ts)
820{
821 struct tcp_sock *tp = tcp_sk(sk);
822 if (metric > tp->reordering) {
823 int mib_idx;
824
825 tp->reordering = min(TCP_MAX_REORDERING, metric);
826
827 /* This exciting event is worth to be remembered. 8) */
828 if (ts)
829 mib_idx = LINUX_MIB_TCPTSREORDER;
830 else if (tcp_is_reno(tp))
831 mib_idx = LINUX_MIB_TCPRENOREORDER;
832 else if (tcp_is_fack(tp))
833 mib_idx = LINUX_MIB_TCPFACKREORDER;
834 else
835 mib_idx = LINUX_MIB_TCPSACKREORDER;
836
837 NET_INC_STATS_BH(sock_net(sk), mib_idx);
838#if FASTRETRANS_DEBUG > 1
839 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
840 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
841 tp->reordering,
842 tp->fackets_out,
843 tp->sacked_out,
844 tp->undo_marker ? tp->undo_retrans : 0);
845#endif
846 tcp_disable_fack(tp);
847 }
848
849 if (metric > 0)
850 tcp_disable_early_retrans(tp);
851}
852
853/* This must be called before lost_out is incremented */
854static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
855{
856 if ((tp->retransmit_skb_hint == NULL) ||
857 before(TCP_SKB_CB(skb)->seq,
858 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
859 tp->retransmit_skb_hint = skb;
860
861 if (!tp->lost_out ||
862 after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))
863 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
864}
865
866static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
867{
868 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
869 tcp_verify_retransmit_hint(tp, skb);
870
871 tp->lost_out += tcp_skb_pcount(skb);
872 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
873 }
874}
875
876static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,
877 struct sk_buff *skb)
878{
879 tcp_verify_retransmit_hint(tp, skb);
880
881 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
882 tp->lost_out += tcp_skb_pcount(skb);
883 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
884 }
885}
886
887/* This procedure tags the retransmission queue when SACKs arrive.
888 *
889 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
890 * Packets in queue with these bits set are counted in variables
891 * sacked_out, retrans_out and lost_out, correspondingly.
892 *
893 * Valid combinations are:
894 * Tag InFlight Description
895 * 0 1 - orig segment is in flight.
896 * S 0 - nothing flies, orig reached receiver.
897 * L 0 - nothing flies, orig lost by net.
898 * R 2 - both orig and retransmit are in flight.
899 * L|R 1 - orig is lost, retransmit is in flight.
900 * S|R 1 - orig reached receiver, retrans is still in flight.
901 * (L|S|R is logically valid, it could occur when L|R is sacked,
902 * but it is equivalent to plain S and code short-curcuits it to S.
903 * L|S is logically invalid, it would mean -1 packet in flight 8))
904 *
905 * These 6 states form finite state machine, controlled by the following events:
906 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
907 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
908 * 3. Loss detection event of two flavors:
909 * A. Scoreboard estimator decided the packet is lost.
910 * A'. Reno "three dupacks" marks head of queue lost.
911 * A''. Its FACK modification, head until snd.fack is lost.
912 * B. SACK arrives sacking SND.NXT at the moment, when the
913 * segment was retransmitted.
914 * 4. D-SACK added new rule: D-SACK changes any tag to S.
915 *
916 * It is pleasant to note, that state diagram turns out to be commutative,
917 * so that we are allowed not to be bothered by order of our actions,
918 * when multiple events arrive simultaneously. (see the function below).
919 *
920 * Reordering detection.
921 * --------------------
922 * Reordering metric is maximal distance, which a packet can be displaced
923 * in packet stream. With SACKs we can estimate it:
924 *
925 * 1. SACK fills old hole and the corresponding segment was not
926 * ever retransmitted -> reordering. Alas, we cannot use it
927 * when segment was retransmitted.
928 * 2. The last flaw is solved with D-SACK. D-SACK arrives
929 * for retransmitted and already SACKed segment -> reordering..
930 * Both of these heuristics are not used in Loss state, when we cannot
931 * account for retransmits accurately.
932 *
933 * SACK block validation.
934 * ----------------------
935 *
936 * SACK block range validation checks that the received SACK block fits to
937 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
938 * Note that SND.UNA is not included to the range though being valid because
939 * it means that the receiver is rather inconsistent with itself reporting
940 * SACK reneging when it should advance SND.UNA. Such SACK block this is
941 * perfectly valid, however, in light of RFC2018 which explicitly states
942 * that "SACK block MUST reflect the newest segment. Even if the newest
943 * segment is going to be discarded ...", not that it looks very clever
944 * in case of head skb. Due to potentional receiver driven attacks, we
945 * choose to avoid immediate execution of a walk in write queue due to
946 * reneging and defer head skb's loss recovery to standard loss recovery
947 * procedure that will eventually trigger (nothing forbids us doing this).
948 *
949 * Implements also blockage to start_seq wrap-around. Problem lies in the
950 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
951 * there's no guarantee that it will be before snd_nxt (n). The problem
952 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
953 * wrap (s_w):
954 *
955 * <- outs wnd -> <- wrapzone ->
956 * u e n u_w e_w s n_w
957 * | | | | | | |
958 * |<------------+------+----- TCP seqno space --------------+---------->|
959 * ...-- <2^31 ->| |<--------...
960 * ...---- >2^31 ------>| |<--------...
961 *
962 * Current code wouldn't be vulnerable but it's better still to discard such
963 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
964 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
965 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
966 * equal to the ideal case (infinite seqno space without wrap caused issues).
967 *
968 * With D-SACK the lower bound is extended to cover sequence space below
969 * SND.UNA down to undo_marker, which is the last point of interest. Yet
970 * again, D-SACK block must not to go across snd_una (for the same reason as
971 * for the normal SACK blocks, explained above). But there all simplicity
972 * ends, TCP might receive valid D-SACKs below that. As long as they reside
973 * fully below undo_marker they do not affect behavior in anyway and can
974 * therefore be safely ignored. In rare cases (which are more or less
975 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
976 * fragmentation and packet reordering past skb's retransmission. To consider
977 * them correctly, the acceptable range must be extended even more though
978 * the exact amount is rather hard to quantify. However, tp->max_window can
979 * be used as an exaggerated estimate.
980 */
981static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack,
982 u32 start_seq, u32 end_seq)
983{
984 /* Too far in future, or reversed (interpretation is ambiguous) */
985 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
986 return false;
987
988 /* Nasty start_seq wrap-around check (see comments above) */
989 if (!before(start_seq, tp->snd_nxt))
990 return false;
991
992 /* In outstanding window? ...This is valid exit for D-SACKs too.
993 * start_seq == snd_una is non-sensical (see comments above)
994 */
995 if (after(start_seq, tp->snd_una))
996 return true;
997
998 if (!is_dsack || !tp->undo_marker)
999 return false;
1000
1001 /* ...Then it's D-SACK, and must reside below snd_una completely */
1002 if (after(end_seq, tp->snd_una))
1003 return false;
1004
1005 if (!before(start_seq, tp->undo_marker))
1006 return true;
1007
1008 /* Too old */
1009 if (!after(end_seq, tp->undo_marker))
1010 return false;
1011
1012 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1013 * start_seq < undo_marker and end_seq >= undo_marker.
1014 */
1015 return !before(start_seq, end_seq - tp->max_window);
1016}
1017
1018/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1019 * Event "B". Later note: FACK people cheated me again 8), we have to account
1020 * for reordering! Ugly, but should help.
1021 *
1022 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1023 * less than what is now known to be received by the other end (derived from
1024 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1025 * retransmitted skbs to avoid some costly processing per ACKs.
1026 */
1027static void tcp_mark_lost_retrans(struct sock *sk)
1028{
1029 const struct inet_connection_sock *icsk = inet_csk(sk);
1030 struct tcp_sock *tp = tcp_sk(sk);
1031 struct sk_buff *skb;
1032 int cnt = 0;
1033 u32 new_low_seq = tp->snd_nxt;
1034 u32 received_upto = tcp_highest_sack_seq(tp);
1035
1036 if (!tcp_is_fack(tp) || !tp->retrans_out ||
1037 !after(received_upto, tp->lost_retrans_low) ||
1038 icsk->icsk_ca_state != TCP_CA_Recovery)
1039 return;
1040
1041 tcp_for_write_queue(skb, sk) {
1042 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
1043
1044 if (skb == tcp_send_head(sk))
1045 break;
1046 if (cnt == tp->retrans_out)
1047 break;
1048 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1049 continue;
1050
1051 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
1052 continue;
1053
1054 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1055 * constraint here (see above) but figuring out that at
1056 * least tp->reordering SACK blocks reside between ack_seq
1057 * and received_upto is not easy task to do cheaply with
1058 * the available datastructures.
1059 *
1060 * Whether FACK should check here for tp->reordering segs
1061 * in-between one could argue for either way (it would be
1062 * rather simple to implement as we could count fack_count
1063 * during the walk and do tp->fackets_out - fack_count).
1064 */
1065 if (after(received_upto, ack_seq)) {
1066 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1067 tp->retrans_out -= tcp_skb_pcount(skb);
1068
1069 tcp_skb_mark_lost_uncond_verify(tp, skb);
1070 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
1071 } else {
1072 if (before(ack_seq, new_low_seq))
1073 new_low_seq = ack_seq;
1074 cnt += tcp_skb_pcount(skb);
1075 }
1076 }
1077
1078 if (tp->retrans_out)
1079 tp->lost_retrans_low = new_low_seq;
1080}
1081
1082static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
1083 struct tcp_sack_block_wire *sp, int num_sacks,
1084 u32 prior_snd_una)
1085{
1086 struct tcp_sock *tp = tcp_sk(sk);
1087 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
1088 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
1089 bool dup_sack = false;
1090
1091 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
1092 dup_sack = true;
1093 tcp_dsack_seen(tp);
1094 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV);
1095 } else if (num_sacks > 1) {
1096 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
1097 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
1098
1099 if (!after(end_seq_0, end_seq_1) &&
1100 !before(start_seq_0, start_seq_1)) {
1101 dup_sack = true;
1102 tcp_dsack_seen(tp);
1103 NET_INC_STATS_BH(sock_net(sk),
1104 LINUX_MIB_TCPDSACKOFORECV);
1105 }
1106 }
1107
1108 /* D-SACK for already forgotten data... Do dumb counting. */
1109 if (dup_sack && tp->undo_marker && tp->undo_retrans &&
1110 !after(end_seq_0, prior_snd_una) &&
1111 after(end_seq_0, tp->undo_marker))
1112 tp->undo_retrans--;
1113
1114 return dup_sack;
1115}
1116
1117struct tcp_sacktag_state {
1118 int reord;
1119 int fack_count;
1120 long rtt_us; /* RTT measured by SACKing never-retransmitted data */
1121 int flag;
1122};
1123
1124/* Check if skb is fully within the SACK block. In presence of GSO skbs,
1125 * the incoming SACK may not exactly match but we can find smaller MSS
1126 * aligned portion of it that matches. Therefore we might need to fragment
1127 * which may fail and creates some hassle (caller must handle error case
1128 * returns).
1129 *
1130 * FIXME: this could be merged to shift decision code
1131 */
1132static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
1133 u32 start_seq, u32 end_seq)
1134{
1135 int err;
1136 bool in_sack;
1137 unsigned int pkt_len;
1138 unsigned int mss;
1139
1140 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1141 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1142
1143 if (tcp_skb_pcount(skb) > 1 && !in_sack &&
1144 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1145 mss = tcp_skb_mss(skb);
1146 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1147
1148 if (!in_sack) {
1149 pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
1150 if (pkt_len < mss)
1151 pkt_len = mss;
1152 } else {
1153 pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
1154 if (pkt_len < mss)
1155 return -EINVAL;
1156 }
1157
1158 /* Round if necessary so that SACKs cover only full MSSes
1159 * and/or the remaining small portion (if present)
1160 */
1161 if (pkt_len > mss) {
1162 unsigned int new_len = (pkt_len / mss) * mss;
1163 if (!in_sack && new_len < pkt_len) {
1164 new_len += mss;
1165 if (new_len > skb->len)
1166 return 0;
1167 }
1168 pkt_len = new_len;
1169 }
1170 err = tcp_fragment(sk, skb, pkt_len, mss);
1171 if (err < 0)
1172 return err;
1173 }
1174
1175 return in_sack;
1176}
1177
1178/* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1179static u8 tcp_sacktag_one(struct sock *sk,
1180 struct tcp_sacktag_state *state, u8 sacked,
1181 u32 start_seq, u32 end_seq,
1182 int dup_sack, int pcount,
1183 const struct skb_mstamp *xmit_time)
1184{
1185 struct tcp_sock *tp = tcp_sk(sk);
1186 int fack_count = state->fack_count;
1187
1188 /* Account D-SACK for retransmitted packet. */
1189 if (dup_sack && (sacked & TCPCB_RETRANS)) {
1190 if (tp->undo_marker && tp->undo_retrans &&
1191 after(end_seq, tp->undo_marker))
1192 tp->undo_retrans--;
1193 if (sacked & TCPCB_SACKED_ACKED)
1194 state->reord = min(fack_count, state->reord);
1195 }
1196
1197 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1198 if (!after(end_seq, tp->snd_una))
1199 return sacked;
1200
1201 if (!(sacked & TCPCB_SACKED_ACKED)) {
1202 if (sacked & TCPCB_SACKED_RETRANS) {
1203 /* If the segment is not tagged as lost,
1204 * we do not clear RETRANS, believing
1205 * that retransmission is still in flight.
1206 */
1207 if (sacked & TCPCB_LOST) {
1208 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1209 tp->lost_out -= pcount;
1210 tp->retrans_out -= pcount;
1211 }
1212 } else {
1213 if (!(sacked & TCPCB_RETRANS)) {
1214 /* New sack for not retransmitted frame,
1215 * which was in hole. It is reordering.
1216 */
1217 if (before(start_seq,
1218 tcp_highest_sack_seq(tp)))
1219 state->reord = min(fack_count,
1220 state->reord);
1221 if (!after(end_seq, tp->high_seq))
1222 state->flag |= FLAG_ORIG_SACK_ACKED;
1223 /* Pick the earliest sequence sacked for RTT */
1224 if (state->rtt_us < 0) {
1225 struct skb_mstamp now;
1226
1227 skb_mstamp_get(&now);
1228 state->rtt_us = skb_mstamp_us_delta(&now,
1229 xmit_time);
1230 }
1231 }
1232
1233 if (sacked & TCPCB_LOST) {
1234 sacked &= ~TCPCB_LOST;
1235 tp->lost_out -= pcount;
1236 }
1237 }
1238
1239 sacked |= TCPCB_SACKED_ACKED;
1240 state->flag |= FLAG_DATA_SACKED;
1241 tp->sacked_out += pcount;
1242
1243 fack_count += pcount;
1244
1245 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1246 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
1247 before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq))
1248 tp->lost_cnt_hint += pcount;
1249
1250 if (fack_count > tp->fackets_out)
1251 tp->fackets_out = fack_count;
1252 }
1253
1254 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1255 * frames and clear it. undo_retrans is decreased above, L|R frames
1256 * are accounted above as well.
1257 */
1258 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
1259 sacked &= ~TCPCB_SACKED_RETRANS;
1260 tp->retrans_out -= pcount;
1261 }
1262
1263 return sacked;
1264}
1265
1266/* Shift newly-SACKed bytes from this skb to the immediately previous
1267 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1268 */
1269static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
1270 struct tcp_sacktag_state *state,
1271 unsigned int pcount, int shifted, int mss,
1272 bool dup_sack)
1273{
1274 struct tcp_sock *tp = tcp_sk(sk);
1275 struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
1276 u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */
1277 u32 end_seq = start_seq + shifted; /* end of newly-SACKed */
1278
1279 BUG_ON(!pcount);
1280
1281 /* Adjust counters and hints for the newly sacked sequence
1282 * range but discard the return value since prev is already
1283 * marked. We must tag the range first because the seq
1284 * advancement below implicitly advances
1285 * tcp_highest_sack_seq() when skb is highest_sack.
1286 */
1287 tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
1288 start_seq, end_seq, dup_sack, pcount,
1289 &skb->skb_mstamp);
1290
1291 if (skb == tp->lost_skb_hint)
1292 tp->lost_cnt_hint += pcount;
1293
1294 TCP_SKB_CB(prev)->end_seq += shifted;
1295 TCP_SKB_CB(skb)->seq += shifted;
1296
1297 skb_shinfo(prev)->gso_segs += pcount;
1298 BUG_ON(skb_shinfo(skb)->gso_segs < pcount);
1299 skb_shinfo(skb)->gso_segs -= pcount;
1300
1301 /* When we're adding to gso_segs == 1, gso_size will be zero,
1302 * in theory this shouldn't be necessary but as long as DSACK
1303 * code can come after this skb later on it's better to keep
1304 * setting gso_size to something.
1305 */
1306 if (!skb_shinfo(prev)->gso_size) {
1307 skb_shinfo(prev)->gso_size = mss;
1308 skb_shinfo(prev)->gso_type = sk->sk_gso_type;
1309 }
1310
1311 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1312 if (skb_shinfo(skb)->gso_segs <= 1) {
1313 skb_shinfo(skb)->gso_size = 0;
1314 skb_shinfo(skb)->gso_type = 0;
1315 }
1316
1317 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1318 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
1319
1320 if (skb->len > 0) {
1321 BUG_ON(!tcp_skb_pcount(skb));
1322 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED);
1323 return false;
1324 }
1325
1326 /* Whole SKB was eaten :-) */
1327
1328 if (skb == tp->retransmit_skb_hint)
1329 tp->retransmit_skb_hint = prev;
1330 if (skb == tp->lost_skb_hint) {
1331 tp->lost_skb_hint = prev;
1332 tp->lost_cnt_hint -= tcp_skb_pcount(prev);
1333 }
1334
1335 TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1336 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1337 TCP_SKB_CB(prev)->end_seq++;
1338
1339 if (skb == tcp_highest_sack(sk))
1340 tcp_advance_highest_sack(sk, skb);
1341
1342 tcp_unlink_write_queue(skb, sk);
1343 sk_wmem_free_skb(sk, skb);
1344
1345 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED);
1346
1347 return true;
1348}
1349
1350/* I wish gso_size would have a bit more sane initialization than
1351 * something-or-zero which complicates things
1352 */
1353static int tcp_skb_seglen(const struct sk_buff *skb)
1354{
1355 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
1356}
1357
1358/* Shifting pages past head area doesn't work */
1359static int skb_can_shift(const struct sk_buff *skb)
1360{
1361 return !skb_headlen(skb) && skb_is_nonlinear(skb);
1362}
1363
1364/* Try collapsing SACK blocks spanning across multiple skbs to a single
1365 * skb.
1366 */
1367static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
1368 struct tcp_sacktag_state *state,
1369 u32 start_seq, u32 end_seq,
1370 bool dup_sack)
1371{
1372 struct tcp_sock *tp = tcp_sk(sk);
1373 struct sk_buff *prev;
1374 int mss;
1375 int pcount = 0;
1376 int len;
1377 int in_sack;
1378
1379 if (!sk_can_gso(sk))
1380 goto fallback;
1381
1382 /* Normally R but no L won't result in plain S */
1383 if (!dup_sack &&
1384 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
1385 goto fallback;
1386 if (!skb_can_shift(skb))
1387 goto fallback;
1388 /* This frame is about to be dropped (was ACKed). */
1389 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1390 goto fallback;
1391
1392 /* Can only happen with delayed DSACK + discard craziness */
1393 if (unlikely(skb == tcp_write_queue_head(sk)))
1394 goto fallback;
1395 prev = tcp_write_queue_prev(sk, skb);
1396
1397 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
1398 goto fallback;
1399
1400 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1401 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1402
1403 if (in_sack) {
1404 len = skb->len;
1405 pcount = tcp_skb_pcount(skb);
1406 mss = tcp_skb_seglen(skb);
1407
1408 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1409 * drop this restriction as unnecessary
1410 */
1411 if (mss != tcp_skb_seglen(prev))
1412 goto fallback;
1413 } else {
1414 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
1415 goto noop;
1416 /* CHECKME: This is non-MSS split case only?, this will
1417 * cause skipped skbs due to advancing loop btw, original
1418 * has that feature too
1419 */
1420 if (tcp_skb_pcount(skb) <= 1)
1421 goto noop;
1422
1423 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1424 if (!in_sack) {
1425 /* TODO: head merge to next could be attempted here
1426 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1427 * though it might not be worth of the additional hassle
1428 *
1429 * ...we can probably just fallback to what was done
1430 * previously. We could try merging non-SACKed ones
1431 * as well but it probably isn't going to buy off
1432 * because later SACKs might again split them, and
1433 * it would make skb timestamp tracking considerably
1434 * harder problem.
1435 */
1436 goto fallback;
1437 }
1438
1439 len = end_seq - TCP_SKB_CB(skb)->seq;
1440 BUG_ON(len < 0);
1441 BUG_ON(len > skb->len);
1442
1443 /* MSS boundaries should be honoured or else pcount will
1444 * severely break even though it makes things bit trickier.
1445 * Optimize common case to avoid most of the divides
1446 */
1447 mss = tcp_skb_mss(skb);
1448
1449 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1450 * drop this restriction as unnecessary
1451 */
1452 if (mss != tcp_skb_seglen(prev))
1453 goto fallback;
1454
1455 if (len == mss) {
1456 pcount = 1;
1457 } else if (len < mss) {
1458 goto noop;
1459 } else {
1460 pcount = len / mss;
1461 len = pcount * mss;
1462 }
1463 }
1464
1465 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1466 if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una))
1467 goto fallback;
1468
1469 if (!skb_shift(prev, skb, len))
1470 goto fallback;
1471 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
1472 goto out;
1473
1474 /* Hole filled allows collapsing with the next as well, this is very
1475 * useful when hole on every nth skb pattern happens
1476 */
1477 if (prev == tcp_write_queue_tail(sk))
1478 goto out;
1479 skb = tcp_write_queue_next(sk, prev);
1480
1481 if (!skb_can_shift(skb) ||
1482 (skb == tcp_send_head(sk)) ||
1483 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
1484 (mss != tcp_skb_seglen(skb)))
1485 goto out;
1486
1487 len = skb->len;
1488 if (skb_shift(prev, skb, len)) {
1489 pcount += tcp_skb_pcount(skb);
1490 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
1491 }
1492
1493out:
1494 state->fack_count += pcount;
1495 return prev;
1496
1497noop:
1498 return skb;
1499
1500fallback:
1501 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
1502 return NULL;
1503}
1504
1505static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
1506 struct tcp_sack_block *next_dup,
1507 struct tcp_sacktag_state *state,
1508 u32 start_seq, u32 end_seq,
1509 bool dup_sack_in)
1510{
1511 struct tcp_sock *tp = tcp_sk(sk);
1512 struct sk_buff *tmp;
1513
1514 tcp_for_write_queue_from(skb, sk) {
1515 int in_sack = 0;
1516 bool dup_sack = dup_sack_in;
1517
1518 if (skb == tcp_send_head(sk))
1519 break;
1520
1521 /* queue is in-order => we can short-circuit the walk early */
1522 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1523 break;
1524
1525 if ((next_dup != NULL) &&
1526 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
1527 in_sack = tcp_match_skb_to_sack(sk, skb,
1528 next_dup->start_seq,
1529 next_dup->end_seq);
1530 if (in_sack > 0)
1531 dup_sack = true;
1532 }
1533
1534 /* skb reference here is a bit tricky to get right, since
1535 * shifting can eat and free both this skb and the next,
1536 * so not even _safe variant of the loop is enough.
1537 */
1538 if (in_sack <= 0) {
1539 tmp = tcp_shift_skb_data(sk, skb, state,
1540 start_seq, end_seq, dup_sack);
1541 if (tmp != NULL) {
1542 if (tmp != skb) {
1543 skb = tmp;
1544 continue;
1545 }
1546
1547 in_sack = 0;
1548 } else {
1549 in_sack = tcp_match_skb_to_sack(sk, skb,
1550 start_seq,
1551 end_seq);
1552 }
1553 }
1554
1555 if (unlikely(in_sack < 0))
1556 break;
1557
1558 if (in_sack) {
1559 TCP_SKB_CB(skb)->sacked =
1560 tcp_sacktag_one(sk,
1561 state,
1562 TCP_SKB_CB(skb)->sacked,
1563 TCP_SKB_CB(skb)->seq,
1564 TCP_SKB_CB(skb)->end_seq,
1565 dup_sack,
1566 tcp_skb_pcount(skb),
1567 &skb->skb_mstamp);
1568
1569 if (!before(TCP_SKB_CB(skb)->seq,
1570 tcp_highest_sack_seq(tp)))
1571 tcp_advance_highest_sack(sk, skb);
1572 }
1573
1574 state->fack_count += tcp_skb_pcount(skb);
1575 }
1576 return skb;
1577}
1578
1579/* Avoid all extra work that is being done by sacktag while walking in
1580 * a normal way
1581 */
1582static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
1583 struct tcp_sacktag_state *state,
1584 u32 skip_to_seq)
1585{
1586 tcp_for_write_queue_from(skb, sk) {
1587 if (skb == tcp_send_head(sk))
1588 break;
1589
1590 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
1591 break;
1592
1593 state->fack_count += tcp_skb_pcount(skb);
1594 }
1595 return skb;
1596}
1597
1598static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
1599 struct sock *sk,
1600 struct tcp_sack_block *next_dup,
1601 struct tcp_sacktag_state *state,
1602 u32 skip_to_seq)
1603{
1604 if (next_dup == NULL)
1605 return skb;
1606
1607 if (before(next_dup->start_seq, skip_to_seq)) {
1608 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq);
1609 skb = tcp_sacktag_walk(skb, sk, NULL, state,
1610 next_dup->start_seq, next_dup->end_seq,
1611 1);
1612 }
1613
1614 return skb;
1615}
1616
1617static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache)
1618{
1619 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1620}
1621
1622static int
1623tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
1624 u32 prior_snd_una, long *sack_rtt_us)
1625{
1626 struct tcp_sock *tp = tcp_sk(sk);
1627 const unsigned char *ptr = (skb_transport_header(ack_skb) +
1628 TCP_SKB_CB(ack_skb)->sacked);
1629 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
1630 struct tcp_sack_block sp[TCP_NUM_SACKS];
1631 struct tcp_sack_block *cache;
1632 struct tcp_sacktag_state state;
1633 struct sk_buff *skb;
1634 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
1635 int used_sacks;
1636 bool found_dup_sack = false;
1637 int i, j;
1638 int first_sack_index;
1639
1640 state.flag = 0;
1641 state.reord = tp->packets_out;
1642 state.rtt_us = -1L;
1643
1644 if (!tp->sacked_out) {
1645 if (WARN_ON(tp->fackets_out))
1646 tp->fackets_out = 0;
1647 tcp_highest_sack_reset(sk);
1648 }
1649
1650 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
1651 num_sacks, prior_snd_una);
1652 if (found_dup_sack)
1653 state.flag |= FLAG_DSACKING_ACK;
1654
1655 /* Eliminate too old ACKs, but take into
1656 * account more or less fresh ones, they can
1657 * contain valid SACK info.
1658 */
1659 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
1660 return 0;
1661
1662 if (!tp->packets_out)
1663 goto out;
1664
1665 used_sacks = 0;
1666 first_sack_index = 0;
1667 for (i = 0; i < num_sacks; i++) {
1668 bool dup_sack = !i && found_dup_sack;
1669
1670 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
1671 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
1672
1673 if (!tcp_is_sackblock_valid(tp, dup_sack,
1674 sp[used_sacks].start_seq,
1675 sp[used_sacks].end_seq)) {
1676 int mib_idx;
1677
1678 if (dup_sack) {
1679 if (!tp->undo_marker)
1680 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO;
1681 else
1682 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD;
1683 } else {
1684 /* Don't count olds caused by ACK reordering */
1685 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
1686 !after(sp[used_sacks].end_seq, tp->snd_una))
1687 continue;
1688 mib_idx = LINUX_MIB_TCPSACKDISCARD;
1689 }
1690
1691 NET_INC_STATS_BH(sock_net(sk), mib_idx);
1692 if (i == 0)
1693 first_sack_index = -1;
1694 continue;
1695 }
1696
1697 /* Ignore very old stuff early */
1698 if (!after(sp[used_sacks].end_seq, prior_snd_una))
1699 continue;
1700
1701 used_sacks++;
1702 }
1703
1704 /* order SACK blocks to allow in order walk of the retrans queue */
1705 for (i = used_sacks - 1; i > 0; i--) {
1706 for (j = 0; j < i; j++) {
1707 if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
1708 swap(sp[j], sp[j + 1]);
1709
1710 /* Track where the first SACK block goes to */
1711 if (j == first_sack_index)
1712 first_sack_index = j + 1;
1713 }
1714 }
1715 }
1716
1717 skb = tcp_write_queue_head(sk);
1718 state.fack_count = 0;
1719 i = 0;
1720
1721 if (!tp->sacked_out) {
1722 /* It's already past, so skip checking against it */
1723 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1724 } else {
1725 cache = tp->recv_sack_cache;
1726 /* Skip empty blocks in at head of the cache */
1727 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
1728 !cache->end_seq)
1729 cache++;
1730 }
1731
1732 while (i < used_sacks) {
1733 u32 start_seq = sp[i].start_seq;
1734 u32 end_seq = sp[i].end_seq;
1735 bool dup_sack = (found_dup_sack && (i == first_sack_index));
1736 struct tcp_sack_block *next_dup = NULL;
1737
1738 if (found_dup_sack && ((i + 1) == first_sack_index))
1739 next_dup = &sp[i + 1];
1740
1741 /* Skip too early cached blocks */
1742 while (tcp_sack_cache_ok(tp, cache) &&
1743 !before(start_seq, cache->end_seq))
1744 cache++;
1745
1746 /* Can skip some work by looking recv_sack_cache? */
1747 if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
1748 after(end_seq, cache->start_seq)) {
1749
1750 /* Head todo? */
1751 if (before(start_seq, cache->start_seq)) {
1752 skb = tcp_sacktag_skip(skb, sk, &state,
1753 start_seq);
1754 skb = tcp_sacktag_walk(skb, sk, next_dup,
1755 &state,
1756 start_seq,
1757 cache->start_seq,
1758 dup_sack);
1759 }
1760
1761 /* Rest of the block already fully processed? */
1762 if (!after(end_seq, cache->end_seq))
1763 goto advance_sp;
1764
1765 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
1766 &state,
1767 cache->end_seq);
1768
1769 /* ...tail remains todo... */
1770 if (tcp_highest_sack_seq(tp) == cache->end_seq) {
1771 /* ...but better entrypoint exists! */
1772 skb = tcp_highest_sack(sk);
1773 if (skb == NULL)
1774 break;
1775 state.fack_count = tp->fackets_out;
1776 cache++;
1777 goto walk;
1778 }
1779
1780 skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq);
1781 /* Check overlap against next cached too (past this one already) */
1782 cache++;
1783 continue;
1784 }
1785
1786 if (!before(start_seq, tcp_highest_sack_seq(tp))) {
1787 skb = tcp_highest_sack(sk);
1788 if (skb == NULL)
1789 break;
1790 state.fack_count = tp->fackets_out;
1791 }
1792 skb = tcp_sacktag_skip(skb, sk, &state, start_seq);
1793
1794walk:
1795 skb = tcp_sacktag_walk(skb, sk, next_dup, &state,
1796 start_seq, end_seq, dup_sack);
1797
1798advance_sp:
1799 i++;
1800 }
1801
1802 /* Clear the head of the cache sack blocks so we can skip it next time */
1803 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
1804 tp->recv_sack_cache[i].start_seq = 0;
1805 tp->recv_sack_cache[i].end_seq = 0;
1806 }
1807 for (j = 0; j < used_sacks; j++)
1808 tp->recv_sack_cache[i++] = sp[j];
1809
1810 tcp_mark_lost_retrans(sk);
1811
1812 tcp_verify_left_out(tp);
1813
1814 if ((state.reord < tp->fackets_out) &&
1815 ((inet_csk(sk)->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker))
1816 tcp_update_reordering(sk, tp->fackets_out - state.reord, 0);
1817
1818out:
1819
1820#if FASTRETRANS_DEBUG > 0
1821 WARN_ON((int)tp->sacked_out < 0);
1822 WARN_ON((int)tp->lost_out < 0);
1823 WARN_ON((int)tp->retrans_out < 0);
1824 WARN_ON((int)tcp_packets_in_flight(tp) < 0);
1825#endif
1826 *sack_rtt_us = state.rtt_us;
1827 return state.flag;
1828}
1829
1830/* Limits sacked_out so that sum with lost_out isn't ever larger than
1831 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1832 */
1833static bool tcp_limit_reno_sacked(struct tcp_sock *tp)
1834{
1835 u32 holes;
1836
1837 holes = max(tp->lost_out, 1U);
1838 holes = min(holes, tp->packets_out);
1839
1840 if ((tp->sacked_out + holes) > tp->packets_out) {
1841 tp->sacked_out = tp->packets_out - holes;
1842 return true;
1843 }
1844 return false;
1845}
1846
1847/* If we receive more dupacks than we expected counting segments
1848 * in assumption of absent reordering, interpret this as reordering.
1849 * The only another reason could be bug in receiver TCP.
1850 */
1851static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1852{
1853 struct tcp_sock *tp = tcp_sk(sk);
1854 if (tcp_limit_reno_sacked(tp))
1855 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1856}
1857
1858/* Emulate SACKs for SACKless connection: account for a new dupack. */
1859
1860static void tcp_add_reno_sack(struct sock *sk)
1861{
1862 struct tcp_sock *tp = tcp_sk(sk);
1863 tp->sacked_out++;
1864 tcp_check_reno_reordering(sk, 0);
1865 tcp_verify_left_out(tp);
1866}
1867
1868/* Account for ACK, ACKing some data in Reno Recovery phase. */
1869
1870static void tcp_remove_reno_sacks(struct sock *sk, int acked)
1871{
1872 struct tcp_sock *tp = tcp_sk(sk);
1873
1874 if (acked > 0) {
1875 /* One ACK acked hole. The rest eat duplicate ACKs. */
1876 if (acked - 1 >= tp->sacked_out)
1877 tp->sacked_out = 0;
1878 else
1879 tp->sacked_out -= acked - 1;
1880 }
1881 tcp_check_reno_reordering(sk, acked);
1882 tcp_verify_left_out(tp);
1883}
1884
1885static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1886{
1887 tp->sacked_out = 0;
1888}
1889
1890static void tcp_clear_retrans_partial(struct tcp_sock *tp)
1891{
1892 tp->retrans_out = 0;
1893 tp->lost_out = 0;
1894
1895 tp->undo_marker = 0;
1896 tp->undo_retrans = 0;
1897}
1898
1899void tcp_clear_retrans(struct tcp_sock *tp)
1900{
1901 tcp_clear_retrans_partial(tp);
1902
1903 tp->fackets_out = 0;
1904 tp->sacked_out = 0;
1905}
1906
1907/* Enter Loss state. If "how" is not zero, forget all SACK information
1908 * and reset tags completely, otherwise preserve SACKs. If receiver
1909 * dropped its ofo queue, we will know this due to reneging detection.
1910 */
1911void tcp_enter_loss(struct sock *sk, int how)
1912{
1913 const struct inet_connection_sock *icsk = inet_csk(sk);
1914 struct tcp_sock *tp = tcp_sk(sk);
1915 struct sk_buff *skb;
1916 bool new_recovery = false;
1917
1918 /* Reduce ssthresh if it has not yet been made inside this window. */
1919 if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
1920 !after(tp->high_seq, tp->snd_una) ||
1921 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1922 new_recovery = true;
1923 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1924 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1925 tcp_ca_event(sk, CA_EVENT_LOSS);
1926 }
1927 tp->snd_cwnd = 1;
1928 tp->snd_cwnd_cnt = 0;
1929 tp->snd_cwnd_stamp = tcp_time_stamp;
1930
1931 tcp_clear_retrans_partial(tp);
1932
1933 if (tcp_is_reno(tp))
1934 tcp_reset_reno_sack(tp);
1935
1936 tp->undo_marker = tp->snd_una;
1937 if (how) {
1938 tp->sacked_out = 0;
1939 tp->fackets_out = 0;
1940 }
1941 tcp_clear_all_retrans_hints(tp);
1942
1943 tcp_for_write_queue(skb, sk) {
1944 if (skb == tcp_send_head(sk))
1945 break;
1946
1947 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1948 tp->undo_marker = 0;
1949
1950 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1951 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1952 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1953 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1954 tp->lost_out += tcp_skb_pcount(skb);
1955 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
1956 }
1957 }
1958 tcp_verify_left_out(tp);
1959
1960 /* Timeout in disordered state after receiving substantial DUPACKs
1961 * suggests that the degree of reordering is over-estimated.
1962 */
1963 if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
1964 tp->sacked_out >= sysctl_tcp_reordering)
1965 tp->reordering = min_t(unsigned int, tp->reordering,
1966 sysctl_tcp_reordering);
1967 tcp_set_ca_state(sk, TCP_CA_Loss);
1968 tp->high_seq = tp->snd_nxt;
1969 TCP_ECN_queue_cwr(tp);
1970
1971 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1972 * loss recovery is underway except recurring timeout(s) on
1973 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1974 */
1975 tp->frto = sysctl_tcp_frto &&
1976 (new_recovery || icsk->icsk_retransmits) &&
1977 !inet_csk(sk)->icsk_mtup.probe_size;
1978}
1979
1980/* If ACK arrived pointing to a remembered SACK, it means that our
1981 * remembered SACKs do not reflect real state of receiver i.e.
1982 * receiver _host_ is heavily congested (or buggy).
1983 *
1984 * Do processing similar to RTO timeout.
1985 */
1986static bool tcp_check_sack_reneging(struct sock *sk, int flag)
1987{
1988 if (flag & FLAG_SACK_RENEGING) {
1989 struct inet_connection_sock *icsk = inet_csk(sk);
1990 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
1991
1992 tcp_enter_loss(sk, 1);
1993 icsk->icsk_retransmits++;
1994 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
1995 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
1996 icsk->icsk_rto, TCP_RTO_MAX);
1997 return true;
1998 }
1999 return false;
2000}
2001
2002static inline int tcp_fackets_out(const struct tcp_sock *tp)
2003{
2004 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out;
2005}
2006
2007/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2008 * counter when SACK is enabled (without SACK, sacked_out is used for
2009 * that purpose).
2010 *
2011 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2012 * segments up to the highest received SACK block so far and holes in
2013 * between them.
2014 *
2015 * With reordering, holes may still be in flight, so RFC3517 recovery
2016 * uses pure sacked_out (total number of SACKed segments) even though
2017 * it violates the RFC that uses duplicate ACKs, often these are equal
2018 * but when e.g. out-of-window ACKs or packet duplication occurs,
2019 * they differ. Since neither occurs due to loss, TCP should really
2020 * ignore them.
2021 */
2022static inline int tcp_dupack_heuristics(const struct tcp_sock *tp)
2023{
2024 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
2025}
2026
2027static bool tcp_pause_early_retransmit(struct sock *sk, int flag)
2028{
2029 struct tcp_sock *tp = tcp_sk(sk);
2030 unsigned long delay;
2031
2032 /* Delay early retransmit and entering fast recovery for
2033 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2034 * available, or RTO is scheduled to fire first.
2035 */
2036 if (sysctl_tcp_early_retrans < 2 || sysctl_tcp_early_retrans > 3 ||
2037 (flag & FLAG_ECE) || !tp->srtt_us)
2038 return false;
2039
2040 delay = max(usecs_to_jiffies(tp->srtt_us >> 5),
2041 msecs_to_jiffies(2));
2042
2043 if (!time_after(inet_csk(sk)->icsk_timeout, (jiffies + delay)))
2044 return false;
2045
2046 inet_csk_reset_xmit_timer(sk, ICSK_TIME_EARLY_RETRANS, delay,
2047 TCP_RTO_MAX);
2048 return true;
2049}
2050
2051/* Linux NewReno/SACK/FACK/ECN state machine.
2052 * --------------------------------------
2053 *
2054 * "Open" Normal state, no dubious events, fast path.
2055 * "Disorder" In all the respects it is "Open",
2056 * but requires a bit more attention. It is entered when
2057 * we see some SACKs or dupacks. It is split of "Open"
2058 * mainly to move some processing from fast path to slow one.
2059 * "CWR" CWND was reduced due to some Congestion Notification event.
2060 * It can be ECN, ICMP source quench, local device congestion.
2061 * "Recovery" CWND was reduced, we are fast-retransmitting.
2062 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2063 *
2064 * tcp_fastretrans_alert() is entered:
2065 * - each incoming ACK, if state is not "Open"
2066 * - when arrived ACK is unusual, namely:
2067 * * SACK
2068 * * Duplicate ACK.
2069 * * ECN ECE.
2070 *
2071 * Counting packets in flight is pretty simple.
2072 *
2073 * in_flight = packets_out - left_out + retrans_out
2074 *
2075 * packets_out is SND.NXT-SND.UNA counted in packets.
2076 *
2077 * retrans_out is number of retransmitted segments.
2078 *
2079 * left_out is number of segments left network, but not ACKed yet.
2080 *
2081 * left_out = sacked_out + lost_out
2082 *
2083 * sacked_out: Packets, which arrived to receiver out of order
2084 * and hence not ACKed. With SACKs this number is simply
2085 * amount of SACKed data. Even without SACKs
2086 * it is easy to give pretty reliable estimate of this number,
2087 * counting duplicate ACKs.
2088 *
2089 * lost_out: Packets lost by network. TCP has no explicit
2090 * "loss notification" feedback from network (for now).
2091 * It means that this number can be only _guessed_.
2092 * Actually, it is the heuristics to predict lossage that
2093 * distinguishes different algorithms.
2094 *
2095 * F.e. after RTO, when all the queue is considered as lost,
2096 * lost_out = packets_out and in_flight = retrans_out.
2097 *
2098 * Essentially, we have now two algorithms counting
2099 * lost packets.
2100 *
2101 * FACK: It is the simplest heuristics. As soon as we decided
2102 * that something is lost, we decide that _all_ not SACKed
2103 * packets until the most forward SACK are lost. I.e.
2104 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2105 * It is absolutely correct estimate, if network does not reorder
2106 * packets. And it loses any connection to reality when reordering
2107 * takes place. We use FACK by default until reordering
2108 * is suspected on the path to this destination.
2109 *
2110 * NewReno: when Recovery is entered, we assume that one segment
2111 * is lost (classic Reno). While we are in Recovery and
2112 * a partial ACK arrives, we assume that one more packet
2113 * is lost (NewReno). This heuristics are the same in NewReno
2114 * and SACK.
2115 *
2116 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2117 * deflation etc. CWND is real congestion window, never inflated, changes
2118 * only according to classic VJ rules.
2119 *
2120 * Really tricky (and requiring careful tuning) part of algorithm
2121 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2122 * The first determines the moment _when_ we should reduce CWND and,
2123 * hence, slow down forward transmission. In fact, it determines the moment
2124 * when we decide that hole is caused by loss, rather than by a reorder.
2125 *
2126 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2127 * holes, caused by lost packets.
2128 *
2129 * And the most logically complicated part of algorithm is undo
2130 * heuristics. We detect false retransmits due to both too early
2131 * fast retransmit (reordering) and underestimated RTO, analyzing
2132 * timestamps and D-SACKs. When we detect that some segments were
2133 * retransmitted by mistake and CWND reduction was wrong, we undo
2134 * window reduction and abort recovery phase. This logic is hidden
2135 * inside several functions named tcp_try_undo_<something>.
2136 */
2137
2138/* This function decides, when we should leave Disordered state
2139 * and enter Recovery phase, reducing congestion window.
2140 *
2141 * Main question: may we further continue forward transmission
2142 * with the same cwnd?
2143 */
2144static bool tcp_time_to_recover(struct sock *sk, int flag)
2145{
2146 struct tcp_sock *tp = tcp_sk(sk);
2147 __u32 packets_out;
2148
2149 /* Trick#1: The loss is proven. */
2150 if (tp->lost_out)
2151 return true;
2152
2153 /* Not-A-Trick#2 : Classic rule... */
2154 if (tcp_dupack_heuristics(tp) > tp->reordering)
2155 return true;
2156
2157 /* Trick#4: It is still not OK... But will it be useful to delay
2158 * recovery more?
2159 */
2160 packets_out = tp->packets_out;
2161 if (packets_out <= tp->reordering &&
2162 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
2163 !tcp_may_send_now(sk)) {
2164 /* We have nothing to send. This connection is limited
2165 * either by receiver window or by application.
2166 */
2167 return true;
2168 }
2169
2170 /* If a thin stream is detected, retransmit after first
2171 * received dupack. Employ only if SACK is supported in order
2172 * to avoid possible corner-case series of spurious retransmissions
2173 * Use only if there are no unsent data.
2174 */
2175 if ((tp->thin_dupack || sysctl_tcp_thin_dupack) &&
2176 tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 &&
2177 tcp_is_sack(tp) && !tcp_send_head(sk))
2178 return true;
2179
2180 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2181 * retransmissions due to small network reorderings, we implement
2182 * Mitigation A.3 in the RFC and delay the retransmission for a short
2183 * interval if appropriate.
2184 */
2185 if (tp->do_early_retrans && !tp->retrans_out && tp->sacked_out &&
2186 (tp->packets_out >= (tp->sacked_out + 1) && tp->packets_out < 4) &&
2187 !tcp_may_send_now(sk))
2188 return !tcp_pause_early_retransmit(sk, flag);
2189
2190 return false;
2191}
2192
2193/* Detect loss in event "A" above by marking head of queue up as lost.
2194 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2195 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2196 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2197 * the maximum SACKed segments to pass before reaching this limit.
2198 */
2199static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
2200{
2201 struct tcp_sock *tp = tcp_sk(sk);
2202 struct sk_buff *skb;
2203 int cnt, oldcnt;
2204 int err;
2205 unsigned int mss;
2206 /* Use SACK to deduce losses of new sequences sent during recovery */
2207 const u32 loss_high = tcp_is_sack(tp) ? tp->snd_nxt : tp->high_seq;
2208
2209 WARN_ON(packets > tp->packets_out);
2210 if (tp->lost_skb_hint) {
2211 skb = tp->lost_skb_hint;
2212 cnt = tp->lost_cnt_hint;
2213 /* Head already handled? */
2214 if (mark_head && skb != tcp_write_queue_head(sk))
2215 return;
2216 } else {
2217 skb = tcp_write_queue_head(sk);
2218 cnt = 0;
2219 }
2220
2221 tcp_for_write_queue_from(skb, sk) {
2222 if (skb == tcp_send_head(sk))
2223 break;
2224 /* TODO: do this better */
2225 /* this is not the most efficient way to do this... */
2226 tp->lost_skb_hint = skb;
2227 tp->lost_cnt_hint = cnt;
2228
2229 if (after(TCP_SKB_CB(skb)->end_seq, loss_high))
2230 break;
2231
2232 oldcnt = cnt;
2233 if (tcp_is_fack(tp) || tcp_is_reno(tp) ||
2234 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
2235 cnt += tcp_skb_pcount(skb);
2236
2237 if (cnt > packets) {
2238 if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) ||
2239 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) ||
2240 (oldcnt >= packets))
2241 break;
2242
2243 mss = skb_shinfo(skb)->gso_size;
2244 err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss);
2245 if (err < 0)
2246 break;
2247 cnt = packets;
2248 }
2249
2250 tcp_skb_mark_lost(tp, skb);
2251
2252 if (mark_head)
2253 break;
2254 }
2255 tcp_verify_left_out(tp);
2256}
2257
2258/* Account newly detected lost packet(s) */
2259
2260static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
2261{
2262 struct tcp_sock *tp = tcp_sk(sk);
2263
2264 if (tcp_is_reno(tp)) {
2265 tcp_mark_head_lost(sk, 1, 1);
2266 } else if (tcp_is_fack(tp)) {
2267 int lost = tp->fackets_out - tp->reordering;
2268 if (lost <= 0)
2269 lost = 1;
2270 tcp_mark_head_lost(sk, lost, 0);
2271 } else {
2272 int sacked_upto = tp->sacked_out - tp->reordering;
2273 if (sacked_upto >= 0)
2274 tcp_mark_head_lost(sk, sacked_upto, 0);
2275 else if (fast_rexmit)
2276 tcp_mark_head_lost(sk, 1, 1);
2277 }
2278}
2279
2280/* CWND moderation, preventing bursts due to too big ACKs
2281 * in dubious situations.
2282 */
2283static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
2284{
2285 tp->snd_cwnd = min(tp->snd_cwnd,
2286 tcp_packets_in_flight(tp) + tcp_max_burst(tp));
2287 tp->snd_cwnd_stamp = tcp_time_stamp;
2288}
2289
2290/* Nothing was retransmitted or returned timestamp is less
2291 * than timestamp of the first retransmission.
2292 */
2293static inline bool tcp_packet_delayed(const struct tcp_sock *tp)
2294{
2295 return !tp->retrans_stamp ||
2296 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2297 before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp));
2298}
2299
2300/* Undo procedures. */
2301
2302#if FASTRETRANS_DEBUG > 1
2303static void DBGUNDO(struct sock *sk, const char *msg)
2304{
2305 struct tcp_sock *tp = tcp_sk(sk);
2306 struct inet_sock *inet = inet_sk(sk);
2307
2308 if (sk->sk_family == AF_INET) {
2309 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2310 msg,
2311 &inet->inet_daddr, ntohs(inet->inet_dport),
2312 tp->snd_cwnd, tcp_left_out(tp),
2313 tp->snd_ssthresh, tp->prior_ssthresh,
2314 tp->packets_out);
2315 }
2316#if IS_ENABLED(CONFIG_IPV6)
2317 else if (sk->sk_family == AF_INET6) {
2318 struct ipv6_pinfo *np = inet6_sk(sk);
2319 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2320 msg,
2321 &np->daddr, ntohs(inet->inet_dport),
2322 tp->snd_cwnd, tcp_left_out(tp),
2323 tp->snd_ssthresh, tp->prior_ssthresh,
2324 tp->packets_out);
2325 }
2326#endif
2327}
2328#else
2329#define DBGUNDO(x...) do { } while (0)
2330#endif
2331
2332static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss)
2333{
2334 struct tcp_sock *tp = tcp_sk(sk);
2335
2336 if (unmark_loss) {
2337 struct sk_buff *skb;
2338
2339 tcp_for_write_queue(skb, sk) {
2340 if (skb == tcp_send_head(sk))
2341 break;
2342 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2343 }
2344 tp->lost_out = 0;
2345 tcp_clear_all_retrans_hints(tp);
2346 }
2347
2348 if (tp->prior_ssthresh) {
2349 const struct inet_connection_sock *icsk = inet_csk(sk);
2350
2351 if (icsk->icsk_ca_ops->undo_cwnd)
2352 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
2353 else
2354 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
2355
2356 if (tp->prior_ssthresh > tp->snd_ssthresh) {
2357 tp->snd_ssthresh = tp->prior_ssthresh;
2358 TCP_ECN_withdraw_cwr(tp);
2359 }
2360 } else {
2361 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
2362 }
2363 tp->snd_cwnd_stamp = tcp_time_stamp;
2364 tp->undo_marker = 0;
2365}
2366
2367static inline bool tcp_may_undo(const struct tcp_sock *tp)
2368{
2369 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
2370}
2371
2372/* People celebrate: "We love our President!" */
2373static bool tcp_try_undo_recovery(struct sock *sk)
2374{
2375 struct tcp_sock *tp = tcp_sk(sk);
2376
2377 if (tcp_may_undo(tp)) {
2378 int mib_idx;
2379
2380 /* Happy end! We did not retransmit anything
2381 * or our original transmission succeeded.
2382 */
2383 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
2384 tcp_undo_cwnd_reduction(sk, false);
2385 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
2386 mib_idx = LINUX_MIB_TCPLOSSUNDO;
2387 else
2388 mib_idx = LINUX_MIB_TCPFULLUNDO;
2389
2390 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2391 }
2392 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
2393 /* Hold old state until something *above* high_seq
2394 * is ACKed. For Reno it is MUST to prevent false
2395 * fast retransmits (RFC2582). SACK TCP is safe. */
2396 tcp_moderate_cwnd(tp);
2397 return true;
2398 }
2399 tcp_set_ca_state(sk, TCP_CA_Open);
2400 return false;
2401}
2402
2403/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2404static bool tcp_try_undo_dsack(struct sock *sk)
2405{
2406 struct tcp_sock *tp = tcp_sk(sk);
2407
2408 if (tp->undo_marker && !tp->undo_retrans) {
2409 DBGUNDO(sk, "D-SACK");
2410 tcp_undo_cwnd_reduction(sk, false);
2411 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
2412 return true;
2413 }
2414 return false;
2415}
2416
2417/* We can clear retrans_stamp when there are no retransmissions in the
2418 * window. It would seem that it is trivially available for us in
2419 * tp->retrans_out, however, that kind of assumptions doesn't consider
2420 * what will happen if errors occur when sending retransmission for the
2421 * second time. ...It could the that such segment has only
2422 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2423 * the head skb is enough except for some reneging corner cases that
2424 * are not worth the effort.
2425 *
2426 * Main reason for all this complexity is the fact that connection dying
2427 * time now depends on the validity of the retrans_stamp, in particular,
2428 * that successive retransmissions of a segment must not advance
2429 * retrans_stamp under any conditions.
2430 */
2431static bool tcp_any_retrans_done(const struct sock *sk)
2432{
2433 const struct tcp_sock *tp = tcp_sk(sk);
2434 struct sk_buff *skb;
2435
2436 if (tp->retrans_out)
2437 return true;
2438
2439 skb = tcp_write_queue_head(sk);
2440 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
2441 return true;
2442
2443 return false;
2444}
2445
2446/* Undo during loss recovery after partial ACK or using F-RTO. */
2447static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo)
2448{
2449 struct tcp_sock *tp = tcp_sk(sk);
2450
2451 if (frto_undo || tcp_may_undo(tp)) {
2452 tcp_undo_cwnd_reduction(sk, true);
2453
2454 DBGUNDO(sk, "partial loss");
2455 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
2456 if (frto_undo)
2457 NET_INC_STATS_BH(sock_net(sk),
2458 LINUX_MIB_TCPSPURIOUSRTOS);
2459 inet_csk(sk)->icsk_retransmits = 0;
2460 if (frto_undo || tcp_is_sack(tp))
2461 tcp_set_ca_state(sk, TCP_CA_Open);
2462 return true;
2463 }
2464 return false;
2465}
2466
2467/* The cwnd reduction in CWR and Recovery use the PRR algorithm
2468 * https://datatracker.ietf.org/doc/draft-ietf-tcpm-proportional-rate-reduction/
2469 * It computes the number of packets to send (sndcnt) based on packets newly
2470 * delivered:
2471 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2472 * cwnd reductions across a full RTT.
2473 * 2) If packets in flight is lower than ssthresh (such as due to excess
2474 * losses and/or application stalls), do not perform any further cwnd
2475 * reductions, but instead slow start up to ssthresh.
2476 */
2477static void tcp_init_cwnd_reduction(struct sock *sk, const bool set_ssthresh)
2478{
2479 struct tcp_sock *tp = tcp_sk(sk);
2480
2481 tp->high_seq = tp->snd_nxt;
2482 tp->tlp_high_seq = 0;
2483 tp->snd_cwnd_cnt = 0;
2484 tp->prior_cwnd = tp->snd_cwnd;
2485 tp->prr_delivered = 0;
2486 tp->prr_out = 0;
2487 if (set_ssthresh)
2488 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
2489 TCP_ECN_queue_cwr(tp);
2490}
2491
2492static void tcp_cwnd_reduction(struct sock *sk, const int prior_unsacked,
2493 int fast_rexmit)
2494{
2495 struct tcp_sock *tp = tcp_sk(sk);
2496 int sndcnt = 0;
2497 int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp);
2498 int newly_acked_sacked = prior_unsacked -
2499 (tp->packets_out - tp->sacked_out);
2500
2501 tp->prr_delivered += newly_acked_sacked;
2502 if (tcp_packets_in_flight(tp) > tp->snd_ssthresh) {
2503 u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +
2504 tp->prior_cwnd - 1;
2505 sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out;
2506 } else {
2507 sndcnt = min_t(int, delta,
2508 max_t(int, tp->prr_delivered - tp->prr_out,
2509 newly_acked_sacked) + 1);
2510 }
2511
2512 sndcnt = max(sndcnt, (fast_rexmit ? 1 : 0));
2513 tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
2514}
2515
2516static inline void tcp_end_cwnd_reduction(struct sock *sk)
2517{
2518 struct tcp_sock *tp = tcp_sk(sk);
2519
2520 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2521 if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR ||
2522 (tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) {
2523 tp->snd_cwnd = tp->snd_ssthresh;
2524 tp->snd_cwnd_stamp = tcp_time_stamp;
2525 }
2526 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
2527}
2528
2529/* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2530void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
2531{
2532 struct tcp_sock *tp = tcp_sk(sk);
2533
2534 tp->prior_ssthresh = 0;
2535 if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
2536 tp->undo_marker = 0;
2537 tcp_init_cwnd_reduction(sk, set_ssthresh);
2538 tcp_set_ca_state(sk, TCP_CA_CWR);
2539 }
2540}
2541
2542static void tcp_try_keep_open(struct sock *sk)
2543{
2544 struct tcp_sock *tp = tcp_sk(sk);
2545 int state = TCP_CA_Open;
2546
2547 if (tcp_left_out(tp) || tcp_any_retrans_done(sk))
2548 state = TCP_CA_Disorder;
2549
2550 if (inet_csk(sk)->icsk_ca_state != state) {
2551 tcp_set_ca_state(sk, state);
2552 tp->high_seq = tp->snd_nxt;
2553 }
2554}
2555
2556static void tcp_try_to_open(struct sock *sk, int flag, const int prior_unsacked)
2557{
2558 struct tcp_sock *tp = tcp_sk(sk);
2559
2560 tcp_verify_left_out(tp);
2561
2562 if (!tcp_any_retrans_done(sk))
2563 tp->retrans_stamp = 0;
2564
2565 if (flag & FLAG_ECE)
2566 tcp_enter_cwr(sk, 1);
2567
2568 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
2569 tcp_try_keep_open(sk);
2570 } else {
2571 tcp_cwnd_reduction(sk, prior_unsacked, 0);
2572 }
2573}
2574
2575static void tcp_mtup_probe_failed(struct sock *sk)
2576{
2577 struct inet_connection_sock *icsk = inet_csk(sk);
2578
2579 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
2580 icsk->icsk_mtup.probe_size = 0;
2581}
2582
2583static void tcp_mtup_probe_success(struct sock *sk)
2584{
2585 struct tcp_sock *tp = tcp_sk(sk);
2586 struct inet_connection_sock *icsk = inet_csk(sk);
2587
2588 /* FIXME: breaks with very large cwnd */
2589 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2590 tp->snd_cwnd = tp->snd_cwnd *
2591 tcp_mss_to_mtu(sk, tp->mss_cache) /
2592 icsk->icsk_mtup.probe_size;
2593 tp->snd_cwnd_cnt = 0;
2594 tp->snd_cwnd_stamp = tcp_time_stamp;
2595 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2596
2597 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
2598 icsk->icsk_mtup.probe_size = 0;
2599 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
2600}
2601
2602/* Do a simple retransmit without using the backoff mechanisms in
2603 * tcp_timer. This is used for path mtu discovery.
2604 * The socket is already locked here.
2605 */
2606void tcp_simple_retransmit(struct sock *sk)
2607{
2608 const struct inet_connection_sock *icsk = inet_csk(sk);
2609 struct tcp_sock *tp = tcp_sk(sk);
2610 struct sk_buff *skb;
2611 unsigned int mss = tcp_current_mss(sk);
2612 u32 prior_lost = tp->lost_out;
2613
2614 tcp_for_write_queue(skb, sk) {
2615 if (skb == tcp_send_head(sk))
2616 break;
2617 if (tcp_skb_seglen(skb) > mss &&
2618 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
2619 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2620 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2621 tp->retrans_out -= tcp_skb_pcount(skb);
2622 }
2623 tcp_skb_mark_lost_uncond_verify(tp, skb);
2624 }
2625 }
2626
2627 tcp_clear_retrans_hints_partial(tp);
2628
2629 if (prior_lost == tp->lost_out)
2630 return;
2631
2632 if (tcp_is_reno(tp))
2633 tcp_limit_reno_sacked(tp);
2634
2635 tcp_verify_left_out(tp);
2636
2637 /* Don't muck with the congestion window here.
2638 * Reason is that we do not increase amount of _data_
2639 * in network, but units changed and effective
2640 * cwnd/ssthresh really reduced now.
2641 */
2642 if (icsk->icsk_ca_state != TCP_CA_Loss) {
2643 tp->high_seq = tp->snd_nxt;
2644 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2645 tp->prior_ssthresh = 0;
2646 tp->undo_marker = 0;
2647 tcp_set_ca_state(sk, TCP_CA_Loss);
2648 }
2649 tcp_xmit_retransmit_queue(sk);
2650}
2651EXPORT_SYMBOL(tcp_simple_retransmit);
2652
2653static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
2654{
2655 struct tcp_sock *tp = tcp_sk(sk);
2656 int mib_idx;
2657
2658 if (tcp_is_reno(tp))
2659 mib_idx = LINUX_MIB_TCPRENORECOVERY;
2660 else
2661 mib_idx = LINUX_MIB_TCPSACKRECOVERY;
2662
2663 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2664
2665 tp->prior_ssthresh = 0;
2666 tp->undo_marker = tp->snd_una;
2667 tp->undo_retrans = tp->retrans_out;
2668
2669 if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
2670 if (!ece_ack)
2671 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2672 tcp_init_cwnd_reduction(sk, true);
2673 }
2674 tcp_set_ca_state(sk, TCP_CA_Recovery);
2675}
2676
2677/* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2678 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2679 */
2680static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
2681{
2682 struct inet_connection_sock *icsk = inet_csk(sk);
2683 struct tcp_sock *tp = tcp_sk(sk);
2684 bool recovered = !before(tp->snd_una, tp->high_seq);
2685
2686 if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2687 /* Step 3.b. A timeout is spurious if not all data are
2688 * lost, i.e., never-retransmitted data are (s)acked.
2689 */
2690 if (tcp_try_undo_loss(sk, flag & FLAG_ORIG_SACK_ACKED))
2691 return;
2692
2693 if (after(tp->snd_nxt, tp->high_seq) &&
2694 (flag & FLAG_DATA_SACKED || is_dupack)) {
2695 tp->frto = 0; /* Loss was real: 2nd part of step 3.a */
2696 } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
2697 tp->high_seq = tp->snd_nxt;
2698 __tcp_push_pending_frames(sk, tcp_current_mss(sk),
2699 TCP_NAGLE_OFF);
2700 if (after(tp->snd_nxt, tp->high_seq))
2701 return; /* Step 2.b */
2702 tp->frto = 0;
2703 }
2704 }
2705
2706 if (recovered) {
2707 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2708 icsk->icsk_retransmits = 0;
2709 tcp_try_undo_recovery(sk);
2710 return;
2711 }
2712 if (flag & FLAG_DATA_ACKED)
2713 icsk->icsk_retransmits = 0;
2714 if (tcp_is_reno(tp)) {
2715 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2716 * delivered. Lower inflight to clock out (re)tranmissions.
2717 */
2718 if (after(tp->snd_nxt, tp->high_seq) && is_dupack)
2719 tcp_add_reno_sack(sk);
2720 else if (flag & FLAG_SND_UNA_ADVANCED)
2721 tcp_reset_reno_sack(tp);
2722 }
2723 if (tcp_try_undo_loss(sk, false))
2724 return;
2725 tcp_xmit_retransmit_queue(sk);
2726}
2727
2728/* Undo during fast recovery after partial ACK. */
2729static bool tcp_try_undo_partial(struct sock *sk, const int acked,
2730 const int prior_unsacked)
2731{
2732 struct tcp_sock *tp = tcp_sk(sk);
2733
2734 if (tp->undo_marker && tcp_packet_delayed(tp)) {
2735 /* Plain luck! Hole if filled with delayed
2736 * packet, rather than with a retransmit.
2737 */
2738 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
2739
2740 /* We are getting evidence that the reordering degree is higher
2741 * than we realized. If there are no retransmits out then we
2742 * can undo. Otherwise we clock out new packets but do not
2743 * mark more packets lost or retransmit more.
2744 */
2745 if (tp->retrans_out) {
2746 tcp_cwnd_reduction(sk, prior_unsacked, 0);
2747 return true;
2748 }
2749
2750 if (!tcp_any_retrans_done(sk))
2751 tp->retrans_stamp = 0;
2752
2753 DBGUNDO(sk, "partial recovery");
2754 tcp_undo_cwnd_reduction(sk, true);
2755 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
2756 tcp_try_keep_open(sk);
2757 return true;
2758 }
2759 return false;
2760}
2761
2762/* Process an event, which can update packets-in-flight not trivially.
2763 * Main goal of this function is to calculate new estimate for left_out,
2764 * taking into account both packets sitting in receiver's buffer and
2765 * packets lost by network.
2766 *
2767 * Besides that it does CWND reduction, when packet loss is detected
2768 * and changes state of machine.
2769 *
2770 * It does _not_ decide what to send, it is made in function
2771 * tcp_xmit_retransmit_queue().
2772 */
2773static void tcp_fastretrans_alert(struct sock *sk, const int acked,
2774 const int prior_unsacked,
2775 bool is_dupack, int flag)
2776{
2777 struct inet_connection_sock *icsk = inet_csk(sk);
2778 struct tcp_sock *tp = tcp_sk(sk);
2779 bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
2780 (tcp_fackets_out(tp) > tp->reordering));
2781 int fast_rexmit = 0;
2782
2783 if (WARN_ON(!tp->packets_out && tp->sacked_out))
2784 tp->sacked_out = 0;
2785 if (WARN_ON(!tp->sacked_out && tp->fackets_out))
2786 tp->fackets_out = 0;
2787
2788 /* Now state machine starts.
2789 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2790 if (flag & FLAG_ECE)
2791 tp->prior_ssthresh = 0;
2792
2793 /* B. In all the states check for reneging SACKs. */
2794 if (tcp_check_sack_reneging(sk, flag))
2795 return;
2796
2797 /* C. Check consistency of the current state. */
2798 tcp_verify_left_out(tp);
2799
2800 /* D. Check state exit conditions. State can be terminated
2801 * when high_seq is ACKed. */
2802 if (icsk->icsk_ca_state == TCP_CA_Open) {
2803 WARN_ON(tp->retrans_out != 0);
2804 tp->retrans_stamp = 0;
2805 } else if (!before(tp->snd_una, tp->high_seq)) {
2806 switch (icsk->icsk_ca_state) {
2807 case TCP_CA_CWR:
2808 /* CWR is to be held something *above* high_seq
2809 * is ACKed for CWR bit to reach receiver. */
2810 if (tp->snd_una != tp->high_seq) {
2811 tcp_end_cwnd_reduction(sk);
2812 tcp_set_ca_state(sk, TCP_CA_Open);
2813 }
2814 break;
2815
2816 case TCP_CA_Recovery:
2817 if (tcp_is_reno(tp))
2818 tcp_reset_reno_sack(tp);
2819 if (tcp_try_undo_recovery(sk))
2820 return;
2821 tcp_end_cwnd_reduction(sk);
2822 break;
2823 }
2824 }
2825
2826 /* E. Process state. */
2827 switch (icsk->icsk_ca_state) {
2828 case TCP_CA_Recovery:
2829 if (!(flag & FLAG_SND_UNA_ADVANCED)) {
2830 if (tcp_is_reno(tp) && is_dupack)
2831 tcp_add_reno_sack(sk);
2832 } else {
2833 if (tcp_try_undo_partial(sk, acked, prior_unsacked))
2834 return;
2835 /* Partial ACK arrived. Force fast retransmit. */
2836 do_lost = tcp_is_reno(tp) ||
2837 tcp_fackets_out(tp) > tp->reordering;
2838 }
2839 if (tcp_try_undo_dsack(sk)) {
2840 tcp_try_keep_open(sk);
2841 return;
2842 }
2843 break;
2844 case TCP_CA_Loss:
2845 tcp_process_loss(sk, flag, is_dupack);
2846 if (icsk->icsk_ca_state != TCP_CA_Open)
2847 return;
2848 /* Fall through to processing in Open state. */
2849 default:
2850 if (tcp_is_reno(tp)) {
2851 if (flag & FLAG_SND_UNA_ADVANCED)
2852 tcp_reset_reno_sack(tp);
2853 if (is_dupack)
2854 tcp_add_reno_sack(sk);
2855 }
2856
2857 if (icsk->icsk_ca_state <= TCP_CA_Disorder)
2858 tcp_try_undo_dsack(sk);
2859
2860 if (!tcp_time_to_recover(sk, flag)) {
2861 tcp_try_to_open(sk, flag, prior_unsacked);
2862 return;
2863 }
2864
2865 /* MTU probe failure: don't reduce cwnd */
2866 if (icsk->icsk_ca_state < TCP_CA_CWR &&
2867 icsk->icsk_mtup.probe_size &&
2868 tp->snd_una == tp->mtu_probe.probe_seq_start) {
2869 tcp_mtup_probe_failed(sk);
2870 /* Restores the reduction we did in tcp_mtup_probe() */
2871 tp->snd_cwnd++;
2872 tcp_simple_retransmit(sk);
2873 return;
2874 }
2875
2876 /* Otherwise enter Recovery state */
2877 tcp_enter_recovery(sk, (flag & FLAG_ECE));
2878 fast_rexmit = 1;
2879 }
2880
2881 if (do_lost)
2882 tcp_update_scoreboard(sk, fast_rexmit);
2883 tcp_cwnd_reduction(sk, prior_unsacked, fast_rexmit);
2884 tcp_xmit_retransmit_queue(sk);
2885}
2886
2887static inline bool tcp_ack_update_rtt(struct sock *sk, const int flag,
2888 long seq_rtt_us, long sack_rtt_us)
2889{
2890 const struct tcp_sock *tp = tcp_sk(sk);
2891
2892 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2893 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2894 * Karn's algorithm forbids taking RTT if some retransmitted data
2895 * is acked (RFC6298).
2896 */
2897 if (flag & FLAG_RETRANS_DATA_ACKED)
2898 seq_rtt_us = -1L;
2899
2900 if (seq_rtt_us < 0)
2901 seq_rtt_us = sack_rtt_us;
2902
2903 /* RTTM Rule: A TSecr value received in a segment is used to
2904 * update the averaged RTT measurement only if the segment
2905 * acknowledges some new data, i.e., only if it advances the
2906 * left edge of the send window.
2907 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2908 */
2909 if (seq_rtt_us < 0 && tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2910 flag & FLAG_ACKED)
2911 seq_rtt_us = jiffies_to_usecs(tcp_time_stamp - tp->rx_opt.rcv_tsecr);
2912
2913 if (seq_rtt_us < 0)
2914 return false;
2915
2916 tcp_rtt_estimator(sk, seq_rtt_us);
2917 tcp_set_rto(sk);
2918
2919 /* RFC6298: only reset backoff on valid RTT measurement. */
2920 inet_csk(sk)->icsk_backoff = 0;
2921 return true;
2922}
2923
2924/* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2925static void tcp_synack_rtt_meas(struct sock *sk, const u32 synack_stamp)
2926{
2927 struct tcp_sock *tp = tcp_sk(sk);
2928 long seq_rtt_us = -1L;
2929
2930 if (synack_stamp && !tp->total_retrans)
2931 seq_rtt_us = jiffies_to_usecs(tcp_time_stamp - synack_stamp);
2932
2933 /* If the ACK acks both the SYNACK and the (Fast Open'd) data packets
2934 * sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack()
2935 */
2936 if (!tp->srtt_us)
2937 tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, seq_rtt_us, -1L);
2938}
2939
2940static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 acked, u32 in_flight)
2941{
2942 const struct inet_connection_sock *icsk = inet_csk(sk);
2943 icsk->icsk_ca_ops->cong_avoid(sk, ack, acked, in_flight);
2944 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
2945}
2946
2947/* Restart timer after forward progress on connection.
2948 * RFC2988 recommends to restart timer to now+rto.
2949 */
2950void tcp_rearm_rto(struct sock *sk)
2951{
2952 const struct inet_connection_sock *icsk = inet_csk(sk);
2953 struct tcp_sock *tp = tcp_sk(sk);
2954
2955 /* If the retrans timer is currently being used by Fast Open
2956 * for SYN-ACK retrans purpose, stay put.
2957 */
2958 if (tp->fastopen_rsk)
2959 return;
2960
2961 if (!tp->packets_out) {
2962 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
2963 } else {
2964 u32 rto = inet_csk(sk)->icsk_rto;
2965 /* Offset the time elapsed after installing regular RTO */
2966 if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
2967 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
2968 struct sk_buff *skb = tcp_write_queue_head(sk);
2969 const u32 rto_time_stamp = TCP_SKB_CB(skb)->when + rto;
2970 s32 delta = (s32)(rto_time_stamp - tcp_time_stamp);
2971 /* delta may not be positive if the socket is locked
2972 * when the retrans timer fires and is rescheduled.
2973 */
2974 if (delta > 0)
2975 rto = delta;
2976 }
2977 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
2978 TCP_RTO_MAX);
2979 }
2980}
2981
2982/* This function is called when the delayed ER timer fires. TCP enters
2983 * fast recovery and performs fast-retransmit.
2984 */
2985void tcp_resume_early_retransmit(struct sock *sk)
2986{
2987 struct tcp_sock *tp = tcp_sk(sk);
2988
2989 tcp_rearm_rto(sk);
2990
2991 /* Stop if ER is disabled after the delayed ER timer is scheduled */
2992 if (!tp->do_early_retrans)
2993 return;
2994
2995 tcp_enter_recovery(sk, false);
2996 tcp_update_scoreboard(sk, 1);
2997 tcp_xmit_retransmit_queue(sk);
2998}
2999
3000/* If we get here, the whole TSO packet has not been acked. */
3001static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
3002{
3003 struct tcp_sock *tp = tcp_sk(sk);
3004 u32 packets_acked;
3005
3006 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
3007
3008 packets_acked = tcp_skb_pcount(skb);
3009 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3010 return 0;
3011 packets_acked -= tcp_skb_pcount(skb);
3012
3013 if (packets_acked) {
3014 BUG_ON(tcp_skb_pcount(skb) == 0);
3015 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
3016 }
3017
3018 return packets_acked;
3019}
3020
3021/* Remove acknowledged frames from the retransmission queue. If our packet
3022 * is before the ack sequence we can discard it as it's confirmed to have
3023 * arrived at the other end.
3024 */
3025static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
3026 u32 prior_snd_una, long sack_rtt_us)
3027{
3028 const struct inet_connection_sock *icsk = inet_csk(sk);
3029 struct skb_mstamp first_ackt, last_ackt, now;
3030 struct tcp_sock *tp = tcp_sk(sk);
3031 u32 prior_sacked = tp->sacked_out;
3032 u32 reord = tp->packets_out;
3033 bool fully_acked = true;
3034 long ca_seq_rtt_us = -1L;
3035 long seq_rtt_us = -1L;
3036 struct sk_buff *skb;
3037 u32 pkts_acked = 0;
3038 bool rtt_update;
3039 int flag = 0;
3040
3041 first_ackt.v64 = 0;
3042
3043 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
3044 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
3045 u8 sacked = scb->sacked;
3046 u32 acked_pcount;
3047
3048 /* Determine how many packets and what bytes were acked, tso and else */
3049 if (after(scb->end_seq, tp->snd_una)) {
3050 if (tcp_skb_pcount(skb) == 1 ||
3051 !after(tp->snd_una, scb->seq))
3052 break;
3053
3054 acked_pcount = tcp_tso_acked(sk, skb);
3055 if (!acked_pcount)
3056 break;
3057
3058 fully_acked = false;
3059 } else {
3060 acked_pcount = tcp_skb_pcount(skb);
3061 }
3062
3063 if (sacked & TCPCB_RETRANS) {
3064 if (sacked & TCPCB_SACKED_RETRANS)
3065 tp->retrans_out -= acked_pcount;
3066 flag |= FLAG_RETRANS_DATA_ACKED;
3067 } else {
3068 last_ackt = skb->skb_mstamp;
3069 WARN_ON_ONCE(last_ackt.v64 == 0);
3070 if (!first_ackt.v64)
3071 first_ackt = last_ackt;
3072
3073 if (!(sacked & TCPCB_SACKED_ACKED))
3074 reord = min(pkts_acked, reord);
3075 if (!after(scb->end_seq, tp->high_seq))
3076 flag |= FLAG_ORIG_SACK_ACKED;
3077 }
3078
3079 if (sacked & TCPCB_SACKED_ACKED)
3080 tp->sacked_out -= acked_pcount;
3081 if (sacked & TCPCB_LOST)
3082 tp->lost_out -= acked_pcount;
3083
3084 tp->packets_out -= acked_pcount;
3085 pkts_acked += acked_pcount;
3086
3087 /* Initial outgoing SYN's get put onto the write_queue
3088 * just like anything else we transmit. It is not
3089 * true data, and if we misinform our callers that
3090 * this ACK acks real data, we will erroneously exit
3091 * connection startup slow start one packet too
3092 * quickly. This is severely frowned upon behavior.
3093 */
3094 if (!(scb->tcp_flags & TCPHDR_SYN)) {
3095 flag |= FLAG_DATA_ACKED;
3096 } else {
3097 flag |= FLAG_SYN_ACKED;
3098 tp->retrans_stamp = 0;
3099 }
3100
3101 if (!fully_acked)
3102 break;
3103
3104 tcp_unlink_write_queue(skb, sk);
3105 sk_wmem_free_skb(sk, skb);
3106 if (skb == tp->retransmit_skb_hint)
3107 tp->retransmit_skb_hint = NULL;
3108 if (skb == tp->lost_skb_hint)
3109 tp->lost_skb_hint = NULL;
3110 }
3111
3112 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
3113 tp->snd_up = tp->snd_una;
3114
3115 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
3116 flag |= FLAG_SACK_RENEGING;
3117
3118 skb_mstamp_get(&now);
3119 if (first_ackt.v64) {
3120 seq_rtt_us = skb_mstamp_us_delta(&now, &first_ackt);
3121 ca_seq_rtt_us = skb_mstamp_us_delta(&now, &last_ackt);
3122 }
3123
3124 rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt_us, sack_rtt_us);
3125
3126 if (flag & FLAG_ACKED) {
3127 const struct tcp_congestion_ops *ca_ops
3128 = inet_csk(sk)->icsk_ca_ops;
3129
3130 tcp_rearm_rto(sk);
3131 if (unlikely(icsk->icsk_mtup.probe_size &&
3132 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
3133 tcp_mtup_probe_success(sk);
3134 }
3135
3136 if (tcp_is_reno(tp)) {
3137 tcp_remove_reno_sacks(sk, pkts_acked);
3138 } else {
3139 int delta;
3140
3141 /* Non-retransmitted hole got filled? That's reordering */
3142 if (reord < prior_fackets)
3143 tcp_update_reordering(sk, tp->fackets_out - reord, 0);
3144
3145 delta = tcp_is_fack(tp) ? pkts_acked :
3146 prior_sacked - tp->sacked_out;
3147 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
3148 }
3149
3150 tp->fackets_out -= min(pkts_acked, tp->fackets_out);
3151
3152 if (ca_ops->pkts_acked)
3153 ca_ops->pkts_acked(sk, pkts_acked, ca_seq_rtt_us);
3154
3155 } else if (skb && rtt_update && sack_rtt_us >= 0 &&
3156 sack_rtt_us > skb_mstamp_us_delta(&now, &skb->skb_mstamp)) {
3157 /* Do not re-arm RTO if the sack RTT is measured from data sent
3158 * after when the head was last (re)transmitted. Otherwise the
3159 * timeout may continue to extend in loss recovery.
3160 */
3161 tcp_rearm_rto(sk);
3162 }
3163
3164#if FASTRETRANS_DEBUG > 0
3165 WARN_ON((int)tp->sacked_out < 0);
3166 WARN_ON((int)tp->lost_out < 0);
3167 WARN_ON((int)tp->retrans_out < 0);
3168 if (!tp->packets_out && tcp_is_sack(tp)) {
3169 icsk = inet_csk(sk);
3170 if (tp->lost_out) {
3171 pr_debug("Leak l=%u %d\n",
3172 tp->lost_out, icsk->icsk_ca_state);
3173 tp->lost_out = 0;
3174 }
3175 if (tp->sacked_out) {
3176 pr_debug("Leak s=%u %d\n",
3177 tp->sacked_out, icsk->icsk_ca_state);
3178 tp->sacked_out = 0;
3179 }
3180 if (tp->retrans_out) {
3181 pr_debug("Leak r=%u %d\n",
3182 tp->retrans_out, icsk->icsk_ca_state);
3183 tp->retrans_out = 0;
3184 }
3185 }
3186#endif
3187 return flag;
3188}
3189
3190static void tcp_ack_probe(struct sock *sk)
3191{
3192 const struct tcp_sock *tp = tcp_sk(sk);
3193 struct inet_connection_sock *icsk = inet_csk(sk);
3194
3195 /* Was it a usable window open? */
3196
3197 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) {
3198 icsk->icsk_backoff = 0;
3199 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
3200 /* Socket must be waked up by subsequent tcp_data_snd_check().
3201 * This function is not for random using!
3202 */
3203 } else {
3204 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3205 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
3206 TCP_RTO_MAX);
3207 }
3208}
3209
3210static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag)
3211{
3212 return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
3213 inet_csk(sk)->icsk_ca_state != TCP_CA_Open;
3214}
3215
3216/* Decide wheather to run the increase function of congestion control. */
3217static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
3218{
3219 if (tcp_in_cwnd_reduction(sk))
3220 return false;
3221
3222 /* If reordering is high then always grow cwnd whenever data is
3223 * delivered regardless of its ordering. Otherwise stay conservative
3224 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3225 * new SACK or ECE mark may first advance cwnd here and later reduce
3226 * cwnd in tcp_fastretrans_alert() based on more states.
3227 */
3228 if (tcp_sk(sk)->reordering > sysctl_tcp_reordering)
3229 return flag & FLAG_FORWARD_PROGRESS;
3230
3231 return flag & FLAG_DATA_ACKED;
3232}
3233
3234/* Check that window update is acceptable.
3235 * The function assumes that snd_una<=ack<=snd_next.
3236 */
3237static inline bool tcp_may_update_window(const struct tcp_sock *tp,
3238 const u32 ack, const u32 ack_seq,
3239 const u32 nwin)
3240{
3241 return after(ack, tp->snd_una) ||
3242 after(ack_seq, tp->snd_wl1) ||
3243 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd);
3244}
3245
3246/* Update our send window.
3247 *
3248 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3249 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3250 */
3251static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack,
3252 u32 ack_seq)
3253{
3254 struct tcp_sock *tp = tcp_sk(sk);
3255 int flag = 0;
3256 u32 nwin = ntohs(tcp_hdr(skb)->window);
3257
3258 if (likely(!tcp_hdr(skb)->syn))
3259 nwin <<= tp->rx_opt.snd_wscale;
3260
3261 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
3262 flag |= FLAG_WIN_UPDATE;
3263 tcp_update_wl(tp, ack_seq);
3264
3265 if (tp->snd_wnd != nwin) {
3266 tp->snd_wnd = nwin;
3267
3268 /* Note, it is the only place, where
3269 * fast path is recovered for sending TCP.
3270 */
3271 tp->pred_flags = 0;
3272 tcp_fast_path_check(sk);
3273
3274 if (nwin > tp->max_window) {
3275 tp->max_window = nwin;
3276 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
3277 }
3278 }
3279 }
3280
3281 tp->snd_una = ack;
3282
3283 return flag;
3284}
3285
3286/* RFC 5961 7 [ACK Throttling] */
3287static void tcp_send_challenge_ack(struct sock *sk)
3288{
3289 /* unprotected vars, we dont care of overwrites */
3290 static u32 challenge_timestamp;
3291 static unsigned int challenge_count;
3292 u32 now = jiffies / HZ;
3293
3294 if (now != challenge_timestamp) {
3295 challenge_timestamp = now;
3296 challenge_count = 0;
3297 }
3298 if (++challenge_count <= sysctl_tcp_challenge_ack_limit) {
3299 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK);
3300 tcp_send_ack(sk);
3301 }
3302}
3303
3304static void tcp_store_ts_recent(struct tcp_sock *tp)
3305{
3306 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
3307 tp->rx_opt.ts_recent_stamp = get_seconds();
3308}
3309
3310static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3311{
3312 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3313 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3314 * extra check below makes sure this can only happen
3315 * for pure ACK frames. -DaveM
3316 *
3317 * Not only, also it occurs for expired timestamps.
3318 */
3319
3320 if (tcp_paws_check(&tp->rx_opt, 0))
3321 tcp_store_ts_recent(tp);
3322 }
3323}
3324
3325/* This routine deals with acks during a TLP episode.
3326 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3327 */
3328static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag)
3329{
3330 struct tcp_sock *tp = tcp_sk(sk);
3331 bool is_tlp_dupack = (ack == tp->tlp_high_seq) &&
3332 !(flag & (FLAG_SND_UNA_ADVANCED |
3333 FLAG_NOT_DUP | FLAG_DATA_SACKED));
3334
3335 /* Mark the end of TLP episode on receiving TLP dupack or when
3336 * ack is after tlp_high_seq.
3337 */
3338 if (is_tlp_dupack) {
3339 tp->tlp_high_seq = 0;
3340 return;
3341 }
3342
3343 if (after(ack, tp->tlp_high_seq)) {
3344 tp->tlp_high_seq = 0;
3345 /* Don't reduce cwnd if DSACK arrives for TLP retrans. */
3346 if (!(flag & FLAG_DSACKING_ACK)) {
3347 tcp_init_cwnd_reduction(sk, true);
3348 tcp_set_ca_state(sk, TCP_CA_CWR);
3349 tcp_end_cwnd_reduction(sk);
3350 tcp_try_keep_open(sk);
3351 NET_INC_STATS_BH(sock_net(sk),
3352 LINUX_MIB_TCPLOSSPROBERECOVERY);
3353 }
3354 }
3355}
3356
3357/* This routine deals with incoming acks, but not outgoing ones. */
3358static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
3359{
3360 struct inet_connection_sock *icsk = inet_csk(sk);
3361 struct tcp_sock *tp = tcp_sk(sk);
3362 u32 prior_snd_una = tp->snd_una;
3363 u32 ack_seq = TCP_SKB_CB(skb)->seq;
3364 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3365 bool is_dupack = false;
3366 u32 prior_in_flight;
3367 u32 prior_fackets;
3368 int prior_packets = tp->packets_out;
3369 const int prior_unsacked = tp->packets_out - tp->sacked_out;
3370 int acked = 0; /* Number of packets newly acked */
3371 long sack_rtt_us = -1L;
3372
3373 /* If the ack is older than previous acks
3374 * then we can probably ignore it.
3375 */
3376 if (before(ack, prior_snd_una)) {
3377 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3378 if (before(ack, prior_snd_una - tp->max_window)) {
3379 tcp_send_challenge_ack(sk);
3380 return -1;
3381 }
3382 goto old_ack;
3383 }
3384
3385 /* If the ack includes data we haven't sent yet, discard
3386 * this segment (RFC793 Section 3.9).
3387 */
3388 if (after(ack, tp->snd_nxt))
3389 goto invalid_ack;
3390
3391 if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
3392 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
3393 tcp_rearm_rto(sk);
3394
3395 if (after(ack, prior_snd_una))
3396 flag |= FLAG_SND_UNA_ADVANCED;
3397
3398 prior_fackets = tp->fackets_out;
3399 prior_in_flight = tcp_packets_in_flight(tp);
3400
3401 /* ts_recent update must be made after we are sure that the packet
3402 * is in window.
3403 */
3404 if (flag & FLAG_UPDATE_TS_RECENT)
3405 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
3406
3407 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
3408 /* Window is constant, pure forward advance.
3409 * No more checks are required.
3410 * Note, we use the fact that SND.UNA>=SND.WL2.
3411 */
3412 tcp_update_wl(tp, ack_seq);
3413 tp->snd_una = ack;
3414 flag |= FLAG_WIN_UPDATE;
3415
3416 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
3417
3418 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS);
3419 } else {
3420 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
3421 flag |= FLAG_DATA;
3422 else
3423 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS);
3424
3425 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
3426
3427 if (TCP_SKB_CB(skb)->sacked)
3428 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
3429 &sack_rtt_us);
3430
3431 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb)))
3432 flag |= FLAG_ECE;
3433
3434 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
3435 }
3436
3437 /* We passed data and got it acked, remove any soft error
3438 * log. Something worked...
3439 */
3440 sk->sk_err_soft = 0;
3441 icsk->icsk_probes_out = 0;
3442 tp->rcv_tstamp = tcp_time_stamp;
3443 if (!prior_packets)
3444 goto no_queue;
3445
3446 /* See if we can take anything off of the retransmit queue. */
3447 acked = tp->packets_out;
3448 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una,
3449 sack_rtt_us);
3450 acked -= tp->packets_out;
3451
3452 /* Advance cwnd if state allows */
3453 if (tcp_may_raise_cwnd(sk, flag))
3454 tcp_cong_avoid(sk, ack, acked, prior_in_flight);
3455
3456 if (tcp_ack_is_dubious(sk, flag)) {
3457 is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
3458 tcp_fastretrans_alert(sk, acked, prior_unsacked,
3459 is_dupack, flag);
3460 }
3461 if (tp->tlp_high_seq)
3462 tcp_process_tlp_ack(sk, ack, flag);
3463
3464 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) {
3465 struct dst_entry *dst = __sk_dst_get(sk);
3466 if (dst)
3467 dst_confirm(dst);
3468 }
3469
3470 if (icsk->icsk_pending == ICSK_TIME_RETRANS)
3471 tcp_schedule_loss_probe(sk);
3472 tcp_update_pacing_rate(sk);
3473 return 1;
3474
3475no_queue:
3476 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3477 if (flag & FLAG_DSACKING_ACK)
3478 tcp_fastretrans_alert(sk, acked, prior_unsacked,
3479 is_dupack, flag);
3480 /* If this ack opens up a zero window, clear backoff. It was
3481 * being used to time the probes, and is probably far higher than
3482 * it needs to be for normal retransmission.
3483 */
3484 if (tcp_send_head(sk))
3485 tcp_ack_probe(sk);
3486
3487 if (tp->tlp_high_seq)
3488 tcp_process_tlp_ack(sk, ack, flag);
3489 return 1;
3490
3491invalid_ack:
3492 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3493 return -1;
3494
3495old_ack:
3496 /* If data was SACKed, tag it and see if we should send more data.
3497 * If data was DSACKed, see if we can undo a cwnd reduction.
3498 */
3499 if (TCP_SKB_CB(skb)->sacked) {
3500 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
3501 &sack_rtt_us);
3502 tcp_fastretrans_alert(sk, acked, prior_unsacked,
3503 is_dupack, flag);
3504 }
3505
3506 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3507 return 0;
3508}
3509
3510/* Look for tcp options. Normally only called on SYN and SYNACK packets.
3511 * But, this can also be called on packets in the established flow when
3512 * the fast version below fails.
3513 */
3514void tcp_parse_options(const struct sk_buff *skb,
3515 struct tcp_options_received *opt_rx, int estab,
3516 struct tcp_fastopen_cookie *foc)
3517{
3518 const unsigned char *ptr;
3519 const struct tcphdr *th = tcp_hdr(skb);
3520 int length = (th->doff * 4) - sizeof(struct tcphdr);
3521
3522 ptr = (const unsigned char *)(th + 1);
3523 opt_rx->saw_tstamp = 0;
3524
3525 while (length > 0) {
3526 int opcode = *ptr++;
3527 int opsize;
3528
3529 switch (opcode) {
3530 case TCPOPT_EOL:
3531 return;
3532 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3533 length--;
3534 continue;
3535 default:
3536 opsize = *ptr++;
3537 if (opsize < 2) /* "silly options" */
3538 return;
3539 if (opsize > length)
3540 return; /* don't parse partial options */
3541 switch (opcode) {
3542 case TCPOPT_MSS:
3543 if (opsize == TCPOLEN_MSS && th->syn && !estab) {
3544 u16 in_mss = get_unaligned_be16(ptr);
3545 if (in_mss) {
3546 if (opt_rx->user_mss &&
3547 opt_rx->user_mss < in_mss)
3548 in_mss = opt_rx->user_mss;
3549 opt_rx->mss_clamp = in_mss;
3550 }
3551 }
3552 break;
3553 case TCPOPT_WINDOW:
3554 if (opsize == TCPOLEN_WINDOW && th->syn &&
3555 !estab && sysctl_tcp_window_scaling) {
3556 __u8 snd_wscale = *(__u8 *)ptr;
3557 opt_rx->wscale_ok = 1;
3558 if (snd_wscale > 14) {
3559 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3560 __func__,
3561 snd_wscale);
3562 snd_wscale = 14;
3563 }
3564 opt_rx->snd_wscale = snd_wscale;
3565 }
3566 break;
3567 case TCPOPT_TIMESTAMP:
3568 if ((opsize == TCPOLEN_TIMESTAMP) &&
3569 ((estab && opt_rx->tstamp_ok) ||
3570 (!estab && sysctl_tcp_timestamps))) {
3571 opt_rx->saw_tstamp = 1;
3572 opt_rx->rcv_tsval = get_unaligned_be32(ptr);
3573 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
3574 }
3575 break;
3576 case TCPOPT_SACK_PERM:
3577 if (opsize == TCPOLEN_SACK_PERM && th->syn &&
3578 !estab && sysctl_tcp_sack) {
3579 opt_rx->sack_ok = TCP_SACK_SEEN;
3580 tcp_sack_reset(opt_rx);
3581 }
3582 break;
3583
3584 case TCPOPT_SACK:
3585 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
3586 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3587 opt_rx->sack_ok) {
3588 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3589 }
3590 break;
3591#ifdef CONFIG_TCP_MD5SIG
3592 case TCPOPT_MD5SIG:
3593 /*
3594 * The MD5 Hash has already been
3595 * checked (see tcp_v{4,6}_do_rcv()).
3596 */
3597 break;
3598#endif
3599 case TCPOPT_EXP:
3600 /* Fast Open option shares code 254 using a
3601 * 16 bits magic number. It's valid only in
3602 * SYN or SYN-ACK with an even size.
3603 */
3604 if (opsize < TCPOLEN_EXP_FASTOPEN_BASE ||
3605 get_unaligned_be16(ptr) != TCPOPT_FASTOPEN_MAGIC ||
3606 foc == NULL || !th->syn || (opsize & 1))
3607 break;
3608 foc->len = opsize - TCPOLEN_EXP_FASTOPEN_BASE;
3609 if (foc->len >= TCP_FASTOPEN_COOKIE_MIN &&
3610 foc->len <= TCP_FASTOPEN_COOKIE_MAX)
3611 memcpy(foc->val, ptr + 2, foc->len);
3612 else if (foc->len != 0)
3613 foc->len = -1;
3614 break;
3615
3616 }
3617 ptr += opsize-2;
3618 length -= opsize;
3619 }
3620 }
3621}
3622EXPORT_SYMBOL(tcp_parse_options);
3623
3624static bool tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th)
3625{
3626 const __be32 *ptr = (const __be32 *)(th + 1);
3627
3628 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3629 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3630 tp->rx_opt.saw_tstamp = 1;
3631 ++ptr;
3632 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3633 ++ptr;
3634 if (*ptr)
3635 tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset;
3636 else
3637 tp->rx_opt.rcv_tsecr = 0;
3638 return true;
3639 }
3640 return false;
3641}
3642
3643/* Fast parse options. This hopes to only see timestamps.
3644 * If it is wrong it falls back on tcp_parse_options().
3645 */
3646static bool tcp_fast_parse_options(const struct sk_buff *skb,
3647 const struct tcphdr *th, struct tcp_sock *tp)
3648{
3649 /* In the spirit of fast parsing, compare doff directly to constant
3650 * values. Because equality is used, short doff can be ignored here.
3651 */
3652 if (th->doff == (sizeof(*th) / 4)) {
3653 tp->rx_opt.saw_tstamp = 0;
3654 return false;
3655 } else if (tp->rx_opt.tstamp_ok &&
3656 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
3657 if (tcp_parse_aligned_timestamp(tp, th))
3658 return true;
3659 }
3660
3661 tcp_parse_options(skb, &tp->rx_opt, 1, NULL);
3662 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
3663 tp->rx_opt.rcv_tsecr -= tp->tsoffset;
3664
3665 return true;
3666}
3667
3668#ifdef CONFIG_TCP_MD5SIG
3669/*
3670 * Parse MD5 Signature option
3671 */
3672const u8 *tcp_parse_md5sig_option(const struct tcphdr *th)
3673{
3674 int length = (th->doff << 2) - sizeof(*th);
3675 const u8 *ptr = (const u8 *)(th + 1);
3676
3677 /* If the TCP option is too short, we can short cut */
3678 if (length < TCPOLEN_MD5SIG)
3679 return NULL;
3680
3681 while (length > 0) {
3682 int opcode = *ptr++;
3683 int opsize;
3684
3685 switch (opcode) {
3686 case TCPOPT_EOL:
3687 return NULL;
3688 case TCPOPT_NOP:
3689 length--;
3690 continue;
3691 default:
3692 opsize = *ptr++;
3693 if (opsize < 2 || opsize > length)
3694 return NULL;
3695 if (opcode == TCPOPT_MD5SIG)
3696 return opsize == TCPOLEN_MD5SIG ? ptr : NULL;
3697 }
3698 ptr += opsize - 2;
3699 length -= opsize;
3700 }
3701 return NULL;
3702}
3703EXPORT_SYMBOL(tcp_parse_md5sig_option);
3704#endif
3705
3706/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3707 *
3708 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3709 * it can pass through stack. So, the following predicate verifies that
3710 * this segment is not used for anything but congestion avoidance or
3711 * fast retransmit. Moreover, we even are able to eliminate most of such
3712 * second order effects, if we apply some small "replay" window (~RTO)
3713 * to timestamp space.
3714 *
3715 * All these measures still do not guarantee that we reject wrapped ACKs
3716 * on networks with high bandwidth, when sequence space is recycled fastly,
3717 * but it guarantees that such events will be very rare and do not affect
3718 * connection seriously. This doesn't look nice, but alas, PAWS is really
3719 * buggy extension.
3720 *
3721 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3722 * states that events when retransmit arrives after original data are rare.
3723 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3724 * the biggest problem on large power networks even with minor reordering.
3725 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3726 * up to bandwidth of 18Gigabit/sec. 8) ]
3727 */
3728
3729static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
3730{
3731 const struct tcp_sock *tp = tcp_sk(sk);
3732 const struct tcphdr *th = tcp_hdr(skb);
3733 u32 seq = TCP_SKB_CB(skb)->seq;
3734 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3735
3736 return (/* 1. Pure ACK with correct sequence number. */
3737 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
3738
3739 /* 2. ... and duplicate ACK. */
3740 ack == tp->snd_una &&
3741
3742 /* 3. ... and does not update window. */
3743 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
3744
3745 /* 4. ... and sits in replay window. */
3746 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
3747}
3748
3749static inline bool tcp_paws_discard(const struct sock *sk,
3750 const struct sk_buff *skb)
3751{
3752 const struct tcp_sock *tp = tcp_sk(sk);
3753
3754 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
3755 !tcp_disordered_ack(sk, skb);
3756}
3757
3758/* Check segment sequence number for validity.
3759 *
3760 * Segment controls are considered valid, if the segment
3761 * fits to the window after truncation to the window. Acceptability
3762 * of data (and SYN, FIN, of course) is checked separately.
3763 * See tcp_data_queue(), for example.
3764 *
3765 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3766 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3767 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3768 * (borrowed from freebsd)
3769 */
3770
3771static inline bool tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq)
3772{
3773 return !before(end_seq, tp->rcv_wup) &&
3774 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
3775}
3776
3777/* When we get a reset we do this. */
3778void tcp_reset(struct sock *sk)
3779{
3780 /* We want the right error as BSD sees it (and indeed as we do). */
3781 switch (sk->sk_state) {
3782 case TCP_SYN_SENT:
3783 sk->sk_err = ECONNREFUSED;
3784 break;
3785 case TCP_CLOSE_WAIT:
3786 sk->sk_err = EPIPE;
3787 break;
3788 case TCP_CLOSE:
3789 return;
3790 default:
3791 sk->sk_err = ECONNRESET;
3792 }
3793 /* This barrier is coupled with smp_rmb() in tcp_poll() */
3794 smp_wmb();
3795
3796 if (!sock_flag(sk, SOCK_DEAD))
3797 sk->sk_error_report(sk);
3798
3799 tcp_done(sk);
3800}
3801
3802/*
3803 * Process the FIN bit. This now behaves as it is supposed to work
3804 * and the FIN takes effect when it is validly part of sequence
3805 * space. Not before when we get holes.
3806 *
3807 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3808 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3809 * TIME-WAIT)
3810 *
3811 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3812 * close and we go into CLOSING (and later onto TIME-WAIT)
3813 *
3814 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3815 */
3816static void tcp_fin(struct sock *sk)
3817{
3818 struct tcp_sock *tp = tcp_sk(sk);
3819 const struct dst_entry *dst;
3820
3821 inet_csk_schedule_ack(sk);
3822
3823 sk->sk_shutdown |= RCV_SHUTDOWN;
3824 sock_set_flag(sk, SOCK_DONE);
3825
3826 switch (sk->sk_state) {
3827 case TCP_SYN_RECV:
3828 case TCP_ESTABLISHED:
3829 /* Move to CLOSE_WAIT */
3830 tcp_set_state(sk, TCP_CLOSE_WAIT);
3831 dst = __sk_dst_get(sk);
3832 if (!dst || !dst_metric(dst, RTAX_QUICKACK))
3833 inet_csk(sk)->icsk_ack.pingpong = 1;
3834 break;
3835
3836 case TCP_CLOSE_WAIT:
3837 case TCP_CLOSING:
3838 /* Received a retransmission of the FIN, do
3839 * nothing.
3840 */
3841 break;
3842 case TCP_LAST_ACK:
3843 /* RFC793: Remain in the LAST-ACK state. */
3844 break;
3845
3846 case TCP_FIN_WAIT1:
3847 /* This case occurs when a simultaneous close
3848 * happens, we must ack the received FIN and
3849 * enter the CLOSING state.
3850 */
3851 tcp_send_ack(sk);
3852 tcp_set_state(sk, TCP_CLOSING);
3853 break;
3854 case TCP_FIN_WAIT2:
3855 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3856 tcp_send_ack(sk);
3857 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
3858 break;
3859 default:
3860 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3861 * cases we should never reach this piece of code.
3862 */
3863 pr_err("%s: Impossible, sk->sk_state=%d\n",
3864 __func__, sk->sk_state);
3865 break;
3866 }
3867
3868 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3869 * Probably, we should reset in this case. For now drop them.
3870 */
3871 __skb_queue_purge(&tp->out_of_order_queue);
3872 if (tcp_is_sack(tp))
3873 tcp_sack_reset(&tp->rx_opt);
3874 sk_mem_reclaim(sk);
3875
3876 if (!sock_flag(sk, SOCK_DEAD)) {
3877 sk->sk_state_change(sk);
3878
3879 /* Do not send POLL_HUP for half duplex close. */
3880 if (sk->sk_shutdown == SHUTDOWN_MASK ||
3881 sk->sk_state == TCP_CLOSE)
3882 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
3883 else
3884 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
3885 }
3886}
3887
3888static inline bool tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
3889 u32 end_seq)
3890{
3891 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
3892 if (before(seq, sp->start_seq))
3893 sp->start_seq = seq;
3894 if (after(end_seq, sp->end_seq))
3895 sp->end_seq = end_seq;
3896 return true;
3897 }
3898 return false;
3899}
3900
3901static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
3902{
3903 struct tcp_sock *tp = tcp_sk(sk);
3904
3905 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
3906 int mib_idx;
3907
3908 if (before(seq, tp->rcv_nxt))
3909 mib_idx = LINUX_MIB_TCPDSACKOLDSENT;
3910 else
3911 mib_idx = LINUX_MIB_TCPDSACKOFOSENT;
3912
3913 NET_INC_STATS_BH(sock_net(sk), mib_idx);
3914
3915 tp->rx_opt.dsack = 1;
3916 tp->duplicate_sack[0].start_seq = seq;
3917 tp->duplicate_sack[0].end_seq = end_seq;
3918 }
3919}
3920
3921static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
3922{
3923 struct tcp_sock *tp = tcp_sk(sk);
3924
3925 if (!tp->rx_opt.dsack)
3926 tcp_dsack_set(sk, seq, end_seq);
3927 else
3928 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
3929}
3930
3931static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
3932{
3933 struct tcp_sock *tp = tcp_sk(sk);
3934
3935 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
3936 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3937 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
3938 tcp_enter_quickack_mode(sk);
3939
3940 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
3941 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3942
3943 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
3944 end_seq = tp->rcv_nxt;
3945 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
3946 }
3947 }
3948
3949 tcp_send_ack(sk);
3950}
3951
3952/* These routines update the SACK block as out-of-order packets arrive or
3953 * in-order packets close up the sequence space.
3954 */
3955static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
3956{
3957 int this_sack;
3958 struct tcp_sack_block *sp = &tp->selective_acks[0];
3959 struct tcp_sack_block *swalk = sp + 1;
3960
3961 /* See if the recent change to the first SACK eats into
3962 * or hits the sequence space of other SACK blocks, if so coalesce.
3963 */
3964 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
3965 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
3966 int i;
3967
3968 /* Zap SWALK, by moving every further SACK up by one slot.
3969 * Decrease num_sacks.
3970 */
3971 tp->rx_opt.num_sacks--;
3972 for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
3973 sp[i] = sp[i + 1];
3974 continue;
3975 }
3976 this_sack++, swalk++;
3977 }
3978}
3979
3980static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
3981{
3982 struct tcp_sock *tp = tcp_sk(sk);
3983 struct tcp_sack_block *sp = &tp->selective_acks[0];
3984 int cur_sacks = tp->rx_opt.num_sacks;
3985 int this_sack;
3986
3987 if (!cur_sacks)
3988 goto new_sack;
3989
3990 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
3991 if (tcp_sack_extend(sp, seq, end_seq)) {
3992 /* Rotate this_sack to the first one. */
3993 for (; this_sack > 0; this_sack--, sp--)
3994 swap(*sp, *(sp - 1));
3995 if (cur_sacks > 1)
3996 tcp_sack_maybe_coalesce(tp);
3997 return;
3998 }
3999 }
4000
4001 /* Could not find an adjacent existing SACK, build a new one,
4002 * put it at the front, and shift everyone else down. We
4003 * always know there is at least one SACK present already here.
4004 *
4005 * If the sack array is full, forget about the last one.
4006 */
4007 if (this_sack >= TCP_NUM_SACKS) {
4008 this_sack--;
4009 tp->rx_opt.num_sacks--;
4010 sp--;
4011 }
4012 for (; this_sack > 0; this_sack--, sp--)
4013 *sp = *(sp - 1);
4014
4015new_sack:
4016 /* Build the new head SACK, and we're done. */
4017 sp->start_seq = seq;
4018 sp->end_seq = end_seq;
4019 tp->rx_opt.num_sacks++;
4020}
4021
4022/* RCV.NXT advances, some SACKs should be eaten. */
4023
4024static void tcp_sack_remove(struct tcp_sock *tp)
4025{
4026 struct tcp_sack_block *sp = &tp->selective_acks[0];
4027 int num_sacks = tp->rx_opt.num_sacks;
4028 int this_sack;
4029
4030 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4031 if (skb_queue_empty(&tp->out_of_order_queue)) {
4032 tp->rx_opt.num_sacks = 0;
4033 return;
4034 }
4035
4036 for (this_sack = 0; this_sack < num_sacks;) {
4037 /* Check if the start of the sack is covered by RCV.NXT. */
4038 if (!before(tp->rcv_nxt, sp->start_seq)) {
4039 int i;
4040
4041 /* RCV.NXT must cover all the block! */
4042 WARN_ON(before(tp->rcv_nxt, sp->end_seq));
4043
4044 /* Zap this SACK, by moving forward any other SACKS. */
4045 for (i = this_sack+1; i < num_sacks; i++)
4046 tp->selective_acks[i-1] = tp->selective_acks[i];
4047 num_sacks--;
4048 continue;
4049 }
4050 this_sack++;
4051 sp++;
4052 }
4053 tp->rx_opt.num_sacks = num_sacks;
4054}
4055
4056/* This one checks to see if we can put data from the
4057 * out_of_order queue into the receive_queue.
4058 */
4059static void tcp_ofo_queue(struct sock *sk)
4060{
4061 struct tcp_sock *tp = tcp_sk(sk);
4062 __u32 dsack_high = tp->rcv_nxt;
4063 struct sk_buff *skb;
4064
4065 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
4066 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4067 break;
4068
4069 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
4070 __u32 dsack = dsack_high;
4071 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
4072 dsack_high = TCP_SKB_CB(skb)->end_seq;
4073 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack);
4074 }
4075
4076 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4077 SOCK_DEBUG(sk, "ofo packet was already received\n");
4078 __skb_unlink(skb, &tp->out_of_order_queue);
4079 __kfree_skb(skb);
4080 continue;
4081 }
4082 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
4083 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4084 TCP_SKB_CB(skb)->end_seq);
4085
4086 __skb_unlink(skb, &tp->out_of_order_queue);
4087 __skb_queue_tail(&sk->sk_receive_queue, skb);
4088 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4089 if (tcp_hdr(skb)->fin)
4090 tcp_fin(sk);
4091 }
4092}
4093
4094static bool tcp_prune_ofo_queue(struct sock *sk);
4095static int tcp_prune_queue(struct sock *sk);
4096
4097static int tcp_try_rmem_schedule(struct sock *sk, struct sk_buff *skb,
4098 unsigned int size)
4099{
4100 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
4101 !sk_rmem_schedule(sk, skb, size)) {
4102
4103 if (tcp_prune_queue(sk) < 0)
4104 return -1;
4105
4106 if (!sk_rmem_schedule(sk, skb, size)) {
4107 if (!tcp_prune_ofo_queue(sk))
4108 return -1;
4109
4110 if (!sk_rmem_schedule(sk, skb, size))
4111 return -1;
4112 }
4113 }
4114 return 0;
4115}
4116
4117/**
4118 * tcp_try_coalesce - try to merge skb to prior one
4119 * @sk: socket
4120 * @to: prior buffer
4121 * @from: buffer to add in queue
4122 * @fragstolen: pointer to boolean
4123 *
4124 * Before queueing skb @from after @to, try to merge them
4125 * to reduce overall memory use and queue lengths, if cost is small.
4126 * Packets in ofo or receive queues can stay a long time.
4127 * Better try to coalesce them right now to avoid future collapses.
4128 * Returns true if caller should free @from instead of queueing it
4129 */
4130static bool tcp_try_coalesce(struct sock *sk,
4131 struct sk_buff *to,
4132 struct sk_buff *from,
4133 bool *fragstolen)
4134{
4135 int delta;
4136
4137 *fragstolen = false;
4138
4139 if (tcp_hdr(from)->fin)
4140 return false;
4141
4142 /* Its possible this segment overlaps with prior segment in queue */
4143 if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq)
4144 return false;
4145
4146 if (!skb_try_coalesce(to, from, fragstolen, &delta))
4147 return false;
4148
4149 atomic_add(delta, &sk->sk_rmem_alloc);
4150 sk_mem_charge(sk, delta);
4151 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE);
4152 TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq;
4153 TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq;
4154 return true;
4155}
4156
4157static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
4158{
4159 struct tcp_sock *tp = tcp_sk(sk);
4160 struct sk_buff *skb1;
4161 u32 seq, end_seq;
4162
4163 TCP_ECN_check_ce(tp, skb);
4164
4165 if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
4166 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFODROP);
4167 __kfree_skb(skb);
4168 return;
4169 }
4170
4171 /* Disable header prediction. */
4172 tp->pred_flags = 0;
4173 inet_csk_schedule_ack(sk);
4174
4175 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
4176 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
4177 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4178
4179 skb1 = skb_peek_tail(&tp->out_of_order_queue);
4180 if (!skb1) {
4181 /* Initial out of order segment, build 1 SACK. */
4182 if (tcp_is_sack(tp)) {
4183 tp->rx_opt.num_sacks = 1;
4184 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
4185 tp->selective_acks[0].end_seq =
4186 TCP_SKB_CB(skb)->end_seq;
4187 }
4188 __skb_queue_head(&tp->out_of_order_queue, skb);
4189 goto end;
4190 }
4191
4192 seq = TCP_SKB_CB(skb)->seq;
4193 end_seq = TCP_SKB_CB(skb)->end_seq;
4194
4195 if (seq == TCP_SKB_CB(skb1)->end_seq) {
4196 bool fragstolen;
4197
4198 if (!tcp_try_coalesce(sk, skb1, skb, &fragstolen)) {
4199 __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
4200 } else {
4201 tcp_grow_window(sk, skb);
4202 kfree_skb_partial(skb, fragstolen);
4203 skb = NULL;
4204 }
4205
4206 if (!tp->rx_opt.num_sacks ||
4207 tp->selective_acks[0].end_seq != seq)
4208 goto add_sack;
4209
4210 /* Common case: data arrive in order after hole. */
4211 tp->selective_acks[0].end_seq = end_seq;
4212 goto end;
4213 }
4214
4215 /* Find place to insert this segment. */
4216 while (1) {
4217 if (!after(TCP_SKB_CB(skb1)->seq, seq))
4218 break;
4219 if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) {
4220 skb1 = NULL;
4221 break;
4222 }
4223 skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1);
4224 }
4225
4226 /* Do skb overlap to previous one? */
4227 if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) {
4228 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4229 /* All the bits are present. Drop. */
4230 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
4231 __kfree_skb(skb);
4232 skb = NULL;
4233 tcp_dsack_set(sk, seq, end_seq);
4234 goto add_sack;
4235 }
4236 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
4237 /* Partial overlap. */
4238 tcp_dsack_set(sk, seq,
4239 TCP_SKB_CB(skb1)->end_seq);
4240 } else {
4241 if (skb_queue_is_first(&tp->out_of_order_queue,
4242 skb1))
4243 skb1 = NULL;
4244 else
4245 skb1 = skb_queue_prev(
4246 &tp->out_of_order_queue,
4247 skb1);
4248 }
4249 }
4250 if (!skb1)
4251 __skb_queue_head(&tp->out_of_order_queue, skb);
4252 else
4253 __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
4254
4255 /* And clean segments covered by new one as whole. */
4256 while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) {
4257 skb1 = skb_queue_next(&tp->out_of_order_queue, skb);
4258
4259 if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
4260 break;
4261 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4262 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4263 end_seq);
4264 break;
4265 }
4266 __skb_unlink(skb1, &tp->out_of_order_queue);
4267 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4268 TCP_SKB_CB(skb1)->end_seq);
4269 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
4270 __kfree_skb(skb1);
4271 }
4272
4273add_sack:
4274 if (tcp_is_sack(tp))
4275 tcp_sack_new_ofo_skb(sk, seq, end_seq);
4276end:
4277 if (skb) {
4278 tcp_grow_window(sk, skb);
4279 skb_set_owner_r(skb, sk);
4280 }
4281}
4282
4283static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen,
4284 bool *fragstolen)
4285{
4286 int eaten;
4287 struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
4288
4289 __skb_pull(skb, hdrlen);
4290 eaten = (tail &&
4291 tcp_try_coalesce(sk, tail, skb, fragstolen)) ? 1 : 0;
4292 tcp_sk(sk)->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4293 if (!eaten) {
4294 __skb_queue_tail(&sk->sk_receive_queue, skb);
4295 skb_set_owner_r(skb, sk);
4296 }
4297 return eaten;
4298}
4299
4300int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
4301{
4302 struct sk_buff *skb = NULL;
4303 struct tcphdr *th;
4304 bool fragstolen;
4305
4306 if (size == 0)
4307 return 0;
4308
4309 skb = alloc_skb(size + sizeof(*th), sk->sk_allocation);
4310 if (!skb)
4311 goto err;
4312
4313 if (tcp_try_rmem_schedule(sk, skb, size + sizeof(*th)))
4314 goto err_free;
4315
4316 th = (struct tcphdr *)skb_put(skb, sizeof(*th));
4317 skb_reset_transport_header(skb);
4318 memset(th, 0, sizeof(*th));
4319
4320 if (memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size))
4321 goto err_free;
4322
4323 TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;
4324 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size;
4325 TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1;
4326
4327 if (tcp_queue_rcv(sk, skb, sizeof(*th), &fragstolen)) {
4328 WARN_ON_ONCE(fragstolen); /* should not happen */
4329 __kfree_skb(skb);
4330 }
4331 return size;
4332
4333err_free:
4334 kfree_skb(skb);
4335err:
4336 return -ENOMEM;
4337}
4338
4339static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
4340{
4341 const struct tcphdr *th = tcp_hdr(skb);
4342 struct tcp_sock *tp = tcp_sk(sk);
4343 int eaten = -1;
4344 bool fragstolen = false;
4345
4346 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
4347 goto drop;
4348
4349 skb_dst_drop(skb);
4350 __skb_pull(skb, th->doff * 4);
4351
4352 TCP_ECN_accept_cwr(tp, skb);
4353
4354 tp->rx_opt.dsack = 0;
4355
4356 /* Queue data for delivery to the user.
4357 * Packets in sequence go to the receive queue.
4358 * Out of sequence packets to the out_of_order_queue.
4359 */
4360 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4361 if (tcp_receive_window(tp) == 0)
4362 goto out_of_window;
4363
4364 /* Ok. In sequence. In window. */
4365 if (tp->ucopy.task == current &&
4366 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
4367 sock_owned_by_user(sk) && !tp->urg_data) {
4368 int chunk = min_t(unsigned int, skb->len,
4369 tp->ucopy.len);
4370
4371 __set_current_state(TASK_RUNNING);
4372
4373 local_bh_enable();
4374 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
4375 tp->ucopy.len -= chunk;
4376 tp->copied_seq += chunk;
4377 eaten = (chunk == skb->len);
4378 tcp_rcv_space_adjust(sk);
4379 }
4380 local_bh_disable();
4381 }
4382
4383 if (eaten <= 0) {
4384queue_and_out:
4385 if (eaten < 0 &&
4386 tcp_try_rmem_schedule(sk, skb, skb->truesize))
4387 goto drop;
4388
4389 eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen);
4390 }
4391 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4392 if (skb->len)
4393 tcp_event_data_recv(sk, skb);
4394 if (th->fin)
4395 tcp_fin(sk);
4396
4397 if (!skb_queue_empty(&tp->out_of_order_queue)) {
4398 tcp_ofo_queue(sk);
4399
4400 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4401 * gap in queue is filled.
4402 */
4403 if (skb_queue_empty(&tp->out_of_order_queue))
4404 inet_csk(sk)->icsk_ack.pingpong = 0;
4405 }
4406
4407 if (tp->rx_opt.num_sacks)
4408 tcp_sack_remove(tp);
4409
4410 tcp_fast_path_check(sk);
4411
4412 if (eaten > 0)
4413 kfree_skb_partial(skb, fragstolen);
4414 if (!sock_flag(sk, SOCK_DEAD))
4415 sk->sk_data_ready(sk);
4416 return;
4417 }
4418
4419 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4420 /* A retransmit, 2nd most common case. Force an immediate ack. */
4421 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4422 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4423
4424out_of_window:
4425 tcp_enter_quickack_mode(sk);
4426 inet_csk_schedule_ack(sk);
4427drop:
4428 __kfree_skb(skb);
4429 return;
4430 }
4431
4432 /* Out of window. F.e. zero window probe. */
4433 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
4434 goto out_of_window;
4435
4436 tcp_enter_quickack_mode(sk);
4437
4438 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4439 /* Partial packet, seq < rcv_next < end_seq */
4440 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
4441 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4442 TCP_SKB_CB(skb)->end_seq);
4443
4444 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
4445
4446 /* If window is closed, drop tail of packet. But after
4447 * remembering D-SACK for its head made in previous line.
4448 */
4449 if (!tcp_receive_window(tp))
4450 goto out_of_window;
4451 goto queue_and_out;
4452 }
4453
4454 tcp_data_queue_ofo(sk, skb);
4455}
4456
4457static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
4458 struct sk_buff_head *list)
4459{
4460 struct sk_buff *next = NULL;
4461
4462 if (!skb_queue_is_last(list, skb))
4463 next = skb_queue_next(list, skb);
4464
4465 __skb_unlink(skb, list);
4466 __kfree_skb(skb);
4467 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
4468
4469 return next;
4470}
4471
4472/* Collapse contiguous sequence of skbs head..tail with
4473 * sequence numbers start..end.
4474 *
4475 * If tail is NULL, this means until the end of the list.
4476 *
4477 * Segments with FIN/SYN are not collapsed (only because this
4478 * simplifies code)
4479 */
4480static void
4481tcp_collapse(struct sock *sk, struct sk_buff_head *list,
4482 struct sk_buff *head, struct sk_buff *tail,
4483 u32 start, u32 end)
4484{
4485 struct sk_buff *skb, *n;
4486 bool end_of_skbs;
4487
4488 /* First, check that queue is collapsible and find
4489 * the point where collapsing can be useful. */
4490 skb = head;
4491restart:
4492 end_of_skbs = true;
4493 skb_queue_walk_from_safe(list, skb, n) {
4494 if (skb == tail)
4495 break;
4496 /* No new bits? It is possible on ofo queue. */
4497 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4498 skb = tcp_collapse_one(sk, skb, list);
4499 if (!skb)
4500 break;
4501 goto restart;
4502 }
4503
4504 /* The first skb to collapse is:
4505 * - not SYN/FIN and
4506 * - bloated or contains data before "start" or
4507 * overlaps to the next one.
4508 */
4509 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin &&
4510 (tcp_win_from_space(skb->truesize) > skb->len ||
4511 before(TCP_SKB_CB(skb)->seq, start))) {
4512 end_of_skbs = false;
4513 break;
4514 }
4515
4516 if (!skb_queue_is_last(list, skb)) {
4517 struct sk_buff *next = skb_queue_next(list, skb);
4518 if (next != tail &&
4519 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) {
4520 end_of_skbs = false;
4521 break;
4522 }
4523 }
4524
4525 /* Decided to skip this, advance start seq. */
4526 start = TCP_SKB_CB(skb)->end_seq;
4527 }
4528 if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin)
4529 return;
4530
4531 while (before(start, end)) {
4532 struct sk_buff *nskb;
4533 unsigned int header = skb_headroom(skb);
4534 int copy = SKB_MAX_ORDER(header, 0);
4535
4536 /* Too big header? This can happen with IPv6. */
4537 if (copy < 0)
4538 return;
4539 if (end - start < copy)
4540 copy = end - start;
4541 nskb = alloc_skb(copy + header, GFP_ATOMIC);
4542 if (!nskb)
4543 return;
4544
4545 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head);
4546 skb_set_network_header(nskb, (skb_network_header(skb) -
4547 skb->head));
4548 skb_set_transport_header(nskb, (skb_transport_header(skb) -
4549 skb->head));
4550 skb_reserve(nskb, header);
4551 memcpy(nskb->head, skb->head, header);
4552 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
4553 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
4554 __skb_queue_before(list, skb, nskb);
4555 skb_set_owner_r(nskb, sk);
4556
4557 /* Copy data, releasing collapsed skbs. */
4558 while (copy > 0) {
4559 int offset = start - TCP_SKB_CB(skb)->seq;
4560 int size = TCP_SKB_CB(skb)->end_seq - start;
4561
4562 BUG_ON(offset < 0);
4563 if (size > 0) {
4564 size = min(copy, size);
4565 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
4566 BUG();
4567 TCP_SKB_CB(nskb)->end_seq += size;
4568 copy -= size;
4569 start += size;
4570 }
4571 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4572 skb = tcp_collapse_one(sk, skb, list);
4573 if (!skb ||
4574 skb == tail ||
4575 tcp_hdr(skb)->syn ||
4576 tcp_hdr(skb)->fin)
4577 return;
4578 }
4579 }
4580 }
4581}
4582
4583/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4584 * and tcp_collapse() them until all the queue is collapsed.
4585 */
4586static void tcp_collapse_ofo_queue(struct sock *sk)
4587{
4588 struct tcp_sock *tp = tcp_sk(sk);
4589 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
4590 struct sk_buff *head;
4591 u32 start, end;
4592
4593 if (skb == NULL)
4594 return;
4595
4596 start = TCP_SKB_CB(skb)->seq;
4597 end = TCP_SKB_CB(skb)->end_seq;
4598 head = skb;
4599
4600 for (;;) {
4601 struct sk_buff *next = NULL;
4602
4603 if (!skb_queue_is_last(&tp->out_of_order_queue, skb))
4604 next = skb_queue_next(&tp->out_of_order_queue, skb);
4605 skb = next;
4606
4607 /* Segment is terminated when we see gap or when
4608 * we are at the end of all the queue. */
4609 if (!skb ||
4610 after(TCP_SKB_CB(skb)->seq, end) ||
4611 before(TCP_SKB_CB(skb)->end_seq, start)) {
4612 tcp_collapse(sk, &tp->out_of_order_queue,
4613 head, skb, start, end);
4614 head = skb;
4615 if (!skb)
4616 break;
4617 /* Start new segment */
4618 start = TCP_SKB_CB(skb)->seq;
4619 end = TCP_SKB_CB(skb)->end_seq;
4620 } else {
4621 if (before(TCP_SKB_CB(skb)->seq, start))
4622 start = TCP_SKB_CB(skb)->seq;
4623 if (after(TCP_SKB_CB(skb)->end_seq, end))
4624 end = TCP_SKB_CB(skb)->end_seq;
4625 }
4626 }
4627}
4628
4629/*
4630 * Purge the out-of-order queue.
4631 * Return true if queue was pruned.
4632 */
4633static bool tcp_prune_ofo_queue(struct sock *sk)
4634{
4635 struct tcp_sock *tp = tcp_sk(sk);
4636 bool res = false;
4637
4638 if (!skb_queue_empty(&tp->out_of_order_queue)) {
4639 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED);
4640 __skb_queue_purge(&tp->out_of_order_queue);
4641
4642 /* Reset SACK state. A conforming SACK implementation will
4643 * do the same at a timeout based retransmit. When a connection
4644 * is in a sad state like this, we care only about integrity
4645 * of the connection not performance.
4646 */
4647 if (tp->rx_opt.sack_ok)
4648 tcp_sack_reset(&tp->rx_opt);
4649 sk_mem_reclaim(sk);
4650 res = true;
4651 }
4652 return res;
4653}
4654
4655/* Reduce allocated memory if we can, trying to get
4656 * the socket within its memory limits again.
4657 *
4658 * Return less than zero if we should start dropping frames
4659 * until the socket owning process reads some of the data
4660 * to stabilize the situation.
4661 */
4662static int tcp_prune_queue(struct sock *sk)
4663{
4664 struct tcp_sock *tp = tcp_sk(sk);
4665
4666 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
4667
4668 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED);
4669
4670 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
4671 tcp_clamp_window(sk);
4672 else if (sk_under_memory_pressure(sk))
4673 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
4674
4675 tcp_collapse_ofo_queue(sk);
4676 if (!skb_queue_empty(&sk->sk_receive_queue))
4677 tcp_collapse(sk, &sk->sk_receive_queue,
4678 skb_peek(&sk->sk_receive_queue),
4679 NULL,
4680 tp->copied_seq, tp->rcv_nxt);
4681 sk_mem_reclaim(sk);
4682
4683 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4684 return 0;
4685
4686 /* Collapsing did not help, destructive actions follow.
4687 * This must not ever occur. */
4688
4689 tcp_prune_ofo_queue(sk);
4690
4691 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4692 return 0;
4693
4694 /* If we are really being abused, tell the caller to silently
4695 * drop receive data on the floor. It will get retransmitted
4696 * and hopefully then we'll have sufficient space.
4697 */
4698 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED);
4699
4700 /* Massive buffer overcommit. */
4701 tp->pred_flags = 0;
4702 return -1;
4703}
4704
4705/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4706 * As additional protections, we do not touch cwnd in retransmission phases,
4707 * and if application hit its sndbuf limit recently.
4708 */
4709void tcp_cwnd_application_limited(struct sock *sk)
4710{
4711 struct tcp_sock *tp = tcp_sk(sk);
4712
4713 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
4714 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
4715 /* Limited by application or receiver window. */
4716 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
4717 u32 win_used = max(tp->snd_cwnd_used, init_win);
4718 if (win_used < tp->snd_cwnd) {
4719 tp->snd_ssthresh = tcp_current_ssthresh(sk);
4720 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
4721 }
4722 tp->snd_cwnd_used = 0;
4723 }
4724 tp->snd_cwnd_stamp = tcp_time_stamp;
4725}
4726
4727static bool tcp_should_expand_sndbuf(const struct sock *sk)
4728{
4729 const struct tcp_sock *tp = tcp_sk(sk);
4730
4731 /* If the user specified a specific send buffer setting, do
4732 * not modify it.
4733 */
4734 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
4735 return false;
4736
4737 /* If we are under global TCP memory pressure, do not expand. */
4738 if (sk_under_memory_pressure(sk))
4739 return false;
4740
4741 /* If we are under soft global TCP memory pressure, do not expand. */
4742 if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0))
4743 return false;
4744
4745 /* If we filled the congestion window, do not expand. */
4746 if (tp->packets_out >= tp->snd_cwnd)
4747 return false;
4748
4749 return true;
4750}
4751
4752/* When incoming ACK allowed to free some skb from write_queue,
4753 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4754 * on the exit from tcp input handler.
4755 *
4756 * PROBLEM: sndbuf expansion does not work well with largesend.
4757 */
4758static void tcp_new_space(struct sock *sk)
4759{
4760 struct tcp_sock *tp = tcp_sk(sk);
4761
4762 if (tcp_should_expand_sndbuf(sk)) {
4763 tcp_sndbuf_expand(sk);
4764 tp->snd_cwnd_stamp = tcp_time_stamp;
4765 }
4766
4767 sk->sk_write_space(sk);
4768}
4769
4770static void tcp_check_space(struct sock *sk)
4771{
4772 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
4773 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
4774 if (sk->sk_socket &&
4775 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
4776 tcp_new_space(sk);
4777 }
4778}
4779
4780static inline void tcp_data_snd_check(struct sock *sk)
4781{
4782 tcp_push_pending_frames(sk);
4783 tcp_check_space(sk);
4784}
4785
4786/*
4787 * Check if sending an ack is needed.
4788 */
4789static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
4790{
4791 struct tcp_sock *tp = tcp_sk(sk);
4792
4793 /* More than one full frame received... */
4794 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
4795 /* ... and right edge of window advances far enough.
4796 * (tcp_recvmsg() will send ACK otherwise). Or...
4797 */
4798 __tcp_select_window(sk) >= tp->rcv_wnd) ||
4799 /* We ACK each frame or... */
4800 tcp_in_quickack_mode(sk) ||
4801 /* We have out of order data. */
4802 (ofo_possible && skb_peek(&tp->out_of_order_queue))) {
4803 /* Then ack it now */
4804 tcp_send_ack(sk);
4805 } else {
4806 /* Else, send delayed ack. */
4807 tcp_send_delayed_ack(sk);
4808 }
4809}
4810
4811static inline void tcp_ack_snd_check(struct sock *sk)
4812{
4813 if (!inet_csk_ack_scheduled(sk)) {
4814 /* We sent a data segment already. */
4815 return;
4816 }
4817 __tcp_ack_snd_check(sk, 1);
4818}
4819
4820/*
4821 * This routine is only called when we have urgent data
4822 * signaled. Its the 'slow' part of tcp_urg. It could be
4823 * moved inline now as tcp_urg is only called from one
4824 * place. We handle URGent data wrong. We have to - as
4825 * BSD still doesn't use the correction from RFC961.
4826 * For 1003.1g we should support a new option TCP_STDURG to permit
4827 * either form (or just set the sysctl tcp_stdurg).
4828 */
4829
4830static void tcp_check_urg(struct sock *sk, const struct tcphdr *th)
4831{
4832 struct tcp_sock *tp = tcp_sk(sk);
4833 u32 ptr = ntohs(th->urg_ptr);
4834
4835 if (ptr && !sysctl_tcp_stdurg)
4836 ptr--;
4837 ptr += ntohl(th->seq);
4838
4839 /* Ignore urgent data that we've already seen and read. */
4840 if (after(tp->copied_seq, ptr))
4841 return;
4842
4843 /* Do not replay urg ptr.
4844 *
4845 * NOTE: interesting situation not covered by specs.
4846 * Misbehaving sender may send urg ptr, pointing to segment,
4847 * which we already have in ofo queue. We are not able to fetch
4848 * such data and will stay in TCP_URG_NOTYET until will be eaten
4849 * by recvmsg(). Seems, we are not obliged to handle such wicked
4850 * situations. But it is worth to think about possibility of some
4851 * DoSes using some hypothetical application level deadlock.
4852 */
4853 if (before(ptr, tp->rcv_nxt))
4854 return;
4855
4856 /* Do we already have a newer (or duplicate) urgent pointer? */
4857 if (tp->urg_data && !after(ptr, tp->urg_seq))
4858 return;
4859
4860 /* Tell the world about our new urgent pointer. */
4861 sk_send_sigurg(sk);
4862
4863 /* We may be adding urgent data when the last byte read was
4864 * urgent. To do this requires some care. We cannot just ignore
4865 * tp->copied_seq since we would read the last urgent byte again
4866 * as data, nor can we alter copied_seq until this data arrives
4867 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4868 *
4869 * NOTE. Double Dutch. Rendering to plain English: author of comment
4870 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4871 * and expect that both A and B disappear from stream. This is _wrong_.
4872 * Though this happens in BSD with high probability, this is occasional.
4873 * Any application relying on this is buggy. Note also, that fix "works"
4874 * only in this artificial test. Insert some normal data between A and B and we will
4875 * decline of BSD again. Verdict: it is better to remove to trap
4876 * buggy users.
4877 */
4878 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
4879 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
4880 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
4881 tp->copied_seq++;
4882 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
4883 __skb_unlink(skb, &sk->sk_receive_queue);
4884 __kfree_skb(skb);
4885 }
4886 }
4887
4888 tp->urg_data = TCP_URG_NOTYET;
4889 tp->urg_seq = ptr;
4890
4891 /* Disable header prediction. */
4892 tp->pred_flags = 0;
4893}
4894
4895/* This is the 'fast' part of urgent handling. */
4896static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th)
4897{
4898 struct tcp_sock *tp = tcp_sk(sk);
4899
4900 /* Check if we get a new urgent pointer - normally not. */
4901 if (th->urg)
4902 tcp_check_urg(sk, th);
4903
4904 /* Do we wait for any urgent data? - normally not... */
4905 if (tp->urg_data == TCP_URG_NOTYET) {
4906 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
4907 th->syn;
4908
4909 /* Is the urgent pointer pointing into this packet? */
4910 if (ptr < skb->len) {
4911 u8 tmp;
4912 if (skb_copy_bits(skb, ptr, &tmp, 1))
4913 BUG();
4914 tp->urg_data = TCP_URG_VALID | tmp;
4915 if (!sock_flag(sk, SOCK_DEAD))
4916 sk->sk_data_ready(sk);
4917 }
4918 }
4919}
4920
4921static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
4922{
4923 struct tcp_sock *tp = tcp_sk(sk);
4924 int chunk = skb->len - hlen;
4925 int err;
4926
4927 local_bh_enable();
4928 if (skb_csum_unnecessary(skb))
4929 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
4930 else
4931 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
4932 tp->ucopy.iov);
4933
4934 if (!err) {
4935 tp->ucopy.len -= chunk;
4936 tp->copied_seq += chunk;
4937 tcp_rcv_space_adjust(sk);
4938 }
4939
4940 local_bh_disable();
4941 return err;
4942}
4943
4944static __sum16 __tcp_checksum_complete_user(struct sock *sk,
4945 struct sk_buff *skb)
4946{
4947 __sum16 result;
4948
4949 if (sock_owned_by_user(sk)) {
4950 local_bh_enable();
4951 result = __tcp_checksum_complete(skb);
4952 local_bh_disable();
4953 } else {
4954 result = __tcp_checksum_complete(skb);
4955 }
4956 return result;
4957}
4958
4959static inline bool tcp_checksum_complete_user(struct sock *sk,
4960 struct sk_buff *skb)
4961{
4962 return !skb_csum_unnecessary(skb) &&
4963 __tcp_checksum_complete_user(sk, skb);
4964}
4965
4966#ifdef CONFIG_NET_DMA
4967static bool tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb,
4968 int hlen)
4969{
4970 struct tcp_sock *tp = tcp_sk(sk);
4971 int chunk = skb->len - hlen;
4972 int dma_cookie;
4973 bool copied_early = false;
4974
4975 if (tp->ucopy.wakeup)
4976 return false;
4977
4978 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
4979 tp->ucopy.dma_chan = net_dma_find_channel();
4980
4981 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) {
4982
4983 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
4984 skb, hlen,
4985 tp->ucopy.iov, chunk,
4986 tp->ucopy.pinned_list);
4987
4988 if (dma_cookie < 0)
4989 goto out;
4990
4991 tp->ucopy.dma_cookie = dma_cookie;
4992 copied_early = true;
4993
4994 tp->ucopy.len -= chunk;
4995 tp->copied_seq += chunk;
4996 tcp_rcv_space_adjust(sk);
4997
4998 if ((tp->ucopy.len == 0) ||
4999 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) ||
5000 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
5001 tp->ucopy.wakeup = 1;
5002 sk->sk_data_ready(sk);
5003 }
5004 } else if (chunk > 0) {
5005 tp->ucopy.wakeup = 1;
5006 sk->sk_data_ready(sk);
5007 }
5008out:
5009 return copied_early;
5010}
5011#endif /* CONFIG_NET_DMA */
5012
5013/* Does PAWS and seqno based validation of an incoming segment, flags will
5014 * play significant role here.
5015 */
5016static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
5017 const struct tcphdr *th, int syn_inerr)
5018{
5019 struct tcp_sock *tp = tcp_sk(sk);
5020
5021 /* RFC1323: H1. Apply PAWS check first. */
5022 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
5023 tcp_paws_discard(sk, skb)) {
5024 if (!th->rst) {
5025 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
5026 tcp_send_dupack(sk, skb);
5027 goto discard;
5028 }
5029 /* Reset is accepted even if it did not pass PAWS. */
5030 }
5031
5032 /* Step 1: check sequence number */
5033 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
5034 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5035 * (RST) segments are validated by checking their SEQ-fields."
5036 * And page 69: "If an incoming segment is not acceptable,
5037 * an acknowledgment should be sent in reply (unless the RST
5038 * bit is set, if so drop the segment and return)".
5039 */
5040 if (!th->rst) {
5041 if (th->syn)
5042 goto syn_challenge;
5043 tcp_send_dupack(sk, skb);
5044 }
5045 goto discard;
5046 }
5047
5048 /* Step 2: check RST bit */
5049 if (th->rst) {
5050 /* RFC 5961 3.2 :
5051 * If sequence number exactly matches RCV.NXT, then
5052 * RESET the connection
5053 * else
5054 * Send a challenge ACK
5055 */
5056 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt)
5057 tcp_reset(sk);
5058 else
5059 tcp_send_challenge_ack(sk);
5060 goto discard;
5061 }
5062
5063 /* step 3: check security and precedence [ignored] */
5064
5065 /* step 4: Check for a SYN
5066 * RFC 5691 4.2 : Send a challenge ack
5067 */
5068 if (th->syn) {
5069syn_challenge:
5070 if (syn_inerr)
5071 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5072 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);
5073 tcp_send_challenge_ack(sk);
5074 goto discard;
5075 }
5076
5077 return true;
5078
5079discard:
5080 __kfree_skb(skb);
5081 return false;
5082}
5083
5084/*
5085 * TCP receive function for the ESTABLISHED state.
5086 *
5087 * It is split into a fast path and a slow path. The fast path is
5088 * disabled when:
5089 * - A zero window was announced from us - zero window probing
5090 * is only handled properly in the slow path.
5091 * - Out of order segments arrived.
5092 * - Urgent data is expected.
5093 * - There is no buffer space left
5094 * - Unexpected TCP flags/window values/header lengths are received
5095 * (detected by checking the TCP header against pred_flags)
5096 * - Data is sent in both directions. Fast path only supports pure senders
5097 * or pure receivers (this means either the sequence number or the ack
5098 * value must stay constant)
5099 * - Unexpected TCP option.
5100 *
5101 * When these conditions are not satisfied it drops into a standard
5102 * receive procedure patterned after RFC793 to handle all cases.
5103 * The first three cases are guaranteed by proper pred_flags setting,
5104 * the rest is checked inline. Fast processing is turned on in
5105 * tcp_data_queue when everything is OK.
5106 */
5107void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
5108 const struct tcphdr *th, unsigned int len)
5109{
5110 struct tcp_sock *tp = tcp_sk(sk);
5111
5112 if (unlikely(sk->sk_rx_dst == NULL))
5113 inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
5114 /*
5115 * Header prediction.
5116 * The code loosely follows the one in the famous
5117 * "30 instruction TCP receive" Van Jacobson mail.
5118 *
5119 * Van's trick is to deposit buffers into socket queue
5120 * on a device interrupt, to call tcp_recv function
5121 * on the receive process context and checksum and copy
5122 * the buffer to user space. smart...
5123 *
5124 * Our current scheme is not silly either but we take the
5125 * extra cost of the net_bh soft interrupt processing...
5126 * We do checksum and copy also but from device to kernel.
5127 */
5128
5129 tp->rx_opt.saw_tstamp = 0;
5130
5131 /* pred_flags is 0xS?10 << 16 + snd_wnd
5132 * if header_prediction is to be made
5133 * 'S' will always be tp->tcp_header_len >> 2
5134 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5135 * turn it off (when there are holes in the receive
5136 * space for instance)
5137 * PSH flag is ignored.
5138 */
5139
5140 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
5141 TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
5142 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
5143 int tcp_header_len = tp->tcp_header_len;
5144
5145 /* Timestamp header prediction: tcp_header_len
5146 * is automatically equal to th->doff*4 due to pred_flags
5147 * match.
5148 */
5149
5150 /* Check timestamp */
5151 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
5152 /* No? Slow path! */
5153 if (!tcp_parse_aligned_timestamp(tp, th))
5154 goto slow_path;
5155
5156 /* If PAWS failed, check it more carefully in slow path */
5157 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
5158 goto slow_path;
5159
5160 /* DO NOT update ts_recent here, if checksum fails
5161 * and timestamp was corrupted part, it will result
5162 * in a hung connection since we will drop all
5163 * future packets due to the PAWS test.
5164 */
5165 }
5166
5167 if (len <= tcp_header_len) {
5168 /* Bulk data transfer: sender */
5169 if (len == tcp_header_len) {
5170 /* Predicted packet is in window by definition.
5171 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5172 * Hence, check seq<=rcv_wup reduces to:
5173 */
5174 if (tcp_header_len ==
5175 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5176 tp->rcv_nxt == tp->rcv_wup)
5177 tcp_store_ts_recent(tp);
5178
5179 /* We know that such packets are checksummed
5180 * on entry.
5181 */
5182 tcp_ack(sk, skb, 0);
5183 __kfree_skb(skb);
5184 tcp_data_snd_check(sk);
5185 return;
5186 } else { /* Header too small */
5187 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5188 goto discard;
5189 }
5190 } else {
5191 int eaten = 0;
5192 int copied_early = 0;
5193 bool fragstolen = false;
5194
5195 if (tp->copied_seq == tp->rcv_nxt &&
5196 len - tcp_header_len <= tp->ucopy.len) {
5197#ifdef CONFIG_NET_DMA
5198 if (tp->ucopy.task == current &&
5199 sock_owned_by_user(sk) &&
5200 tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
5201 copied_early = 1;
5202 eaten = 1;
5203 }
5204#endif
5205 if (tp->ucopy.task == current &&
5206 sock_owned_by_user(sk) && !copied_early) {
5207 __set_current_state(TASK_RUNNING);
5208
5209 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
5210 eaten = 1;
5211 }
5212 if (eaten) {
5213 /* Predicted packet is in window by definition.
5214 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5215 * Hence, check seq<=rcv_wup reduces to:
5216 */
5217 if (tcp_header_len ==
5218 (sizeof(struct tcphdr) +
5219 TCPOLEN_TSTAMP_ALIGNED) &&
5220 tp->rcv_nxt == tp->rcv_wup)
5221 tcp_store_ts_recent(tp);
5222
5223 tcp_rcv_rtt_measure_ts(sk, skb);
5224
5225 __skb_pull(skb, tcp_header_len);
5226 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
5227 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER);
5228 }
5229 if (copied_early)
5230 tcp_cleanup_rbuf(sk, skb->len);
5231 }
5232 if (!eaten) {
5233 if (tcp_checksum_complete_user(sk, skb))
5234 goto csum_error;
5235
5236 if ((int)skb->truesize > sk->sk_forward_alloc)
5237 goto step5;
5238
5239 /* Predicted packet is in window by definition.
5240 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5241 * Hence, check seq<=rcv_wup reduces to:
5242 */
5243 if (tcp_header_len ==
5244 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5245 tp->rcv_nxt == tp->rcv_wup)
5246 tcp_store_ts_recent(tp);
5247
5248 tcp_rcv_rtt_measure_ts(sk, skb);
5249
5250 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS);
5251
5252 /* Bulk data transfer: receiver */
5253 eaten = tcp_queue_rcv(sk, skb, tcp_header_len,
5254 &fragstolen);
5255 }
5256
5257 tcp_event_data_recv(sk, skb);
5258
5259 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
5260 /* Well, only one small jumplet in fast path... */
5261 tcp_ack(sk, skb, FLAG_DATA);
5262 tcp_data_snd_check(sk);
5263 if (!inet_csk_ack_scheduled(sk))
5264 goto no_ack;
5265 }
5266
5267 if (!copied_early || tp->rcv_nxt != tp->rcv_wup)
5268 __tcp_ack_snd_check(sk, 0);
5269no_ack:
5270#ifdef CONFIG_NET_DMA
5271 if (copied_early)
5272 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
5273 else
5274#endif
5275 if (eaten)
5276 kfree_skb_partial(skb, fragstolen);
5277 sk->sk_data_ready(sk);
5278 return;
5279 }
5280 }
5281
5282slow_path:
5283 if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
5284 goto csum_error;
5285
5286 if (!th->ack && !th->rst)
5287 goto discard;
5288
5289 /*
5290 * Standard slow path.
5291 */
5292
5293 if (!tcp_validate_incoming(sk, skb, th, 1))
5294 return;
5295
5296step5:
5297 if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0)
5298 goto discard;
5299
5300 tcp_rcv_rtt_measure_ts(sk, skb);
5301
5302 /* Process urgent data. */
5303 tcp_urg(sk, skb, th);
5304
5305 /* step 7: process the segment text */
5306 tcp_data_queue(sk, skb);
5307
5308 tcp_data_snd_check(sk);
5309 tcp_ack_snd_check(sk);
5310 return;
5311
5312csum_error:
5313 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_CSUMERRORS);
5314 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5315
5316discard:
5317 __kfree_skb(skb);
5318}
5319EXPORT_SYMBOL(tcp_rcv_established);
5320
5321void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
5322{
5323 struct tcp_sock *tp = tcp_sk(sk);
5324 struct inet_connection_sock *icsk = inet_csk(sk);
5325
5326 tcp_set_state(sk, TCP_ESTABLISHED);
5327
5328 if (skb != NULL) {
5329 icsk->icsk_af_ops->sk_rx_dst_set(sk, skb);
5330 security_inet_conn_established(sk, skb);
5331 }
5332
5333 /* Make sure socket is routed, for correct metrics. */
5334 icsk->icsk_af_ops->rebuild_header(sk);
5335
5336 tcp_init_metrics(sk);
5337
5338 tcp_init_congestion_control(sk);
5339
5340 /* Prevent spurious tcp_cwnd_restart() on first data
5341 * packet.
5342 */
5343 tp->lsndtime = tcp_time_stamp;
5344
5345 tcp_init_buffer_space(sk);
5346
5347 if (sock_flag(sk, SOCK_KEEPOPEN))
5348 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
5349
5350 if (!tp->rx_opt.snd_wscale)
5351 __tcp_fast_path_on(tp, tp->snd_wnd);
5352 else
5353 tp->pred_flags = 0;
5354
5355 if (!sock_flag(sk, SOCK_DEAD)) {
5356 sk->sk_state_change(sk);
5357 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
5358 }
5359}
5360
5361static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
5362 struct tcp_fastopen_cookie *cookie)
5363{
5364 struct tcp_sock *tp = tcp_sk(sk);
5365 struct sk_buff *data = tp->syn_data ? tcp_write_queue_head(sk) : NULL;
5366 u16 mss = tp->rx_opt.mss_clamp;
5367 bool syn_drop;
5368
5369 if (mss == tp->rx_opt.user_mss) {
5370 struct tcp_options_received opt;
5371
5372 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5373 tcp_clear_options(&opt);
5374 opt.user_mss = opt.mss_clamp = 0;
5375 tcp_parse_options(synack, &opt, 0, NULL);
5376 mss = opt.mss_clamp;
5377 }
5378
5379 if (!tp->syn_fastopen) /* Ignore an unsolicited cookie */
5380 cookie->len = -1;
5381
5382 /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably
5383 * the remote receives only the retransmitted (regular) SYNs: either
5384 * the original SYN-data or the corresponding SYN-ACK is lost.
5385 */
5386 syn_drop = (cookie->len <= 0 && data && tp->total_retrans);
5387
5388 tcp_fastopen_cache_set(sk, mss, cookie, syn_drop);
5389
5390 if (data) { /* Retransmit unacked data in SYN */
5391 tcp_for_write_queue_from(data, sk) {
5392 if (data == tcp_send_head(sk) ||
5393 __tcp_retransmit_skb(sk, data))
5394 break;
5395 }
5396 tcp_rearm_rto(sk);
5397 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL);
5398 return true;
5399 }
5400 tp->syn_data_acked = tp->syn_data;
5401 if (tp->syn_data_acked)
5402 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
5403 return false;
5404}
5405
5406static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
5407 const struct tcphdr *th, unsigned int len)
5408{
5409 struct inet_connection_sock *icsk = inet_csk(sk);
5410 struct tcp_sock *tp = tcp_sk(sk);
5411 struct tcp_fastopen_cookie foc = { .len = -1 };
5412 int saved_clamp = tp->rx_opt.mss_clamp;
5413
5414 tcp_parse_options(skb, &tp->rx_opt, 0, &foc);
5415 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
5416 tp->rx_opt.rcv_tsecr -= tp->tsoffset;
5417
5418 if (th->ack) {
5419 /* rfc793:
5420 * "If the state is SYN-SENT then
5421 * first check the ACK bit
5422 * If the ACK bit is set
5423 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5424 * a reset (unless the RST bit is set, if so drop
5425 * the segment and return)"
5426 */
5427 if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
5428 after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt))
5429 goto reset_and_undo;
5430
5431 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
5432 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
5433 tcp_time_stamp)) {
5434 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED);
5435 goto reset_and_undo;
5436 }
5437
5438 /* Now ACK is acceptable.
5439 *
5440 * "If the RST bit is set
5441 * If the ACK was acceptable then signal the user "error:
5442 * connection reset", drop the segment, enter CLOSED state,
5443 * delete TCB, and return."
5444 */
5445
5446 if (th->rst) {
5447 tcp_reset(sk);
5448 goto discard;
5449 }
5450
5451 /* rfc793:
5452 * "fifth, if neither of the SYN or RST bits is set then
5453 * drop the segment and return."
5454 *
5455 * See note below!
5456 * --ANK(990513)
5457 */
5458 if (!th->syn)
5459 goto discard_and_undo;
5460
5461 /* rfc793:
5462 * "If the SYN bit is on ...
5463 * are acceptable then ...
5464 * (our SYN has been ACKed), change the connection
5465 * state to ESTABLISHED..."
5466 */
5467
5468 TCP_ECN_rcv_synack(tp, th);
5469
5470 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5471 tcp_ack(sk, skb, FLAG_SLOWPATH);
5472
5473 /* Ok.. it's good. Set up sequence numbers and
5474 * move to established.
5475 */
5476 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5477 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5478
5479 /* RFC1323: The window in SYN & SYN/ACK segments is
5480 * never scaled.
5481 */
5482 tp->snd_wnd = ntohs(th->window);
5483
5484 if (!tp->rx_opt.wscale_ok) {
5485 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
5486 tp->window_clamp = min(tp->window_clamp, 65535U);
5487 }
5488
5489 if (tp->rx_opt.saw_tstamp) {
5490 tp->rx_opt.tstamp_ok = 1;
5491 tp->tcp_header_len =
5492 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5493 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5494 tcp_store_ts_recent(tp);
5495 } else {
5496 tp->tcp_header_len = sizeof(struct tcphdr);
5497 }
5498
5499 if (tcp_is_sack(tp) && sysctl_tcp_fack)
5500 tcp_enable_fack(tp);
5501
5502 tcp_mtup_init(sk);
5503 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5504 tcp_initialize_rcv_mss(sk);
5505
5506 /* Remember, tcp_poll() does not lock socket!
5507 * Change state from SYN-SENT only after copied_seq
5508 * is initialized. */
5509 tp->copied_seq = tp->rcv_nxt;
5510
5511 smp_mb();
5512
5513 tcp_finish_connect(sk, skb);
5514
5515 if ((tp->syn_fastopen || tp->syn_data) &&
5516 tcp_rcv_fastopen_synack(sk, skb, &foc))
5517 return -1;
5518
5519 if (sk->sk_write_pending ||
5520 icsk->icsk_accept_queue.rskq_defer_accept ||
5521 icsk->icsk_ack.pingpong) {
5522 /* Save one ACK. Data will be ready after
5523 * several ticks, if write_pending is set.
5524 *
5525 * It may be deleted, but with this feature tcpdumps
5526 * look so _wonderfully_ clever, that I was not able
5527 * to stand against the temptation 8) --ANK
5528 */
5529 inet_csk_schedule_ack(sk);
5530 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
5531 tcp_enter_quickack_mode(sk);
5532 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
5533 TCP_DELACK_MAX, TCP_RTO_MAX);
5534
5535discard:
5536 __kfree_skb(skb);
5537 return 0;
5538 } else {
5539 tcp_send_ack(sk);
5540 }
5541 return -1;
5542 }
5543
5544 /* No ACK in the segment */
5545
5546 if (th->rst) {
5547 /* rfc793:
5548 * "If the RST bit is set
5549 *
5550 * Otherwise (no ACK) drop the segment and return."
5551 */
5552
5553 goto discard_and_undo;
5554 }
5555
5556 /* PAWS check. */
5557 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
5558 tcp_paws_reject(&tp->rx_opt, 0))
5559 goto discard_and_undo;
5560
5561 if (th->syn) {
5562 /* We see SYN without ACK. It is attempt of
5563 * simultaneous connect with crossed SYNs.
5564 * Particularly, it can be connect to self.
5565 */
5566 tcp_set_state(sk, TCP_SYN_RECV);
5567
5568 if (tp->rx_opt.saw_tstamp) {
5569 tp->rx_opt.tstamp_ok = 1;
5570 tcp_store_ts_recent(tp);
5571 tp->tcp_header_len =
5572 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5573 } else {
5574 tp->tcp_header_len = sizeof(struct tcphdr);
5575 }
5576
5577 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5578 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5579
5580 /* RFC1323: The window in SYN & SYN/ACK segments is
5581 * never scaled.
5582 */
5583 tp->snd_wnd = ntohs(th->window);
5584 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
5585 tp->max_window = tp->snd_wnd;
5586
5587 TCP_ECN_rcv_syn(tp, th);
5588
5589 tcp_mtup_init(sk);
5590 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5591 tcp_initialize_rcv_mss(sk);
5592
5593 tcp_send_synack(sk);
5594#if 0
5595 /* Note, we could accept data and URG from this segment.
5596 * There are no obstacles to make this (except that we must
5597 * either change tcp_recvmsg() to prevent it from returning data
5598 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5599 *
5600 * However, if we ignore data in ACKless segments sometimes,
5601 * we have no reasons to accept it sometimes.
5602 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5603 * is not flawless. So, discard packet for sanity.
5604 * Uncomment this return to process the data.
5605 */
5606 return -1;
5607#else
5608 goto discard;
5609#endif
5610 }
5611 /* "fifth, if neither of the SYN or RST bits is set then
5612 * drop the segment and return."
5613 */
5614
5615discard_and_undo:
5616 tcp_clear_options(&tp->rx_opt);
5617 tp->rx_opt.mss_clamp = saved_clamp;
5618 goto discard;
5619
5620reset_and_undo:
5621 tcp_clear_options(&tp->rx_opt);
5622 tp->rx_opt.mss_clamp = saved_clamp;
5623 return 1;
5624}
5625
5626/*
5627 * This function implements the receiving procedure of RFC 793 for
5628 * all states except ESTABLISHED and TIME_WAIT.
5629 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5630 * address independent.
5631 */
5632
5633int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
5634 const struct tcphdr *th, unsigned int len)
5635{
5636 struct tcp_sock *tp = tcp_sk(sk);
5637 struct inet_connection_sock *icsk = inet_csk(sk);
5638 struct request_sock *req;
5639 int queued = 0;
5640 bool acceptable;
5641 u32 synack_stamp;
5642
5643 tp->rx_opt.saw_tstamp = 0;
5644
5645 switch (sk->sk_state) {
5646 case TCP_CLOSE:
5647 goto discard;
5648
5649 case TCP_LISTEN:
5650 if (th->ack)
5651 return 1;
5652
5653 if (th->rst)
5654 goto discard;
5655
5656 if (th->syn) {
5657 if (th->fin)
5658 goto discard;
5659 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
5660 return 1;
5661
5662 /* Now we have several options: In theory there is
5663 * nothing else in the frame. KA9Q has an option to
5664 * send data with the syn, BSD accepts data with the
5665 * syn up to the [to be] advertised window and
5666 * Solaris 2.1 gives you a protocol error. For now
5667 * we just ignore it, that fits the spec precisely
5668 * and avoids incompatibilities. It would be nice in
5669 * future to drop through and process the data.
5670 *
5671 * Now that TTCP is starting to be used we ought to
5672 * queue this data.
5673 * But, this leaves one open to an easy denial of
5674 * service attack, and SYN cookies can't defend
5675 * against this problem. So, we drop the data
5676 * in the interest of security over speed unless
5677 * it's still in use.
5678 */
5679 kfree_skb(skb);
5680 return 0;
5681 }
5682 goto discard;
5683
5684 case TCP_SYN_SENT:
5685 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
5686 if (queued >= 0)
5687 return queued;
5688
5689 /* Do step6 onward by hand. */
5690 tcp_urg(sk, skb, th);
5691 __kfree_skb(skb);
5692 tcp_data_snd_check(sk);
5693 return 0;
5694 }
5695
5696 req = tp->fastopen_rsk;
5697 if (req != NULL) {
5698 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
5699 sk->sk_state != TCP_FIN_WAIT1);
5700
5701 if (tcp_check_req(sk, skb, req, NULL, true) == NULL)
5702 goto discard;
5703 }
5704
5705 if (!th->ack && !th->rst)
5706 goto discard;
5707
5708 if (!tcp_validate_incoming(sk, skb, th, 0))
5709 return 0;
5710
5711 /* step 5: check the ACK field */
5712 acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
5713 FLAG_UPDATE_TS_RECENT) > 0;
5714
5715 switch (sk->sk_state) {
5716 case TCP_SYN_RECV:
5717 if (!acceptable)
5718 return 1;
5719
5720 /* Once we leave TCP_SYN_RECV, we no longer need req
5721 * so release it.
5722 */
5723 if (req) {
5724 synack_stamp = tcp_rsk(req)->snt_synack;
5725 tp->total_retrans = req->num_retrans;
5726 reqsk_fastopen_remove(sk, req, false);
5727 } else {
5728 synack_stamp = tp->lsndtime;
5729 /* Make sure socket is routed, for correct metrics. */
5730 icsk->icsk_af_ops->rebuild_header(sk);
5731 tcp_init_congestion_control(sk);
5732
5733 tcp_mtup_init(sk);
5734 tp->copied_seq = tp->rcv_nxt;
5735 tcp_init_buffer_space(sk);
5736 }
5737 smp_mb();
5738 tcp_set_state(sk, TCP_ESTABLISHED);
5739 sk->sk_state_change(sk);
5740
5741 /* Note, that this wakeup is only for marginal crossed SYN case.
5742 * Passively open sockets are not waked up, because
5743 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5744 */
5745 if (sk->sk_socket)
5746 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
5747
5748 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
5749 tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
5750 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5751 tcp_synack_rtt_meas(sk, synack_stamp);
5752
5753 if (tp->rx_opt.tstamp_ok)
5754 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5755
5756 if (req) {
5757 /* Re-arm the timer because data may have been sent out.
5758 * This is similar to the regular data transmission case
5759 * when new data has just been ack'ed.
5760 *
5761 * (TFO) - we could try to be more aggressive and
5762 * retransmitting any data sooner based on when they
5763 * are sent out.
5764 */
5765 tcp_rearm_rto(sk);
5766 } else
5767 tcp_init_metrics(sk);
5768
5769 tcp_update_pacing_rate(sk);
5770
5771 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5772 tp->lsndtime = tcp_time_stamp;
5773
5774 tcp_initialize_rcv_mss(sk);
5775 tcp_fast_path_on(tp);
5776 break;
5777
5778 case TCP_FIN_WAIT1: {
5779 struct dst_entry *dst;
5780 int tmo;
5781
5782 /* If we enter the TCP_FIN_WAIT1 state and we are a
5783 * Fast Open socket and this is the first acceptable
5784 * ACK we have received, this would have acknowledged
5785 * our SYNACK so stop the SYNACK timer.
5786 */
5787 if (req != NULL) {
5788 /* Return RST if ack_seq is invalid.
5789 * Note that RFC793 only says to generate a
5790 * DUPACK for it but for TCP Fast Open it seems
5791 * better to treat this case like TCP_SYN_RECV
5792 * above.
5793 */
5794 if (!acceptable)
5795 return 1;
5796 /* We no longer need the request sock. */
5797 reqsk_fastopen_remove(sk, req, false);
5798 tcp_rearm_rto(sk);
5799 }
5800 if (tp->snd_una != tp->write_seq)
5801 break;
5802
5803 tcp_set_state(sk, TCP_FIN_WAIT2);
5804 sk->sk_shutdown |= SEND_SHUTDOWN;
5805
5806 dst = __sk_dst_get(sk);
5807 if (dst)
5808 dst_confirm(dst);
5809
5810 if (!sock_flag(sk, SOCK_DEAD)) {
5811 /* Wake up lingering close() */
5812 sk->sk_state_change(sk);
5813 break;
5814 }
5815
5816 if (tp->linger2 < 0 ||
5817 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5818 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
5819 tcp_done(sk);
5820 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
5821 return 1;
5822 }
5823
5824 tmo = tcp_fin_time(sk);
5825 if (tmo > TCP_TIMEWAIT_LEN) {
5826 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
5827 } else if (th->fin || sock_owned_by_user(sk)) {
5828 /* Bad case. We could lose such FIN otherwise.
5829 * It is not a big problem, but it looks confusing
5830 * and not so rare event. We still can lose it now,
5831 * if it spins in bh_lock_sock(), but it is really
5832 * marginal case.
5833 */
5834 inet_csk_reset_keepalive_timer(sk, tmo);
5835 } else {
5836 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
5837 goto discard;
5838 }
5839 break;
5840 }
5841
5842 case TCP_CLOSING:
5843 if (tp->snd_una == tp->write_seq) {
5844 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
5845 goto discard;
5846 }
5847 break;
5848
5849 case TCP_LAST_ACK:
5850 if (tp->snd_una == tp->write_seq) {
5851 tcp_update_metrics(sk);
5852 tcp_done(sk);
5853 goto discard;
5854 }
5855 break;
5856 }
5857
5858 /* step 6: check the URG bit */
5859 tcp_urg(sk, skb, th);
5860
5861 /* step 7: process the segment text */
5862 switch (sk->sk_state) {
5863 case TCP_CLOSE_WAIT:
5864 case TCP_CLOSING:
5865 case TCP_LAST_ACK:
5866 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
5867 break;
5868 case TCP_FIN_WAIT1:
5869 case TCP_FIN_WAIT2:
5870 /* RFC 793 says to queue data in these states,
5871 * RFC 1122 says we MUST send a reset.
5872 * BSD 4.4 also does reset.
5873 */
5874 if (sk->sk_shutdown & RCV_SHUTDOWN) {
5875 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5876 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
5877 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
5878 tcp_reset(sk);
5879 return 1;
5880 }
5881 }
5882 /* Fall through */
5883 case TCP_ESTABLISHED:
5884 tcp_data_queue(sk, skb);
5885 queued = 1;
5886 break;
5887 }
5888
5889 /* tcp_data could move socket to TIME-WAIT */
5890 if (sk->sk_state != TCP_CLOSE) {
5891 tcp_data_snd_check(sk);
5892 tcp_ack_snd_check(sk);
5893 }
5894
5895 if (!queued) {
5896discard:
5897 __kfree_skb(skb);
5898 }
5899 return 0;
5900}
5901EXPORT_SYMBOL(tcp_rcv_state_process);