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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
83int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
84
85#define FLAG_DATA 0x01 /* Incoming frame contained data. */
86#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
87#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
88#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
89#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
90#define FLAG_DATA_SACKED 0x20 /* New SACK. */
91#define FLAG_ECE 0x40 /* ECE in this ACK */
92#define FLAG_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
93#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
94#define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
95#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
96#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
97#define FLAG_SET_XMIT_TIMER 0x1000 /* Set TLP or RTO timer */
98#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
99#define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
100#define FLAG_NO_CHALLENGE_ACK 0x8000 /* do not call tcp_send_challenge_ack() */
101#define FLAG_ACK_MAYBE_DELAYED 0x10000 /* Likely a delayed ACK */
102
103#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
104#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
105#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE|FLAG_DSACKING_ACK)
106#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
107
108#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
109#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
110
111#define REXMIT_NONE 0 /* no loss recovery to do */
112#define REXMIT_LOST 1 /* retransmit packets marked lost */
113#define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */
114
115#if IS_ENABLED(CONFIG_TLS_DEVICE)
116static DEFINE_STATIC_KEY_DEFERRED_FALSE(clean_acked_data_enabled, HZ);
117
118void clean_acked_data_enable(struct inet_connection_sock *icsk,
119 void (*cad)(struct sock *sk, u32 ack_seq))
120{
121 icsk->icsk_clean_acked = cad;
122 static_branch_deferred_inc(&clean_acked_data_enabled);
123}
124EXPORT_SYMBOL_GPL(clean_acked_data_enable);
125
126void clean_acked_data_disable(struct inet_connection_sock *icsk)
127{
128 static_branch_slow_dec_deferred(&clean_acked_data_enabled);
129 icsk->icsk_clean_acked = NULL;
130}
131EXPORT_SYMBOL_GPL(clean_acked_data_disable);
132
133void clean_acked_data_flush(void)
134{
135 static_key_deferred_flush(&clean_acked_data_enabled);
136}
137EXPORT_SYMBOL_GPL(clean_acked_data_flush);
138#endif
139
140static void tcp_gro_dev_warn(struct sock *sk, const struct sk_buff *skb,
141 unsigned int len)
142{
143 static bool __once __read_mostly;
144
145 if (!__once) {
146 struct net_device *dev;
147
148 __once = true;
149
150 rcu_read_lock();
151 dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif);
152 if (!dev || len >= dev->mtu)
153 pr_warn("%s: Driver has suspect GRO implementation, TCP performance may be compromised.\n",
154 dev ? dev->name : "Unknown driver");
155 rcu_read_unlock();
156 }
157}
158
159/* Adapt the MSS value used to make delayed ack decision to the
160 * real world.
161 */
162static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
163{
164 struct inet_connection_sock *icsk = inet_csk(sk);
165 const unsigned int lss = icsk->icsk_ack.last_seg_size;
166 unsigned int len;
167
168 icsk->icsk_ack.last_seg_size = 0;
169
170 /* skb->len may jitter because of SACKs, even if peer
171 * sends good full-sized frames.
172 */
173 len = skb_shinfo(skb)->gso_size ? : skb->len;
174 if (len >= icsk->icsk_ack.rcv_mss) {
175 icsk->icsk_ack.rcv_mss = min_t(unsigned int, len,
176 tcp_sk(sk)->advmss);
177 /* Account for possibly-removed options */
178 if (unlikely(len > icsk->icsk_ack.rcv_mss +
179 MAX_TCP_OPTION_SPACE))
180 tcp_gro_dev_warn(sk, skb, len);
181 } else {
182 /* Otherwise, we make more careful check taking into account,
183 * that SACKs block is variable.
184 *
185 * "len" is invariant segment length, including TCP header.
186 */
187 len += skb->data - skb_transport_header(skb);
188 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) ||
189 /* If PSH is not set, packet should be
190 * full sized, provided peer TCP is not badly broken.
191 * This observation (if it is correct 8)) allows
192 * to handle super-low mtu links fairly.
193 */
194 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
195 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
196 /* Subtract also invariant (if peer is RFC compliant),
197 * tcp header plus fixed timestamp option length.
198 * Resulting "len" is MSS free of SACK jitter.
199 */
200 len -= tcp_sk(sk)->tcp_header_len;
201 icsk->icsk_ack.last_seg_size = len;
202 if (len == lss) {
203 icsk->icsk_ack.rcv_mss = len;
204 return;
205 }
206 }
207 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
208 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
209 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
210 }
211}
212
213static void tcp_incr_quickack(struct sock *sk, unsigned int max_quickacks)
214{
215 struct inet_connection_sock *icsk = inet_csk(sk);
216 unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
217
218 if (quickacks == 0)
219 quickacks = 2;
220 quickacks = min(quickacks, max_quickacks);
221 if (quickacks > icsk->icsk_ack.quick)
222 icsk->icsk_ack.quick = quickacks;
223}
224
225void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks)
226{
227 struct inet_connection_sock *icsk = inet_csk(sk);
228
229 tcp_incr_quickack(sk, max_quickacks);
230 inet_csk_exit_pingpong_mode(sk);
231 icsk->icsk_ack.ato = TCP_ATO_MIN;
232}
233EXPORT_SYMBOL(tcp_enter_quickack_mode);
234
235/* Send ACKs quickly, if "quick" count is not exhausted
236 * and the session is not interactive.
237 */
238
239static bool tcp_in_quickack_mode(struct sock *sk)
240{
241 const struct inet_connection_sock *icsk = inet_csk(sk);
242 const struct dst_entry *dst = __sk_dst_get(sk);
243
244 return (dst && dst_metric(dst, RTAX_QUICKACK)) ||
245 (icsk->icsk_ack.quick && !inet_csk_in_pingpong_mode(sk));
246}
247
248static void tcp_ecn_queue_cwr(struct tcp_sock *tp)
249{
250 if (tp->ecn_flags & TCP_ECN_OK)
251 tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
252}
253
254static void tcp_ecn_accept_cwr(struct sock *sk, const struct sk_buff *skb)
255{
256 if (tcp_hdr(skb)->cwr) {
257 tcp_sk(sk)->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
258
259 /* If the sender is telling us it has entered CWR, then its
260 * cwnd may be very low (even just 1 packet), so we should ACK
261 * immediately.
262 */
263 inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
264 }
265}
266
267static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp)
268{
269 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
270}
271
272static void __tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb)
273{
274 struct tcp_sock *tp = tcp_sk(sk);
275
276 switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) {
277 case INET_ECN_NOT_ECT:
278 /* Funny extension: if ECT is not set on a segment,
279 * and we already seen ECT on a previous segment,
280 * it is probably a retransmit.
281 */
282 if (tp->ecn_flags & TCP_ECN_SEEN)
283 tcp_enter_quickack_mode(sk, 2);
284 break;
285 case INET_ECN_CE:
286 if (tcp_ca_needs_ecn(sk))
287 tcp_ca_event(sk, CA_EVENT_ECN_IS_CE);
288
289 if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) {
290 /* Better not delay acks, sender can have a very low cwnd */
291 tcp_enter_quickack_mode(sk, 2);
292 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
293 }
294 tp->ecn_flags |= TCP_ECN_SEEN;
295 break;
296 default:
297 if (tcp_ca_needs_ecn(sk))
298 tcp_ca_event(sk, CA_EVENT_ECN_NO_CE);
299 tp->ecn_flags |= TCP_ECN_SEEN;
300 break;
301 }
302}
303
304static void tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb)
305{
306 if (tcp_sk(sk)->ecn_flags & TCP_ECN_OK)
307 __tcp_ecn_check_ce(sk, skb);
308}
309
310static void tcp_ecn_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th)
311{
312 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
313 tp->ecn_flags &= ~TCP_ECN_OK;
314}
315
316static void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th)
317{
318 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
319 tp->ecn_flags &= ~TCP_ECN_OK;
320}
321
322static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th)
323{
324 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
325 return true;
326 return false;
327}
328
329/* Buffer size and advertised window tuning.
330 *
331 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
332 */
333
334static void tcp_sndbuf_expand(struct sock *sk)
335{
336 const struct tcp_sock *tp = tcp_sk(sk);
337 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
338 int sndmem, per_mss;
339 u32 nr_segs;
340
341 /* Worst case is non GSO/TSO : each frame consumes one skb
342 * and skb->head is kmalloced using power of two area of memory
343 */
344 per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
345 MAX_TCP_HEADER +
346 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
347
348 per_mss = roundup_pow_of_two(per_mss) +
349 SKB_DATA_ALIGN(sizeof(struct sk_buff));
350
351 nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd);
352 nr_segs = max_t(u32, nr_segs, tp->reordering + 1);
353
354 /* Fast Recovery (RFC 5681 3.2) :
355 * Cubic needs 1.7 factor, rounded to 2 to include
356 * extra cushion (application might react slowly to EPOLLOUT)
357 */
358 sndmem = ca_ops->sndbuf_expand ? ca_ops->sndbuf_expand(sk) : 2;
359 sndmem *= nr_segs * per_mss;
360
361 if (sk->sk_sndbuf < sndmem)
362 WRITE_ONCE(sk->sk_sndbuf,
363 min(sndmem, sock_net(sk)->ipv4.sysctl_tcp_wmem[2]));
364}
365
366/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
367 *
368 * All tcp_full_space() is split to two parts: "network" buffer, allocated
369 * forward and advertised in receiver window (tp->rcv_wnd) and
370 * "application buffer", required to isolate scheduling/application
371 * latencies from network.
372 * window_clamp is maximal advertised window. It can be less than
373 * tcp_full_space(), in this case tcp_full_space() - window_clamp
374 * is reserved for "application" buffer. The less window_clamp is
375 * the smoother our behaviour from viewpoint of network, but the lower
376 * throughput and the higher sensitivity of the connection to losses. 8)
377 *
378 * rcv_ssthresh is more strict window_clamp used at "slow start"
379 * phase to predict further behaviour of this connection.
380 * It is used for two goals:
381 * - to enforce header prediction at sender, even when application
382 * requires some significant "application buffer". It is check #1.
383 * - to prevent pruning of receive queue because of misprediction
384 * of receiver window. Check #2.
385 *
386 * The scheme does not work when sender sends good segments opening
387 * window and then starts to feed us spaghetti. But it should work
388 * in common situations. Otherwise, we have to rely on queue collapsing.
389 */
390
391/* Slow part of check#2. */
392static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
393{
394 struct tcp_sock *tp = tcp_sk(sk);
395 /* Optimize this! */
396 int truesize = tcp_win_from_space(sk, skb->truesize) >> 1;
397 int window = tcp_win_from_space(sk, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]) >> 1;
398
399 while (tp->rcv_ssthresh <= window) {
400 if (truesize <= skb->len)
401 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
402
403 truesize >>= 1;
404 window >>= 1;
405 }
406 return 0;
407}
408
409static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
410{
411 struct tcp_sock *tp = tcp_sk(sk);
412 int room;
413
414 room = min_t(int, tp->window_clamp, tcp_space(sk)) - tp->rcv_ssthresh;
415
416 /* Check #1 */
417 if (room > 0 && !tcp_under_memory_pressure(sk)) {
418 int incr;
419
420 /* Check #2. Increase window, if skb with such overhead
421 * will fit to rcvbuf in future.
422 */
423 if (tcp_win_from_space(sk, skb->truesize) <= skb->len)
424 incr = 2 * tp->advmss;
425 else
426 incr = __tcp_grow_window(sk, skb);
427
428 if (incr) {
429 incr = max_t(int, incr, 2 * skb->len);
430 tp->rcv_ssthresh += min(room, incr);
431 inet_csk(sk)->icsk_ack.quick |= 1;
432 }
433 }
434}
435
436/* 3. Try to fixup all. It is made immediately after connection enters
437 * established state.
438 */
439void tcp_init_buffer_space(struct sock *sk)
440{
441 int tcp_app_win = sock_net(sk)->ipv4.sysctl_tcp_app_win;
442 struct tcp_sock *tp = tcp_sk(sk);
443 int maxwin;
444
445 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
446 tcp_sndbuf_expand(sk);
447
448 tp->rcvq_space.space = min_t(u32, tp->rcv_wnd, TCP_INIT_CWND * tp->advmss);
449 tcp_mstamp_refresh(tp);
450 tp->rcvq_space.time = tp->tcp_mstamp;
451 tp->rcvq_space.seq = tp->copied_seq;
452
453 maxwin = tcp_full_space(sk);
454
455 if (tp->window_clamp >= maxwin) {
456 tp->window_clamp = maxwin;
457
458 if (tcp_app_win && maxwin > 4 * tp->advmss)
459 tp->window_clamp = max(maxwin -
460 (maxwin >> tcp_app_win),
461 4 * tp->advmss);
462 }
463
464 /* Force reservation of one segment. */
465 if (tcp_app_win &&
466 tp->window_clamp > 2 * tp->advmss &&
467 tp->window_clamp + tp->advmss > maxwin)
468 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
469
470 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
471 tp->snd_cwnd_stamp = tcp_jiffies32;
472}
473
474/* 4. Recalculate window clamp after socket hit its memory bounds. */
475static void tcp_clamp_window(struct sock *sk)
476{
477 struct tcp_sock *tp = tcp_sk(sk);
478 struct inet_connection_sock *icsk = inet_csk(sk);
479 struct net *net = sock_net(sk);
480
481 icsk->icsk_ack.quick = 0;
482
483 if (sk->sk_rcvbuf < net->ipv4.sysctl_tcp_rmem[2] &&
484 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
485 !tcp_under_memory_pressure(sk) &&
486 sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) {
487 WRITE_ONCE(sk->sk_rcvbuf,
488 min(atomic_read(&sk->sk_rmem_alloc),
489 net->ipv4.sysctl_tcp_rmem[2]));
490 }
491 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
492 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
493}
494
495/* Initialize RCV_MSS value.
496 * RCV_MSS is an our guess about MSS used by the peer.
497 * We haven't any direct information about the MSS.
498 * It's better to underestimate the RCV_MSS rather than overestimate.
499 * Overestimations make us ACKing less frequently than needed.
500 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
501 */
502void tcp_initialize_rcv_mss(struct sock *sk)
503{
504 const struct tcp_sock *tp = tcp_sk(sk);
505 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
506
507 hint = min(hint, tp->rcv_wnd / 2);
508 hint = min(hint, TCP_MSS_DEFAULT);
509 hint = max(hint, TCP_MIN_MSS);
510
511 inet_csk(sk)->icsk_ack.rcv_mss = hint;
512}
513EXPORT_SYMBOL(tcp_initialize_rcv_mss);
514
515/* Receiver "autotuning" code.
516 *
517 * The algorithm for RTT estimation w/o timestamps is based on
518 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
519 * <http://public.lanl.gov/radiant/pubs.html#DRS>
520 *
521 * More detail on this code can be found at
522 * <http://staff.psc.edu/jheffner/>,
523 * though this reference is out of date. A new paper
524 * is pending.
525 */
526static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
527{
528 u32 new_sample = tp->rcv_rtt_est.rtt_us;
529 long m = sample;
530
531 if (new_sample != 0) {
532 /* If we sample in larger samples in the non-timestamp
533 * case, we could grossly overestimate the RTT especially
534 * with chatty applications or bulk transfer apps which
535 * are stalled on filesystem I/O.
536 *
537 * Also, since we are only going for a minimum in the
538 * non-timestamp case, we do not smooth things out
539 * else with timestamps disabled convergence takes too
540 * long.
541 */
542 if (!win_dep) {
543 m -= (new_sample >> 3);
544 new_sample += m;
545 } else {
546 m <<= 3;
547 if (m < new_sample)
548 new_sample = m;
549 }
550 } else {
551 /* No previous measure. */
552 new_sample = m << 3;
553 }
554
555 tp->rcv_rtt_est.rtt_us = new_sample;
556}
557
558static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
559{
560 u32 delta_us;
561
562 if (tp->rcv_rtt_est.time == 0)
563 goto new_measure;
564 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
565 return;
566 delta_us = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcv_rtt_est.time);
567 if (!delta_us)
568 delta_us = 1;
569 tcp_rcv_rtt_update(tp, delta_us, 1);
570
571new_measure:
572 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
573 tp->rcv_rtt_est.time = tp->tcp_mstamp;
574}
575
576static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
577 const struct sk_buff *skb)
578{
579 struct tcp_sock *tp = tcp_sk(sk);
580
581 if (tp->rx_opt.rcv_tsecr == tp->rcv_rtt_last_tsecr)
582 return;
583 tp->rcv_rtt_last_tsecr = tp->rx_opt.rcv_tsecr;
584
585 if (TCP_SKB_CB(skb)->end_seq -
586 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss) {
587 u32 delta = tcp_time_stamp(tp) - tp->rx_opt.rcv_tsecr;
588 u32 delta_us;
589
590 if (likely(delta < INT_MAX / (USEC_PER_SEC / TCP_TS_HZ))) {
591 if (!delta)
592 delta = 1;
593 delta_us = delta * (USEC_PER_SEC / TCP_TS_HZ);
594 tcp_rcv_rtt_update(tp, delta_us, 0);
595 }
596 }
597}
598
599/*
600 * This function should be called every time data is copied to user space.
601 * It calculates the appropriate TCP receive buffer space.
602 */
603void tcp_rcv_space_adjust(struct sock *sk)
604{
605 struct tcp_sock *tp = tcp_sk(sk);
606 u32 copied;
607 int time;
608
609 trace_tcp_rcv_space_adjust(sk);
610
611 tcp_mstamp_refresh(tp);
612 time = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcvq_space.time);
613 if (time < (tp->rcv_rtt_est.rtt_us >> 3) || tp->rcv_rtt_est.rtt_us == 0)
614 return;
615
616 /* Number of bytes copied to user in last RTT */
617 copied = tp->copied_seq - tp->rcvq_space.seq;
618 if (copied <= tp->rcvq_space.space)
619 goto new_measure;
620
621 /* A bit of theory :
622 * copied = bytes received in previous RTT, our base window
623 * To cope with packet losses, we need a 2x factor
624 * To cope with slow start, and sender growing its cwin by 100 %
625 * every RTT, we need a 4x factor, because the ACK we are sending
626 * now is for the next RTT, not the current one :
627 * <prev RTT . ><current RTT .. ><next RTT .... >
628 */
629
630 if (sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf &&
631 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
632 int rcvmem, rcvbuf;
633 u64 rcvwin, grow;
634
635 /* minimal window to cope with packet losses, assuming
636 * steady state. Add some cushion because of small variations.
637 */
638 rcvwin = ((u64)copied << 1) + 16 * tp->advmss;
639
640 /* Accommodate for sender rate increase (eg. slow start) */
641 grow = rcvwin * (copied - tp->rcvq_space.space);
642 do_div(grow, tp->rcvq_space.space);
643 rcvwin += (grow << 1);
644
645 rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER);
646 while (tcp_win_from_space(sk, rcvmem) < tp->advmss)
647 rcvmem += 128;
648
649 do_div(rcvwin, tp->advmss);
650 rcvbuf = min_t(u64, rcvwin * rcvmem,
651 sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
652 if (rcvbuf > sk->sk_rcvbuf) {
653 WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);
654
655 /* Make the window clamp follow along. */
656 tp->window_clamp = tcp_win_from_space(sk, rcvbuf);
657 }
658 }
659 tp->rcvq_space.space = copied;
660
661new_measure:
662 tp->rcvq_space.seq = tp->copied_seq;
663 tp->rcvq_space.time = tp->tcp_mstamp;
664}
665
666/* There is something which you must keep in mind when you analyze the
667 * behavior of the tp->ato delayed ack timeout interval. When a
668 * connection starts up, we want to ack as quickly as possible. The
669 * problem is that "good" TCP's do slow start at the beginning of data
670 * transmission. The means that until we send the first few ACK's the
671 * sender will sit on his end and only queue most of his data, because
672 * he can only send snd_cwnd unacked packets at any given time. For
673 * each ACK we send, he increments snd_cwnd and transmits more of his
674 * queue. -DaveM
675 */
676static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
677{
678 struct tcp_sock *tp = tcp_sk(sk);
679 struct inet_connection_sock *icsk = inet_csk(sk);
680 u32 now;
681
682 inet_csk_schedule_ack(sk);
683
684 tcp_measure_rcv_mss(sk, skb);
685
686 tcp_rcv_rtt_measure(tp);
687
688 now = tcp_jiffies32;
689
690 if (!icsk->icsk_ack.ato) {
691 /* The _first_ data packet received, initialize
692 * delayed ACK engine.
693 */
694 tcp_incr_quickack(sk, TCP_MAX_QUICKACKS);
695 icsk->icsk_ack.ato = TCP_ATO_MIN;
696 } else {
697 int m = now - icsk->icsk_ack.lrcvtime;
698
699 if (m <= TCP_ATO_MIN / 2) {
700 /* The fastest case is the first. */
701 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
702 } else if (m < icsk->icsk_ack.ato) {
703 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
704 if (icsk->icsk_ack.ato > icsk->icsk_rto)
705 icsk->icsk_ack.ato = icsk->icsk_rto;
706 } else if (m > icsk->icsk_rto) {
707 /* Too long gap. Apparently sender failed to
708 * restart window, so that we send ACKs quickly.
709 */
710 tcp_incr_quickack(sk, TCP_MAX_QUICKACKS);
711 sk_mem_reclaim(sk);
712 }
713 }
714 icsk->icsk_ack.lrcvtime = now;
715
716 tcp_ecn_check_ce(sk, skb);
717
718 if (skb->len >= 128)
719 tcp_grow_window(sk, skb);
720}
721
722/* Called to compute a smoothed rtt estimate. The data fed to this
723 * routine either comes from timestamps, or from segments that were
724 * known _not_ to have been retransmitted [see Karn/Partridge
725 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
726 * piece by Van Jacobson.
727 * NOTE: the next three routines used to be one big routine.
728 * To save cycles in the RFC 1323 implementation it was better to break
729 * it up into three procedures. -- erics
730 */
731static void tcp_rtt_estimator(struct sock *sk, long mrtt_us)
732{
733 struct tcp_sock *tp = tcp_sk(sk);
734 long m = mrtt_us; /* RTT */
735 u32 srtt = tp->srtt_us;
736
737 /* The following amusing code comes from Jacobson's
738 * article in SIGCOMM '88. Note that rtt and mdev
739 * are scaled versions of rtt and mean deviation.
740 * This is designed to be as fast as possible
741 * m stands for "measurement".
742 *
743 * On a 1990 paper the rto value is changed to:
744 * RTO = rtt + 4 * mdev
745 *
746 * Funny. This algorithm seems to be very broken.
747 * These formulae increase RTO, when it should be decreased, increase
748 * too slowly, when it should be increased quickly, decrease too quickly
749 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
750 * does not matter how to _calculate_ it. Seems, it was trap
751 * that VJ failed to avoid. 8)
752 */
753 if (srtt != 0) {
754 m -= (srtt >> 3); /* m is now error in rtt est */
755 srtt += m; /* rtt = 7/8 rtt + 1/8 new */
756 if (m < 0) {
757 m = -m; /* m is now abs(error) */
758 m -= (tp->mdev_us >> 2); /* similar update on mdev */
759 /* This is similar to one of Eifel findings.
760 * Eifel blocks mdev updates when rtt decreases.
761 * This solution is a bit different: we use finer gain
762 * for mdev in this case (alpha*beta).
763 * Like Eifel it also prevents growth of rto,
764 * but also it limits too fast rto decreases,
765 * happening in pure Eifel.
766 */
767 if (m > 0)
768 m >>= 3;
769 } else {
770 m -= (tp->mdev_us >> 2); /* similar update on mdev */
771 }
772 tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */
773 if (tp->mdev_us > tp->mdev_max_us) {
774 tp->mdev_max_us = tp->mdev_us;
775 if (tp->mdev_max_us > tp->rttvar_us)
776 tp->rttvar_us = tp->mdev_max_us;
777 }
778 if (after(tp->snd_una, tp->rtt_seq)) {
779 if (tp->mdev_max_us < tp->rttvar_us)
780 tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2;
781 tp->rtt_seq = tp->snd_nxt;
782 tp->mdev_max_us = tcp_rto_min_us(sk);
783
784 tcp_bpf_rtt(sk);
785 }
786 } else {
787 /* no previous measure. */
788 srtt = m << 3; /* take the measured time to be rtt */
789 tp->mdev_us = m << 1; /* make sure rto = 3*rtt */
790 tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk));
791 tp->mdev_max_us = tp->rttvar_us;
792 tp->rtt_seq = tp->snd_nxt;
793
794 tcp_bpf_rtt(sk);
795 }
796 tp->srtt_us = max(1U, srtt);
797}
798
799static void tcp_update_pacing_rate(struct sock *sk)
800{
801 const struct tcp_sock *tp = tcp_sk(sk);
802 u64 rate;
803
804 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
805 rate = (u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3);
806
807 /* current rate is (cwnd * mss) / srtt
808 * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
809 * In Congestion Avoidance phase, set it to 120 % the current rate.
810 *
811 * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
812 * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
813 * end of slow start and should slow down.
814 */
815 if (tp->snd_cwnd < tp->snd_ssthresh / 2)
816 rate *= sock_net(sk)->ipv4.sysctl_tcp_pacing_ss_ratio;
817 else
818 rate *= sock_net(sk)->ipv4.sysctl_tcp_pacing_ca_ratio;
819
820 rate *= max(tp->snd_cwnd, tp->packets_out);
821
822 if (likely(tp->srtt_us))
823 do_div(rate, tp->srtt_us);
824
825 /* WRITE_ONCE() is needed because sch_fq fetches sk_pacing_rate
826 * without any lock. We want to make sure compiler wont store
827 * intermediate values in this location.
828 */
829 WRITE_ONCE(sk->sk_pacing_rate, min_t(u64, rate,
830 sk->sk_max_pacing_rate));
831}
832
833/* Calculate rto without backoff. This is the second half of Van Jacobson's
834 * routine referred to above.
835 */
836static void tcp_set_rto(struct sock *sk)
837{
838 const struct tcp_sock *tp = tcp_sk(sk);
839 /* Old crap is replaced with new one. 8)
840 *
841 * More seriously:
842 * 1. If rtt variance happened to be less 50msec, it is hallucination.
843 * It cannot be less due to utterly erratic ACK generation made
844 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
845 * to do with delayed acks, because at cwnd>2 true delack timeout
846 * is invisible. Actually, Linux-2.4 also generates erratic
847 * ACKs in some circumstances.
848 */
849 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp);
850
851 /* 2. Fixups made earlier cannot be right.
852 * If we do not estimate RTO correctly without them,
853 * all the algo is pure shit and should be replaced
854 * with correct one. It is exactly, which we pretend to do.
855 */
856
857 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
858 * guarantees that rto is higher.
859 */
860 tcp_bound_rto(sk);
861}
862
863__u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst)
864{
865 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
866
867 if (!cwnd)
868 cwnd = TCP_INIT_CWND;
869 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
870}
871
872/* Take a notice that peer is sending D-SACKs */
873static void tcp_dsack_seen(struct tcp_sock *tp)
874{
875 tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
876 tp->rack.dsack_seen = 1;
877 tp->dsack_dups++;
878}
879
880/* It's reordering when higher sequence was delivered (i.e. sacked) before
881 * some lower never-retransmitted sequence ("low_seq"). The maximum reordering
882 * distance is approximated in full-mss packet distance ("reordering").
883 */
884static void tcp_check_sack_reordering(struct sock *sk, const u32 low_seq,
885 const int ts)
886{
887 struct tcp_sock *tp = tcp_sk(sk);
888 const u32 mss = tp->mss_cache;
889 u32 fack, metric;
890
891 fack = tcp_highest_sack_seq(tp);
892 if (!before(low_seq, fack))
893 return;
894
895 metric = fack - low_seq;
896 if ((metric > tp->reordering * mss) && mss) {
897#if FASTRETRANS_DEBUG > 1
898 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
899 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
900 tp->reordering,
901 0,
902 tp->sacked_out,
903 tp->undo_marker ? tp->undo_retrans : 0);
904#endif
905 tp->reordering = min_t(u32, (metric + mss - 1) / mss,
906 sock_net(sk)->ipv4.sysctl_tcp_max_reordering);
907 }
908
909 /* This exciting event is worth to be remembered. 8) */
910 tp->reord_seen++;
911 NET_INC_STATS(sock_net(sk),
912 ts ? LINUX_MIB_TCPTSREORDER : LINUX_MIB_TCPSACKREORDER);
913}
914
915/* This must be called before lost_out is incremented */
916static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
917{
918 if (!tp->retransmit_skb_hint ||
919 before(TCP_SKB_CB(skb)->seq,
920 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
921 tp->retransmit_skb_hint = skb;
922}
923
924/* Sum the number of packets on the wire we have marked as lost.
925 * There are two cases we care about here:
926 * a) Packet hasn't been marked lost (nor retransmitted),
927 * and this is the first loss.
928 * b) Packet has been marked both lost and retransmitted,
929 * and this means we think it was lost again.
930 */
931static void tcp_sum_lost(struct tcp_sock *tp, struct sk_buff *skb)
932{
933 __u8 sacked = TCP_SKB_CB(skb)->sacked;
934
935 if (!(sacked & TCPCB_LOST) ||
936 ((sacked & TCPCB_LOST) && (sacked & TCPCB_SACKED_RETRANS)))
937 tp->lost += tcp_skb_pcount(skb);
938}
939
940static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
941{
942 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
943 tcp_verify_retransmit_hint(tp, skb);
944
945 tp->lost_out += tcp_skb_pcount(skb);
946 tcp_sum_lost(tp, skb);
947 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
948 }
949}
950
951void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb)
952{
953 tcp_verify_retransmit_hint(tp, skb);
954
955 tcp_sum_lost(tp, skb);
956 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
957 tp->lost_out += tcp_skb_pcount(skb);
958 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
959 }
960}
961
962/* This procedure tags the retransmission queue when SACKs arrive.
963 *
964 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
965 * Packets in queue with these bits set are counted in variables
966 * sacked_out, retrans_out and lost_out, correspondingly.
967 *
968 * Valid combinations are:
969 * Tag InFlight Description
970 * 0 1 - orig segment is in flight.
971 * S 0 - nothing flies, orig reached receiver.
972 * L 0 - nothing flies, orig lost by net.
973 * R 2 - both orig and retransmit are in flight.
974 * L|R 1 - orig is lost, retransmit is in flight.
975 * S|R 1 - orig reached receiver, retrans is still in flight.
976 * (L|S|R is logically valid, it could occur when L|R is sacked,
977 * but it is equivalent to plain S and code short-curcuits it to S.
978 * L|S is logically invalid, it would mean -1 packet in flight 8))
979 *
980 * These 6 states form finite state machine, controlled by the following events:
981 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
982 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
983 * 3. Loss detection event of two flavors:
984 * A. Scoreboard estimator decided the packet is lost.
985 * A'. Reno "three dupacks" marks head of queue lost.
986 * B. SACK arrives sacking SND.NXT at the moment, when the
987 * segment was retransmitted.
988 * 4. D-SACK added new rule: D-SACK changes any tag to S.
989 *
990 * It is pleasant to note, that state diagram turns out to be commutative,
991 * so that we are allowed not to be bothered by order of our actions,
992 * when multiple events arrive simultaneously. (see the function below).
993 *
994 * Reordering detection.
995 * --------------------
996 * Reordering metric is maximal distance, which a packet can be displaced
997 * in packet stream. With SACKs we can estimate it:
998 *
999 * 1. SACK fills old hole and the corresponding segment was not
1000 * ever retransmitted -> reordering. Alas, we cannot use it
1001 * when segment was retransmitted.
1002 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1003 * for retransmitted and already SACKed segment -> reordering..
1004 * Both of these heuristics are not used in Loss state, when we cannot
1005 * account for retransmits accurately.
1006 *
1007 * SACK block validation.
1008 * ----------------------
1009 *
1010 * SACK block range validation checks that the received SACK block fits to
1011 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1012 * Note that SND.UNA is not included to the range though being valid because
1013 * it means that the receiver is rather inconsistent with itself reporting
1014 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1015 * perfectly valid, however, in light of RFC2018 which explicitly states
1016 * that "SACK block MUST reflect the newest segment. Even if the newest
1017 * segment is going to be discarded ...", not that it looks very clever
1018 * in case of head skb. Due to potentional receiver driven attacks, we
1019 * choose to avoid immediate execution of a walk in write queue due to
1020 * reneging and defer head skb's loss recovery to standard loss recovery
1021 * procedure that will eventually trigger (nothing forbids us doing this).
1022 *
1023 * Implements also blockage to start_seq wrap-around. Problem lies in the
1024 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1025 * there's no guarantee that it will be before snd_nxt (n). The problem
1026 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1027 * wrap (s_w):
1028 *
1029 * <- outs wnd -> <- wrapzone ->
1030 * u e n u_w e_w s n_w
1031 * | | | | | | |
1032 * |<------------+------+----- TCP seqno space --------------+---------->|
1033 * ...-- <2^31 ->| |<--------...
1034 * ...---- >2^31 ------>| |<--------...
1035 *
1036 * Current code wouldn't be vulnerable but it's better still to discard such
1037 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1038 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1039 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1040 * equal to the ideal case (infinite seqno space without wrap caused issues).
1041 *
1042 * With D-SACK the lower bound is extended to cover sequence space below
1043 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1044 * again, D-SACK block must not to go across snd_una (for the same reason as
1045 * for the normal SACK blocks, explained above). But there all simplicity
1046 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1047 * fully below undo_marker they do not affect behavior in anyway and can
1048 * therefore be safely ignored. In rare cases (which are more or less
1049 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1050 * fragmentation and packet reordering past skb's retransmission. To consider
1051 * them correctly, the acceptable range must be extended even more though
1052 * the exact amount is rather hard to quantify. However, tp->max_window can
1053 * be used as an exaggerated estimate.
1054 */
1055static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack,
1056 u32 start_seq, u32 end_seq)
1057{
1058 /* Too far in future, or reversed (interpretation is ambiguous) */
1059 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
1060 return false;
1061
1062 /* Nasty start_seq wrap-around check (see comments above) */
1063 if (!before(start_seq, tp->snd_nxt))
1064 return false;
1065
1066 /* In outstanding window? ...This is valid exit for D-SACKs too.
1067 * start_seq == snd_una is non-sensical (see comments above)
1068 */
1069 if (after(start_seq, tp->snd_una))
1070 return true;
1071
1072 if (!is_dsack || !tp->undo_marker)
1073 return false;
1074
1075 /* ...Then it's D-SACK, and must reside below snd_una completely */
1076 if (after(end_seq, tp->snd_una))
1077 return false;
1078
1079 if (!before(start_seq, tp->undo_marker))
1080 return true;
1081
1082 /* Too old */
1083 if (!after(end_seq, tp->undo_marker))
1084 return false;
1085
1086 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1087 * start_seq < undo_marker and end_seq >= undo_marker.
1088 */
1089 return !before(start_seq, end_seq - tp->max_window);
1090}
1091
1092static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
1093 struct tcp_sack_block_wire *sp, int num_sacks,
1094 u32 prior_snd_una)
1095{
1096 struct tcp_sock *tp = tcp_sk(sk);
1097 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
1098 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
1099 bool dup_sack = false;
1100
1101 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
1102 dup_sack = true;
1103 tcp_dsack_seen(tp);
1104 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKRECV);
1105 } else if (num_sacks > 1) {
1106 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
1107 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
1108
1109 if (!after(end_seq_0, end_seq_1) &&
1110 !before(start_seq_0, start_seq_1)) {
1111 dup_sack = true;
1112 tcp_dsack_seen(tp);
1113 NET_INC_STATS(sock_net(sk),
1114 LINUX_MIB_TCPDSACKOFORECV);
1115 }
1116 }
1117
1118 /* D-SACK for already forgotten data... Do dumb counting. */
1119 if (dup_sack && tp->undo_marker && tp->undo_retrans > 0 &&
1120 !after(end_seq_0, prior_snd_una) &&
1121 after(end_seq_0, tp->undo_marker))
1122 tp->undo_retrans--;
1123
1124 return dup_sack;
1125}
1126
1127struct tcp_sacktag_state {
1128 u32 reord;
1129 /* Timestamps for earliest and latest never-retransmitted segment
1130 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1131 * but congestion control should still get an accurate delay signal.
1132 */
1133 u64 first_sackt;
1134 u64 last_sackt;
1135 struct rate_sample *rate;
1136 int flag;
1137 unsigned int mss_now;
1138};
1139
1140/* Check if skb is fully within the SACK block. In presence of GSO skbs,
1141 * the incoming SACK may not exactly match but we can find smaller MSS
1142 * aligned portion of it that matches. Therefore we might need to fragment
1143 * which may fail and creates some hassle (caller must handle error case
1144 * returns).
1145 *
1146 * FIXME: this could be merged to shift decision code
1147 */
1148static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
1149 u32 start_seq, u32 end_seq)
1150{
1151 int err;
1152 bool in_sack;
1153 unsigned int pkt_len;
1154 unsigned int mss;
1155
1156 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1157 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1158
1159 if (tcp_skb_pcount(skb) > 1 && !in_sack &&
1160 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1161 mss = tcp_skb_mss(skb);
1162 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1163
1164 if (!in_sack) {
1165 pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
1166 if (pkt_len < mss)
1167 pkt_len = mss;
1168 } else {
1169 pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
1170 if (pkt_len < mss)
1171 return -EINVAL;
1172 }
1173
1174 /* Round if necessary so that SACKs cover only full MSSes
1175 * and/or the remaining small portion (if present)
1176 */
1177 if (pkt_len > mss) {
1178 unsigned int new_len = (pkt_len / mss) * mss;
1179 if (!in_sack && new_len < pkt_len)
1180 new_len += mss;
1181 pkt_len = new_len;
1182 }
1183
1184 if (pkt_len >= skb->len && !in_sack)
1185 return 0;
1186
1187 err = tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
1188 pkt_len, mss, GFP_ATOMIC);
1189 if (err < 0)
1190 return err;
1191 }
1192
1193 return in_sack;
1194}
1195
1196/* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1197static u8 tcp_sacktag_one(struct sock *sk,
1198 struct tcp_sacktag_state *state, u8 sacked,
1199 u32 start_seq, u32 end_seq,
1200 int dup_sack, int pcount,
1201 u64 xmit_time)
1202{
1203 struct tcp_sock *tp = tcp_sk(sk);
1204
1205 /* Account D-SACK for retransmitted packet. */
1206 if (dup_sack && (sacked & TCPCB_RETRANS)) {
1207 if (tp->undo_marker && tp->undo_retrans > 0 &&
1208 after(end_seq, tp->undo_marker))
1209 tp->undo_retrans--;
1210 if ((sacked & TCPCB_SACKED_ACKED) &&
1211 before(start_seq, state->reord))
1212 state->reord = start_seq;
1213 }
1214
1215 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1216 if (!after(end_seq, tp->snd_una))
1217 return sacked;
1218
1219 if (!(sacked & TCPCB_SACKED_ACKED)) {
1220 tcp_rack_advance(tp, sacked, end_seq, xmit_time);
1221
1222 if (sacked & TCPCB_SACKED_RETRANS) {
1223 /* If the segment is not tagged as lost,
1224 * we do not clear RETRANS, believing
1225 * that retransmission is still in flight.
1226 */
1227 if (sacked & TCPCB_LOST) {
1228 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1229 tp->lost_out -= pcount;
1230 tp->retrans_out -= pcount;
1231 }
1232 } else {
1233 if (!(sacked & TCPCB_RETRANS)) {
1234 /* New sack for not retransmitted frame,
1235 * which was in hole. It is reordering.
1236 */
1237 if (before(start_seq,
1238 tcp_highest_sack_seq(tp)) &&
1239 before(start_seq, state->reord))
1240 state->reord = start_seq;
1241
1242 if (!after(end_seq, tp->high_seq))
1243 state->flag |= FLAG_ORIG_SACK_ACKED;
1244 if (state->first_sackt == 0)
1245 state->first_sackt = xmit_time;
1246 state->last_sackt = xmit_time;
1247 }
1248
1249 if (sacked & TCPCB_LOST) {
1250 sacked &= ~TCPCB_LOST;
1251 tp->lost_out -= pcount;
1252 }
1253 }
1254
1255 sacked |= TCPCB_SACKED_ACKED;
1256 state->flag |= FLAG_DATA_SACKED;
1257 tp->sacked_out += pcount;
1258 tp->delivered += pcount; /* Out-of-order packets delivered */
1259
1260 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1261 if (tp->lost_skb_hint &&
1262 before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq))
1263 tp->lost_cnt_hint += pcount;
1264 }
1265
1266 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1267 * frames and clear it. undo_retrans is decreased above, L|R frames
1268 * are accounted above as well.
1269 */
1270 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
1271 sacked &= ~TCPCB_SACKED_RETRANS;
1272 tp->retrans_out -= pcount;
1273 }
1274
1275 return sacked;
1276}
1277
1278/* Shift newly-SACKed bytes from this skb to the immediately previous
1279 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1280 */
1281static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *prev,
1282 struct sk_buff *skb,
1283 struct tcp_sacktag_state *state,
1284 unsigned int pcount, int shifted, int mss,
1285 bool dup_sack)
1286{
1287 struct tcp_sock *tp = tcp_sk(sk);
1288 u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */
1289 u32 end_seq = start_seq + shifted; /* end of newly-SACKed */
1290
1291 BUG_ON(!pcount);
1292
1293 /* Adjust counters and hints for the newly sacked sequence
1294 * range but discard the return value since prev is already
1295 * marked. We must tag the range first because the seq
1296 * advancement below implicitly advances
1297 * tcp_highest_sack_seq() when skb is highest_sack.
1298 */
1299 tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
1300 start_seq, end_seq, dup_sack, pcount,
1301 tcp_skb_timestamp_us(skb));
1302 tcp_rate_skb_delivered(sk, skb, state->rate);
1303
1304 if (skb == tp->lost_skb_hint)
1305 tp->lost_cnt_hint += pcount;
1306
1307 TCP_SKB_CB(prev)->end_seq += shifted;
1308 TCP_SKB_CB(skb)->seq += shifted;
1309
1310 tcp_skb_pcount_add(prev, pcount);
1311 WARN_ON_ONCE(tcp_skb_pcount(skb) < pcount);
1312 tcp_skb_pcount_add(skb, -pcount);
1313
1314 /* When we're adding to gso_segs == 1, gso_size will be zero,
1315 * in theory this shouldn't be necessary but as long as DSACK
1316 * code can come after this skb later on it's better to keep
1317 * setting gso_size to something.
1318 */
1319 if (!TCP_SKB_CB(prev)->tcp_gso_size)
1320 TCP_SKB_CB(prev)->tcp_gso_size = mss;
1321
1322 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1323 if (tcp_skb_pcount(skb) <= 1)
1324 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1325
1326 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1327 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
1328
1329 if (skb->len > 0) {
1330 BUG_ON(!tcp_skb_pcount(skb));
1331 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTED);
1332 return false;
1333 }
1334
1335 /* Whole SKB was eaten :-) */
1336
1337 if (skb == tp->retransmit_skb_hint)
1338 tp->retransmit_skb_hint = prev;
1339 if (skb == tp->lost_skb_hint) {
1340 tp->lost_skb_hint = prev;
1341 tp->lost_cnt_hint -= tcp_skb_pcount(prev);
1342 }
1343
1344 TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1345 TCP_SKB_CB(prev)->eor = TCP_SKB_CB(skb)->eor;
1346 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1347 TCP_SKB_CB(prev)->end_seq++;
1348
1349 if (skb == tcp_highest_sack(sk))
1350 tcp_advance_highest_sack(sk, skb);
1351
1352 tcp_skb_collapse_tstamp(prev, skb);
1353 if (unlikely(TCP_SKB_CB(prev)->tx.delivered_mstamp))
1354 TCP_SKB_CB(prev)->tx.delivered_mstamp = 0;
1355
1356 tcp_rtx_queue_unlink_and_free(skb, sk);
1357
1358 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKMERGED);
1359
1360 return true;
1361}
1362
1363/* I wish gso_size would have a bit more sane initialization than
1364 * something-or-zero which complicates things
1365 */
1366static int tcp_skb_seglen(const struct sk_buff *skb)
1367{
1368 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
1369}
1370
1371/* Shifting pages past head area doesn't work */
1372static int skb_can_shift(const struct sk_buff *skb)
1373{
1374 return !skb_headlen(skb) && skb_is_nonlinear(skb);
1375}
1376
1377int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from,
1378 int pcount, int shiftlen)
1379{
1380 /* TCP min gso_size is 8 bytes (TCP_MIN_GSO_SIZE)
1381 * Since TCP_SKB_CB(skb)->tcp_gso_segs is 16 bits, we need
1382 * to make sure not storing more than 65535 * 8 bytes per skb,
1383 * even if current MSS is bigger.
1384 */
1385 if (unlikely(to->len + shiftlen >= 65535 * TCP_MIN_GSO_SIZE))
1386 return 0;
1387 if (unlikely(tcp_skb_pcount(to) + pcount > 65535))
1388 return 0;
1389 return skb_shift(to, from, shiftlen);
1390}
1391
1392/* Try collapsing SACK blocks spanning across multiple skbs to a single
1393 * skb.
1394 */
1395static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
1396 struct tcp_sacktag_state *state,
1397 u32 start_seq, u32 end_seq,
1398 bool dup_sack)
1399{
1400 struct tcp_sock *tp = tcp_sk(sk);
1401 struct sk_buff *prev;
1402 int mss;
1403 int pcount = 0;
1404 int len;
1405 int in_sack;
1406
1407 /* Normally R but no L won't result in plain S */
1408 if (!dup_sack &&
1409 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
1410 goto fallback;
1411 if (!skb_can_shift(skb))
1412 goto fallback;
1413 /* This frame is about to be dropped (was ACKed). */
1414 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1415 goto fallback;
1416
1417 /* Can only happen with delayed DSACK + discard craziness */
1418 prev = skb_rb_prev(skb);
1419 if (!prev)
1420 goto fallback;
1421
1422 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
1423 goto fallback;
1424
1425 if (!tcp_skb_can_collapse_to(prev))
1426 goto fallback;
1427
1428 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1429 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1430
1431 if (in_sack) {
1432 len = skb->len;
1433 pcount = tcp_skb_pcount(skb);
1434 mss = tcp_skb_seglen(skb);
1435
1436 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1437 * drop this restriction as unnecessary
1438 */
1439 if (mss != tcp_skb_seglen(prev))
1440 goto fallback;
1441 } else {
1442 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
1443 goto noop;
1444 /* CHECKME: This is non-MSS split case only?, this will
1445 * cause skipped skbs due to advancing loop btw, original
1446 * has that feature too
1447 */
1448 if (tcp_skb_pcount(skb) <= 1)
1449 goto noop;
1450
1451 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1452 if (!in_sack) {
1453 /* TODO: head merge to next could be attempted here
1454 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1455 * though it might not be worth of the additional hassle
1456 *
1457 * ...we can probably just fallback to what was done
1458 * previously. We could try merging non-SACKed ones
1459 * as well but it probably isn't going to buy off
1460 * because later SACKs might again split them, and
1461 * it would make skb timestamp tracking considerably
1462 * harder problem.
1463 */
1464 goto fallback;
1465 }
1466
1467 len = end_seq - TCP_SKB_CB(skb)->seq;
1468 BUG_ON(len < 0);
1469 BUG_ON(len > skb->len);
1470
1471 /* MSS boundaries should be honoured or else pcount will
1472 * severely break even though it makes things bit trickier.
1473 * Optimize common case to avoid most of the divides
1474 */
1475 mss = tcp_skb_mss(skb);
1476
1477 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1478 * drop this restriction as unnecessary
1479 */
1480 if (mss != tcp_skb_seglen(prev))
1481 goto fallback;
1482
1483 if (len == mss) {
1484 pcount = 1;
1485 } else if (len < mss) {
1486 goto noop;
1487 } else {
1488 pcount = len / mss;
1489 len = pcount * mss;
1490 }
1491 }
1492
1493 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1494 if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una))
1495 goto fallback;
1496
1497 if (!tcp_skb_shift(prev, skb, pcount, len))
1498 goto fallback;
1499 if (!tcp_shifted_skb(sk, prev, skb, state, pcount, len, mss, dup_sack))
1500 goto out;
1501
1502 /* Hole filled allows collapsing with the next as well, this is very
1503 * useful when hole on every nth skb pattern happens
1504 */
1505 skb = skb_rb_next(prev);
1506 if (!skb)
1507 goto out;
1508
1509 if (!skb_can_shift(skb) ||
1510 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
1511 (mss != tcp_skb_seglen(skb)))
1512 goto out;
1513
1514 len = skb->len;
1515 pcount = tcp_skb_pcount(skb);
1516 if (tcp_skb_shift(prev, skb, pcount, len))
1517 tcp_shifted_skb(sk, prev, skb, state, pcount,
1518 len, mss, 0);
1519
1520out:
1521 return prev;
1522
1523noop:
1524 return skb;
1525
1526fallback:
1527 NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
1528 return NULL;
1529}
1530
1531static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
1532 struct tcp_sack_block *next_dup,
1533 struct tcp_sacktag_state *state,
1534 u32 start_seq, u32 end_seq,
1535 bool dup_sack_in)
1536{
1537 struct tcp_sock *tp = tcp_sk(sk);
1538 struct sk_buff *tmp;
1539
1540 skb_rbtree_walk_from(skb) {
1541 int in_sack = 0;
1542 bool dup_sack = dup_sack_in;
1543
1544 /* queue is in-order => we can short-circuit the walk early */
1545 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1546 break;
1547
1548 if (next_dup &&
1549 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
1550 in_sack = tcp_match_skb_to_sack(sk, skb,
1551 next_dup->start_seq,
1552 next_dup->end_seq);
1553 if (in_sack > 0)
1554 dup_sack = true;
1555 }
1556
1557 /* skb reference here is a bit tricky to get right, since
1558 * shifting can eat and free both this skb and the next,
1559 * so not even _safe variant of the loop is enough.
1560 */
1561 if (in_sack <= 0) {
1562 tmp = tcp_shift_skb_data(sk, skb, state,
1563 start_seq, end_seq, dup_sack);
1564 if (tmp) {
1565 if (tmp != skb) {
1566 skb = tmp;
1567 continue;
1568 }
1569
1570 in_sack = 0;
1571 } else {
1572 in_sack = tcp_match_skb_to_sack(sk, skb,
1573 start_seq,
1574 end_seq);
1575 }
1576 }
1577
1578 if (unlikely(in_sack < 0))
1579 break;
1580
1581 if (in_sack) {
1582 TCP_SKB_CB(skb)->sacked =
1583 tcp_sacktag_one(sk,
1584 state,
1585 TCP_SKB_CB(skb)->sacked,
1586 TCP_SKB_CB(skb)->seq,
1587 TCP_SKB_CB(skb)->end_seq,
1588 dup_sack,
1589 tcp_skb_pcount(skb),
1590 tcp_skb_timestamp_us(skb));
1591 tcp_rate_skb_delivered(sk, skb, state->rate);
1592 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1593 list_del_init(&skb->tcp_tsorted_anchor);
1594
1595 if (!before(TCP_SKB_CB(skb)->seq,
1596 tcp_highest_sack_seq(tp)))
1597 tcp_advance_highest_sack(sk, skb);
1598 }
1599 }
1600 return skb;
1601}
1602
1603static struct sk_buff *tcp_sacktag_bsearch(struct sock *sk, u32 seq)
1604{
1605 struct rb_node *parent, **p = &sk->tcp_rtx_queue.rb_node;
1606 struct sk_buff *skb;
1607
1608 while (*p) {
1609 parent = *p;
1610 skb = rb_to_skb(parent);
1611 if (before(seq, TCP_SKB_CB(skb)->seq)) {
1612 p = &parent->rb_left;
1613 continue;
1614 }
1615 if (!before(seq, TCP_SKB_CB(skb)->end_seq)) {
1616 p = &parent->rb_right;
1617 continue;
1618 }
1619 return skb;
1620 }
1621 return NULL;
1622}
1623
1624static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
1625 u32 skip_to_seq)
1626{
1627 if (skb && after(TCP_SKB_CB(skb)->seq, skip_to_seq))
1628 return skb;
1629
1630 return tcp_sacktag_bsearch(sk, skip_to_seq);
1631}
1632
1633static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
1634 struct sock *sk,
1635 struct tcp_sack_block *next_dup,
1636 struct tcp_sacktag_state *state,
1637 u32 skip_to_seq)
1638{
1639 if (!next_dup)
1640 return skb;
1641
1642 if (before(next_dup->start_seq, skip_to_seq)) {
1643 skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq);
1644 skb = tcp_sacktag_walk(skb, sk, NULL, state,
1645 next_dup->start_seq, next_dup->end_seq,
1646 1);
1647 }
1648
1649 return skb;
1650}
1651
1652static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache)
1653{
1654 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1655}
1656
1657static int
1658tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
1659 u32 prior_snd_una, struct tcp_sacktag_state *state)
1660{
1661 struct tcp_sock *tp = tcp_sk(sk);
1662 const unsigned char *ptr = (skb_transport_header(ack_skb) +
1663 TCP_SKB_CB(ack_skb)->sacked);
1664 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
1665 struct tcp_sack_block sp[TCP_NUM_SACKS];
1666 struct tcp_sack_block *cache;
1667 struct sk_buff *skb;
1668 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
1669 int used_sacks;
1670 bool found_dup_sack = false;
1671 int i, j;
1672 int first_sack_index;
1673
1674 state->flag = 0;
1675 state->reord = tp->snd_nxt;
1676
1677 if (!tp->sacked_out)
1678 tcp_highest_sack_reset(sk);
1679
1680 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
1681 num_sacks, prior_snd_una);
1682 if (found_dup_sack) {
1683 state->flag |= FLAG_DSACKING_ACK;
1684 tp->delivered++; /* A spurious retransmission is delivered */
1685 }
1686
1687 /* Eliminate too old ACKs, but take into
1688 * account more or less fresh ones, they can
1689 * contain valid SACK info.
1690 */
1691 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
1692 return 0;
1693
1694 if (!tp->packets_out)
1695 goto out;
1696
1697 used_sacks = 0;
1698 first_sack_index = 0;
1699 for (i = 0; i < num_sacks; i++) {
1700 bool dup_sack = !i && found_dup_sack;
1701
1702 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
1703 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
1704
1705 if (!tcp_is_sackblock_valid(tp, dup_sack,
1706 sp[used_sacks].start_seq,
1707 sp[used_sacks].end_seq)) {
1708 int mib_idx;
1709
1710 if (dup_sack) {
1711 if (!tp->undo_marker)
1712 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO;
1713 else
1714 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD;
1715 } else {
1716 /* Don't count olds caused by ACK reordering */
1717 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
1718 !after(sp[used_sacks].end_seq, tp->snd_una))
1719 continue;
1720 mib_idx = LINUX_MIB_TCPSACKDISCARD;
1721 }
1722
1723 NET_INC_STATS(sock_net(sk), mib_idx);
1724 if (i == 0)
1725 first_sack_index = -1;
1726 continue;
1727 }
1728
1729 /* Ignore very old stuff early */
1730 if (!after(sp[used_sacks].end_seq, prior_snd_una))
1731 continue;
1732
1733 used_sacks++;
1734 }
1735
1736 /* order SACK blocks to allow in order walk of the retrans queue */
1737 for (i = used_sacks - 1; i > 0; i--) {
1738 for (j = 0; j < i; j++) {
1739 if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
1740 swap(sp[j], sp[j + 1]);
1741
1742 /* Track where the first SACK block goes to */
1743 if (j == first_sack_index)
1744 first_sack_index = j + 1;
1745 }
1746 }
1747 }
1748
1749 state->mss_now = tcp_current_mss(sk);
1750 skb = NULL;
1751 i = 0;
1752
1753 if (!tp->sacked_out) {
1754 /* It's already past, so skip checking against it */
1755 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1756 } else {
1757 cache = tp->recv_sack_cache;
1758 /* Skip empty blocks in at head of the cache */
1759 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
1760 !cache->end_seq)
1761 cache++;
1762 }
1763
1764 while (i < used_sacks) {
1765 u32 start_seq = sp[i].start_seq;
1766 u32 end_seq = sp[i].end_seq;
1767 bool dup_sack = (found_dup_sack && (i == first_sack_index));
1768 struct tcp_sack_block *next_dup = NULL;
1769
1770 if (found_dup_sack && ((i + 1) == first_sack_index))
1771 next_dup = &sp[i + 1];
1772
1773 /* Skip too early cached blocks */
1774 while (tcp_sack_cache_ok(tp, cache) &&
1775 !before(start_seq, cache->end_seq))
1776 cache++;
1777
1778 /* Can skip some work by looking recv_sack_cache? */
1779 if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
1780 after(end_seq, cache->start_seq)) {
1781
1782 /* Head todo? */
1783 if (before(start_seq, cache->start_seq)) {
1784 skb = tcp_sacktag_skip(skb, sk, start_seq);
1785 skb = tcp_sacktag_walk(skb, sk, next_dup,
1786 state,
1787 start_seq,
1788 cache->start_seq,
1789 dup_sack);
1790 }
1791
1792 /* Rest of the block already fully processed? */
1793 if (!after(end_seq, cache->end_seq))
1794 goto advance_sp;
1795
1796 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
1797 state,
1798 cache->end_seq);
1799
1800 /* ...tail remains todo... */
1801 if (tcp_highest_sack_seq(tp) == cache->end_seq) {
1802 /* ...but better entrypoint exists! */
1803 skb = tcp_highest_sack(sk);
1804 if (!skb)
1805 break;
1806 cache++;
1807 goto walk;
1808 }
1809
1810 skb = tcp_sacktag_skip(skb, sk, cache->end_seq);
1811 /* Check overlap against next cached too (past this one already) */
1812 cache++;
1813 continue;
1814 }
1815
1816 if (!before(start_seq, tcp_highest_sack_seq(tp))) {
1817 skb = tcp_highest_sack(sk);
1818 if (!skb)
1819 break;
1820 }
1821 skb = tcp_sacktag_skip(skb, sk, start_seq);
1822
1823walk:
1824 skb = tcp_sacktag_walk(skb, sk, next_dup, state,
1825 start_seq, end_seq, dup_sack);
1826
1827advance_sp:
1828 i++;
1829 }
1830
1831 /* Clear the head of the cache sack blocks so we can skip it next time */
1832 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
1833 tp->recv_sack_cache[i].start_seq = 0;
1834 tp->recv_sack_cache[i].end_seq = 0;
1835 }
1836 for (j = 0; j < used_sacks; j++)
1837 tp->recv_sack_cache[i++] = sp[j];
1838
1839 if (inet_csk(sk)->icsk_ca_state != TCP_CA_Loss || tp->undo_marker)
1840 tcp_check_sack_reordering(sk, state->reord, 0);
1841
1842 tcp_verify_left_out(tp);
1843out:
1844
1845#if FASTRETRANS_DEBUG > 0
1846 WARN_ON((int)tp->sacked_out < 0);
1847 WARN_ON((int)tp->lost_out < 0);
1848 WARN_ON((int)tp->retrans_out < 0);
1849 WARN_ON((int)tcp_packets_in_flight(tp) < 0);
1850#endif
1851 return state->flag;
1852}
1853
1854/* Limits sacked_out so that sum with lost_out isn't ever larger than
1855 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1856 */
1857static bool tcp_limit_reno_sacked(struct tcp_sock *tp)
1858{
1859 u32 holes;
1860
1861 holes = max(tp->lost_out, 1U);
1862 holes = min(holes, tp->packets_out);
1863
1864 if ((tp->sacked_out + holes) > tp->packets_out) {
1865 tp->sacked_out = tp->packets_out - holes;
1866 return true;
1867 }
1868 return false;
1869}
1870
1871/* If we receive more dupacks than we expected counting segments
1872 * in assumption of absent reordering, interpret this as reordering.
1873 * The only another reason could be bug in receiver TCP.
1874 */
1875static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1876{
1877 struct tcp_sock *tp = tcp_sk(sk);
1878
1879 if (!tcp_limit_reno_sacked(tp))
1880 return;
1881
1882 tp->reordering = min_t(u32, tp->packets_out + addend,
1883 sock_net(sk)->ipv4.sysctl_tcp_max_reordering);
1884 tp->reord_seen++;
1885 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRENOREORDER);
1886}
1887
1888/* Emulate SACKs for SACKless connection: account for a new dupack. */
1889
1890static void tcp_add_reno_sack(struct sock *sk, int num_dupack)
1891{
1892 if (num_dupack) {
1893 struct tcp_sock *tp = tcp_sk(sk);
1894 u32 prior_sacked = tp->sacked_out;
1895 s32 delivered;
1896
1897 tp->sacked_out += num_dupack;
1898 tcp_check_reno_reordering(sk, 0);
1899 delivered = tp->sacked_out - prior_sacked;
1900 if (delivered > 0)
1901 tp->delivered += delivered;
1902 tcp_verify_left_out(tp);
1903 }
1904}
1905
1906/* Account for ACK, ACKing some data in Reno Recovery phase. */
1907
1908static void tcp_remove_reno_sacks(struct sock *sk, int acked)
1909{
1910 struct tcp_sock *tp = tcp_sk(sk);
1911
1912 if (acked > 0) {
1913 /* One ACK acked hole. The rest eat duplicate ACKs. */
1914 tp->delivered += max_t(int, acked - tp->sacked_out, 1);
1915 if (acked - 1 >= tp->sacked_out)
1916 tp->sacked_out = 0;
1917 else
1918 tp->sacked_out -= acked - 1;
1919 }
1920 tcp_check_reno_reordering(sk, acked);
1921 tcp_verify_left_out(tp);
1922}
1923
1924static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1925{
1926 tp->sacked_out = 0;
1927}
1928
1929void tcp_clear_retrans(struct tcp_sock *tp)
1930{
1931 tp->retrans_out = 0;
1932 tp->lost_out = 0;
1933 tp->undo_marker = 0;
1934 tp->undo_retrans = -1;
1935 tp->sacked_out = 0;
1936}
1937
1938static inline void tcp_init_undo(struct tcp_sock *tp)
1939{
1940 tp->undo_marker = tp->snd_una;
1941 /* Retransmission still in flight may cause DSACKs later. */
1942 tp->undo_retrans = tp->retrans_out ? : -1;
1943}
1944
1945static bool tcp_is_rack(const struct sock *sk)
1946{
1947 return sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION;
1948}
1949
1950/* If we detect SACK reneging, forget all SACK information
1951 * and reset tags completely, otherwise preserve SACKs. If receiver
1952 * dropped its ofo queue, we will know this due to reneging detection.
1953 */
1954static void tcp_timeout_mark_lost(struct sock *sk)
1955{
1956 struct tcp_sock *tp = tcp_sk(sk);
1957 struct sk_buff *skb, *head;
1958 bool is_reneg; /* is receiver reneging on SACKs? */
1959
1960 head = tcp_rtx_queue_head(sk);
1961 is_reneg = head && (TCP_SKB_CB(head)->sacked & TCPCB_SACKED_ACKED);
1962 if (is_reneg) {
1963 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
1964 tp->sacked_out = 0;
1965 /* Mark SACK reneging until we recover from this loss event. */
1966 tp->is_sack_reneg = 1;
1967 } else if (tcp_is_reno(tp)) {
1968 tcp_reset_reno_sack(tp);
1969 }
1970
1971 skb = head;
1972 skb_rbtree_walk_from(skb) {
1973 if (is_reneg)
1974 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1975 else if (tcp_is_rack(sk) && skb != head &&
1976 tcp_rack_skb_timeout(tp, skb, 0) > 0)
1977 continue; /* Don't mark recently sent ones lost yet */
1978 tcp_mark_skb_lost(sk, skb);
1979 }
1980 tcp_verify_left_out(tp);
1981 tcp_clear_all_retrans_hints(tp);
1982}
1983
1984/* Enter Loss state. */
1985void tcp_enter_loss(struct sock *sk)
1986{
1987 const struct inet_connection_sock *icsk = inet_csk(sk);
1988 struct tcp_sock *tp = tcp_sk(sk);
1989 struct net *net = sock_net(sk);
1990 bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery;
1991
1992 tcp_timeout_mark_lost(sk);
1993
1994 /* Reduce ssthresh if it has not yet been made inside this window. */
1995 if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
1996 !after(tp->high_seq, tp->snd_una) ||
1997 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1998 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1999 tp->prior_cwnd = tp->snd_cwnd;
2000 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2001 tcp_ca_event(sk, CA_EVENT_LOSS);
2002 tcp_init_undo(tp);
2003 }
2004 tp->snd_cwnd = tcp_packets_in_flight(tp) + 1;
2005 tp->snd_cwnd_cnt = 0;
2006 tp->snd_cwnd_stamp = tcp_jiffies32;
2007
2008 /* Timeout in disordered state after receiving substantial DUPACKs
2009 * suggests that the degree of reordering is over-estimated.
2010 */
2011 if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
2012 tp->sacked_out >= net->ipv4.sysctl_tcp_reordering)
2013 tp->reordering = min_t(unsigned int, tp->reordering,
2014 net->ipv4.sysctl_tcp_reordering);
2015 tcp_set_ca_state(sk, TCP_CA_Loss);
2016 tp->high_seq = tp->snd_nxt;
2017 tcp_ecn_queue_cwr(tp);
2018
2019 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
2020 * loss recovery is underway except recurring timeout(s) on
2021 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
2022 */
2023 tp->frto = net->ipv4.sysctl_tcp_frto &&
2024 (new_recovery || icsk->icsk_retransmits) &&
2025 !inet_csk(sk)->icsk_mtup.probe_size;
2026}
2027
2028/* If ACK arrived pointing to a remembered SACK, it means that our
2029 * remembered SACKs do not reflect real state of receiver i.e.
2030 * receiver _host_ is heavily congested (or buggy).
2031 *
2032 * To avoid big spurious retransmission bursts due to transient SACK
2033 * scoreboard oddities that look like reneging, we give the receiver a
2034 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
2035 * restore sanity to the SACK scoreboard. If the apparent reneging
2036 * persists until this RTO then we'll clear the SACK scoreboard.
2037 */
2038static bool tcp_check_sack_reneging(struct sock *sk, int flag)
2039{
2040 if (flag & FLAG_SACK_RENEGING) {
2041 struct tcp_sock *tp = tcp_sk(sk);
2042 unsigned long delay = max(usecs_to_jiffies(tp->srtt_us >> 4),
2043 msecs_to_jiffies(10));
2044
2045 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2046 delay, TCP_RTO_MAX);
2047 return true;
2048 }
2049 return false;
2050}
2051
2052/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2053 * counter when SACK is enabled (without SACK, sacked_out is used for
2054 * that purpose).
2055 *
2056 * With reordering, holes may still be in flight, so RFC3517 recovery
2057 * uses pure sacked_out (total number of SACKed segments) even though
2058 * it violates the RFC that uses duplicate ACKs, often these are equal
2059 * but when e.g. out-of-window ACKs or packet duplication occurs,
2060 * they differ. Since neither occurs due to loss, TCP should really
2061 * ignore them.
2062 */
2063static inline int tcp_dupack_heuristics(const struct tcp_sock *tp)
2064{
2065 return tp->sacked_out + 1;
2066}
2067
2068/* Linux NewReno/SACK/ECN state machine.
2069 * --------------------------------------
2070 *
2071 * "Open" Normal state, no dubious events, fast path.
2072 * "Disorder" In all the respects it is "Open",
2073 * but requires a bit more attention. It is entered when
2074 * we see some SACKs or dupacks. It is split of "Open"
2075 * mainly to move some processing from fast path to slow one.
2076 * "CWR" CWND was reduced due to some Congestion Notification event.
2077 * It can be ECN, ICMP source quench, local device congestion.
2078 * "Recovery" CWND was reduced, we are fast-retransmitting.
2079 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2080 *
2081 * tcp_fastretrans_alert() is entered:
2082 * - each incoming ACK, if state is not "Open"
2083 * - when arrived ACK is unusual, namely:
2084 * * SACK
2085 * * Duplicate ACK.
2086 * * ECN ECE.
2087 *
2088 * Counting packets in flight is pretty simple.
2089 *
2090 * in_flight = packets_out - left_out + retrans_out
2091 *
2092 * packets_out is SND.NXT-SND.UNA counted in packets.
2093 *
2094 * retrans_out is number of retransmitted segments.
2095 *
2096 * left_out is number of segments left network, but not ACKed yet.
2097 *
2098 * left_out = sacked_out + lost_out
2099 *
2100 * sacked_out: Packets, which arrived to receiver out of order
2101 * and hence not ACKed. With SACKs this number is simply
2102 * amount of SACKed data. Even without SACKs
2103 * it is easy to give pretty reliable estimate of this number,
2104 * counting duplicate ACKs.
2105 *
2106 * lost_out: Packets lost by network. TCP has no explicit
2107 * "loss notification" feedback from network (for now).
2108 * It means that this number can be only _guessed_.
2109 * Actually, it is the heuristics to predict lossage that
2110 * distinguishes different algorithms.
2111 *
2112 * F.e. after RTO, when all the queue is considered as lost,
2113 * lost_out = packets_out and in_flight = retrans_out.
2114 *
2115 * Essentially, we have now a few algorithms detecting
2116 * lost packets.
2117 *
2118 * If the receiver supports SACK:
2119 *
2120 * RFC6675/3517: It is the conventional algorithm. A packet is
2121 * considered lost if the number of higher sequence packets
2122 * SACKed is greater than or equal the DUPACK thoreshold
2123 * (reordering). This is implemented in tcp_mark_head_lost and
2124 * tcp_update_scoreboard.
2125 *
2126 * RACK (draft-ietf-tcpm-rack-01): it is a newer algorithm
2127 * (2017-) that checks timing instead of counting DUPACKs.
2128 * Essentially a packet is considered lost if it's not S/ACKed
2129 * after RTT + reordering_window, where both metrics are
2130 * dynamically measured and adjusted. This is implemented in
2131 * tcp_rack_mark_lost.
2132 *
2133 * If the receiver does not support SACK:
2134 *
2135 * NewReno (RFC6582): in Recovery we assume that one segment
2136 * is lost (classic Reno). While we are in Recovery and
2137 * a partial ACK arrives, we assume that one more packet
2138 * is lost (NewReno). This heuristics are the same in NewReno
2139 * and SACK.
2140 *
2141 * Really tricky (and requiring careful tuning) part of algorithm
2142 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2143 * The first determines the moment _when_ we should reduce CWND and,
2144 * hence, slow down forward transmission. In fact, it determines the moment
2145 * when we decide that hole is caused by loss, rather than by a reorder.
2146 *
2147 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2148 * holes, caused by lost packets.
2149 *
2150 * And the most logically complicated part of algorithm is undo
2151 * heuristics. We detect false retransmits due to both too early
2152 * fast retransmit (reordering) and underestimated RTO, analyzing
2153 * timestamps and D-SACKs. When we detect that some segments were
2154 * retransmitted by mistake and CWND reduction was wrong, we undo
2155 * window reduction and abort recovery phase. This logic is hidden
2156 * inside several functions named tcp_try_undo_<something>.
2157 */
2158
2159/* This function decides, when we should leave Disordered state
2160 * and enter Recovery phase, reducing congestion window.
2161 *
2162 * Main question: may we further continue forward transmission
2163 * with the same cwnd?
2164 */
2165static bool tcp_time_to_recover(struct sock *sk, int flag)
2166{
2167 struct tcp_sock *tp = tcp_sk(sk);
2168
2169 /* Trick#1: The loss is proven. */
2170 if (tp->lost_out)
2171 return true;
2172
2173 /* Not-A-Trick#2 : Classic rule... */
2174 if (!tcp_is_rack(sk) && tcp_dupack_heuristics(tp) > tp->reordering)
2175 return true;
2176
2177 return false;
2178}
2179
2180/* Detect loss in event "A" above by marking head of queue up as lost.
2181 * For non-SACK(Reno) senders, the first "packets" number of segments
2182 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2183 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2184 * the maximum SACKed segments to pass before reaching this limit.
2185 */
2186static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
2187{
2188 struct tcp_sock *tp = tcp_sk(sk);
2189 struct sk_buff *skb;
2190 int cnt, oldcnt, lost;
2191 unsigned int mss;
2192 /* Use SACK to deduce losses of new sequences sent during recovery */
2193 const u32 loss_high = tcp_is_sack(tp) ? tp->snd_nxt : tp->high_seq;
2194
2195 WARN_ON(packets > tp->packets_out);
2196 skb = tp->lost_skb_hint;
2197 if (skb) {
2198 /* Head already handled? */
2199 if (mark_head && after(TCP_SKB_CB(skb)->seq, tp->snd_una))
2200 return;
2201 cnt = tp->lost_cnt_hint;
2202 } else {
2203 skb = tcp_rtx_queue_head(sk);
2204 cnt = 0;
2205 }
2206
2207 skb_rbtree_walk_from(skb) {
2208 /* TODO: do this better */
2209 /* this is not the most efficient way to do this... */
2210 tp->lost_skb_hint = skb;
2211 tp->lost_cnt_hint = cnt;
2212
2213 if (after(TCP_SKB_CB(skb)->end_seq, loss_high))
2214 break;
2215
2216 oldcnt = cnt;
2217 if (tcp_is_reno(tp) ||
2218 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
2219 cnt += tcp_skb_pcount(skb);
2220
2221 if (cnt > packets) {
2222 if (tcp_is_sack(tp) ||
2223 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) ||
2224 (oldcnt >= packets))
2225 break;
2226
2227 mss = tcp_skb_mss(skb);
2228 /* If needed, chop off the prefix to mark as lost. */
2229 lost = (packets - oldcnt) * mss;
2230 if (lost < skb->len &&
2231 tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
2232 lost, mss, GFP_ATOMIC) < 0)
2233 break;
2234 cnt = packets;
2235 }
2236
2237 tcp_skb_mark_lost(tp, skb);
2238
2239 if (mark_head)
2240 break;
2241 }
2242 tcp_verify_left_out(tp);
2243}
2244
2245/* Account newly detected lost packet(s) */
2246
2247static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
2248{
2249 struct tcp_sock *tp = tcp_sk(sk);
2250
2251 if (tcp_is_sack(tp)) {
2252 int sacked_upto = tp->sacked_out - tp->reordering;
2253 if (sacked_upto >= 0)
2254 tcp_mark_head_lost(sk, sacked_upto, 0);
2255 else if (fast_rexmit)
2256 tcp_mark_head_lost(sk, 1, 1);
2257 }
2258}
2259
2260static bool tcp_tsopt_ecr_before(const struct tcp_sock *tp, u32 when)
2261{
2262 return tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2263 before(tp->rx_opt.rcv_tsecr, when);
2264}
2265
2266/* skb is spurious retransmitted if the returned timestamp echo
2267 * reply is prior to the skb transmission time
2268 */
2269static bool tcp_skb_spurious_retrans(const struct tcp_sock *tp,
2270 const struct sk_buff *skb)
2271{
2272 return (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) &&
2273 tcp_tsopt_ecr_before(tp, tcp_skb_timestamp(skb));
2274}
2275
2276/* Nothing was retransmitted or returned timestamp is less
2277 * than timestamp of the first retransmission.
2278 */
2279static inline bool tcp_packet_delayed(const struct tcp_sock *tp)
2280{
2281 return tp->retrans_stamp &&
2282 tcp_tsopt_ecr_before(tp, tp->retrans_stamp);
2283}
2284
2285/* Undo procedures. */
2286
2287/* We can clear retrans_stamp when there are no retransmissions in the
2288 * window. It would seem that it is trivially available for us in
2289 * tp->retrans_out, however, that kind of assumptions doesn't consider
2290 * what will happen if errors occur when sending retransmission for the
2291 * second time. ...It could the that such segment has only
2292 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2293 * the head skb is enough except for some reneging corner cases that
2294 * are not worth the effort.
2295 *
2296 * Main reason for all this complexity is the fact that connection dying
2297 * time now depends on the validity of the retrans_stamp, in particular,
2298 * that successive retransmissions of a segment must not advance
2299 * retrans_stamp under any conditions.
2300 */
2301static bool tcp_any_retrans_done(const struct sock *sk)
2302{
2303 const struct tcp_sock *tp = tcp_sk(sk);
2304 struct sk_buff *skb;
2305
2306 if (tp->retrans_out)
2307 return true;
2308
2309 skb = tcp_rtx_queue_head(sk);
2310 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
2311 return true;
2312
2313 return false;
2314}
2315
2316static void DBGUNDO(struct sock *sk, const char *msg)
2317{
2318#if FASTRETRANS_DEBUG > 1
2319 struct tcp_sock *tp = tcp_sk(sk);
2320 struct inet_sock *inet = inet_sk(sk);
2321
2322 if (sk->sk_family == AF_INET) {
2323 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2324 msg,
2325 &inet->inet_daddr, ntohs(inet->inet_dport),
2326 tp->snd_cwnd, tcp_left_out(tp),
2327 tp->snd_ssthresh, tp->prior_ssthresh,
2328 tp->packets_out);
2329 }
2330#if IS_ENABLED(CONFIG_IPV6)
2331 else if (sk->sk_family == AF_INET6) {
2332 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2333 msg,
2334 &sk->sk_v6_daddr, ntohs(inet->inet_dport),
2335 tp->snd_cwnd, tcp_left_out(tp),
2336 tp->snd_ssthresh, tp->prior_ssthresh,
2337 tp->packets_out);
2338 }
2339#endif
2340#endif
2341}
2342
2343static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss)
2344{
2345 struct tcp_sock *tp = tcp_sk(sk);
2346
2347 if (unmark_loss) {
2348 struct sk_buff *skb;
2349
2350 skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
2351 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2352 }
2353 tp->lost_out = 0;
2354 tcp_clear_all_retrans_hints(tp);
2355 }
2356
2357 if (tp->prior_ssthresh) {
2358 const struct inet_connection_sock *icsk = inet_csk(sk);
2359
2360 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
2361
2362 if (tp->prior_ssthresh > tp->snd_ssthresh) {
2363 tp->snd_ssthresh = tp->prior_ssthresh;
2364 tcp_ecn_withdraw_cwr(tp);
2365 }
2366 }
2367 tp->snd_cwnd_stamp = tcp_jiffies32;
2368 tp->undo_marker = 0;
2369 tp->rack.advanced = 1; /* Force RACK to re-exam losses */
2370}
2371
2372static inline bool tcp_may_undo(const struct tcp_sock *tp)
2373{
2374 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
2375}
2376
2377/* People celebrate: "We love our President!" */
2378static bool tcp_try_undo_recovery(struct sock *sk)
2379{
2380 struct tcp_sock *tp = tcp_sk(sk);
2381
2382 if (tcp_may_undo(tp)) {
2383 int mib_idx;
2384
2385 /* Happy end! We did not retransmit anything
2386 * or our original transmission succeeded.
2387 */
2388 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
2389 tcp_undo_cwnd_reduction(sk, false);
2390 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
2391 mib_idx = LINUX_MIB_TCPLOSSUNDO;
2392 else
2393 mib_idx = LINUX_MIB_TCPFULLUNDO;
2394
2395 NET_INC_STATS(sock_net(sk), mib_idx);
2396 } else if (tp->rack.reo_wnd_persist) {
2397 tp->rack.reo_wnd_persist--;
2398 }
2399 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
2400 /* Hold old state until something *above* high_seq
2401 * is ACKed. For Reno it is MUST to prevent false
2402 * fast retransmits (RFC2582). SACK TCP is safe. */
2403 if (!tcp_any_retrans_done(sk))
2404 tp->retrans_stamp = 0;
2405 return true;
2406 }
2407 tcp_set_ca_state(sk, TCP_CA_Open);
2408 tp->is_sack_reneg = 0;
2409 return false;
2410}
2411
2412/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2413static bool tcp_try_undo_dsack(struct sock *sk)
2414{
2415 struct tcp_sock *tp = tcp_sk(sk);
2416
2417 if (tp->undo_marker && !tp->undo_retrans) {
2418 tp->rack.reo_wnd_persist = min(TCP_RACK_RECOVERY_THRESH,
2419 tp->rack.reo_wnd_persist + 1);
2420 DBGUNDO(sk, "D-SACK");
2421 tcp_undo_cwnd_reduction(sk, false);
2422 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
2423 return true;
2424 }
2425 return false;
2426}
2427
2428/* Undo during loss recovery after partial ACK or using F-RTO. */
2429static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo)
2430{
2431 struct tcp_sock *tp = tcp_sk(sk);
2432
2433 if (frto_undo || tcp_may_undo(tp)) {
2434 tcp_undo_cwnd_reduction(sk, true);
2435
2436 DBGUNDO(sk, "partial loss");
2437 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
2438 if (frto_undo)
2439 NET_INC_STATS(sock_net(sk),
2440 LINUX_MIB_TCPSPURIOUSRTOS);
2441 inet_csk(sk)->icsk_retransmits = 0;
2442 if (frto_undo || tcp_is_sack(tp)) {
2443 tcp_set_ca_state(sk, TCP_CA_Open);
2444 tp->is_sack_reneg = 0;
2445 }
2446 return true;
2447 }
2448 return false;
2449}
2450
2451/* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2452 * It computes the number of packets to send (sndcnt) based on packets newly
2453 * delivered:
2454 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2455 * cwnd reductions across a full RTT.
2456 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2457 * But when the retransmits are acked without further losses, PRR
2458 * slow starts cwnd up to ssthresh to speed up the recovery.
2459 */
2460static void tcp_init_cwnd_reduction(struct sock *sk)
2461{
2462 struct tcp_sock *tp = tcp_sk(sk);
2463
2464 tp->high_seq = tp->snd_nxt;
2465 tp->tlp_high_seq = 0;
2466 tp->snd_cwnd_cnt = 0;
2467 tp->prior_cwnd = tp->snd_cwnd;
2468 tp->prr_delivered = 0;
2469 tp->prr_out = 0;
2470 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
2471 tcp_ecn_queue_cwr(tp);
2472}
2473
2474void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int flag)
2475{
2476 struct tcp_sock *tp = tcp_sk(sk);
2477 int sndcnt = 0;
2478 int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp);
2479
2480 if (newly_acked_sacked <= 0 || WARN_ON_ONCE(!tp->prior_cwnd))
2481 return;
2482
2483 tp->prr_delivered += newly_acked_sacked;
2484 if (delta < 0) {
2485 u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +
2486 tp->prior_cwnd - 1;
2487 sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out;
2488 } else if ((flag & (FLAG_RETRANS_DATA_ACKED | FLAG_LOST_RETRANS)) ==
2489 FLAG_RETRANS_DATA_ACKED) {
2490 sndcnt = min_t(int, delta,
2491 max_t(int, tp->prr_delivered - tp->prr_out,
2492 newly_acked_sacked) + 1);
2493 } else {
2494 sndcnt = min(delta, newly_acked_sacked);
2495 }
2496 /* Force a fast retransmit upon entering fast recovery */
2497 sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1));
2498 tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
2499}
2500
2501static inline void tcp_end_cwnd_reduction(struct sock *sk)
2502{
2503 struct tcp_sock *tp = tcp_sk(sk);
2504
2505 if (inet_csk(sk)->icsk_ca_ops->cong_control)
2506 return;
2507
2508 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2509 if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH &&
2510 (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR || tp->undo_marker)) {
2511 tp->snd_cwnd = tp->snd_ssthresh;
2512 tp->snd_cwnd_stamp = tcp_jiffies32;
2513 }
2514 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
2515}
2516
2517/* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2518void tcp_enter_cwr(struct sock *sk)
2519{
2520 struct tcp_sock *tp = tcp_sk(sk);
2521
2522 tp->prior_ssthresh = 0;
2523 if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
2524 tp->undo_marker = 0;
2525 tcp_init_cwnd_reduction(sk);
2526 tcp_set_ca_state(sk, TCP_CA_CWR);
2527 }
2528}
2529EXPORT_SYMBOL(tcp_enter_cwr);
2530
2531static void tcp_try_keep_open(struct sock *sk)
2532{
2533 struct tcp_sock *tp = tcp_sk(sk);
2534 int state = TCP_CA_Open;
2535
2536 if (tcp_left_out(tp) || tcp_any_retrans_done(sk))
2537 state = TCP_CA_Disorder;
2538
2539 if (inet_csk(sk)->icsk_ca_state != state) {
2540 tcp_set_ca_state(sk, state);
2541 tp->high_seq = tp->snd_nxt;
2542 }
2543}
2544
2545static void tcp_try_to_open(struct sock *sk, int flag)
2546{
2547 struct tcp_sock *tp = tcp_sk(sk);
2548
2549 tcp_verify_left_out(tp);
2550
2551 if (!tcp_any_retrans_done(sk))
2552 tp->retrans_stamp = 0;
2553
2554 if (flag & FLAG_ECE)
2555 tcp_enter_cwr(sk);
2556
2557 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
2558 tcp_try_keep_open(sk);
2559 }
2560}
2561
2562static void tcp_mtup_probe_failed(struct sock *sk)
2563{
2564 struct inet_connection_sock *icsk = inet_csk(sk);
2565
2566 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
2567 icsk->icsk_mtup.probe_size = 0;
2568 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMTUPFAIL);
2569}
2570
2571static void tcp_mtup_probe_success(struct sock *sk)
2572{
2573 struct tcp_sock *tp = tcp_sk(sk);
2574 struct inet_connection_sock *icsk = inet_csk(sk);
2575
2576 /* FIXME: breaks with very large cwnd */
2577 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2578 tp->snd_cwnd = tp->snd_cwnd *
2579 tcp_mss_to_mtu(sk, tp->mss_cache) /
2580 icsk->icsk_mtup.probe_size;
2581 tp->snd_cwnd_cnt = 0;
2582 tp->snd_cwnd_stamp = tcp_jiffies32;
2583 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2584
2585 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
2586 icsk->icsk_mtup.probe_size = 0;
2587 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
2588 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMTUPSUCCESS);
2589}
2590
2591/* Do a simple retransmit without using the backoff mechanisms in
2592 * tcp_timer. This is used for path mtu discovery.
2593 * The socket is already locked here.
2594 */
2595void tcp_simple_retransmit(struct sock *sk)
2596{
2597 const struct inet_connection_sock *icsk = inet_csk(sk);
2598 struct tcp_sock *tp = tcp_sk(sk);
2599 struct sk_buff *skb;
2600 unsigned int mss = tcp_current_mss(sk);
2601
2602 skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
2603 if (tcp_skb_seglen(skb) > mss &&
2604 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
2605 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2606 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2607 tp->retrans_out -= tcp_skb_pcount(skb);
2608 }
2609 tcp_skb_mark_lost_uncond_verify(tp, skb);
2610 }
2611 }
2612
2613 tcp_clear_retrans_hints_partial(tp);
2614
2615 if (!tp->lost_out)
2616 return;
2617
2618 if (tcp_is_reno(tp))
2619 tcp_limit_reno_sacked(tp);
2620
2621 tcp_verify_left_out(tp);
2622
2623 /* Don't muck with the congestion window here.
2624 * Reason is that we do not increase amount of _data_
2625 * in network, but units changed and effective
2626 * cwnd/ssthresh really reduced now.
2627 */
2628 if (icsk->icsk_ca_state != TCP_CA_Loss) {
2629 tp->high_seq = tp->snd_nxt;
2630 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2631 tp->prior_ssthresh = 0;
2632 tp->undo_marker = 0;
2633 tcp_set_ca_state(sk, TCP_CA_Loss);
2634 }
2635 tcp_xmit_retransmit_queue(sk);
2636}
2637EXPORT_SYMBOL(tcp_simple_retransmit);
2638
2639void tcp_enter_recovery(struct sock *sk, bool ece_ack)
2640{
2641 struct tcp_sock *tp = tcp_sk(sk);
2642 int mib_idx;
2643
2644 if (tcp_is_reno(tp))
2645 mib_idx = LINUX_MIB_TCPRENORECOVERY;
2646 else
2647 mib_idx = LINUX_MIB_TCPSACKRECOVERY;
2648
2649 NET_INC_STATS(sock_net(sk), mib_idx);
2650
2651 tp->prior_ssthresh = 0;
2652 tcp_init_undo(tp);
2653
2654 if (!tcp_in_cwnd_reduction(sk)) {
2655 if (!ece_ack)
2656 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2657 tcp_init_cwnd_reduction(sk);
2658 }
2659 tcp_set_ca_state(sk, TCP_CA_Recovery);
2660}
2661
2662/* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2663 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2664 */
2665static void tcp_process_loss(struct sock *sk, int flag, int num_dupack,
2666 int *rexmit)
2667{
2668 struct tcp_sock *tp = tcp_sk(sk);
2669 bool recovered = !before(tp->snd_una, tp->high_seq);
2670
2671 if ((flag & FLAG_SND_UNA_ADVANCED || rcu_access_pointer(tp->fastopen_rsk)) &&
2672 tcp_try_undo_loss(sk, false))
2673 return;
2674
2675 if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2676 /* Step 3.b. A timeout is spurious if not all data are
2677 * lost, i.e., never-retransmitted data are (s)acked.
2678 */
2679 if ((flag & FLAG_ORIG_SACK_ACKED) &&
2680 tcp_try_undo_loss(sk, true))
2681 return;
2682
2683 if (after(tp->snd_nxt, tp->high_seq)) {
2684 if (flag & FLAG_DATA_SACKED || num_dupack)
2685 tp->frto = 0; /* Step 3.a. loss was real */
2686 } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
2687 tp->high_seq = tp->snd_nxt;
2688 /* Step 2.b. Try send new data (but deferred until cwnd
2689 * is updated in tcp_ack()). Otherwise fall back to
2690 * the conventional recovery.
2691 */
2692 if (!tcp_write_queue_empty(sk) &&
2693 after(tcp_wnd_end(tp), tp->snd_nxt)) {
2694 *rexmit = REXMIT_NEW;
2695 return;
2696 }
2697 tp->frto = 0;
2698 }
2699 }
2700
2701 if (recovered) {
2702 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2703 tcp_try_undo_recovery(sk);
2704 return;
2705 }
2706 if (tcp_is_reno(tp)) {
2707 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2708 * delivered. Lower inflight to clock out (re)tranmissions.
2709 */
2710 if (after(tp->snd_nxt, tp->high_seq) && num_dupack)
2711 tcp_add_reno_sack(sk, num_dupack);
2712 else if (flag & FLAG_SND_UNA_ADVANCED)
2713 tcp_reset_reno_sack(tp);
2714 }
2715 *rexmit = REXMIT_LOST;
2716}
2717
2718/* Undo during fast recovery after partial ACK. */
2719static bool tcp_try_undo_partial(struct sock *sk, u32 prior_snd_una)
2720{
2721 struct tcp_sock *tp = tcp_sk(sk);
2722
2723 if (tp->undo_marker && tcp_packet_delayed(tp)) {
2724 /* Plain luck! Hole if filled with delayed
2725 * packet, rather than with a retransmit. Check reordering.
2726 */
2727 tcp_check_sack_reordering(sk, prior_snd_una, 1);
2728
2729 /* We are getting evidence that the reordering degree is higher
2730 * than we realized. If there are no retransmits out then we
2731 * can undo. Otherwise we clock out new packets but do not
2732 * mark more packets lost or retransmit more.
2733 */
2734 if (tp->retrans_out)
2735 return true;
2736
2737 if (!tcp_any_retrans_done(sk))
2738 tp->retrans_stamp = 0;
2739
2740 DBGUNDO(sk, "partial recovery");
2741 tcp_undo_cwnd_reduction(sk, true);
2742 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
2743 tcp_try_keep_open(sk);
2744 return true;
2745 }
2746 return false;
2747}
2748
2749static void tcp_identify_packet_loss(struct sock *sk, int *ack_flag)
2750{
2751 struct tcp_sock *tp = tcp_sk(sk);
2752
2753 if (tcp_rtx_queue_empty(sk))
2754 return;
2755
2756 if (unlikely(tcp_is_reno(tp))) {
2757 tcp_newreno_mark_lost(sk, *ack_flag & FLAG_SND_UNA_ADVANCED);
2758 } else if (tcp_is_rack(sk)) {
2759 u32 prior_retrans = tp->retrans_out;
2760
2761 tcp_rack_mark_lost(sk);
2762 if (prior_retrans > tp->retrans_out)
2763 *ack_flag |= FLAG_LOST_RETRANS;
2764 }
2765}
2766
2767static bool tcp_force_fast_retransmit(struct sock *sk)
2768{
2769 struct tcp_sock *tp = tcp_sk(sk);
2770
2771 return after(tcp_highest_sack_seq(tp),
2772 tp->snd_una + tp->reordering * tp->mss_cache);
2773}
2774
2775/* Process an event, which can update packets-in-flight not trivially.
2776 * Main goal of this function is to calculate new estimate for left_out,
2777 * taking into account both packets sitting in receiver's buffer and
2778 * packets lost by network.
2779 *
2780 * Besides that it updates the congestion state when packet loss or ECN
2781 * is detected. But it does not reduce the cwnd, it is done by the
2782 * congestion control later.
2783 *
2784 * It does _not_ decide what to send, it is made in function
2785 * tcp_xmit_retransmit_queue().
2786 */
2787static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
2788 int num_dupack, int *ack_flag, int *rexmit)
2789{
2790 struct inet_connection_sock *icsk = inet_csk(sk);
2791 struct tcp_sock *tp = tcp_sk(sk);
2792 int fast_rexmit = 0, flag = *ack_flag;
2793 bool do_lost = num_dupack || ((flag & FLAG_DATA_SACKED) &&
2794 tcp_force_fast_retransmit(sk));
2795
2796 if (!tp->packets_out && tp->sacked_out)
2797 tp->sacked_out = 0;
2798
2799 /* Now state machine starts.
2800 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2801 if (flag & FLAG_ECE)
2802 tp->prior_ssthresh = 0;
2803
2804 /* B. In all the states check for reneging SACKs. */
2805 if (tcp_check_sack_reneging(sk, flag))
2806 return;
2807
2808 /* C. Check consistency of the current state. */
2809 tcp_verify_left_out(tp);
2810
2811 /* D. Check state exit conditions. State can be terminated
2812 * when high_seq is ACKed. */
2813 if (icsk->icsk_ca_state == TCP_CA_Open) {
2814 WARN_ON(tp->retrans_out != 0);
2815 tp->retrans_stamp = 0;
2816 } else if (!before(tp->snd_una, tp->high_seq)) {
2817 switch (icsk->icsk_ca_state) {
2818 case TCP_CA_CWR:
2819 /* CWR is to be held something *above* high_seq
2820 * is ACKed for CWR bit to reach receiver. */
2821 if (tp->snd_una != tp->high_seq) {
2822 tcp_end_cwnd_reduction(sk);
2823 tcp_set_ca_state(sk, TCP_CA_Open);
2824 }
2825 break;
2826
2827 case TCP_CA_Recovery:
2828 if (tcp_is_reno(tp))
2829 tcp_reset_reno_sack(tp);
2830 if (tcp_try_undo_recovery(sk))
2831 return;
2832 tcp_end_cwnd_reduction(sk);
2833 break;
2834 }
2835 }
2836
2837 /* E. Process state. */
2838 switch (icsk->icsk_ca_state) {
2839 case TCP_CA_Recovery:
2840 if (!(flag & FLAG_SND_UNA_ADVANCED)) {
2841 if (tcp_is_reno(tp))
2842 tcp_add_reno_sack(sk, num_dupack);
2843 } else {
2844 if (tcp_try_undo_partial(sk, prior_snd_una))
2845 return;
2846 /* Partial ACK arrived. Force fast retransmit. */
2847 do_lost = tcp_is_reno(tp) ||
2848 tcp_force_fast_retransmit(sk);
2849 }
2850 if (tcp_try_undo_dsack(sk)) {
2851 tcp_try_keep_open(sk);
2852 return;
2853 }
2854 tcp_identify_packet_loss(sk, ack_flag);
2855 break;
2856 case TCP_CA_Loss:
2857 tcp_process_loss(sk, flag, num_dupack, rexmit);
2858 tcp_identify_packet_loss(sk, ack_flag);
2859 if (!(icsk->icsk_ca_state == TCP_CA_Open ||
2860 (*ack_flag & FLAG_LOST_RETRANS)))
2861 return;
2862 /* Change state if cwnd is undone or retransmits are lost */
2863 /* fall through */
2864 default:
2865 if (tcp_is_reno(tp)) {
2866 if (flag & FLAG_SND_UNA_ADVANCED)
2867 tcp_reset_reno_sack(tp);
2868 tcp_add_reno_sack(sk, num_dupack);
2869 }
2870
2871 if (icsk->icsk_ca_state <= TCP_CA_Disorder)
2872 tcp_try_undo_dsack(sk);
2873
2874 tcp_identify_packet_loss(sk, ack_flag);
2875 if (!tcp_time_to_recover(sk, flag)) {
2876 tcp_try_to_open(sk, flag);
2877 return;
2878 }
2879
2880 /* MTU probe failure: don't reduce cwnd */
2881 if (icsk->icsk_ca_state < TCP_CA_CWR &&
2882 icsk->icsk_mtup.probe_size &&
2883 tp->snd_una == tp->mtu_probe.probe_seq_start) {
2884 tcp_mtup_probe_failed(sk);
2885 /* Restores the reduction we did in tcp_mtup_probe() */
2886 tp->snd_cwnd++;
2887 tcp_simple_retransmit(sk);
2888 return;
2889 }
2890
2891 /* Otherwise enter Recovery state */
2892 tcp_enter_recovery(sk, (flag & FLAG_ECE));
2893 fast_rexmit = 1;
2894 }
2895
2896 if (!tcp_is_rack(sk) && do_lost)
2897 tcp_update_scoreboard(sk, fast_rexmit);
2898 *rexmit = REXMIT_LOST;
2899}
2900
2901static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us, const int flag)
2902{
2903 u32 wlen = sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen * HZ;
2904 struct tcp_sock *tp = tcp_sk(sk);
2905
2906 if ((flag & FLAG_ACK_MAYBE_DELAYED) && rtt_us > tcp_min_rtt(tp)) {
2907 /* If the remote keeps returning delayed ACKs, eventually
2908 * the min filter would pick it up and overestimate the
2909 * prop. delay when it expires. Skip suspected delayed ACKs.
2910 */
2911 return;
2912 }
2913 minmax_running_min(&tp->rtt_min, wlen, tcp_jiffies32,
2914 rtt_us ? : jiffies_to_usecs(1));
2915}
2916
2917static bool tcp_ack_update_rtt(struct sock *sk, const int flag,
2918 long seq_rtt_us, long sack_rtt_us,
2919 long ca_rtt_us, struct rate_sample *rs)
2920{
2921 const struct tcp_sock *tp = tcp_sk(sk);
2922
2923 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2924 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2925 * Karn's algorithm forbids taking RTT if some retransmitted data
2926 * is acked (RFC6298).
2927 */
2928 if (seq_rtt_us < 0)
2929 seq_rtt_us = sack_rtt_us;
2930
2931 /* RTTM Rule: A TSecr value received in a segment is used to
2932 * update the averaged RTT measurement only if the segment
2933 * acknowledges some new data, i.e., only if it advances the
2934 * left edge of the send window.
2935 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2936 */
2937 if (seq_rtt_us < 0 && tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2938 flag & FLAG_ACKED) {
2939 u32 delta = tcp_time_stamp(tp) - tp->rx_opt.rcv_tsecr;
2940
2941 if (likely(delta < INT_MAX / (USEC_PER_SEC / TCP_TS_HZ))) {
2942 seq_rtt_us = delta * (USEC_PER_SEC / TCP_TS_HZ);
2943 ca_rtt_us = seq_rtt_us;
2944 }
2945 }
2946 rs->rtt_us = ca_rtt_us; /* RTT of last (S)ACKed packet (or -1) */
2947 if (seq_rtt_us < 0)
2948 return false;
2949
2950 /* ca_rtt_us >= 0 is counting on the invariant that ca_rtt_us is
2951 * always taken together with ACK, SACK, or TS-opts. Any negative
2952 * values will be skipped with the seq_rtt_us < 0 check above.
2953 */
2954 tcp_update_rtt_min(sk, ca_rtt_us, flag);
2955 tcp_rtt_estimator(sk, seq_rtt_us);
2956 tcp_set_rto(sk);
2957
2958 /* RFC6298: only reset backoff on valid RTT measurement. */
2959 inet_csk(sk)->icsk_backoff = 0;
2960 return true;
2961}
2962
2963/* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2964void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req)
2965{
2966 struct rate_sample rs;
2967 long rtt_us = -1L;
2968
2969 if (req && !req->num_retrans && tcp_rsk(req)->snt_synack)
2970 rtt_us = tcp_stamp_us_delta(tcp_clock_us(), tcp_rsk(req)->snt_synack);
2971
2972 tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, rtt_us, -1L, rtt_us, &rs);
2973}
2974
2975
2976static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
2977{
2978 const struct inet_connection_sock *icsk = inet_csk(sk);
2979
2980 icsk->icsk_ca_ops->cong_avoid(sk, ack, acked);
2981 tcp_sk(sk)->snd_cwnd_stamp = tcp_jiffies32;
2982}
2983
2984/* Restart timer after forward progress on connection.
2985 * RFC2988 recommends to restart timer to now+rto.
2986 */
2987void tcp_rearm_rto(struct sock *sk)
2988{
2989 const struct inet_connection_sock *icsk = inet_csk(sk);
2990 struct tcp_sock *tp = tcp_sk(sk);
2991
2992 /* If the retrans timer is currently being used by Fast Open
2993 * for SYN-ACK retrans purpose, stay put.
2994 */
2995 if (rcu_access_pointer(tp->fastopen_rsk))
2996 return;
2997
2998 if (!tp->packets_out) {
2999 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
3000 } else {
3001 u32 rto = inet_csk(sk)->icsk_rto;
3002 /* Offset the time elapsed after installing regular RTO */
3003 if (icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT ||
3004 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
3005 s64 delta_us = tcp_rto_delta_us(sk);
3006 /* delta_us may not be positive if the socket is locked
3007 * when the retrans timer fires and is rescheduled.
3008 */
3009 rto = usecs_to_jiffies(max_t(int, delta_us, 1));
3010 }
3011 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
3012 TCP_RTO_MAX, tcp_rtx_queue_head(sk));
3013 }
3014}
3015
3016/* Try to schedule a loss probe; if that doesn't work, then schedule an RTO. */
3017static void tcp_set_xmit_timer(struct sock *sk)
3018{
3019 if (!tcp_schedule_loss_probe(sk, true))
3020 tcp_rearm_rto(sk);
3021}
3022
3023/* If we get here, the whole TSO packet has not been acked. */
3024static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
3025{
3026 struct tcp_sock *tp = tcp_sk(sk);
3027 u32 packets_acked;
3028
3029 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
3030
3031 packets_acked = tcp_skb_pcount(skb);
3032 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3033 return 0;
3034 packets_acked -= tcp_skb_pcount(skb);
3035
3036 if (packets_acked) {
3037 BUG_ON(tcp_skb_pcount(skb) == 0);
3038 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
3039 }
3040
3041 return packets_acked;
3042}
3043
3044static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
3045 u32 prior_snd_una)
3046{
3047 const struct skb_shared_info *shinfo;
3048
3049 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3050 if (likely(!TCP_SKB_CB(skb)->txstamp_ack))
3051 return;
3052
3053 shinfo = skb_shinfo(skb);
3054 if (!before(shinfo->tskey, prior_snd_una) &&
3055 before(shinfo->tskey, tcp_sk(sk)->snd_una)) {
3056 tcp_skb_tsorted_save(skb) {
3057 __skb_tstamp_tx(skb, NULL, sk, SCM_TSTAMP_ACK);
3058 } tcp_skb_tsorted_restore(skb);
3059 }
3060}
3061
3062/* Remove acknowledged frames from the retransmission queue. If our packet
3063 * is before the ack sequence we can discard it as it's confirmed to have
3064 * arrived at the other end.
3065 */
3066static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack,
3067 u32 prior_snd_una,
3068 struct tcp_sacktag_state *sack)
3069{
3070 const struct inet_connection_sock *icsk = inet_csk(sk);
3071 u64 first_ackt, last_ackt;
3072 struct tcp_sock *tp = tcp_sk(sk);
3073 u32 prior_sacked = tp->sacked_out;
3074 u32 reord = tp->snd_nxt; /* lowest acked un-retx un-sacked seq */
3075 struct sk_buff *skb, *next;
3076 bool fully_acked = true;
3077 long sack_rtt_us = -1L;
3078 long seq_rtt_us = -1L;
3079 long ca_rtt_us = -1L;
3080 u32 pkts_acked = 0;
3081 u32 last_in_flight = 0;
3082 bool rtt_update;
3083 int flag = 0;
3084
3085 first_ackt = 0;
3086
3087 for (skb = skb_rb_first(&sk->tcp_rtx_queue); skb; skb = next) {
3088 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
3089 const u32 start_seq = scb->seq;
3090 u8 sacked = scb->sacked;
3091 u32 acked_pcount;
3092
3093 tcp_ack_tstamp(sk, skb, prior_snd_una);
3094
3095 /* Determine how many packets and what bytes were acked, tso and else */
3096 if (after(scb->end_seq, tp->snd_una)) {
3097 if (tcp_skb_pcount(skb) == 1 ||
3098 !after(tp->snd_una, scb->seq))
3099 break;
3100
3101 acked_pcount = tcp_tso_acked(sk, skb);
3102 if (!acked_pcount)
3103 break;
3104 fully_acked = false;
3105 } else {
3106 acked_pcount = tcp_skb_pcount(skb);
3107 }
3108
3109 if (unlikely(sacked & TCPCB_RETRANS)) {
3110 if (sacked & TCPCB_SACKED_RETRANS)
3111 tp->retrans_out -= acked_pcount;
3112 flag |= FLAG_RETRANS_DATA_ACKED;
3113 } else if (!(sacked & TCPCB_SACKED_ACKED)) {
3114 last_ackt = tcp_skb_timestamp_us(skb);
3115 WARN_ON_ONCE(last_ackt == 0);
3116 if (!first_ackt)
3117 first_ackt = last_ackt;
3118
3119 last_in_flight = TCP_SKB_CB(skb)->tx.in_flight;
3120 if (before(start_seq, reord))
3121 reord = start_seq;
3122 if (!after(scb->end_seq, tp->high_seq))
3123 flag |= FLAG_ORIG_SACK_ACKED;
3124 }
3125
3126 if (sacked & TCPCB_SACKED_ACKED) {
3127 tp->sacked_out -= acked_pcount;
3128 } else if (tcp_is_sack(tp)) {
3129 tp->delivered += acked_pcount;
3130 if (!tcp_skb_spurious_retrans(tp, skb))
3131 tcp_rack_advance(tp, sacked, scb->end_seq,
3132 tcp_skb_timestamp_us(skb));
3133 }
3134 if (sacked & TCPCB_LOST)
3135 tp->lost_out -= acked_pcount;
3136
3137 tp->packets_out -= acked_pcount;
3138 pkts_acked += acked_pcount;
3139 tcp_rate_skb_delivered(sk, skb, sack->rate);
3140
3141 /* Initial outgoing SYN's get put onto the write_queue
3142 * just like anything else we transmit. It is not
3143 * true data, and if we misinform our callers that
3144 * this ACK acks real data, we will erroneously exit
3145 * connection startup slow start one packet too
3146 * quickly. This is severely frowned upon behavior.
3147 */
3148 if (likely(!(scb->tcp_flags & TCPHDR_SYN))) {
3149 flag |= FLAG_DATA_ACKED;
3150 } else {
3151 flag |= FLAG_SYN_ACKED;
3152 tp->retrans_stamp = 0;
3153 }
3154
3155 if (!fully_acked)
3156 break;
3157
3158 next = skb_rb_next(skb);
3159 if (unlikely(skb == tp->retransmit_skb_hint))
3160 tp->retransmit_skb_hint = NULL;
3161 if (unlikely(skb == tp->lost_skb_hint))
3162 tp->lost_skb_hint = NULL;
3163 tcp_rtx_queue_unlink_and_free(skb, sk);
3164 }
3165
3166 if (!skb)
3167 tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
3168
3169 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
3170 tp->snd_up = tp->snd_una;
3171
3172 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
3173 flag |= FLAG_SACK_RENEGING;
3174
3175 if (likely(first_ackt) && !(flag & FLAG_RETRANS_DATA_ACKED)) {
3176 seq_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, first_ackt);
3177 ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, last_ackt);
3178
3179 if (pkts_acked == 1 && last_in_flight < tp->mss_cache &&
3180 last_in_flight && !prior_sacked && fully_acked &&
3181 sack->rate->prior_delivered + 1 == tp->delivered &&
3182 !(flag & (FLAG_CA_ALERT | FLAG_SYN_ACKED))) {
3183 /* Conservatively mark a delayed ACK. It's typically
3184 * from a lone runt packet over the round trip to
3185 * a receiver w/o out-of-order or CE events.
3186 */
3187 flag |= FLAG_ACK_MAYBE_DELAYED;
3188 }
3189 }
3190 if (sack->first_sackt) {
3191 sack_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, sack->first_sackt);
3192 ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, sack->last_sackt);
3193 }
3194 rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt_us, sack_rtt_us,
3195 ca_rtt_us, sack->rate);
3196
3197 if (flag & FLAG_ACKED) {
3198 flag |= FLAG_SET_XMIT_TIMER; /* set TLP or RTO timer */
3199 if (unlikely(icsk->icsk_mtup.probe_size &&
3200 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
3201 tcp_mtup_probe_success(sk);
3202 }
3203
3204 if (tcp_is_reno(tp)) {
3205 tcp_remove_reno_sacks(sk, pkts_acked);
3206
3207 /* If any of the cumulatively ACKed segments was
3208 * retransmitted, non-SACK case cannot confirm that
3209 * progress was due to original transmission due to
3210 * lack of TCPCB_SACKED_ACKED bits even if some of
3211 * the packets may have been never retransmitted.
3212 */
3213 if (flag & FLAG_RETRANS_DATA_ACKED)
3214 flag &= ~FLAG_ORIG_SACK_ACKED;
3215 } else {
3216 int delta;
3217
3218 /* Non-retransmitted hole got filled? That's reordering */
3219 if (before(reord, prior_fack))
3220 tcp_check_sack_reordering(sk, reord, 0);
3221
3222 delta = prior_sacked - tp->sacked_out;
3223 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
3224 }
3225 } else if (skb && rtt_update && sack_rtt_us >= 0 &&
3226 sack_rtt_us > tcp_stamp_us_delta(tp->tcp_mstamp,
3227 tcp_skb_timestamp_us(skb))) {
3228 /* Do not re-arm RTO if the sack RTT is measured from data sent
3229 * after when the head was last (re)transmitted. Otherwise the
3230 * timeout may continue to extend in loss recovery.
3231 */
3232 flag |= FLAG_SET_XMIT_TIMER; /* set TLP or RTO timer */
3233 }
3234
3235 if (icsk->icsk_ca_ops->pkts_acked) {
3236 struct ack_sample sample = { .pkts_acked = pkts_acked,
3237 .rtt_us = sack->rate->rtt_us,
3238 .in_flight = last_in_flight };
3239
3240 icsk->icsk_ca_ops->pkts_acked(sk, &sample);
3241 }
3242
3243#if FASTRETRANS_DEBUG > 0
3244 WARN_ON((int)tp->sacked_out < 0);
3245 WARN_ON((int)tp->lost_out < 0);
3246 WARN_ON((int)tp->retrans_out < 0);
3247 if (!tp->packets_out && tcp_is_sack(tp)) {
3248 icsk = inet_csk(sk);
3249 if (tp->lost_out) {
3250 pr_debug("Leak l=%u %d\n",
3251 tp->lost_out, icsk->icsk_ca_state);
3252 tp->lost_out = 0;
3253 }
3254 if (tp->sacked_out) {
3255 pr_debug("Leak s=%u %d\n",
3256 tp->sacked_out, icsk->icsk_ca_state);
3257 tp->sacked_out = 0;
3258 }
3259 if (tp->retrans_out) {
3260 pr_debug("Leak r=%u %d\n",
3261 tp->retrans_out, icsk->icsk_ca_state);
3262 tp->retrans_out = 0;
3263 }
3264 }
3265#endif
3266 return flag;
3267}
3268
3269static void tcp_ack_probe(struct sock *sk)
3270{
3271 struct inet_connection_sock *icsk = inet_csk(sk);
3272 struct sk_buff *head = tcp_send_head(sk);
3273 const struct tcp_sock *tp = tcp_sk(sk);
3274
3275 /* Was it a usable window open? */
3276 if (!head)
3277 return;
3278 if (!after(TCP_SKB_CB(head)->end_seq, tcp_wnd_end(tp))) {
3279 icsk->icsk_backoff = 0;
3280 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
3281 /* Socket must be waked up by subsequent tcp_data_snd_check().
3282 * This function is not for random using!
3283 */
3284 } else {
3285 unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX);
3286
3287 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3288 when, TCP_RTO_MAX, NULL);
3289 }
3290}
3291
3292static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag)
3293{
3294 return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
3295 inet_csk(sk)->icsk_ca_state != TCP_CA_Open;
3296}
3297
3298/* Decide wheather to run the increase function of congestion control. */
3299static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
3300{
3301 /* If reordering is high then always grow cwnd whenever data is
3302 * delivered regardless of its ordering. Otherwise stay conservative
3303 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3304 * new SACK or ECE mark may first advance cwnd here and later reduce
3305 * cwnd in tcp_fastretrans_alert() based on more states.
3306 */
3307 if (tcp_sk(sk)->reordering > sock_net(sk)->ipv4.sysctl_tcp_reordering)
3308 return flag & FLAG_FORWARD_PROGRESS;
3309
3310 return flag & FLAG_DATA_ACKED;
3311}
3312
3313/* The "ultimate" congestion control function that aims to replace the rigid
3314 * cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction).
3315 * It's called toward the end of processing an ACK with precise rate
3316 * information. All transmission or retransmission are delayed afterwards.
3317 */
3318static void tcp_cong_control(struct sock *sk, u32 ack, u32 acked_sacked,
3319 int flag, const struct rate_sample *rs)
3320{
3321 const struct inet_connection_sock *icsk = inet_csk(sk);
3322
3323 if (icsk->icsk_ca_ops->cong_control) {
3324 icsk->icsk_ca_ops->cong_control(sk, rs);
3325 return;
3326 }
3327
3328 if (tcp_in_cwnd_reduction(sk)) {
3329 /* Reduce cwnd if state mandates */
3330 tcp_cwnd_reduction(sk, acked_sacked, flag);
3331 } else if (tcp_may_raise_cwnd(sk, flag)) {
3332 /* Advance cwnd if state allows */
3333 tcp_cong_avoid(sk, ack, acked_sacked);
3334 }
3335 tcp_update_pacing_rate(sk);
3336}
3337
3338/* Check that window update is acceptable.
3339 * The function assumes that snd_una<=ack<=snd_next.
3340 */
3341static inline bool tcp_may_update_window(const struct tcp_sock *tp,
3342 const u32 ack, const u32 ack_seq,
3343 const u32 nwin)
3344{
3345 return after(ack, tp->snd_una) ||
3346 after(ack_seq, tp->snd_wl1) ||
3347 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd);
3348}
3349
3350/* If we update tp->snd_una, also update tp->bytes_acked */
3351static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
3352{
3353 u32 delta = ack - tp->snd_una;
3354
3355 sock_owned_by_me((struct sock *)tp);
3356 tp->bytes_acked += delta;
3357 tp->snd_una = ack;
3358}
3359
3360/* If we update tp->rcv_nxt, also update tp->bytes_received */
3361static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
3362{
3363 u32 delta = seq - tp->rcv_nxt;
3364
3365 sock_owned_by_me((struct sock *)tp);
3366 tp->bytes_received += delta;
3367 WRITE_ONCE(tp->rcv_nxt, seq);
3368}
3369
3370/* Update our send window.
3371 *
3372 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3373 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3374 */
3375static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack,
3376 u32 ack_seq)
3377{
3378 struct tcp_sock *tp = tcp_sk(sk);
3379 int flag = 0;
3380 u32 nwin = ntohs(tcp_hdr(skb)->window);
3381
3382 if (likely(!tcp_hdr(skb)->syn))
3383 nwin <<= tp->rx_opt.snd_wscale;
3384
3385 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
3386 flag |= FLAG_WIN_UPDATE;
3387 tcp_update_wl(tp, ack_seq);
3388
3389 if (tp->snd_wnd != nwin) {
3390 tp->snd_wnd = nwin;
3391
3392 /* Note, it is the only place, where
3393 * fast path is recovered for sending TCP.
3394 */
3395 tp->pred_flags = 0;
3396 tcp_fast_path_check(sk);
3397
3398 if (!tcp_write_queue_empty(sk))
3399 tcp_slow_start_after_idle_check(sk);
3400
3401 if (nwin > tp->max_window) {
3402 tp->max_window = nwin;
3403 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
3404 }
3405 }
3406 }
3407
3408 tcp_snd_una_update(tp, ack);
3409
3410 return flag;
3411}
3412
3413static bool __tcp_oow_rate_limited(struct net *net, int mib_idx,
3414 u32 *last_oow_ack_time)
3415{
3416 if (*last_oow_ack_time) {
3417 s32 elapsed = (s32)(tcp_jiffies32 - *last_oow_ack_time);
3418
3419 if (0 <= elapsed && elapsed < net->ipv4.sysctl_tcp_invalid_ratelimit) {
3420 NET_INC_STATS(net, mib_idx);
3421 return true; /* rate-limited: don't send yet! */
3422 }
3423 }
3424
3425 *last_oow_ack_time = tcp_jiffies32;
3426
3427 return false; /* not rate-limited: go ahead, send dupack now! */
3428}
3429
3430/* Return true if we're currently rate-limiting out-of-window ACKs and
3431 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3432 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3433 * attacks that send repeated SYNs or ACKs for the same connection. To
3434 * do this, we do not send a duplicate SYNACK or ACK if the remote
3435 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3436 */
3437bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
3438 int mib_idx, u32 *last_oow_ack_time)
3439{
3440 /* Data packets without SYNs are not likely part of an ACK loop. */
3441 if ((TCP_SKB_CB(skb)->seq != TCP_SKB_CB(skb)->end_seq) &&
3442 !tcp_hdr(skb)->syn)
3443 return false;
3444
3445 return __tcp_oow_rate_limited(net, mib_idx, last_oow_ack_time);
3446}
3447
3448/* RFC 5961 7 [ACK Throttling] */
3449static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
3450{
3451 /* unprotected vars, we dont care of overwrites */
3452 static u32 challenge_timestamp;
3453 static unsigned int challenge_count;
3454 struct tcp_sock *tp = tcp_sk(sk);
3455 struct net *net = sock_net(sk);
3456 u32 count, now;
3457
3458 /* First check our per-socket dupack rate limit. */
3459 if (__tcp_oow_rate_limited(net,
3460 LINUX_MIB_TCPACKSKIPPEDCHALLENGE,
3461 &tp->last_oow_ack_time))
3462 return;
3463
3464 /* Then check host-wide RFC 5961 rate limit. */
3465 now = jiffies / HZ;
3466 if (now != challenge_timestamp) {
3467 u32 ack_limit = net->ipv4.sysctl_tcp_challenge_ack_limit;
3468 u32 half = (ack_limit + 1) >> 1;
3469
3470 challenge_timestamp = now;
3471 WRITE_ONCE(challenge_count, half + prandom_u32_max(ack_limit));
3472 }
3473 count = READ_ONCE(challenge_count);
3474 if (count > 0) {
3475 WRITE_ONCE(challenge_count, count - 1);
3476 NET_INC_STATS(net, LINUX_MIB_TCPCHALLENGEACK);
3477 tcp_send_ack(sk);
3478 }
3479}
3480
3481static void tcp_store_ts_recent(struct tcp_sock *tp)
3482{
3483 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
3484 tp->rx_opt.ts_recent_stamp = ktime_get_seconds();
3485}
3486
3487static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3488{
3489 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3490 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3491 * extra check below makes sure this can only happen
3492 * for pure ACK frames. -DaveM
3493 *
3494 * Not only, also it occurs for expired timestamps.
3495 */
3496
3497 if (tcp_paws_check(&tp->rx_opt, 0))
3498 tcp_store_ts_recent(tp);
3499 }
3500}
3501
3502/* This routine deals with acks during a TLP episode.
3503 * We mark the end of a TLP episode on receiving TLP dupack or when
3504 * ack is after tlp_high_seq.
3505 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3506 */
3507static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag)
3508{
3509 struct tcp_sock *tp = tcp_sk(sk);
3510
3511 if (before(ack, tp->tlp_high_seq))
3512 return;
3513
3514 if (flag & FLAG_DSACKING_ACK) {
3515 /* This DSACK means original and TLP probe arrived; no loss */
3516 tp->tlp_high_seq = 0;
3517 } else if (after(ack, tp->tlp_high_seq)) {
3518 /* ACK advances: there was a loss, so reduce cwnd. Reset
3519 * tlp_high_seq in tcp_init_cwnd_reduction()
3520 */
3521 tcp_init_cwnd_reduction(sk);
3522 tcp_set_ca_state(sk, TCP_CA_CWR);
3523 tcp_end_cwnd_reduction(sk);
3524 tcp_try_keep_open(sk);
3525 NET_INC_STATS(sock_net(sk),
3526 LINUX_MIB_TCPLOSSPROBERECOVERY);
3527 } else if (!(flag & (FLAG_SND_UNA_ADVANCED |
3528 FLAG_NOT_DUP | FLAG_DATA_SACKED))) {
3529 /* Pure dupack: original and TLP probe arrived; no loss */
3530 tp->tlp_high_seq = 0;
3531 }
3532}
3533
3534static inline void tcp_in_ack_event(struct sock *sk, u32 flags)
3535{
3536 const struct inet_connection_sock *icsk = inet_csk(sk);
3537
3538 if (icsk->icsk_ca_ops->in_ack_event)
3539 icsk->icsk_ca_ops->in_ack_event(sk, flags);
3540}
3541
3542/* Congestion control has updated the cwnd already. So if we're in
3543 * loss recovery then now we do any new sends (for FRTO) or
3544 * retransmits (for CA_Loss or CA_recovery) that make sense.
3545 */
3546static void tcp_xmit_recovery(struct sock *sk, int rexmit)
3547{
3548 struct tcp_sock *tp = tcp_sk(sk);
3549
3550 if (rexmit == REXMIT_NONE || sk->sk_state == TCP_SYN_SENT)
3551 return;
3552
3553 if (unlikely(rexmit == 2)) {
3554 __tcp_push_pending_frames(sk, tcp_current_mss(sk),
3555 TCP_NAGLE_OFF);
3556 if (after(tp->snd_nxt, tp->high_seq))
3557 return;
3558 tp->frto = 0;
3559 }
3560 tcp_xmit_retransmit_queue(sk);
3561}
3562
3563/* Returns the number of packets newly acked or sacked by the current ACK */
3564static u32 tcp_newly_delivered(struct sock *sk, u32 prior_delivered, int flag)
3565{
3566 const struct net *net = sock_net(sk);
3567 struct tcp_sock *tp = tcp_sk(sk);
3568 u32 delivered;
3569
3570 delivered = tp->delivered - prior_delivered;
3571 NET_ADD_STATS(net, LINUX_MIB_TCPDELIVERED, delivered);
3572 if (flag & FLAG_ECE) {
3573 tp->delivered_ce += delivered;
3574 NET_ADD_STATS(net, LINUX_MIB_TCPDELIVEREDCE, delivered);
3575 }
3576 return delivered;
3577}
3578
3579/* This routine deals with incoming acks, but not outgoing ones. */
3580static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
3581{
3582 struct inet_connection_sock *icsk = inet_csk(sk);
3583 struct tcp_sock *tp = tcp_sk(sk);
3584 struct tcp_sacktag_state sack_state;
3585 struct rate_sample rs = { .prior_delivered = 0 };
3586 u32 prior_snd_una = tp->snd_una;
3587 bool is_sack_reneg = tp->is_sack_reneg;
3588 u32 ack_seq = TCP_SKB_CB(skb)->seq;
3589 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3590 int num_dupack = 0;
3591 int prior_packets = tp->packets_out;
3592 u32 delivered = tp->delivered;
3593 u32 lost = tp->lost;
3594 int rexmit = REXMIT_NONE; /* Flag to (re)transmit to recover losses */
3595 u32 prior_fack;
3596
3597 sack_state.first_sackt = 0;
3598 sack_state.rate = &rs;
3599
3600 /* We very likely will need to access rtx queue. */
3601 prefetch(sk->tcp_rtx_queue.rb_node);
3602
3603 /* If the ack is older than previous acks
3604 * then we can probably ignore it.
3605 */
3606 if (before(ack, prior_snd_una)) {
3607 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3608 if (before(ack, prior_snd_una - tp->max_window)) {
3609 if (!(flag & FLAG_NO_CHALLENGE_ACK))
3610 tcp_send_challenge_ack(sk, skb);
3611 return -1;
3612 }
3613 goto old_ack;
3614 }
3615
3616 /* If the ack includes data we haven't sent yet, discard
3617 * this segment (RFC793 Section 3.9).
3618 */
3619 if (after(ack, tp->snd_nxt))
3620 return -1;
3621
3622 if (after(ack, prior_snd_una)) {
3623 flag |= FLAG_SND_UNA_ADVANCED;
3624 icsk->icsk_retransmits = 0;
3625
3626#if IS_ENABLED(CONFIG_TLS_DEVICE)
3627 if (static_branch_unlikely(&clean_acked_data_enabled.key))
3628 if (icsk->icsk_clean_acked)
3629 icsk->icsk_clean_acked(sk, ack);
3630#endif
3631 }
3632
3633 prior_fack = tcp_is_sack(tp) ? tcp_highest_sack_seq(tp) : tp->snd_una;
3634 rs.prior_in_flight = tcp_packets_in_flight(tp);
3635
3636 /* ts_recent update must be made after we are sure that the packet
3637 * is in window.
3638 */
3639 if (flag & FLAG_UPDATE_TS_RECENT)
3640 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
3641
3642 if ((flag & (FLAG_SLOWPATH | FLAG_SND_UNA_ADVANCED)) ==
3643 FLAG_SND_UNA_ADVANCED) {
3644 /* Window is constant, pure forward advance.
3645 * No more checks are required.
3646 * Note, we use the fact that SND.UNA>=SND.WL2.
3647 */
3648 tcp_update_wl(tp, ack_seq);
3649 tcp_snd_una_update(tp, ack);
3650 flag |= FLAG_WIN_UPDATE;
3651
3652 tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE);
3653
3654 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPACKS);
3655 } else {
3656 u32 ack_ev_flags = CA_ACK_SLOWPATH;
3657
3658 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
3659 flag |= FLAG_DATA;
3660 else
3661 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPUREACKS);
3662
3663 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
3664
3665 if (TCP_SKB_CB(skb)->sacked)
3666 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
3667 &sack_state);
3668
3669 if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) {
3670 flag |= FLAG_ECE;
3671 ack_ev_flags |= CA_ACK_ECE;
3672 }
3673
3674 if (flag & FLAG_WIN_UPDATE)
3675 ack_ev_flags |= CA_ACK_WIN_UPDATE;
3676
3677 tcp_in_ack_event(sk, ack_ev_flags);
3678 }
3679
3680 /* We passed data and got it acked, remove any soft error
3681 * log. Something worked...
3682 */
3683 sk->sk_err_soft = 0;
3684 icsk->icsk_probes_out = 0;
3685 tp->rcv_tstamp = tcp_jiffies32;
3686 if (!prior_packets)
3687 goto no_queue;
3688
3689 /* See if we can take anything off of the retransmit queue. */
3690 flag |= tcp_clean_rtx_queue(sk, prior_fack, prior_snd_una, &sack_state);
3691
3692 tcp_rack_update_reo_wnd(sk, &rs);
3693
3694 if (tp->tlp_high_seq)
3695 tcp_process_tlp_ack(sk, ack, flag);
3696 /* If needed, reset TLP/RTO timer; RACK may later override this. */
3697 if (flag & FLAG_SET_XMIT_TIMER)
3698 tcp_set_xmit_timer(sk);
3699
3700 if (tcp_ack_is_dubious(sk, flag)) {
3701 if (!(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP))) {
3702 num_dupack = 1;
3703 /* Consider if pure acks were aggregated in tcp_add_backlog() */
3704 if (!(flag & FLAG_DATA))
3705 num_dupack = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
3706 }
3707 tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
3708 &rexmit);
3709 }
3710
3711 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
3712 sk_dst_confirm(sk);
3713
3714 delivered = tcp_newly_delivered(sk, delivered, flag);
3715 lost = tp->lost - lost; /* freshly marked lost */
3716 rs.is_ack_delayed = !!(flag & FLAG_ACK_MAYBE_DELAYED);
3717 tcp_rate_gen(sk, delivered, lost, is_sack_reneg, sack_state.rate);
3718 tcp_cong_control(sk, ack, delivered, flag, sack_state.rate);
3719 tcp_xmit_recovery(sk, rexmit);
3720 return 1;
3721
3722no_queue:
3723 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3724 if (flag & FLAG_DSACKING_ACK) {
3725 tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
3726 &rexmit);
3727 tcp_newly_delivered(sk, delivered, flag);
3728 }
3729 /* If this ack opens up a zero window, clear backoff. It was
3730 * being used to time the probes, and is probably far higher than
3731 * it needs to be for normal retransmission.
3732 */
3733 tcp_ack_probe(sk);
3734
3735 if (tp->tlp_high_seq)
3736 tcp_process_tlp_ack(sk, ack, flag);
3737 return 1;
3738
3739old_ack:
3740 /* If data was SACKed, tag it and see if we should send more data.
3741 * If data was DSACKed, see if we can undo a cwnd reduction.
3742 */
3743 if (TCP_SKB_CB(skb)->sacked) {
3744 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
3745 &sack_state);
3746 tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
3747 &rexmit);
3748 tcp_newly_delivered(sk, delivered, flag);
3749 tcp_xmit_recovery(sk, rexmit);
3750 }
3751
3752 return 0;
3753}
3754
3755static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
3756 bool syn, struct tcp_fastopen_cookie *foc,
3757 bool exp_opt)
3758{
3759 /* Valid only in SYN or SYN-ACK with an even length. */
3760 if (!foc || !syn || len < 0 || (len & 1))
3761 return;
3762
3763 if (len >= TCP_FASTOPEN_COOKIE_MIN &&
3764 len <= TCP_FASTOPEN_COOKIE_MAX)
3765 memcpy(foc->val, cookie, len);
3766 else if (len != 0)
3767 len = -1;
3768 foc->len = len;
3769 foc->exp = exp_opt;
3770}
3771
3772static void smc_parse_options(const struct tcphdr *th,
3773 struct tcp_options_received *opt_rx,
3774 const unsigned char *ptr,
3775 int opsize)
3776{
3777#if IS_ENABLED(CONFIG_SMC)
3778 if (static_branch_unlikely(&tcp_have_smc)) {
3779 if (th->syn && !(opsize & 1) &&
3780 opsize >= TCPOLEN_EXP_SMC_BASE &&
3781 get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC)
3782 opt_rx->smc_ok = 1;
3783 }
3784#endif
3785}
3786
3787/* Try to parse the MSS option from the TCP header. Return 0 on failure, clamped
3788 * value on success.
3789 */
3790static u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss)
3791{
3792 const unsigned char *ptr = (const unsigned char *)(th + 1);
3793 int length = (th->doff * 4) - sizeof(struct tcphdr);
3794 u16 mss = 0;
3795
3796 while (length > 0) {
3797 int opcode = *ptr++;
3798 int opsize;
3799
3800 switch (opcode) {
3801 case TCPOPT_EOL:
3802 return mss;
3803 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3804 length--;
3805 continue;
3806 default:
3807 if (length < 2)
3808 return mss;
3809 opsize = *ptr++;
3810 if (opsize < 2) /* "silly options" */
3811 return mss;
3812 if (opsize > length)
3813 return mss; /* fail on partial options */
3814 if (opcode == TCPOPT_MSS && opsize == TCPOLEN_MSS) {
3815 u16 in_mss = get_unaligned_be16(ptr);
3816
3817 if (in_mss) {
3818 if (user_mss && user_mss < in_mss)
3819 in_mss = user_mss;
3820 mss = in_mss;
3821 }
3822 }
3823 ptr += opsize - 2;
3824 length -= opsize;
3825 }
3826 }
3827 return mss;
3828}
3829
3830/* Look for tcp options. Normally only called on SYN and SYNACK packets.
3831 * But, this can also be called on packets in the established flow when
3832 * the fast version below fails.
3833 */
3834void tcp_parse_options(const struct net *net,
3835 const struct sk_buff *skb,
3836 struct tcp_options_received *opt_rx, int estab,
3837 struct tcp_fastopen_cookie *foc)
3838{
3839 const unsigned char *ptr;
3840 const struct tcphdr *th = tcp_hdr(skb);
3841 int length = (th->doff * 4) - sizeof(struct tcphdr);
3842
3843 ptr = (const unsigned char *)(th + 1);
3844 opt_rx->saw_tstamp = 0;
3845
3846 while (length > 0) {
3847 int opcode = *ptr++;
3848 int opsize;
3849
3850 switch (opcode) {
3851 case TCPOPT_EOL:
3852 return;
3853 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3854 length--;
3855 continue;
3856 default:
3857 if (length < 2)
3858 return;
3859 opsize = *ptr++;
3860 if (opsize < 2) /* "silly options" */
3861 return;
3862 if (opsize > length)
3863 return; /* don't parse partial options */
3864 switch (opcode) {
3865 case TCPOPT_MSS:
3866 if (opsize == TCPOLEN_MSS && th->syn && !estab) {
3867 u16 in_mss = get_unaligned_be16(ptr);
3868 if (in_mss) {
3869 if (opt_rx->user_mss &&
3870 opt_rx->user_mss < in_mss)
3871 in_mss = opt_rx->user_mss;
3872 opt_rx->mss_clamp = in_mss;
3873 }
3874 }
3875 break;
3876 case TCPOPT_WINDOW:
3877 if (opsize == TCPOLEN_WINDOW && th->syn &&
3878 !estab && net->ipv4.sysctl_tcp_window_scaling) {
3879 __u8 snd_wscale = *(__u8 *)ptr;
3880 opt_rx->wscale_ok = 1;
3881 if (snd_wscale > TCP_MAX_WSCALE) {
3882 net_info_ratelimited("%s: Illegal window scaling value %d > %u received\n",
3883 __func__,
3884 snd_wscale,
3885 TCP_MAX_WSCALE);
3886 snd_wscale = TCP_MAX_WSCALE;
3887 }
3888 opt_rx->snd_wscale = snd_wscale;
3889 }
3890 break;
3891 case TCPOPT_TIMESTAMP:
3892 if ((opsize == TCPOLEN_TIMESTAMP) &&
3893 ((estab && opt_rx->tstamp_ok) ||
3894 (!estab && net->ipv4.sysctl_tcp_timestamps))) {
3895 opt_rx->saw_tstamp = 1;
3896 opt_rx->rcv_tsval = get_unaligned_be32(ptr);
3897 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
3898 }
3899 break;
3900 case TCPOPT_SACK_PERM:
3901 if (opsize == TCPOLEN_SACK_PERM && th->syn &&
3902 !estab && net->ipv4.sysctl_tcp_sack) {
3903 opt_rx->sack_ok = TCP_SACK_SEEN;
3904 tcp_sack_reset(opt_rx);
3905 }
3906 break;
3907
3908 case TCPOPT_SACK:
3909 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
3910 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3911 opt_rx->sack_ok) {
3912 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3913 }
3914 break;
3915#ifdef CONFIG_TCP_MD5SIG
3916 case TCPOPT_MD5SIG:
3917 /*
3918 * The MD5 Hash has already been
3919 * checked (see tcp_v{4,6}_do_rcv()).
3920 */
3921 break;
3922#endif
3923 case TCPOPT_FASTOPEN:
3924 tcp_parse_fastopen_option(
3925 opsize - TCPOLEN_FASTOPEN_BASE,
3926 ptr, th->syn, foc, false);
3927 break;
3928
3929 case TCPOPT_EXP:
3930 /* Fast Open option shares code 254 using a
3931 * 16 bits magic number.
3932 */
3933 if (opsize >= TCPOLEN_EXP_FASTOPEN_BASE &&
3934 get_unaligned_be16(ptr) ==
3935 TCPOPT_FASTOPEN_MAGIC)
3936 tcp_parse_fastopen_option(opsize -
3937 TCPOLEN_EXP_FASTOPEN_BASE,
3938 ptr + 2, th->syn, foc, true);
3939 else
3940 smc_parse_options(th, opt_rx, ptr,
3941 opsize);
3942 break;
3943
3944 }
3945 ptr += opsize-2;
3946 length -= opsize;
3947 }
3948 }
3949}
3950EXPORT_SYMBOL(tcp_parse_options);
3951
3952static bool tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th)
3953{
3954 const __be32 *ptr = (const __be32 *)(th + 1);
3955
3956 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3957 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3958 tp->rx_opt.saw_tstamp = 1;
3959 ++ptr;
3960 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3961 ++ptr;
3962 if (*ptr)
3963 tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset;
3964 else
3965 tp->rx_opt.rcv_tsecr = 0;
3966 return true;
3967 }
3968 return false;
3969}
3970
3971/* Fast parse options. This hopes to only see timestamps.
3972 * If it is wrong it falls back on tcp_parse_options().
3973 */
3974static bool tcp_fast_parse_options(const struct net *net,
3975 const struct sk_buff *skb,
3976 const struct tcphdr *th, struct tcp_sock *tp)
3977{
3978 /* In the spirit of fast parsing, compare doff directly to constant
3979 * values. Because equality is used, short doff can be ignored here.
3980 */
3981 if (th->doff == (sizeof(*th) / 4)) {
3982 tp->rx_opt.saw_tstamp = 0;
3983 return false;
3984 } else if (tp->rx_opt.tstamp_ok &&
3985 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
3986 if (tcp_parse_aligned_timestamp(tp, th))
3987 return true;
3988 }
3989
3990 tcp_parse_options(net, skb, &tp->rx_opt, 1, NULL);
3991 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
3992 tp->rx_opt.rcv_tsecr -= tp->tsoffset;
3993
3994 return true;
3995}
3996
3997#ifdef CONFIG_TCP_MD5SIG
3998/*
3999 * Parse MD5 Signature option
4000 */
4001const u8 *tcp_parse_md5sig_option(const struct tcphdr *th)
4002{
4003 int length = (th->doff << 2) - sizeof(*th);
4004 const u8 *ptr = (const u8 *)(th + 1);
4005
4006 /* If not enough data remaining, we can short cut */
4007 while (length >= TCPOLEN_MD5SIG) {
4008 int opcode = *ptr++;
4009 int opsize;
4010
4011 switch (opcode) {
4012 case TCPOPT_EOL:
4013 return NULL;
4014 case TCPOPT_NOP:
4015 length--;
4016 continue;
4017 default:
4018 opsize = *ptr++;
4019 if (opsize < 2 || opsize > length)
4020 return NULL;
4021 if (opcode == TCPOPT_MD5SIG)
4022 return opsize == TCPOLEN_MD5SIG ? ptr : NULL;
4023 }
4024 ptr += opsize - 2;
4025 length -= opsize;
4026 }
4027 return NULL;
4028}
4029EXPORT_SYMBOL(tcp_parse_md5sig_option);
4030#endif
4031
4032/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
4033 *
4034 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
4035 * it can pass through stack. So, the following predicate verifies that
4036 * this segment is not used for anything but congestion avoidance or
4037 * fast retransmit. Moreover, we even are able to eliminate most of such
4038 * second order effects, if we apply some small "replay" window (~RTO)
4039 * to timestamp space.
4040 *
4041 * All these measures still do not guarantee that we reject wrapped ACKs
4042 * on networks with high bandwidth, when sequence space is recycled fastly,
4043 * but it guarantees that such events will be very rare and do not affect
4044 * connection seriously. This doesn't look nice, but alas, PAWS is really
4045 * buggy extension.
4046 *
4047 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
4048 * states that events when retransmit arrives after original data are rare.
4049 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
4050 * the biggest problem on large power networks even with minor reordering.
4051 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
4052 * up to bandwidth of 18Gigabit/sec. 8) ]
4053 */
4054
4055static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
4056{
4057 const struct tcp_sock *tp = tcp_sk(sk);
4058 const struct tcphdr *th = tcp_hdr(skb);
4059 u32 seq = TCP_SKB_CB(skb)->seq;
4060 u32 ack = TCP_SKB_CB(skb)->ack_seq;
4061
4062 return (/* 1. Pure ACK with correct sequence number. */
4063 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
4064
4065 /* 2. ... and duplicate ACK. */
4066 ack == tp->snd_una &&
4067
4068 /* 3. ... and does not update window. */
4069 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
4070
4071 /* 4. ... and sits in replay window. */
4072 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
4073}
4074
4075static inline bool tcp_paws_discard(const struct sock *sk,
4076 const struct sk_buff *skb)
4077{
4078 const struct tcp_sock *tp = tcp_sk(sk);
4079
4080 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
4081 !tcp_disordered_ack(sk, skb);
4082}
4083
4084/* Check segment sequence number for validity.
4085 *
4086 * Segment controls are considered valid, if the segment
4087 * fits to the window after truncation to the window. Acceptability
4088 * of data (and SYN, FIN, of course) is checked separately.
4089 * See tcp_data_queue(), for example.
4090 *
4091 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4092 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4093 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4094 * (borrowed from freebsd)
4095 */
4096
4097static inline bool tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq)
4098{
4099 return !before(end_seq, tp->rcv_wup) &&
4100 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
4101}
4102
4103/* When we get a reset we do this. */
4104void tcp_reset(struct sock *sk)
4105{
4106 trace_tcp_receive_reset(sk);
4107
4108 /* We want the right error as BSD sees it (and indeed as we do). */
4109 switch (sk->sk_state) {
4110 case TCP_SYN_SENT:
4111 sk->sk_err = ECONNREFUSED;
4112 break;
4113 case TCP_CLOSE_WAIT:
4114 sk->sk_err = EPIPE;
4115 break;
4116 case TCP_CLOSE:
4117 return;
4118 default:
4119 sk->sk_err = ECONNRESET;
4120 }
4121 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4122 smp_wmb();
4123
4124 tcp_write_queue_purge(sk);
4125 tcp_done(sk);
4126
4127 if (!sock_flag(sk, SOCK_DEAD))
4128 sk->sk_error_report(sk);
4129}
4130
4131/*
4132 * Process the FIN bit. This now behaves as it is supposed to work
4133 * and the FIN takes effect when it is validly part of sequence
4134 * space. Not before when we get holes.
4135 *
4136 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4137 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4138 * TIME-WAIT)
4139 *
4140 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4141 * close and we go into CLOSING (and later onto TIME-WAIT)
4142 *
4143 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4144 */
4145void tcp_fin(struct sock *sk)
4146{
4147 struct tcp_sock *tp = tcp_sk(sk);
4148
4149 inet_csk_schedule_ack(sk);
4150
4151 sk->sk_shutdown |= RCV_SHUTDOWN;
4152 sock_set_flag(sk, SOCK_DONE);
4153
4154 switch (sk->sk_state) {
4155 case TCP_SYN_RECV:
4156 case TCP_ESTABLISHED:
4157 /* Move to CLOSE_WAIT */
4158 tcp_set_state(sk, TCP_CLOSE_WAIT);
4159 inet_csk_enter_pingpong_mode(sk);
4160 break;
4161
4162 case TCP_CLOSE_WAIT:
4163 case TCP_CLOSING:
4164 /* Received a retransmission of the FIN, do
4165 * nothing.
4166 */
4167 break;
4168 case TCP_LAST_ACK:
4169 /* RFC793: Remain in the LAST-ACK state. */
4170 break;
4171
4172 case TCP_FIN_WAIT1:
4173 /* This case occurs when a simultaneous close
4174 * happens, we must ack the received FIN and
4175 * enter the CLOSING state.
4176 */
4177 tcp_send_ack(sk);
4178 tcp_set_state(sk, TCP_CLOSING);
4179 break;
4180 case TCP_FIN_WAIT2:
4181 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4182 tcp_send_ack(sk);
4183 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4184 break;
4185 default:
4186 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4187 * cases we should never reach this piece of code.
4188 */
4189 pr_err("%s: Impossible, sk->sk_state=%d\n",
4190 __func__, sk->sk_state);
4191 break;
4192 }
4193
4194 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4195 * Probably, we should reset in this case. For now drop them.
4196 */
4197 skb_rbtree_purge(&tp->out_of_order_queue);
4198 if (tcp_is_sack(tp))
4199 tcp_sack_reset(&tp->rx_opt);
4200 sk_mem_reclaim(sk);
4201
4202 if (!sock_flag(sk, SOCK_DEAD)) {
4203 sk->sk_state_change(sk);
4204
4205 /* Do not send POLL_HUP for half duplex close. */
4206 if (sk->sk_shutdown == SHUTDOWN_MASK ||
4207 sk->sk_state == TCP_CLOSE)
4208 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
4209 else
4210 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
4211 }
4212}
4213
4214static inline bool tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
4215 u32 end_seq)
4216{
4217 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
4218 if (before(seq, sp->start_seq))
4219 sp->start_seq = seq;
4220 if (after(end_seq, sp->end_seq))
4221 sp->end_seq = end_seq;
4222 return true;
4223 }
4224 return false;
4225}
4226
4227static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
4228{
4229 struct tcp_sock *tp = tcp_sk(sk);
4230
4231 if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) {
4232 int mib_idx;
4233
4234 if (before(seq, tp->rcv_nxt))
4235 mib_idx = LINUX_MIB_TCPDSACKOLDSENT;
4236 else
4237 mib_idx = LINUX_MIB_TCPDSACKOFOSENT;
4238
4239 NET_INC_STATS(sock_net(sk), mib_idx);
4240
4241 tp->rx_opt.dsack = 1;
4242 tp->duplicate_sack[0].start_seq = seq;
4243 tp->duplicate_sack[0].end_seq = end_seq;
4244 }
4245}
4246
4247static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
4248{
4249 struct tcp_sock *tp = tcp_sk(sk);
4250
4251 if (!tp->rx_opt.dsack)
4252 tcp_dsack_set(sk, seq, end_seq);
4253 else
4254 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
4255}
4256
4257static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb)
4258{
4259 /* When the ACK path fails or drops most ACKs, the sender would
4260 * timeout and spuriously retransmit the same segment repeatedly.
4261 * The receiver remembers and reflects via DSACKs. Leverage the
4262 * DSACK state and change the txhash to re-route speculatively.
4263 */
4264 if (TCP_SKB_CB(skb)->seq == tcp_sk(sk)->duplicate_sack[0].start_seq)
4265 sk_rethink_txhash(sk);
4266}
4267
4268static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
4269{
4270 struct tcp_sock *tp = tcp_sk(sk);
4271
4272 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4273 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4274 NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4275 tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
4276
4277 if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) {
4278 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4279
4280 tcp_rcv_spurious_retrans(sk, skb);
4281 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
4282 end_seq = tp->rcv_nxt;
4283 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
4284 }
4285 }
4286
4287 tcp_send_ack(sk);
4288}
4289
4290/* These routines update the SACK block as out-of-order packets arrive or
4291 * in-order packets close up the sequence space.
4292 */
4293static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
4294{
4295 int this_sack;
4296 struct tcp_sack_block *sp = &tp->selective_acks[0];
4297 struct tcp_sack_block *swalk = sp + 1;
4298
4299 /* See if the recent change to the first SACK eats into
4300 * or hits the sequence space of other SACK blocks, if so coalesce.
4301 */
4302 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
4303 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
4304 int i;
4305
4306 /* Zap SWALK, by moving every further SACK up by one slot.
4307 * Decrease num_sacks.
4308 */
4309 tp->rx_opt.num_sacks--;
4310 for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
4311 sp[i] = sp[i + 1];
4312 continue;
4313 }
4314 this_sack++, swalk++;
4315 }
4316}
4317
4318static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
4319{
4320 struct tcp_sock *tp = tcp_sk(sk);
4321 struct tcp_sack_block *sp = &tp->selective_acks[0];
4322 int cur_sacks = tp->rx_opt.num_sacks;
4323 int this_sack;
4324
4325 if (!cur_sacks)
4326 goto new_sack;
4327
4328 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
4329 if (tcp_sack_extend(sp, seq, end_seq)) {
4330 /* Rotate this_sack to the first one. */
4331 for (; this_sack > 0; this_sack--, sp--)
4332 swap(*sp, *(sp - 1));
4333 if (cur_sacks > 1)
4334 tcp_sack_maybe_coalesce(tp);
4335 return;
4336 }
4337 }
4338
4339 /* Could not find an adjacent existing SACK, build a new one,
4340 * put it at the front, and shift everyone else down. We
4341 * always know there is at least one SACK present already here.
4342 *
4343 * If the sack array is full, forget about the last one.
4344 */
4345 if (this_sack >= TCP_NUM_SACKS) {
4346 if (tp->compressed_ack > TCP_FASTRETRANS_THRESH)
4347 tcp_send_ack(sk);
4348 this_sack--;
4349 tp->rx_opt.num_sacks--;
4350 sp--;
4351 }
4352 for (; this_sack > 0; this_sack--, sp--)
4353 *sp = *(sp - 1);
4354
4355new_sack:
4356 /* Build the new head SACK, and we're done. */
4357 sp->start_seq = seq;
4358 sp->end_seq = end_seq;
4359 tp->rx_opt.num_sacks++;
4360}
4361
4362/* RCV.NXT advances, some SACKs should be eaten. */
4363
4364static void tcp_sack_remove(struct tcp_sock *tp)
4365{
4366 struct tcp_sack_block *sp = &tp->selective_acks[0];
4367 int num_sacks = tp->rx_opt.num_sacks;
4368 int this_sack;
4369
4370 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4371 if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
4372 tp->rx_opt.num_sacks = 0;
4373 return;
4374 }
4375
4376 for (this_sack = 0; this_sack < num_sacks;) {
4377 /* Check if the start of the sack is covered by RCV.NXT. */
4378 if (!before(tp->rcv_nxt, sp->start_seq)) {
4379 int i;
4380
4381 /* RCV.NXT must cover all the block! */
4382 WARN_ON(before(tp->rcv_nxt, sp->end_seq));
4383
4384 /* Zap this SACK, by moving forward any other SACKS. */
4385 for (i = this_sack+1; i < num_sacks; i++)
4386 tp->selective_acks[i-1] = tp->selective_acks[i];
4387 num_sacks--;
4388 continue;
4389 }
4390 this_sack++;
4391 sp++;
4392 }
4393 tp->rx_opt.num_sacks = num_sacks;
4394}
4395
4396/**
4397 * tcp_try_coalesce - try to merge skb to prior one
4398 * @sk: socket
4399 * @dest: destination queue
4400 * @to: prior buffer
4401 * @from: buffer to add in queue
4402 * @fragstolen: pointer to boolean
4403 *
4404 * Before queueing skb @from after @to, try to merge them
4405 * to reduce overall memory use and queue lengths, if cost is small.
4406 * Packets in ofo or receive queues can stay a long time.
4407 * Better try to coalesce them right now to avoid future collapses.
4408 * Returns true if caller should free @from instead of queueing it
4409 */
4410static bool tcp_try_coalesce(struct sock *sk,
4411 struct sk_buff *to,
4412 struct sk_buff *from,
4413 bool *fragstolen)
4414{
4415 int delta;
4416
4417 *fragstolen = false;
4418
4419 /* Its possible this segment overlaps with prior segment in queue */
4420 if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq)
4421 return false;
4422
4423#ifdef CONFIG_TLS_DEVICE
4424 if (from->decrypted != to->decrypted)
4425 return false;
4426#endif
4427
4428 if (!skb_try_coalesce(to, from, fragstolen, &delta))
4429 return false;
4430
4431 atomic_add(delta, &sk->sk_rmem_alloc);
4432 sk_mem_charge(sk, delta);
4433 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE);
4434 TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq;
4435 TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq;
4436 TCP_SKB_CB(to)->tcp_flags |= TCP_SKB_CB(from)->tcp_flags;
4437
4438 if (TCP_SKB_CB(from)->has_rxtstamp) {
4439 TCP_SKB_CB(to)->has_rxtstamp = true;
4440 to->tstamp = from->tstamp;
4441 skb_hwtstamps(to)->hwtstamp = skb_hwtstamps(from)->hwtstamp;
4442 }
4443
4444 return true;
4445}
4446
4447static bool tcp_ooo_try_coalesce(struct sock *sk,
4448 struct sk_buff *to,
4449 struct sk_buff *from,
4450 bool *fragstolen)
4451{
4452 bool res = tcp_try_coalesce(sk, to, from, fragstolen);
4453
4454 /* In case tcp_drop() is called later, update to->gso_segs */
4455 if (res) {
4456 u32 gso_segs = max_t(u16, 1, skb_shinfo(to)->gso_segs) +
4457 max_t(u16, 1, skb_shinfo(from)->gso_segs);
4458
4459 skb_shinfo(to)->gso_segs = min_t(u32, gso_segs, 0xFFFF);
4460 }
4461 return res;
4462}
4463
4464static void tcp_drop(struct sock *sk, struct sk_buff *skb)
4465{
4466 sk_drops_add(sk, skb);
4467 __kfree_skb(skb);
4468}
4469
4470/* This one checks to see if we can put data from the
4471 * out_of_order queue into the receive_queue.
4472 */
4473static void tcp_ofo_queue(struct sock *sk)
4474{
4475 struct tcp_sock *tp = tcp_sk(sk);
4476 __u32 dsack_high = tp->rcv_nxt;
4477 bool fin, fragstolen, eaten;
4478 struct sk_buff *skb, *tail;
4479 struct rb_node *p;
4480
4481 p = rb_first(&tp->out_of_order_queue);
4482 while (p) {
4483 skb = rb_to_skb(p);
4484 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4485 break;
4486
4487 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
4488 __u32 dsack = dsack_high;
4489 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
4490 dsack_high = TCP_SKB_CB(skb)->end_seq;
4491 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack);
4492 }
4493 p = rb_next(p);
4494 rb_erase(&skb->rbnode, &tp->out_of_order_queue);
4495
4496 if (unlikely(!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))) {
4497 tcp_drop(sk, skb);
4498 continue;
4499 }
4500
4501 tail = skb_peek_tail(&sk->sk_receive_queue);
4502 eaten = tail && tcp_try_coalesce(sk, tail, skb, &fragstolen);
4503 tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
4504 fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
4505 if (!eaten)
4506 __skb_queue_tail(&sk->sk_receive_queue, skb);
4507 else
4508 kfree_skb_partial(skb, fragstolen);
4509
4510 if (unlikely(fin)) {
4511 tcp_fin(sk);
4512 /* tcp_fin() purges tp->out_of_order_queue,
4513 * so we must end this loop right now.
4514 */
4515 break;
4516 }
4517 }
4518}
4519
4520static bool tcp_prune_ofo_queue(struct sock *sk);
4521static int tcp_prune_queue(struct sock *sk);
4522
4523static int tcp_try_rmem_schedule(struct sock *sk, struct sk_buff *skb,
4524 unsigned int size)
4525{
4526 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
4527 !sk_rmem_schedule(sk, skb, size)) {
4528
4529 if (tcp_prune_queue(sk) < 0)
4530 return -1;
4531
4532 while (!sk_rmem_schedule(sk, skb, size)) {
4533 if (!tcp_prune_ofo_queue(sk))
4534 return -1;
4535 }
4536 }
4537 return 0;
4538}
4539
4540static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
4541{
4542 struct tcp_sock *tp = tcp_sk(sk);
4543 struct rb_node **p, *parent;
4544 struct sk_buff *skb1;
4545 u32 seq, end_seq;
4546 bool fragstolen;
4547
4548 tcp_ecn_check_ce(sk, skb);
4549
4550 if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
4551 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFODROP);
4552 tcp_drop(sk, skb);
4553 return;
4554 }
4555
4556 /* Disable header prediction. */
4557 tp->pred_flags = 0;
4558 inet_csk_schedule_ack(sk);
4559
4560 tp->rcv_ooopack += max_t(u16, 1, skb_shinfo(skb)->gso_segs);
4561 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
4562 seq = TCP_SKB_CB(skb)->seq;
4563 end_seq = TCP_SKB_CB(skb)->end_seq;
4564
4565 p = &tp->out_of_order_queue.rb_node;
4566 if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
4567 /* Initial out of order segment, build 1 SACK. */
4568 if (tcp_is_sack(tp)) {
4569 tp->rx_opt.num_sacks = 1;
4570 tp->selective_acks[0].start_seq = seq;
4571 tp->selective_acks[0].end_seq = end_seq;
4572 }
4573 rb_link_node(&skb->rbnode, NULL, p);
4574 rb_insert_color(&skb->rbnode, &tp->out_of_order_queue);
4575 tp->ooo_last_skb = skb;
4576 goto end;
4577 }
4578
4579 /* In the typical case, we are adding an skb to the end of the list.
4580 * Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
4581 */
4582 if (tcp_ooo_try_coalesce(sk, tp->ooo_last_skb,
4583 skb, &fragstolen)) {
4584coalesce_done:
4585 tcp_grow_window(sk, skb);
4586 kfree_skb_partial(skb, fragstolen);
4587 skb = NULL;
4588 goto add_sack;
4589 }
4590 /* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
4591 if (!before(seq, TCP_SKB_CB(tp->ooo_last_skb)->end_seq)) {
4592 parent = &tp->ooo_last_skb->rbnode;
4593 p = &parent->rb_right;
4594 goto insert;
4595 }
4596
4597 /* Find place to insert this segment. Handle overlaps on the way. */
4598 parent = NULL;
4599 while (*p) {
4600 parent = *p;
4601 skb1 = rb_to_skb(parent);
4602 if (before(seq, TCP_SKB_CB(skb1)->seq)) {
4603 p = &parent->rb_left;
4604 continue;
4605 }
4606 if (before(seq, TCP_SKB_CB(skb1)->end_seq)) {
4607 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4608 /* All the bits are present. Drop. */
4609 NET_INC_STATS(sock_net(sk),
4610 LINUX_MIB_TCPOFOMERGE);
4611 tcp_drop(sk, skb);
4612 skb = NULL;
4613 tcp_dsack_set(sk, seq, end_seq);
4614 goto add_sack;
4615 }
4616 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
4617 /* Partial overlap. */
4618 tcp_dsack_set(sk, seq, TCP_SKB_CB(skb1)->end_seq);
4619 } else {
4620 /* skb's seq == skb1's seq and skb covers skb1.
4621 * Replace skb1 with skb.
4622 */
4623 rb_replace_node(&skb1->rbnode, &skb->rbnode,
4624 &tp->out_of_order_queue);
4625 tcp_dsack_extend(sk,
4626 TCP_SKB_CB(skb1)->seq,
4627 TCP_SKB_CB(skb1)->end_seq);
4628 NET_INC_STATS(sock_net(sk),
4629 LINUX_MIB_TCPOFOMERGE);
4630 tcp_drop(sk, skb1);
4631 goto merge_right;
4632 }
4633 } else if (tcp_ooo_try_coalesce(sk, skb1,
4634 skb, &fragstolen)) {
4635 goto coalesce_done;
4636 }
4637 p = &parent->rb_right;
4638 }
4639insert:
4640 /* Insert segment into RB tree. */
4641 rb_link_node(&skb->rbnode, parent, p);
4642 rb_insert_color(&skb->rbnode, &tp->out_of_order_queue);
4643
4644merge_right:
4645 /* Remove other segments covered by skb. */
4646 while ((skb1 = skb_rb_next(skb)) != NULL) {
4647 if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
4648 break;
4649 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4650 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4651 end_seq);
4652 break;
4653 }
4654 rb_erase(&skb1->rbnode, &tp->out_of_order_queue);
4655 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4656 TCP_SKB_CB(skb1)->end_seq);
4657 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
4658 tcp_drop(sk, skb1);
4659 }
4660 /* If there is no skb after us, we are the last_skb ! */
4661 if (!skb1)
4662 tp->ooo_last_skb = skb;
4663
4664add_sack:
4665 if (tcp_is_sack(tp))
4666 tcp_sack_new_ofo_skb(sk, seq, end_seq);
4667end:
4668 if (skb) {
4669 tcp_grow_window(sk, skb);
4670 skb_condense(skb);
4671 skb_set_owner_r(skb, sk);
4672 }
4673}
4674
4675static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb,
4676 bool *fragstolen)
4677{
4678 int eaten;
4679 struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
4680
4681 eaten = (tail &&
4682 tcp_try_coalesce(sk, tail,
4683 skb, fragstolen)) ? 1 : 0;
4684 tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
4685 if (!eaten) {
4686 __skb_queue_tail(&sk->sk_receive_queue, skb);
4687 skb_set_owner_r(skb, sk);
4688 }
4689 return eaten;
4690}
4691
4692int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
4693{
4694 struct sk_buff *skb;
4695 int err = -ENOMEM;
4696 int data_len = 0;
4697 bool fragstolen;
4698
4699 if (size == 0)
4700 return 0;
4701
4702 if (size > PAGE_SIZE) {
4703 int npages = min_t(size_t, size >> PAGE_SHIFT, MAX_SKB_FRAGS);
4704
4705 data_len = npages << PAGE_SHIFT;
4706 size = data_len + (size & ~PAGE_MASK);
4707 }
4708 skb = alloc_skb_with_frags(size - data_len, data_len,
4709 PAGE_ALLOC_COSTLY_ORDER,
4710 &err, sk->sk_allocation);
4711 if (!skb)
4712 goto err;
4713
4714 skb_put(skb, size - data_len);
4715 skb->data_len = data_len;
4716 skb->len = size;
4717
4718 if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) {
4719 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP);
4720 goto err_free;
4721 }
4722
4723 err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size);
4724 if (err)
4725 goto err_free;
4726
4727 TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;
4728 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size;
4729 TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1;
4730
4731 if (tcp_queue_rcv(sk, skb, &fragstolen)) {
4732 WARN_ON_ONCE(fragstolen); /* should not happen */
4733 __kfree_skb(skb);
4734 }
4735 return size;
4736
4737err_free:
4738 kfree_skb(skb);
4739err:
4740 return err;
4741
4742}
4743
4744void tcp_data_ready(struct sock *sk)
4745{
4746 const struct tcp_sock *tp = tcp_sk(sk);
4747 int avail = tp->rcv_nxt - tp->copied_seq;
4748
4749 if (avail < sk->sk_rcvlowat && !sock_flag(sk, SOCK_DONE))
4750 return;
4751
4752 sk->sk_data_ready(sk);
4753}
4754
4755static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
4756{
4757 struct tcp_sock *tp = tcp_sk(sk);
4758 bool fragstolen;
4759 int eaten;
4760
4761 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
4762 __kfree_skb(skb);
4763 return;
4764 }
4765 skb_dst_drop(skb);
4766 __skb_pull(skb, tcp_hdr(skb)->doff * 4);
4767
4768 tcp_ecn_accept_cwr(sk, skb);
4769
4770 tp->rx_opt.dsack = 0;
4771
4772 /* Queue data for delivery to the user.
4773 * Packets in sequence go to the receive queue.
4774 * Out of sequence packets to the out_of_order_queue.
4775 */
4776 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4777 if (tcp_receive_window(tp) == 0) {
4778 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP);
4779 goto out_of_window;
4780 }
4781
4782 /* Ok. In sequence. In window. */
4783queue_and_out:
4784 if (skb_queue_len(&sk->sk_receive_queue) == 0)
4785 sk_forced_mem_schedule(sk, skb->truesize);
4786 else if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) {
4787 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP);
4788 goto drop;
4789 }
4790
4791 eaten = tcp_queue_rcv(sk, skb, &fragstolen);
4792 if (skb->len)
4793 tcp_event_data_recv(sk, skb);
4794 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
4795 tcp_fin(sk);
4796
4797 if (!RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
4798 tcp_ofo_queue(sk);
4799
4800 /* RFC5681. 4.2. SHOULD send immediate ACK, when
4801 * gap in queue is filled.
4802 */
4803 if (RB_EMPTY_ROOT(&tp->out_of_order_queue))
4804 inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
4805 }
4806
4807 if (tp->rx_opt.num_sacks)
4808 tcp_sack_remove(tp);
4809
4810 tcp_fast_path_check(sk);
4811
4812 if (eaten > 0)
4813 kfree_skb_partial(skb, fragstolen);
4814 if (!sock_flag(sk, SOCK_DEAD))
4815 tcp_data_ready(sk);
4816 return;
4817 }
4818
4819 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4820 tcp_rcv_spurious_retrans(sk, skb);
4821 /* A retransmit, 2nd most common case. Force an immediate ack. */
4822 NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4823 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4824
4825out_of_window:
4826 tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
4827 inet_csk_schedule_ack(sk);
4828drop:
4829 tcp_drop(sk, skb);
4830 return;
4831 }
4832
4833 /* Out of window. F.e. zero window probe. */
4834 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
4835 goto out_of_window;
4836
4837 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4838 /* Partial packet, seq < rcv_next < end_seq */
4839 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
4840
4841 /* If window is closed, drop tail of packet. But after
4842 * remembering D-SACK for its head made in previous line.
4843 */
4844 if (!tcp_receive_window(tp)) {
4845 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP);
4846 goto out_of_window;
4847 }
4848 goto queue_and_out;
4849 }
4850
4851 tcp_data_queue_ofo(sk, skb);
4852}
4853
4854static struct sk_buff *tcp_skb_next(struct sk_buff *skb, struct sk_buff_head *list)
4855{
4856 if (list)
4857 return !skb_queue_is_last(list, skb) ? skb->next : NULL;
4858
4859 return skb_rb_next(skb);
4860}
4861
4862static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
4863 struct sk_buff_head *list,
4864 struct rb_root *root)
4865{
4866 struct sk_buff *next = tcp_skb_next(skb, list);
4867
4868 if (list)
4869 __skb_unlink(skb, list);
4870 else
4871 rb_erase(&skb->rbnode, root);
4872
4873 __kfree_skb(skb);
4874 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
4875
4876 return next;
4877}
4878
4879/* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */
4880void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
4881{
4882 struct rb_node **p = &root->rb_node;
4883 struct rb_node *parent = NULL;
4884 struct sk_buff *skb1;
4885
4886 while (*p) {
4887 parent = *p;
4888 skb1 = rb_to_skb(parent);
4889 if (before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb1)->seq))
4890 p = &parent->rb_left;
4891 else
4892 p = &parent->rb_right;
4893 }
4894 rb_link_node(&skb->rbnode, parent, p);
4895 rb_insert_color(&skb->rbnode, root);
4896}
4897
4898/* Collapse contiguous sequence of skbs head..tail with
4899 * sequence numbers start..end.
4900 *
4901 * If tail is NULL, this means until the end of the queue.
4902 *
4903 * Segments with FIN/SYN are not collapsed (only because this
4904 * simplifies code)
4905 */
4906static void
4907tcp_collapse(struct sock *sk, struct sk_buff_head *list, struct rb_root *root,
4908 struct sk_buff *head, struct sk_buff *tail, u32 start, u32 end)
4909{
4910 struct sk_buff *skb = head, *n;
4911 struct sk_buff_head tmp;
4912 bool end_of_skbs;
4913
4914 /* First, check that queue is collapsible and find
4915 * the point where collapsing can be useful.
4916 */
4917restart:
4918 for (end_of_skbs = true; skb != NULL && skb != tail; skb = n) {
4919 n = tcp_skb_next(skb, list);
4920
4921 /* No new bits? It is possible on ofo queue. */
4922 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4923 skb = tcp_collapse_one(sk, skb, list, root);
4924 if (!skb)
4925 break;
4926 goto restart;
4927 }
4928
4929 /* The first skb to collapse is:
4930 * - not SYN/FIN and
4931 * - bloated or contains data before "start" or
4932 * overlaps to the next one.
4933 */
4934 if (!(TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)) &&
4935 (tcp_win_from_space(sk, skb->truesize) > skb->len ||
4936 before(TCP_SKB_CB(skb)->seq, start))) {
4937 end_of_skbs = false;
4938 break;
4939 }
4940
4941 if (n && n != tail &&
4942 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(n)->seq) {
4943 end_of_skbs = false;
4944 break;
4945 }
4946
4947 /* Decided to skip this, advance start seq. */
4948 start = TCP_SKB_CB(skb)->end_seq;
4949 }
4950 if (end_of_skbs ||
4951 (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
4952 return;
4953
4954 __skb_queue_head_init(&tmp);
4955
4956 while (before(start, end)) {
4957 int copy = min_t(int, SKB_MAX_ORDER(0, 0), end - start);
4958 struct sk_buff *nskb;
4959
4960 nskb = alloc_skb(copy, GFP_ATOMIC);
4961 if (!nskb)
4962 break;
4963
4964 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
4965#ifdef CONFIG_TLS_DEVICE
4966 nskb->decrypted = skb->decrypted;
4967#endif
4968 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
4969 if (list)
4970 __skb_queue_before(list, skb, nskb);
4971 else
4972 __skb_queue_tail(&tmp, nskb); /* defer rbtree insertion */
4973 skb_set_owner_r(nskb, sk);
4974
4975 /* Copy data, releasing collapsed skbs. */
4976 while (copy > 0) {
4977 int offset = start - TCP_SKB_CB(skb)->seq;
4978 int size = TCP_SKB_CB(skb)->end_seq - start;
4979
4980 BUG_ON(offset < 0);
4981 if (size > 0) {
4982 size = min(copy, size);
4983 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
4984 BUG();
4985 TCP_SKB_CB(nskb)->end_seq += size;
4986 copy -= size;
4987 start += size;
4988 }
4989 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4990 skb = tcp_collapse_one(sk, skb, list, root);
4991 if (!skb ||
4992 skb == tail ||
4993 (TCP_SKB_CB(skb)->tcp_flags & (TCPHDR_SYN | TCPHDR_FIN)))
4994 goto end;
4995#ifdef CONFIG_TLS_DEVICE
4996 if (skb->decrypted != nskb->decrypted)
4997 goto end;
4998#endif
4999 }
5000 }
5001 }
5002end:
5003 skb_queue_walk_safe(&tmp, skb, n)
5004 tcp_rbtree_insert(root, skb);
5005}
5006
5007/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
5008 * and tcp_collapse() them until all the queue is collapsed.
5009 */
5010static void tcp_collapse_ofo_queue(struct sock *sk)
5011{
5012 struct tcp_sock *tp = tcp_sk(sk);
5013 u32 range_truesize, sum_tiny = 0;
5014 struct sk_buff *skb, *head;
5015 u32 start, end;
5016
5017 skb = skb_rb_first(&tp->out_of_order_queue);
5018new_range:
5019 if (!skb) {
5020 tp->ooo_last_skb = skb_rb_last(&tp->out_of_order_queue);
5021 return;
5022 }
5023 start = TCP_SKB_CB(skb)->seq;
5024 end = TCP_SKB_CB(skb)->end_seq;
5025 range_truesize = skb->truesize;
5026
5027 for (head = skb;;) {
5028 skb = skb_rb_next(skb);
5029
5030 /* Range is terminated when we see a gap or when
5031 * we are at the queue end.
5032 */
5033 if (!skb ||
5034 after(TCP_SKB_CB(skb)->seq, end) ||
5035 before(TCP_SKB_CB(skb)->end_seq, start)) {
5036 /* Do not attempt collapsing tiny skbs */
5037 if (range_truesize != head->truesize ||
5038 end - start >= SKB_WITH_OVERHEAD(SK_MEM_QUANTUM)) {
5039 tcp_collapse(sk, NULL, &tp->out_of_order_queue,
5040 head, skb, start, end);
5041 } else {
5042 sum_tiny += range_truesize;
5043 if (sum_tiny > sk->sk_rcvbuf >> 3)
5044 return;
5045 }
5046 goto new_range;
5047 }
5048
5049 range_truesize += skb->truesize;
5050 if (unlikely(before(TCP_SKB_CB(skb)->seq, start)))
5051 start = TCP_SKB_CB(skb)->seq;
5052 if (after(TCP_SKB_CB(skb)->end_seq, end))
5053 end = TCP_SKB_CB(skb)->end_seq;
5054 }
5055}
5056
5057/*
5058 * Clean the out-of-order queue to make room.
5059 * We drop high sequences packets to :
5060 * 1) Let a chance for holes to be filled.
5061 * 2) not add too big latencies if thousands of packets sit there.
5062 * (But if application shrinks SO_RCVBUF, we could still end up
5063 * freeing whole queue here)
5064 * 3) Drop at least 12.5 % of sk_rcvbuf to avoid malicious attacks.
5065 *
5066 * Return true if queue has shrunk.
5067 */
5068static bool tcp_prune_ofo_queue(struct sock *sk)
5069{
5070 struct tcp_sock *tp = tcp_sk(sk);
5071 struct rb_node *node, *prev;
5072 int goal;
5073
5074 if (RB_EMPTY_ROOT(&tp->out_of_order_queue))
5075 return false;
5076
5077 NET_INC_STATS(sock_net(sk), LINUX_MIB_OFOPRUNED);
5078 goal = sk->sk_rcvbuf >> 3;
5079 node = &tp->ooo_last_skb->rbnode;
5080 do {
5081 prev = rb_prev(node);
5082 rb_erase(node, &tp->out_of_order_queue);
5083 goal -= rb_to_skb(node)->truesize;
5084 tcp_drop(sk, rb_to_skb(node));
5085 if (!prev || goal <= 0) {
5086 sk_mem_reclaim(sk);
5087 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
5088 !tcp_under_memory_pressure(sk))
5089 break;
5090 goal = sk->sk_rcvbuf >> 3;
5091 }
5092 node = prev;
5093 } while (node);
5094 tp->ooo_last_skb = rb_to_skb(prev);
5095
5096 /* Reset SACK state. A conforming SACK implementation will
5097 * do the same at a timeout based retransmit. When a connection
5098 * is in a sad state like this, we care only about integrity
5099 * of the connection not performance.
5100 */
5101 if (tp->rx_opt.sack_ok)
5102 tcp_sack_reset(&tp->rx_opt);
5103 return true;
5104}
5105
5106/* Reduce allocated memory if we can, trying to get
5107 * the socket within its memory limits again.
5108 *
5109 * Return less than zero if we should start dropping frames
5110 * until the socket owning process reads some of the data
5111 * to stabilize the situation.
5112 */
5113static int tcp_prune_queue(struct sock *sk)
5114{
5115 struct tcp_sock *tp = tcp_sk(sk);
5116
5117 NET_INC_STATS(sock_net(sk), LINUX_MIB_PRUNECALLED);
5118
5119 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
5120 tcp_clamp_window(sk);
5121 else if (tcp_under_memory_pressure(sk))
5122 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
5123
5124 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
5125 return 0;
5126
5127 tcp_collapse_ofo_queue(sk);
5128 if (!skb_queue_empty(&sk->sk_receive_queue))
5129 tcp_collapse(sk, &sk->sk_receive_queue, NULL,
5130 skb_peek(&sk->sk_receive_queue),
5131 NULL,
5132 tp->copied_seq, tp->rcv_nxt);
5133 sk_mem_reclaim(sk);
5134
5135 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
5136 return 0;
5137
5138 /* Collapsing did not help, destructive actions follow.
5139 * This must not ever occur. */
5140
5141 tcp_prune_ofo_queue(sk);
5142
5143 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
5144 return 0;
5145
5146 /* If we are really being abused, tell the caller to silently
5147 * drop receive data on the floor. It will get retransmitted
5148 * and hopefully then we'll have sufficient space.
5149 */
5150 NET_INC_STATS(sock_net(sk), LINUX_MIB_RCVPRUNED);
5151
5152 /* Massive buffer overcommit. */
5153 tp->pred_flags = 0;
5154 return -1;
5155}
5156
5157static bool tcp_should_expand_sndbuf(const struct sock *sk)
5158{
5159 const struct tcp_sock *tp = tcp_sk(sk);
5160
5161 /* If the user specified a specific send buffer setting, do
5162 * not modify it.
5163 */
5164 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
5165 return false;
5166
5167 /* If we are under global TCP memory pressure, do not expand. */
5168 if (tcp_under_memory_pressure(sk))
5169 return false;
5170
5171 /* If we are under soft global TCP memory pressure, do not expand. */
5172 if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0))
5173 return false;
5174
5175 /* If we filled the congestion window, do not expand. */
5176 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
5177 return false;
5178
5179 return true;
5180}
5181
5182/* When incoming ACK allowed to free some skb from write_queue,
5183 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
5184 * on the exit from tcp input handler.
5185 *
5186 * PROBLEM: sndbuf expansion does not work well with largesend.
5187 */
5188static void tcp_new_space(struct sock *sk)
5189{
5190 struct tcp_sock *tp = tcp_sk(sk);
5191
5192 if (tcp_should_expand_sndbuf(sk)) {
5193 tcp_sndbuf_expand(sk);
5194 tp->snd_cwnd_stamp = tcp_jiffies32;
5195 }
5196
5197 sk->sk_write_space(sk);
5198}
5199
5200static void tcp_check_space(struct sock *sk)
5201{
5202 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
5203 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
5204 /* pairs with tcp_poll() */
5205 smp_mb();
5206 if (sk->sk_socket &&
5207 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
5208 tcp_new_space(sk);
5209 if (!test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
5210 tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
5211 }
5212 }
5213}
5214
5215static inline void tcp_data_snd_check(struct sock *sk)
5216{
5217 tcp_push_pending_frames(sk);
5218 tcp_check_space(sk);
5219}
5220
5221/*
5222 * Check if sending an ack is needed.
5223 */
5224static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
5225{
5226 struct tcp_sock *tp = tcp_sk(sk);
5227 unsigned long rtt, delay;
5228
5229 /* More than one full frame received... */
5230 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
5231 /* ... and right edge of window advances far enough.
5232 * (tcp_recvmsg() will send ACK otherwise).
5233 * If application uses SO_RCVLOWAT, we want send ack now if
5234 * we have not received enough bytes to satisfy the condition.
5235 */
5236 (tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat ||
5237 __tcp_select_window(sk) >= tp->rcv_wnd)) ||
5238 /* We ACK each frame or... */
5239 tcp_in_quickack_mode(sk) ||
5240 /* Protocol state mandates a one-time immediate ACK */
5241 inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOW) {
5242send_now:
5243 tcp_send_ack(sk);
5244 return;
5245 }
5246
5247 if (!ofo_possible || RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
5248 tcp_send_delayed_ack(sk);
5249 return;
5250 }
5251
5252 if (!tcp_is_sack(tp) ||
5253 tp->compressed_ack >= sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr)
5254 goto send_now;
5255
5256 if (tp->compressed_ack_rcv_nxt != tp->rcv_nxt) {
5257 tp->compressed_ack_rcv_nxt = tp->rcv_nxt;
5258 if (tp->compressed_ack > TCP_FASTRETRANS_THRESH)
5259 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
5260 tp->compressed_ack - TCP_FASTRETRANS_THRESH);
5261 tp->compressed_ack = 0;
5262 }
5263
5264 if (++tp->compressed_ack <= TCP_FASTRETRANS_THRESH)
5265 goto send_now;
5266
5267 if (hrtimer_is_queued(&tp->compressed_ack_timer))
5268 return;
5269
5270 /* compress ack timer : 5 % of rtt, but no more than tcp_comp_sack_delay_ns */
5271
5272 rtt = tp->rcv_rtt_est.rtt_us;
5273 if (tp->srtt_us && tp->srtt_us < rtt)
5274 rtt = tp->srtt_us;
5275
5276 delay = min_t(unsigned long, sock_net(sk)->ipv4.sysctl_tcp_comp_sack_delay_ns,
5277 rtt * (NSEC_PER_USEC >> 3)/20);
5278 sock_hold(sk);
5279 hrtimer_start(&tp->compressed_ack_timer, ns_to_ktime(delay),
5280 HRTIMER_MODE_REL_PINNED_SOFT);
5281}
5282
5283static inline void tcp_ack_snd_check(struct sock *sk)
5284{
5285 if (!inet_csk_ack_scheduled(sk)) {
5286 /* We sent a data segment already. */
5287 return;
5288 }
5289 __tcp_ack_snd_check(sk, 1);
5290}
5291
5292/*
5293 * This routine is only called when we have urgent data
5294 * signaled. Its the 'slow' part of tcp_urg. It could be
5295 * moved inline now as tcp_urg is only called from one
5296 * place. We handle URGent data wrong. We have to - as
5297 * BSD still doesn't use the correction from RFC961.
5298 * For 1003.1g we should support a new option TCP_STDURG to permit
5299 * either form (or just set the sysctl tcp_stdurg).
5300 */
5301
5302static void tcp_check_urg(struct sock *sk, const struct tcphdr *th)
5303{
5304 struct tcp_sock *tp = tcp_sk(sk);
5305 u32 ptr = ntohs(th->urg_ptr);
5306
5307 if (ptr && !sock_net(sk)->ipv4.sysctl_tcp_stdurg)
5308 ptr--;
5309 ptr += ntohl(th->seq);
5310
5311 /* Ignore urgent data that we've already seen and read. */
5312 if (after(tp->copied_seq, ptr))
5313 return;
5314
5315 /* Do not replay urg ptr.
5316 *
5317 * NOTE: interesting situation not covered by specs.
5318 * Misbehaving sender may send urg ptr, pointing to segment,
5319 * which we already have in ofo queue. We are not able to fetch
5320 * such data and will stay in TCP_URG_NOTYET until will be eaten
5321 * by recvmsg(). Seems, we are not obliged to handle such wicked
5322 * situations. But it is worth to think about possibility of some
5323 * DoSes using some hypothetical application level deadlock.
5324 */
5325 if (before(ptr, tp->rcv_nxt))
5326 return;
5327
5328 /* Do we already have a newer (or duplicate) urgent pointer? */
5329 if (tp->urg_data && !after(ptr, tp->urg_seq))
5330 return;
5331
5332 /* Tell the world about our new urgent pointer. */
5333 sk_send_sigurg(sk);
5334
5335 /* We may be adding urgent data when the last byte read was
5336 * urgent. To do this requires some care. We cannot just ignore
5337 * tp->copied_seq since we would read the last urgent byte again
5338 * as data, nor can we alter copied_seq until this data arrives
5339 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5340 *
5341 * NOTE. Double Dutch. Rendering to plain English: author of comment
5342 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5343 * and expect that both A and B disappear from stream. This is _wrong_.
5344 * Though this happens in BSD with high probability, this is occasional.
5345 * Any application relying on this is buggy. Note also, that fix "works"
5346 * only in this artificial test. Insert some normal data between A and B and we will
5347 * decline of BSD again. Verdict: it is better to remove to trap
5348 * buggy users.
5349 */
5350 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
5351 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
5352 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
5353 tp->copied_seq++;
5354 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
5355 __skb_unlink(skb, &sk->sk_receive_queue);
5356 __kfree_skb(skb);
5357 }
5358 }
5359
5360 tp->urg_data = TCP_URG_NOTYET;
5361 WRITE_ONCE(tp->urg_seq, ptr);
5362
5363 /* Disable header prediction. */
5364 tp->pred_flags = 0;
5365}
5366
5367/* This is the 'fast' part of urgent handling. */
5368static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th)
5369{
5370 struct tcp_sock *tp = tcp_sk(sk);
5371
5372 /* Check if we get a new urgent pointer - normally not. */
5373 if (th->urg)
5374 tcp_check_urg(sk, th);
5375
5376 /* Do we wait for any urgent data? - normally not... */
5377 if (tp->urg_data == TCP_URG_NOTYET) {
5378 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
5379 th->syn;
5380
5381 /* Is the urgent pointer pointing into this packet? */
5382 if (ptr < skb->len) {
5383 u8 tmp;
5384 if (skb_copy_bits(skb, ptr, &tmp, 1))
5385 BUG();
5386 tp->urg_data = TCP_URG_VALID | tmp;
5387 if (!sock_flag(sk, SOCK_DEAD))
5388 sk->sk_data_ready(sk);
5389 }
5390 }
5391}
5392
5393/* Accept RST for rcv_nxt - 1 after a FIN.
5394 * When tcp connections are abruptly terminated from Mac OSX (via ^C), a
5395 * FIN is sent followed by a RST packet. The RST is sent with the same
5396 * sequence number as the FIN, and thus according to RFC 5961 a challenge
5397 * ACK should be sent. However, Mac OSX rate limits replies to challenge
5398 * ACKs on the closed socket. In addition middleboxes can drop either the
5399 * challenge ACK or a subsequent RST.
5400 */
5401static bool tcp_reset_check(const struct sock *sk, const struct sk_buff *skb)
5402{
5403 struct tcp_sock *tp = tcp_sk(sk);
5404
5405 return unlikely(TCP_SKB_CB(skb)->seq == (tp->rcv_nxt - 1) &&
5406 (1 << sk->sk_state) & (TCPF_CLOSE_WAIT | TCPF_LAST_ACK |
5407 TCPF_CLOSING));
5408}
5409
5410/* Does PAWS and seqno based validation of an incoming segment, flags will
5411 * play significant role here.
5412 */
5413static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
5414 const struct tcphdr *th, int syn_inerr)
5415{
5416 struct tcp_sock *tp = tcp_sk(sk);
5417 bool rst_seq_match = false;
5418
5419 /* RFC1323: H1. Apply PAWS check first. */
5420 if (tcp_fast_parse_options(sock_net(sk), skb, th, tp) &&
5421 tp->rx_opt.saw_tstamp &&
5422 tcp_paws_discard(sk, skb)) {
5423 if (!th->rst) {
5424 NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
5425 if (!tcp_oow_rate_limited(sock_net(sk), skb,
5426 LINUX_MIB_TCPACKSKIPPEDPAWS,
5427 &tp->last_oow_ack_time))
5428 tcp_send_dupack(sk, skb);
5429 goto discard;
5430 }
5431 /* Reset is accepted even if it did not pass PAWS. */
5432 }
5433
5434 /* Step 1: check sequence number */
5435 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
5436 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5437 * (RST) segments are validated by checking their SEQ-fields."
5438 * And page 69: "If an incoming segment is not acceptable,
5439 * an acknowledgment should be sent in reply (unless the RST
5440 * bit is set, if so drop the segment and return)".
5441 */
5442 if (!th->rst) {
5443 if (th->syn)
5444 goto syn_challenge;
5445 if (!tcp_oow_rate_limited(sock_net(sk), skb,
5446 LINUX_MIB_TCPACKSKIPPEDSEQ,
5447 &tp->last_oow_ack_time))
5448 tcp_send_dupack(sk, skb);
5449 } else if (tcp_reset_check(sk, skb)) {
5450 tcp_reset(sk);
5451 }
5452 goto discard;
5453 }
5454
5455 /* Step 2: check RST bit */
5456 if (th->rst) {
5457 /* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a
5458 * FIN and SACK too if available):
5459 * If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or
5460 * the right-most SACK block,
5461 * then
5462 * RESET the connection
5463 * else
5464 * Send a challenge ACK
5465 */
5466 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt ||
5467 tcp_reset_check(sk, skb)) {
5468 rst_seq_match = true;
5469 } else if (tcp_is_sack(tp) && tp->rx_opt.num_sacks > 0) {
5470 struct tcp_sack_block *sp = &tp->selective_acks[0];
5471 int max_sack = sp[0].end_seq;
5472 int this_sack;
5473
5474 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;
5475 ++this_sack) {
5476 max_sack = after(sp[this_sack].end_seq,
5477 max_sack) ?
5478 sp[this_sack].end_seq : max_sack;
5479 }
5480
5481 if (TCP_SKB_CB(skb)->seq == max_sack)
5482 rst_seq_match = true;
5483 }
5484
5485 if (rst_seq_match)
5486 tcp_reset(sk);
5487 else {
5488 /* Disable TFO if RST is out-of-order
5489 * and no data has been received
5490 * for current active TFO socket
5491 */
5492 if (tp->syn_fastopen && !tp->data_segs_in &&
5493 sk->sk_state == TCP_ESTABLISHED)
5494 tcp_fastopen_active_disable(sk);
5495 tcp_send_challenge_ack(sk, skb);
5496 }
5497 goto discard;
5498 }
5499
5500 /* step 3: check security and precedence [ignored] */
5501
5502 /* step 4: Check for a SYN
5503 * RFC 5961 4.2 : Send a challenge ack
5504 */
5505 if (th->syn) {
5506syn_challenge:
5507 if (syn_inerr)
5508 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
5509 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);
5510 tcp_send_challenge_ack(sk, skb);
5511 goto discard;
5512 }
5513
5514 return true;
5515
5516discard:
5517 tcp_drop(sk, skb);
5518 return false;
5519}
5520
5521/*
5522 * TCP receive function for the ESTABLISHED state.
5523 *
5524 * It is split into a fast path and a slow path. The fast path is
5525 * disabled when:
5526 * - A zero window was announced from us - zero window probing
5527 * is only handled properly in the slow path.
5528 * - Out of order segments arrived.
5529 * - Urgent data is expected.
5530 * - There is no buffer space left
5531 * - Unexpected TCP flags/window values/header lengths are received
5532 * (detected by checking the TCP header against pred_flags)
5533 * - Data is sent in both directions. Fast path only supports pure senders
5534 * or pure receivers (this means either the sequence number or the ack
5535 * value must stay constant)
5536 * - Unexpected TCP option.
5537 *
5538 * When these conditions are not satisfied it drops into a standard
5539 * receive procedure patterned after RFC793 to handle all cases.
5540 * The first three cases are guaranteed by proper pred_flags setting,
5541 * the rest is checked inline. Fast processing is turned on in
5542 * tcp_data_queue when everything is OK.
5543 */
5544void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
5545{
5546 const struct tcphdr *th = (const struct tcphdr *)skb->data;
5547 struct tcp_sock *tp = tcp_sk(sk);
5548 unsigned int len = skb->len;
5549
5550 /* TCP congestion window tracking */
5551 trace_tcp_probe(sk, skb);
5552
5553 tcp_mstamp_refresh(tp);
5554 if (unlikely(!sk->sk_rx_dst))
5555 inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
5556 /*
5557 * Header prediction.
5558 * The code loosely follows the one in the famous
5559 * "30 instruction TCP receive" Van Jacobson mail.
5560 *
5561 * Van's trick is to deposit buffers into socket queue
5562 * on a device interrupt, to call tcp_recv function
5563 * on the receive process context and checksum and copy
5564 * the buffer to user space. smart...
5565 *
5566 * Our current scheme is not silly either but we take the
5567 * extra cost of the net_bh soft interrupt processing...
5568 * We do checksum and copy also but from device to kernel.
5569 */
5570
5571 tp->rx_opt.saw_tstamp = 0;
5572
5573 /* pred_flags is 0xS?10 << 16 + snd_wnd
5574 * if header_prediction is to be made
5575 * 'S' will always be tp->tcp_header_len >> 2
5576 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5577 * turn it off (when there are holes in the receive
5578 * space for instance)
5579 * PSH flag is ignored.
5580 */
5581
5582 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
5583 TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
5584 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
5585 int tcp_header_len = tp->tcp_header_len;
5586
5587 /* Timestamp header prediction: tcp_header_len
5588 * is automatically equal to th->doff*4 due to pred_flags
5589 * match.
5590 */
5591
5592 /* Check timestamp */
5593 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
5594 /* No? Slow path! */
5595 if (!tcp_parse_aligned_timestamp(tp, th))
5596 goto slow_path;
5597
5598 /* If PAWS failed, check it more carefully in slow path */
5599 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
5600 goto slow_path;
5601
5602 /* DO NOT update ts_recent here, if checksum fails
5603 * and timestamp was corrupted part, it will result
5604 * in a hung connection since we will drop all
5605 * future packets due to the PAWS test.
5606 */
5607 }
5608
5609 if (len <= tcp_header_len) {
5610 /* Bulk data transfer: sender */
5611 if (len == tcp_header_len) {
5612 /* Predicted packet is in window by definition.
5613 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5614 * Hence, check seq<=rcv_wup reduces to:
5615 */
5616 if (tcp_header_len ==
5617 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5618 tp->rcv_nxt == tp->rcv_wup)
5619 tcp_store_ts_recent(tp);
5620
5621 /* We know that such packets are checksummed
5622 * on entry.
5623 */
5624 tcp_ack(sk, skb, 0);
5625 __kfree_skb(skb);
5626 tcp_data_snd_check(sk);
5627 /* When receiving pure ack in fast path, update
5628 * last ts ecr directly instead of calling
5629 * tcp_rcv_rtt_measure_ts()
5630 */
5631 tp->rcv_rtt_last_tsecr = tp->rx_opt.rcv_tsecr;
5632 return;
5633 } else { /* Header too small */
5634 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
5635 goto discard;
5636 }
5637 } else {
5638 int eaten = 0;
5639 bool fragstolen = false;
5640
5641 if (tcp_checksum_complete(skb))
5642 goto csum_error;
5643
5644 if ((int)skb->truesize > sk->sk_forward_alloc)
5645 goto step5;
5646
5647 /* Predicted packet is in window by definition.
5648 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5649 * Hence, check seq<=rcv_wup reduces to:
5650 */
5651 if (tcp_header_len ==
5652 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5653 tp->rcv_nxt == tp->rcv_wup)
5654 tcp_store_ts_recent(tp);
5655
5656 tcp_rcv_rtt_measure_ts(sk, skb);
5657
5658 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPHITS);
5659
5660 /* Bulk data transfer: receiver */
5661 __skb_pull(skb, tcp_header_len);
5662 eaten = tcp_queue_rcv(sk, skb, &fragstolen);
5663
5664 tcp_event_data_recv(sk, skb);
5665
5666 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
5667 /* Well, only one small jumplet in fast path... */
5668 tcp_ack(sk, skb, FLAG_DATA);
5669 tcp_data_snd_check(sk);
5670 if (!inet_csk_ack_scheduled(sk))
5671 goto no_ack;
5672 }
5673
5674 __tcp_ack_snd_check(sk, 0);
5675no_ack:
5676 if (eaten)
5677 kfree_skb_partial(skb, fragstolen);
5678 tcp_data_ready(sk);
5679 return;
5680 }
5681 }
5682
5683slow_path:
5684 if (len < (th->doff << 2) || tcp_checksum_complete(skb))
5685 goto csum_error;
5686
5687 if (!th->ack && !th->rst && !th->syn)
5688 goto discard;
5689
5690 /*
5691 * Standard slow path.
5692 */
5693
5694 if (!tcp_validate_incoming(sk, skb, th, 1))
5695 return;
5696
5697step5:
5698 if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0)
5699 goto discard;
5700
5701 tcp_rcv_rtt_measure_ts(sk, skb);
5702
5703 /* Process urgent data. */
5704 tcp_urg(sk, skb, th);
5705
5706 /* step 7: process the segment text */
5707 tcp_data_queue(sk, skb);
5708
5709 tcp_data_snd_check(sk);
5710 tcp_ack_snd_check(sk);
5711 return;
5712
5713csum_error:
5714 TCP_INC_STATS(sock_net(sk), TCP_MIB_CSUMERRORS);
5715 TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
5716
5717discard:
5718 tcp_drop(sk, skb);
5719}
5720EXPORT_SYMBOL(tcp_rcv_established);
5721
5722void tcp_init_transfer(struct sock *sk, int bpf_op)
5723{
5724 struct inet_connection_sock *icsk = inet_csk(sk);
5725 struct tcp_sock *tp = tcp_sk(sk);
5726
5727 tcp_mtup_init(sk);
5728 icsk->icsk_af_ops->rebuild_header(sk);
5729 tcp_init_metrics(sk);
5730
5731 /* Initialize the congestion window to start the transfer.
5732 * Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
5733 * retransmitted. In light of RFC6298 more aggressive 1sec
5734 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
5735 * retransmission has occurred.
5736 */
5737 if (tp->total_retrans > 1 && tp->undo_marker)
5738 tp->snd_cwnd = 1;
5739 else
5740 tp->snd_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
5741 tp->snd_cwnd_stamp = tcp_jiffies32;
5742
5743 tcp_call_bpf(sk, bpf_op, 0, NULL);
5744 tcp_init_congestion_control(sk);
5745 tcp_init_buffer_space(sk);
5746}
5747
5748void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
5749{
5750 struct tcp_sock *tp = tcp_sk(sk);
5751 struct inet_connection_sock *icsk = inet_csk(sk);
5752
5753 tcp_set_state(sk, TCP_ESTABLISHED);
5754 icsk->icsk_ack.lrcvtime = tcp_jiffies32;
5755
5756 if (skb) {
5757 icsk->icsk_af_ops->sk_rx_dst_set(sk, skb);
5758 security_inet_conn_established(sk, skb);
5759 sk_mark_napi_id(sk, skb);
5760 }
5761
5762 tcp_init_transfer(sk, BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB);
5763
5764 /* Prevent spurious tcp_cwnd_restart() on first data
5765 * packet.
5766 */
5767 tp->lsndtime = tcp_jiffies32;
5768
5769 if (sock_flag(sk, SOCK_KEEPOPEN))
5770 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
5771
5772 if (!tp->rx_opt.snd_wscale)
5773 __tcp_fast_path_on(tp, tp->snd_wnd);
5774 else
5775 tp->pred_flags = 0;
5776}
5777
5778static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
5779 struct tcp_fastopen_cookie *cookie)
5780{
5781 struct tcp_sock *tp = tcp_sk(sk);
5782 struct sk_buff *data = tp->syn_data ? tcp_rtx_queue_head(sk) : NULL;
5783 u16 mss = tp->rx_opt.mss_clamp, try_exp = 0;
5784 bool syn_drop = false;
5785
5786 if (mss == tp->rx_opt.user_mss) {
5787 struct tcp_options_received opt;
5788
5789 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5790 tcp_clear_options(&opt);
5791 opt.user_mss = opt.mss_clamp = 0;
5792 tcp_parse_options(sock_net(sk), synack, &opt, 0, NULL);
5793 mss = opt.mss_clamp;
5794 }
5795
5796 if (!tp->syn_fastopen) {
5797 /* Ignore an unsolicited cookie */
5798 cookie->len = -1;
5799 } else if (tp->total_retrans) {
5800 /* SYN timed out and the SYN-ACK neither has a cookie nor
5801 * acknowledges data. Presumably the remote received only
5802 * the retransmitted (regular) SYNs: either the original
5803 * SYN-data or the corresponding SYN-ACK was dropped.
5804 */
5805 syn_drop = (cookie->len < 0 && data);
5806 } else if (cookie->len < 0 && !tp->syn_data) {
5807 /* We requested a cookie but didn't get it. If we did not use
5808 * the (old) exp opt format then try so next time (try_exp=1).
5809 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
5810 */
5811 try_exp = tp->syn_fastopen_exp ? 2 : 1;
5812 }
5813
5814 tcp_fastopen_cache_set(sk, mss, cookie, syn_drop, try_exp);
5815
5816 if (data) { /* Retransmit unacked data in SYN */
5817 skb_rbtree_walk_from(data) {
5818 if (__tcp_retransmit_skb(sk, data, 1))
5819 break;
5820 }
5821 tcp_rearm_rto(sk);
5822 NET_INC_STATS(sock_net(sk),
5823 LINUX_MIB_TCPFASTOPENACTIVEFAIL);
5824 return true;
5825 }
5826 tp->syn_data_acked = tp->syn_data;
5827 if (tp->syn_data_acked) {
5828 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
5829 /* SYN-data is counted as two separate packets in tcp_ack() */
5830 if (tp->delivered > 1)
5831 --tp->delivered;
5832 }
5833
5834 tcp_fastopen_add_skb(sk, synack);
5835
5836 return false;
5837}
5838
5839static void smc_check_reset_syn(struct tcp_sock *tp)
5840{
5841#if IS_ENABLED(CONFIG_SMC)
5842 if (static_branch_unlikely(&tcp_have_smc)) {
5843 if (tp->syn_smc && !tp->rx_opt.smc_ok)
5844 tp->syn_smc = 0;
5845 }
5846#endif
5847}
5848
5849static void tcp_try_undo_spurious_syn(struct sock *sk)
5850{
5851 struct tcp_sock *tp = tcp_sk(sk);
5852 u32 syn_stamp;
5853
5854 /* undo_marker is set when SYN or SYNACK times out. The timeout is
5855 * spurious if the ACK's timestamp option echo value matches the
5856 * original SYN timestamp.
5857 */
5858 syn_stamp = tp->retrans_stamp;
5859 if (tp->undo_marker && syn_stamp && tp->rx_opt.saw_tstamp &&
5860 syn_stamp == tp->rx_opt.rcv_tsecr)
5861 tp->undo_marker = 0;
5862}
5863
5864static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
5865 const struct tcphdr *th)
5866{
5867 struct inet_connection_sock *icsk = inet_csk(sk);
5868 struct tcp_sock *tp = tcp_sk(sk);
5869 struct tcp_fastopen_cookie foc = { .len = -1 };
5870 int saved_clamp = tp->rx_opt.mss_clamp;
5871 bool fastopen_fail;
5872
5873 tcp_parse_options(sock_net(sk), skb, &tp->rx_opt, 0, &foc);
5874 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
5875 tp->rx_opt.rcv_tsecr -= tp->tsoffset;
5876
5877 if (th->ack) {
5878 /* rfc793:
5879 * "If the state is SYN-SENT then
5880 * first check the ACK bit
5881 * If the ACK bit is set
5882 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5883 * a reset (unless the RST bit is set, if so drop
5884 * the segment and return)"
5885 */
5886 if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
5887 after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt))
5888 goto reset_and_undo;
5889
5890 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
5891 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
5892 tcp_time_stamp(tp))) {
5893 NET_INC_STATS(sock_net(sk),
5894 LINUX_MIB_PAWSACTIVEREJECTED);
5895 goto reset_and_undo;
5896 }
5897
5898 /* Now ACK is acceptable.
5899 *
5900 * "If the RST bit is set
5901 * If the ACK was acceptable then signal the user "error:
5902 * connection reset", drop the segment, enter CLOSED state,
5903 * delete TCB, and return."
5904 */
5905
5906 if (th->rst) {
5907 tcp_reset(sk);
5908 goto discard;
5909 }
5910
5911 /* rfc793:
5912 * "fifth, if neither of the SYN or RST bits is set then
5913 * drop the segment and return."
5914 *
5915 * See note below!
5916 * --ANK(990513)
5917 */
5918 if (!th->syn)
5919 goto discard_and_undo;
5920
5921 /* rfc793:
5922 * "If the SYN bit is on ...
5923 * are acceptable then ...
5924 * (our SYN has been ACKed), change the connection
5925 * state to ESTABLISHED..."
5926 */
5927
5928 tcp_ecn_rcv_synack(tp, th);
5929
5930 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5931 tcp_try_undo_spurious_syn(sk);
5932 tcp_ack(sk, skb, FLAG_SLOWPATH);
5933
5934 /* Ok.. it's good. Set up sequence numbers and
5935 * move to established.
5936 */
5937 WRITE_ONCE(tp->rcv_nxt, TCP_SKB_CB(skb)->seq + 1);
5938 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5939
5940 /* RFC1323: The window in SYN & SYN/ACK segments is
5941 * never scaled.
5942 */
5943 tp->snd_wnd = ntohs(th->window);
5944
5945 if (!tp->rx_opt.wscale_ok) {
5946 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
5947 tp->window_clamp = min(tp->window_clamp, 65535U);
5948 }
5949
5950 if (tp->rx_opt.saw_tstamp) {
5951 tp->rx_opt.tstamp_ok = 1;
5952 tp->tcp_header_len =
5953 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5954 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5955 tcp_store_ts_recent(tp);
5956 } else {
5957 tp->tcp_header_len = sizeof(struct tcphdr);
5958 }
5959
5960 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5961 tcp_initialize_rcv_mss(sk);
5962
5963 /* Remember, tcp_poll() does not lock socket!
5964 * Change state from SYN-SENT only after copied_seq
5965 * is initialized. */
5966 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
5967
5968 smc_check_reset_syn(tp);
5969
5970 smp_mb();
5971
5972 tcp_finish_connect(sk, skb);
5973
5974 fastopen_fail = (tp->syn_fastopen || tp->syn_data) &&
5975 tcp_rcv_fastopen_synack(sk, skb, &foc);
5976
5977 if (!sock_flag(sk, SOCK_DEAD)) {
5978 sk->sk_state_change(sk);
5979 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
5980 }
5981 if (fastopen_fail)
5982 return -1;
5983 if (sk->sk_write_pending ||
5984 icsk->icsk_accept_queue.rskq_defer_accept ||
5985 inet_csk_in_pingpong_mode(sk)) {
5986 /* Save one ACK. Data will be ready after
5987 * several ticks, if write_pending is set.
5988 *
5989 * It may be deleted, but with this feature tcpdumps
5990 * look so _wonderfully_ clever, that I was not able
5991 * to stand against the temptation 8) --ANK
5992 */
5993 inet_csk_schedule_ack(sk);
5994 tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
5995 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
5996 TCP_DELACK_MAX, TCP_RTO_MAX);
5997
5998discard:
5999 tcp_drop(sk, skb);
6000 return 0;
6001 } else {
6002 tcp_send_ack(sk);
6003 }
6004 return -1;
6005 }
6006
6007 /* No ACK in the segment */
6008
6009 if (th->rst) {
6010 /* rfc793:
6011 * "If the RST bit is set
6012 *
6013 * Otherwise (no ACK) drop the segment and return."
6014 */
6015
6016 goto discard_and_undo;
6017 }
6018
6019 /* PAWS check. */
6020 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
6021 tcp_paws_reject(&tp->rx_opt, 0))
6022 goto discard_and_undo;
6023
6024 if (th->syn) {
6025 /* We see SYN without ACK. It is attempt of
6026 * simultaneous connect with crossed SYNs.
6027 * Particularly, it can be connect to self.
6028 */
6029 tcp_set_state(sk, TCP_SYN_RECV);
6030
6031 if (tp->rx_opt.saw_tstamp) {
6032 tp->rx_opt.tstamp_ok = 1;
6033 tcp_store_ts_recent(tp);
6034 tp->tcp_header_len =
6035 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
6036 } else {
6037 tp->tcp_header_len = sizeof(struct tcphdr);
6038 }
6039
6040 WRITE_ONCE(tp->rcv_nxt, TCP_SKB_CB(skb)->seq + 1);
6041 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
6042 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
6043
6044 /* RFC1323: The window in SYN & SYN/ACK segments is
6045 * never scaled.
6046 */
6047 tp->snd_wnd = ntohs(th->window);
6048 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
6049 tp->max_window = tp->snd_wnd;
6050
6051 tcp_ecn_rcv_syn(tp, th);
6052
6053 tcp_mtup_init(sk);
6054 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
6055 tcp_initialize_rcv_mss(sk);
6056
6057 tcp_send_synack(sk);
6058#if 0
6059 /* Note, we could accept data and URG from this segment.
6060 * There are no obstacles to make this (except that we must
6061 * either change tcp_recvmsg() to prevent it from returning data
6062 * before 3WHS completes per RFC793, or employ TCP Fast Open).
6063 *
6064 * However, if we ignore data in ACKless segments sometimes,
6065 * we have no reasons to accept it sometimes.
6066 * Also, seems the code doing it in step6 of tcp_rcv_state_process
6067 * is not flawless. So, discard packet for sanity.
6068 * Uncomment this return to process the data.
6069 */
6070 return -1;
6071#else
6072 goto discard;
6073#endif
6074 }
6075 /* "fifth, if neither of the SYN or RST bits is set then
6076 * drop the segment and return."
6077 */
6078
6079discard_and_undo:
6080 tcp_clear_options(&tp->rx_opt);
6081 tp->rx_opt.mss_clamp = saved_clamp;
6082 goto discard;
6083
6084reset_and_undo:
6085 tcp_clear_options(&tp->rx_opt);
6086 tp->rx_opt.mss_clamp = saved_clamp;
6087 return 1;
6088}
6089
6090static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
6091{
6092 struct request_sock *req;
6093
6094 tcp_try_undo_loss(sk, false);
6095
6096 /* Reset rtx states to prevent spurious retransmits_timed_out() */
6097 tcp_sk(sk)->retrans_stamp = 0;
6098 inet_csk(sk)->icsk_retransmits = 0;
6099
6100 /* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,
6101 * we no longer need req so release it.
6102 */
6103 req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk,
6104 lockdep_sock_is_held(sk));
6105 reqsk_fastopen_remove(sk, req, false);
6106
6107 /* Re-arm the timer because data may have been sent out.
6108 * This is similar to the regular data transmission case
6109 * when new data has just been ack'ed.
6110 *
6111 * (TFO) - we could try to be more aggressive and
6112 * retransmitting any data sooner based on when they
6113 * are sent out.
6114 */
6115 tcp_rearm_rto(sk);
6116}
6117
6118/*
6119 * This function implements the receiving procedure of RFC 793 for
6120 * all states except ESTABLISHED and TIME_WAIT.
6121 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
6122 * address independent.
6123 */
6124
6125int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
6126{
6127 struct tcp_sock *tp = tcp_sk(sk);
6128 struct inet_connection_sock *icsk = inet_csk(sk);
6129 const struct tcphdr *th = tcp_hdr(skb);
6130 struct request_sock *req;
6131 int queued = 0;
6132 bool acceptable;
6133
6134 switch (sk->sk_state) {
6135 case TCP_CLOSE:
6136 goto discard;
6137
6138 case TCP_LISTEN:
6139 if (th->ack)
6140 return 1;
6141
6142 if (th->rst)
6143 goto discard;
6144
6145 if (th->syn) {
6146 if (th->fin)
6147 goto discard;
6148 /* It is possible that we process SYN packets from backlog,
6149 * so we need to make sure to disable BH and RCU right there.
6150 */
6151 rcu_read_lock();
6152 local_bh_disable();
6153 acceptable = icsk->icsk_af_ops->conn_request(sk, skb) >= 0;
6154 local_bh_enable();
6155 rcu_read_unlock();
6156
6157 if (!acceptable)
6158 return 1;
6159 consume_skb(skb);
6160 return 0;
6161 }
6162 goto discard;
6163
6164 case TCP_SYN_SENT:
6165 tp->rx_opt.saw_tstamp = 0;
6166 tcp_mstamp_refresh(tp);
6167 queued = tcp_rcv_synsent_state_process(sk, skb, th);
6168 if (queued >= 0)
6169 return queued;
6170
6171 /* Do step6 onward by hand. */
6172 tcp_urg(sk, skb, th);
6173 __kfree_skb(skb);
6174 tcp_data_snd_check(sk);
6175 return 0;
6176 }
6177
6178 tcp_mstamp_refresh(tp);
6179 tp->rx_opt.saw_tstamp = 0;
6180 req = rcu_dereference_protected(tp->fastopen_rsk,
6181 lockdep_sock_is_held(sk));
6182 if (req) {
6183 bool req_stolen;
6184
6185 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
6186 sk->sk_state != TCP_FIN_WAIT1);
6187
6188 if (!tcp_check_req(sk, skb, req, true, &req_stolen))
6189 goto discard;
6190 }
6191
6192 if (!th->ack && !th->rst && !th->syn)
6193 goto discard;
6194
6195 if (!tcp_validate_incoming(sk, skb, th, 0))
6196 return 0;
6197
6198 /* step 5: check the ACK field */
6199 acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
6200 FLAG_UPDATE_TS_RECENT |
6201 FLAG_NO_CHALLENGE_ACK) > 0;
6202
6203 if (!acceptable) {
6204 if (sk->sk_state == TCP_SYN_RECV)
6205 return 1; /* send one RST */
6206 tcp_send_challenge_ack(sk, skb);
6207 goto discard;
6208 }
6209 switch (sk->sk_state) {
6210 case TCP_SYN_RECV:
6211 tp->delivered++; /* SYN-ACK delivery isn't tracked in tcp_ack */
6212 if (!tp->srtt_us)
6213 tcp_synack_rtt_meas(sk, req);
6214
6215 if (req) {
6216 tcp_rcv_synrecv_state_fastopen(sk);
6217 } else {
6218 tcp_try_undo_spurious_syn(sk);
6219 tp->retrans_stamp = 0;
6220 tcp_init_transfer(sk, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB);
6221 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
6222 }
6223 smp_mb();
6224 tcp_set_state(sk, TCP_ESTABLISHED);
6225 sk->sk_state_change(sk);
6226
6227 /* Note, that this wakeup is only for marginal crossed SYN case.
6228 * Passively open sockets are not waked up, because
6229 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
6230 */
6231 if (sk->sk_socket)
6232 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
6233
6234 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
6235 tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
6236 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
6237
6238 if (tp->rx_opt.tstamp_ok)
6239 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
6240
6241 if (!inet_csk(sk)->icsk_ca_ops->cong_control)
6242 tcp_update_pacing_rate(sk);
6243
6244 /* Prevent spurious tcp_cwnd_restart() on first data packet */
6245 tp->lsndtime = tcp_jiffies32;
6246
6247 tcp_initialize_rcv_mss(sk);
6248 tcp_fast_path_on(tp);
6249 break;
6250
6251 case TCP_FIN_WAIT1: {
6252 int tmo;
6253
6254 if (req)
6255 tcp_rcv_synrecv_state_fastopen(sk);
6256
6257 if (tp->snd_una != tp->write_seq)
6258 break;
6259
6260 tcp_set_state(sk, TCP_FIN_WAIT2);
6261 sk->sk_shutdown |= SEND_SHUTDOWN;
6262
6263 sk_dst_confirm(sk);
6264
6265 if (!sock_flag(sk, SOCK_DEAD)) {
6266 /* Wake up lingering close() */
6267 sk->sk_state_change(sk);
6268 break;
6269 }
6270
6271 if (tp->linger2 < 0) {
6272 tcp_done(sk);
6273 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
6274 return 1;
6275 }
6276 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
6277 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
6278 /* Receive out of order FIN after close() */
6279 if (tp->syn_fastopen && th->fin)
6280 tcp_fastopen_active_disable(sk);
6281 tcp_done(sk);
6282 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
6283 return 1;
6284 }
6285
6286 tmo = tcp_fin_time(sk);
6287 if (tmo > TCP_TIMEWAIT_LEN) {
6288 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
6289 } else if (th->fin || sock_owned_by_user(sk)) {
6290 /* Bad case. We could lose such FIN otherwise.
6291 * It is not a big problem, but it looks confusing
6292 * and not so rare event. We still can lose it now,
6293 * if it spins in bh_lock_sock(), but it is really
6294 * marginal case.
6295 */
6296 inet_csk_reset_keepalive_timer(sk, tmo);
6297 } else {
6298 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
6299 goto discard;
6300 }
6301 break;
6302 }
6303
6304 case TCP_CLOSING:
6305 if (tp->snd_una == tp->write_seq) {
6306 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
6307 goto discard;
6308 }
6309 break;
6310
6311 case TCP_LAST_ACK:
6312 if (tp->snd_una == tp->write_seq) {
6313 tcp_update_metrics(sk);
6314 tcp_done(sk);
6315 goto discard;
6316 }
6317 break;
6318 }
6319
6320 /* step 6: check the URG bit */
6321 tcp_urg(sk, skb, th);
6322
6323 /* step 7: process the segment text */
6324 switch (sk->sk_state) {
6325 case TCP_CLOSE_WAIT:
6326 case TCP_CLOSING:
6327 case TCP_LAST_ACK:
6328 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
6329 break;
6330 /* fall through */
6331 case TCP_FIN_WAIT1:
6332 case TCP_FIN_WAIT2:
6333 /* RFC 793 says to queue data in these states,
6334 * RFC 1122 says we MUST send a reset.
6335 * BSD 4.4 also does reset.
6336 */
6337 if (sk->sk_shutdown & RCV_SHUTDOWN) {
6338 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
6339 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
6340 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
6341 tcp_reset(sk);
6342 return 1;
6343 }
6344 }
6345 /* Fall through */
6346 case TCP_ESTABLISHED:
6347 tcp_data_queue(sk, skb);
6348 queued = 1;
6349 break;
6350 }
6351
6352 /* tcp_data could move socket to TIME-WAIT */
6353 if (sk->sk_state != TCP_CLOSE) {
6354 tcp_data_snd_check(sk);
6355 tcp_ack_snd_check(sk);
6356 }
6357
6358 if (!queued) {
6359discard:
6360 tcp_drop(sk, skb);
6361 }
6362 return 0;
6363}
6364EXPORT_SYMBOL(tcp_rcv_state_process);
6365
6366static inline void pr_drop_req(struct request_sock *req, __u16 port, int family)
6367{
6368 struct inet_request_sock *ireq = inet_rsk(req);
6369
6370 if (family == AF_INET)
6371 net_dbg_ratelimited("drop open request from %pI4/%u\n",
6372 &ireq->ir_rmt_addr, port);
6373#if IS_ENABLED(CONFIG_IPV6)
6374 else if (family == AF_INET6)
6375 net_dbg_ratelimited("drop open request from %pI6/%u\n",
6376 &ireq->ir_v6_rmt_addr, port);
6377#endif
6378}
6379
6380/* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
6381 *
6382 * If we receive a SYN packet with these bits set, it means a
6383 * network is playing bad games with TOS bits. In order to
6384 * avoid possible false congestion notifications, we disable
6385 * TCP ECN negotiation.
6386 *
6387 * Exception: tcp_ca wants ECN. This is required for DCTCP
6388 * congestion control: Linux DCTCP asserts ECT on all packets,
6389 * including SYN, which is most optimal solution; however,
6390 * others, such as FreeBSD do not.
6391 *
6392 * Exception: At least one of the reserved bits of the TCP header (th->res1) is
6393 * set, indicating the use of a future TCP extension (such as AccECN). See
6394 * RFC8311 §4.3 which updates RFC3168 to allow the development of such
6395 * extensions.
6396 */
6397static void tcp_ecn_create_request(struct request_sock *req,
6398 const struct sk_buff *skb,
6399 const struct sock *listen_sk,
6400 const struct dst_entry *dst)
6401{
6402 const struct tcphdr *th = tcp_hdr(skb);
6403 const struct net *net = sock_net(listen_sk);
6404 bool th_ecn = th->ece && th->cwr;
6405 bool ect, ecn_ok;
6406 u32 ecn_ok_dst;
6407
6408 if (!th_ecn)
6409 return;
6410
6411 ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield);
6412 ecn_ok_dst = dst_feature(dst, DST_FEATURE_ECN_MASK);
6413 ecn_ok = net->ipv4.sysctl_tcp_ecn || ecn_ok_dst;
6414
6415 if (((!ect || th->res1) && ecn_ok) || tcp_ca_needs_ecn(listen_sk) ||
6416 (ecn_ok_dst & DST_FEATURE_ECN_CA) ||
6417 tcp_bpf_ca_needs_ecn((struct sock *)req))
6418 inet_rsk(req)->ecn_ok = 1;
6419}
6420
6421static void tcp_openreq_init(struct request_sock *req,
6422 const struct tcp_options_received *rx_opt,
6423 struct sk_buff *skb, const struct sock *sk)
6424{
6425 struct inet_request_sock *ireq = inet_rsk(req);
6426
6427 req->rsk_rcv_wnd = 0; /* So that tcp_send_synack() knows! */
6428 req->cookie_ts = 0;
6429 tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
6430 tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
6431 tcp_rsk(req)->snt_synack = 0;
6432 tcp_rsk(req)->last_oow_ack_time = 0;
6433 req->mss = rx_opt->mss_clamp;
6434 req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
6435 ireq->tstamp_ok = rx_opt->tstamp_ok;
6436 ireq->sack_ok = rx_opt->sack_ok;
6437 ireq->snd_wscale = rx_opt->snd_wscale;
6438 ireq->wscale_ok = rx_opt->wscale_ok;
6439 ireq->acked = 0;
6440 ireq->ecn_ok = 0;
6441 ireq->ir_rmt_port = tcp_hdr(skb)->source;
6442 ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
6443 ireq->ir_mark = inet_request_mark(sk, skb);
6444#if IS_ENABLED(CONFIG_SMC)
6445 ireq->smc_ok = rx_opt->smc_ok;
6446#endif
6447}
6448
6449struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
6450 struct sock *sk_listener,
6451 bool attach_listener)
6452{
6453 struct request_sock *req = reqsk_alloc(ops, sk_listener,
6454 attach_listener);
6455
6456 if (req) {
6457 struct inet_request_sock *ireq = inet_rsk(req);
6458
6459 ireq->ireq_opt = NULL;
6460#if IS_ENABLED(CONFIG_IPV6)
6461 ireq->pktopts = NULL;
6462#endif
6463 atomic64_set(&ireq->ir_cookie, 0);
6464 ireq->ireq_state = TCP_NEW_SYN_RECV;
6465 write_pnet(&ireq->ireq_net, sock_net(sk_listener));
6466 ireq->ireq_family = sk_listener->sk_family;
6467 }
6468
6469 return req;
6470}
6471EXPORT_SYMBOL(inet_reqsk_alloc);
6472
6473/*
6474 * Return true if a syncookie should be sent
6475 */
6476static bool tcp_syn_flood_action(const struct sock *sk, const char *proto)
6477{
6478 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
6479 const char *msg = "Dropping request";
6480 bool want_cookie = false;
6481 struct net *net = sock_net(sk);
6482
6483#ifdef CONFIG_SYN_COOKIES
6484 if (net->ipv4.sysctl_tcp_syncookies) {
6485 msg = "Sending cookies";
6486 want_cookie = true;
6487 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDOCOOKIES);
6488 } else
6489#endif
6490 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
6491
6492 if (!queue->synflood_warned &&
6493 net->ipv4.sysctl_tcp_syncookies != 2 &&
6494 xchg(&queue->synflood_warned, 1) == 0)
6495 net_info_ratelimited("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
6496 proto, sk->sk_num, msg);
6497
6498 return want_cookie;
6499}
6500
6501static void tcp_reqsk_record_syn(const struct sock *sk,
6502 struct request_sock *req,
6503 const struct sk_buff *skb)
6504{
6505 if (tcp_sk(sk)->save_syn) {
6506 u32 len = skb_network_header_len(skb) + tcp_hdrlen(skb);
6507 u32 *copy;
6508
6509 copy = kmalloc(len + sizeof(u32), GFP_ATOMIC);
6510 if (copy) {
6511 copy[0] = len;
6512 memcpy(©[1], skb_network_header(skb), len);
6513 req->saved_syn = copy;
6514 }
6515 }
6516}
6517
6518/* If a SYN cookie is required and supported, returns a clamped MSS value to be
6519 * used for SYN cookie generation.
6520 */
6521u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
6522 const struct tcp_request_sock_ops *af_ops,
6523 struct sock *sk, struct tcphdr *th)
6524{
6525 struct tcp_sock *tp = tcp_sk(sk);
6526 u16 mss;
6527
6528 if (sock_net(sk)->ipv4.sysctl_tcp_syncookies != 2 &&
6529 !inet_csk_reqsk_queue_is_full(sk))
6530 return 0;
6531
6532 if (!tcp_syn_flood_action(sk, rsk_ops->slab_name))
6533 return 0;
6534
6535 if (sk_acceptq_is_full(sk)) {
6536 NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
6537 return 0;
6538 }
6539
6540 mss = tcp_parse_mss_option(th, tp->rx_opt.user_mss);
6541 if (!mss)
6542 mss = af_ops->mss_clamp;
6543
6544 return mss;
6545}
6546EXPORT_SYMBOL_GPL(tcp_get_syncookie_mss);
6547
6548int tcp_conn_request(struct request_sock_ops *rsk_ops,
6549 const struct tcp_request_sock_ops *af_ops,
6550 struct sock *sk, struct sk_buff *skb)
6551{
6552 struct tcp_fastopen_cookie foc = { .len = -1 };
6553 __u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
6554 struct tcp_options_received tmp_opt;
6555 struct tcp_sock *tp = tcp_sk(sk);
6556 struct net *net = sock_net(sk);
6557 struct sock *fastopen_sk = NULL;
6558 struct request_sock *req;
6559 bool want_cookie = false;
6560 struct dst_entry *dst;
6561 struct flowi fl;
6562
6563 /* TW buckets are converted to open requests without
6564 * limitations, they conserve resources and peer is
6565 * evidently real one.
6566 */
6567 if ((net->ipv4.sysctl_tcp_syncookies == 2 ||
6568 inet_csk_reqsk_queue_is_full(sk)) && !isn) {
6569 want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name);
6570 if (!want_cookie)
6571 goto drop;
6572 }
6573
6574 if (sk_acceptq_is_full(sk)) {
6575 NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
6576 goto drop;
6577 }
6578
6579 req = inet_reqsk_alloc(rsk_ops, sk, !want_cookie);
6580 if (!req)
6581 goto drop;
6582
6583 tcp_rsk(req)->af_specific = af_ops;
6584 tcp_rsk(req)->ts_off = 0;
6585
6586 tcp_clear_options(&tmp_opt);
6587 tmp_opt.mss_clamp = af_ops->mss_clamp;
6588 tmp_opt.user_mss = tp->rx_opt.user_mss;
6589 tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0,
6590 want_cookie ? NULL : &foc);
6591
6592 if (want_cookie && !tmp_opt.saw_tstamp)
6593 tcp_clear_options(&tmp_opt);
6594
6595 if (IS_ENABLED(CONFIG_SMC) && want_cookie)
6596 tmp_opt.smc_ok = 0;
6597
6598 tmp_opt.tstamp_ok = tmp_opt.saw_tstamp;
6599 tcp_openreq_init(req, &tmp_opt, skb, sk);
6600 inet_rsk(req)->no_srccheck = inet_sk(sk)->transparent;
6601
6602 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
6603 inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb);
6604
6605 af_ops->init_req(req, sk, skb);
6606
6607 if (security_inet_conn_request(sk, skb, req))
6608 goto drop_and_free;
6609
6610 if (tmp_opt.tstamp_ok)
6611 tcp_rsk(req)->ts_off = af_ops->init_ts_off(net, skb);
6612
6613 dst = af_ops->route_req(sk, &fl, req);
6614 if (!dst)
6615 goto drop_and_free;
6616
6617 if (!want_cookie && !isn) {
6618 /* Kill the following clause, if you dislike this way. */
6619 if (!net->ipv4.sysctl_tcp_syncookies &&
6620 (net->ipv4.sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
6621 (net->ipv4.sysctl_max_syn_backlog >> 2)) &&
6622 !tcp_peer_is_proven(req, dst)) {
6623 /* Without syncookies last quarter of
6624 * backlog is filled with destinations,
6625 * proven to be alive.
6626 * It means that we continue to communicate
6627 * to destinations, already remembered
6628 * to the moment of synflood.
6629 */
6630 pr_drop_req(req, ntohs(tcp_hdr(skb)->source),
6631 rsk_ops->family);
6632 goto drop_and_release;
6633 }
6634
6635 isn = af_ops->init_seq(skb);
6636 }
6637
6638 tcp_ecn_create_request(req, skb, sk, dst);
6639
6640 if (want_cookie) {
6641 isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
6642 req->cookie_ts = tmp_opt.tstamp_ok;
6643 if (!tmp_opt.tstamp_ok)
6644 inet_rsk(req)->ecn_ok = 0;
6645 }
6646
6647 tcp_rsk(req)->snt_isn = isn;
6648 tcp_rsk(req)->txhash = net_tx_rndhash();
6649 tcp_openreq_init_rwin(req, sk, dst);
6650 sk_rx_queue_set(req_to_sk(req), skb);
6651 if (!want_cookie) {
6652 tcp_reqsk_record_syn(sk, req, skb);
6653 fastopen_sk = tcp_try_fastopen(sk, skb, req, &foc, dst);
6654 }
6655 if (fastopen_sk) {
6656 af_ops->send_synack(fastopen_sk, dst, &fl, req,
6657 &foc, TCP_SYNACK_FASTOPEN);
6658 /* Add the child socket directly into the accept queue */
6659 if (!inet_csk_reqsk_queue_add(sk, req, fastopen_sk)) {
6660 reqsk_fastopen_remove(fastopen_sk, req, false);
6661 bh_unlock_sock(fastopen_sk);
6662 sock_put(fastopen_sk);
6663 goto drop_and_free;
6664 }
6665 sk->sk_data_ready(sk);
6666 bh_unlock_sock(fastopen_sk);
6667 sock_put(fastopen_sk);
6668 } else {
6669 tcp_rsk(req)->tfo_listener = false;
6670 if (!want_cookie)
6671 inet_csk_reqsk_queue_hash_add(sk, req,
6672 tcp_timeout_init((struct sock *)req));
6673 af_ops->send_synack(sk, dst, &fl, req, &foc,
6674 !want_cookie ? TCP_SYNACK_NORMAL :
6675 TCP_SYNACK_COOKIE);
6676 if (want_cookie) {
6677 reqsk_free(req);
6678 return 0;
6679 }
6680 }
6681 reqsk_put(req);
6682 return 0;
6683
6684drop_and_release:
6685 dst_release(dst);
6686drop_and_free:
6687 __reqsk_free(req);
6688drop:
6689 tcp_listendrop(sk);
6690 return 0;
6691}
6692EXPORT_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#include <linux/mm.h>
65#include <linux/slab.h>
66#include <linux/module.h>
67#include <linux/sysctl.h>
68#include <linux/kernel.h>
69#include <net/dst.h>
70#include <net/tcp.h>
71#include <net/inet_common.h>
72#include <linux/ipsec.h>
73#include <asm/unaligned.h>
74#include <net/netdma.h>
75
76int sysctl_tcp_timestamps __read_mostly = 1;
77int sysctl_tcp_window_scaling __read_mostly = 1;
78int sysctl_tcp_sack __read_mostly = 1;
79int sysctl_tcp_fack __read_mostly = 1;
80int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
81EXPORT_SYMBOL(sysctl_tcp_reordering);
82int sysctl_tcp_ecn __read_mostly = 2;
83EXPORT_SYMBOL(sysctl_tcp_ecn);
84int sysctl_tcp_dsack __read_mostly = 1;
85int sysctl_tcp_app_win __read_mostly = 31;
86int sysctl_tcp_adv_win_scale __read_mostly = 2;
87EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
88
89int sysctl_tcp_stdurg __read_mostly;
90int sysctl_tcp_rfc1337 __read_mostly;
91int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
92int sysctl_tcp_frto __read_mostly = 2;
93int sysctl_tcp_frto_response __read_mostly;
94int sysctl_tcp_nometrics_save __read_mostly;
95
96int sysctl_tcp_thin_dupack __read_mostly;
97
98int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
99int sysctl_tcp_abc __read_mostly;
100
101#define FLAG_DATA 0x01 /* Incoming frame contained data. */
102#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
103#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
104#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
105#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
106#define FLAG_DATA_SACKED 0x20 /* New SACK. */
107#define FLAG_ECE 0x40 /* ECE in this ACK */
108#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
109#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
110#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
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_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
114#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
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#define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
121
122#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
123#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
124
125/* Adapt the MSS value used to make delayed ack decision to the
126 * real world.
127 */
128static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
129{
130 struct inet_connection_sock *icsk = inet_csk(sk);
131 const unsigned int lss = icsk->icsk_ack.last_seg_size;
132 unsigned int len;
133
134 icsk->icsk_ack.last_seg_size = 0;
135
136 /* skb->len may jitter because of SACKs, even if peer
137 * sends good full-sized frames.
138 */
139 len = skb_shinfo(skb)->gso_size ? : skb->len;
140 if (len >= icsk->icsk_ack.rcv_mss) {
141 icsk->icsk_ack.rcv_mss = len;
142 } else {
143 /* Otherwise, we make more careful check taking into account,
144 * that SACKs block is variable.
145 *
146 * "len" is invariant segment length, including TCP header.
147 */
148 len += skb->data - skb_transport_header(skb);
149 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) ||
150 /* If PSH is not set, packet should be
151 * full sized, provided peer TCP is not badly broken.
152 * This observation (if it is correct 8)) allows
153 * to handle super-low mtu links fairly.
154 */
155 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
156 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) {
157 /* Subtract also invariant (if peer is RFC compliant),
158 * tcp header plus fixed timestamp option length.
159 * Resulting "len" is MSS free of SACK jitter.
160 */
161 len -= tcp_sk(sk)->tcp_header_len;
162 icsk->icsk_ack.last_seg_size = len;
163 if (len == lss) {
164 icsk->icsk_ack.rcv_mss = len;
165 return;
166 }
167 }
168 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
169 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
170 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
171 }
172}
173
174static void tcp_incr_quickack(struct sock *sk)
175{
176 struct inet_connection_sock *icsk = inet_csk(sk);
177 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
178
179 if (quickacks == 0)
180 quickacks = 2;
181 if (quickacks > icsk->icsk_ack.quick)
182 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
183}
184
185static void tcp_enter_quickack_mode(struct sock *sk)
186{
187 struct inet_connection_sock *icsk = inet_csk(sk);
188 tcp_incr_quickack(sk);
189 icsk->icsk_ack.pingpong = 0;
190 icsk->icsk_ack.ato = TCP_ATO_MIN;
191}
192
193/* Send ACKs quickly, if "quick" count is not exhausted
194 * and the session is not interactive.
195 */
196
197static inline int tcp_in_quickack_mode(const struct sock *sk)
198{
199 const struct inet_connection_sock *icsk = inet_csk(sk);
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, 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, struct sk_buff *skb)
221{
222 if (tp->ecn_flags & TCP_ECN_OK) {
223 if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags))
224 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
225 /* Funny extension: if ECT is not set on a segment,
226 * it is surely retransmit. It is not in ECN RFC,
227 * but Linux follows this rule. */
228 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags)))
229 tcp_enter_quickack_mode((struct sock *)tp);
230 }
231}
232
233static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, struct tcphdr *th)
234{
235 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
236 tp->ecn_flags &= ~TCP_ECN_OK;
237}
238
239static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, struct tcphdr *th)
240{
241 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
242 tp->ecn_flags &= ~TCP_ECN_OK;
243}
244
245static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th)
246{
247 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
248 return 1;
249 return 0;
250}
251
252/* Buffer size and advertised window tuning.
253 *
254 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
255 */
256
257static void tcp_fixup_sndbuf(struct sock *sk)
258{
259 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
260 sizeof(struct sk_buff);
261
262 if (sk->sk_sndbuf < 3 * sndmem) {
263 sk->sk_sndbuf = 3 * sndmem;
264 if (sk->sk_sndbuf > sysctl_tcp_wmem[2])
265 sk->sk_sndbuf = sysctl_tcp_wmem[2];
266 }
267}
268
269/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
270 *
271 * All tcp_full_space() is split to two parts: "network" buffer, allocated
272 * forward and advertised in receiver window (tp->rcv_wnd) and
273 * "application buffer", required to isolate scheduling/application
274 * latencies from network.
275 * window_clamp is maximal advertised window. It can be less than
276 * tcp_full_space(), in this case tcp_full_space() - window_clamp
277 * is reserved for "application" buffer. The less window_clamp is
278 * the smoother our behaviour from viewpoint of network, but the lower
279 * throughput and the higher sensitivity of the connection to losses. 8)
280 *
281 * rcv_ssthresh is more strict window_clamp used at "slow start"
282 * phase to predict further behaviour of this connection.
283 * It is used for two goals:
284 * - to enforce header prediction at sender, even when application
285 * requires some significant "application buffer". It is check #1.
286 * - to prevent pruning of receive queue because of misprediction
287 * of receiver window. Check #2.
288 *
289 * The scheme does not work when sender sends good segments opening
290 * window and then starts to feed us spaghetti. But it should work
291 * in common situations. Otherwise, we have to rely on queue collapsing.
292 */
293
294/* Slow part of check#2. */
295static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb)
296{
297 struct tcp_sock *tp = tcp_sk(sk);
298 /* Optimize this! */
299 int truesize = tcp_win_from_space(skb->truesize) >> 1;
300 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1;
301
302 while (tp->rcv_ssthresh <= window) {
303 if (truesize <= skb->len)
304 return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
305
306 truesize >>= 1;
307 window >>= 1;
308 }
309 return 0;
310}
311
312static void tcp_grow_window(struct sock *sk, struct sk_buff *skb)
313{
314 struct tcp_sock *tp = tcp_sk(sk);
315
316 /* Check #1 */
317 if (tp->rcv_ssthresh < tp->window_clamp &&
318 (int)tp->rcv_ssthresh < tcp_space(sk) &&
319 !tcp_memory_pressure) {
320 int incr;
321
322 /* Check #2. Increase window, if skb with such overhead
323 * will fit to rcvbuf in future.
324 */
325 if (tcp_win_from_space(skb->truesize) <= skb->len)
326 incr = 2 * tp->advmss;
327 else
328 incr = __tcp_grow_window(sk, skb);
329
330 if (incr) {
331 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr,
332 tp->window_clamp);
333 inet_csk(sk)->icsk_ack.quick |= 1;
334 }
335 }
336}
337
338/* 3. Tuning rcvbuf, when connection enters established state. */
339
340static void tcp_fixup_rcvbuf(struct sock *sk)
341{
342 struct tcp_sock *tp = tcp_sk(sk);
343 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
344
345 /* Try to select rcvbuf so that 4 mss-sized segments
346 * will fit to window and corresponding skbs will fit to our rcvbuf.
347 * (was 3; 4 is minimum to allow fast retransmit to work.)
348 */
349 while (tcp_win_from_space(rcvmem) < tp->advmss)
350 rcvmem += 128;
351 if (sk->sk_rcvbuf < 4 * rcvmem)
352 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
353}
354
355/* 4. Try to fixup all. It is made immediately after connection enters
356 * established state.
357 */
358static void tcp_init_buffer_space(struct sock *sk)
359{
360 struct tcp_sock *tp = tcp_sk(sk);
361 int maxwin;
362
363 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
364 tcp_fixup_rcvbuf(sk);
365 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
366 tcp_fixup_sndbuf(sk);
367
368 tp->rcvq_space.space = tp->rcv_wnd;
369
370 maxwin = tcp_full_space(sk);
371
372 if (tp->window_clamp >= maxwin) {
373 tp->window_clamp = maxwin;
374
375 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
376 tp->window_clamp = max(maxwin -
377 (maxwin >> sysctl_tcp_app_win),
378 4 * tp->advmss);
379 }
380
381 /* Force reservation of one segment. */
382 if (sysctl_tcp_app_win &&
383 tp->window_clamp > 2 * tp->advmss &&
384 tp->window_clamp + tp->advmss > maxwin)
385 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
386
387 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
388 tp->snd_cwnd_stamp = tcp_time_stamp;
389}
390
391/* 5. Recalculate window clamp after socket hit its memory bounds. */
392static void tcp_clamp_window(struct sock *sk)
393{
394 struct tcp_sock *tp = tcp_sk(sk);
395 struct inet_connection_sock *icsk = inet_csk(sk);
396
397 icsk->icsk_ack.quick = 0;
398
399 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
400 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
401 !tcp_memory_pressure &&
402 atomic_long_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
403 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
404 sysctl_tcp_rmem[2]);
405 }
406 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
407 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
408}
409
410/* Initialize RCV_MSS value.
411 * RCV_MSS is an our guess about MSS used by the peer.
412 * We haven't any direct information about the MSS.
413 * It's better to underestimate the RCV_MSS rather than overestimate.
414 * Overestimations make us ACKing less frequently than needed.
415 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
416 */
417void tcp_initialize_rcv_mss(struct sock *sk)
418{
419 struct tcp_sock *tp = tcp_sk(sk);
420 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
421
422 hint = min(hint, tp->rcv_wnd / 2);
423 hint = min(hint, TCP_MSS_DEFAULT);
424 hint = max(hint, TCP_MIN_MSS);
425
426 inet_csk(sk)->icsk_ack.rcv_mss = hint;
427}
428EXPORT_SYMBOL(tcp_initialize_rcv_mss);
429
430/* Receiver "autotuning" code.
431 *
432 * The algorithm for RTT estimation w/o timestamps is based on
433 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
434 * <http://public.lanl.gov/radiant/pubs.html#DRS>
435 *
436 * More detail on this code can be found at
437 * <http://staff.psc.edu/jheffner/>,
438 * though this reference is out of date. A new paper
439 * is pending.
440 */
441static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
442{
443 u32 new_sample = tp->rcv_rtt_est.rtt;
444 long m = sample;
445
446 if (m == 0)
447 m = 1;
448
449 if (new_sample != 0) {
450 /* If we sample in larger samples in the non-timestamp
451 * case, we could grossly overestimate the RTT especially
452 * with chatty applications or bulk transfer apps which
453 * are stalled on filesystem I/O.
454 *
455 * Also, since we are only going for a minimum in the
456 * non-timestamp case, we do not smooth things out
457 * else with timestamps disabled convergence takes too
458 * long.
459 */
460 if (!win_dep) {
461 m -= (new_sample >> 3);
462 new_sample += m;
463 } else if (m < new_sample)
464 new_sample = m << 3;
465 } else {
466 /* No previous measure. */
467 new_sample = m << 3;
468 }
469
470 if (tp->rcv_rtt_est.rtt != new_sample)
471 tp->rcv_rtt_est.rtt = new_sample;
472}
473
474static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
475{
476 if (tp->rcv_rtt_est.time == 0)
477 goto new_measure;
478 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
479 return;
480 tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1);
481
482new_measure:
483 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
484 tp->rcv_rtt_est.time = tcp_time_stamp;
485}
486
487static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
488 const struct sk_buff *skb)
489{
490 struct tcp_sock *tp = tcp_sk(sk);
491 if (tp->rx_opt.rcv_tsecr &&
492 (TCP_SKB_CB(skb)->end_seq -
493 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
494 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
495}
496
497/*
498 * This function should be called every time data is copied to user space.
499 * It calculates the appropriate TCP receive buffer space.
500 */
501void tcp_rcv_space_adjust(struct sock *sk)
502{
503 struct tcp_sock *tp = tcp_sk(sk);
504 int time;
505 int space;
506
507 if (tp->rcvq_space.time == 0)
508 goto new_measure;
509
510 time = tcp_time_stamp - tp->rcvq_space.time;
511 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
512 return;
513
514 space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
515
516 space = max(tp->rcvq_space.space, space);
517
518 if (tp->rcvq_space.space != space) {
519 int rcvmem;
520
521 tp->rcvq_space.space = space;
522
523 if (sysctl_tcp_moderate_rcvbuf &&
524 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
525 int new_clamp = space;
526
527 /* Receive space grows, normalize in order to
528 * take into account packet headers and sk_buff
529 * structure overhead.
530 */
531 space /= tp->advmss;
532 if (!space)
533 space = 1;
534 rcvmem = (tp->advmss + MAX_TCP_HEADER +
535 16 + sizeof(struct sk_buff));
536 while (tcp_win_from_space(rcvmem) < tp->advmss)
537 rcvmem += 128;
538 space *= rcvmem;
539 space = min(space, sysctl_tcp_rmem[2]);
540 if (space > sk->sk_rcvbuf) {
541 sk->sk_rcvbuf = space;
542
543 /* Make the window clamp follow along. */
544 tp->window_clamp = new_clamp;
545 }
546 }
547 }
548
549new_measure:
550 tp->rcvq_space.seq = tp->copied_seq;
551 tp->rcvq_space.time = tcp_time_stamp;
552}
553
554/* There is something which you must keep in mind when you analyze the
555 * behavior of the tp->ato delayed ack timeout interval. When a
556 * connection starts up, we want to ack as quickly as possible. The
557 * problem is that "good" TCP's do slow start at the beginning of data
558 * transmission. The means that until we send the first few ACK's the
559 * sender will sit on his end and only queue most of his data, because
560 * he can only send snd_cwnd unacked packets at any given time. For
561 * each ACK we send, he increments snd_cwnd and transmits more of his
562 * queue. -DaveM
563 */
564static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
565{
566 struct tcp_sock *tp = tcp_sk(sk);
567 struct inet_connection_sock *icsk = inet_csk(sk);
568 u32 now;
569
570 inet_csk_schedule_ack(sk);
571
572 tcp_measure_rcv_mss(sk, skb);
573
574 tcp_rcv_rtt_measure(tp);
575
576 now = tcp_time_stamp;
577
578 if (!icsk->icsk_ack.ato) {
579 /* The _first_ data packet received, initialize
580 * delayed ACK engine.
581 */
582 tcp_incr_quickack(sk);
583 icsk->icsk_ack.ato = TCP_ATO_MIN;
584 } else {
585 int m = now - icsk->icsk_ack.lrcvtime;
586
587 if (m <= TCP_ATO_MIN / 2) {
588 /* The fastest case is the first. */
589 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
590 } else if (m < icsk->icsk_ack.ato) {
591 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
592 if (icsk->icsk_ack.ato > icsk->icsk_rto)
593 icsk->icsk_ack.ato = icsk->icsk_rto;
594 } else if (m > icsk->icsk_rto) {
595 /* Too long gap. Apparently sender failed to
596 * restart window, so that we send ACKs quickly.
597 */
598 tcp_incr_quickack(sk);
599 sk_mem_reclaim(sk);
600 }
601 }
602 icsk->icsk_ack.lrcvtime = now;
603
604 TCP_ECN_check_ce(tp, skb);
605
606 if (skb->len >= 128)
607 tcp_grow_window(sk, skb);
608}
609
610/* Called to compute a smoothed rtt estimate. The data fed to this
611 * routine either comes from timestamps, or from segments that were
612 * known _not_ to have been retransmitted [see Karn/Partridge
613 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
614 * piece by Van Jacobson.
615 * NOTE: the next three routines used to be one big routine.
616 * To save cycles in the RFC 1323 implementation it was better to break
617 * it up into three procedures. -- erics
618 */
619static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
620{
621 struct tcp_sock *tp = tcp_sk(sk);
622 long m = mrtt; /* RTT */
623
624 /* The following amusing code comes from Jacobson's
625 * article in SIGCOMM '88. Note that rtt and mdev
626 * are scaled versions of rtt and mean deviation.
627 * This is designed to be as fast as possible
628 * m stands for "measurement".
629 *
630 * On a 1990 paper the rto value is changed to:
631 * RTO = rtt + 4 * mdev
632 *
633 * Funny. This algorithm seems to be very broken.
634 * These formulae increase RTO, when it should be decreased, increase
635 * too slowly, when it should be increased quickly, decrease too quickly
636 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
637 * does not matter how to _calculate_ it. Seems, it was trap
638 * that VJ failed to avoid. 8)
639 */
640 if (m == 0)
641 m = 1;
642 if (tp->srtt != 0) {
643 m -= (tp->srtt >> 3); /* m is now error in rtt est */
644 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
645 if (m < 0) {
646 m = -m; /* m is now abs(error) */
647 m -= (tp->mdev >> 2); /* similar update on mdev */
648 /* This is similar to one of Eifel findings.
649 * Eifel blocks mdev updates when rtt decreases.
650 * This solution is a bit different: we use finer gain
651 * for mdev in this case (alpha*beta).
652 * Like Eifel it also prevents growth of rto,
653 * but also it limits too fast rto decreases,
654 * happening in pure Eifel.
655 */
656 if (m > 0)
657 m >>= 3;
658 } else {
659 m -= (tp->mdev >> 2); /* similar update on mdev */
660 }
661 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
662 if (tp->mdev > tp->mdev_max) {
663 tp->mdev_max = tp->mdev;
664 if (tp->mdev_max > tp->rttvar)
665 tp->rttvar = tp->mdev_max;
666 }
667 if (after(tp->snd_una, tp->rtt_seq)) {
668 if (tp->mdev_max < tp->rttvar)
669 tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2;
670 tp->rtt_seq = tp->snd_nxt;
671 tp->mdev_max = tcp_rto_min(sk);
672 }
673 } else {
674 /* no previous measure. */
675 tp->srtt = m << 3; /* take the measured time to be rtt */
676 tp->mdev = m << 1; /* make sure rto = 3*rtt */
677 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
678 tp->rtt_seq = tp->snd_nxt;
679 }
680}
681
682/* Calculate rto without backoff. This is the second half of Van Jacobson's
683 * routine referred to above.
684 */
685static inline void tcp_set_rto(struct sock *sk)
686{
687 const struct tcp_sock *tp = tcp_sk(sk);
688 /* Old crap is replaced with new one. 8)
689 *
690 * More seriously:
691 * 1. If rtt variance happened to be less 50msec, it is hallucination.
692 * It cannot be less due to utterly erratic ACK generation made
693 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
694 * to do with delayed acks, because at cwnd>2 true delack timeout
695 * is invisible. Actually, Linux-2.4 also generates erratic
696 * ACKs in some circumstances.
697 */
698 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp);
699
700 /* 2. Fixups made earlier cannot be right.
701 * If we do not estimate RTO correctly without them,
702 * all the algo is pure shit and should be replaced
703 * with correct one. It is exactly, which we pretend to do.
704 */
705
706 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
707 * guarantees that rto is higher.
708 */
709 tcp_bound_rto(sk);
710}
711
712/* Save metrics learned by this TCP session.
713 This function is called only, when TCP finishes successfully
714 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
715 */
716void tcp_update_metrics(struct sock *sk)
717{
718 struct tcp_sock *tp = tcp_sk(sk);
719 struct dst_entry *dst = __sk_dst_get(sk);
720
721 if (sysctl_tcp_nometrics_save)
722 return;
723
724 dst_confirm(dst);
725
726 if (dst && (dst->flags & DST_HOST)) {
727 const struct inet_connection_sock *icsk = inet_csk(sk);
728 int m;
729 unsigned long rtt;
730
731 if (icsk->icsk_backoff || !tp->srtt) {
732 /* This session failed to estimate rtt. Why?
733 * Probably, no packets returned in time.
734 * Reset our results.
735 */
736 if (!(dst_metric_locked(dst, RTAX_RTT)))
737 dst_metric_set(dst, RTAX_RTT, 0);
738 return;
739 }
740
741 rtt = dst_metric_rtt(dst, RTAX_RTT);
742 m = rtt - tp->srtt;
743
744 /* If newly calculated rtt larger than stored one,
745 * store new one. Otherwise, use EWMA. Remember,
746 * rtt overestimation is always better than underestimation.
747 */
748 if (!(dst_metric_locked(dst, RTAX_RTT))) {
749 if (m <= 0)
750 set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt);
751 else
752 set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3));
753 }
754
755 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
756 unsigned long var;
757 if (m < 0)
758 m = -m;
759
760 /* Scale deviation to rttvar fixed point */
761 m >>= 1;
762 if (m < tp->mdev)
763 m = tp->mdev;
764
765 var = dst_metric_rtt(dst, RTAX_RTTVAR);
766 if (m >= var)
767 var = m;
768 else
769 var -= (var - m) >> 2;
770
771 set_dst_metric_rtt(dst, RTAX_RTTVAR, var);
772 }
773
774 if (tcp_in_initial_slowstart(tp)) {
775 /* Slow start still did not finish. */
776 if (dst_metric(dst, RTAX_SSTHRESH) &&
777 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
778 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
779 dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_cwnd >> 1);
780 if (!dst_metric_locked(dst, RTAX_CWND) &&
781 tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
782 dst_metric_set(dst, RTAX_CWND, tp->snd_cwnd);
783 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
784 icsk->icsk_ca_state == TCP_CA_Open) {
785 /* Cong. avoidance phase, cwnd is reliable. */
786 if (!dst_metric_locked(dst, RTAX_SSTHRESH))
787 dst_metric_set(dst, RTAX_SSTHRESH,
788 max(tp->snd_cwnd >> 1, tp->snd_ssthresh));
789 if (!dst_metric_locked(dst, RTAX_CWND))
790 dst_metric_set(dst, RTAX_CWND,
791 (dst_metric(dst, RTAX_CWND) +
792 tp->snd_cwnd) >> 1);
793 } else {
794 /* Else slow start did not finish, cwnd is non-sense,
795 ssthresh may be also invalid.
796 */
797 if (!dst_metric_locked(dst, RTAX_CWND))
798 dst_metric_set(dst, RTAX_CWND,
799 (dst_metric(dst, RTAX_CWND) +
800 tp->snd_ssthresh) >> 1);
801 if (dst_metric(dst, RTAX_SSTHRESH) &&
802 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
803 tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH))
804 dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_ssthresh);
805 }
806
807 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
808 if (dst_metric(dst, RTAX_REORDERING) < tp->reordering &&
809 tp->reordering != sysctl_tcp_reordering)
810 dst_metric_set(dst, RTAX_REORDERING, tp->reordering);
811 }
812 }
813}
814
815__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
816{
817 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
818
819 if (!cwnd)
820 cwnd = TCP_INIT_CWND;
821 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
822}
823
824/* Set slow start threshold and cwnd not falling to slow start */
825void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
826{
827 struct tcp_sock *tp = tcp_sk(sk);
828 const struct inet_connection_sock *icsk = inet_csk(sk);
829
830 tp->prior_ssthresh = 0;
831 tp->bytes_acked = 0;
832 if (icsk->icsk_ca_state < TCP_CA_CWR) {
833 tp->undo_marker = 0;
834 if (set_ssthresh)
835 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
836 tp->snd_cwnd = min(tp->snd_cwnd,
837 tcp_packets_in_flight(tp) + 1U);
838 tp->snd_cwnd_cnt = 0;
839 tp->high_seq = tp->snd_nxt;
840 tp->snd_cwnd_stamp = tcp_time_stamp;
841 TCP_ECN_queue_cwr(tp);
842
843 tcp_set_ca_state(sk, TCP_CA_CWR);
844 }
845}
846
847/*
848 * Packet counting of FACK is based on in-order assumptions, therefore TCP
849 * disables it when reordering is detected
850 */
851static void tcp_disable_fack(struct tcp_sock *tp)
852{
853 /* RFC3517 uses different metric in lost marker => reset on change */
854 if (tcp_is_fack(tp))
855 tp->lost_skb_hint = NULL;
856 tp->rx_opt.sack_ok &= ~2;
857}
858
859/* Take a notice that peer is sending D-SACKs */
860static void tcp_dsack_seen(struct tcp_sock *tp)
861{
862 tp->rx_opt.sack_ok |= 4;
863}
864
865/* Initialize metrics on socket. */
866
867static void tcp_init_metrics(struct sock *sk)
868{
869 struct tcp_sock *tp = tcp_sk(sk);
870 struct dst_entry *dst = __sk_dst_get(sk);
871
872 if (dst == NULL)
873 goto reset;
874
875 dst_confirm(dst);
876
877 if (dst_metric_locked(dst, RTAX_CWND))
878 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
879 if (dst_metric(dst, RTAX_SSTHRESH)) {
880 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
881 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
882 tp->snd_ssthresh = tp->snd_cwnd_clamp;
883 } else {
884 /* ssthresh may have been reduced unnecessarily during.
885 * 3WHS. Restore it back to its initial default.
886 */
887 tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
888 }
889 if (dst_metric(dst, RTAX_REORDERING) &&
890 tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
891 tcp_disable_fack(tp);
892 tp->reordering = dst_metric(dst, RTAX_REORDERING);
893 }
894
895 if (dst_metric(dst, RTAX_RTT) == 0 || tp->srtt == 0)
896 goto reset;
897
898 /* Initial rtt is determined from SYN,SYN-ACK.
899 * The segment is small and rtt may appear much
900 * less than real one. Use per-dst memory
901 * to make it more realistic.
902 *
903 * A bit of theory. RTT is time passed after "normal" sized packet
904 * is sent until it is ACKed. In normal circumstances sending small
905 * packets force peer to delay ACKs and calculation is correct too.
906 * The algorithm is adaptive and, provided we follow specs, it
907 * NEVER underestimate RTT. BUT! If peer tries to make some clever
908 * tricks sort of "quick acks" for time long enough to decrease RTT
909 * to low value, and then abruptly stops to do it and starts to delay
910 * ACKs, wait for troubles.
911 */
912 if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) {
913 tp->srtt = dst_metric_rtt(dst, RTAX_RTT);
914 tp->rtt_seq = tp->snd_nxt;
915 }
916 if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) {
917 tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR);
918 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
919 }
920 tcp_set_rto(sk);
921reset:
922 if (tp->srtt == 0) {
923 /* RFC2988bis: We've failed to get a valid RTT sample from
924 * 3WHS. This is most likely due to retransmission,
925 * including spurious one. Reset the RTO back to 3secs
926 * from the more aggressive 1sec to avoid more spurious
927 * retransmission.
928 */
929 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_FALLBACK;
930 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_FALLBACK;
931 }
932 /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
933 * retransmitted. In light of RFC2988bis' more aggressive 1sec
934 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
935 * retransmission has occurred.
936 */
937 if (tp->total_retrans > 1)
938 tp->snd_cwnd = 1;
939 else
940 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
941 tp->snd_cwnd_stamp = tcp_time_stamp;
942}
943
944static void tcp_update_reordering(struct sock *sk, const int metric,
945 const int ts)
946{
947 struct tcp_sock *tp = tcp_sk(sk);
948 if (metric > tp->reordering) {
949 int mib_idx;
950
951 tp->reordering = min(TCP_MAX_REORDERING, metric);
952
953 /* This exciting event is worth to be remembered. 8) */
954 if (ts)
955 mib_idx = LINUX_MIB_TCPTSREORDER;
956 else if (tcp_is_reno(tp))
957 mib_idx = LINUX_MIB_TCPRENOREORDER;
958 else if (tcp_is_fack(tp))
959 mib_idx = LINUX_MIB_TCPFACKREORDER;
960 else
961 mib_idx = LINUX_MIB_TCPSACKREORDER;
962
963 NET_INC_STATS_BH(sock_net(sk), mib_idx);
964#if FASTRETRANS_DEBUG > 1
965 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
966 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
967 tp->reordering,
968 tp->fackets_out,
969 tp->sacked_out,
970 tp->undo_marker ? tp->undo_retrans : 0);
971#endif
972 tcp_disable_fack(tp);
973 }
974}
975
976/* This must be called before lost_out is incremented */
977static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
978{
979 if ((tp->retransmit_skb_hint == NULL) ||
980 before(TCP_SKB_CB(skb)->seq,
981 TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
982 tp->retransmit_skb_hint = skb;
983
984 if (!tp->lost_out ||
985 after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))
986 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
987}
988
989static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
990{
991 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
992 tcp_verify_retransmit_hint(tp, skb);
993
994 tp->lost_out += tcp_skb_pcount(skb);
995 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
996 }
997}
998
999static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,
1000 struct sk_buff *skb)
1001{
1002 tcp_verify_retransmit_hint(tp, skb);
1003
1004 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1005 tp->lost_out += tcp_skb_pcount(skb);
1006 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1007 }
1008}
1009
1010/* This procedure tags the retransmission queue when SACKs arrive.
1011 *
1012 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1013 * Packets in queue with these bits set are counted in variables
1014 * sacked_out, retrans_out and lost_out, correspondingly.
1015 *
1016 * Valid combinations are:
1017 * Tag InFlight Description
1018 * 0 1 - orig segment is in flight.
1019 * S 0 - nothing flies, orig reached receiver.
1020 * L 0 - nothing flies, orig lost by net.
1021 * R 2 - both orig and retransmit are in flight.
1022 * L|R 1 - orig is lost, retransmit is in flight.
1023 * S|R 1 - orig reached receiver, retrans is still in flight.
1024 * (L|S|R is logically valid, it could occur when L|R is sacked,
1025 * but it is equivalent to plain S and code short-curcuits it to S.
1026 * L|S is logically invalid, it would mean -1 packet in flight 8))
1027 *
1028 * These 6 states form finite state machine, controlled by the following events:
1029 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1030 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1031 * 3. Loss detection event of one of three flavors:
1032 * A. Scoreboard estimator decided the packet is lost.
1033 * A'. Reno "three dupacks" marks head of queue lost.
1034 * A''. Its FACK modfication, head until snd.fack is lost.
1035 * B. SACK arrives sacking data transmitted after never retransmitted
1036 * hole was sent out.
1037 * C. SACK arrives sacking SND.NXT at the moment, when the
1038 * segment was retransmitted.
1039 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1040 *
1041 * It is pleasant to note, that state diagram turns out to be commutative,
1042 * so that we are allowed not to be bothered by order of our actions,
1043 * when multiple events arrive simultaneously. (see the function below).
1044 *
1045 * Reordering detection.
1046 * --------------------
1047 * Reordering metric is maximal distance, which a packet can be displaced
1048 * in packet stream. With SACKs we can estimate it:
1049 *
1050 * 1. SACK fills old hole and the corresponding segment was not
1051 * ever retransmitted -> reordering. Alas, we cannot use it
1052 * when segment was retransmitted.
1053 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1054 * for retransmitted and already SACKed segment -> reordering..
1055 * Both of these heuristics are not used in Loss state, when we cannot
1056 * account for retransmits accurately.
1057 *
1058 * SACK block validation.
1059 * ----------------------
1060 *
1061 * SACK block range validation checks that the received SACK block fits to
1062 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1063 * Note that SND.UNA is not included to the range though being valid because
1064 * it means that the receiver is rather inconsistent with itself reporting
1065 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1066 * perfectly valid, however, in light of RFC2018 which explicitly states
1067 * that "SACK block MUST reflect the newest segment. Even if the newest
1068 * segment is going to be discarded ...", not that it looks very clever
1069 * in case of head skb. Due to potentional receiver driven attacks, we
1070 * choose to avoid immediate execution of a walk in write queue due to
1071 * reneging and defer head skb's loss recovery to standard loss recovery
1072 * procedure that will eventually trigger (nothing forbids us doing this).
1073 *
1074 * Implements also blockage to start_seq wrap-around. Problem lies in the
1075 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1076 * there's no guarantee that it will be before snd_nxt (n). The problem
1077 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1078 * wrap (s_w):
1079 *
1080 * <- outs wnd -> <- wrapzone ->
1081 * u e n u_w e_w s n_w
1082 * | | | | | | |
1083 * |<------------+------+----- TCP seqno space --------------+---------->|
1084 * ...-- <2^31 ->| |<--------...
1085 * ...---- >2^31 ------>| |<--------...
1086 *
1087 * Current code wouldn't be vulnerable but it's better still to discard such
1088 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1089 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1090 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1091 * equal to the ideal case (infinite seqno space without wrap caused issues).
1092 *
1093 * With D-SACK the lower bound is extended to cover sequence space below
1094 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1095 * again, D-SACK block must not to go across snd_una (for the same reason as
1096 * for the normal SACK blocks, explained above). But there all simplicity
1097 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1098 * fully below undo_marker they do not affect behavior in anyway and can
1099 * therefore be safely ignored. In rare cases (which are more or less
1100 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1101 * fragmentation and packet reordering past skb's retransmission. To consider
1102 * them correctly, the acceptable range must be extended even more though
1103 * the exact amount is rather hard to quantify. However, tp->max_window can
1104 * be used as an exaggerated estimate.
1105 */
1106static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
1107 u32 start_seq, u32 end_seq)
1108{
1109 /* Too far in future, or reversed (interpretation is ambiguous) */
1110 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq))
1111 return 0;
1112
1113 /* Nasty start_seq wrap-around check (see comments above) */
1114 if (!before(start_seq, tp->snd_nxt))
1115 return 0;
1116
1117 /* In outstanding window? ...This is valid exit for D-SACKs too.
1118 * start_seq == snd_una is non-sensical (see comments above)
1119 */
1120 if (after(start_seq, tp->snd_una))
1121 return 1;
1122
1123 if (!is_dsack || !tp->undo_marker)
1124 return 0;
1125
1126 /* ...Then it's D-SACK, and must reside below snd_una completely */
1127 if (after(end_seq, tp->snd_una))
1128 return 0;
1129
1130 if (!before(start_seq, tp->undo_marker))
1131 return 1;
1132
1133 /* Too old */
1134 if (!after(end_seq, tp->undo_marker))
1135 return 0;
1136
1137 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1138 * start_seq < undo_marker and end_seq >= undo_marker.
1139 */
1140 return !before(start_seq, end_seq - tp->max_window);
1141}
1142
1143/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1144 * Event "C". Later note: FACK people cheated me again 8), we have to account
1145 * for reordering! Ugly, but should help.
1146 *
1147 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1148 * less than what is now known to be received by the other end (derived from
1149 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1150 * retransmitted skbs to avoid some costly processing per ACKs.
1151 */
1152static void tcp_mark_lost_retrans(struct sock *sk)
1153{
1154 const struct inet_connection_sock *icsk = inet_csk(sk);
1155 struct tcp_sock *tp = tcp_sk(sk);
1156 struct sk_buff *skb;
1157 int cnt = 0;
1158 u32 new_low_seq = tp->snd_nxt;
1159 u32 received_upto = tcp_highest_sack_seq(tp);
1160
1161 if (!tcp_is_fack(tp) || !tp->retrans_out ||
1162 !after(received_upto, tp->lost_retrans_low) ||
1163 icsk->icsk_ca_state != TCP_CA_Recovery)
1164 return;
1165
1166 tcp_for_write_queue(skb, sk) {
1167 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
1168
1169 if (skb == tcp_send_head(sk))
1170 break;
1171 if (cnt == tp->retrans_out)
1172 break;
1173 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1174 continue;
1175
1176 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
1177 continue;
1178
1179 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1180 * constraint here (see above) but figuring out that at
1181 * least tp->reordering SACK blocks reside between ack_seq
1182 * and received_upto is not easy task to do cheaply with
1183 * the available datastructures.
1184 *
1185 * Whether FACK should check here for tp->reordering segs
1186 * in-between one could argue for either way (it would be
1187 * rather simple to implement as we could count fack_count
1188 * during the walk and do tp->fackets_out - fack_count).
1189 */
1190 if (after(received_upto, ack_seq)) {
1191 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1192 tp->retrans_out -= tcp_skb_pcount(skb);
1193
1194 tcp_skb_mark_lost_uncond_verify(tp, skb);
1195 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
1196 } else {
1197 if (before(ack_seq, new_low_seq))
1198 new_low_seq = ack_seq;
1199 cnt += tcp_skb_pcount(skb);
1200 }
1201 }
1202
1203 if (tp->retrans_out)
1204 tp->lost_retrans_low = new_low_seq;
1205}
1206
1207static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb,
1208 struct tcp_sack_block_wire *sp, int num_sacks,
1209 u32 prior_snd_una)
1210{
1211 struct tcp_sock *tp = tcp_sk(sk);
1212 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq);
1213 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq);
1214 int dup_sack = 0;
1215
1216 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) {
1217 dup_sack = 1;
1218 tcp_dsack_seen(tp);
1219 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV);
1220 } else if (num_sacks > 1) {
1221 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq);
1222 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq);
1223
1224 if (!after(end_seq_0, end_seq_1) &&
1225 !before(start_seq_0, start_seq_1)) {
1226 dup_sack = 1;
1227 tcp_dsack_seen(tp);
1228 NET_INC_STATS_BH(sock_net(sk),
1229 LINUX_MIB_TCPDSACKOFORECV);
1230 }
1231 }
1232
1233 /* D-SACK for already forgotten data... Do dumb counting. */
1234 if (dup_sack && tp->undo_marker && tp->undo_retrans &&
1235 !after(end_seq_0, prior_snd_una) &&
1236 after(end_seq_0, tp->undo_marker))
1237 tp->undo_retrans--;
1238
1239 return dup_sack;
1240}
1241
1242struct tcp_sacktag_state {
1243 int reord;
1244 int fack_count;
1245 int flag;
1246};
1247
1248/* Check if skb is fully within the SACK block. In presence of GSO skbs,
1249 * the incoming SACK may not exactly match but we can find smaller MSS
1250 * aligned portion of it that matches. Therefore we might need to fragment
1251 * which may fail and creates some hassle (caller must handle error case
1252 * returns).
1253 *
1254 * FIXME: this could be merged to shift decision code
1255 */
1256static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
1257 u32 start_seq, u32 end_seq)
1258{
1259 int in_sack, err;
1260 unsigned int pkt_len;
1261 unsigned int mss;
1262
1263 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1264 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1265
1266 if (tcp_skb_pcount(skb) > 1 && !in_sack &&
1267 after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1268 mss = tcp_skb_mss(skb);
1269 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1270
1271 if (!in_sack) {
1272 pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
1273 if (pkt_len < mss)
1274 pkt_len = mss;
1275 } else {
1276 pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
1277 if (pkt_len < mss)
1278 return -EINVAL;
1279 }
1280
1281 /* Round if necessary so that SACKs cover only full MSSes
1282 * and/or the remaining small portion (if present)
1283 */
1284 if (pkt_len > mss) {
1285 unsigned int new_len = (pkt_len / mss) * mss;
1286 if (!in_sack && new_len < pkt_len) {
1287 new_len += mss;
1288 if (new_len > skb->len)
1289 return 0;
1290 }
1291 pkt_len = new_len;
1292 }
1293 err = tcp_fragment(sk, skb, pkt_len, mss);
1294 if (err < 0)
1295 return err;
1296 }
1297
1298 return in_sack;
1299}
1300
1301static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
1302 struct tcp_sacktag_state *state,
1303 int dup_sack, int pcount)
1304{
1305 struct tcp_sock *tp = tcp_sk(sk);
1306 u8 sacked = TCP_SKB_CB(skb)->sacked;
1307 int fack_count = state->fack_count;
1308
1309 /* Account D-SACK for retransmitted packet. */
1310 if (dup_sack && (sacked & TCPCB_RETRANS)) {
1311 if (tp->undo_marker && tp->undo_retrans &&
1312 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1313 tp->undo_retrans--;
1314 if (sacked & TCPCB_SACKED_ACKED)
1315 state->reord = min(fack_count, state->reord);
1316 }
1317
1318 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1319 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1320 return sacked;
1321
1322 if (!(sacked & TCPCB_SACKED_ACKED)) {
1323 if (sacked & TCPCB_SACKED_RETRANS) {
1324 /* If the segment is not tagged as lost,
1325 * we do not clear RETRANS, believing
1326 * that retransmission is still in flight.
1327 */
1328 if (sacked & TCPCB_LOST) {
1329 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1330 tp->lost_out -= pcount;
1331 tp->retrans_out -= pcount;
1332 }
1333 } else {
1334 if (!(sacked & TCPCB_RETRANS)) {
1335 /* New sack for not retransmitted frame,
1336 * which was in hole. It is reordering.
1337 */
1338 if (before(TCP_SKB_CB(skb)->seq,
1339 tcp_highest_sack_seq(tp)))
1340 state->reord = min(fack_count,
1341 state->reord);
1342
1343 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1344 if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
1345 state->flag |= FLAG_ONLY_ORIG_SACKED;
1346 }
1347
1348 if (sacked & TCPCB_LOST) {
1349 sacked &= ~TCPCB_LOST;
1350 tp->lost_out -= pcount;
1351 }
1352 }
1353
1354 sacked |= TCPCB_SACKED_ACKED;
1355 state->flag |= FLAG_DATA_SACKED;
1356 tp->sacked_out += pcount;
1357
1358 fack_count += pcount;
1359
1360 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1361 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
1362 before(TCP_SKB_CB(skb)->seq,
1363 TCP_SKB_CB(tp->lost_skb_hint)->seq))
1364 tp->lost_cnt_hint += pcount;
1365
1366 if (fack_count > tp->fackets_out)
1367 tp->fackets_out = fack_count;
1368 }
1369
1370 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1371 * frames and clear it. undo_retrans is decreased above, L|R frames
1372 * are accounted above as well.
1373 */
1374 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
1375 sacked &= ~TCPCB_SACKED_RETRANS;
1376 tp->retrans_out -= pcount;
1377 }
1378
1379 return sacked;
1380}
1381
1382static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
1383 struct tcp_sacktag_state *state,
1384 unsigned int pcount, int shifted, int mss,
1385 int dup_sack)
1386{
1387 struct tcp_sock *tp = tcp_sk(sk);
1388 struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
1389
1390 BUG_ON(!pcount);
1391
1392 if (skb == tp->lost_skb_hint)
1393 tp->lost_cnt_hint += pcount;
1394
1395 TCP_SKB_CB(prev)->end_seq += shifted;
1396 TCP_SKB_CB(skb)->seq += shifted;
1397
1398 skb_shinfo(prev)->gso_segs += pcount;
1399 BUG_ON(skb_shinfo(skb)->gso_segs < pcount);
1400 skb_shinfo(skb)->gso_segs -= pcount;
1401
1402 /* When we're adding to gso_segs == 1, gso_size will be zero,
1403 * in theory this shouldn't be necessary but as long as DSACK
1404 * code can come after this skb later on it's better to keep
1405 * setting gso_size to something.
1406 */
1407 if (!skb_shinfo(prev)->gso_size) {
1408 skb_shinfo(prev)->gso_size = mss;
1409 skb_shinfo(prev)->gso_type = sk->sk_gso_type;
1410 }
1411
1412 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1413 if (skb_shinfo(skb)->gso_segs <= 1) {
1414 skb_shinfo(skb)->gso_size = 0;
1415 skb_shinfo(skb)->gso_type = 0;
1416 }
1417
1418 /* We discard results */
1419 tcp_sacktag_one(skb, sk, state, dup_sack, pcount);
1420
1421 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1422 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
1423
1424 if (skb->len > 0) {
1425 BUG_ON(!tcp_skb_pcount(skb));
1426 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED);
1427 return 0;
1428 }
1429
1430 /* Whole SKB was eaten :-) */
1431
1432 if (skb == tp->retransmit_skb_hint)
1433 tp->retransmit_skb_hint = prev;
1434 if (skb == tp->scoreboard_skb_hint)
1435 tp->scoreboard_skb_hint = prev;
1436 if (skb == tp->lost_skb_hint) {
1437 tp->lost_skb_hint = prev;
1438 tp->lost_cnt_hint -= tcp_skb_pcount(prev);
1439 }
1440
1441 TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(prev)->flags;
1442 if (skb == tcp_highest_sack(sk))
1443 tcp_advance_highest_sack(sk, skb);
1444
1445 tcp_unlink_write_queue(skb, sk);
1446 sk_wmem_free_skb(sk, skb);
1447
1448 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED);
1449
1450 return 1;
1451}
1452
1453/* I wish gso_size would have a bit more sane initialization than
1454 * something-or-zero which complicates things
1455 */
1456static int tcp_skb_seglen(struct sk_buff *skb)
1457{
1458 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
1459}
1460
1461/* Shifting pages past head area doesn't work */
1462static int skb_can_shift(struct sk_buff *skb)
1463{
1464 return !skb_headlen(skb) && skb_is_nonlinear(skb);
1465}
1466
1467/* Try collapsing SACK blocks spanning across multiple skbs to a single
1468 * skb.
1469 */
1470static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
1471 struct tcp_sacktag_state *state,
1472 u32 start_seq, u32 end_seq,
1473 int dup_sack)
1474{
1475 struct tcp_sock *tp = tcp_sk(sk);
1476 struct sk_buff *prev;
1477 int mss;
1478 int pcount = 0;
1479 int len;
1480 int in_sack;
1481
1482 if (!sk_can_gso(sk))
1483 goto fallback;
1484
1485 /* Normally R but no L won't result in plain S */
1486 if (!dup_sack &&
1487 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
1488 goto fallback;
1489 if (!skb_can_shift(skb))
1490 goto fallback;
1491 /* This frame is about to be dropped (was ACKed). */
1492 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1493 goto fallback;
1494
1495 /* Can only happen with delayed DSACK + discard craziness */
1496 if (unlikely(skb == tcp_write_queue_head(sk)))
1497 goto fallback;
1498 prev = tcp_write_queue_prev(sk, skb);
1499
1500 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
1501 goto fallback;
1502
1503 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1504 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1505
1506 if (in_sack) {
1507 len = skb->len;
1508 pcount = tcp_skb_pcount(skb);
1509 mss = tcp_skb_seglen(skb);
1510
1511 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1512 * drop this restriction as unnecessary
1513 */
1514 if (mss != tcp_skb_seglen(prev))
1515 goto fallback;
1516 } else {
1517 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
1518 goto noop;
1519 /* CHECKME: This is non-MSS split case only?, this will
1520 * cause skipped skbs due to advancing loop btw, original
1521 * has that feature too
1522 */
1523 if (tcp_skb_pcount(skb) <= 1)
1524 goto noop;
1525
1526 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
1527 if (!in_sack) {
1528 /* TODO: head merge to next could be attempted here
1529 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1530 * though it might not be worth of the additional hassle
1531 *
1532 * ...we can probably just fallback to what was done
1533 * previously. We could try merging non-SACKed ones
1534 * as well but it probably isn't going to buy off
1535 * because later SACKs might again split them, and
1536 * it would make skb timestamp tracking considerably
1537 * harder problem.
1538 */
1539 goto fallback;
1540 }
1541
1542 len = end_seq - TCP_SKB_CB(skb)->seq;
1543 BUG_ON(len < 0);
1544 BUG_ON(len > skb->len);
1545
1546 /* MSS boundaries should be honoured or else pcount will
1547 * severely break even though it makes things bit trickier.
1548 * Optimize common case to avoid most of the divides
1549 */
1550 mss = tcp_skb_mss(skb);
1551
1552 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1553 * drop this restriction as unnecessary
1554 */
1555 if (mss != tcp_skb_seglen(prev))
1556 goto fallback;
1557
1558 if (len == mss) {
1559 pcount = 1;
1560 } else if (len < mss) {
1561 goto noop;
1562 } else {
1563 pcount = len / mss;
1564 len = pcount * mss;
1565 }
1566 }
1567
1568 if (!skb_shift(prev, skb, len))
1569 goto fallback;
1570 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
1571 goto out;
1572
1573 /* Hole filled allows collapsing with the next as well, this is very
1574 * useful when hole on every nth skb pattern happens
1575 */
1576 if (prev == tcp_write_queue_tail(sk))
1577 goto out;
1578 skb = tcp_write_queue_next(sk, prev);
1579
1580 if (!skb_can_shift(skb) ||
1581 (skb == tcp_send_head(sk)) ||
1582 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
1583 (mss != tcp_skb_seglen(skb)))
1584 goto out;
1585
1586 len = skb->len;
1587 if (skb_shift(prev, skb, len)) {
1588 pcount += tcp_skb_pcount(skb);
1589 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
1590 }
1591
1592out:
1593 state->fack_count += pcount;
1594 return prev;
1595
1596noop:
1597 return skb;
1598
1599fallback:
1600 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
1601 return NULL;
1602}
1603
1604static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
1605 struct tcp_sack_block *next_dup,
1606 struct tcp_sacktag_state *state,
1607 u32 start_seq, u32 end_seq,
1608 int dup_sack_in)
1609{
1610 struct tcp_sock *tp = tcp_sk(sk);
1611 struct sk_buff *tmp;
1612
1613 tcp_for_write_queue_from(skb, sk) {
1614 int in_sack = 0;
1615 int dup_sack = dup_sack_in;
1616
1617 if (skb == tcp_send_head(sk))
1618 break;
1619
1620 /* queue is in-order => we can short-circuit the walk early */
1621 if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1622 break;
1623
1624 if ((next_dup != NULL) &&
1625 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) {
1626 in_sack = tcp_match_skb_to_sack(sk, skb,
1627 next_dup->start_seq,
1628 next_dup->end_seq);
1629 if (in_sack > 0)
1630 dup_sack = 1;
1631 }
1632
1633 /* skb reference here is a bit tricky to get right, since
1634 * shifting can eat and free both this skb and the next,
1635 * so not even _safe variant of the loop is enough.
1636 */
1637 if (in_sack <= 0) {
1638 tmp = tcp_shift_skb_data(sk, skb, state,
1639 start_seq, end_seq, dup_sack);
1640 if (tmp != NULL) {
1641 if (tmp != skb) {
1642 skb = tmp;
1643 continue;
1644 }
1645
1646 in_sack = 0;
1647 } else {
1648 in_sack = tcp_match_skb_to_sack(sk, skb,
1649 start_seq,
1650 end_seq);
1651 }
1652 }
1653
1654 if (unlikely(in_sack < 0))
1655 break;
1656
1657 if (in_sack) {
1658 TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk,
1659 state,
1660 dup_sack,
1661 tcp_skb_pcount(skb));
1662
1663 if (!before(TCP_SKB_CB(skb)->seq,
1664 tcp_highest_sack_seq(tp)))
1665 tcp_advance_highest_sack(sk, skb);
1666 }
1667
1668 state->fack_count += tcp_skb_pcount(skb);
1669 }
1670 return skb;
1671}
1672
1673/* Avoid all extra work that is being done by sacktag while walking in
1674 * a normal way
1675 */
1676static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
1677 struct tcp_sacktag_state *state,
1678 u32 skip_to_seq)
1679{
1680 tcp_for_write_queue_from(skb, sk) {
1681 if (skb == tcp_send_head(sk))
1682 break;
1683
1684 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
1685 break;
1686
1687 state->fack_count += tcp_skb_pcount(skb);
1688 }
1689 return skb;
1690}
1691
1692static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
1693 struct sock *sk,
1694 struct tcp_sack_block *next_dup,
1695 struct tcp_sacktag_state *state,
1696 u32 skip_to_seq)
1697{
1698 if (next_dup == NULL)
1699 return skb;
1700
1701 if (before(next_dup->start_seq, skip_to_seq)) {
1702 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq);
1703 skb = tcp_sacktag_walk(skb, sk, NULL, state,
1704 next_dup->start_seq, next_dup->end_seq,
1705 1);
1706 }
1707
1708 return skb;
1709}
1710
1711static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache)
1712{
1713 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1714}
1715
1716static int
1717tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
1718 u32 prior_snd_una)
1719{
1720 const struct inet_connection_sock *icsk = inet_csk(sk);
1721 struct tcp_sock *tp = tcp_sk(sk);
1722 unsigned char *ptr = (skb_transport_header(ack_skb) +
1723 TCP_SKB_CB(ack_skb)->sacked);
1724 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
1725 struct tcp_sack_block sp[TCP_NUM_SACKS];
1726 struct tcp_sack_block *cache;
1727 struct tcp_sacktag_state state;
1728 struct sk_buff *skb;
1729 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
1730 int used_sacks;
1731 int found_dup_sack = 0;
1732 int i, j;
1733 int first_sack_index;
1734
1735 state.flag = 0;
1736 state.reord = tp->packets_out;
1737
1738 if (!tp->sacked_out) {
1739 if (WARN_ON(tp->fackets_out))
1740 tp->fackets_out = 0;
1741 tcp_highest_sack_reset(sk);
1742 }
1743
1744 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
1745 num_sacks, prior_snd_una);
1746 if (found_dup_sack)
1747 state.flag |= FLAG_DSACKING_ACK;
1748
1749 /* Eliminate too old ACKs, but take into
1750 * account more or less fresh ones, they can
1751 * contain valid SACK info.
1752 */
1753 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
1754 return 0;
1755
1756 if (!tp->packets_out)
1757 goto out;
1758
1759 used_sacks = 0;
1760 first_sack_index = 0;
1761 for (i = 0; i < num_sacks; i++) {
1762 int dup_sack = !i && found_dup_sack;
1763
1764 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq);
1765 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq);
1766
1767 if (!tcp_is_sackblock_valid(tp, dup_sack,
1768 sp[used_sacks].start_seq,
1769 sp[used_sacks].end_seq)) {
1770 int mib_idx;
1771
1772 if (dup_sack) {
1773 if (!tp->undo_marker)
1774 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO;
1775 else
1776 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD;
1777 } else {
1778 /* Don't count olds caused by ACK reordering */
1779 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
1780 !after(sp[used_sacks].end_seq, tp->snd_una))
1781 continue;
1782 mib_idx = LINUX_MIB_TCPSACKDISCARD;
1783 }
1784
1785 NET_INC_STATS_BH(sock_net(sk), mib_idx);
1786 if (i == 0)
1787 first_sack_index = -1;
1788 continue;
1789 }
1790
1791 /* Ignore very old stuff early */
1792 if (!after(sp[used_sacks].end_seq, prior_snd_una))
1793 continue;
1794
1795 used_sacks++;
1796 }
1797
1798 /* order SACK blocks to allow in order walk of the retrans queue */
1799 for (i = used_sacks - 1; i > 0; i--) {
1800 for (j = 0; j < i; j++) {
1801 if (after(sp[j].start_seq, sp[j + 1].start_seq)) {
1802 swap(sp[j], sp[j + 1]);
1803
1804 /* Track where the first SACK block goes to */
1805 if (j == first_sack_index)
1806 first_sack_index = j + 1;
1807 }
1808 }
1809 }
1810
1811 skb = tcp_write_queue_head(sk);
1812 state.fack_count = 0;
1813 i = 0;
1814
1815 if (!tp->sacked_out) {
1816 /* It's already past, so skip checking against it */
1817 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache);
1818 } else {
1819 cache = tp->recv_sack_cache;
1820 /* Skip empty blocks in at head of the cache */
1821 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq &&
1822 !cache->end_seq)
1823 cache++;
1824 }
1825
1826 while (i < used_sacks) {
1827 u32 start_seq = sp[i].start_seq;
1828 u32 end_seq = sp[i].end_seq;
1829 int dup_sack = (found_dup_sack && (i == first_sack_index));
1830 struct tcp_sack_block *next_dup = NULL;
1831
1832 if (found_dup_sack && ((i + 1) == first_sack_index))
1833 next_dup = &sp[i + 1];
1834
1835 /* Event "B" in the comment above. */
1836 if (after(end_seq, tp->high_seq))
1837 state.flag |= FLAG_DATA_LOST;
1838
1839 /* Skip too early cached blocks */
1840 while (tcp_sack_cache_ok(tp, cache) &&
1841 !before(start_seq, cache->end_seq))
1842 cache++;
1843
1844 /* Can skip some work by looking recv_sack_cache? */
1845 if (tcp_sack_cache_ok(tp, cache) && !dup_sack &&
1846 after(end_seq, cache->start_seq)) {
1847
1848 /* Head todo? */
1849 if (before(start_seq, cache->start_seq)) {
1850 skb = tcp_sacktag_skip(skb, sk, &state,
1851 start_seq);
1852 skb = tcp_sacktag_walk(skb, sk, next_dup,
1853 &state,
1854 start_seq,
1855 cache->start_seq,
1856 dup_sack);
1857 }
1858
1859 /* Rest of the block already fully processed? */
1860 if (!after(end_seq, cache->end_seq))
1861 goto advance_sp;
1862
1863 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
1864 &state,
1865 cache->end_seq);
1866
1867 /* ...tail remains todo... */
1868 if (tcp_highest_sack_seq(tp) == cache->end_seq) {
1869 /* ...but better entrypoint exists! */
1870 skb = tcp_highest_sack(sk);
1871 if (skb == NULL)
1872 break;
1873 state.fack_count = tp->fackets_out;
1874 cache++;
1875 goto walk;
1876 }
1877
1878 skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq);
1879 /* Check overlap against next cached too (past this one already) */
1880 cache++;
1881 continue;
1882 }
1883
1884 if (!before(start_seq, tcp_highest_sack_seq(tp))) {
1885 skb = tcp_highest_sack(sk);
1886 if (skb == NULL)
1887 break;
1888 state.fack_count = tp->fackets_out;
1889 }
1890 skb = tcp_sacktag_skip(skb, sk, &state, start_seq);
1891
1892walk:
1893 skb = tcp_sacktag_walk(skb, sk, next_dup, &state,
1894 start_seq, end_seq, dup_sack);
1895
1896advance_sp:
1897 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1898 * due to in-order walk
1899 */
1900 if (after(end_seq, tp->frto_highmark))
1901 state.flag &= ~FLAG_ONLY_ORIG_SACKED;
1902
1903 i++;
1904 }
1905
1906 /* Clear the head of the cache sack blocks so we can skip it next time */
1907 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) {
1908 tp->recv_sack_cache[i].start_seq = 0;
1909 tp->recv_sack_cache[i].end_seq = 0;
1910 }
1911 for (j = 0; j < used_sacks; j++)
1912 tp->recv_sack_cache[i++] = sp[j];
1913
1914 tcp_mark_lost_retrans(sk);
1915
1916 tcp_verify_left_out(tp);
1917
1918 if ((state.reord < tp->fackets_out) &&
1919 ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) &&
1920 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
1921 tcp_update_reordering(sk, tp->fackets_out - state.reord, 0);
1922
1923out:
1924
1925#if FASTRETRANS_DEBUG > 0
1926 WARN_ON((int)tp->sacked_out < 0);
1927 WARN_ON((int)tp->lost_out < 0);
1928 WARN_ON((int)tp->retrans_out < 0);
1929 WARN_ON((int)tcp_packets_in_flight(tp) < 0);
1930#endif
1931 return state.flag;
1932}
1933
1934/* Limits sacked_out so that sum with lost_out isn't ever larger than
1935 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1936 */
1937static int tcp_limit_reno_sacked(struct tcp_sock *tp)
1938{
1939 u32 holes;
1940
1941 holes = max(tp->lost_out, 1U);
1942 holes = min(holes, tp->packets_out);
1943
1944 if ((tp->sacked_out + holes) > tp->packets_out) {
1945 tp->sacked_out = tp->packets_out - holes;
1946 return 1;
1947 }
1948 return 0;
1949}
1950
1951/* If we receive more dupacks than we expected counting segments
1952 * in assumption of absent reordering, interpret this as reordering.
1953 * The only another reason could be bug in receiver TCP.
1954 */
1955static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1956{
1957 struct tcp_sock *tp = tcp_sk(sk);
1958 if (tcp_limit_reno_sacked(tp))
1959 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1960}
1961
1962/* Emulate SACKs for SACKless connection: account for a new dupack. */
1963
1964static void tcp_add_reno_sack(struct sock *sk)
1965{
1966 struct tcp_sock *tp = tcp_sk(sk);
1967 tp->sacked_out++;
1968 tcp_check_reno_reordering(sk, 0);
1969 tcp_verify_left_out(tp);
1970}
1971
1972/* Account for ACK, ACKing some data in Reno Recovery phase. */
1973
1974static void tcp_remove_reno_sacks(struct sock *sk, int acked)
1975{
1976 struct tcp_sock *tp = tcp_sk(sk);
1977
1978 if (acked > 0) {
1979 /* One ACK acked hole. The rest eat duplicate ACKs. */
1980 if (acked - 1 >= tp->sacked_out)
1981 tp->sacked_out = 0;
1982 else
1983 tp->sacked_out -= acked - 1;
1984 }
1985 tcp_check_reno_reordering(sk, acked);
1986 tcp_verify_left_out(tp);
1987}
1988
1989static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1990{
1991 tp->sacked_out = 0;
1992}
1993
1994static int tcp_is_sackfrto(const struct tcp_sock *tp)
1995{
1996 return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp);
1997}
1998
1999/* F-RTO can only be used if TCP has never retransmitted anything other than
2000 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
2001 */
2002int tcp_use_frto(struct sock *sk)
2003{
2004 const struct tcp_sock *tp = tcp_sk(sk);
2005 const struct inet_connection_sock *icsk = inet_csk(sk);
2006 struct sk_buff *skb;
2007
2008 if (!sysctl_tcp_frto)
2009 return 0;
2010
2011 /* MTU probe and F-RTO won't really play nicely along currently */
2012 if (icsk->icsk_mtup.probe_size)
2013 return 0;
2014
2015 if (tcp_is_sackfrto(tp))
2016 return 1;
2017
2018 /* Avoid expensive walking of rexmit queue if possible */
2019 if (tp->retrans_out > 1)
2020 return 0;
2021
2022 skb = tcp_write_queue_head(sk);
2023 if (tcp_skb_is_last(sk, skb))
2024 return 1;
2025 skb = tcp_write_queue_next(sk, skb); /* Skips head */
2026 tcp_for_write_queue_from(skb, sk) {
2027 if (skb == tcp_send_head(sk))
2028 break;
2029 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2030 return 0;
2031 /* Short-circuit when first non-SACKed skb has been checked */
2032 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
2033 break;
2034 }
2035 return 1;
2036}
2037
2038/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2039 * recovery a bit and use heuristics in tcp_process_frto() to detect if
2040 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2041 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2042 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2043 * bits are handled if the Loss state is really to be entered (in
2044 * tcp_enter_frto_loss).
2045 *
2046 * Do like tcp_enter_loss() would; when RTO expires the second time it
2047 * does:
2048 * "Reduce ssthresh if it has not yet been made inside this window."
2049 */
2050void tcp_enter_frto(struct sock *sk)
2051{
2052 const struct inet_connection_sock *icsk = inet_csk(sk);
2053 struct tcp_sock *tp = tcp_sk(sk);
2054 struct sk_buff *skb;
2055
2056 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) ||
2057 tp->snd_una == tp->high_seq ||
2058 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) &&
2059 !icsk->icsk_retransmits)) {
2060 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2061 /* Our state is too optimistic in ssthresh() call because cwnd
2062 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
2063 * recovery has not yet completed. Pattern would be this: RTO,
2064 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2065 * up here twice).
2066 * RFC4138 should be more specific on what to do, even though
2067 * RTO is quite unlikely to occur after the first Cumulative ACK
2068 * due to back-off and complexity of triggering events ...
2069 */
2070 if (tp->frto_counter) {
2071 u32 stored_cwnd;
2072 stored_cwnd = tp->snd_cwnd;
2073 tp->snd_cwnd = 2;
2074 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2075 tp->snd_cwnd = stored_cwnd;
2076 } else {
2077 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2078 }
2079 /* ... in theory, cong.control module could do "any tricks" in
2080 * ssthresh(), which means that ca_state, lost bits and lost_out
2081 * counter would have to be faked before the call occurs. We
2082 * consider that too expensive, unlikely and hacky, so modules
2083 * using these in ssthresh() must deal these incompatibility
2084 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2085 */
2086 tcp_ca_event(sk, CA_EVENT_FRTO);
2087 }
2088
2089 tp->undo_marker = tp->snd_una;
2090 tp->undo_retrans = 0;
2091
2092 skb = tcp_write_queue_head(sk);
2093 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2094 tp->undo_marker = 0;
2095 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2096 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2097 tp->retrans_out -= tcp_skb_pcount(skb);
2098 }
2099 tcp_verify_left_out(tp);
2100
2101 /* Too bad if TCP was application limited */
2102 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
2103
2104 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2105 * The last condition is necessary at least in tp->frto_counter case.
2106 */
2107 if (tcp_is_sackfrto(tp) && (tp->frto_counter ||
2108 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) &&
2109 after(tp->high_seq, tp->snd_una)) {
2110 tp->frto_highmark = tp->high_seq;
2111 } else {
2112 tp->frto_highmark = tp->snd_nxt;
2113 }
2114 tcp_set_ca_state(sk, TCP_CA_Disorder);
2115 tp->high_seq = tp->snd_nxt;
2116 tp->frto_counter = 1;
2117}
2118
2119/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2120 * which indicates that we should follow the traditional RTO recovery,
2121 * i.e. mark everything lost and do go-back-N retransmission.
2122 */
2123static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
2124{
2125 struct tcp_sock *tp = tcp_sk(sk);
2126 struct sk_buff *skb;
2127
2128 tp->lost_out = 0;
2129 tp->retrans_out = 0;
2130 if (tcp_is_reno(tp))
2131 tcp_reset_reno_sack(tp);
2132
2133 tcp_for_write_queue(skb, sk) {
2134 if (skb == tcp_send_head(sk))
2135 break;
2136
2137 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2138 /*
2139 * Count the retransmission made on RTO correctly (only when
2140 * waiting for the first ACK and did not get it)...
2141 */
2142 if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) {
2143 /* For some reason this R-bit might get cleared? */
2144 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
2145 tp->retrans_out += tcp_skb_pcount(skb);
2146 /* ...enter this if branch just for the first segment */
2147 flag |= FLAG_DATA_ACKED;
2148 } else {
2149 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2150 tp->undo_marker = 0;
2151 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2152 }
2153
2154 /* Marking forward transmissions that were made after RTO lost
2155 * can cause unnecessary retransmissions in some scenarios,
2156 * SACK blocks will mitigate that in some but not in all cases.
2157 * We used to not mark them but it was causing break-ups with
2158 * receivers that do only in-order receival.
2159 *
2160 * TODO: we could detect presence of such receiver and select
2161 * different behavior per flow.
2162 */
2163 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
2164 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
2165 tp->lost_out += tcp_skb_pcount(skb);
2166 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
2167 }
2168 }
2169 tcp_verify_left_out(tp);
2170
2171 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments;
2172 tp->snd_cwnd_cnt = 0;
2173 tp->snd_cwnd_stamp = tcp_time_stamp;
2174 tp->frto_counter = 0;
2175 tp->bytes_acked = 0;
2176
2177 tp->reordering = min_t(unsigned int, tp->reordering,
2178 sysctl_tcp_reordering);
2179 tcp_set_ca_state(sk, TCP_CA_Loss);
2180 tp->high_seq = tp->snd_nxt;
2181 TCP_ECN_queue_cwr(tp);
2182
2183 tcp_clear_all_retrans_hints(tp);
2184}
2185
2186static void tcp_clear_retrans_partial(struct tcp_sock *tp)
2187{
2188 tp->retrans_out = 0;
2189 tp->lost_out = 0;
2190
2191 tp->undo_marker = 0;
2192 tp->undo_retrans = 0;
2193}
2194
2195void tcp_clear_retrans(struct tcp_sock *tp)
2196{
2197 tcp_clear_retrans_partial(tp);
2198
2199 tp->fackets_out = 0;
2200 tp->sacked_out = 0;
2201}
2202
2203/* Enter Loss state. If "how" is not zero, forget all SACK information
2204 * and reset tags completely, otherwise preserve SACKs. If receiver
2205 * dropped its ofo queue, we will know this due to reneging detection.
2206 */
2207void tcp_enter_loss(struct sock *sk, int how)
2208{
2209 const struct inet_connection_sock *icsk = inet_csk(sk);
2210 struct tcp_sock *tp = tcp_sk(sk);
2211 struct sk_buff *skb;
2212
2213 /* Reduce ssthresh if it has not yet been made inside this window. */
2214 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
2215 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
2216 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2217 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2218 tcp_ca_event(sk, CA_EVENT_LOSS);
2219 }
2220 tp->snd_cwnd = 1;
2221 tp->snd_cwnd_cnt = 0;
2222 tp->snd_cwnd_stamp = tcp_time_stamp;
2223
2224 tp->bytes_acked = 0;
2225 tcp_clear_retrans_partial(tp);
2226
2227 if (tcp_is_reno(tp))
2228 tcp_reset_reno_sack(tp);
2229
2230 if (!how) {
2231 /* Push undo marker, if it was plain RTO and nothing
2232 * was retransmitted. */
2233 tp->undo_marker = tp->snd_una;
2234 } else {
2235 tp->sacked_out = 0;
2236 tp->fackets_out = 0;
2237 }
2238 tcp_clear_all_retrans_hints(tp);
2239
2240 tcp_for_write_queue(skb, sk) {
2241 if (skb == tcp_send_head(sk))
2242 break;
2243
2244 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
2245 tp->undo_marker = 0;
2246 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
2247 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
2248 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
2249 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
2250 tp->lost_out += tcp_skb_pcount(skb);
2251 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
2252 }
2253 }
2254 tcp_verify_left_out(tp);
2255
2256 tp->reordering = min_t(unsigned int, tp->reordering,
2257 sysctl_tcp_reordering);
2258 tcp_set_ca_state(sk, TCP_CA_Loss);
2259 tp->high_seq = tp->snd_nxt;
2260 TCP_ECN_queue_cwr(tp);
2261 /* Abort F-RTO algorithm if one is in progress */
2262 tp->frto_counter = 0;
2263}
2264
2265/* If ACK arrived pointing to a remembered SACK, it means that our
2266 * remembered SACKs do not reflect real state of receiver i.e.
2267 * receiver _host_ is heavily congested (or buggy).
2268 *
2269 * Do processing similar to RTO timeout.
2270 */
2271static int tcp_check_sack_reneging(struct sock *sk, int flag)
2272{
2273 if (flag & FLAG_SACK_RENEGING) {
2274 struct inet_connection_sock *icsk = inet_csk(sk);
2275 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
2276
2277 tcp_enter_loss(sk, 1);
2278 icsk->icsk_retransmits++;
2279 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
2280 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2281 icsk->icsk_rto, TCP_RTO_MAX);
2282 return 1;
2283 }
2284 return 0;
2285}
2286
2287static inline int tcp_fackets_out(struct tcp_sock *tp)
2288{
2289 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out;
2290}
2291
2292/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2293 * counter when SACK is enabled (without SACK, sacked_out is used for
2294 * that purpose).
2295 *
2296 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2297 * segments up to the highest received SACK block so far and holes in
2298 * between them.
2299 *
2300 * With reordering, holes may still be in flight, so RFC3517 recovery
2301 * uses pure sacked_out (total number of SACKed segments) even though
2302 * it violates the RFC that uses duplicate ACKs, often these are equal
2303 * but when e.g. out-of-window ACKs or packet duplication occurs,
2304 * they differ. Since neither occurs due to loss, TCP should really
2305 * ignore them.
2306 */
2307static inline int tcp_dupack_heuristics(struct tcp_sock *tp)
2308{
2309 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
2310}
2311
2312static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
2313{
2314 return tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto;
2315}
2316
2317static inline int tcp_head_timedout(struct sock *sk)
2318{
2319 struct tcp_sock *tp = tcp_sk(sk);
2320
2321 return tp->packets_out &&
2322 tcp_skb_timedout(sk, tcp_write_queue_head(sk));
2323}
2324
2325/* Linux NewReno/SACK/FACK/ECN state machine.
2326 * --------------------------------------
2327 *
2328 * "Open" Normal state, no dubious events, fast path.
2329 * "Disorder" In all the respects it is "Open",
2330 * but requires a bit more attention. It is entered when
2331 * we see some SACKs or dupacks. It is split of "Open"
2332 * mainly to move some processing from fast path to slow one.
2333 * "CWR" CWND was reduced due to some Congestion Notification event.
2334 * It can be ECN, ICMP source quench, local device congestion.
2335 * "Recovery" CWND was reduced, we are fast-retransmitting.
2336 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2337 *
2338 * tcp_fastretrans_alert() is entered:
2339 * - each incoming ACK, if state is not "Open"
2340 * - when arrived ACK is unusual, namely:
2341 * * SACK
2342 * * Duplicate ACK.
2343 * * ECN ECE.
2344 *
2345 * Counting packets in flight is pretty simple.
2346 *
2347 * in_flight = packets_out - left_out + retrans_out
2348 *
2349 * packets_out is SND.NXT-SND.UNA counted in packets.
2350 *
2351 * retrans_out is number of retransmitted segments.
2352 *
2353 * left_out is number of segments left network, but not ACKed yet.
2354 *
2355 * left_out = sacked_out + lost_out
2356 *
2357 * sacked_out: Packets, which arrived to receiver out of order
2358 * and hence not ACKed. With SACKs this number is simply
2359 * amount of SACKed data. Even without SACKs
2360 * it is easy to give pretty reliable estimate of this number,
2361 * counting duplicate ACKs.
2362 *
2363 * lost_out: Packets lost by network. TCP has no explicit
2364 * "loss notification" feedback from network (for now).
2365 * It means that this number can be only _guessed_.
2366 * Actually, it is the heuristics to predict lossage that
2367 * distinguishes different algorithms.
2368 *
2369 * F.e. after RTO, when all the queue is considered as lost,
2370 * lost_out = packets_out and in_flight = retrans_out.
2371 *
2372 * Essentially, we have now two algorithms counting
2373 * lost packets.
2374 *
2375 * FACK: It is the simplest heuristics. As soon as we decided
2376 * that something is lost, we decide that _all_ not SACKed
2377 * packets until the most forward SACK are lost. I.e.
2378 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2379 * It is absolutely correct estimate, if network does not reorder
2380 * packets. And it loses any connection to reality when reordering
2381 * takes place. We use FACK by default until reordering
2382 * is suspected on the path to this destination.
2383 *
2384 * NewReno: when Recovery is entered, we assume that one segment
2385 * is lost (classic Reno). While we are in Recovery and
2386 * a partial ACK arrives, we assume that one more packet
2387 * is lost (NewReno). This heuristics are the same in NewReno
2388 * and SACK.
2389 *
2390 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2391 * deflation etc. CWND is real congestion window, never inflated, changes
2392 * only according to classic VJ rules.
2393 *
2394 * Really tricky (and requiring careful tuning) part of algorithm
2395 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2396 * The first determines the moment _when_ we should reduce CWND and,
2397 * hence, slow down forward transmission. In fact, it determines the moment
2398 * when we decide that hole is caused by loss, rather than by a reorder.
2399 *
2400 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2401 * holes, caused by lost packets.
2402 *
2403 * And the most logically complicated part of algorithm is undo
2404 * heuristics. We detect false retransmits due to both too early
2405 * fast retransmit (reordering) and underestimated RTO, analyzing
2406 * timestamps and D-SACKs. When we detect that some segments were
2407 * retransmitted by mistake and CWND reduction was wrong, we undo
2408 * window reduction and abort recovery phase. This logic is hidden
2409 * inside several functions named tcp_try_undo_<something>.
2410 */
2411
2412/* This function decides, when we should leave Disordered state
2413 * and enter Recovery phase, reducing congestion window.
2414 *
2415 * Main question: may we further continue forward transmission
2416 * with the same cwnd?
2417 */
2418static int tcp_time_to_recover(struct sock *sk)
2419{
2420 struct tcp_sock *tp = tcp_sk(sk);
2421 __u32 packets_out;
2422
2423 /* Do not perform any recovery during F-RTO algorithm */
2424 if (tp->frto_counter)
2425 return 0;
2426
2427 /* Trick#1: The loss is proven. */
2428 if (tp->lost_out)
2429 return 1;
2430
2431 /* Not-A-Trick#2 : Classic rule... */
2432 if (tcp_dupack_heuristics(tp) > tp->reordering)
2433 return 1;
2434
2435 /* Trick#3 : when we use RFC2988 timer restart, fast
2436 * retransmit can be triggered by timeout of queue head.
2437 */
2438 if (tcp_is_fack(tp) && tcp_head_timedout(sk))
2439 return 1;
2440
2441 /* Trick#4: It is still not OK... But will it be useful to delay
2442 * recovery more?
2443 */
2444 packets_out = tp->packets_out;
2445 if (packets_out <= tp->reordering &&
2446 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
2447 !tcp_may_send_now(sk)) {
2448 /* We have nothing to send. This connection is limited
2449 * either by receiver window or by application.
2450 */
2451 return 1;
2452 }
2453
2454 /* If a thin stream is detected, retransmit after first
2455 * received dupack. Employ only if SACK is supported in order
2456 * to avoid possible corner-case series of spurious retransmissions
2457 * Use only if there are no unsent data.
2458 */
2459 if ((tp->thin_dupack || sysctl_tcp_thin_dupack) &&
2460 tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 &&
2461 tcp_is_sack(tp) && !tcp_send_head(sk))
2462 return 1;
2463
2464 return 0;
2465}
2466
2467/* New heuristics: it is possible only after we switched to restart timer
2468 * each time when something is ACKed. Hence, we can detect timed out packets
2469 * during fast retransmit without falling to slow start.
2470 *
2471 * Usefulness of this as is very questionable, since we should know which of
2472 * the segments is the next to timeout which is relatively expensive to find
2473 * in general case unless we add some data structure just for that. The
2474 * current approach certainly won't find the right one too often and when it
2475 * finally does find _something_ it usually marks large part of the window
2476 * right away (because a retransmission with a larger timestamp blocks the
2477 * loop from advancing). -ij
2478 */
2479static void tcp_timeout_skbs(struct sock *sk)
2480{
2481 struct tcp_sock *tp = tcp_sk(sk);
2482 struct sk_buff *skb;
2483
2484 if (!tcp_is_fack(tp) || !tcp_head_timedout(sk))
2485 return;
2486
2487 skb = tp->scoreboard_skb_hint;
2488 if (tp->scoreboard_skb_hint == NULL)
2489 skb = tcp_write_queue_head(sk);
2490
2491 tcp_for_write_queue_from(skb, sk) {
2492 if (skb == tcp_send_head(sk))
2493 break;
2494 if (!tcp_skb_timedout(sk, skb))
2495 break;
2496
2497 tcp_skb_mark_lost(tp, skb);
2498 }
2499
2500 tp->scoreboard_skb_hint = skb;
2501
2502 tcp_verify_left_out(tp);
2503}
2504
2505/* Mark head of queue up as lost. With RFC3517 SACK, the packets is
2506 * is against sacked "cnt", otherwise it's against facked "cnt"
2507 */
2508static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
2509{
2510 struct tcp_sock *tp = tcp_sk(sk);
2511 struct sk_buff *skb;
2512 int cnt, oldcnt;
2513 int err;
2514 unsigned int mss;
2515
2516 WARN_ON(packets > tp->packets_out);
2517 if (tp->lost_skb_hint) {
2518 skb = tp->lost_skb_hint;
2519 cnt = tp->lost_cnt_hint;
2520 /* Head already handled? */
2521 if (mark_head && skb != tcp_write_queue_head(sk))
2522 return;
2523 } else {
2524 skb = tcp_write_queue_head(sk);
2525 cnt = 0;
2526 }
2527
2528 tcp_for_write_queue_from(skb, sk) {
2529 if (skb == tcp_send_head(sk))
2530 break;
2531 /* TODO: do this better */
2532 /* this is not the most efficient way to do this... */
2533 tp->lost_skb_hint = skb;
2534 tp->lost_cnt_hint = cnt;
2535
2536 if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
2537 break;
2538
2539 oldcnt = cnt;
2540 if (tcp_is_fack(tp) || tcp_is_reno(tp) ||
2541 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
2542 cnt += tcp_skb_pcount(skb);
2543
2544 if (cnt > packets) {
2545 if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) ||
2546 (oldcnt >= packets))
2547 break;
2548
2549 mss = skb_shinfo(skb)->gso_size;
2550 err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss);
2551 if (err < 0)
2552 break;
2553 cnt = packets;
2554 }
2555
2556 tcp_skb_mark_lost(tp, skb);
2557
2558 if (mark_head)
2559 break;
2560 }
2561 tcp_verify_left_out(tp);
2562}
2563
2564/* Account newly detected lost packet(s) */
2565
2566static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
2567{
2568 struct tcp_sock *tp = tcp_sk(sk);
2569
2570 if (tcp_is_reno(tp)) {
2571 tcp_mark_head_lost(sk, 1, 1);
2572 } else if (tcp_is_fack(tp)) {
2573 int lost = tp->fackets_out - tp->reordering;
2574 if (lost <= 0)
2575 lost = 1;
2576 tcp_mark_head_lost(sk, lost, 0);
2577 } else {
2578 int sacked_upto = tp->sacked_out - tp->reordering;
2579 if (sacked_upto >= 0)
2580 tcp_mark_head_lost(sk, sacked_upto, 0);
2581 else if (fast_rexmit)
2582 tcp_mark_head_lost(sk, 1, 1);
2583 }
2584
2585 tcp_timeout_skbs(sk);
2586}
2587
2588/* CWND moderation, preventing bursts due to too big ACKs
2589 * in dubious situations.
2590 */
2591static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
2592{
2593 tp->snd_cwnd = min(tp->snd_cwnd,
2594 tcp_packets_in_flight(tp) + tcp_max_burst(tp));
2595 tp->snd_cwnd_stamp = tcp_time_stamp;
2596}
2597
2598/* Lower bound on congestion window is slow start threshold
2599 * unless congestion avoidance choice decides to overide it.
2600 */
2601static inline u32 tcp_cwnd_min(const struct sock *sk)
2602{
2603 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
2604
2605 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
2606}
2607
2608/* Decrease cwnd each second ack. */
2609static void tcp_cwnd_down(struct sock *sk, int flag)
2610{
2611 struct tcp_sock *tp = tcp_sk(sk);
2612 int decr = tp->snd_cwnd_cnt + 1;
2613
2614 if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) ||
2615 (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) {
2616 tp->snd_cwnd_cnt = decr & 1;
2617 decr >>= 1;
2618
2619 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
2620 tp->snd_cwnd -= decr;
2621
2622 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1);
2623 tp->snd_cwnd_stamp = tcp_time_stamp;
2624 }
2625}
2626
2627/* Nothing was retransmitted or returned timestamp is less
2628 * than timestamp of the first retransmission.
2629 */
2630static inline int tcp_packet_delayed(struct tcp_sock *tp)
2631{
2632 return !tp->retrans_stamp ||
2633 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
2634 before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp));
2635}
2636
2637/* Undo procedures. */
2638
2639#if FASTRETRANS_DEBUG > 1
2640static void DBGUNDO(struct sock *sk, const char *msg)
2641{
2642 struct tcp_sock *tp = tcp_sk(sk);
2643 struct inet_sock *inet = inet_sk(sk);
2644
2645 if (sk->sk_family == AF_INET) {
2646 printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2647 msg,
2648 &inet->inet_daddr, ntohs(inet->inet_dport),
2649 tp->snd_cwnd, tcp_left_out(tp),
2650 tp->snd_ssthresh, tp->prior_ssthresh,
2651 tp->packets_out);
2652 }
2653#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
2654 else if (sk->sk_family == AF_INET6) {
2655 struct ipv6_pinfo *np = inet6_sk(sk);
2656 printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2657 msg,
2658 &np->daddr, ntohs(inet->inet_dport),
2659 tp->snd_cwnd, tcp_left_out(tp),
2660 tp->snd_ssthresh, tp->prior_ssthresh,
2661 tp->packets_out);
2662 }
2663#endif
2664}
2665#else
2666#define DBGUNDO(x...) do { } while (0)
2667#endif
2668
2669static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh)
2670{
2671 struct tcp_sock *tp = tcp_sk(sk);
2672
2673 if (tp->prior_ssthresh) {
2674 const struct inet_connection_sock *icsk = inet_csk(sk);
2675
2676 if (icsk->icsk_ca_ops->undo_cwnd)
2677 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
2678 else
2679 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
2680
2681 if (undo_ssthresh && tp->prior_ssthresh > tp->snd_ssthresh) {
2682 tp->snd_ssthresh = tp->prior_ssthresh;
2683 TCP_ECN_withdraw_cwr(tp);
2684 }
2685 } else {
2686 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
2687 }
2688 tp->snd_cwnd_stamp = tcp_time_stamp;
2689}
2690
2691static inline int tcp_may_undo(struct tcp_sock *tp)
2692{
2693 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
2694}
2695
2696/* People celebrate: "We love our President!" */
2697static int tcp_try_undo_recovery(struct sock *sk)
2698{
2699 struct tcp_sock *tp = tcp_sk(sk);
2700
2701 if (tcp_may_undo(tp)) {
2702 int mib_idx;
2703
2704 /* Happy end! We did not retransmit anything
2705 * or our original transmission succeeded.
2706 */
2707 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
2708 tcp_undo_cwr(sk, true);
2709 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
2710 mib_idx = LINUX_MIB_TCPLOSSUNDO;
2711 else
2712 mib_idx = LINUX_MIB_TCPFULLUNDO;
2713
2714 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2715 tp->undo_marker = 0;
2716 }
2717 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) {
2718 /* Hold old state until something *above* high_seq
2719 * is ACKed. For Reno it is MUST to prevent false
2720 * fast retransmits (RFC2582). SACK TCP is safe. */
2721 tcp_moderate_cwnd(tp);
2722 return 1;
2723 }
2724 tcp_set_ca_state(sk, TCP_CA_Open);
2725 return 0;
2726}
2727
2728/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2729static void tcp_try_undo_dsack(struct sock *sk)
2730{
2731 struct tcp_sock *tp = tcp_sk(sk);
2732
2733 if (tp->undo_marker && !tp->undo_retrans) {
2734 DBGUNDO(sk, "D-SACK");
2735 tcp_undo_cwr(sk, true);
2736 tp->undo_marker = 0;
2737 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
2738 }
2739}
2740
2741/* We can clear retrans_stamp when there are no retransmissions in the
2742 * window. It would seem that it is trivially available for us in
2743 * tp->retrans_out, however, that kind of assumptions doesn't consider
2744 * what will happen if errors occur when sending retransmission for the
2745 * second time. ...It could the that such segment has only
2746 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2747 * the head skb is enough except for some reneging corner cases that
2748 * are not worth the effort.
2749 *
2750 * Main reason for all this complexity is the fact that connection dying
2751 * time now depends on the validity of the retrans_stamp, in particular,
2752 * that successive retransmissions of a segment must not advance
2753 * retrans_stamp under any conditions.
2754 */
2755static int tcp_any_retrans_done(struct sock *sk)
2756{
2757 struct tcp_sock *tp = tcp_sk(sk);
2758 struct sk_buff *skb;
2759
2760 if (tp->retrans_out)
2761 return 1;
2762
2763 skb = tcp_write_queue_head(sk);
2764 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
2765 return 1;
2766
2767 return 0;
2768}
2769
2770/* Undo during fast recovery after partial ACK. */
2771
2772static int tcp_try_undo_partial(struct sock *sk, int acked)
2773{
2774 struct tcp_sock *tp = tcp_sk(sk);
2775 /* Partial ACK arrived. Force Hoe's retransmit. */
2776 int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering);
2777
2778 if (tcp_may_undo(tp)) {
2779 /* Plain luck! Hole if filled with delayed
2780 * packet, rather than with a retransmit.
2781 */
2782 if (!tcp_any_retrans_done(sk))
2783 tp->retrans_stamp = 0;
2784
2785 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
2786
2787 DBGUNDO(sk, "Hoe");
2788 tcp_undo_cwr(sk, false);
2789 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO);
2790
2791 /* So... Do not make Hoe's retransmit yet.
2792 * If the first packet was delayed, the rest
2793 * ones are most probably delayed as well.
2794 */
2795 failed = 0;
2796 }
2797 return failed;
2798}
2799
2800/* Undo during loss recovery after partial ACK. */
2801static int tcp_try_undo_loss(struct sock *sk)
2802{
2803 struct tcp_sock *tp = tcp_sk(sk);
2804
2805 if (tcp_may_undo(tp)) {
2806 struct sk_buff *skb;
2807 tcp_for_write_queue(skb, sk) {
2808 if (skb == tcp_send_head(sk))
2809 break;
2810 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
2811 }
2812
2813 tcp_clear_all_retrans_hints(tp);
2814
2815 DBGUNDO(sk, "partial loss");
2816 tp->lost_out = 0;
2817 tcp_undo_cwr(sk, true);
2818 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO);
2819 inet_csk(sk)->icsk_retransmits = 0;
2820 tp->undo_marker = 0;
2821 if (tcp_is_sack(tp))
2822 tcp_set_ca_state(sk, TCP_CA_Open);
2823 return 1;
2824 }
2825 return 0;
2826}
2827
2828static inline void tcp_complete_cwr(struct sock *sk)
2829{
2830 struct tcp_sock *tp = tcp_sk(sk);
2831 /* Do not moderate cwnd if it's already undone in cwr or recovery */
2832 if (tp->undo_marker && tp->snd_cwnd > tp->snd_ssthresh) {
2833 tp->snd_cwnd = tp->snd_ssthresh;
2834 tp->snd_cwnd_stamp = tcp_time_stamp;
2835 }
2836 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
2837}
2838
2839static void tcp_try_keep_open(struct sock *sk)
2840{
2841 struct tcp_sock *tp = tcp_sk(sk);
2842 int state = TCP_CA_Open;
2843
2844 if (tcp_left_out(tp) || tcp_any_retrans_done(sk) || tp->undo_marker)
2845 state = TCP_CA_Disorder;
2846
2847 if (inet_csk(sk)->icsk_ca_state != state) {
2848 tcp_set_ca_state(sk, state);
2849 tp->high_seq = tp->snd_nxt;
2850 }
2851}
2852
2853static void tcp_try_to_open(struct sock *sk, int flag)
2854{
2855 struct tcp_sock *tp = tcp_sk(sk);
2856
2857 tcp_verify_left_out(tp);
2858
2859 if (!tp->frto_counter && !tcp_any_retrans_done(sk))
2860 tp->retrans_stamp = 0;
2861
2862 if (flag & FLAG_ECE)
2863 tcp_enter_cwr(sk, 1);
2864
2865 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
2866 tcp_try_keep_open(sk);
2867 tcp_moderate_cwnd(tp);
2868 } else {
2869 tcp_cwnd_down(sk, flag);
2870 }
2871}
2872
2873static void tcp_mtup_probe_failed(struct sock *sk)
2874{
2875 struct inet_connection_sock *icsk = inet_csk(sk);
2876
2877 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
2878 icsk->icsk_mtup.probe_size = 0;
2879}
2880
2881static void tcp_mtup_probe_success(struct sock *sk)
2882{
2883 struct tcp_sock *tp = tcp_sk(sk);
2884 struct inet_connection_sock *icsk = inet_csk(sk);
2885
2886 /* FIXME: breaks with very large cwnd */
2887 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2888 tp->snd_cwnd = tp->snd_cwnd *
2889 tcp_mss_to_mtu(sk, tp->mss_cache) /
2890 icsk->icsk_mtup.probe_size;
2891 tp->snd_cwnd_cnt = 0;
2892 tp->snd_cwnd_stamp = tcp_time_stamp;
2893 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2894
2895 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
2896 icsk->icsk_mtup.probe_size = 0;
2897 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
2898}
2899
2900/* Do a simple retransmit without using the backoff mechanisms in
2901 * tcp_timer. This is used for path mtu discovery.
2902 * The socket is already locked here.
2903 */
2904void tcp_simple_retransmit(struct sock *sk)
2905{
2906 const struct inet_connection_sock *icsk = inet_csk(sk);
2907 struct tcp_sock *tp = tcp_sk(sk);
2908 struct sk_buff *skb;
2909 unsigned int mss = tcp_current_mss(sk);
2910 u32 prior_lost = tp->lost_out;
2911
2912 tcp_for_write_queue(skb, sk) {
2913 if (skb == tcp_send_head(sk))
2914 break;
2915 if (tcp_skb_seglen(skb) > mss &&
2916 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
2917 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2918 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
2919 tp->retrans_out -= tcp_skb_pcount(skb);
2920 }
2921 tcp_skb_mark_lost_uncond_verify(tp, skb);
2922 }
2923 }
2924
2925 tcp_clear_retrans_hints_partial(tp);
2926
2927 if (prior_lost == tp->lost_out)
2928 return;
2929
2930 if (tcp_is_reno(tp))
2931 tcp_limit_reno_sacked(tp);
2932
2933 tcp_verify_left_out(tp);
2934
2935 /* Don't muck with the congestion window here.
2936 * Reason is that we do not increase amount of _data_
2937 * in network, but units changed and effective
2938 * cwnd/ssthresh really reduced now.
2939 */
2940 if (icsk->icsk_ca_state != TCP_CA_Loss) {
2941 tp->high_seq = tp->snd_nxt;
2942 tp->snd_ssthresh = tcp_current_ssthresh(sk);
2943 tp->prior_ssthresh = 0;
2944 tp->undo_marker = 0;
2945 tcp_set_ca_state(sk, TCP_CA_Loss);
2946 }
2947 tcp_xmit_retransmit_queue(sk);
2948}
2949EXPORT_SYMBOL(tcp_simple_retransmit);
2950
2951/* Process an event, which can update packets-in-flight not trivially.
2952 * Main goal of this function is to calculate new estimate for left_out,
2953 * taking into account both packets sitting in receiver's buffer and
2954 * packets lost by network.
2955 *
2956 * Besides that it does CWND reduction, when packet loss is detected
2957 * and changes state of machine.
2958 *
2959 * It does _not_ decide what to send, it is made in function
2960 * tcp_xmit_retransmit_queue().
2961 */
2962static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
2963{
2964 struct inet_connection_sock *icsk = inet_csk(sk);
2965 struct tcp_sock *tp = tcp_sk(sk);
2966 int is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
2967 int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
2968 (tcp_fackets_out(tp) > tp->reordering));
2969 int fast_rexmit = 0, mib_idx;
2970
2971 if (WARN_ON(!tp->packets_out && tp->sacked_out))
2972 tp->sacked_out = 0;
2973 if (WARN_ON(!tp->sacked_out && tp->fackets_out))
2974 tp->fackets_out = 0;
2975
2976 /* Now state machine starts.
2977 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2978 if (flag & FLAG_ECE)
2979 tp->prior_ssthresh = 0;
2980
2981 /* B. In all the states check for reneging SACKs. */
2982 if (tcp_check_sack_reneging(sk, flag))
2983 return;
2984
2985 /* C. Process data loss notification, provided it is valid. */
2986 if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) &&
2987 before(tp->snd_una, tp->high_seq) &&
2988 icsk->icsk_ca_state != TCP_CA_Open &&
2989 tp->fackets_out > tp->reordering) {
2990 tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering, 0);
2991 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS);
2992 }
2993
2994 /* D. Check consistency of the current state. */
2995 tcp_verify_left_out(tp);
2996
2997 /* E. Check state exit conditions. State can be terminated
2998 * when high_seq is ACKed. */
2999 if (icsk->icsk_ca_state == TCP_CA_Open) {
3000 WARN_ON(tp->retrans_out != 0);
3001 tp->retrans_stamp = 0;
3002 } else if (!before(tp->snd_una, tp->high_seq)) {
3003 switch (icsk->icsk_ca_state) {
3004 case TCP_CA_Loss:
3005 icsk->icsk_retransmits = 0;
3006 if (tcp_try_undo_recovery(sk))
3007 return;
3008 break;
3009
3010 case TCP_CA_CWR:
3011 /* CWR is to be held something *above* high_seq
3012 * is ACKed for CWR bit to reach receiver. */
3013 if (tp->snd_una != tp->high_seq) {
3014 tcp_complete_cwr(sk);
3015 tcp_set_ca_state(sk, TCP_CA_Open);
3016 }
3017 break;
3018
3019 case TCP_CA_Disorder:
3020 tcp_try_undo_dsack(sk);
3021 if (!tp->undo_marker ||
3022 /* For SACK case do not Open to allow to undo
3023 * catching for all duplicate ACKs. */
3024 tcp_is_reno(tp) || tp->snd_una != tp->high_seq) {
3025 tp->undo_marker = 0;
3026 tcp_set_ca_state(sk, TCP_CA_Open);
3027 }
3028 break;
3029
3030 case TCP_CA_Recovery:
3031 if (tcp_is_reno(tp))
3032 tcp_reset_reno_sack(tp);
3033 if (tcp_try_undo_recovery(sk))
3034 return;
3035 tcp_complete_cwr(sk);
3036 break;
3037 }
3038 }
3039
3040 /* F. Process state. */
3041 switch (icsk->icsk_ca_state) {
3042 case TCP_CA_Recovery:
3043 if (!(flag & FLAG_SND_UNA_ADVANCED)) {
3044 if (tcp_is_reno(tp) && is_dupack)
3045 tcp_add_reno_sack(sk);
3046 } else
3047 do_lost = tcp_try_undo_partial(sk, pkts_acked);
3048 break;
3049 case TCP_CA_Loss:
3050 if (flag & FLAG_DATA_ACKED)
3051 icsk->icsk_retransmits = 0;
3052 if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED)
3053 tcp_reset_reno_sack(tp);
3054 if (!tcp_try_undo_loss(sk)) {
3055 tcp_moderate_cwnd(tp);
3056 tcp_xmit_retransmit_queue(sk);
3057 return;
3058 }
3059 if (icsk->icsk_ca_state != TCP_CA_Open)
3060 return;
3061 /* Loss is undone; fall through to processing in Open state. */
3062 default:
3063 if (tcp_is_reno(tp)) {
3064 if (flag & FLAG_SND_UNA_ADVANCED)
3065 tcp_reset_reno_sack(tp);
3066 if (is_dupack)
3067 tcp_add_reno_sack(sk);
3068 }
3069
3070 if (icsk->icsk_ca_state == TCP_CA_Disorder)
3071 tcp_try_undo_dsack(sk);
3072
3073 if (!tcp_time_to_recover(sk)) {
3074 tcp_try_to_open(sk, flag);
3075 return;
3076 }
3077
3078 /* MTU probe failure: don't reduce cwnd */
3079 if (icsk->icsk_ca_state < TCP_CA_CWR &&
3080 icsk->icsk_mtup.probe_size &&
3081 tp->snd_una == tp->mtu_probe.probe_seq_start) {
3082 tcp_mtup_probe_failed(sk);
3083 /* Restores the reduction we did in tcp_mtup_probe() */
3084 tp->snd_cwnd++;
3085 tcp_simple_retransmit(sk);
3086 return;
3087 }
3088
3089 /* Otherwise enter Recovery state */
3090
3091 if (tcp_is_reno(tp))
3092 mib_idx = LINUX_MIB_TCPRENORECOVERY;
3093 else
3094 mib_idx = LINUX_MIB_TCPSACKRECOVERY;
3095
3096 NET_INC_STATS_BH(sock_net(sk), mib_idx);
3097
3098 tp->high_seq = tp->snd_nxt;
3099 tp->prior_ssthresh = 0;
3100 tp->undo_marker = tp->snd_una;
3101 tp->undo_retrans = tp->retrans_out;
3102
3103 if (icsk->icsk_ca_state < TCP_CA_CWR) {
3104 if (!(flag & FLAG_ECE))
3105 tp->prior_ssthresh = tcp_current_ssthresh(sk);
3106 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
3107 TCP_ECN_queue_cwr(tp);
3108 }
3109
3110 tp->bytes_acked = 0;
3111 tp->snd_cwnd_cnt = 0;
3112 tcp_set_ca_state(sk, TCP_CA_Recovery);
3113 fast_rexmit = 1;
3114 }
3115
3116 if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk)))
3117 tcp_update_scoreboard(sk, fast_rexmit);
3118 tcp_cwnd_down(sk, flag);
3119 tcp_xmit_retransmit_queue(sk);
3120}
3121
3122void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt)
3123{
3124 tcp_rtt_estimator(sk, seq_rtt);
3125 tcp_set_rto(sk);
3126 inet_csk(sk)->icsk_backoff = 0;
3127}
3128EXPORT_SYMBOL(tcp_valid_rtt_meas);
3129
3130/* Read draft-ietf-tcplw-high-performance before mucking
3131 * with this code. (Supersedes RFC1323)
3132 */
3133static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
3134{
3135 /* RTTM Rule: A TSecr value received in a segment is used to
3136 * update the averaged RTT measurement only if the segment
3137 * acknowledges some new data, i.e., only if it advances the
3138 * left edge of the send window.
3139 *
3140 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3141 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3142 *
3143 * Changed: reset backoff as soon as we see the first valid sample.
3144 * If we do not, we get strongly overestimated rto. With timestamps
3145 * samples are accepted even from very old segments: f.e., when rtt=1
3146 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3147 * answer arrives rto becomes 120 seconds! If at least one of segments
3148 * in window is lost... Voila. --ANK (010210)
3149 */
3150 struct tcp_sock *tp = tcp_sk(sk);
3151
3152 tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr);
3153}
3154
3155static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
3156{
3157 /* We don't have a timestamp. Can only use
3158 * packets that are not retransmitted to determine
3159 * rtt estimates. Also, we must not reset the
3160 * backoff for rto until we get a non-retransmitted
3161 * packet. This allows us to deal with a situation
3162 * where the network delay has increased suddenly.
3163 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3164 */
3165
3166 if (flag & FLAG_RETRANS_DATA_ACKED)
3167 return;
3168
3169 tcp_valid_rtt_meas(sk, seq_rtt);
3170}
3171
3172static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
3173 const s32 seq_rtt)
3174{
3175 const struct tcp_sock *tp = tcp_sk(sk);
3176 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3177 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
3178 tcp_ack_saw_tstamp(sk, flag);
3179 else if (seq_rtt >= 0)
3180 tcp_ack_no_tstamp(sk, seq_rtt, flag);
3181}
3182
3183static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
3184{
3185 const struct inet_connection_sock *icsk = inet_csk(sk);
3186 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight);
3187 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
3188}
3189
3190/* Restart timer after forward progress on connection.
3191 * RFC2988 recommends to restart timer to now+rto.
3192 */
3193static void tcp_rearm_rto(struct sock *sk)
3194{
3195 struct tcp_sock *tp = tcp_sk(sk);
3196
3197 if (!tp->packets_out) {
3198 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
3199 } else {
3200 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3201 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3202 }
3203}
3204
3205/* If we get here, the whole TSO packet has not been acked. */
3206static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
3207{
3208 struct tcp_sock *tp = tcp_sk(sk);
3209 u32 packets_acked;
3210
3211 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una));
3212
3213 packets_acked = tcp_skb_pcount(skb);
3214 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3215 return 0;
3216 packets_acked -= tcp_skb_pcount(skb);
3217
3218 if (packets_acked) {
3219 BUG_ON(tcp_skb_pcount(skb) == 0);
3220 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq));
3221 }
3222
3223 return packets_acked;
3224}
3225
3226/* Remove acknowledged frames from the retransmission queue. If our packet
3227 * is before the ack sequence we can discard it as it's confirmed to have
3228 * arrived at the other end.
3229 */
3230static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
3231 u32 prior_snd_una)
3232{
3233 struct tcp_sock *tp = tcp_sk(sk);
3234 const struct inet_connection_sock *icsk = inet_csk(sk);
3235 struct sk_buff *skb;
3236 u32 now = tcp_time_stamp;
3237 int fully_acked = 1;
3238 int flag = 0;
3239 u32 pkts_acked = 0;
3240 u32 reord = tp->packets_out;
3241 u32 prior_sacked = tp->sacked_out;
3242 s32 seq_rtt = -1;
3243 s32 ca_seq_rtt = -1;
3244 ktime_t last_ackt = net_invalid_timestamp();
3245
3246 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
3247 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
3248 u32 acked_pcount;
3249 u8 sacked = scb->sacked;
3250
3251 /* Determine how many packets and what bytes were acked, tso and else */
3252 if (after(scb->end_seq, tp->snd_una)) {
3253 if (tcp_skb_pcount(skb) == 1 ||
3254 !after(tp->snd_una, scb->seq))
3255 break;
3256
3257 acked_pcount = tcp_tso_acked(sk, skb);
3258 if (!acked_pcount)
3259 break;
3260
3261 fully_acked = 0;
3262 } else {
3263 acked_pcount = tcp_skb_pcount(skb);
3264 }
3265
3266 if (sacked & TCPCB_RETRANS) {
3267 if (sacked & TCPCB_SACKED_RETRANS)
3268 tp->retrans_out -= acked_pcount;
3269 flag |= FLAG_RETRANS_DATA_ACKED;
3270 ca_seq_rtt = -1;
3271 seq_rtt = -1;
3272 if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1))
3273 flag |= FLAG_NONHEAD_RETRANS_ACKED;
3274 } else {
3275 ca_seq_rtt = now - scb->when;
3276 last_ackt = skb->tstamp;
3277 if (seq_rtt < 0) {
3278 seq_rtt = ca_seq_rtt;
3279 }
3280 if (!(sacked & TCPCB_SACKED_ACKED))
3281 reord = min(pkts_acked, reord);
3282 }
3283
3284 if (sacked & TCPCB_SACKED_ACKED)
3285 tp->sacked_out -= acked_pcount;
3286 if (sacked & TCPCB_LOST)
3287 tp->lost_out -= acked_pcount;
3288
3289 tp->packets_out -= acked_pcount;
3290 pkts_acked += acked_pcount;
3291
3292 /* Initial outgoing SYN's get put onto the write_queue
3293 * just like anything else we transmit. It is not
3294 * true data, and if we misinform our callers that
3295 * this ACK acks real data, we will erroneously exit
3296 * connection startup slow start one packet too
3297 * quickly. This is severely frowned upon behavior.
3298 */
3299 if (!(scb->flags & TCPHDR_SYN)) {
3300 flag |= FLAG_DATA_ACKED;
3301 } else {
3302 flag |= FLAG_SYN_ACKED;
3303 tp->retrans_stamp = 0;
3304 }
3305
3306 if (!fully_acked)
3307 break;
3308
3309 tcp_unlink_write_queue(skb, sk);
3310 sk_wmem_free_skb(sk, skb);
3311 tp->scoreboard_skb_hint = NULL;
3312 if (skb == tp->retransmit_skb_hint)
3313 tp->retransmit_skb_hint = NULL;
3314 if (skb == tp->lost_skb_hint)
3315 tp->lost_skb_hint = NULL;
3316 }
3317
3318 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
3319 tp->snd_up = tp->snd_una;
3320
3321 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
3322 flag |= FLAG_SACK_RENEGING;
3323
3324 if (flag & FLAG_ACKED) {
3325 const struct tcp_congestion_ops *ca_ops
3326 = inet_csk(sk)->icsk_ca_ops;
3327
3328 if (unlikely(icsk->icsk_mtup.probe_size &&
3329 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) {
3330 tcp_mtup_probe_success(sk);
3331 }
3332
3333 tcp_ack_update_rtt(sk, flag, seq_rtt);
3334 tcp_rearm_rto(sk);
3335
3336 if (tcp_is_reno(tp)) {
3337 tcp_remove_reno_sacks(sk, pkts_acked);
3338 } else {
3339 int delta;
3340
3341 /* Non-retransmitted hole got filled? That's reordering */
3342 if (reord < prior_fackets)
3343 tcp_update_reordering(sk, tp->fackets_out - reord, 0);
3344
3345 delta = tcp_is_fack(tp) ? pkts_acked :
3346 prior_sacked - tp->sacked_out;
3347 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta);
3348 }
3349
3350 tp->fackets_out -= min(pkts_acked, tp->fackets_out);
3351
3352 if (ca_ops->pkts_acked) {
3353 s32 rtt_us = -1;
3354
3355 /* Is the ACK triggering packet unambiguous? */
3356 if (!(flag & FLAG_RETRANS_DATA_ACKED)) {
3357 /* High resolution needed and available? */
3358 if (ca_ops->flags & TCP_CONG_RTT_STAMP &&
3359 !ktime_equal(last_ackt,
3360 net_invalid_timestamp()))
3361 rtt_us = ktime_us_delta(ktime_get_real(),
3362 last_ackt);
3363 else if (ca_seq_rtt >= 0)
3364 rtt_us = jiffies_to_usecs(ca_seq_rtt);
3365 }
3366
3367 ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
3368 }
3369 }
3370
3371#if FASTRETRANS_DEBUG > 0
3372 WARN_ON((int)tp->sacked_out < 0);
3373 WARN_ON((int)tp->lost_out < 0);
3374 WARN_ON((int)tp->retrans_out < 0);
3375 if (!tp->packets_out && tcp_is_sack(tp)) {
3376 icsk = inet_csk(sk);
3377 if (tp->lost_out) {
3378 printk(KERN_DEBUG "Leak l=%u %d\n",
3379 tp->lost_out, icsk->icsk_ca_state);
3380 tp->lost_out = 0;
3381 }
3382 if (tp->sacked_out) {
3383 printk(KERN_DEBUG "Leak s=%u %d\n",
3384 tp->sacked_out, icsk->icsk_ca_state);
3385 tp->sacked_out = 0;
3386 }
3387 if (tp->retrans_out) {
3388 printk(KERN_DEBUG "Leak r=%u %d\n",
3389 tp->retrans_out, icsk->icsk_ca_state);
3390 tp->retrans_out = 0;
3391 }
3392 }
3393#endif
3394 return flag;
3395}
3396
3397static void tcp_ack_probe(struct sock *sk)
3398{
3399 const struct tcp_sock *tp = tcp_sk(sk);
3400 struct inet_connection_sock *icsk = inet_csk(sk);
3401
3402 /* Was it a usable window open? */
3403
3404 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) {
3405 icsk->icsk_backoff = 0;
3406 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
3407 /* Socket must be waked up by subsequent tcp_data_snd_check().
3408 * This function is not for random using!
3409 */
3410 } else {
3411 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3412 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
3413 TCP_RTO_MAX);
3414 }
3415}
3416
3417static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
3418{
3419 return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
3420 inet_csk(sk)->icsk_ca_state != TCP_CA_Open;
3421}
3422
3423static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
3424{
3425 const struct tcp_sock *tp = tcp_sk(sk);
3426 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
3427 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
3428}
3429
3430/* Check that window update is acceptable.
3431 * The function assumes that snd_una<=ack<=snd_next.
3432 */
3433static inline int tcp_may_update_window(const struct tcp_sock *tp,
3434 const u32 ack, const u32 ack_seq,
3435 const u32 nwin)
3436{
3437 return after(ack, tp->snd_una) ||
3438 after(ack_seq, tp->snd_wl1) ||
3439 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd);
3440}
3441
3442/* Update our send window.
3443 *
3444 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3445 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3446 */
3447static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack,
3448 u32 ack_seq)
3449{
3450 struct tcp_sock *tp = tcp_sk(sk);
3451 int flag = 0;
3452 u32 nwin = ntohs(tcp_hdr(skb)->window);
3453
3454 if (likely(!tcp_hdr(skb)->syn))
3455 nwin <<= tp->rx_opt.snd_wscale;
3456
3457 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
3458 flag |= FLAG_WIN_UPDATE;
3459 tcp_update_wl(tp, ack_seq);
3460
3461 if (tp->snd_wnd != nwin) {
3462 tp->snd_wnd = nwin;
3463
3464 /* Note, it is the only place, where
3465 * fast path is recovered for sending TCP.
3466 */
3467 tp->pred_flags = 0;
3468 tcp_fast_path_check(sk);
3469
3470 if (nwin > tp->max_window) {
3471 tp->max_window = nwin;
3472 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
3473 }
3474 }
3475 }
3476
3477 tp->snd_una = ack;
3478
3479 return flag;
3480}
3481
3482/* A very conservative spurious RTO response algorithm: reduce cwnd and
3483 * continue in congestion avoidance.
3484 */
3485static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
3486{
3487 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
3488 tp->snd_cwnd_cnt = 0;
3489 tp->bytes_acked = 0;
3490 TCP_ECN_queue_cwr(tp);
3491 tcp_moderate_cwnd(tp);
3492}
3493
3494/* A conservative spurious RTO response algorithm: reduce cwnd using
3495 * rate halving and continue in congestion avoidance.
3496 */
3497static void tcp_ratehalving_spur_to_response(struct sock *sk)
3498{
3499 tcp_enter_cwr(sk, 0);
3500}
3501
3502static void tcp_undo_spur_to_response(struct sock *sk, int flag)
3503{
3504 if (flag & FLAG_ECE)
3505 tcp_ratehalving_spur_to_response(sk);
3506 else
3507 tcp_undo_cwr(sk, true);
3508}
3509
3510/* F-RTO spurious RTO detection algorithm (RFC4138)
3511 *
3512 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3513 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3514 * window (but not to or beyond highest sequence sent before RTO):
3515 * On First ACK, send two new segments out.
3516 * On Second ACK, RTO was likely spurious. Do spurious response (response
3517 * algorithm is not part of the F-RTO detection algorithm
3518 * given in RFC4138 but can be selected separately).
3519 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3520 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3521 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3522 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3523 *
3524 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3525 * original window even after we transmit two new data segments.
3526 *
3527 * SACK version:
3528 * on first step, wait until first cumulative ACK arrives, then move to
3529 * the second step. In second step, the next ACK decides.
3530 *
3531 * F-RTO is implemented (mainly) in four functions:
3532 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3533 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3534 * called when tcp_use_frto() showed green light
3535 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3536 * - tcp_enter_frto_loss() is called if there is not enough evidence
3537 * to prove that the RTO is indeed spurious. It transfers the control
3538 * from F-RTO to the conventional RTO recovery
3539 */
3540static int tcp_process_frto(struct sock *sk, int flag)
3541{
3542 struct tcp_sock *tp = tcp_sk(sk);
3543
3544 tcp_verify_left_out(tp);
3545
3546 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3547 if (flag & FLAG_DATA_ACKED)
3548 inet_csk(sk)->icsk_retransmits = 0;
3549
3550 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) ||
3551 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED)))
3552 tp->undo_marker = 0;
3553
3554 if (!before(tp->snd_una, tp->frto_highmark)) {
3555 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag);
3556 return 1;
3557 }
3558
3559 if (!tcp_is_sackfrto(tp)) {
3560 /* RFC4138 shortcoming in step 2; should also have case c):
3561 * ACK isn't duplicate nor advances window, e.g., opposite dir
3562 * data, winupdate
3563 */
3564 if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP))
3565 return 1;
3566
3567 if (!(flag & FLAG_DATA_ACKED)) {
3568 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3),
3569 flag);
3570 return 1;
3571 }
3572 } else {
3573 if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) {
3574 /* Prevent sending of new data. */
3575 tp->snd_cwnd = min(tp->snd_cwnd,
3576 tcp_packets_in_flight(tp));
3577 return 1;
3578 }
3579
3580 if ((tp->frto_counter >= 2) &&
3581 (!(flag & FLAG_FORWARD_PROGRESS) ||
3582 ((flag & FLAG_DATA_SACKED) &&
3583 !(flag & FLAG_ONLY_ORIG_SACKED)))) {
3584 /* RFC4138 shortcoming (see comment above) */
3585 if (!(flag & FLAG_FORWARD_PROGRESS) &&
3586 (flag & FLAG_NOT_DUP))
3587 return 1;
3588
3589 tcp_enter_frto_loss(sk, 3, flag);
3590 return 1;
3591 }
3592 }
3593
3594 if (tp->frto_counter == 1) {
3595 /* tcp_may_send_now needs to see updated state */
3596 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
3597 tp->frto_counter = 2;
3598
3599 if (!tcp_may_send_now(sk))
3600 tcp_enter_frto_loss(sk, 2, flag);
3601
3602 return 1;
3603 } else {
3604 switch (sysctl_tcp_frto_response) {
3605 case 2:
3606 tcp_undo_spur_to_response(sk, flag);
3607 break;
3608 case 1:
3609 tcp_conservative_spur_to_response(tp);
3610 break;
3611 default:
3612 tcp_ratehalving_spur_to_response(sk);
3613 break;
3614 }
3615 tp->frto_counter = 0;
3616 tp->undo_marker = 0;
3617 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUSRTOS);
3618 }
3619 return 0;
3620}
3621
3622/* This routine deals with incoming acks, but not outgoing ones. */
3623static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
3624{
3625 struct inet_connection_sock *icsk = inet_csk(sk);
3626 struct tcp_sock *tp = tcp_sk(sk);
3627 u32 prior_snd_una = tp->snd_una;
3628 u32 ack_seq = TCP_SKB_CB(skb)->seq;
3629 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3630 u32 prior_in_flight;
3631 u32 prior_fackets;
3632 int prior_packets;
3633 int frto_cwnd = 0;
3634
3635 /* If the ack is older than previous acks
3636 * then we can probably ignore it.
3637 */
3638 if (before(ack, prior_snd_una))
3639 goto old_ack;
3640
3641 /* If the ack includes data we haven't sent yet, discard
3642 * this segment (RFC793 Section 3.9).
3643 */
3644 if (after(ack, tp->snd_nxt))
3645 goto invalid_ack;
3646
3647 if (after(ack, prior_snd_una))
3648 flag |= FLAG_SND_UNA_ADVANCED;
3649
3650 if (sysctl_tcp_abc) {
3651 if (icsk->icsk_ca_state < TCP_CA_CWR)
3652 tp->bytes_acked += ack - prior_snd_una;
3653 else if (icsk->icsk_ca_state == TCP_CA_Loss)
3654 /* we assume just one segment left network */
3655 tp->bytes_acked += min(ack - prior_snd_una,
3656 tp->mss_cache);
3657 }
3658
3659 prior_fackets = tp->fackets_out;
3660 prior_in_flight = tcp_packets_in_flight(tp);
3661
3662 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
3663 /* Window is constant, pure forward advance.
3664 * No more checks are required.
3665 * Note, we use the fact that SND.UNA>=SND.WL2.
3666 */
3667 tcp_update_wl(tp, ack_seq);
3668 tp->snd_una = ack;
3669 flag |= FLAG_WIN_UPDATE;
3670
3671 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
3672
3673 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS);
3674 } else {
3675 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
3676 flag |= FLAG_DATA;
3677 else
3678 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS);
3679
3680 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq);
3681
3682 if (TCP_SKB_CB(skb)->sacked)
3683 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
3684
3685 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb)))
3686 flag |= FLAG_ECE;
3687
3688 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
3689 }
3690
3691 /* We passed data and got it acked, remove any soft error
3692 * log. Something worked...
3693 */
3694 sk->sk_err_soft = 0;
3695 icsk->icsk_probes_out = 0;
3696 tp->rcv_tstamp = tcp_time_stamp;
3697 prior_packets = tp->packets_out;
3698 if (!prior_packets)
3699 goto no_queue;
3700
3701 /* See if we can take anything off of the retransmit queue. */
3702 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);
3703
3704 if (tp->frto_counter)
3705 frto_cwnd = tcp_process_frto(sk, flag);
3706 /* Guarantee sacktag reordering detection against wrap-arounds */
3707 if (before(tp->frto_highmark, tp->snd_una))
3708 tp->frto_highmark = 0;
3709
3710 if (tcp_ack_is_dubious(sk, flag)) {
3711 /* Advance CWND, if state allows this. */
3712 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&
3713 tcp_may_raise_cwnd(sk, flag))
3714 tcp_cong_avoid(sk, ack, prior_in_flight);
3715 tcp_fastretrans_alert(sk, prior_packets - tp->packets_out,
3716 flag);
3717 } else {
3718 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
3719 tcp_cong_avoid(sk, ack, prior_in_flight);
3720 }
3721
3722 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
3723 dst_confirm(__sk_dst_get(sk));
3724
3725 return 1;
3726
3727no_queue:
3728 /* If this ack opens up a zero window, clear backoff. It was
3729 * being used to time the probes, and is probably far higher than
3730 * it needs to be for normal retransmission.
3731 */
3732 if (tcp_send_head(sk))
3733 tcp_ack_probe(sk);
3734 return 1;
3735
3736invalid_ack:
3737 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3738 return -1;
3739
3740old_ack:
3741 if (TCP_SKB_CB(skb)->sacked) {
3742 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
3743 if (icsk->icsk_ca_state == TCP_CA_Open)
3744 tcp_try_keep_open(sk);
3745 }
3746
3747 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
3748 return 0;
3749}
3750
3751/* Look for tcp options. Normally only called on SYN and SYNACK packets.
3752 * But, this can also be called on packets in the established flow when
3753 * the fast version below fails.
3754 */
3755void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
3756 u8 **hvpp, int estab)
3757{
3758 unsigned char *ptr;
3759 struct tcphdr *th = tcp_hdr(skb);
3760 int length = (th->doff * 4) - sizeof(struct tcphdr);
3761
3762 ptr = (unsigned char *)(th + 1);
3763 opt_rx->saw_tstamp = 0;
3764
3765 while (length > 0) {
3766 int opcode = *ptr++;
3767 int opsize;
3768
3769 switch (opcode) {
3770 case TCPOPT_EOL:
3771 return;
3772 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3773 length--;
3774 continue;
3775 default:
3776 opsize = *ptr++;
3777 if (opsize < 2) /* "silly options" */
3778 return;
3779 if (opsize > length)
3780 return; /* don't parse partial options */
3781 switch (opcode) {
3782 case TCPOPT_MSS:
3783 if (opsize == TCPOLEN_MSS && th->syn && !estab) {
3784 u16 in_mss = get_unaligned_be16(ptr);
3785 if (in_mss) {
3786 if (opt_rx->user_mss &&
3787 opt_rx->user_mss < in_mss)
3788 in_mss = opt_rx->user_mss;
3789 opt_rx->mss_clamp = in_mss;
3790 }
3791 }
3792 break;
3793 case TCPOPT_WINDOW:
3794 if (opsize == TCPOLEN_WINDOW && th->syn &&
3795 !estab && sysctl_tcp_window_scaling) {
3796 __u8 snd_wscale = *(__u8 *)ptr;
3797 opt_rx->wscale_ok = 1;
3798 if (snd_wscale > 14) {
3799 if (net_ratelimit())
3800 printk(KERN_INFO "tcp_parse_options: Illegal window "
3801 "scaling value %d >14 received.\n",
3802 snd_wscale);
3803 snd_wscale = 14;
3804 }
3805 opt_rx->snd_wscale = snd_wscale;
3806 }
3807 break;
3808 case TCPOPT_TIMESTAMP:
3809 if ((opsize == TCPOLEN_TIMESTAMP) &&
3810 ((estab && opt_rx->tstamp_ok) ||
3811 (!estab && sysctl_tcp_timestamps))) {
3812 opt_rx->saw_tstamp = 1;
3813 opt_rx->rcv_tsval = get_unaligned_be32(ptr);
3814 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4);
3815 }
3816 break;
3817 case TCPOPT_SACK_PERM:
3818 if (opsize == TCPOLEN_SACK_PERM && th->syn &&
3819 !estab && sysctl_tcp_sack) {
3820 opt_rx->sack_ok = 1;
3821 tcp_sack_reset(opt_rx);
3822 }
3823 break;
3824
3825 case TCPOPT_SACK:
3826 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
3827 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3828 opt_rx->sack_ok) {
3829 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3830 }
3831 break;
3832#ifdef CONFIG_TCP_MD5SIG
3833 case TCPOPT_MD5SIG:
3834 /*
3835 * The MD5 Hash has already been
3836 * checked (see tcp_v{4,6}_do_rcv()).
3837 */
3838 break;
3839#endif
3840 case TCPOPT_COOKIE:
3841 /* This option is variable length.
3842 */
3843 switch (opsize) {
3844 case TCPOLEN_COOKIE_BASE:
3845 /* not yet implemented */
3846 break;
3847 case TCPOLEN_COOKIE_PAIR:
3848 /* not yet implemented */
3849 break;
3850 case TCPOLEN_COOKIE_MIN+0:
3851 case TCPOLEN_COOKIE_MIN+2:
3852 case TCPOLEN_COOKIE_MIN+4:
3853 case TCPOLEN_COOKIE_MIN+6:
3854 case TCPOLEN_COOKIE_MAX:
3855 /* 16-bit multiple */
3856 opt_rx->cookie_plus = opsize;
3857 *hvpp = ptr;
3858 break;
3859 default:
3860 /* ignore option */
3861 break;
3862 }
3863 break;
3864 }
3865
3866 ptr += opsize-2;
3867 length -= opsize;
3868 }
3869 }
3870}
3871EXPORT_SYMBOL(tcp_parse_options);
3872
3873static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th)
3874{
3875 __be32 *ptr = (__be32 *)(th + 1);
3876
3877 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3878 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3879 tp->rx_opt.saw_tstamp = 1;
3880 ++ptr;
3881 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3882 ++ptr;
3883 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3884 return 1;
3885 }
3886 return 0;
3887}
3888
3889/* Fast parse options. This hopes to only see timestamps.
3890 * If it is wrong it falls back on tcp_parse_options().
3891 */
3892static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
3893 struct tcp_sock *tp, u8 **hvpp)
3894{
3895 /* In the spirit of fast parsing, compare doff directly to constant
3896 * values. Because equality is used, short doff can be ignored here.
3897 */
3898 if (th->doff == (sizeof(*th) / 4)) {
3899 tp->rx_opt.saw_tstamp = 0;
3900 return 0;
3901 } else if (tp->rx_opt.tstamp_ok &&
3902 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) {
3903 if (tcp_parse_aligned_timestamp(tp, th))
3904 return 1;
3905 }
3906 tcp_parse_options(skb, &tp->rx_opt, hvpp, 1);
3907 return 1;
3908}
3909
3910#ifdef CONFIG_TCP_MD5SIG
3911/*
3912 * Parse MD5 Signature option
3913 */
3914u8 *tcp_parse_md5sig_option(struct tcphdr *th)
3915{
3916 int length = (th->doff << 2) - sizeof (*th);
3917 u8 *ptr = (u8*)(th + 1);
3918
3919 /* If the TCP option is too short, we can short cut */
3920 if (length < TCPOLEN_MD5SIG)
3921 return NULL;
3922
3923 while (length > 0) {
3924 int opcode = *ptr++;
3925 int opsize;
3926
3927 switch(opcode) {
3928 case TCPOPT_EOL:
3929 return NULL;
3930 case TCPOPT_NOP:
3931 length--;
3932 continue;
3933 default:
3934 opsize = *ptr++;
3935 if (opsize < 2 || opsize > length)
3936 return NULL;
3937 if (opcode == TCPOPT_MD5SIG)
3938 return opsize == TCPOLEN_MD5SIG ? ptr : NULL;
3939 }
3940 ptr += opsize - 2;
3941 length -= opsize;
3942 }
3943 return NULL;
3944}
3945EXPORT_SYMBOL(tcp_parse_md5sig_option);
3946#endif
3947
3948static inline void tcp_store_ts_recent(struct tcp_sock *tp)
3949{
3950 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
3951 tp->rx_opt.ts_recent_stamp = get_seconds();
3952}
3953
3954static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3955{
3956 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3957 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3958 * extra check below makes sure this can only happen
3959 * for pure ACK frames. -DaveM
3960 *
3961 * Not only, also it occurs for expired timestamps.
3962 */
3963
3964 if (tcp_paws_check(&tp->rx_opt, 0))
3965 tcp_store_ts_recent(tp);
3966 }
3967}
3968
3969/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3970 *
3971 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3972 * it can pass through stack. So, the following predicate verifies that
3973 * this segment is not used for anything but congestion avoidance or
3974 * fast retransmit. Moreover, we even are able to eliminate most of such
3975 * second order effects, if we apply some small "replay" window (~RTO)
3976 * to timestamp space.
3977 *
3978 * All these measures still do not guarantee that we reject wrapped ACKs
3979 * on networks with high bandwidth, when sequence space is recycled fastly,
3980 * but it guarantees that such events will be very rare and do not affect
3981 * connection seriously. This doesn't look nice, but alas, PAWS is really
3982 * buggy extension.
3983 *
3984 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3985 * states that events when retransmit arrives after original data are rare.
3986 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3987 * the biggest problem on large power networks even with minor reordering.
3988 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3989 * up to bandwidth of 18Gigabit/sec. 8) ]
3990 */
3991
3992static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
3993{
3994 struct tcp_sock *tp = tcp_sk(sk);
3995 struct tcphdr *th = tcp_hdr(skb);
3996 u32 seq = TCP_SKB_CB(skb)->seq;
3997 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3998
3999 return (/* 1. Pure ACK with correct sequence number. */
4000 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
4001
4002 /* 2. ... and duplicate ACK. */
4003 ack == tp->snd_una &&
4004
4005 /* 3. ... and does not update window. */
4006 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
4007
4008 /* 4. ... and sits in replay window. */
4009 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
4010}
4011
4012static inline int tcp_paws_discard(const struct sock *sk,
4013 const struct sk_buff *skb)
4014{
4015 const struct tcp_sock *tp = tcp_sk(sk);
4016
4017 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) &&
4018 !tcp_disordered_ack(sk, skb);
4019}
4020
4021/* Check segment sequence number for validity.
4022 *
4023 * Segment controls are considered valid, if the segment
4024 * fits to the window after truncation to the window. Acceptability
4025 * of data (and SYN, FIN, of course) is checked separately.
4026 * See tcp_data_queue(), for example.
4027 *
4028 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4029 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4030 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4031 * (borrowed from freebsd)
4032 */
4033
4034static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
4035{
4036 return !before(end_seq, tp->rcv_wup) &&
4037 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
4038}
4039
4040/* When we get a reset we do this. */
4041static void tcp_reset(struct sock *sk)
4042{
4043 /* We want the right error as BSD sees it (and indeed as we do). */
4044 switch (sk->sk_state) {
4045 case TCP_SYN_SENT:
4046 sk->sk_err = ECONNREFUSED;
4047 break;
4048 case TCP_CLOSE_WAIT:
4049 sk->sk_err = EPIPE;
4050 break;
4051 case TCP_CLOSE:
4052 return;
4053 default:
4054 sk->sk_err = ECONNRESET;
4055 }
4056 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4057 smp_wmb();
4058
4059 if (!sock_flag(sk, SOCK_DEAD))
4060 sk->sk_error_report(sk);
4061
4062 tcp_done(sk);
4063}
4064
4065/*
4066 * Process the FIN bit. This now behaves as it is supposed to work
4067 * and the FIN takes effect when it is validly part of sequence
4068 * space. Not before when we get holes.
4069 *
4070 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4071 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4072 * TIME-WAIT)
4073 *
4074 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4075 * close and we go into CLOSING (and later onto TIME-WAIT)
4076 *
4077 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4078 */
4079static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
4080{
4081 struct tcp_sock *tp = tcp_sk(sk);
4082
4083 inet_csk_schedule_ack(sk);
4084
4085 sk->sk_shutdown |= RCV_SHUTDOWN;
4086 sock_set_flag(sk, SOCK_DONE);
4087
4088 switch (sk->sk_state) {
4089 case TCP_SYN_RECV:
4090 case TCP_ESTABLISHED:
4091 /* Move to CLOSE_WAIT */
4092 tcp_set_state(sk, TCP_CLOSE_WAIT);
4093 inet_csk(sk)->icsk_ack.pingpong = 1;
4094 break;
4095
4096 case TCP_CLOSE_WAIT:
4097 case TCP_CLOSING:
4098 /* Received a retransmission of the FIN, do
4099 * nothing.
4100 */
4101 break;
4102 case TCP_LAST_ACK:
4103 /* RFC793: Remain in the LAST-ACK state. */
4104 break;
4105
4106 case TCP_FIN_WAIT1:
4107 /* This case occurs when a simultaneous close
4108 * happens, we must ack the received FIN and
4109 * enter the CLOSING state.
4110 */
4111 tcp_send_ack(sk);
4112 tcp_set_state(sk, TCP_CLOSING);
4113 break;
4114 case TCP_FIN_WAIT2:
4115 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4116 tcp_send_ack(sk);
4117 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4118 break;
4119 default:
4120 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4121 * cases we should never reach this piece of code.
4122 */
4123 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
4124 __func__, sk->sk_state);
4125 break;
4126 }
4127
4128 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4129 * Probably, we should reset in this case. For now drop them.
4130 */
4131 __skb_queue_purge(&tp->out_of_order_queue);
4132 if (tcp_is_sack(tp))
4133 tcp_sack_reset(&tp->rx_opt);
4134 sk_mem_reclaim(sk);
4135
4136 if (!sock_flag(sk, SOCK_DEAD)) {
4137 sk->sk_state_change(sk);
4138
4139 /* Do not send POLL_HUP for half duplex close. */
4140 if (sk->sk_shutdown == SHUTDOWN_MASK ||
4141 sk->sk_state == TCP_CLOSE)
4142 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
4143 else
4144 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
4145 }
4146}
4147
4148static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq,
4149 u32 end_seq)
4150{
4151 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
4152 if (before(seq, sp->start_seq))
4153 sp->start_seq = seq;
4154 if (after(end_seq, sp->end_seq))
4155 sp->end_seq = end_seq;
4156 return 1;
4157 }
4158 return 0;
4159}
4160
4161static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq)
4162{
4163 struct tcp_sock *tp = tcp_sk(sk);
4164
4165 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
4166 int mib_idx;
4167
4168 if (before(seq, tp->rcv_nxt))
4169 mib_idx = LINUX_MIB_TCPDSACKOLDSENT;
4170 else
4171 mib_idx = LINUX_MIB_TCPDSACKOFOSENT;
4172
4173 NET_INC_STATS_BH(sock_net(sk), mib_idx);
4174
4175 tp->rx_opt.dsack = 1;
4176 tp->duplicate_sack[0].start_seq = seq;
4177 tp->duplicate_sack[0].end_seq = end_seq;
4178 }
4179}
4180
4181static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
4182{
4183 struct tcp_sock *tp = tcp_sk(sk);
4184
4185 if (!tp->rx_opt.dsack)
4186 tcp_dsack_set(sk, seq, end_seq);
4187 else
4188 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
4189}
4190
4191static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
4192{
4193 struct tcp_sock *tp = tcp_sk(sk);
4194
4195 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4196 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4197 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4198 tcp_enter_quickack_mode(sk);
4199
4200 if (tcp_is_sack(tp) && sysctl_tcp_dsack) {
4201 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4202
4203 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
4204 end_seq = tp->rcv_nxt;
4205 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq);
4206 }
4207 }
4208
4209 tcp_send_ack(sk);
4210}
4211
4212/* These routines update the SACK block as out-of-order packets arrive or
4213 * in-order packets close up the sequence space.
4214 */
4215static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
4216{
4217 int this_sack;
4218 struct tcp_sack_block *sp = &tp->selective_acks[0];
4219 struct tcp_sack_block *swalk = sp + 1;
4220
4221 /* See if the recent change to the first SACK eats into
4222 * or hits the sequence space of other SACK blocks, if so coalesce.
4223 */
4224 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) {
4225 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
4226 int i;
4227
4228 /* Zap SWALK, by moving every further SACK up by one slot.
4229 * Decrease num_sacks.
4230 */
4231 tp->rx_opt.num_sacks--;
4232 for (i = this_sack; i < tp->rx_opt.num_sacks; i++)
4233 sp[i] = sp[i + 1];
4234 continue;
4235 }
4236 this_sack++, swalk++;
4237 }
4238}
4239
4240static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
4241{
4242 struct tcp_sock *tp = tcp_sk(sk);
4243 struct tcp_sack_block *sp = &tp->selective_acks[0];
4244 int cur_sacks = tp->rx_opt.num_sacks;
4245 int this_sack;
4246
4247 if (!cur_sacks)
4248 goto new_sack;
4249
4250 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) {
4251 if (tcp_sack_extend(sp, seq, end_seq)) {
4252 /* Rotate this_sack to the first one. */
4253 for (; this_sack > 0; this_sack--, sp--)
4254 swap(*sp, *(sp - 1));
4255 if (cur_sacks > 1)
4256 tcp_sack_maybe_coalesce(tp);
4257 return;
4258 }
4259 }
4260
4261 /* Could not find an adjacent existing SACK, build a new one,
4262 * put it at the front, and shift everyone else down. We
4263 * always know there is at least one SACK present already here.
4264 *
4265 * If the sack array is full, forget about the last one.
4266 */
4267 if (this_sack >= TCP_NUM_SACKS) {
4268 this_sack--;
4269 tp->rx_opt.num_sacks--;
4270 sp--;
4271 }
4272 for (; this_sack > 0; this_sack--, sp--)
4273 *sp = *(sp - 1);
4274
4275new_sack:
4276 /* Build the new head SACK, and we're done. */
4277 sp->start_seq = seq;
4278 sp->end_seq = end_seq;
4279 tp->rx_opt.num_sacks++;
4280}
4281
4282/* RCV.NXT advances, some SACKs should be eaten. */
4283
4284static void tcp_sack_remove(struct tcp_sock *tp)
4285{
4286 struct tcp_sack_block *sp = &tp->selective_acks[0];
4287 int num_sacks = tp->rx_opt.num_sacks;
4288 int this_sack;
4289
4290 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4291 if (skb_queue_empty(&tp->out_of_order_queue)) {
4292 tp->rx_opt.num_sacks = 0;
4293 return;
4294 }
4295
4296 for (this_sack = 0; this_sack < num_sacks;) {
4297 /* Check if the start of the sack is covered by RCV.NXT. */
4298 if (!before(tp->rcv_nxt, sp->start_seq)) {
4299 int i;
4300
4301 /* RCV.NXT must cover all the block! */
4302 WARN_ON(before(tp->rcv_nxt, sp->end_seq));
4303
4304 /* Zap this SACK, by moving forward any other SACKS. */
4305 for (i=this_sack+1; i < num_sacks; i++)
4306 tp->selective_acks[i-1] = tp->selective_acks[i];
4307 num_sacks--;
4308 continue;
4309 }
4310 this_sack++;
4311 sp++;
4312 }
4313 tp->rx_opt.num_sacks = num_sacks;
4314}
4315
4316/* This one checks to see if we can put data from the
4317 * out_of_order queue into the receive_queue.
4318 */
4319static void tcp_ofo_queue(struct sock *sk)
4320{
4321 struct tcp_sock *tp = tcp_sk(sk);
4322 __u32 dsack_high = tp->rcv_nxt;
4323 struct sk_buff *skb;
4324
4325 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
4326 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4327 break;
4328
4329 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
4330 __u32 dsack = dsack_high;
4331 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
4332 dsack_high = TCP_SKB_CB(skb)->end_seq;
4333 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack);
4334 }
4335
4336 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4337 SOCK_DEBUG(sk, "ofo packet was already received\n");
4338 __skb_unlink(skb, &tp->out_of_order_queue);
4339 __kfree_skb(skb);
4340 continue;
4341 }
4342 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
4343 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4344 TCP_SKB_CB(skb)->end_seq);
4345
4346 __skb_unlink(skb, &tp->out_of_order_queue);
4347 __skb_queue_tail(&sk->sk_receive_queue, skb);
4348 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4349 if (tcp_hdr(skb)->fin)
4350 tcp_fin(skb, sk, tcp_hdr(skb));
4351 }
4352}
4353
4354static int tcp_prune_ofo_queue(struct sock *sk);
4355static int tcp_prune_queue(struct sock *sk);
4356
4357static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size)
4358{
4359 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
4360 !sk_rmem_schedule(sk, size)) {
4361
4362 if (tcp_prune_queue(sk) < 0)
4363 return -1;
4364
4365 if (!sk_rmem_schedule(sk, size)) {
4366 if (!tcp_prune_ofo_queue(sk))
4367 return -1;
4368
4369 if (!sk_rmem_schedule(sk, size))
4370 return -1;
4371 }
4372 }
4373 return 0;
4374}
4375
4376static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
4377{
4378 struct tcphdr *th = tcp_hdr(skb);
4379 struct tcp_sock *tp = tcp_sk(sk);
4380 int eaten = -1;
4381
4382 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
4383 goto drop;
4384
4385 skb_dst_drop(skb);
4386 __skb_pull(skb, th->doff * 4);
4387
4388 TCP_ECN_accept_cwr(tp, skb);
4389
4390 tp->rx_opt.dsack = 0;
4391
4392 /* Queue data for delivery to the user.
4393 * Packets in sequence go to the receive queue.
4394 * Out of sequence packets to the out_of_order_queue.
4395 */
4396 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4397 if (tcp_receive_window(tp) == 0)
4398 goto out_of_window;
4399
4400 /* Ok. In sequence. In window. */
4401 if (tp->ucopy.task == current &&
4402 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
4403 sock_owned_by_user(sk) && !tp->urg_data) {
4404 int chunk = min_t(unsigned int, skb->len,
4405 tp->ucopy.len);
4406
4407 __set_current_state(TASK_RUNNING);
4408
4409 local_bh_enable();
4410 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
4411 tp->ucopy.len -= chunk;
4412 tp->copied_seq += chunk;
4413 eaten = (chunk == skb->len);
4414 tcp_rcv_space_adjust(sk);
4415 }
4416 local_bh_disable();
4417 }
4418
4419 if (eaten <= 0) {
4420queue_and_out:
4421 if (eaten < 0 &&
4422 tcp_try_rmem_schedule(sk, skb->truesize))
4423 goto drop;
4424
4425 skb_set_owner_r(skb, sk);
4426 __skb_queue_tail(&sk->sk_receive_queue, skb);
4427 }
4428 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4429 if (skb->len)
4430 tcp_event_data_recv(sk, skb);
4431 if (th->fin)
4432 tcp_fin(skb, sk, th);
4433
4434 if (!skb_queue_empty(&tp->out_of_order_queue)) {
4435 tcp_ofo_queue(sk);
4436
4437 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4438 * gap in queue is filled.
4439 */
4440 if (skb_queue_empty(&tp->out_of_order_queue))
4441 inet_csk(sk)->icsk_ack.pingpong = 0;
4442 }
4443
4444 if (tp->rx_opt.num_sacks)
4445 tcp_sack_remove(tp);
4446
4447 tcp_fast_path_check(sk);
4448
4449 if (eaten > 0)
4450 __kfree_skb(skb);
4451 else if (!sock_flag(sk, SOCK_DEAD))
4452 sk->sk_data_ready(sk, 0);
4453 return;
4454 }
4455
4456 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
4457 /* A retransmit, 2nd most common case. Force an immediate ack. */
4458 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
4459 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4460
4461out_of_window:
4462 tcp_enter_quickack_mode(sk);
4463 inet_csk_schedule_ack(sk);
4464drop:
4465 __kfree_skb(skb);
4466 return;
4467 }
4468
4469 /* Out of window. F.e. zero window probe. */
4470 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
4471 goto out_of_window;
4472
4473 tcp_enter_quickack_mode(sk);
4474
4475 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4476 /* Partial packet, seq < rcv_next < end_seq */
4477 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
4478 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
4479 TCP_SKB_CB(skb)->end_seq);
4480
4481 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
4482
4483 /* If window is closed, drop tail of packet. But after
4484 * remembering D-SACK for its head made in previous line.
4485 */
4486 if (!tcp_receive_window(tp))
4487 goto out_of_window;
4488 goto queue_and_out;
4489 }
4490
4491 TCP_ECN_check_ce(tp, skb);
4492
4493 if (tcp_try_rmem_schedule(sk, skb->truesize))
4494 goto drop;
4495
4496 /* Disable header prediction. */
4497 tp->pred_flags = 0;
4498 inet_csk_schedule_ack(sk);
4499
4500 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
4501 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
4502
4503 skb_set_owner_r(skb, sk);
4504
4505 if (!skb_peek(&tp->out_of_order_queue)) {
4506 /* Initial out of order segment, build 1 SACK. */
4507 if (tcp_is_sack(tp)) {
4508 tp->rx_opt.num_sacks = 1;
4509 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
4510 tp->selective_acks[0].end_seq =
4511 TCP_SKB_CB(skb)->end_seq;
4512 }
4513 __skb_queue_head(&tp->out_of_order_queue, skb);
4514 } else {
4515 struct sk_buff *skb1 = skb_peek_tail(&tp->out_of_order_queue);
4516 u32 seq = TCP_SKB_CB(skb)->seq;
4517 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
4518
4519 if (seq == TCP_SKB_CB(skb1)->end_seq) {
4520 __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
4521
4522 if (!tp->rx_opt.num_sacks ||
4523 tp->selective_acks[0].end_seq != seq)
4524 goto add_sack;
4525
4526 /* Common case: data arrive in order after hole. */
4527 tp->selective_acks[0].end_seq = end_seq;
4528 return;
4529 }
4530
4531 /* Find place to insert this segment. */
4532 while (1) {
4533 if (!after(TCP_SKB_CB(skb1)->seq, seq))
4534 break;
4535 if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) {
4536 skb1 = NULL;
4537 break;
4538 }
4539 skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1);
4540 }
4541
4542 /* Do skb overlap to previous one? */
4543 if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) {
4544 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4545 /* All the bits are present. Drop. */
4546 __kfree_skb(skb);
4547 tcp_dsack_set(sk, seq, end_seq);
4548 goto add_sack;
4549 }
4550 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
4551 /* Partial overlap. */
4552 tcp_dsack_set(sk, seq,
4553 TCP_SKB_CB(skb1)->end_seq);
4554 } else {
4555 if (skb_queue_is_first(&tp->out_of_order_queue,
4556 skb1))
4557 skb1 = NULL;
4558 else
4559 skb1 = skb_queue_prev(
4560 &tp->out_of_order_queue,
4561 skb1);
4562 }
4563 }
4564 if (!skb1)
4565 __skb_queue_head(&tp->out_of_order_queue, skb);
4566 else
4567 __skb_queue_after(&tp->out_of_order_queue, skb1, skb);
4568
4569 /* And clean segments covered by new one as whole. */
4570 while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) {
4571 skb1 = skb_queue_next(&tp->out_of_order_queue, skb);
4572
4573 if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
4574 break;
4575 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
4576 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4577 end_seq);
4578 break;
4579 }
4580 __skb_unlink(skb1, &tp->out_of_order_queue);
4581 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
4582 TCP_SKB_CB(skb1)->end_seq);
4583 __kfree_skb(skb1);
4584 }
4585
4586add_sack:
4587 if (tcp_is_sack(tp))
4588 tcp_sack_new_ofo_skb(sk, seq, end_seq);
4589 }
4590}
4591
4592static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
4593 struct sk_buff_head *list)
4594{
4595 struct sk_buff *next = NULL;
4596
4597 if (!skb_queue_is_last(list, skb))
4598 next = skb_queue_next(list, skb);
4599
4600 __skb_unlink(skb, list);
4601 __kfree_skb(skb);
4602 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
4603
4604 return next;
4605}
4606
4607/* Collapse contiguous sequence of skbs head..tail with
4608 * sequence numbers start..end.
4609 *
4610 * If tail is NULL, this means until the end of the list.
4611 *
4612 * Segments with FIN/SYN are not collapsed (only because this
4613 * simplifies code)
4614 */
4615static void
4616tcp_collapse(struct sock *sk, struct sk_buff_head *list,
4617 struct sk_buff *head, struct sk_buff *tail,
4618 u32 start, u32 end)
4619{
4620 struct sk_buff *skb, *n;
4621 bool end_of_skbs;
4622
4623 /* First, check that queue is collapsible and find
4624 * the point where collapsing can be useful. */
4625 skb = head;
4626restart:
4627 end_of_skbs = true;
4628 skb_queue_walk_from_safe(list, skb, n) {
4629 if (skb == tail)
4630 break;
4631 /* No new bits? It is possible on ofo queue. */
4632 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4633 skb = tcp_collapse_one(sk, skb, list);
4634 if (!skb)
4635 break;
4636 goto restart;
4637 }
4638
4639 /* The first skb to collapse is:
4640 * - not SYN/FIN and
4641 * - bloated or contains data before "start" or
4642 * overlaps to the next one.
4643 */
4644 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin &&
4645 (tcp_win_from_space(skb->truesize) > skb->len ||
4646 before(TCP_SKB_CB(skb)->seq, start))) {
4647 end_of_skbs = false;
4648 break;
4649 }
4650
4651 if (!skb_queue_is_last(list, skb)) {
4652 struct sk_buff *next = skb_queue_next(list, skb);
4653 if (next != tail &&
4654 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) {
4655 end_of_skbs = false;
4656 break;
4657 }
4658 }
4659
4660 /* Decided to skip this, advance start seq. */
4661 start = TCP_SKB_CB(skb)->end_seq;
4662 }
4663 if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin)
4664 return;
4665
4666 while (before(start, end)) {
4667 struct sk_buff *nskb;
4668 unsigned int header = skb_headroom(skb);
4669 int copy = SKB_MAX_ORDER(header, 0);
4670
4671 /* Too big header? This can happen with IPv6. */
4672 if (copy < 0)
4673 return;
4674 if (end - start < copy)
4675 copy = end - start;
4676 nskb = alloc_skb(copy + header, GFP_ATOMIC);
4677 if (!nskb)
4678 return;
4679
4680 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head);
4681 skb_set_network_header(nskb, (skb_network_header(skb) -
4682 skb->head));
4683 skb_set_transport_header(nskb, (skb_transport_header(skb) -
4684 skb->head));
4685 skb_reserve(nskb, header);
4686 memcpy(nskb->head, skb->head, header);
4687 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
4688 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
4689 __skb_queue_before(list, skb, nskb);
4690 skb_set_owner_r(nskb, sk);
4691
4692 /* Copy data, releasing collapsed skbs. */
4693 while (copy > 0) {
4694 int offset = start - TCP_SKB_CB(skb)->seq;
4695 int size = TCP_SKB_CB(skb)->end_seq - start;
4696
4697 BUG_ON(offset < 0);
4698 if (size > 0) {
4699 size = min(copy, size);
4700 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
4701 BUG();
4702 TCP_SKB_CB(nskb)->end_seq += size;
4703 copy -= size;
4704 start += size;
4705 }
4706 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
4707 skb = tcp_collapse_one(sk, skb, list);
4708 if (!skb ||
4709 skb == tail ||
4710 tcp_hdr(skb)->syn ||
4711 tcp_hdr(skb)->fin)
4712 return;
4713 }
4714 }
4715 }
4716}
4717
4718/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4719 * and tcp_collapse() them until all the queue is collapsed.
4720 */
4721static void tcp_collapse_ofo_queue(struct sock *sk)
4722{
4723 struct tcp_sock *tp = tcp_sk(sk);
4724 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
4725 struct sk_buff *head;
4726 u32 start, end;
4727
4728 if (skb == NULL)
4729 return;
4730
4731 start = TCP_SKB_CB(skb)->seq;
4732 end = TCP_SKB_CB(skb)->end_seq;
4733 head = skb;
4734
4735 for (;;) {
4736 struct sk_buff *next = NULL;
4737
4738 if (!skb_queue_is_last(&tp->out_of_order_queue, skb))
4739 next = skb_queue_next(&tp->out_of_order_queue, skb);
4740 skb = next;
4741
4742 /* Segment is terminated when we see gap or when
4743 * we are at the end of all the queue. */
4744 if (!skb ||
4745 after(TCP_SKB_CB(skb)->seq, end) ||
4746 before(TCP_SKB_CB(skb)->end_seq, start)) {
4747 tcp_collapse(sk, &tp->out_of_order_queue,
4748 head, skb, start, end);
4749 head = skb;
4750 if (!skb)
4751 break;
4752 /* Start new segment */
4753 start = TCP_SKB_CB(skb)->seq;
4754 end = TCP_SKB_CB(skb)->end_seq;
4755 } else {
4756 if (before(TCP_SKB_CB(skb)->seq, start))
4757 start = TCP_SKB_CB(skb)->seq;
4758 if (after(TCP_SKB_CB(skb)->end_seq, end))
4759 end = TCP_SKB_CB(skb)->end_seq;
4760 }
4761 }
4762}
4763
4764/*
4765 * Purge the out-of-order queue.
4766 * Return true if queue was pruned.
4767 */
4768static int tcp_prune_ofo_queue(struct sock *sk)
4769{
4770 struct tcp_sock *tp = tcp_sk(sk);
4771 int res = 0;
4772
4773 if (!skb_queue_empty(&tp->out_of_order_queue)) {
4774 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED);
4775 __skb_queue_purge(&tp->out_of_order_queue);
4776
4777 /* Reset SACK state. A conforming SACK implementation will
4778 * do the same at a timeout based retransmit. When a connection
4779 * is in a sad state like this, we care only about integrity
4780 * of the connection not performance.
4781 */
4782 if (tp->rx_opt.sack_ok)
4783 tcp_sack_reset(&tp->rx_opt);
4784 sk_mem_reclaim(sk);
4785 res = 1;
4786 }
4787 return res;
4788}
4789
4790/* Reduce allocated memory if we can, trying to get
4791 * the socket within its memory limits again.
4792 *
4793 * Return less than zero if we should start dropping frames
4794 * until the socket owning process reads some of the data
4795 * to stabilize the situation.
4796 */
4797static int tcp_prune_queue(struct sock *sk)
4798{
4799 struct tcp_sock *tp = tcp_sk(sk);
4800
4801 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
4802
4803 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED);
4804
4805 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
4806 tcp_clamp_window(sk);
4807 else if (tcp_memory_pressure)
4808 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
4809
4810 tcp_collapse_ofo_queue(sk);
4811 if (!skb_queue_empty(&sk->sk_receive_queue))
4812 tcp_collapse(sk, &sk->sk_receive_queue,
4813 skb_peek(&sk->sk_receive_queue),
4814 NULL,
4815 tp->copied_seq, tp->rcv_nxt);
4816 sk_mem_reclaim(sk);
4817
4818 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4819 return 0;
4820
4821 /* Collapsing did not help, destructive actions follow.
4822 * This must not ever occur. */
4823
4824 tcp_prune_ofo_queue(sk);
4825
4826 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
4827 return 0;
4828
4829 /* If we are really being abused, tell the caller to silently
4830 * drop receive data on the floor. It will get retransmitted
4831 * and hopefully then we'll have sufficient space.
4832 */
4833 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED);
4834
4835 /* Massive buffer overcommit. */
4836 tp->pred_flags = 0;
4837 return -1;
4838}
4839
4840/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4841 * As additional protections, we do not touch cwnd in retransmission phases,
4842 * and if application hit its sndbuf limit recently.
4843 */
4844void tcp_cwnd_application_limited(struct sock *sk)
4845{
4846 struct tcp_sock *tp = tcp_sk(sk);
4847
4848 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
4849 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
4850 /* Limited by application or receiver window. */
4851 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
4852 u32 win_used = max(tp->snd_cwnd_used, init_win);
4853 if (win_used < tp->snd_cwnd) {
4854 tp->snd_ssthresh = tcp_current_ssthresh(sk);
4855 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
4856 }
4857 tp->snd_cwnd_used = 0;
4858 }
4859 tp->snd_cwnd_stamp = tcp_time_stamp;
4860}
4861
4862static int tcp_should_expand_sndbuf(struct sock *sk)
4863{
4864 struct tcp_sock *tp = tcp_sk(sk);
4865
4866 /* If the user specified a specific send buffer setting, do
4867 * not modify it.
4868 */
4869 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
4870 return 0;
4871
4872 /* If we are under global TCP memory pressure, do not expand. */
4873 if (tcp_memory_pressure)
4874 return 0;
4875
4876 /* If we are under soft global TCP memory pressure, do not expand. */
4877 if (atomic_long_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
4878 return 0;
4879
4880 /* If we filled the congestion window, do not expand. */
4881 if (tp->packets_out >= tp->snd_cwnd)
4882 return 0;
4883
4884 return 1;
4885}
4886
4887/* When incoming ACK allowed to free some skb from write_queue,
4888 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4889 * on the exit from tcp input handler.
4890 *
4891 * PROBLEM: sndbuf expansion does not work well with largesend.
4892 */
4893static void tcp_new_space(struct sock *sk)
4894{
4895 struct tcp_sock *tp = tcp_sk(sk);
4896
4897 if (tcp_should_expand_sndbuf(sk)) {
4898 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
4899 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
4900 int demanded = max_t(unsigned int, tp->snd_cwnd,
4901 tp->reordering + 1);
4902 sndmem *= 2 * demanded;
4903 if (sndmem > sk->sk_sndbuf)
4904 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
4905 tp->snd_cwnd_stamp = tcp_time_stamp;
4906 }
4907
4908 sk->sk_write_space(sk);
4909}
4910
4911static void tcp_check_space(struct sock *sk)
4912{
4913 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
4914 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
4915 if (sk->sk_socket &&
4916 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
4917 tcp_new_space(sk);
4918 }
4919}
4920
4921static inline void tcp_data_snd_check(struct sock *sk)
4922{
4923 tcp_push_pending_frames(sk);
4924 tcp_check_space(sk);
4925}
4926
4927/*
4928 * Check if sending an ack is needed.
4929 */
4930static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
4931{
4932 struct tcp_sock *tp = tcp_sk(sk);
4933
4934 /* More than one full frame received... */
4935 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
4936 /* ... and right edge of window advances far enough.
4937 * (tcp_recvmsg() will send ACK otherwise). Or...
4938 */
4939 __tcp_select_window(sk) >= tp->rcv_wnd) ||
4940 /* We ACK each frame or... */
4941 tcp_in_quickack_mode(sk) ||
4942 /* We have out of order data. */
4943 (ofo_possible && skb_peek(&tp->out_of_order_queue))) {
4944 /* Then ack it now */
4945 tcp_send_ack(sk);
4946 } else {
4947 /* Else, send delayed ack. */
4948 tcp_send_delayed_ack(sk);
4949 }
4950}
4951
4952static inline void tcp_ack_snd_check(struct sock *sk)
4953{
4954 if (!inet_csk_ack_scheduled(sk)) {
4955 /* We sent a data segment already. */
4956 return;
4957 }
4958 __tcp_ack_snd_check(sk, 1);
4959}
4960
4961/*
4962 * This routine is only called when we have urgent data
4963 * signaled. Its the 'slow' part of tcp_urg. It could be
4964 * moved inline now as tcp_urg is only called from one
4965 * place. We handle URGent data wrong. We have to - as
4966 * BSD still doesn't use the correction from RFC961.
4967 * For 1003.1g we should support a new option TCP_STDURG to permit
4968 * either form (or just set the sysctl tcp_stdurg).
4969 */
4970
4971static void tcp_check_urg(struct sock *sk, struct tcphdr *th)
4972{
4973 struct tcp_sock *tp = tcp_sk(sk);
4974 u32 ptr = ntohs(th->urg_ptr);
4975
4976 if (ptr && !sysctl_tcp_stdurg)
4977 ptr--;
4978 ptr += ntohl(th->seq);
4979
4980 /* Ignore urgent data that we've already seen and read. */
4981 if (after(tp->copied_seq, ptr))
4982 return;
4983
4984 /* Do not replay urg ptr.
4985 *
4986 * NOTE: interesting situation not covered by specs.
4987 * Misbehaving sender may send urg ptr, pointing to segment,
4988 * which we already have in ofo queue. We are not able to fetch
4989 * such data and will stay in TCP_URG_NOTYET until will be eaten
4990 * by recvmsg(). Seems, we are not obliged to handle such wicked
4991 * situations. But it is worth to think about possibility of some
4992 * DoSes using some hypothetical application level deadlock.
4993 */
4994 if (before(ptr, tp->rcv_nxt))
4995 return;
4996
4997 /* Do we already have a newer (or duplicate) urgent pointer? */
4998 if (tp->urg_data && !after(ptr, tp->urg_seq))
4999 return;
5000
5001 /* Tell the world about our new urgent pointer. */
5002 sk_send_sigurg(sk);
5003
5004 /* We may be adding urgent data when the last byte read was
5005 * urgent. To do this requires some care. We cannot just ignore
5006 * tp->copied_seq since we would read the last urgent byte again
5007 * as data, nor can we alter copied_seq until this data arrives
5008 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5009 *
5010 * NOTE. Double Dutch. Rendering to plain English: author of comment
5011 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5012 * and expect that both A and B disappear from stream. This is _wrong_.
5013 * Though this happens in BSD with high probability, this is occasional.
5014 * Any application relying on this is buggy. Note also, that fix "works"
5015 * only in this artificial test. Insert some normal data between A and B and we will
5016 * decline of BSD again. Verdict: it is better to remove to trap
5017 * buggy users.
5018 */
5019 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
5020 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) {
5021 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
5022 tp->copied_seq++;
5023 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
5024 __skb_unlink(skb, &sk->sk_receive_queue);
5025 __kfree_skb(skb);
5026 }
5027 }
5028
5029 tp->urg_data = TCP_URG_NOTYET;
5030 tp->urg_seq = ptr;
5031
5032 /* Disable header prediction. */
5033 tp->pred_flags = 0;
5034}
5035
5036/* This is the 'fast' part of urgent handling. */
5037static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
5038{
5039 struct tcp_sock *tp = tcp_sk(sk);
5040
5041 /* Check if we get a new urgent pointer - normally not. */
5042 if (th->urg)
5043 tcp_check_urg(sk, th);
5044
5045 /* Do we wait for any urgent data? - normally not... */
5046 if (tp->urg_data == TCP_URG_NOTYET) {
5047 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
5048 th->syn;
5049
5050 /* Is the urgent pointer pointing into this packet? */
5051 if (ptr < skb->len) {
5052 u8 tmp;
5053 if (skb_copy_bits(skb, ptr, &tmp, 1))
5054 BUG();
5055 tp->urg_data = TCP_URG_VALID | tmp;
5056 if (!sock_flag(sk, SOCK_DEAD))
5057 sk->sk_data_ready(sk, 0);
5058 }
5059 }
5060}
5061
5062static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
5063{
5064 struct tcp_sock *tp = tcp_sk(sk);
5065 int chunk = skb->len - hlen;
5066 int err;
5067
5068 local_bh_enable();
5069 if (skb_csum_unnecessary(skb))
5070 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
5071 else
5072 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
5073 tp->ucopy.iov);
5074
5075 if (!err) {
5076 tp->ucopy.len -= chunk;
5077 tp->copied_seq += chunk;
5078 tcp_rcv_space_adjust(sk);
5079 }
5080
5081 local_bh_disable();
5082 return err;
5083}
5084
5085static __sum16 __tcp_checksum_complete_user(struct sock *sk,
5086 struct sk_buff *skb)
5087{
5088 __sum16 result;
5089
5090 if (sock_owned_by_user(sk)) {
5091 local_bh_enable();
5092 result = __tcp_checksum_complete(skb);
5093 local_bh_disable();
5094 } else {
5095 result = __tcp_checksum_complete(skb);
5096 }
5097 return result;
5098}
5099
5100static inline int tcp_checksum_complete_user(struct sock *sk,
5101 struct sk_buff *skb)
5102{
5103 return !skb_csum_unnecessary(skb) &&
5104 __tcp_checksum_complete_user(sk, skb);
5105}
5106
5107#ifdef CONFIG_NET_DMA
5108static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb,
5109 int hlen)
5110{
5111 struct tcp_sock *tp = tcp_sk(sk);
5112 int chunk = skb->len - hlen;
5113 int dma_cookie;
5114 int copied_early = 0;
5115
5116 if (tp->ucopy.wakeup)
5117 return 0;
5118
5119 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
5120 tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY);
5121
5122 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) {
5123
5124 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
5125 skb, hlen,
5126 tp->ucopy.iov, chunk,
5127 tp->ucopy.pinned_list);
5128
5129 if (dma_cookie < 0)
5130 goto out;
5131
5132 tp->ucopy.dma_cookie = dma_cookie;
5133 copied_early = 1;
5134
5135 tp->ucopy.len -= chunk;
5136 tp->copied_seq += chunk;
5137 tcp_rcv_space_adjust(sk);
5138
5139 if ((tp->ucopy.len == 0) ||
5140 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) ||
5141 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
5142 tp->ucopy.wakeup = 1;
5143 sk->sk_data_ready(sk, 0);
5144 }
5145 } else if (chunk > 0) {
5146 tp->ucopy.wakeup = 1;
5147 sk->sk_data_ready(sk, 0);
5148 }
5149out:
5150 return copied_early;
5151}
5152#endif /* CONFIG_NET_DMA */
5153
5154/* Does PAWS and seqno based validation of an incoming segment, flags will
5155 * play significant role here.
5156 */
5157static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
5158 struct tcphdr *th, int syn_inerr)
5159{
5160 u8 *hash_location;
5161 struct tcp_sock *tp = tcp_sk(sk);
5162
5163 /* RFC1323: H1. Apply PAWS check first. */
5164 if (tcp_fast_parse_options(skb, th, tp, &hash_location) &&
5165 tp->rx_opt.saw_tstamp &&
5166 tcp_paws_discard(sk, skb)) {
5167 if (!th->rst) {
5168 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
5169 tcp_send_dupack(sk, skb);
5170 goto discard;
5171 }
5172 /* Reset is accepted even if it did not pass PAWS. */
5173 }
5174
5175 /* Step 1: check sequence number */
5176 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
5177 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5178 * (RST) segments are validated by checking their SEQ-fields."
5179 * And page 69: "If an incoming segment is not acceptable,
5180 * an acknowledgment should be sent in reply (unless the RST
5181 * bit is set, if so drop the segment and return)".
5182 */
5183 if (!th->rst)
5184 tcp_send_dupack(sk, skb);
5185 goto discard;
5186 }
5187
5188 /* Step 2: check RST bit */
5189 if (th->rst) {
5190 tcp_reset(sk);
5191 goto discard;
5192 }
5193
5194 /* ts_recent update must be made after we are sure that the packet
5195 * is in window.
5196 */
5197 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
5198
5199 /* step 3: check security and precedence [ignored] */
5200
5201 /* step 4: Check for a SYN in window. */
5202 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
5203 if (syn_inerr)
5204 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5205 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
5206 tcp_reset(sk);
5207 return -1;
5208 }
5209
5210 return 1;
5211
5212discard:
5213 __kfree_skb(skb);
5214 return 0;
5215}
5216
5217/*
5218 * TCP receive function for the ESTABLISHED state.
5219 *
5220 * It is split into a fast path and a slow path. The fast path is
5221 * disabled when:
5222 * - A zero window was announced from us - zero window probing
5223 * is only handled properly in the slow path.
5224 * - Out of order segments arrived.
5225 * - Urgent data is expected.
5226 * - There is no buffer space left
5227 * - Unexpected TCP flags/window values/header lengths are received
5228 * (detected by checking the TCP header against pred_flags)
5229 * - Data is sent in both directions. Fast path only supports pure senders
5230 * or pure receivers (this means either the sequence number or the ack
5231 * value must stay constant)
5232 * - Unexpected TCP option.
5233 *
5234 * When these conditions are not satisfied it drops into a standard
5235 * receive procedure patterned after RFC793 to handle all cases.
5236 * The first three cases are guaranteed by proper pred_flags setting,
5237 * the rest is checked inline. Fast processing is turned on in
5238 * tcp_data_queue when everything is OK.
5239 */
5240int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
5241 struct tcphdr *th, unsigned len)
5242{
5243 struct tcp_sock *tp = tcp_sk(sk);
5244 int res;
5245
5246 /*
5247 * Header prediction.
5248 * The code loosely follows the one in the famous
5249 * "30 instruction TCP receive" Van Jacobson mail.
5250 *
5251 * Van's trick is to deposit buffers into socket queue
5252 * on a device interrupt, to call tcp_recv function
5253 * on the receive process context and checksum and copy
5254 * the buffer to user space. smart...
5255 *
5256 * Our current scheme is not silly either but we take the
5257 * extra cost of the net_bh soft interrupt processing...
5258 * We do checksum and copy also but from device to kernel.
5259 */
5260
5261 tp->rx_opt.saw_tstamp = 0;
5262
5263 /* pred_flags is 0xS?10 << 16 + snd_wnd
5264 * if header_prediction is to be made
5265 * 'S' will always be tp->tcp_header_len >> 2
5266 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5267 * turn it off (when there are holes in the receive
5268 * space for instance)
5269 * PSH flag is ignored.
5270 */
5271
5272 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
5273 TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
5274 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
5275 int tcp_header_len = tp->tcp_header_len;
5276
5277 /* Timestamp header prediction: tcp_header_len
5278 * is automatically equal to th->doff*4 due to pred_flags
5279 * match.
5280 */
5281
5282 /* Check timestamp */
5283 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
5284 /* No? Slow path! */
5285 if (!tcp_parse_aligned_timestamp(tp, th))
5286 goto slow_path;
5287
5288 /* If PAWS failed, check it more carefully in slow path */
5289 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
5290 goto slow_path;
5291
5292 /* DO NOT update ts_recent here, if checksum fails
5293 * and timestamp was corrupted part, it will result
5294 * in a hung connection since we will drop all
5295 * future packets due to the PAWS test.
5296 */
5297 }
5298
5299 if (len <= tcp_header_len) {
5300 /* Bulk data transfer: sender */
5301 if (len == tcp_header_len) {
5302 /* Predicted packet is in window by definition.
5303 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5304 * Hence, check seq<=rcv_wup reduces to:
5305 */
5306 if (tcp_header_len ==
5307 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5308 tp->rcv_nxt == tp->rcv_wup)
5309 tcp_store_ts_recent(tp);
5310
5311 /* We know that such packets are checksummed
5312 * on entry.
5313 */
5314 tcp_ack(sk, skb, 0);
5315 __kfree_skb(skb);
5316 tcp_data_snd_check(sk);
5317 return 0;
5318 } else { /* Header too small */
5319 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5320 goto discard;
5321 }
5322 } else {
5323 int eaten = 0;
5324 int copied_early = 0;
5325
5326 if (tp->copied_seq == tp->rcv_nxt &&
5327 len - tcp_header_len <= tp->ucopy.len) {
5328#ifdef CONFIG_NET_DMA
5329 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
5330 copied_early = 1;
5331 eaten = 1;
5332 }
5333#endif
5334 if (tp->ucopy.task == current &&
5335 sock_owned_by_user(sk) && !copied_early) {
5336 __set_current_state(TASK_RUNNING);
5337
5338 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
5339 eaten = 1;
5340 }
5341 if (eaten) {
5342 /* Predicted packet is in window by definition.
5343 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5344 * Hence, check seq<=rcv_wup reduces to:
5345 */
5346 if (tcp_header_len ==
5347 (sizeof(struct tcphdr) +
5348 TCPOLEN_TSTAMP_ALIGNED) &&
5349 tp->rcv_nxt == tp->rcv_wup)
5350 tcp_store_ts_recent(tp);
5351
5352 tcp_rcv_rtt_measure_ts(sk, skb);
5353
5354 __skb_pull(skb, tcp_header_len);
5355 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
5356 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER);
5357 }
5358 if (copied_early)
5359 tcp_cleanup_rbuf(sk, skb->len);
5360 }
5361 if (!eaten) {
5362 if (tcp_checksum_complete_user(sk, skb))
5363 goto csum_error;
5364
5365 /* Predicted packet is in window by definition.
5366 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5367 * Hence, check seq<=rcv_wup reduces to:
5368 */
5369 if (tcp_header_len ==
5370 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
5371 tp->rcv_nxt == tp->rcv_wup)
5372 tcp_store_ts_recent(tp);
5373
5374 tcp_rcv_rtt_measure_ts(sk, skb);
5375
5376 if ((int)skb->truesize > sk->sk_forward_alloc)
5377 goto step5;
5378
5379 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS);
5380
5381 /* Bulk data transfer: receiver */
5382 __skb_pull(skb, tcp_header_len);
5383 __skb_queue_tail(&sk->sk_receive_queue, skb);
5384 skb_set_owner_r(skb, sk);
5385 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
5386 }
5387
5388 tcp_event_data_recv(sk, skb);
5389
5390 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
5391 /* Well, only one small jumplet in fast path... */
5392 tcp_ack(sk, skb, FLAG_DATA);
5393 tcp_data_snd_check(sk);
5394 if (!inet_csk_ack_scheduled(sk))
5395 goto no_ack;
5396 }
5397
5398 if (!copied_early || tp->rcv_nxt != tp->rcv_wup)
5399 __tcp_ack_snd_check(sk, 0);
5400no_ack:
5401#ifdef CONFIG_NET_DMA
5402 if (copied_early)
5403 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
5404 else
5405#endif
5406 if (eaten)
5407 __kfree_skb(skb);
5408 else
5409 sk->sk_data_ready(sk, 0);
5410 return 0;
5411 }
5412 }
5413
5414slow_path:
5415 if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
5416 goto csum_error;
5417
5418 /*
5419 * Standard slow path.
5420 */
5421
5422 res = tcp_validate_incoming(sk, skb, th, 1);
5423 if (res <= 0)
5424 return -res;
5425
5426step5:
5427 if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0)
5428 goto discard;
5429
5430 tcp_rcv_rtt_measure_ts(sk, skb);
5431
5432 /* Process urgent data. */
5433 tcp_urg(sk, skb, th);
5434
5435 /* step 7: process the segment text */
5436 tcp_data_queue(sk, skb);
5437
5438 tcp_data_snd_check(sk);
5439 tcp_ack_snd_check(sk);
5440 return 0;
5441
5442csum_error:
5443 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
5444
5445discard:
5446 __kfree_skb(skb);
5447 return 0;
5448}
5449EXPORT_SYMBOL(tcp_rcv_established);
5450
5451static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
5452 struct tcphdr *th, unsigned len)
5453{
5454 u8 *hash_location;
5455 struct inet_connection_sock *icsk = inet_csk(sk);
5456 struct tcp_sock *tp = tcp_sk(sk);
5457 struct tcp_cookie_values *cvp = tp->cookie_values;
5458 int saved_clamp = tp->rx_opt.mss_clamp;
5459
5460 tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0);
5461
5462 if (th->ack) {
5463 /* rfc793:
5464 * "If the state is SYN-SENT then
5465 * first check the ACK bit
5466 * If the ACK bit is set
5467 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5468 * a reset (unless the RST bit is set, if so drop
5469 * the segment and return)"
5470 *
5471 * We do not send data with SYN, so that RFC-correct
5472 * test reduces to:
5473 */
5474 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
5475 goto reset_and_undo;
5476
5477 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
5478 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
5479 tcp_time_stamp)) {
5480 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED);
5481 goto reset_and_undo;
5482 }
5483
5484 /* Now ACK is acceptable.
5485 *
5486 * "If the RST bit is set
5487 * If the ACK was acceptable then signal the user "error:
5488 * connection reset", drop the segment, enter CLOSED state,
5489 * delete TCB, and return."
5490 */
5491
5492 if (th->rst) {
5493 tcp_reset(sk);
5494 goto discard;
5495 }
5496
5497 /* rfc793:
5498 * "fifth, if neither of the SYN or RST bits is set then
5499 * drop the segment and return."
5500 *
5501 * See note below!
5502 * --ANK(990513)
5503 */
5504 if (!th->syn)
5505 goto discard_and_undo;
5506
5507 /* rfc793:
5508 * "If the SYN bit is on ...
5509 * are acceptable then ...
5510 * (our SYN has been ACKed), change the connection
5511 * state to ESTABLISHED..."
5512 */
5513
5514 TCP_ECN_rcv_synack(tp, th);
5515
5516 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
5517 tcp_ack(sk, skb, FLAG_SLOWPATH);
5518
5519 /* Ok.. it's good. Set up sequence numbers and
5520 * move to established.
5521 */
5522 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5523 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5524
5525 /* RFC1323: The window in SYN & SYN/ACK segments is
5526 * never scaled.
5527 */
5528 tp->snd_wnd = ntohs(th->window);
5529 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5530
5531 if (!tp->rx_opt.wscale_ok) {
5532 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
5533 tp->window_clamp = min(tp->window_clamp, 65535U);
5534 }
5535
5536 if (tp->rx_opt.saw_tstamp) {
5537 tp->rx_opt.tstamp_ok = 1;
5538 tp->tcp_header_len =
5539 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5540 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5541 tcp_store_ts_recent(tp);
5542 } else {
5543 tp->tcp_header_len = sizeof(struct tcphdr);
5544 }
5545
5546 if (tcp_is_sack(tp) && sysctl_tcp_fack)
5547 tcp_enable_fack(tp);
5548
5549 tcp_mtup_init(sk);
5550 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5551 tcp_initialize_rcv_mss(sk);
5552
5553 /* Remember, tcp_poll() does not lock socket!
5554 * Change state from SYN-SENT only after copied_seq
5555 * is initialized. */
5556 tp->copied_seq = tp->rcv_nxt;
5557
5558 if (cvp != NULL &&
5559 cvp->cookie_pair_size > 0 &&
5560 tp->rx_opt.cookie_plus > 0) {
5561 int cookie_size = tp->rx_opt.cookie_plus
5562 - TCPOLEN_COOKIE_BASE;
5563 int cookie_pair_size = cookie_size
5564 + cvp->cookie_desired;
5565
5566 /* A cookie extension option was sent and returned.
5567 * Note that each incoming SYNACK replaces the
5568 * Responder cookie. The initial exchange is most
5569 * fragile, as protection against spoofing relies
5570 * entirely upon the sequence and timestamp (above).
5571 * This replacement strategy allows the correct pair to
5572 * pass through, while any others will be filtered via
5573 * Responder verification later.
5574 */
5575 if (sizeof(cvp->cookie_pair) >= cookie_pair_size) {
5576 memcpy(&cvp->cookie_pair[cvp->cookie_desired],
5577 hash_location, cookie_size);
5578 cvp->cookie_pair_size = cookie_pair_size;
5579 }
5580 }
5581
5582 smp_mb();
5583 tcp_set_state(sk, TCP_ESTABLISHED);
5584
5585 security_inet_conn_established(sk, skb);
5586
5587 /* Make sure socket is routed, for correct metrics. */
5588 icsk->icsk_af_ops->rebuild_header(sk);
5589
5590 tcp_init_metrics(sk);
5591
5592 tcp_init_congestion_control(sk);
5593
5594 /* Prevent spurious tcp_cwnd_restart() on first data
5595 * packet.
5596 */
5597 tp->lsndtime = tcp_time_stamp;
5598
5599 tcp_init_buffer_space(sk);
5600
5601 if (sock_flag(sk, SOCK_KEEPOPEN))
5602 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
5603
5604 if (!tp->rx_opt.snd_wscale)
5605 __tcp_fast_path_on(tp, tp->snd_wnd);
5606 else
5607 tp->pred_flags = 0;
5608
5609 if (!sock_flag(sk, SOCK_DEAD)) {
5610 sk->sk_state_change(sk);
5611 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
5612 }
5613
5614 if (sk->sk_write_pending ||
5615 icsk->icsk_accept_queue.rskq_defer_accept ||
5616 icsk->icsk_ack.pingpong) {
5617 /* Save one ACK. Data will be ready after
5618 * several ticks, if write_pending is set.
5619 *
5620 * It may be deleted, but with this feature tcpdumps
5621 * look so _wonderfully_ clever, that I was not able
5622 * to stand against the temptation 8) --ANK
5623 */
5624 inet_csk_schedule_ack(sk);
5625 icsk->icsk_ack.lrcvtime = tcp_time_stamp;
5626 icsk->icsk_ack.ato = TCP_ATO_MIN;
5627 tcp_incr_quickack(sk);
5628 tcp_enter_quickack_mode(sk);
5629 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
5630 TCP_DELACK_MAX, TCP_RTO_MAX);
5631
5632discard:
5633 __kfree_skb(skb);
5634 return 0;
5635 } else {
5636 tcp_send_ack(sk);
5637 }
5638 return -1;
5639 }
5640
5641 /* No ACK in the segment */
5642
5643 if (th->rst) {
5644 /* rfc793:
5645 * "If the RST bit is set
5646 *
5647 * Otherwise (no ACK) drop the segment and return."
5648 */
5649
5650 goto discard_and_undo;
5651 }
5652
5653 /* PAWS check. */
5654 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp &&
5655 tcp_paws_reject(&tp->rx_opt, 0))
5656 goto discard_and_undo;
5657
5658 if (th->syn) {
5659 /* We see SYN without ACK. It is attempt of
5660 * simultaneous connect with crossed SYNs.
5661 * Particularly, it can be connect to self.
5662 */
5663 tcp_set_state(sk, TCP_SYN_RECV);
5664
5665 if (tp->rx_opt.saw_tstamp) {
5666 tp->rx_opt.tstamp_ok = 1;
5667 tcp_store_ts_recent(tp);
5668 tp->tcp_header_len =
5669 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
5670 } else {
5671 tp->tcp_header_len = sizeof(struct tcphdr);
5672 }
5673
5674 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
5675 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
5676
5677 /* RFC1323: The window in SYN & SYN/ACK segments is
5678 * never scaled.
5679 */
5680 tp->snd_wnd = ntohs(th->window);
5681 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
5682 tp->max_window = tp->snd_wnd;
5683
5684 TCP_ECN_rcv_syn(tp, th);
5685
5686 tcp_mtup_init(sk);
5687 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
5688 tcp_initialize_rcv_mss(sk);
5689
5690 tcp_send_synack(sk);
5691#if 0
5692 /* Note, we could accept data and URG from this segment.
5693 * There are no obstacles to make this.
5694 *
5695 * However, if we ignore data in ACKless segments sometimes,
5696 * we have no reasons to accept it sometimes.
5697 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5698 * is not flawless. So, discard packet for sanity.
5699 * Uncomment this return to process the data.
5700 */
5701 return -1;
5702#else
5703 goto discard;
5704#endif
5705 }
5706 /* "fifth, if neither of the SYN or RST bits is set then
5707 * drop the segment and return."
5708 */
5709
5710discard_and_undo:
5711 tcp_clear_options(&tp->rx_opt);
5712 tp->rx_opt.mss_clamp = saved_clamp;
5713 goto discard;
5714
5715reset_and_undo:
5716 tcp_clear_options(&tp->rx_opt);
5717 tp->rx_opt.mss_clamp = saved_clamp;
5718 return 1;
5719}
5720
5721/*
5722 * This function implements the receiving procedure of RFC 793 for
5723 * all states except ESTABLISHED and TIME_WAIT.
5724 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5725 * address independent.
5726 */
5727
5728int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
5729 struct tcphdr *th, unsigned len)
5730{
5731 struct tcp_sock *tp = tcp_sk(sk);
5732 struct inet_connection_sock *icsk = inet_csk(sk);
5733 int queued = 0;
5734 int res;
5735
5736 tp->rx_opt.saw_tstamp = 0;
5737
5738 switch (sk->sk_state) {
5739 case TCP_CLOSE:
5740 goto discard;
5741
5742 case TCP_LISTEN:
5743 if (th->ack)
5744 return 1;
5745
5746 if (th->rst)
5747 goto discard;
5748
5749 if (th->syn) {
5750 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
5751 return 1;
5752
5753 /* Now we have several options: In theory there is
5754 * nothing else in the frame. KA9Q has an option to
5755 * send data with the syn, BSD accepts data with the
5756 * syn up to the [to be] advertised window and
5757 * Solaris 2.1 gives you a protocol error. For now
5758 * we just ignore it, that fits the spec precisely
5759 * and avoids incompatibilities. It would be nice in
5760 * future to drop through and process the data.
5761 *
5762 * Now that TTCP is starting to be used we ought to
5763 * queue this data.
5764 * But, this leaves one open to an easy denial of
5765 * service attack, and SYN cookies can't defend
5766 * against this problem. So, we drop the data
5767 * in the interest of security over speed unless
5768 * it's still in use.
5769 */
5770 kfree_skb(skb);
5771 return 0;
5772 }
5773 goto discard;
5774
5775 case TCP_SYN_SENT:
5776 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
5777 if (queued >= 0)
5778 return queued;
5779
5780 /* Do step6 onward by hand. */
5781 tcp_urg(sk, skb, th);
5782 __kfree_skb(skb);
5783 tcp_data_snd_check(sk);
5784 return 0;
5785 }
5786
5787 res = tcp_validate_incoming(sk, skb, th, 0);
5788 if (res <= 0)
5789 return -res;
5790
5791 /* step 5: check the ACK field */
5792 if (th->ack) {
5793 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0;
5794
5795 switch (sk->sk_state) {
5796 case TCP_SYN_RECV:
5797 if (acceptable) {
5798 tp->copied_seq = tp->rcv_nxt;
5799 smp_mb();
5800 tcp_set_state(sk, TCP_ESTABLISHED);
5801 sk->sk_state_change(sk);
5802
5803 /* Note, that this wakeup is only for marginal
5804 * crossed SYN case. Passively open sockets
5805 * are not waked up, because sk->sk_sleep ==
5806 * NULL and sk->sk_socket == NULL.
5807 */
5808 if (sk->sk_socket)
5809 sk_wake_async(sk,
5810 SOCK_WAKE_IO, POLL_OUT);
5811
5812 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
5813 tp->snd_wnd = ntohs(th->window) <<
5814 tp->rx_opt.snd_wscale;
5815 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
5816
5817 if (tp->rx_opt.tstamp_ok)
5818 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
5819
5820 /* Make sure socket is routed, for
5821 * correct metrics.
5822 */
5823 icsk->icsk_af_ops->rebuild_header(sk);
5824
5825 tcp_init_metrics(sk);
5826
5827 tcp_init_congestion_control(sk);
5828
5829 /* Prevent spurious tcp_cwnd_restart() on
5830 * first data packet.
5831 */
5832 tp->lsndtime = tcp_time_stamp;
5833
5834 tcp_mtup_init(sk);
5835 tcp_initialize_rcv_mss(sk);
5836 tcp_init_buffer_space(sk);
5837 tcp_fast_path_on(tp);
5838 } else {
5839 return 1;
5840 }
5841 break;
5842
5843 case TCP_FIN_WAIT1:
5844 if (tp->snd_una == tp->write_seq) {
5845 tcp_set_state(sk, TCP_FIN_WAIT2);
5846 sk->sk_shutdown |= SEND_SHUTDOWN;
5847 dst_confirm(__sk_dst_get(sk));
5848
5849 if (!sock_flag(sk, SOCK_DEAD))
5850 /* Wake up lingering close() */
5851 sk->sk_state_change(sk);
5852 else {
5853 int tmo;
5854
5855 if (tp->linger2 < 0 ||
5856 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5857 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
5858 tcp_done(sk);
5859 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
5860 return 1;
5861 }
5862
5863 tmo = tcp_fin_time(sk);
5864 if (tmo > TCP_TIMEWAIT_LEN) {
5865 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
5866 } else if (th->fin || sock_owned_by_user(sk)) {
5867 /* Bad case. We could lose such FIN otherwise.
5868 * It is not a big problem, but it looks confusing
5869 * and not so rare event. We still can lose it now,
5870 * if it spins in bh_lock_sock(), but it is really
5871 * marginal case.
5872 */
5873 inet_csk_reset_keepalive_timer(sk, tmo);
5874 } else {
5875 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
5876 goto discard;
5877 }
5878 }
5879 }
5880 break;
5881
5882 case TCP_CLOSING:
5883 if (tp->snd_una == tp->write_seq) {
5884 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
5885 goto discard;
5886 }
5887 break;
5888
5889 case TCP_LAST_ACK:
5890 if (tp->snd_una == tp->write_seq) {
5891 tcp_update_metrics(sk);
5892 tcp_done(sk);
5893 goto discard;
5894 }
5895 break;
5896 }
5897 } else
5898 goto discard;
5899
5900 /* step 6: check the URG bit */
5901 tcp_urg(sk, skb, th);
5902
5903 /* step 7: process the segment text */
5904 switch (sk->sk_state) {
5905 case TCP_CLOSE_WAIT:
5906 case TCP_CLOSING:
5907 case TCP_LAST_ACK:
5908 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
5909 break;
5910 case TCP_FIN_WAIT1:
5911 case TCP_FIN_WAIT2:
5912 /* RFC 793 says to queue data in these states,
5913 * RFC 1122 says we MUST send a reset.
5914 * BSD 4.4 also does reset.
5915 */
5916 if (sk->sk_shutdown & RCV_SHUTDOWN) {
5917 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
5918 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
5919 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
5920 tcp_reset(sk);
5921 return 1;
5922 }
5923 }
5924 /* Fall through */
5925 case TCP_ESTABLISHED:
5926 tcp_data_queue(sk, skb);
5927 queued = 1;
5928 break;
5929 }
5930
5931 /* tcp_data could move socket to TIME-WAIT */
5932 if (sk->sk_state != TCP_CLOSE) {
5933 tcp_data_snd_check(sk);
5934 tcp_ack_snd_check(sk);
5935 }
5936
5937 if (!queued) {
5938discard:
5939 __kfree_skb(skb);
5940 }
5941 return 0;
5942}
5943EXPORT_SYMBOL(tcp_rcv_state_process);