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1// SPDX-License-Identifier: GPL-2.0-only
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: Pedro Roque : Retransmit queue handled by TCP.
24 * : Fragmentation on mtu decrease
25 * : Segment collapse on retransmit
26 * : AF independence
27 *
28 * Linus Torvalds : send_delayed_ack
29 * David S. Miller : Charge memory using the right skb
30 * during syn/ack processing.
31 * David S. Miller : Output engine completely rewritten.
32 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
33 * Cacophonix Gaul : draft-minshall-nagle-01
34 * J Hadi Salim : ECN support
35 *
36 */
37
38#define pr_fmt(fmt) "TCP: " fmt
39
40#include <net/tcp.h>
41#include <net/mptcp.h>
42
43#include <linux/compiler.h>
44#include <linux/gfp.h>
45#include <linux/module.h>
46#include <linux/static_key.h>
47
48#include <trace/events/tcp.h>
49
50/* Refresh clocks of a TCP socket,
51 * ensuring monotically increasing values.
52 */
53void tcp_mstamp_refresh(struct tcp_sock *tp)
54{
55 u64 val = tcp_clock_ns();
56
57 tp->tcp_clock_cache = val;
58 tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
59}
60
61static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
62 int push_one, gfp_t gfp);
63
64/* Account for new data that has been sent to the network. */
65static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
66{
67 struct inet_connection_sock *icsk = inet_csk(sk);
68 struct tcp_sock *tp = tcp_sk(sk);
69 unsigned int prior_packets = tp->packets_out;
70
71 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
72
73 __skb_unlink(skb, &sk->sk_write_queue);
74 tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
75
76 if (tp->highest_sack == NULL)
77 tp->highest_sack = skb;
78
79 tp->packets_out += tcp_skb_pcount(skb);
80 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
81 tcp_rearm_rto(sk);
82
83 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
84 tcp_skb_pcount(skb));
85}
86
87/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
88 * window scaling factor due to loss of precision.
89 * If window has been shrunk, what should we make? It is not clear at all.
90 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
91 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
92 * invalid. OK, let's make this for now:
93 */
94static inline __u32 tcp_acceptable_seq(const struct sock *sk)
95{
96 const struct tcp_sock *tp = tcp_sk(sk);
97
98 if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
99 (tp->rx_opt.wscale_ok &&
100 ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
101 return tp->snd_nxt;
102 else
103 return tcp_wnd_end(tp);
104}
105
106/* Calculate mss to advertise in SYN segment.
107 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
108 *
109 * 1. It is independent of path mtu.
110 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
111 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
112 * attached devices, because some buggy hosts are confused by
113 * large MSS.
114 * 4. We do not make 3, we advertise MSS, calculated from first
115 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
116 * This may be overridden via information stored in routing table.
117 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
118 * probably even Jumbo".
119 */
120static __u16 tcp_advertise_mss(struct sock *sk)
121{
122 struct tcp_sock *tp = tcp_sk(sk);
123 const struct dst_entry *dst = __sk_dst_get(sk);
124 int mss = tp->advmss;
125
126 if (dst) {
127 unsigned int metric = dst_metric_advmss(dst);
128
129 if (metric < mss) {
130 mss = metric;
131 tp->advmss = mss;
132 }
133 }
134
135 return (__u16)mss;
136}
137
138/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
139 * This is the first part of cwnd validation mechanism.
140 */
141void tcp_cwnd_restart(struct sock *sk, s32 delta)
142{
143 struct tcp_sock *tp = tcp_sk(sk);
144 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
145 u32 cwnd = tp->snd_cwnd;
146
147 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
148
149 tp->snd_ssthresh = tcp_current_ssthresh(sk);
150 restart_cwnd = min(restart_cwnd, cwnd);
151
152 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
153 cwnd >>= 1;
154 tp->snd_cwnd = max(cwnd, restart_cwnd);
155 tp->snd_cwnd_stamp = tcp_jiffies32;
156 tp->snd_cwnd_used = 0;
157}
158
159/* Congestion state accounting after a packet has been sent. */
160static void tcp_event_data_sent(struct tcp_sock *tp,
161 struct sock *sk)
162{
163 struct inet_connection_sock *icsk = inet_csk(sk);
164 const u32 now = tcp_jiffies32;
165
166 if (tcp_packets_in_flight(tp) == 0)
167 tcp_ca_event(sk, CA_EVENT_TX_START);
168
169 /* If this is the first data packet sent in response to the
170 * previous received data,
171 * and it is a reply for ato after last received packet,
172 * increase pingpong count.
173 */
174 if (before(tp->lsndtime, icsk->icsk_ack.lrcvtime) &&
175 (u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
176 inet_csk_inc_pingpong_cnt(sk);
177
178 tp->lsndtime = now;
179}
180
181/* Account for an ACK we sent. */
182static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts,
183 u32 rcv_nxt)
184{
185 struct tcp_sock *tp = tcp_sk(sk);
186
187 if (unlikely(tp->compressed_ack)) {
188 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
189 tp->compressed_ack);
190 tp->compressed_ack = 0;
191 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
192 __sock_put(sk);
193 }
194
195 if (unlikely(rcv_nxt != tp->rcv_nxt))
196 return; /* Special ACK sent by DCTCP to reflect ECN */
197 tcp_dec_quickack_mode(sk, pkts);
198 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
199}
200
201/* Determine a window scaling and initial window to offer.
202 * Based on the assumption that the given amount of space
203 * will be offered. Store the results in the tp structure.
204 * NOTE: for smooth operation initial space offering should
205 * be a multiple of mss if possible. We assume here that mss >= 1.
206 * This MUST be enforced by all callers.
207 */
208void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
209 __u32 *rcv_wnd, __u32 *window_clamp,
210 int wscale_ok, __u8 *rcv_wscale,
211 __u32 init_rcv_wnd)
212{
213 unsigned int space = (__space < 0 ? 0 : __space);
214
215 /* If no clamp set the clamp to the max possible scaled window */
216 if (*window_clamp == 0)
217 (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
218 space = min(*window_clamp, space);
219
220 /* Quantize space offering to a multiple of mss if possible. */
221 if (space > mss)
222 space = rounddown(space, mss);
223
224 /* NOTE: offering an initial window larger than 32767
225 * will break some buggy TCP stacks. If the admin tells us
226 * it is likely we could be speaking with such a buggy stack
227 * we will truncate our initial window offering to 32K-1
228 * unless the remote has sent us a window scaling option,
229 * which we interpret as a sign the remote TCP is not
230 * misinterpreting the window field as a signed quantity.
231 */
232 if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
233 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
234 else
235 (*rcv_wnd) = min_t(u32, space, U16_MAX);
236
237 if (init_rcv_wnd)
238 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
239
240 *rcv_wscale = 0;
241 if (wscale_ok) {
242 /* Set window scaling on max possible window */
243 space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
244 space = max_t(u32, space, sysctl_rmem_max);
245 space = min_t(u32, space, *window_clamp);
246 *rcv_wscale = clamp_t(int, ilog2(space) - 15,
247 0, TCP_MAX_WSCALE);
248 }
249 /* Set the clamp no higher than max representable value */
250 (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
251}
252EXPORT_SYMBOL(tcp_select_initial_window);
253
254/* Chose a new window to advertise, update state in tcp_sock for the
255 * socket, and return result with RFC1323 scaling applied. The return
256 * value can be stuffed directly into th->window for an outgoing
257 * frame.
258 */
259static u16 tcp_select_window(struct sock *sk)
260{
261 struct tcp_sock *tp = tcp_sk(sk);
262 u32 old_win = tp->rcv_wnd;
263 u32 cur_win = tcp_receive_window(tp);
264 u32 new_win = __tcp_select_window(sk);
265
266 /* Never shrink the offered window */
267 if (new_win < cur_win) {
268 /* Danger Will Robinson!
269 * Don't update rcv_wup/rcv_wnd here or else
270 * we will not be able to advertise a zero
271 * window in time. --DaveM
272 *
273 * Relax Will Robinson.
274 */
275 if (new_win == 0)
276 NET_INC_STATS(sock_net(sk),
277 LINUX_MIB_TCPWANTZEROWINDOWADV);
278 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
279 }
280 tp->rcv_wnd = new_win;
281 tp->rcv_wup = tp->rcv_nxt;
282
283 /* Make sure we do not exceed the maximum possible
284 * scaled window.
285 */
286 if (!tp->rx_opt.rcv_wscale &&
287 sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
288 new_win = min(new_win, MAX_TCP_WINDOW);
289 else
290 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
291
292 /* RFC1323 scaling applied */
293 new_win >>= tp->rx_opt.rcv_wscale;
294
295 /* If we advertise zero window, disable fast path. */
296 if (new_win == 0) {
297 tp->pred_flags = 0;
298 if (old_win)
299 NET_INC_STATS(sock_net(sk),
300 LINUX_MIB_TCPTOZEROWINDOWADV);
301 } else if (old_win == 0) {
302 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
303 }
304
305 return new_win;
306}
307
308/* Packet ECN state for a SYN-ACK */
309static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
310{
311 const struct tcp_sock *tp = tcp_sk(sk);
312
313 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
314 if (!(tp->ecn_flags & TCP_ECN_OK))
315 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
316 else if (tcp_ca_needs_ecn(sk) ||
317 tcp_bpf_ca_needs_ecn(sk))
318 INET_ECN_xmit(sk);
319}
320
321/* Packet ECN state for a SYN. */
322static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
323{
324 struct tcp_sock *tp = tcp_sk(sk);
325 bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
326 bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
327 tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
328
329 if (!use_ecn) {
330 const struct dst_entry *dst = __sk_dst_get(sk);
331
332 if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
333 use_ecn = true;
334 }
335
336 tp->ecn_flags = 0;
337
338 if (use_ecn) {
339 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
340 tp->ecn_flags = TCP_ECN_OK;
341 if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
342 INET_ECN_xmit(sk);
343 }
344}
345
346static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
347{
348 if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
349 /* tp->ecn_flags are cleared at a later point in time when
350 * SYN ACK is ultimatively being received.
351 */
352 TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
353}
354
355static void
356tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
357{
358 if (inet_rsk(req)->ecn_ok)
359 th->ece = 1;
360}
361
362/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
363 * be sent.
364 */
365static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
366 struct tcphdr *th, int tcp_header_len)
367{
368 struct tcp_sock *tp = tcp_sk(sk);
369
370 if (tp->ecn_flags & TCP_ECN_OK) {
371 /* Not-retransmitted data segment: set ECT and inject CWR. */
372 if (skb->len != tcp_header_len &&
373 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
374 INET_ECN_xmit(sk);
375 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
376 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
377 th->cwr = 1;
378 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
379 }
380 } else if (!tcp_ca_needs_ecn(sk)) {
381 /* ACK or retransmitted segment: clear ECT|CE */
382 INET_ECN_dontxmit(sk);
383 }
384 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
385 th->ece = 1;
386 }
387}
388
389/* Constructs common control bits of non-data skb. If SYN/FIN is present,
390 * auto increment end seqno.
391 */
392static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
393{
394 skb->ip_summed = CHECKSUM_PARTIAL;
395
396 TCP_SKB_CB(skb)->tcp_flags = flags;
397 TCP_SKB_CB(skb)->sacked = 0;
398
399 tcp_skb_pcount_set(skb, 1);
400
401 TCP_SKB_CB(skb)->seq = seq;
402 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
403 seq++;
404 TCP_SKB_CB(skb)->end_seq = seq;
405}
406
407static inline bool tcp_urg_mode(const struct tcp_sock *tp)
408{
409 return tp->snd_una != tp->snd_up;
410}
411
412#define OPTION_SACK_ADVERTISE (1 << 0)
413#define OPTION_TS (1 << 1)
414#define OPTION_MD5 (1 << 2)
415#define OPTION_WSCALE (1 << 3)
416#define OPTION_FAST_OPEN_COOKIE (1 << 8)
417#define OPTION_SMC (1 << 9)
418#define OPTION_MPTCP (1 << 10)
419
420static void smc_options_write(__be32 *ptr, u16 *options)
421{
422#if IS_ENABLED(CONFIG_SMC)
423 if (static_branch_unlikely(&tcp_have_smc)) {
424 if (unlikely(OPTION_SMC & *options)) {
425 *ptr++ = htonl((TCPOPT_NOP << 24) |
426 (TCPOPT_NOP << 16) |
427 (TCPOPT_EXP << 8) |
428 (TCPOLEN_EXP_SMC_BASE));
429 *ptr++ = htonl(TCPOPT_SMC_MAGIC);
430 }
431 }
432#endif
433}
434
435struct tcp_out_options {
436 u16 options; /* bit field of OPTION_* */
437 u16 mss; /* 0 to disable */
438 u8 ws; /* window scale, 0 to disable */
439 u8 num_sack_blocks; /* number of SACK blocks to include */
440 u8 hash_size; /* bytes in hash_location */
441 __u8 *hash_location; /* temporary pointer, overloaded */
442 __u32 tsval, tsecr; /* need to include OPTION_TS */
443 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
444 struct mptcp_out_options mptcp;
445};
446
447static void mptcp_options_write(__be32 *ptr, struct tcp_out_options *opts)
448{
449#if IS_ENABLED(CONFIG_MPTCP)
450 if (unlikely(OPTION_MPTCP & opts->options))
451 mptcp_write_options(ptr, &opts->mptcp);
452#endif
453}
454
455/* Write previously computed TCP options to the packet.
456 *
457 * Beware: Something in the Internet is very sensitive to the ordering of
458 * TCP options, we learned this through the hard way, so be careful here.
459 * Luckily we can at least blame others for their non-compliance but from
460 * inter-operability perspective it seems that we're somewhat stuck with
461 * the ordering which we have been using if we want to keep working with
462 * those broken things (not that it currently hurts anybody as there isn't
463 * particular reason why the ordering would need to be changed).
464 *
465 * At least SACK_PERM as the first option is known to lead to a disaster
466 * (but it may well be that other scenarios fail similarly).
467 */
468static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
469 struct tcp_out_options *opts)
470{
471 u16 options = opts->options; /* mungable copy */
472
473 if (unlikely(OPTION_MD5 & options)) {
474 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
475 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
476 /* overload cookie hash location */
477 opts->hash_location = (__u8 *)ptr;
478 ptr += 4;
479 }
480
481 if (unlikely(opts->mss)) {
482 *ptr++ = htonl((TCPOPT_MSS << 24) |
483 (TCPOLEN_MSS << 16) |
484 opts->mss);
485 }
486
487 if (likely(OPTION_TS & options)) {
488 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
489 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
490 (TCPOLEN_SACK_PERM << 16) |
491 (TCPOPT_TIMESTAMP << 8) |
492 TCPOLEN_TIMESTAMP);
493 options &= ~OPTION_SACK_ADVERTISE;
494 } else {
495 *ptr++ = htonl((TCPOPT_NOP << 24) |
496 (TCPOPT_NOP << 16) |
497 (TCPOPT_TIMESTAMP << 8) |
498 TCPOLEN_TIMESTAMP);
499 }
500 *ptr++ = htonl(opts->tsval);
501 *ptr++ = htonl(opts->tsecr);
502 }
503
504 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
505 *ptr++ = htonl((TCPOPT_NOP << 24) |
506 (TCPOPT_NOP << 16) |
507 (TCPOPT_SACK_PERM << 8) |
508 TCPOLEN_SACK_PERM);
509 }
510
511 if (unlikely(OPTION_WSCALE & options)) {
512 *ptr++ = htonl((TCPOPT_NOP << 24) |
513 (TCPOPT_WINDOW << 16) |
514 (TCPOLEN_WINDOW << 8) |
515 opts->ws);
516 }
517
518 if (unlikely(opts->num_sack_blocks)) {
519 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
520 tp->duplicate_sack : tp->selective_acks;
521 int this_sack;
522
523 *ptr++ = htonl((TCPOPT_NOP << 24) |
524 (TCPOPT_NOP << 16) |
525 (TCPOPT_SACK << 8) |
526 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
527 TCPOLEN_SACK_PERBLOCK)));
528
529 for (this_sack = 0; this_sack < opts->num_sack_blocks;
530 ++this_sack) {
531 *ptr++ = htonl(sp[this_sack].start_seq);
532 *ptr++ = htonl(sp[this_sack].end_seq);
533 }
534
535 tp->rx_opt.dsack = 0;
536 }
537
538 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
539 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
540 u8 *p = (u8 *)ptr;
541 u32 len; /* Fast Open option length */
542
543 if (foc->exp) {
544 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
545 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
546 TCPOPT_FASTOPEN_MAGIC);
547 p += TCPOLEN_EXP_FASTOPEN_BASE;
548 } else {
549 len = TCPOLEN_FASTOPEN_BASE + foc->len;
550 *p++ = TCPOPT_FASTOPEN;
551 *p++ = len;
552 }
553
554 memcpy(p, foc->val, foc->len);
555 if ((len & 3) == 2) {
556 p[foc->len] = TCPOPT_NOP;
557 p[foc->len + 1] = TCPOPT_NOP;
558 }
559 ptr += (len + 3) >> 2;
560 }
561
562 smc_options_write(ptr, &options);
563
564 mptcp_options_write(ptr, opts);
565}
566
567static void smc_set_option(const struct tcp_sock *tp,
568 struct tcp_out_options *opts,
569 unsigned int *remaining)
570{
571#if IS_ENABLED(CONFIG_SMC)
572 if (static_branch_unlikely(&tcp_have_smc)) {
573 if (tp->syn_smc) {
574 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
575 opts->options |= OPTION_SMC;
576 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
577 }
578 }
579 }
580#endif
581}
582
583static void smc_set_option_cond(const struct tcp_sock *tp,
584 const struct inet_request_sock *ireq,
585 struct tcp_out_options *opts,
586 unsigned int *remaining)
587{
588#if IS_ENABLED(CONFIG_SMC)
589 if (static_branch_unlikely(&tcp_have_smc)) {
590 if (tp->syn_smc && ireq->smc_ok) {
591 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
592 opts->options |= OPTION_SMC;
593 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
594 }
595 }
596 }
597#endif
598}
599
600static void mptcp_set_option_cond(const struct request_sock *req,
601 struct tcp_out_options *opts,
602 unsigned int *remaining)
603{
604 if (rsk_is_mptcp(req)) {
605 unsigned int size;
606
607 if (mptcp_synack_options(req, &size, &opts->mptcp)) {
608 if (*remaining >= size) {
609 opts->options |= OPTION_MPTCP;
610 *remaining -= size;
611 }
612 }
613 }
614}
615
616/* Compute TCP options for SYN packets. This is not the final
617 * network wire format yet.
618 */
619static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
620 struct tcp_out_options *opts,
621 struct tcp_md5sig_key **md5)
622{
623 struct tcp_sock *tp = tcp_sk(sk);
624 unsigned int remaining = MAX_TCP_OPTION_SPACE;
625 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
626
627 *md5 = NULL;
628#ifdef CONFIG_TCP_MD5SIG
629 if (static_branch_unlikely(&tcp_md5_needed) &&
630 rcu_access_pointer(tp->md5sig_info)) {
631 *md5 = tp->af_specific->md5_lookup(sk, sk);
632 if (*md5) {
633 opts->options |= OPTION_MD5;
634 remaining -= TCPOLEN_MD5SIG_ALIGNED;
635 }
636 }
637#endif
638
639 /* We always get an MSS option. The option bytes which will be seen in
640 * normal data packets should timestamps be used, must be in the MSS
641 * advertised. But we subtract them from tp->mss_cache so that
642 * calculations in tcp_sendmsg are simpler etc. So account for this
643 * fact here if necessary. If we don't do this correctly, as a
644 * receiver we won't recognize data packets as being full sized when we
645 * should, and thus we won't abide by the delayed ACK rules correctly.
646 * SACKs don't matter, we never delay an ACK when we have any of those
647 * going out. */
648 opts->mss = tcp_advertise_mss(sk);
649 remaining -= TCPOLEN_MSS_ALIGNED;
650
651 if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) {
652 opts->options |= OPTION_TS;
653 opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
654 opts->tsecr = tp->rx_opt.ts_recent;
655 remaining -= TCPOLEN_TSTAMP_ALIGNED;
656 }
657 if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) {
658 opts->ws = tp->rx_opt.rcv_wscale;
659 opts->options |= OPTION_WSCALE;
660 remaining -= TCPOLEN_WSCALE_ALIGNED;
661 }
662 if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) {
663 opts->options |= OPTION_SACK_ADVERTISE;
664 if (unlikely(!(OPTION_TS & opts->options)))
665 remaining -= TCPOLEN_SACKPERM_ALIGNED;
666 }
667
668 if (fastopen && fastopen->cookie.len >= 0) {
669 u32 need = fastopen->cookie.len;
670
671 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
672 TCPOLEN_FASTOPEN_BASE;
673 need = (need + 3) & ~3U; /* Align to 32 bits */
674 if (remaining >= need) {
675 opts->options |= OPTION_FAST_OPEN_COOKIE;
676 opts->fastopen_cookie = &fastopen->cookie;
677 remaining -= need;
678 tp->syn_fastopen = 1;
679 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
680 }
681 }
682
683 smc_set_option(tp, opts, &remaining);
684
685 if (sk_is_mptcp(sk)) {
686 unsigned int size;
687
688 if (mptcp_syn_options(sk, skb, &size, &opts->mptcp)) {
689 opts->options |= OPTION_MPTCP;
690 remaining -= size;
691 }
692 }
693
694 return MAX_TCP_OPTION_SPACE - remaining;
695}
696
697/* Set up TCP options for SYN-ACKs. */
698static unsigned int tcp_synack_options(const struct sock *sk,
699 struct request_sock *req,
700 unsigned int mss, struct sk_buff *skb,
701 struct tcp_out_options *opts,
702 const struct tcp_md5sig_key *md5,
703 struct tcp_fastopen_cookie *foc,
704 enum tcp_synack_type synack_type)
705{
706 struct inet_request_sock *ireq = inet_rsk(req);
707 unsigned int remaining = MAX_TCP_OPTION_SPACE;
708
709#ifdef CONFIG_TCP_MD5SIG
710 if (md5) {
711 opts->options |= OPTION_MD5;
712 remaining -= TCPOLEN_MD5SIG_ALIGNED;
713
714 /* We can't fit any SACK blocks in a packet with MD5 + TS
715 * options. There was discussion about disabling SACK
716 * rather than TS in order to fit in better with old,
717 * buggy kernels, but that was deemed to be unnecessary.
718 */
719 if (synack_type != TCP_SYNACK_COOKIE)
720 ireq->tstamp_ok &= !ireq->sack_ok;
721 }
722#endif
723
724 /* We always send an MSS option. */
725 opts->mss = mss;
726 remaining -= TCPOLEN_MSS_ALIGNED;
727
728 if (likely(ireq->wscale_ok)) {
729 opts->ws = ireq->rcv_wscale;
730 opts->options |= OPTION_WSCALE;
731 remaining -= TCPOLEN_WSCALE_ALIGNED;
732 }
733 if (likely(ireq->tstamp_ok)) {
734 opts->options |= OPTION_TS;
735 opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
736 opts->tsecr = req->ts_recent;
737 remaining -= TCPOLEN_TSTAMP_ALIGNED;
738 }
739 if (likely(ireq->sack_ok)) {
740 opts->options |= OPTION_SACK_ADVERTISE;
741 if (unlikely(!ireq->tstamp_ok))
742 remaining -= TCPOLEN_SACKPERM_ALIGNED;
743 }
744 if (foc != NULL && foc->len >= 0) {
745 u32 need = foc->len;
746
747 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
748 TCPOLEN_FASTOPEN_BASE;
749 need = (need + 3) & ~3U; /* Align to 32 bits */
750 if (remaining >= need) {
751 opts->options |= OPTION_FAST_OPEN_COOKIE;
752 opts->fastopen_cookie = foc;
753 remaining -= need;
754 }
755 }
756
757 mptcp_set_option_cond(req, opts, &remaining);
758
759 smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
760
761 return MAX_TCP_OPTION_SPACE - remaining;
762}
763
764/* Compute TCP options for ESTABLISHED sockets. This is not the
765 * final wire format yet.
766 */
767static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
768 struct tcp_out_options *opts,
769 struct tcp_md5sig_key **md5)
770{
771 struct tcp_sock *tp = tcp_sk(sk);
772 unsigned int size = 0;
773 unsigned int eff_sacks;
774
775 opts->options = 0;
776
777 *md5 = NULL;
778#ifdef CONFIG_TCP_MD5SIG
779 if (static_branch_unlikely(&tcp_md5_needed) &&
780 rcu_access_pointer(tp->md5sig_info)) {
781 *md5 = tp->af_specific->md5_lookup(sk, sk);
782 if (*md5) {
783 opts->options |= OPTION_MD5;
784 size += TCPOLEN_MD5SIG_ALIGNED;
785 }
786 }
787#endif
788
789 if (likely(tp->rx_opt.tstamp_ok)) {
790 opts->options |= OPTION_TS;
791 opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
792 opts->tsecr = tp->rx_opt.ts_recent;
793 size += TCPOLEN_TSTAMP_ALIGNED;
794 }
795
796 /* MPTCP options have precedence over SACK for the limited TCP
797 * option space because a MPTCP connection would be forced to
798 * fall back to regular TCP if a required multipath option is
799 * missing. SACK still gets a chance to use whatever space is
800 * left.
801 */
802 if (sk_is_mptcp(sk)) {
803 unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
804 unsigned int opt_size = 0;
805
806 if (mptcp_established_options(sk, skb, &opt_size, remaining,
807 &opts->mptcp)) {
808 opts->options |= OPTION_MPTCP;
809 size += opt_size;
810 }
811 }
812
813 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
814 if (unlikely(eff_sacks)) {
815 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
816 if (unlikely(remaining < TCPOLEN_SACK_BASE_ALIGNED +
817 TCPOLEN_SACK_PERBLOCK))
818 return size;
819
820 opts->num_sack_blocks =
821 min_t(unsigned int, eff_sacks,
822 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
823 TCPOLEN_SACK_PERBLOCK);
824
825 size += TCPOLEN_SACK_BASE_ALIGNED +
826 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
827 }
828
829 return size;
830}
831
832
833/* TCP SMALL QUEUES (TSQ)
834 *
835 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
836 * to reduce RTT and bufferbloat.
837 * We do this using a special skb destructor (tcp_wfree).
838 *
839 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
840 * needs to be reallocated in a driver.
841 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
842 *
843 * Since transmit from skb destructor is forbidden, we use a tasklet
844 * to process all sockets that eventually need to send more skbs.
845 * We use one tasklet per cpu, with its own queue of sockets.
846 */
847struct tsq_tasklet {
848 struct tasklet_struct tasklet;
849 struct list_head head; /* queue of tcp sockets */
850};
851static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
852
853static void tcp_tsq_write(struct sock *sk)
854{
855 if ((1 << sk->sk_state) &
856 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
857 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
858 struct tcp_sock *tp = tcp_sk(sk);
859
860 if (tp->lost_out > tp->retrans_out &&
861 tp->snd_cwnd > tcp_packets_in_flight(tp)) {
862 tcp_mstamp_refresh(tp);
863 tcp_xmit_retransmit_queue(sk);
864 }
865
866 tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
867 0, GFP_ATOMIC);
868 }
869}
870
871static void tcp_tsq_handler(struct sock *sk)
872{
873 bh_lock_sock(sk);
874 if (!sock_owned_by_user(sk))
875 tcp_tsq_write(sk);
876 else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
877 sock_hold(sk);
878 bh_unlock_sock(sk);
879}
880/*
881 * One tasklet per cpu tries to send more skbs.
882 * We run in tasklet context but need to disable irqs when
883 * transferring tsq->head because tcp_wfree() might
884 * interrupt us (non NAPI drivers)
885 */
886static void tcp_tasklet_func(unsigned long data)
887{
888 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
889 LIST_HEAD(list);
890 unsigned long flags;
891 struct list_head *q, *n;
892 struct tcp_sock *tp;
893 struct sock *sk;
894
895 local_irq_save(flags);
896 list_splice_init(&tsq->head, &list);
897 local_irq_restore(flags);
898
899 list_for_each_safe(q, n, &list) {
900 tp = list_entry(q, struct tcp_sock, tsq_node);
901 list_del(&tp->tsq_node);
902
903 sk = (struct sock *)tp;
904 smp_mb__before_atomic();
905 clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
906
907 tcp_tsq_handler(sk);
908 sk_free(sk);
909 }
910}
911
912#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
913 TCPF_WRITE_TIMER_DEFERRED | \
914 TCPF_DELACK_TIMER_DEFERRED | \
915 TCPF_MTU_REDUCED_DEFERRED)
916/**
917 * tcp_release_cb - tcp release_sock() callback
918 * @sk: socket
919 *
920 * called from release_sock() to perform protocol dependent
921 * actions before socket release.
922 */
923void tcp_release_cb(struct sock *sk)
924{
925 unsigned long flags, nflags;
926
927 /* perform an atomic operation only if at least one flag is set */
928 do {
929 flags = sk->sk_tsq_flags;
930 if (!(flags & TCP_DEFERRED_ALL))
931 return;
932 nflags = flags & ~TCP_DEFERRED_ALL;
933 } while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
934
935 if (flags & TCPF_TSQ_DEFERRED) {
936 tcp_tsq_write(sk);
937 __sock_put(sk);
938 }
939 /* Here begins the tricky part :
940 * We are called from release_sock() with :
941 * 1) BH disabled
942 * 2) sk_lock.slock spinlock held
943 * 3) socket owned by us (sk->sk_lock.owned == 1)
944 *
945 * But following code is meant to be called from BH handlers,
946 * so we should keep BH disabled, but early release socket ownership
947 */
948 sock_release_ownership(sk);
949
950 if (flags & TCPF_WRITE_TIMER_DEFERRED) {
951 tcp_write_timer_handler(sk);
952 __sock_put(sk);
953 }
954 if (flags & TCPF_DELACK_TIMER_DEFERRED) {
955 tcp_delack_timer_handler(sk);
956 __sock_put(sk);
957 }
958 if (flags & TCPF_MTU_REDUCED_DEFERRED) {
959 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
960 __sock_put(sk);
961 }
962}
963EXPORT_SYMBOL(tcp_release_cb);
964
965void __init tcp_tasklet_init(void)
966{
967 int i;
968
969 for_each_possible_cpu(i) {
970 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
971
972 INIT_LIST_HEAD(&tsq->head);
973 tasklet_init(&tsq->tasklet,
974 tcp_tasklet_func,
975 (unsigned long)tsq);
976 }
977}
978
979/*
980 * Write buffer destructor automatically called from kfree_skb.
981 * We can't xmit new skbs from this context, as we might already
982 * hold qdisc lock.
983 */
984void tcp_wfree(struct sk_buff *skb)
985{
986 struct sock *sk = skb->sk;
987 struct tcp_sock *tp = tcp_sk(sk);
988 unsigned long flags, nval, oval;
989
990 /* Keep one reference on sk_wmem_alloc.
991 * Will be released by sk_free() from here or tcp_tasklet_func()
992 */
993 WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
994
995 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
996 * Wait until our queues (qdisc + devices) are drained.
997 * This gives :
998 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
999 * - chance for incoming ACK (processed by another cpu maybe)
1000 * to migrate this flow (skb->ooo_okay will be eventually set)
1001 */
1002 if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
1003 goto out;
1004
1005 for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
1006 struct tsq_tasklet *tsq;
1007 bool empty;
1008
1009 if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
1010 goto out;
1011
1012 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
1013 nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
1014 if (nval != oval)
1015 continue;
1016
1017 /* queue this socket to tasklet queue */
1018 local_irq_save(flags);
1019 tsq = this_cpu_ptr(&tsq_tasklet);
1020 empty = list_empty(&tsq->head);
1021 list_add(&tp->tsq_node, &tsq->head);
1022 if (empty)
1023 tasklet_schedule(&tsq->tasklet);
1024 local_irq_restore(flags);
1025 return;
1026 }
1027out:
1028 sk_free(sk);
1029}
1030
1031/* Note: Called under soft irq.
1032 * We can call TCP stack right away, unless socket is owned by user.
1033 */
1034enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
1035{
1036 struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
1037 struct sock *sk = (struct sock *)tp;
1038
1039 tcp_tsq_handler(sk);
1040 sock_put(sk);
1041
1042 return HRTIMER_NORESTART;
1043}
1044
1045static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb,
1046 u64 prior_wstamp)
1047{
1048 struct tcp_sock *tp = tcp_sk(sk);
1049
1050 if (sk->sk_pacing_status != SK_PACING_NONE) {
1051 unsigned long rate = sk->sk_pacing_rate;
1052
1053 /* Original sch_fq does not pace first 10 MSS
1054 * Note that tp->data_segs_out overflows after 2^32 packets,
1055 * this is a minor annoyance.
1056 */
1057 if (rate != ~0UL && rate && tp->data_segs_out >= 10) {
1058 u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate);
1059 u64 credit = tp->tcp_wstamp_ns - prior_wstamp;
1060
1061 /* take into account OS jitter */
1062 len_ns -= min_t(u64, len_ns / 2, credit);
1063 tp->tcp_wstamp_ns += len_ns;
1064 }
1065 }
1066 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
1067}
1068
1069INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1070INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1071INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb));
1072
1073/* This routine actually transmits TCP packets queued in by
1074 * tcp_do_sendmsg(). This is used by both the initial
1075 * transmission and possible later retransmissions.
1076 * All SKB's seen here are completely headerless. It is our
1077 * job to build the TCP header, and pass the packet down to
1078 * IP so it can do the same plus pass the packet off to the
1079 * device.
1080 *
1081 * We are working here with either a clone of the original
1082 * SKB, or a fresh unique copy made by the retransmit engine.
1083 */
1084static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
1085 int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
1086{
1087 const struct inet_connection_sock *icsk = inet_csk(sk);
1088 struct inet_sock *inet;
1089 struct tcp_sock *tp;
1090 struct tcp_skb_cb *tcb;
1091 struct tcp_out_options opts;
1092 unsigned int tcp_options_size, tcp_header_size;
1093 struct sk_buff *oskb = NULL;
1094 struct tcp_md5sig_key *md5;
1095 struct tcphdr *th;
1096 u64 prior_wstamp;
1097 int err;
1098
1099 BUG_ON(!skb || !tcp_skb_pcount(skb));
1100 tp = tcp_sk(sk);
1101 prior_wstamp = tp->tcp_wstamp_ns;
1102 tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
1103 skb->skb_mstamp_ns = tp->tcp_wstamp_ns;
1104 if (clone_it) {
1105 TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
1106 - tp->snd_una;
1107 oskb = skb;
1108
1109 tcp_skb_tsorted_save(oskb) {
1110 if (unlikely(skb_cloned(oskb)))
1111 skb = pskb_copy(oskb, gfp_mask);
1112 else
1113 skb = skb_clone(oskb, gfp_mask);
1114 } tcp_skb_tsorted_restore(oskb);
1115
1116 if (unlikely(!skb))
1117 return -ENOBUFS;
1118 /* retransmit skbs might have a non zero value in skb->dev
1119 * because skb->dev is aliased with skb->rbnode.rb_left
1120 */
1121 skb->dev = NULL;
1122 }
1123
1124 inet = inet_sk(sk);
1125 tcb = TCP_SKB_CB(skb);
1126 memset(&opts, 0, sizeof(opts));
1127
1128 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
1129 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
1130 } else {
1131 tcp_options_size = tcp_established_options(sk, skb, &opts,
1132 &md5);
1133 /* Force a PSH flag on all (GSO) packets to expedite GRO flush
1134 * at receiver : This slightly improve GRO performance.
1135 * Note that we do not force the PSH flag for non GSO packets,
1136 * because they might be sent under high congestion events,
1137 * and in this case it is better to delay the delivery of 1-MSS
1138 * packets and thus the corresponding ACK packet that would
1139 * release the following packet.
1140 */
1141 if (tcp_skb_pcount(skb) > 1)
1142 tcb->tcp_flags |= TCPHDR_PSH;
1143 }
1144 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1145
1146 /* if no packet is in qdisc/device queue, then allow XPS to select
1147 * another queue. We can be called from tcp_tsq_handler()
1148 * which holds one reference to sk.
1149 *
1150 * TODO: Ideally, in-flight pure ACK packets should not matter here.
1151 * One way to get this would be to set skb->truesize = 2 on them.
1152 */
1153 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1154
1155 /* If we had to use memory reserve to allocate this skb,
1156 * this might cause drops if packet is looped back :
1157 * Other socket might not have SOCK_MEMALLOC.
1158 * Packets not looped back do not care about pfmemalloc.
1159 */
1160 skb->pfmemalloc = 0;
1161
1162 skb_push(skb, tcp_header_size);
1163 skb_reset_transport_header(skb);
1164
1165 skb_orphan(skb);
1166 skb->sk = sk;
1167 skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1168 skb_set_hash_from_sk(skb, sk);
1169 refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1170
1171 skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);
1172
1173 /* Build TCP header and checksum it. */
1174 th = (struct tcphdr *)skb->data;
1175 th->source = inet->inet_sport;
1176 th->dest = inet->inet_dport;
1177 th->seq = htonl(tcb->seq);
1178 th->ack_seq = htonl(rcv_nxt);
1179 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
1180 tcb->tcp_flags);
1181
1182 th->check = 0;
1183 th->urg_ptr = 0;
1184
1185 /* The urg_mode check is necessary during a below snd_una win probe */
1186 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
1187 if (before(tp->snd_up, tcb->seq + 0x10000)) {
1188 th->urg_ptr = htons(tp->snd_up - tcb->seq);
1189 th->urg = 1;
1190 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1191 th->urg_ptr = htons(0xFFFF);
1192 th->urg = 1;
1193 }
1194 }
1195
1196 tcp_options_write((__be32 *)(th + 1), tp, &opts);
1197 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1198 if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
1199 th->window = htons(tcp_select_window(sk));
1200 tcp_ecn_send(sk, skb, th, tcp_header_size);
1201 } else {
1202 /* RFC1323: The window in SYN & SYN/ACK segments
1203 * is never scaled.
1204 */
1205 th->window = htons(min(tp->rcv_wnd, 65535U));
1206 }
1207#ifdef CONFIG_TCP_MD5SIG
1208 /* Calculate the MD5 hash, as we have all we need now */
1209 if (md5) {
1210 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1211 tp->af_specific->calc_md5_hash(opts.hash_location,
1212 md5, sk, skb);
1213 }
1214#endif
1215
1216 INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check,
1217 tcp_v6_send_check, tcp_v4_send_check,
1218 sk, skb);
1219
1220 if (likely(tcb->tcp_flags & TCPHDR_ACK))
1221 tcp_event_ack_sent(sk, tcp_skb_pcount(skb), rcv_nxt);
1222
1223 if (skb->len != tcp_header_size) {
1224 tcp_event_data_sent(tp, sk);
1225 tp->data_segs_out += tcp_skb_pcount(skb);
1226 tp->bytes_sent += skb->len - tcp_header_size;
1227 }
1228
1229 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1230 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1231 tcp_skb_pcount(skb));
1232
1233 tp->segs_out += tcp_skb_pcount(skb);
1234 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1235 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1236 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1237
1238 /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */
1239
1240 /* Cleanup our debris for IP stacks */
1241 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1242 sizeof(struct inet6_skb_parm)));
1243
1244 tcp_add_tx_delay(skb, tp);
1245
1246 err = INDIRECT_CALL_INET(icsk->icsk_af_ops->queue_xmit,
1247 inet6_csk_xmit, ip_queue_xmit,
1248 sk, skb, &inet->cork.fl);
1249
1250 if (unlikely(err > 0)) {
1251 tcp_enter_cwr(sk);
1252 err = net_xmit_eval(err);
1253 }
1254 if (!err && oskb) {
1255 tcp_update_skb_after_send(sk, oskb, prior_wstamp);
1256 tcp_rate_skb_sent(sk, oskb);
1257 }
1258 return err;
1259}
1260
1261static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
1262 gfp_t gfp_mask)
1263{
1264 return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask,
1265 tcp_sk(sk)->rcv_nxt);
1266}
1267
1268/* This routine just queues the buffer for sending.
1269 *
1270 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1271 * otherwise socket can stall.
1272 */
1273static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1274{
1275 struct tcp_sock *tp = tcp_sk(sk);
1276
1277 /* Advance write_seq and place onto the write_queue. */
1278 WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq);
1279 __skb_header_release(skb);
1280 tcp_add_write_queue_tail(sk, skb);
1281 sk_wmem_queued_add(sk, skb->truesize);
1282 sk_mem_charge(sk, skb->truesize);
1283}
1284
1285/* Initialize TSO segments for a packet. */
1286static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1287{
1288 if (skb->len <= mss_now) {
1289 /* Avoid the costly divide in the normal
1290 * non-TSO case.
1291 */
1292 tcp_skb_pcount_set(skb, 1);
1293 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1294 } else {
1295 tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1296 TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1297 }
1298}
1299
1300/* Pcount in the middle of the write queue got changed, we need to do various
1301 * tweaks to fix counters
1302 */
1303static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1304{
1305 struct tcp_sock *tp = tcp_sk(sk);
1306
1307 tp->packets_out -= decr;
1308
1309 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1310 tp->sacked_out -= decr;
1311 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1312 tp->retrans_out -= decr;
1313 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1314 tp->lost_out -= decr;
1315
1316 /* Reno case is special. Sigh... */
1317 if (tcp_is_reno(tp) && decr > 0)
1318 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1319
1320 if (tp->lost_skb_hint &&
1321 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1322 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
1323 tp->lost_cnt_hint -= decr;
1324
1325 tcp_verify_left_out(tp);
1326}
1327
1328static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
1329{
1330 return TCP_SKB_CB(skb)->txstamp_ack ||
1331 (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
1332}
1333
1334static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1335{
1336 struct skb_shared_info *shinfo = skb_shinfo(skb);
1337
1338 if (unlikely(tcp_has_tx_tstamp(skb)) &&
1339 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1340 struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1341 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1342
1343 shinfo->tx_flags &= ~tsflags;
1344 shinfo2->tx_flags |= tsflags;
1345 swap(shinfo->tskey, shinfo2->tskey);
1346 TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
1347 TCP_SKB_CB(skb)->txstamp_ack = 0;
1348 }
1349}
1350
1351static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
1352{
1353 TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
1354 TCP_SKB_CB(skb)->eor = 0;
1355}
1356
1357/* Insert buff after skb on the write or rtx queue of sk. */
1358static void tcp_insert_write_queue_after(struct sk_buff *skb,
1359 struct sk_buff *buff,
1360 struct sock *sk,
1361 enum tcp_queue tcp_queue)
1362{
1363 if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
1364 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1365 else
1366 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
1367}
1368
1369/* Function to create two new TCP segments. Shrinks the given segment
1370 * to the specified size and appends a new segment with the rest of the
1371 * packet to the list. This won't be called frequently, I hope.
1372 * Remember, these are still headerless SKBs at this point.
1373 */
1374int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1375 struct sk_buff *skb, u32 len,
1376 unsigned int mss_now, gfp_t gfp)
1377{
1378 struct tcp_sock *tp = tcp_sk(sk);
1379 struct sk_buff *buff;
1380 int nsize, old_factor;
1381 long limit;
1382 int nlen;
1383 u8 flags;
1384
1385 if (WARN_ON(len > skb->len))
1386 return -EINVAL;
1387
1388 nsize = skb_headlen(skb) - len;
1389 if (nsize < 0)
1390 nsize = 0;
1391
1392 /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb.
1393 * We need some allowance to not penalize applications setting small
1394 * SO_SNDBUF values.
1395 * Also allow first and last skb in retransmit queue to be split.
1396 */
1397 limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_MAX_SIZE);
1398 if (unlikely((sk->sk_wmem_queued >> 1) > limit &&
1399 tcp_queue != TCP_FRAG_IN_WRITE_QUEUE &&
1400 skb != tcp_rtx_queue_head(sk) &&
1401 skb != tcp_rtx_queue_tail(sk))) {
1402 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG);
1403 return -ENOMEM;
1404 }
1405
1406 if (skb_unclone(skb, gfp))
1407 return -ENOMEM;
1408
1409 /* Get a new skb... force flag on. */
1410 buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1411 if (!buff)
1412 return -ENOMEM; /* We'll just try again later. */
1413 skb_copy_decrypted(buff, skb);
1414
1415 sk_wmem_queued_add(sk, buff->truesize);
1416 sk_mem_charge(sk, buff->truesize);
1417 nlen = skb->len - len - nsize;
1418 buff->truesize += nlen;
1419 skb->truesize -= nlen;
1420
1421 /* Correct the sequence numbers. */
1422 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1423 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1424 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1425
1426 /* PSH and FIN should only be set in the second packet. */
1427 flags = TCP_SKB_CB(skb)->tcp_flags;
1428 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1429 TCP_SKB_CB(buff)->tcp_flags = flags;
1430 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1431 tcp_skb_fragment_eor(skb, buff);
1432
1433 skb_split(skb, buff, len);
1434
1435 buff->ip_summed = CHECKSUM_PARTIAL;
1436
1437 buff->tstamp = skb->tstamp;
1438 tcp_fragment_tstamp(skb, buff);
1439
1440 old_factor = tcp_skb_pcount(skb);
1441
1442 /* Fix up tso_factor for both original and new SKB. */
1443 tcp_set_skb_tso_segs(skb, mss_now);
1444 tcp_set_skb_tso_segs(buff, mss_now);
1445
1446 /* Update delivered info for the new segment */
1447 TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
1448
1449 /* If this packet has been sent out already, we must
1450 * adjust the various packet counters.
1451 */
1452 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1453 int diff = old_factor - tcp_skb_pcount(skb) -
1454 tcp_skb_pcount(buff);
1455
1456 if (diff)
1457 tcp_adjust_pcount(sk, skb, diff);
1458 }
1459
1460 /* Link BUFF into the send queue. */
1461 __skb_header_release(buff);
1462 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1463 if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
1464 list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
1465
1466 return 0;
1467}
1468
1469/* This is similar to __pskb_pull_tail(). The difference is that pulled
1470 * data is not copied, but immediately discarded.
1471 */
1472static int __pskb_trim_head(struct sk_buff *skb, int len)
1473{
1474 struct skb_shared_info *shinfo;
1475 int i, k, eat;
1476
1477 eat = min_t(int, len, skb_headlen(skb));
1478 if (eat) {
1479 __skb_pull(skb, eat);
1480 len -= eat;
1481 if (!len)
1482 return 0;
1483 }
1484 eat = len;
1485 k = 0;
1486 shinfo = skb_shinfo(skb);
1487 for (i = 0; i < shinfo->nr_frags; i++) {
1488 int size = skb_frag_size(&shinfo->frags[i]);
1489
1490 if (size <= eat) {
1491 skb_frag_unref(skb, i);
1492 eat -= size;
1493 } else {
1494 shinfo->frags[k] = shinfo->frags[i];
1495 if (eat) {
1496 skb_frag_off_add(&shinfo->frags[k], eat);
1497 skb_frag_size_sub(&shinfo->frags[k], eat);
1498 eat = 0;
1499 }
1500 k++;
1501 }
1502 }
1503 shinfo->nr_frags = k;
1504
1505 skb->data_len -= len;
1506 skb->len = skb->data_len;
1507 return len;
1508}
1509
1510/* Remove acked data from a packet in the transmit queue. */
1511int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1512{
1513 u32 delta_truesize;
1514
1515 if (skb_unclone(skb, GFP_ATOMIC))
1516 return -ENOMEM;
1517
1518 delta_truesize = __pskb_trim_head(skb, len);
1519
1520 TCP_SKB_CB(skb)->seq += len;
1521 skb->ip_summed = CHECKSUM_PARTIAL;
1522
1523 if (delta_truesize) {
1524 skb->truesize -= delta_truesize;
1525 sk_wmem_queued_add(sk, -delta_truesize);
1526 sk_mem_uncharge(sk, delta_truesize);
1527 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1528 }
1529
1530 /* Any change of skb->len requires recalculation of tso factor. */
1531 if (tcp_skb_pcount(skb) > 1)
1532 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1533
1534 return 0;
1535}
1536
1537/* Calculate MSS not accounting any TCP options. */
1538static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1539{
1540 const struct tcp_sock *tp = tcp_sk(sk);
1541 const struct inet_connection_sock *icsk = inet_csk(sk);
1542 int mss_now;
1543
1544 /* Calculate base mss without TCP options:
1545 It is MMS_S - sizeof(tcphdr) of rfc1122
1546 */
1547 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1548
1549 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1550 if (icsk->icsk_af_ops->net_frag_header_len) {
1551 const struct dst_entry *dst = __sk_dst_get(sk);
1552
1553 if (dst && dst_allfrag(dst))
1554 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1555 }
1556
1557 /* Clamp it (mss_clamp does not include tcp options) */
1558 if (mss_now > tp->rx_opt.mss_clamp)
1559 mss_now = tp->rx_opt.mss_clamp;
1560
1561 /* Now subtract optional transport overhead */
1562 mss_now -= icsk->icsk_ext_hdr_len;
1563
1564 /* Then reserve room for full set of TCP options and 8 bytes of data */
1565 mss_now = max(mss_now, sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss);
1566 return mss_now;
1567}
1568
1569/* Calculate MSS. Not accounting for SACKs here. */
1570int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1571{
1572 /* Subtract TCP options size, not including SACKs */
1573 return __tcp_mtu_to_mss(sk, pmtu) -
1574 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1575}
1576
1577/* Inverse of above */
1578int tcp_mss_to_mtu(struct sock *sk, int mss)
1579{
1580 const struct tcp_sock *tp = tcp_sk(sk);
1581 const struct inet_connection_sock *icsk = inet_csk(sk);
1582 int mtu;
1583
1584 mtu = mss +
1585 tp->tcp_header_len +
1586 icsk->icsk_ext_hdr_len +
1587 icsk->icsk_af_ops->net_header_len;
1588
1589 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1590 if (icsk->icsk_af_ops->net_frag_header_len) {
1591 const struct dst_entry *dst = __sk_dst_get(sk);
1592
1593 if (dst && dst_allfrag(dst))
1594 mtu += icsk->icsk_af_ops->net_frag_header_len;
1595 }
1596 return mtu;
1597}
1598EXPORT_SYMBOL(tcp_mss_to_mtu);
1599
1600/* MTU probing init per socket */
1601void tcp_mtup_init(struct sock *sk)
1602{
1603 struct tcp_sock *tp = tcp_sk(sk);
1604 struct inet_connection_sock *icsk = inet_csk(sk);
1605 struct net *net = sock_net(sk);
1606
1607 icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
1608 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1609 icsk->icsk_af_ops->net_header_len;
1610 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
1611 icsk->icsk_mtup.probe_size = 0;
1612 if (icsk->icsk_mtup.enabled)
1613 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1614}
1615EXPORT_SYMBOL(tcp_mtup_init);
1616
1617/* This function synchronize snd mss to current pmtu/exthdr set.
1618
1619 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1620 for TCP options, but includes only bare TCP header.
1621
1622 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1623 It is minimum of user_mss and mss received with SYN.
1624 It also does not include TCP options.
1625
1626 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1627
1628 tp->mss_cache is current effective sending mss, including
1629 all tcp options except for SACKs. It is evaluated,
1630 taking into account current pmtu, but never exceeds
1631 tp->rx_opt.mss_clamp.
1632
1633 NOTE1. rfc1122 clearly states that advertised MSS
1634 DOES NOT include either tcp or ip options.
1635
1636 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1637 are READ ONLY outside this function. --ANK (980731)
1638 */
1639unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1640{
1641 struct tcp_sock *tp = tcp_sk(sk);
1642 struct inet_connection_sock *icsk = inet_csk(sk);
1643 int mss_now;
1644
1645 if (icsk->icsk_mtup.search_high > pmtu)
1646 icsk->icsk_mtup.search_high = pmtu;
1647
1648 mss_now = tcp_mtu_to_mss(sk, pmtu);
1649 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1650
1651 /* And store cached results */
1652 icsk->icsk_pmtu_cookie = pmtu;
1653 if (icsk->icsk_mtup.enabled)
1654 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1655 tp->mss_cache = mss_now;
1656
1657 return mss_now;
1658}
1659EXPORT_SYMBOL(tcp_sync_mss);
1660
1661/* Compute the current effective MSS, taking SACKs and IP options,
1662 * and even PMTU discovery events into account.
1663 */
1664unsigned int tcp_current_mss(struct sock *sk)
1665{
1666 const struct tcp_sock *tp = tcp_sk(sk);
1667 const struct dst_entry *dst = __sk_dst_get(sk);
1668 u32 mss_now;
1669 unsigned int header_len;
1670 struct tcp_out_options opts;
1671 struct tcp_md5sig_key *md5;
1672
1673 mss_now = tp->mss_cache;
1674
1675 if (dst) {
1676 u32 mtu = dst_mtu(dst);
1677 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1678 mss_now = tcp_sync_mss(sk, mtu);
1679 }
1680
1681 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1682 sizeof(struct tcphdr);
1683 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1684 * some common options. If this is an odd packet (because we have SACK
1685 * blocks etc) then our calculated header_len will be different, and
1686 * we have to adjust mss_now correspondingly */
1687 if (header_len != tp->tcp_header_len) {
1688 int delta = (int) header_len - tp->tcp_header_len;
1689 mss_now -= delta;
1690 }
1691
1692 return mss_now;
1693}
1694
1695/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1696 * As additional protections, we do not touch cwnd in retransmission phases,
1697 * and if application hit its sndbuf limit recently.
1698 */
1699static void tcp_cwnd_application_limited(struct sock *sk)
1700{
1701 struct tcp_sock *tp = tcp_sk(sk);
1702
1703 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
1704 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
1705 /* Limited by application or receiver window. */
1706 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
1707 u32 win_used = max(tp->snd_cwnd_used, init_win);
1708 if (win_used < tp->snd_cwnd) {
1709 tp->snd_ssthresh = tcp_current_ssthresh(sk);
1710 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
1711 }
1712 tp->snd_cwnd_used = 0;
1713 }
1714 tp->snd_cwnd_stamp = tcp_jiffies32;
1715}
1716
1717static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1718{
1719 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1720 struct tcp_sock *tp = tcp_sk(sk);
1721
1722 /* Track the maximum number of outstanding packets in each
1723 * window, and remember whether we were cwnd-limited then.
1724 */
1725 if (!before(tp->snd_una, tp->max_packets_seq) ||
1726 tp->packets_out > tp->max_packets_out) {
1727 tp->max_packets_out = tp->packets_out;
1728 tp->max_packets_seq = tp->snd_nxt;
1729 tp->is_cwnd_limited = is_cwnd_limited;
1730 }
1731
1732 if (tcp_is_cwnd_limited(sk)) {
1733 /* Network is feed fully. */
1734 tp->snd_cwnd_used = 0;
1735 tp->snd_cwnd_stamp = tcp_jiffies32;
1736 } else {
1737 /* Network starves. */
1738 if (tp->packets_out > tp->snd_cwnd_used)
1739 tp->snd_cwnd_used = tp->packets_out;
1740
1741 if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle &&
1742 (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1743 !ca_ops->cong_control)
1744 tcp_cwnd_application_limited(sk);
1745
1746 /* The following conditions together indicate the starvation
1747 * is caused by insufficient sender buffer:
1748 * 1) just sent some data (see tcp_write_xmit)
1749 * 2) not cwnd limited (this else condition)
1750 * 3) no more data to send (tcp_write_queue_empty())
1751 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1752 */
1753 if (tcp_write_queue_empty(sk) && sk->sk_socket &&
1754 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
1755 (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
1756 tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1757 }
1758}
1759
1760/* Minshall's variant of the Nagle send check. */
1761static bool tcp_minshall_check(const struct tcp_sock *tp)
1762{
1763 return after(tp->snd_sml, tp->snd_una) &&
1764 !after(tp->snd_sml, tp->snd_nxt);
1765}
1766
1767/* Update snd_sml if this skb is under mss
1768 * Note that a TSO packet might end with a sub-mss segment
1769 * The test is really :
1770 * if ((skb->len % mss) != 0)
1771 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1772 * But we can avoid doing the divide again given we already have
1773 * skb_pcount = skb->len / mss_now
1774 */
1775static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1776 const struct sk_buff *skb)
1777{
1778 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1779 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1780}
1781
1782/* Return false, if packet can be sent now without violation Nagle's rules:
1783 * 1. It is full sized. (provided by caller in %partial bool)
1784 * 2. Or it contains FIN. (already checked by caller)
1785 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1786 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1787 * With Minshall's modification: all sent small packets are ACKed.
1788 */
1789static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1790 int nonagle)
1791{
1792 return partial &&
1793 ((nonagle & TCP_NAGLE_CORK) ||
1794 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1795}
1796
1797/* Return how many segs we'd like on a TSO packet,
1798 * to send one TSO packet per ms
1799 */
1800static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
1801 int min_tso_segs)
1802{
1803 u32 bytes, segs;
1804
1805 bytes = min_t(unsigned long,
1806 sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift),
1807 sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);
1808
1809 /* Goal is to send at least one packet per ms,
1810 * not one big TSO packet every 100 ms.
1811 * This preserves ACK clocking and is consistent
1812 * with tcp_tso_should_defer() heuristic.
1813 */
1814 segs = max_t(u32, bytes / mss_now, min_tso_segs);
1815
1816 return segs;
1817}
1818
1819/* Return the number of segments we want in the skb we are transmitting.
1820 * See if congestion control module wants to decide; otherwise, autosize.
1821 */
1822static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
1823{
1824 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1825 u32 min_tso, tso_segs;
1826
1827 min_tso = ca_ops->min_tso_segs ?
1828 ca_ops->min_tso_segs(sk) :
1829 sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
1830
1831 tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
1832 return min_t(u32, tso_segs, sk->sk_gso_max_segs);
1833}
1834
1835/* Returns the portion of skb which can be sent right away */
1836static unsigned int tcp_mss_split_point(const struct sock *sk,
1837 const struct sk_buff *skb,
1838 unsigned int mss_now,
1839 unsigned int max_segs,
1840 int nonagle)
1841{
1842 const struct tcp_sock *tp = tcp_sk(sk);
1843 u32 partial, needed, window, max_len;
1844
1845 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1846 max_len = mss_now * max_segs;
1847
1848 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1849 return max_len;
1850
1851 needed = min(skb->len, window);
1852
1853 if (max_len <= needed)
1854 return max_len;
1855
1856 partial = needed % mss_now;
1857 /* If last segment is not a full MSS, check if Nagle rules allow us
1858 * to include this last segment in this skb.
1859 * Otherwise, we'll split the skb at last MSS boundary
1860 */
1861 if (tcp_nagle_check(partial != 0, tp, nonagle))
1862 return needed - partial;
1863
1864 return needed;
1865}
1866
1867/* Can at least one segment of SKB be sent right now, according to the
1868 * congestion window rules? If so, return how many segments are allowed.
1869 */
1870static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1871 const struct sk_buff *skb)
1872{
1873 u32 in_flight, cwnd, halfcwnd;
1874
1875 /* Don't be strict about the congestion window for the final FIN. */
1876 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1877 tcp_skb_pcount(skb) == 1)
1878 return 1;
1879
1880 in_flight = tcp_packets_in_flight(tp);
1881 cwnd = tp->snd_cwnd;
1882 if (in_flight >= cwnd)
1883 return 0;
1884
1885 /* For better scheduling, ensure we have at least
1886 * 2 GSO packets in flight.
1887 */
1888 halfcwnd = max(cwnd >> 1, 1U);
1889 return min(halfcwnd, cwnd - in_flight);
1890}
1891
1892/* Initialize TSO state of a skb.
1893 * This must be invoked the first time we consider transmitting
1894 * SKB onto the wire.
1895 */
1896static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1897{
1898 int tso_segs = tcp_skb_pcount(skb);
1899
1900 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1901 tcp_set_skb_tso_segs(skb, mss_now);
1902 tso_segs = tcp_skb_pcount(skb);
1903 }
1904 return tso_segs;
1905}
1906
1907
1908/* Return true if the Nagle test allows this packet to be
1909 * sent now.
1910 */
1911static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1912 unsigned int cur_mss, int nonagle)
1913{
1914 /* Nagle rule does not apply to frames, which sit in the middle of the
1915 * write_queue (they have no chances to get new data).
1916 *
1917 * This is implemented in the callers, where they modify the 'nonagle'
1918 * argument based upon the location of SKB in the send queue.
1919 */
1920 if (nonagle & TCP_NAGLE_PUSH)
1921 return true;
1922
1923 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1924 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1925 return true;
1926
1927 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
1928 return true;
1929
1930 return false;
1931}
1932
1933/* Does at least the first segment of SKB fit into the send window? */
1934static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1935 const struct sk_buff *skb,
1936 unsigned int cur_mss)
1937{
1938 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1939
1940 if (skb->len > cur_mss)
1941 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1942
1943 return !after(end_seq, tcp_wnd_end(tp));
1944}
1945
1946/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1947 * which is put after SKB on the list. It is very much like
1948 * tcp_fragment() except that it may make several kinds of assumptions
1949 * in order to speed up the splitting operation. In particular, we
1950 * know that all the data is in scatter-gather pages, and that the
1951 * packet has never been sent out before (and thus is not cloned).
1952 */
1953static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1954 unsigned int mss_now, gfp_t gfp)
1955{
1956 int nlen = skb->len - len;
1957 struct sk_buff *buff;
1958 u8 flags;
1959
1960 /* All of a TSO frame must be composed of paged data. */
1961 if (skb->len != skb->data_len)
1962 return tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
1963 skb, len, mss_now, gfp);
1964
1965 buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1966 if (unlikely(!buff))
1967 return -ENOMEM;
1968 skb_copy_decrypted(buff, skb);
1969
1970 sk_wmem_queued_add(sk, buff->truesize);
1971 sk_mem_charge(sk, buff->truesize);
1972 buff->truesize += nlen;
1973 skb->truesize -= nlen;
1974
1975 /* Correct the sequence numbers. */
1976 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1977 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1978 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1979
1980 /* PSH and FIN should only be set in the second packet. */
1981 flags = TCP_SKB_CB(skb)->tcp_flags;
1982 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1983 TCP_SKB_CB(buff)->tcp_flags = flags;
1984
1985 /* This packet was never sent out yet, so no SACK bits. */
1986 TCP_SKB_CB(buff)->sacked = 0;
1987
1988 tcp_skb_fragment_eor(skb, buff);
1989
1990 buff->ip_summed = CHECKSUM_PARTIAL;
1991 skb_split(skb, buff, len);
1992 tcp_fragment_tstamp(skb, buff);
1993
1994 /* Fix up tso_factor for both original and new SKB. */
1995 tcp_set_skb_tso_segs(skb, mss_now);
1996 tcp_set_skb_tso_segs(buff, mss_now);
1997
1998 /* Link BUFF into the send queue. */
1999 __skb_header_release(buff);
2000 tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE);
2001
2002 return 0;
2003}
2004
2005/* Try to defer sending, if possible, in order to minimize the amount
2006 * of TSO splitting we do. View it as a kind of TSO Nagle test.
2007 *
2008 * This algorithm is from John Heffner.
2009 */
2010static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
2011 bool *is_cwnd_limited,
2012 bool *is_rwnd_limited,
2013 u32 max_segs)
2014{
2015 const struct inet_connection_sock *icsk = inet_csk(sk);
2016 u32 send_win, cong_win, limit, in_flight;
2017 struct tcp_sock *tp = tcp_sk(sk);
2018 struct sk_buff *head;
2019 int win_divisor;
2020 s64 delta;
2021
2022 if (icsk->icsk_ca_state >= TCP_CA_Recovery)
2023 goto send_now;
2024
2025 /* Avoid bursty behavior by allowing defer
2026 * only if the last write was recent (1 ms).
2027 * Note that tp->tcp_wstamp_ns can be in the future if we have
2028 * packets waiting in a qdisc or device for EDT delivery.
2029 */
2030 delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC;
2031 if (delta > 0)
2032 goto send_now;
2033
2034 in_flight = tcp_packets_in_flight(tp);
2035
2036 BUG_ON(tcp_skb_pcount(skb) <= 1);
2037 BUG_ON(tp->snd_cwnd <= in_flight);
2038
2039 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2040
2041 /* From in_flight test above, we know that cwnd > in_flight. */
2042 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
2043
2044 limit = min(send_win, cong_win);
2045
2046 /* If a full-sized TSO skb can be sent, do it. */
2047 if (limit >= max_segs * tp->mss_cache)
2048 goto send_now;
2049
2050 /* Middle in queue won't get any more data, full sendable already? */
2051 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
2052 goto send_now;
2053
2054 win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
2055 if (win_divisor) {
2056 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
2057
2058 /* If at least some fraction of a window is available,
2059 * just use it.
2060 */
2061 chunk /= win_divisor;
2062 if (limit >= chunk)
2063 goto send_now;
2064 } else {
2065 /* Different approach, try not to defer past a single
2066 * ACK. Receiver should ACK every other full sized
2067 * frame, so if we have space for more than 3 frames
2068 * then send now.
2069 */
2070 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
2071 goto send_now;
2072 }
2073
2074 /* TODO : use tsorted_sent_queue ? */
2075 head = tcp_rtx_queue_head(sk);
2076 if (!head)
2077 goto send_now;
2078 delta = tp->tcp_clock_cache - head->tstamp;
2079 /* If next ACK is likely to come too late (half srtt), do not defer */
2080 if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0)
2081 goto send_now;
2082
2083 /* Ok, it looks like it is advisable to defer.
2084 * Three cases are tracked :
2085 * 1) We are cwnd-limited
2086 * 2) We are rwnd-limited
2087 * 3) We are application limited.
2088 */
2089 if (cong_win < send_win) {
2090 if (cong_win <= skb->len) {
2091 *is_cwnd_limited = true;
2092 return true;
2093 }
2094 } else {
2095 if (send_win <= skb->len) {
2096 *is_rwnd_limited = true;
2097 return true;
2098 }
2099 }
2100
2101 /* If this packet won't get more data, do not wait. */
2102 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
2103 TCP_SKB_CB(skb)->eor)
2104 goto send_now;
2105
2106 return true;
2107
2108send_now:
2109 return false;
2110}
2111
2112static inline void tcp_mtu_check_reprobe(struct sock *sk)
2113{
2114 struct inet_connection_sock *icsk = inet_csk(sk);
2115 struct tcp_sock *tp = tcp_sk(sk);
2116 struct net *net = sock_net(sk);
2117 u32 interval;
2118 s32 delta;
2119
2120 interval = net->ipv4.sysctl_tcp_probe_interval;
2121 delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2122 if (unlikely(delta >= interval * HZ)) {
2123 int mss = tcp_current_mss(sk);
2124
2125 /* Update current search range */
2126 icsk->icsk_mtup.probe_size = 0;
2127 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
2128 sizeof(struct tcphdr) +
2129 icsk->icsk_af_ops->net_header_len;
2130 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
2131
2132 /* Update probe time stamp */
2133 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2134 }
2135}
2136
2137static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
2138{
2139 struct sk_buff *skb, *next;
2140
2141 skb = tcp_send_head(sk);
2142 tcp_for_write_queue_from_safe(skb, next, sk) {
2143 if (len <= skb->len)
2144 break;
2145
2146 if (unlikely(TCP_SKB_CB(skb)->eor) || tcp_has_tx_tstamp(skb))
2147 return false;
2148
2149 len -= skb->len;
2150 }
2151
2152 return true;
2153}
2154
2155/* Create a new MTU probe if we are ready.
2156 * MTU probe is regularly attempting to increase the path MTU by
2157 * deliberately sending larger packets. This discovers routing
2158 * changes resulting in larger path MTUs.
2159 *
2160 * Returns 0 if we should wait to probe (no cwnd available),
2161 * 1 if a probe was sent,
2162 * -1 otherwise
2163 */
2164static int tcp_mtu_probe(struct sock *sk)
2165{
2166 struct inet_connection_sock *icsk = inet_csk(sk);
2167 struct tcp_sock *tp = tcp_sk(sk);
2168 struct sk_buff *skb, *nskb, *next;
2169 struct net *net = sock_net(sk);
2170 int probe_size;
2171 int size_needed;
2172 int copy, len;
2173 int mss_now;
2174 int interval;
2175
2176 /* Not currently probing/verifying,
2177 * not in recovery,
2178 * have enough cwnd, and
2179 * not SACKing (the variable headers throw things off)
2180 */
2181 if (likely(!icsk->icsk_mtup.enabled ||
2182 icsk->icsk_mtup.probe_size ||
2183 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
2184 tp->snd_cwnd < 11 ||
2185 tp->rx_opt.num_sacks || tp->rx_opt.dsack))
2186 return -1;
2187
2188 /* Use binary search for probe_size between tcp_mss_base,
2189 * and current mss_clamp. if (search_high - search_low)
2190 * smaller than a threshold, backoff from probing.
2191 */
2192 mss_now = tcp_current_mss(sk);
2193 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
2194 icsk->icsk_mtup.search_low) >> 1);
2195 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2196 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2197 /* When misfortune happens, we are reprobing actively,
2198 * and then reprobe timer has expired. We stick with current
2199 * probing process by not resetting search range to its orignal.
2200 */
2201 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2202 interval < net->ipv4.sysctl_tcp_probe_threshold) {
2203 /* Check whether enough time has elaplased for
2204 * another round of probing.
2205 */
2206 tcp_mtu_check_reprobe(sk);
2207 return -1;
2208 }
2209
2210 /* Have enough data in the send queue to probe? */
2211 if (tp->write_seq - tp->snd_nxt < size_needed)
2212 return -1;
2213
2214 if (tp->snd_wnd < size_needed)
2215 return -1;
2216 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2217 return 0;
2218
2219 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2220 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
2221 if (!tcp_packets_in_flight(tp))
2222 return -1;
2223 else
2224 return 0;
2225 }
2226
2227 if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
2228 return -1;
2229
2230 /* We're allowed to probe. Build it now. */
2231 nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2232 if (!nskb)
2233 return -1;
2234 sk_wmem_queued_add(sk, nskb->truesize);
2235 sk_mem_charge(sk, nskb->truesize);
2236
2237 skb = tcp_send_head(sk);
2238 skb_copy_decrypted(nskb, skb);
2239
2240 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
2241 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
2242 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
2243 TCP_SKB_CB(nskb)->sacked = 0;
2244 nskb->csum = 0;
2245 nskb->ip_summed = CHECKSUM_PARTIAL;
2246
2247 tcp_insert_write_queue_before(nskb, skb, sk);
2248 tcp_highest_sack_replace(sk, skb, nskb);
2249
2250 len = 0;
2251 tcp_for_write_queue_from_safe(skb, next, sk) {
2252 copy = min_t(int, skb->len, probe_size - len);
2253 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2254
2255 if (skb->len <= copy) {
2256 /* We've eaten all the data from this skb.
2257 * Throw it away. */
2258 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2259 /* If this is the last SKB we copy and eor is set
2260 * we need to propagate it to the new skb.
2261 */
2262 TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
2263 tcp_skb_collapse_tstamp(nskb, skb);
2264 tcp_unlink_write_queue(skb, sk);
2265 sk_wmem_free_skb(sk, skb);
2266 } else {
2267 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
2268 ~(TCPHDR_FIN|TCPHDR_PSH);
2269 if (!skb_shinfo(skb)->nr_frags) {
2270 skb_pull(skb, copy);
2271 } else {
2272 __pskb_trim_head(skb, copy);
2273 tcp_set_skb_tso_segs(skb, mss_now);
2274 }
2275 TCP_SKB_CB(skb)->seq += copy;
2276 }
2277
2278 len += copy;
2279
2280 if (len >= probe_size)
2281 break;
2282 }
2283 tcp_init_tso_segs(nskb, nskb->len);
2284
2285 /* We're ready to send. If this fails, the probe will
2286 * be resegmented into mss-sized pieces by tcp_write_xmit().
2287 */
2288 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
2289 /* Decrement cwnd here because we are sending
2290 * effectively two packets. */
2291 tp->snd_cwnd--;
2292 tcp_event_new_data_sent(sk, nskb);
2293
2294 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2295 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
2296 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
2297
2298 return 1;
2299 }
2300
2301 return -1;
2302}
2303
2304static bool tcp_pacing_check(struct sock *sk)
2305{
2306 struct tcp_sock *tp = tcp_sk(sk);
2307
2308 if (!tcp_needs_internal_pacing(sk))
2309 return false;
2310
2311 if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache)
2312 return false;
2313
2314 if (!hrtimer_is_queued(&tp->pacing_timer)) {
2315 hrtimer_start(&tp->pacing_timer,
2316 ns_to_ktime(tp->tcp_wstamp_ns),
2317 HRTIMER_MODE_ABS_PINNED_SOFT);
2318 sock_hold(sk);
2319 }
2320 return true;
2321}
2322
2323/* TCP Small Queues :
2324 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2325 * (These limits are doubled for retransmits)
2326 * This allows for :
2327 * - better RTT estimation and ACK scheduling
2328 * - faster recovery
2329 * - high rates
2330 * Alas, some drivers / subsystems require a fair amount
2331 * of queued bytes to ensure line rate.
2332 * One example is wifi aggregation (802.11 AMPDU)
2333 */
2334static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
2335 unsigned int factor)
2336{
2337 unsigned long limit;
2338
2339 limit = max_t(unsigned long,
2340 2 * skb->truesize,
2341 sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift));
2342 if (sk->sk_pacing_status == SK_PACING_NONE)
2343 limit = min_t(unsigned long, limit,
2344 sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
2345 limit <<= factor;
2346
2347 if (static_branch_unlikely(&tcp_tx_delay_enabled) &&
2348 tcp_sk(sk)->tcp_tx_delay) {
2349 u64 extra_bytes = (u64)sk->sk_pacing_rate * tcp_sk(sk)->tcp_tx_delay;
2350
2351 /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we
2352 * approximate our needs assuming an ~100% skb->truesize overhead.
2353 * USEC_PER_SEC is approximated by 2^20.
2354 * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift.
2355 */
2356 extra_bytes >>= (20 - 1);
2357 limit += extra_bytes;
2358 }
2359 if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2360 /* Always send skb if rtx queue is empty.
2361 * No need to wait for TX completion to call us back,
2362 * after softirq/tasklet schedule.
2363 * This helps when TX completions are delayed too much.
2364 */
2365 if (tcp_rtx_queue_empty(sk))
2366 return false;
2367
2368 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2369 /* It is possible TX completion already happened
2370 * before we set TSQ_THROTTLED, so we must
2371 * test again the condition.
2372 */
2373 smp_mb__after_atomic();
2374 if (refcount_read(&sk->sk_wmem_alloc) > limit)
2375 return true;
2376 }
2377 return false;
2378}
2379
2380static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
2381{
2382 const u32 now = tcp_jiffies32;
2383 enum tcp_chrono old = tp->chrono_type;
2384
2385 if (old > TCP_CHRONO_UNSPEC)
2386 tp->chrono_stat[old - 1] += now - tp->chrono_start;
2387 tp->chrono_start = now;
2388 tp->chrono_type = new;
2389}
2390
2391void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
2392{
2393 struct tcp_sock *tp = tcp_sk(sk);
2394
2395 /* If there are multiple conditions worthy of tracking in a
2396 * chronograph then the highest priority enum takes precedence
2397 * over the other conditions. So that if something "more interesting"
2398 * starts happening, stop the previous chrono and start a new one.
2399 */
2400 if (type > tp->chrono_type)
2401 tcp_chrono_set(tp, type);
2402}
2403
2404void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
2405{
2406 struct tcp_sock *tp = tcp_sk(sk);
2407
2408
2409 /* There are multiple conditions worthy of tracking in a
2410 * chronograph, so that the highest priority enum takes
2411 * precedence over the other conditions (see tcp_chrono_start).
2412 * If a condition stops, we only stop chrono tracking if
2413 * it's the "most interesting" or current chrono we are
2414 * tracking and starts busy chrono if we have pending data.
2415 */
2416 if (tcp_rtx_and_write_queues_empty(sk))
2417 tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
2418 else if (type == tp->chrono_type)
2419 tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2420}
2421
2422/* This routine writes packets to the network. It advances the
2423 * send_head. This happens as incoming acks open up the remote
2424 * window for us.
2425 *
2426 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2427 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2428 * account rare use of URG, this is not a big flaw.
2429 *
2430 * Send at most one packet when push_one > 0. Temporarily ignore
2431 * cwnd limit to force at most one packet out when push_one == 2.
2432
2433 * Returns true, if no segments are in flight and we have queued segments,
2434 * but cannot send anything now because of SWS or another problem.
2435 */
2436static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2437 int push_one, gfp_t gfp)
2438{
2439 struct tcp_sock *tp = tcp_sk(sk);
2440 struct sk_buff *skb;
2441 unsigned int tso_segs, sent_pkts;
2442 int cwnd_quota;
2443 int result;
2444 bool is_cwnd_limited = false, is_rwnd_limited = false;
2445 u32 max_segs;
2446
2447 sent_pkts = 0;
2448
2449 tcp_mstamp_refresh(tp);
2450 if (!push_one) {
2451 /* Do MTU probing. */
2452 result = tcp_mtu_probe(sk);
2453 if (!result) {
2454 return false;
2455 } else if (result > 0) {
2456 sent_pkts = 1;
2457 }
2458 }
2459
2460 max_segs = tcp_tso_segs(sk, mss_now);
2461 while ((skb = tcp_send_head(sk))) {
2462 unsigned int limit;
2463
2464 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2465 /* "skb_mstamp_ns" is used as a start point for the retransmit timer */
2466 skb->skb_mstamp_ns = tp->tcp_wstamp_ns = tp->tcp_clock_cache;
2467 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
2468 tcp_init_tso_segs(skb, mss_now);
2469 goto repair; /* Skip network transmission */
2470 }
2471
2472 if (tcp_pacing_check(sk))
2473 break;
2474
2475 tso_segs = tcp_init_tso_segs(skb, mss_now);
2476 BUG_ON(!tso_segs);
2477
2478 cwnd_quota = tcp_cwnd_test(tp, skb);
2479 if (!cwnd_quota) {
2480 if (push_one == 2)
2481 /* Force out a loss probe pkt. */
2482 cwnd_quota = 1;
2483 else
2484 break;
2485 }
2486
2487 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
2488 is_rwnd_limited = true;
2489 break;
2490 }
2491
2492 if (tso_segs == 1) {
2493 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2494 (tcp_skb_is_last(sk, skb) ?
2495 nonagle : TCP_NAGLE_PUSH))))
2496 break;
2497 } else {
2498 if (!push_one &&
2499 tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2500 &is_rwnd_limited, max_segs))
2501 break;
2502 }
2503
2504 limit = mss_now;
2505 if (tso_segs > 1 && !tcp_urg_mode(tp))
2506 limit = tcp_mss_split_point(sk, skb, mss_now,
2507 min_t(unsigned int,
2508 cwnd_quota,
2509 max_segs),
2510 nonagle);
2511
2512 if (skb->len > limit &&
2513 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
2514 break;
2515
2516 if (tcp_small_queue_check(sk, skb, 0))
2517 break;
2518
2519 /* Argh, we hit an empty skb(), presumably a thread
2520 * is sleeping in sendmsg()/sk_stream_wait_memory().
2521 * We do not want to send a pure-ack packet and have
2522 * a strange looking rtx queue with empty packet(s).
2523 */
2524 if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq)
2525 break;
2526
2527 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2528 break;
2529
2530repair:
2531 /* Advance the send_head. This one is sent out.
2532 * This call will increment packets_out.
2533 */
2534 tcp_event_new_data_sent(sk, skb);
2535
2536 tcp_minshall_update(tp, mss_now, skb);
2537 sent_pkts += tcp_skb_pcount(skb);
2538
2539 if (push_one)
2540 break;
2541 }
2542
2543 if (is_rwnd_limited)
2544 tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
2545 else
2546 tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
2547
2548 if (likely(sent_pkts)) {
2549 if (tcp_in_cwnd_reduction(sk))
2550 tp->prr_out += sent_pkts;
2551
2552 /* Send one loss probe per tail loss episode. */
2553 if (push_one != 2)
2554 tcp_schedule_loss_probe(sk, false);
2555 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2556 tcp_cwnd_validate(sk, is_cwnd_limited);
2557 return false;
2558 }
2559 return !tp->packets_out && !tcp_write_queue_empty(sk);
2560}
2561
2562bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
2563{
2564 struct inet_connection_sock *icsk = inet_csk(sk);
2565 struct tcp_sock *tp = tcp_sk(sk);
2566 u32 timeout, rto_delta_us;
2567 int early_retrans;
2568
2569 /* Don't do any loss probe on a Fast Open connection before 3WHS
2570 * finishes.
2571 */
2572 if (rcu_access_pointer(tp->fastopen_rsk))
2573 return false;
2574
2575 early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
2576 /* Schedule a loss probe in 2*RTT for SACK capable connections
2577 * not in loss recovery, that are either limited by cwnd or application.
2578 */
2579 if ((early_retrans != 3 && early_retrans != 4) ||
2580 !tp->packets_out || !tcp_is_sack(tp) ||
2581 (icsk->icsk_ca_state != TCP_CA_Open &&
2582 icsk->icsk_ca_state != TCP_CA_CWR))
2583 return false;
2584
2585 /* Probe timeout is 2*rtt. Add minimum RTO to account
2586 * for delayed ack when there's one outstanding packet. If no RTT
2587 * sample is available then probe after TCP_TIMEOUT_INIT.
2588 */
2589 if (tp->srtt_us) {
2590 timeout = usecs_to_jiffies(tp->srtt_us >> 2);
2591 if (tp->packets_out == 1)
2592 timeout += TCP_RTO_MIN;
2593 else
2594 timeout += TCP_TIMEOUT_MIN;
2595 } else {
2596 timeout = TCP_TIMEOUT_INIT;
2597 }
2598
2599 /* If the RTO formula yields an earlier time, then use that time. */
2600 rto_delta_us = advancing_rto ?
2601 jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
2602 tcp_rto_delta_us(sk); /* How far in future is RTO? */
2603 if (rto_delta_us > 0)
2604 timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
2605
2606 tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, TCP_RTO_MAX);
2607 return true;
2608}
2609
2610/* Thanks to skb fast clones, we can detect if a prior transmit of
2611 * a packet is still in a qdisc or driver queue.
2612 * In this case, there is very little point doing a retransmit !
2613 */
2614static bool skb_still_in_host_queue(const struct sock *sk,
2615 const struct sk_buff *skb)
2616{
2617 if (unlikely(skb_fclone_busy(sk, skb))) {
2618 NET_INC_STATS(sock_net(sk),
2619 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2620 return true;
2621 }
2622 return false;
2623}
2624
2625/* When probe timeout (PTO) fires, try send a new segment if possible, else
2626 * retransmit the last segment.
2627 */
2628void tcp_send_loss_probe(struct sock *sk)
2629{
2630 struct tcp_sock *tp = tcp_sk(sk);
2631 struct sk_buff *skb;
2632 int pcount;
2633 int mss = tcp_current_mss(sk);
2634
2635 /* At most one outstanding TLP */
2636 if (tp->tlp_high_seq)
2637 goto rearm_timer;
2638
2639 tp->tlp_retrans = 0;
2640 skb = tcp_send_head(sk);
2641 if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
2642 pcount = tp->packets_out;
2643 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2644 if (tp->packets_out > pcount)
2645 goto probe_sent;
2646 goto rearm_timer;
2647 }
2648 skb = skb_rb_last(&sk->tcp_rtx_queue);
2649 if (unlikely(!skb)) {
2650 WARN_ONCE(tp->packets_out,
2651 "invalid inflight: %u state %u cwnd %u mss %d\n",
2652 tp->packets_out, sk->sk_state, tp->snd_cwnd, mss);
2653 inet_csk(sk)->icsk_pending = 0;
2654 return;
2655 }
2656
2657 if (skb_still_in_host_queue(sk, skb))
2658 goto rearm_timer;
2659
2660 pcount = tcp_skb_pcount(skb);
2661 if (WARN_ON(!pcount))
2662 goto rearm_timer;
2663
2664 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2665 if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
2666 (pcount - 1) * mss, mss,
2667 GFP_ATOMIC)))
2668 goto rearm_timer;
2669 skb = skb_rb_next(skb);
2670 }
2671
2672 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2673 goto rearm_timer;
2674
2675 if (__tcp_retransmit_skb(sk, skb, 1))
2676 goto rearm_timer;
2677
2678 tp->tlp_retrans = 1;
2679
2680probe_sent:
2681 /* Record snd_nxt for loss detection. */
2682 tp->tlp_high_seq = tp->snd_nxt;
2683
2684 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2685 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2686 inet_csk(sk)->icsk_pending = 0;
2687rearm_timer:
2688 tcp_rearm_rto(sk);
2689}
2690
2691/* Push out any pending frames which were held back due to
2692 * TCP_CORK or attempt at coalescing tiny packets.
2693 * The socket must be locked by the caller.
2694 */
2695void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2696 int nonagle)
2697{
2698 /* If we are closed, the bytes will have to remain here.
2699 * In time closedown will finish, we empty the write queue and
2700 * all will be happy.
2701 */
2702 if (unlikely(sk->sk_state == TCP_CLOSE))
2703 return;
2704
2705 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2706 sk_gfp_mask(sk, GFP_ATOMIC)))
2707 tcp_check_probe_timer(sk);
2708}
2709
2710/* Send _single_ skb sitting at the send head. This function requires
2711 * true push pending frames to setup probe timer etc.
2712 */
2713void tcp_push_one(struct sock *sk, unsigned int mss_now)
2714{
2715 struct sk_buff *skb = tcp_send_head(sk);
2716
2717 BUG_ON(!skb || skb->len < mss_now);
2718
2719 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2720}
2721
2722/* This function returns the amount that we can raise the
2723 * usable window based on the following constraints
2724 *
2725 * 1. The window can never be shrunk once it is offered (RFC 793)
2726 * 2. We limit memory per socket
2727 *
2728 * RFC 1122:
2729 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2730 * RECV.NEXT + RCV.WIN fixed until:
2731 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2732 *
2733 * i.e. don't raise the right edge of the window until you can raise
2734 * it at least MSS bytes.
2735 *
2736 * Unfortunately, the recommended algorithm breaks header prediction,
2737 * since header prediction assumes th->window stays fixed.
2738 *
2739 * Strictly speaking, keeping th->window fixed violates the receiver
2740 * side SWS prevention criteria. The problem is that under this rule
2741 * a stream of single byte packets will cause the right side of the
2742 * window to always advance by a single byte.
2743 *
2744 * Of course, if the sender implements sender side SWS prevention
2745 * then this will not be a problem.
2746 *
2747 * BSD seems to make the following compromise:
2748 *
2749 * If the free space is less than the 1/4 of the maximum
2750 * space available and the free space is less than 1/2 mss,
2751 * then set the window to 0.
2752 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2753 * Otherwise, just prevent the window from shrinking
2754 * and from being larger than the largest representable value.
2755 *
2756 * This prevents incremental opening of the window in the regime
2757 * where TCP is limited by the speed of the reader side taking
2758 * data out of the TCP receive queue. It does nothing about
2759 * those cases where the window is constrained on the sender side
2760 * because the pipeline is full.
2761 *
2762 * BSD also seems to "accidentally" limit itself to windows that are a
2763 * multiple of MSS, at least until the free space gets quite small.
2764 * This would appear to be a side effect of the mbuf implementation.
2765 * Combining these two algorithms results in the observed behavior
2766 * of having a fixed window size at almost all times.
2767 *
2768 * Below we obtain similar behavior by forcing the offered window to
2769 * a multiple of the mss when it is feasible to do so.
2770 *
2771 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2772 * Regular options like TIMESTAMP are taken into account.
2773 */
2774u32 __tcp_select_window(struct sock *sk)
2775{
2776 struct inet_connection_sock *icsk = inet_csk(sk);
2777 struct tcp_sock *tp = tcp_sk(sk);
2778 /* MSS for the peer's data. Previous versions used mss_clamp
2779 * here. I don't know if the value based on our guesses
2780 * of peer's MSS is better for the performance. It's more correct
2781 * but may be worse for the performance because of rcv_mss
2782 * fluctuations. --SAW 1998/11/1
2783 */
2784 int mss = icsk->icsk_ack.rcv_mss;
2785 int free_space = tcp_space(sk);
2786 int allowed_space = tcp_full_space(sk);
2787 int full_space, window;
2788
2789 if (sk_is_mptcp(sk))
2790 mptcp_space(sk, &free_space, &allowed_space);
2791
2792 full_space = min_t(int, tp->window_clamp, allowed_space);
2793
2794 if (unlikely(mss > full_space)) {
2795 mss = full_space;
2796 if (mss <= 0)
2797 return 0;
2798 }
2799 if (free_space < (full_space >> 1)) {
2800 icsk->icsk_ack.quick = 0;
2801
2802 if (tcp_under_memory_pressure(sk))
2803 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2804 4U * tp->advmss);
2805
2806 /* free_space might become our new window, make sure we don't
2807 * increase it due to wscale.
2808 */
2809 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2810
2811 /* if free space is less than mss estimate, or is below 1/16th
2812 * of the maximum allowed, try to move to zero-window, else
2813 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2814 * new incoming data is dropped due to memory limits.
2815 * With large window, mss test triggers way too late in order
2816 * to announce zero window in time before rmem limit kicks in.
2817 */
2818 if (free_space < (allowed_space >> 4) || free_space < mss)
2819 return 0;
2820 }
2821
2822 if (free_space > tp->rcv_ssthresh)
2823 free_space = tp->rcv_ssthresh;
2824
2825 /* Don't do rounding if we are using window scaling, since the
2826 * scaled window will not line up with the MSS boundary anyway.
2827 */
2828 if (tp->rx_opt.rcv_wscale) {
2829 window = free_space;
2830
2831 /* Advertise enough space so that it won't get scaled away.
2832 * Import case: prevent zero window announcement if
2833 * 1<<rcv_wscale > mss.
2834 */
2835 window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
2836 } else {
2837 window = tp->rcv_wnd;
2838 /* Get the largest window that is a nice multiple of mss.
2839 * Window clamp already applied above.
2840 * If our current window offering is within 1 mss of the
2841 * free space we just keep it. This prevents the divide
2842 * and multiply from happening most of the time.
2843 * We also don't do any window rounding when the free space
2844 * is too small.
2845 */
2846 if (window <= free_space - mss || window > free_space)
2847 window = rounddown(free_space, mss);
2848 else if (mss == full_space &&
2849 free_space > window + (full_space >> 1))
2850 window = free_space;
2851 }
2852
2853 return window;
2854}
2855
2856void tcp_skb_collapse_tstamp(struct sk_buff *skb,
2857 const struct sk_buff *next_skb)
2858{
2859 if (unlikely(tcp_has_tx_tstamp(next_skb))) {
2860 const struct skb_shared_info *next_shinfo =
2861 skb_shinfo(next_skb);
2862 struct skb_shared_info *shinfo = skb_shinfo(skb);
2863
2864 shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2865 shinfo->tskey = next_shinfo->tskey;
2866 TCP_SKB_CB(skb)->txstamp_ack |=
2867 TCP_SKB_CB(next_skb)->txstamp_ack;
2868 }
2869}
2870
2871/* Collapses two adjacent SKB's during retransmission. */
2872static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
2873{
2874 struct tcp_sock *tp = tcp_sk(sk);
2875 struct sk_buff *next_skb = skb_rb_next(skb);
2876 int next_skb_size;
2877
2878 next_skb_size = next_skb->len;
2879
2880 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2881
2882 if (next_skb_size) {
2883 if (next_skb_size <= skb_availroom(skb))
2884 skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
2885 next_skb_size);
2886 else if (!tcp_skb_shift(skb, next_skb, 1, next_skb_size))
2887 return false;
2888 }
2889 tcp_highest_sack_replace(sk, next_skb, skb);
2890
2891 /* Update sequence range on original skb. */
2892 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2893
2894 /* Merge over control information. This moves PSH/FIN etc. over */
2895 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2896
2897 /* All done, get rid of second SKB and account for it so
2898 * packet counting does not break.
2899 */
2900 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2901 TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2902
2903 /* changed transmit queue under us so clear hints */
2904 tcp_clear_retrans_hints_partial(tp);
2905 if (next_skb == tp->retransmit_skb_hint)
2906 tp->retransmit_skb_hint = skb;
2907
2908 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2909
2910 tcp_skb_collapse_tstamp(skb, next_skb);
2911
2912 tcp_rtx_queue_unlink_and_free(next_skb, sk);
2913 return true;
2914}
2915
2916/* Check if coalescing SKBs is legal. */
2917static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2918{
2919 if (tcp_skb_pcount(skb) > 1)
2920 return false;
2921 if (skb_cloned(skb))
2922 return false;
2923 /* Some heuristics for collapsing over SACK'd could be invented */
2924 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2925 return false;
2926
2927 return true;
2928}
2929
2930/* Collapse packets in the retransmit queue to make to create
2931 * less packets on the wire. This is only done on retransmission.
2932 */
2933static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2934 int space)
2935{
2936 struct tcp_sock *tp = tcp_sk(sk);
2937 struct sk_buff *skb = to, *tmp;
2938 bool first = true;
2939
2940 if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
2941 return;
2942 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2943 return;
2944
2945 skb_rbtree_walk_from_safe(skb, tmp) {
2946 if (!tcp_can_collapse(sk, skb))
2947 break;
2948
2949 if (!tcp_skb_can_collapse(to, skb))
2950 break;
2951
2952 space -= skb->len;
2953
2954 if (first) {
2955 first = false;
2956 continue;
2957 }
2958
2959 if (space < 0)
2960 break;
2961
2962 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2963 break;
2964
2965 if (!tcp_collapse_retrans(sk, to))
2966 break;
2967 }
2968}
2969
2970/* This retransmits one SKB. Policy decisions and retransmit queue
2971 * state updates are done by the caller. Returns non-zero if an
2972 * error occurred which prevented the send.
2973 */
2974int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2975{
2976 struct inet_connection_sock *icsk = inet_csk(sk);
2977 struct tcp_sock *tp = tcp_sk(sk);
2978 unsigned int cur_mss;
2979 int diff, len, err;
2980
2981
2982 /* Inconclusive MTU probe */
2983 if (icsk->icsk_mtup.probe_size)
2984 icsk->icsk_mtup.probe_size = 0;
2985
2986 /* Do not sent more than we queued. 1/4 is reserved for possible
2987 * copying overhead: fragmentation, tunneling, mangling etc.
2988 */
2989 if (refcount_read(&sk->sk_wmem_alloc) >
2990 min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
2991 sk->sk_sndbuf))
2992 return -EAGAIN;
2993
2994 if (skb_still_in_host_queue(sk, skb))
2995 return -EBUSY;
2996
2997 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2998 if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
2999 WARN_ON_ONCE(1);
3000 return -EINVAL;
3001 }
3002 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3003 return -ENOMEM;
3004 }
3005
3006 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3007 return -EHOSTUNREACH; /* Routing failure or similar. */
3008
3009 cur_mss = tcp_current_mss(sk);
3010
3011 /* If receiver has shrunk his window, and skb is out of
3012 * new window, do not retransmit it. The exception is the
3013 * case, when window is shrunk to zero. In this case
3014 * our retransmit serves as a zero window probe.
3015 */
3016 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
3017 TCP_SKB_CB(skb)->seq != tp->snd_una)
3018 return -EAGAIN;
3019
3020 len = cur_mss * segs;
3021 if (skb->len > len) {
3022 if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
3023 cur_mss, GFP_ATOMIC))
3024 return -ENOMEM; /* We'll try again later. */
3025 } else {
3026 if (skb_unclone(skb, GFP_ATOMIC))
3027 return -ENOMEM;
3028
3029 diff = tcp_skb_pcount(skb);
3030 tcp_set_skb_tso_segs(skb, cur_mss);
3031 diff -= tcp_skb_pcount(skb);
3032 if (diff)
3033 tcp_adjust_pcount(sk, skb, diff);
3034 if (skb->len < cur_mss)
3035 tcp_retrans_try_collapse(sk, skb, cur_mss);
3036 }
3037
3038 /* RFC3168, section 6.1.1.1. ECN fallback */
3039 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
3040 tcp_ecn_clear_syn(sk, skb);
3041
3042 /* Update global and local TCP statistics. */
3043 segs = tcp_skb_pcount(skb);
3044 TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
3045 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3046 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3047 tp->total_retrans += segs;
3048 tp->bytes_retrans += skb->len;
3049
3050 /* make sure skb->data is aligned on arches that require it
3051 * and check if ack-trimming & collapsing extended the headroom
3052 * beyond what csum_start can cover.
3053 */
3054 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
3055 skb_headroom(skb) >= 0xFFFF)) {
3056 struct sk_buff *nskb;
3057
3058 tcp_skb_tsorted_save(skb) {
3059 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
3060 if (nskb) {
3061 nskb->dev = NULL;
3062 err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC);
3063 } else {
3064 err = -ENOBUFS;
3065 }
3066 } tcp_skb_tsorted_restore(skb);
3067
3068 if (!err) {
3069 tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns);
3070 tcp_rate_skb_sent(sk, skb);
3071 }
3072 } else {
3073 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3074 }
3075
3076 /* To avoid taking spuriously low RTT samples based on a timestamp
3077 * for a transmit that never happened, always mark EVER_RETRANS
3078 */
3079 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
3080
3081 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
3082 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
3083 TCP_SKB_CB(skb)->seq, segs, err);
3084
3085 if (likely(!err)) {
3086 trace_tcp_retransmit_skb(sk, skb);
3087 } else if (err != -EBUSY) {
3088 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
3089 }
3090 return err;
3091}
3092
3093int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3094{
3095 struct tcp_sock *tp = tcp_sk(sk);
3096 int err = __tcp_retransmit_skb(sk, skb, segs);
3097
3098 if (err == 0) {
3099#if FASTRETRANS_DEBUG > 0
3100 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
3101 net_dbg_ratelimited("retrans_out leaked\n");
3102 }
3103#endif
3104 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
3105 tp->retrans_out += tcp_skb_pcount(skb);
3106 }
3107
3108 /* Save stamp of the first (attempted) retransmit. */
3109 if (!tp->retrans_stamp)
3110 tp->retrans_stamp = tcp_skb_timestamp(skb);
3111
3112 if (tp->undo_retrans < 0)
3113 tp->undo_retrans = 0;
3114 tp->undo_retrans += tcp_skb_pcount(skb);
3115 return err;
3116}
3117
3118/* This gets called after a retransmit timeout, and the initially
3119 * retransmitted data is acknowledged. It tries to continue
3120 * resending the rest of the retransmit queue, until either
3121 * we've sent it all or the congestion window limit is reached.
3122 */
3123void tcp_xmit_retransmit_queue(struct sock *sk)
3124{
3125 const struct inet_connection_sock *icsk = inet_csk(sk);
3126 struct sk_buff *skb, *rtx_head, *hole = NULL;
3127 struct tcp_sock *tp = tcp_sk(sk);
3128 bool rearm_timer = false;
3129 u32 max_segs;
3130 int mib_idx;
3131
3132 if (!tp->packets_out)
3133 return;
3134
3135 rtx_head = tcp_rtx_queue_head(sk);
3136 skb = tp->retransmit_skb_hint ?: rtx_head;
3137 max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
3138 skb_rbtree_walk_from(skb) {
3139 __u8 sacked;
3140 int segs;
3141
3142 if (tcp_pacing_check(sk))
3143 break;
3144
3145 /* we could do better than to assign each time */
3146 if (!hole)
3147 tp->retransmit_skb_hint = skb;
3148
3149 segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
3150 if (segs <= 0)
3151 break;
3152 sacked = TCP_SKB_CB(skb)->sacked;
3153 /* In case tcp_shift_skb_data() have aggregated large skbs,
3154 * we need to make sure not sending too bigs TSO packets
3155 */
3156 segs = min_t(int, segs, max_segs);
3157
3158 if (tp->retrans_out >= tp->lost_out) {
3159 break;
3160 } else if (!(sacked & TCPCB_LOST)) {
3161 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
3162 hole = skb;
3163 continue;
3164
3165 } else {
3166 if (icsk->icsk_ca_state != TCP_CA_Loss)
3167 mib_idx = LINUX_MIB_TCPFASTRETRANS;
3168 else
3169 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
3170 }
3171
3172 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
3173 continue;
3174
3175 if (tcp_small_queue_check(sk, skb, 1))
3176 break;
3177
3178 if (tcp_retransmit_skb(sk, skb, segs))
3179 break;
3180
3181 NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
3182
3183 if (tcp_in_cwnd_reduction(sk))
3184 tp->prr_out += tcp_skb_pcount(skb);
3185
3186 if (skb == rtx_head &&
3187 icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3188 rearm_timer = true;
3189
3190 }
3191 if (rearm_timer)
3192 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3193 inet_csk(sk)->icsk_rto,
3194 TCP_RTO_MAX);
3195}
3196
3197/* We allow to exceed memory limits for FIN packets to expedite
3198 * connection tear down and (memory) recovery.
3199 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3200 * or even be forced to close flow without any FIN.
3201 * In general, we want to allow one skb per socket to avoid hangs
3202 * with edge trigger epoll()
3203 */
3204void sk_forced_mem_schedule(struct sock *sk, int size)
3205{
3206 int amt;
3207
3208 if (size <= sk->sk_forward_alloc)
3209 return;
3210 amt = sk_mem_pages(size);
3211 sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
3212 sk_memory_allocated_add(sk, amt);
3213
3214 if (mem_cgroup_sockets_enabled && sk->sk_memcg)
3215 mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3216}
3217
3218/* Send a FIN. The caller locks the socket for us.
3219 * We should try to send a FIN packet really hard, but eventually give up.
3220 */
3221void tcp_send_fin(struct sock *sk)
3222{
3223 struct sk_buff *skb, *tskb, *tail = tcp_write_queue_tail(sk);
3224 struct tcp_sock *tp = tcp_sk(sk);
3225
3226 /* Optimization, tack on the FIN if we have one skb in write queue and
3227 * this skb was not yet sent, or we are under memory pressure.
3228 * Note: in the latter case, FIN packet will be sent after a timeout,
3229 * as TCP stack thinks it has already been transmitted.
3230 */
3231 tskb = tail;
3232 if (!tskb && tcp_under_memory_pressure(sk))
3233 tskb = skb_rb_last(&sk->tcp_rtx_queue);
3234
3235 if (tskb) {
3236 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
3237 TCP_SKB_CB(tskb)->end_seq++;
3238 tp->write_seq++;
3239 if (!tail) {
3240 /* This means tskb was already sent.
3241 * Pretend we included the FIN on previous transmit.
3242 * We need to set tp->snd_nxt to the value it would have
3243 * if FIN had been sent. This is because retransmit path
3244 * does not change tp->snd_nxt.
3245 */
3246 WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1);
3247 return;
3248 }
3249 } else {
3250 skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
3251 if (unlikely(!skb))
3252 return;
3253
3254 INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3255 skb_reserve(skb, MAX_TCP_HEADER);
3256 sk_forced_mem_schedule(sk, skb->truesize);
3257 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3258 tcp_init_nondata_skb(skb, tp->write_seq,
3259 TCPHDR_ACK | TCPHDR_FIN);
3260 tcp_queue_skb(sk, skb);
3261 }
3262 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
3263}
3264
3265/* We get here when a process closes a file descriptor (either due to
3266 * an explicit close() or as a byproduct of exit()'ing) and there
3267 * was unread data in the receive queue. This behavior is recommended
3268 * by RFC 2525, section 2.17. -DaveM
3269 */
3270void tcp_send_active_reset(struct sock *sk, gfp_t priority)
3271{
3272 struct sk_buff *skb;
3273
3274 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
3275
3276 /* NOTE: No TCP options attached and we never retransmit this. */
3277 skb = alloc_skb(MAX_TCP_HEADER, priority);
3278 if (!skb) {
3279 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3280 return;
3281 }
3282
3283 /* Reserve space for headers and prepare control bits. */
3284 skb_reserve(skb, MAX_TCP_HEADER);
3285 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
3286 TCPHDR_ACK | TCPHDR_RST);
3287 tcp_mstamp_refresh(tcp_sk(sk));
3288 /* Send it off. */
3289 if (tcp_transmit_skb(sk, skb, 0, priority))
3290 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3291
3292 /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3293 * skb here is different to the troublesome skb, so use NULL
3294 */
3295 trace_tcp_send_reset(sk, NULL);
3296}
3297
3298/* Send a crossed SYN-ACK during socket establishment.
3299 * WARNING: This routine must only be called when we have already sent
3300 * a SYN packet that crossed the incoming SYN that caused this routine
3301 * to get called. If this assumption fails then the initial rcv_wnd
3302 * and rcv_wscale values will not be correct.
3303 */
3304int tcp_send_synack(struct sock *sk)
3305{
3306 struct sk_buff *skb;
3307
3308 skb = tcp_rtx_queue_head(sk);
3309 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3310 pr_err("%s: wrong queue state\n", __func__);
3311 return -EFAULT;
3312 }
3313 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
3314 if (skb_cloned(skb)) {
3315 struct sk_buff *nskb;
3316
3317 tcp_skb_tsorted_save(skb) {
3318 nskb = skb_copy(skb, GFP_ATOMIC);
3319 } tcp_skb_tsorted_restore(skb);
3320 if (!nskb)
3321 return -ENOMEM;
3322 INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3323 tcp_highest_sack_replace(sk, skb, nskb);
3324 tcp_rtx_queue_unlink_and_free(skb, sk);
3325 __skb_header_release(nskb);
3326 tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3327 sk_wmem_queued_add(sk, nskb->truesize);
3328 sk_mem_charge(sk, nskb->truesize);
3329 skb = nskb;
3330 }
3331
3332 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3333 tcp_ecn_send_synack(sk, skb);
3334 }
3335 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3336}
3337
3338/**
3339 * tcp_make_synack - Prepare a SYN-ACK.
3340 * sk: listener socket
3341 * dst: dst entry attached to the SYNACK
3342 * req: request_sock pointer
3343 * foc: cookie for tcp fast open
3344 * synack_type: Type of synback to prepare
3345 *
3346 * Allocate one skb and build a SYNACK packet.
3347 * @dst is consumed : Caller should not use it again.
3348 */
3349struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3350 struct request_sock *req,
3351 struct tcp_fastopen_cookie *foc,
3352 enum tcp_synack_type synack_type)
3353{
3354 struct inet_request_sock *ireq = inet_rsk(req);
3355 const struct tcp_sock *tp = tcp_sk(sk);
3356 struct tcp_md5sig_key *md5 = NULL;
3357 struct tcp_out_options opts;
3358 struct sk_buff *skb;
3359 int tcp_header_size;
3360 struct tcphdr *th;
3361 int mss;
3362 u64 now;
3363
3364 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3365 if (unlikely(!skb)) {
3366 dst_release(dst);
3367 return NULL;
3368 }
3369 /* Reserve space for headers. */
3370 skb_reserve(skb, MAX_TCP_HEADER);
3371
3372 switch (synack_type) {
3373 case TCP_SYNACK_NORMAL:
3374 skb_set_owner_w(skb, req_to_sk(req));
3375 break;
3376 case TCP_SYNACK_COOKIE:
3377 /* Under synflood, we do not attach skb to a socket,
3378 * to avoid false sharing.
3379 */
3380 break;
3381 case TCP_SYNACK_FASTOPEN:
3382 /* sk is a const pointer, because we want to express multiple
3383 * cpu might call us concurrently.
3384 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3385 */
3386 skb_set_owner_w(skb, (struct sock *)sk);
3387 break;
3388 }
3389 skb_dst_set(skb, dst);
3390
3391 mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3392
3393 memset(&opts, 0, sizeof(opts));
3394 now = tcp_clock_ns();
3395#ifdef CONFIG_SYN_COOKIES
3396 if (unlikely(synack_type == TCP_SYNACK_COOKIE && ireq->tstamp_ok))
3397 skb->skb_mstamp_ns = cookie_init_timestamp(req, now);
3398 else
3399#endif
3400 {
3401 skb->skb_mstamp_ns = now;
3402 if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */
3403 tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);
3404 }
3405
3406#ifdef CONFIG_TCP_MD5SIG
3407 rcu_read_lock();
3408 md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
3409#endif
3410 skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3411 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
3412 foc, synack_type) + sizeof(*th);
3413
3414 skb_push(skb, tcp_header_size);
3415 skb_reset_transport_header(skb);
3416
3417 th = (struct tcphdr *)skb->data;
3418 memset(th, 0, sizeof(struct tcphdr));
3419 th->syn = 1;
3420 th->ack = 1;
3421 tcp_ecn_make_synack(req, th);
3422 th->source = htons(ireq->ir_num);
3423 th->dest = ireq->ir_rmt_port;
3424 skb->mark = ireq->ir_mark;
3425 skb->ip_summed = CHECKSUM_PARTIAL;
3426 th->seq = htonl(tcp_rsk(req)->snt_isn);
3427 /* XXX data is queued and acked as is. No buffer/window check */
3428 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
3429
3430 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3431 th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3432 tcp_options_write((__be32 *)(th + 1), NULL, &opts);
3433 th->doff = (tcp_header_size >> 2);
3434 __TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3435
3436#ifdef CONFIG_TCP_MD5SIG
3437 /* Okay, we have all we need - do the md5 hash if needed */
3438 if (md5)
3439 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3440 md5, req_to_sk(req), skb);
3441 rcu_read_unlock();
3442#endif
3443
3444 skb->skb_mstamp_ns = now;
3445 tcp_add_tx_delay(skb, tp);
3446
3447 return skb;
3448}
3449EXPORT_SYMBOL(tcp_make_synack);
3450
3451static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
3452{
3453 struct inet_connection_sock *icsk = inet_csk(sk);
3454 const struct tcp_congestion_ops *ca;
3455 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
3456
3457 if (ca_key == TCP_CA_UNSPEC)
3458 return;
3459
3460 rcu_read_lock();
3461 ca = tcp_ca_find_key(ca_key);
3462 if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
3463 bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
3464 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
3465 icsk->icsk_ca_ops = ca;
3466 }
3467 rcu_read_unlock();
3468}
3469
3470/* Do all connect socket setups that can be done AF independent. */
3471static void tcp_connect_init(struct sock *sk)
3472{
3473 const struct dst_entry *dst = __sk_dst_get(sk);
3474 struct tcp_sock *tp = tcp_sk(sk);
3475 __u8 rcv_wscale;
3476 u32 rcv_wnd;
3477
3478 /* We'll fix this up when we get a response from the other end.
3479 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3480 */
3481 tp->tcp_header_len = sizeof(struct tcphdr);
3482 if (sock_net(sk)->ipv4.sysctl_tcp_timestamps)
3483 tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
3484
3485#ifdef CONFIG_TCP_MD5SIG
3486 if (tp->af_specific->md5_lookup(sk, sk))
3487 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
3488#endif
3489
3490 /* If user gave his TCP_MAXSEG, record it to clamp */
3491 if (tp->rx_opt.user_mss)
3492 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3493 tp->max_window = 0;
3494 tcp_mtup_init(sk);
3495 tcp_sync_mss(sk, dst_mtu(dst));
3496
3497 tcp_ca_dst_init(sk, dst);
3498
3499 if (!tp->window_clamp)
3500 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3501 tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3502
3503 tcp_initialize_rcv_mss(sk);
3504
3505 /* limit the window selection if the user enforce a smaller rx buffer */
3506 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
3507 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
3508 tp->window_clamp = tcp_full_space(sk);
3509
3510 rcv_wnd = tcp_rwnd_init_bpf(sk);
3511 if (rcv_wnd == 0)
3512 rcv_wnd = dst_metric(dst, RTAX_INITRWND);
3513
3514 tcp_select_initial_window(sk, tcp_full_space(sk),
3515 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
3516 &tp->rcv_wnd,
3517 &tp->window_clamp,
3518 sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
3519 &rcv_wscale,
3520 rcv_wnd);
3521
3522 tp->rx_opt.rcv_wscale = rcv_wscale;
3523 tp->rcv_ssthresh = tp->rcv_wnd;
3524
3525 sk->sk_err = 0;
3526 sock_reset_flag(sk, SOCK_DONE);
3527 tp->snd_wnd = 0;
3528 tcp_init_wl(tp, 0);
3529 tcp_write_queue_purge(sk);
3530 tp->snd_una = tp->write_seq;
3531 tp->snd_sml = tp->write_seq;
3532 tp->snd_up = tp->write_seq;
3533 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3534
3535 if (likely(!tp->repair))
3536 tp->rcv_nxt = 0;
3537 else
3538 tp->rcv_tstamp = tcp_jiffies32;
3539 tp->rcv_wup = tp->rcv_nxt;
3540 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
3541
3542 inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3543 inet_csk(sk)->icsk_retransmits = 0;
3544 tcp_clear_retrans(tp);
3545}
3546
3547static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
3548{
3549 struct tcp_sock *tp = tcp_sk(sk);
3550 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
3551
3552 tcb->end_seq += skb->len;
3553 __skb_header_release(skb);
3554 sk_wmem_queued_add(sk, skb->truesize);
3555 sk_mem_charge(sk, skb->truesize);
3556 WRITE_ONCE(tp->write_seq, tcb->end_seq);
3557 tp->packets_out += tcp_skb_pcount(skb);
3558}
3559
3560/* Build and send a SYN with data and (cached) Fast Open cookie. However,
3561 * queue a data-only packet after the regular SYN, such that regular SYNs
3562 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3563 * only the SYN sequence, the data are retransmitted in the first ACK.
3564 * If cookie is not cached or other error occurs, falls back to send a
3565 * regular SYN with Fast Open cookie request option.
3566 */
3567static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
3568{
3569 struct tcp_sock *tp = tcp_sk(sk);
3570 struct tcp_fastopen_request *fo = tp->fastopen_req;
3571 int space, err = 0;
3572 struct sk_buff *syn_data;
3573
3574 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
3575 if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3576 goto fallback;
3577
3578 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3579 * user-MSS. Reserve maximum option space for middleboxes that add
3580 * private TCP options. The cost is reduced data space in SYN :(
3581 */
3582 tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
3583
3584 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3585 MAX_TCP_OPTION_SPACE;
3586
3587 space = min_t(size_t, space, fo->size);
3588
3589 /* limit to order-0 allocations */
3590 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
3591
3592 syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3593 if (!syn_data)
3594 goto fallback;
3595 syn_data->ip_summed = CHECKSUM_PARTIAL;
3596 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3597 if (space) {
3598 int copied = copy_from_iter(skb_put(syn_data, space), space,
3599 &fo->data->msg_iter);
3600 if (unlikely(!copied)) {
3601 tcp_skb_tsorted_anchor_cleanup(syn_data);
3602 kfree_skb(syn_data);
3603 goto fallback;
3604 }
3605 if (copied != space) {
3606 skb_trim(syn_data, copied);
3607 space = copied;
3608 }
3609 skb_zcopy_set(syn_data, fo->uarg, NULL);
3610 }
3611 /* No more data pending in inet_wait_for_connect() */
3612 if (space == fo->size)
3613 fo->data = NULL;
3614 fo->copied = space;
3615
3616 tcp_connect_queue_skb(sk, syn_data);
3617 if (syn_data->len)
3618 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3619
3620 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3621
3622 syn->skb_mstamp_ns = syn_data->skb_mstamp_ns;
3623
3624 /* Now full SYN+DATA was cloned and sent (or not),
3625 * remove the SYN from the original skb (syn_data)
3626 * we keep in write queue in case of a retransmit, as we
3627 * also have the SYN packet (with no data) in the same queue.
3628 */
3629 TCP_SKB_CB(syn_data)->seq++;
3630 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
3631 if (!err) {
3632 tp->syn_data = (fo->copied > 0);
3633 tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
3634 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3635 goto done;
3636 }
3637
3638 /* data was not sent, put it in write_queue */
3639 __skb_queue_tail(&sk->sk_write_queue, syn_data);
3640 tp->packets_out -= tcp_skb_pcount(syn_data);
3641
3642fallback:
3643 /* Send a regular SYN with Fast Open cookie request option */
3644 if (fo->cookie.len > 0)
3645 fo->cookie.len = 0;
3646 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3647 if (err)
3648 tp->syn_fastopen = 0;
3649done:
3650 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3651 return err;
3652}
3653
3654/* Build a SYN and send it off. */
3655int tcp_connect(struct sock *sk)
3656{
3657 struct tcp_sock *tp = tcp_sk(sk);
3658 struct sk_buff *buff;
3659 int err;
3660
3661 tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
3662
3663 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3664 return -EHOSTUNREACH; /* Routing failure or similar. */
3665
3666 tcp_connect_init(sk);
3667
3668 if (unlikely(tp->repair)) {
3669 tcp_finish_connect(sk, NULL);
3670 return 0;
3671 }
3672
3673 buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3674 if (unlikely(!buff))
3675 return -ENOBUFS;
3676
3677 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3678 tcp_mstamp_refresh(tp);
3679 tp->retrans_stamp = tcp_time_stamp(tp);
3680 tcp_connect_queue_skb(sk, buff);
3681 tcp_ecn_send_syn(sk, buff);
3682 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
3683
3684 /* Send off SYN; include data in Fast Open. */
3685 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3686 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3687 if (err == -ECONNREFUSED)
3688 return err;
3689
3690 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3691 * in order to make this packet get counted in tcpOutSegs.
3692 */
3693 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3694 tp->pushed_seq = tp->write_seq;
3695 buff = tcp_send_head(sk);
3696 if (unlikely(buff)) {
3697 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq);
3698 tp->pushed_seq = TCP_SKB_CB(buff)->seq;
3699 }
3700 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3701
3702 /* Timer for repeating the SYN until an answer. */
3703 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3704 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3705 return 0;
3706}
3707EXPORT_SYMBOL(tcp_connect);
3708
3709/* Send out a delayed ack, the caller does the policy checking
3710 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3711 * for details.
3712 */
3713void tcp_send_delayed_ack(struct sock *sk)
3714{
3715 struct inet_connection_sock *icsk = inet_csk(sk);
3716 int ato = icsk->icsk_ack.ato;
3717 unsigned long timeout;
3718
3719 if (ato > TCP_DELACK_MIN) {
3720 const struct tcp_sock *tp = tcp_sk(sk);
3721 int max_ato = HZ / 2;
3722
3723 if (inet_csk_in_pingpong_mode(sk) ||
3724 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3725 max_ato = TCP_DELACK_MAX;
3726
3727 /* Slow path, intersegment interval is "high". */
3728
3729 /* If some rtt estimate is known, use it to bound delayed ack.
3730 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3731 * directly.
3732 */
3733 if (tp->srtt_us) {
3734 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3735 TCP_DELACK_MIN);
3736
3737 if (rtt < max_ato)
3738 max_ato = rtt;
3739 }
3740
3741 ato = min(ato, max_ato);
3742 }
3743
3744 /* Stay within the limit we were given */
3745 timeout = jiffies + ato;
3746
3747 /* Use new timeout only if there wasn't a older one earlier. */
3748 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3749 /* If delack timer was blocked or is about to expire,
3750 * send ACK now.
3751 */
3752 if (icsk->icsk_ack.blocked ||
3753 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3754 tcp_send_ack(sk);
3755 return;
3756 }
3757
3758 if (!time_before(timeout, icsk->icsk_ack.timeout))
3759 timeout = icsk->icsk_ack.timeout;
3760 }
3761 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3762 icsk->icsk_ack.timeout = timeout;
3763 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3764}
3765
3766/* This routine sends an ack and also updates the window. */
3767void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
3768{
3769 struct sk_buff *buff;
3770
3771 /* If we have been reset, we may not send again. */
3772 if (sk->sk_state == TCP_CLOSE)
3773 return;
3774
3775 /* We are not putting this on the write queue, so
3776 * tcp_transmit_skb() will set the ownership to this
3777 * sock.
3778 */
3779 buff = alloc_skb(MAX_TCP_HEADER,
3780 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3781 if (unlikely(!buff)) {
3782 inet_csk_schedule_ack(sk);
3783 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
3784 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
3785 TCP_DELACK_MAX, TCP_RTO_MAX);
3786 return;
3787 }
3788
3789 /* Reserve space for headers and prepare control bits. */
3790 skb_reserve(buff, MAX_TCP_HEADER);
3791 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3792
3793 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
3794 * too much.
3795 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
3796 */
3797 skb_set_tcp_pure_ack(buff);
3798
3799 /* Send it off, this clears delayed acks for us. */
3800 __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
3801}
3802EXPORT_SYMBOL_GPL(__tcp_send_ack);
3803
3804void tcp_send_ack(struct sock *sk)
3805{
3806 __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
3807}
3808
3809/* This routine sends a packet with an out of date sequence
3810 * number. It assumes the other end will try to ack it.
3811 *
3812 * Question: what should we make while urgent mode?
3813 * 4.4BSD forces sending single byte of data. We cannot send
3814 * out of window data, because we have SND.NXT==SND.MAX...
3815 *
3816 * Current solution: to send TWO zero-length segments in urgent mode:
3817 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3818 * out-of-date with SND.UNA-1 to probe window.
3819 */
3820static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
3821{
3822 struct tcp_sock *tp = tcp_sk(sk);
3823 struct sk_buff *skb;
3824
3825 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3826 skb = alloc_skb(MAX_TCP_HEADER,
3827 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3828 if (!skb)
3829 return -1;
3830
3831 /* Reserve space for headers and set control bits. */
3832 skb_reserve(skb, MAX_TCP_HEADER);
3833 /* Use a previous sequence. This should cause the other
3834 * end to send an ack. Don't queue or clone SKB, just
3835 * send it.
3836 */
3837 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3838 NET_INC_STATS(sock_net(sk), mib);
3839 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
3840}
3841
3842/* Called from setsockopt( ... TCP_REPAIR ) */
3843void tcp_send_window_probe(struct sock *sk)
3844{
3845 if (sk->sk_state == TCP_ESTABLISHED) {
3846 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3847 tcp_mstamp_refresh(tcp_sk(sk));
3848 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
3849 }
3850}
3851
3852/* Initiate keepalive or window probe from timer. */
3853int tcp_write_wakeup(struct sock *sk, int mib)
3854{
3855 struct tcp_sock *tp = tcp_sk(sk);
3856 struct sk_buff *skb;
3857
3858 if (sk->sk_state == TCP_CLOSE)
3859 return -1;
3860
3861 skb = tcp_send_head(sk);
3862 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3863 int err;
3864 unsigned int mss = tcp_current_mss(sk);
3865 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3866
3867 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
3868 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
3869
3870 /* We are probing the opening of a window
3871 * but the window size is != 0
3872 * must have been a result SWS avoidance ( sender )
3873 */
3874 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
3875 skb->len > mss) {
3876 seg_size = min(seg_size, mss);
3877 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3878 if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
3879 skb, seg_size, mss, GFP_ATOMIC))
3880 return -1;
3881 } else if (!tcp_skb_pcount(skb))
3882 tcp_set_skb_tso_segs(skb, mss);
3883
3884 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3885 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3886 if (!err)
3887 tcp_event_new_data_sent(sk, skb);
3888 return err;
3889 } else {
3890 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3891 tcp_xmit_probe_skb(sk, 1, mib);
3892 return tcp_xmit_probe_skb(sk, 0, mib);
3893 }
3894}
3895
3896/* A window probe timeout has occurred. If window is not closed send
3897 * a partial packet else a zero probe.
3898 */
3899void tcp_send_probe0(struct sock *sk)
3900{
3901 struct inet_connection_sock *icsk = inet_csk(sk);
3902 struct tcp_sock *tp = tcp_sk(sk);
3903 struct net *net = sock_net(sk);
3904 unsigned long timeout;
3905 int err;
3906
3907 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
3908
3909 if (tp->packets_out || tcp_write_queue_empty(sk)) {
3910 /* Cancel probe timer, if it is not required. */
3911 icsk->icsk_probes_out = 0;
3912 icsk->icsk_backoff = 0;
3913 return;
3914 }
3915
3916 icsk->icsk_probes_out++;
3917 if (err <= 0) {
3918 if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3919 icsk->icsk_backoff++;
3920 timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
3921 } else {
3922 /* If packet was not sent due to local congestion,
3923 * Let senders fight for local resources conservatively.
3924 */
3925 timeout = TCP_RESOURCE_PROBE_INTERVAL;
3926 }
3927 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX);
3928}
3929
3930int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3931{
3932 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
3933 struct flowi fl;
3934 int res;
3935
3936 tcp_rsk(req)->txhash = net_tx_rndhash();
3937 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3938 if (!res) {
3939 __TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3940 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3941 if (unlikely(tcp_passive_fastopen(sk)))
3942 tcp_sk(sk)->total_retrans++;
3943 trace_tcp_retransmit_synack(sk, req);
3944 }
3945 return res;
3946}
3947EXPORT_SYMBOL(tcp_rtx_synack);
1// SPDX-License-Identifier: GPL-2.0-only
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: Pedro Roque : Retransmit queue handled by TCP.
24 * : Fragmentation on mtu decrease
25 * : Segment collapse on retransmit
26 * : AF independence
27 *
28 * Linus Torvalds : send_delayed_ack
29 * David S. Miller : Charge memory using the right skb
30 * during syn/ack processing.
31 * David S. Miller : Output engine completely rewritten.
32 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
33 * Cacophonix Gaul : draft-minshall-nagle-01
34 * J Hadi Salim : ECN support
35 *
36 */
37
38#define pr_fmt(fmt) "TCP: " fmt
39
40#include <net/tcp.h>
41#include <net/mptcp.h>
42
43#include <linux/compiler.h>
44#include <linux/gfp.h>
45#include <linux/module.h>
46#include <linux/static_key.h>
47
48#include <trace/events/tcp.h>
49
50/* Refresh clocks of a TCP socket,
51 * ensuring monotically increasing values.
52 */
53void tcp_mstamp_refresh(struct tcp_sock *tp)
54{
55 u64 val = tcp_clock_ns();
56
57 tp->tcp_clock_cache = val;
58 tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
59}
60
61static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
62 int push_one, gfp_t gfp);
63
64/* Account for new data that has been sent to the network. */
65static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
66{
67 struct inet_connection_sock *icsk = inet_csk(sk);
68 struct tcp_sock *tp = tcp_sk(sk);
69 unsigned int prior_packets = tp->packets_out;
70
71 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
72
73 __skb_unlink(skb, &sk->sk_write_queue);
74 tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
75
76 if (tp->highest_sack == NULL)
77 tp->highest_sack = skb;
78
79 tp->packets_out += tcp_skb_pcount(skb);
80 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
81 tcp_rearm_rto(sk);
82
83 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
84 tcp_skb_pcount(skb));
85 tcp_check_space(sk);
86}
87
88/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
89 * window scaling factor due to loss of precision.
90 * If window has been shrunk, what should we make? It is not clear at all.
91 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
92 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
93 * invalid. OK, let's make this for now:
94 */
95static inline __u32 tcp_acceptable_seq(const struct sock *sk)
96{
97 const struct tcp_sock *tp = tcp_sk(sk);
98
99 if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
100 (tp->rx_opt.wscale_ok &&
101 ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
102 return tp->snd_nxt;
103 else
104 return tcp_wnd_end(tp);
105}
106
107/* Calculate mss to advertise in SYN segment.
108 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
109 *
110 * 1. It is independent of path mtu.
111 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
112 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
113 * attached devices, because some buggy hosts are confused by
114 * large MSS.
115 * 4. We do not make 3, we advertise MSS, calculated from first
116 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
117 * This may be overridden via information stored in routing table.
118 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
119 * probably even Jumbo".
120 */
121static __u16 tcp_advertise_mss(struct sock *sk)
122{
123 struct tcp_sock *tp = tcp_sk(sk);
124 const struct dst_entry *dst = __sk_dst_get(sk);
125 int mss = tp->advmss;
126
127 if (dst) {
128 unsigned int metric = dst_metric_advmss(dst);
129
130 if (metric < mss) {
131 mss = metric;
132 tp->advmss = mss;
133 }
134 }
135
136 return (__u16)mss;
137}
138
139/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
140 * This is the first part of cwnd validation mechanism.
141 */
142void tcp_cwnd_restart(struct sock *sk, s32 delta)
143{
144 struct tcp_sock *tp = tcp_sk(sk);
145 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
146 u32 cwnd = tcp_snd_cwnd(tp);
147
148 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
149
150 tp->snd_ssthresh = tcp_current_ssthresh(sk);
151 restart_cwnd = min(restart_cwnd, cwnd);
152
153 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
154 cwnd >>= 1;
155 tcp_snd_cwnd_set(tp, max(cwnd, restart_cwnd));
156 tp->snd_cwnd_stamp = tcp_jiffies32;
157 tp->snd_cwnd_used = 0;
158}
159
160/* Congestion state accounting after a packet has been sent. */
161static void tcp_event_data_sent(struct tcp_sock *tp,
162 struct sock *sk)
163{
164 struct inet_connection_sock *icsk = inet_csk(sk);
165 const u32 now = tcp_jiffies32;
166
167 if (tcp_packets_in_flight(tp) == 0)
168 tcp_ca_event(sk, CA_EVENT_TX_START);
169
170 tp->lsndtime = now;
171
172 /* If it is a reply for ato after last received
173 * packet, increase pingpong count.
174 */
175 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
176 inet_csk_inc_pingpong_cnt(sk);
177}
178
179/* Account for an ACK we sent. */
180static inline void tcp_event_ack_sent(struct sock *sk, u32 rcv_nxt)
181{
182 struct tcp_sock *tp = tcp_sk(sk);
183
184 if (unlikely(tp->compressed_ack)) {
185 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
186 tp->compressed_ack);
187 tp->compressed_ack = 0;
188 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
189 __sock_put(sk);
190 }
191
192 if (unlikely(rcv_nxt != tp->rcv_nxt))
193 return; /* Special ACK sent by DCTCP to reflect ECN */
194 tcp_dec_quickack_mode(sk);
195 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
196}
197
198/* Determine a window scaling and initial window to offer.
199 * Based on the assumption that the given amount of space
200 * will be offered. Store the results in the tp structure.
201 * NOTE: for smooth operation initial space offering should
202 * be a multiple of mss if possible. We assume here that mss >= 1.
203 * This MUST be enforced by all callers.
204 */
205void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
206 __u32 *rcv_wnd, __u32 *window_clamp,
207 int wscale_ok, __u8 *rcv_wscale,
208 __u32 init_rcv_wnd)
209{
210 unsigned int space = (__space < 0 ? 0 : __space);
211
212 /* If no clamp set the clamp to the max possible scaled window */
213 if (*window_clamp == 0)
214 (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
215 space = min(*window_clamp, space);
216
217 /* Quantize space offering to a multiple of mss if possible. */
218 if (space > mss)
219 space = rounddown(space, mss);
220
221 /* NOTE: offering an initial window larger than 32767
222 * will break some buggy TCP stacks. If the admin tells us
223 * it is likely we could be speaking with such a buggy stack
224 * we will truncate our initial window offering to 32K-1
225 * unless the remote has sent us a window scaling option,
226 * which we interpret as a sign the remote TCP is not
227 * misinterpreting the window field as a signed quantity.
228 */
229 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows))
230 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
231 else
232 (*rcv_wnd) = min_t(u32, space, U16_MAX);
233
234 if (init_rcv_wnd)
235 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
236
237 *rcv_wscale = 0;
238 if (wscale_ok) {
239 /* Set window scaling on max possible window */
240 space = max_t(u32, space, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]));
241 space = max_t(u32, space, READ_ONCE(sysctl_rmem_max));
242 space = min_t(u32, space, *window_clamp);
243 *rcv_wscale = clamp_t(int, ilog2(space) - 15,
244 0, TCP_MAX_WSCALE);
245 }
246 /* Set the clamp no higher than max representable value */
247 (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
248}
249EXPORT_SYMBOL(tcp_select_initial_window);
250
251/* Chose a new window to advertise, update state in tcp_sock for the
252 * socket, and return result with RFC1323 scaling applied. The return
253 * value can be stuffed directly into th->window for an outgoing
254 * frame.
255 */
256static u16 tcp_select_window(struct sock *sk)
257{
258 struct tcp_sock *tp = tcp_sk(sk);
259 struct net *net = sock_net(sk);
260 u32 old_win = tp->rcv_wnd;
261 u32 cur_win, new_win;
262
263 /* Make the window 0 if we failed to queue the data because we
264 * are out of memory. The window is temporary, so we don't store
265 * it on the socket.
266 */
267 if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM))
268 return 0;
269
270 cur_win = tcp_receive_window(tp);
271 new_win = __tcp_select_window(sk);
272 if (new_win < cur_win) {
273 /* Danger Will Robinson!
274 * Don't update rcv_wup/rcv_wnd here or else
275 * we will not be able to advertise a zero
276 * window in time. --DaveM
277 *
278 * Relax Will Robinson.
279 */
280 if (!READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) || !tp->rx_opt.rcv_wscale) {
281 /* Never shrink the offered window */
282 if (new_win == 0)
283 NET_INC_STATS(net, LINUX_MIB_TCPWANTZEROWINDOWADV);
284 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
285 }
286 }
287
288 tp->rcv_wnd = new_win;
289 tp->rcv_wup = tp->rcv_nxt;
290
291 /* Make sure we do not exceed the maximum possible
292 * scaled window.
293 */
294 if (!tp->rx_opt.rcv_wscale &&
295 READ_ONCE(net->ipv4.sysctl_tcp_workaround_signed_windows))
296 new_win = min(new_win, MAX_TCP_WINDOW);
297 else
298 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
299
300 /* RFC1323 scaling applied */
301 new_win >>= tp->rx_opt.rcv_wscale;
302
303 /* If we advertise zero window, disable fast path. */
304 if (new_win == 0) {
305 tp->pred_flags = 0;
306 if (old_win)
307 NET_INC_STATS(net, LINUX_MIB_TCPTOZEROWINDOWADV);
308 } else if (old_win == 0) {
309 NET_INC_STATS(net, LINUX_MIB_TCPFROMZEROWINDOWADV);
310 }
311
312 return new_win;
313}
314
315/* Packet ECN state for a SYN-ACK */
316static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
317{
318 const struct tcp_sock *tp = tcp_sk(sk);
319
320 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
321 if (!(tp->ecn_flags & TCP_ECN_OK))
322 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
323 else if (tcp_ca_needs_ecn(sk) ||
324 tcp_bpf_ca_needs_ecn(sk))
325 INET_ECN_xmit(sk);
326}
327
328/* Packet ECN state for a SYN. */
329static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
330{
331 struct tcp_sock *tp = tcp_sk(sk);
332 bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
333 bool use_ecn = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn) == 1 ||
334 tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
335
336 if (!use_ecn) {
337 const struct dst_entry *dst = __sk_dst_get(sk);
338
339 if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
340 use_ecn = true;
341 }
342
343 tp->ecn_flags = 0;
344
345 if (use_ecn) {
346 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
347 tp->ecn_flags = TCP_ECN_OK;
348 if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
349 INET_ECN_xmit(sk);
350 }
351}
352
353static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
354{
355 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback))
356 /* tp->ecn_flags are cleared at a later point in time when
357 * SYN ACK is ultimatively being received.
358 */
359 TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
360}
361
362static void
363tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
364{
365 if (inet_rsk(req)->ecn_ok)
366 th->ece = 1;
367}
368
369/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
370 * be sent.
371 */
372static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
373 struct tcphdr *th, int tcp_header_len)
374{
375 struct tcp_sock *tp = tcp_sk(sk);
376
377 if (tp->ecn_flags & TCP_ECN_OK) {
378 /* Not-retransmitted data segment: set ECT and inject CWR. */
379 if (skb->len != tcp_header_len &&
380 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
381 INET_ECN_xmit(sk);
382 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
383 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
384 th->cwr = 1;
385 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
386 }
387 } else if (!tcp_ca_needs_ecn(sk)) {
388 /* ACK or retransmitted segment: clear ECT|CE */
389 INET_ECN_dontxmit(sk);
390 }
391 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
392 th->ece = 1;
393 }
394}
395
396/* Constructs common control bits of non-data skb. If SYN/FIN is present,
397 * auto increment end seqno.
398 */
399static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
400{
401 skb->ip_summed = CHECKSUM_PARTIAL;
402
403 TCP_SKB_CB(skb)->tcp_flags = flags;
404
405 tcp_skb_pcount_set(skb, 1);
406
407 TCP_SKB_CB(skb)->seq = seq;
408 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
409 seq++;
410 TCP_SKB_CB(skb)->end_seq = seq;
411}
412
413static inline bool tcp_urg_mode(const struct tcp_sock *tp)
414{
415 return tp->snd_una != tp->snd_up;
416}
417
418#define OPTION_SACK_ADVERTISE BIT(0)
419#define OPTION_TS BIT(1)
420#define OPTION_MD5 BIT(2)
421#define OPTION_WSCALE BIT(3)
422#define OPTION_FAST_OPEN_COOKIE BIT(8)
423#define OPTION_SMC BIT(9)
424#define OPTION_MPTCP BIT(10)
425#define OPTION_AO BIT(11)
426
427static void smc_options_write(__be32 *ptr, u16 *options)
428{
429#if IS_ENABLED(CONFIG_SMC)
430 if (static_branch_unlikely(&tcp_have_smc)) {
431 if (unlikely(OPTION_SMC & *options)) {
432 *ptr++ = htonl((TCPOPT_NOP << 24) |
433 (TCPOPT_NOP << 16) |
434 (TCPOPT_EXP << 8) |
435 (TCPOLEN_EXP_SMC_BASE));
436 *ptr++ = htonl(TCPOPT_SMC_MAGIC);
437 }
438 }
439#endif
440}
441
442struct tcp_out_options {
443 u16 options; /* bit field of OPTION_* */
444 u16 mss; /* 0 to disable */
445 u8 ws; /* window scale, 0 to disable */
446 u8 num_sack_blocks; /* number of SACK blocks to include */
447 u8 hash_size; /* bytes in hash_location */
448 u8 bpf_opt_len; /* length of BPF hdr option */
449 __u8 *hash_location; /* temporary pointer, overloaded */
450 __u32 tsval, tsecr; /* need to include OPTION_TS */
451 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
452 struct mptcp_out_options mptcp;
453};
454
455static void mptcp_options_write(struct tcphdr *th, __be32 *ptr,
456 struct tcp_sock *tp,
457 struct tcp_out_options *opts)
458{
459#if IS_ENABLED(CONFIG_MPTCP)
460 if (unlikely(OPTION_MPTCP & opts->options))
461 mptcp_write_options(th, ptr, tp, &opts->mptcp);
462#endif
463}
464
465#ifdef CONFIG_CGROUP_BPF
466static int bpf_skops_write_hdr_opt_arg0(struct sk_buff *skb,
467 enum tcp_synack_type synack_type)
468{
469 if (unlikely(!skb))
470 return BPF_WRITE_HDR_TCP_CURRENT_MSS;
471
472 if (unlikely(synack_type == TCP_SYNACK_COOKIE))
473 return BPF_WRITE_HDR_TCP_SYNACK_COOKIE;
474
475 return 0;
476}
477
478/* req, syn_skb and synack_type are used when writing synack */
479static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
480 struct request_sock *req,
481 struct sk_buff *syn_skb,
482 enum tcp_synack_type synack_type,
483 struct tcp_out_options *opts,
484 unsigned int *remaining)
485{
486 struct bpf_sock_ops_kern sock_ops;
487 int err;
488
489 if (likely(!BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk),
490 BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG)) ||
491 !*remaining)
492 return;
493
494 /* *remaining has already been aligned to 4 bytes, so *remaining >= 4 */
495
496 /* init sock_ops */
497 memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
498
499 sock_ops.op = BPF_SOCK_OPS_HDR_OPT_LEN_CB;
500
501 if (req) {
502 /* The listen "sk" cannot be passed here because
503 * it is not locked. It would not make too much
504 * sense to do bpf_setsockopt(listen_sk) based
505 * on individual connection request also.
506 *
507 * Thus, "req" is passed here and the cgroup-bpf-progs
508 * of the listen "sk" will be run.
509 *
510 * "req" is also used here for fastopen even the "sk" here is
511 * a fullsock "child" sk. It is to keep the behavior
512 * consistent between fastopen and non-fastopen on
513 * the bpf programming side.
514 */
515 sock_ops.sk = (struct sock *)req;
516 sock_ops.syn_skb = syn_skb;
517 } else {
518 sock_owned_by_me(sk);
519
520 sock_ops.is_fullsock = 1;
521 sock_ops.sk = sk;
522 }
523
524 sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
525 sock_ops.remaining_opt_len = *remaining;
526 /* tcp_current_mss() does not pass a skb */
527 if (skb)
528 bpf_skops_init_skb(&sock_ops, skb, 0);
529
530 err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
531
532 if (err || sock_ops.remaining_opt_len == *remaining)
533 return;
534
535 opts->bpf_opt_len = *remaining - sock_ops.remaining_opt_len;
536 /* round up to 4 bytes */
537 opts->bpf_opt_len = (opts->bpf_opt_len + 3) & ~3;
538
539 *remaining -= opts->bpf_opt_len;
540}
541
542static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
543 struct request_sock *req,
544 struct sk_buff *syn_skb,
545 enum tcp_synack_type synack_type,
546 struct tcp_out_options *opts)
547{
548 u8 first_opt_off, nr_written, max_opt_len = opts->bpf_opt_len;
549 struct bpf_sock_ops_kern sock_ops;
550 int err;
551
552 if (likely(!max_opt_len))
553 return;
554
555 memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
556
557 sock_ops.op = BPF_SOCK_OPS_WRITE_HDR_OPT_CB;
558
559 if (req) {
560 sock_ops.sk = (struct sock *)req;
561 sock_ops.syn_skb = syn_skb;
562 } else {
563 sock_owned_by_me(sk);
564
565 sock_ops.is_fullsock = 1;
566 sock_ops.sk = sk;
567 }
568
569 sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
570 sock_ops.remaining_opt_len = max_opt_len;
571 first_opt_off = tcp_hdrlen(skb) - max_opt_len;
572 bpf_skops_init_skb(&sock_ops, skb, first_opt_off);
573
574 err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
575
576 if (err)
577 nr_written = 0;
578 else
579 nr_written = max_opt_len - sock_ops.remaining_opt_len;
580
581 if (nr_written < max_opt_len)
582 memset(skb->data + first_opt_off + nr_written, TCPOPT_NOP,
583 max_opt_len - nr_written);
584}
585#else
586static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
587 struct request_sock *req,
588 struct sk_buff *syn_skb,
589 enum tcp_synack_type synack_type,
590 struct tcp_out_options *opts,
591 unsigned int *remaining)
592{
593}
594
595static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
596 struct request_sock *req,
597 struct sk_buff *syn_skb,
598 enum tcp_synack_type synack_type,
599 struct tcp_out_options *opts)
600{
601}
602#endif
603
604static __be32 *process_tcp_ao_options(struct tcp_sock *tp,
605 const struct tcp_request_sock *tcprsk,
606 struct tcp_out_options *opts,
607 struct tcp_key *key, __be32 *ptr)
608{
609#ifdef CONFIG_TCP_AO
610 u8 maclen = tcp_ao_maclen(key->ao_key);
611
612 if (tcprsk) {
613 u8 aolen = maclen + sizeof(struct tcp_ao_hdr);
614
615 *ptr++ = htonl((TCPOPT_AO << 24) | (aolen << 16) |
616 (tcprsk->ao_keyid << 8) |
617 (tcprsk->ao_rcv_next));
618 } else {
619 struct tcp_ao_key *rnext_key;
620 struct tcp_ao_info *ao_info;
621
622 ao_info = rcu_dereference_check(tp->ao_info,
623 lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk));
624 rnext_key = READ_ONCE(ao_info->rnext_key);
625 if (WARN_ON_ONCE(!rnext_key))
626 return ptr;
627 *ptr++ = htonl((TCPOPT_AO << 24) |
628 (tcp_ao_len(key->ao_key) << 16) |
629 (key->ao_key->sndid << 8) |
630 (rnext_key->rcvid));
631 }
632 opts->hash_location = (__u8 *)ptr;
633 ptr += maclen / sizeof(*ptr);
634 if (unlikely(maclen % sizeof(*ptr))) {
635 memset(ptr, TCPOPT_NOP, sizeof(*ptr));
636 ptr++;
637 }
638#endif
639 return ptr;
640}
641
642/* Write previously computed TCP options to the packet.
643 *
644 * Beware: Something in the Internet is very sensitive to the ordering of
645 * TCP options, we learned this through the hard way, so be careful here.
646 * Luckily we can at least blame others for their non-compliance but from
647 * inter-operability perspective it seems that we're somewhat stuck with
648 * the ordering which we have been using if we want to keep working with
649 * those broken things (not that it currently hurts anybody as there isn't
650 * particular reason why the ordering would need to be changed).
651 *
652 * At least SACK_PERM as the first option is known to lead to a disaster
653 * (but it may well be that other scenarios fail similarly).
654 */
655static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
656 const struct tcp_request_sock *tcprsk,
657 struct tcp_out_options *opts,
658 struct tcp_key *key)
659{
660 __be32 *ptr = (__be32 *)(th + 1);
661 u16 options = opts->options; /* mungable copy */
662
663 if (tcp_key_is_md5(key)) {
664 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
665 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
666 /* overload cookie hash location */
667 opts->hash_location = (__u8 *)ptr;
668 ptr += 4;
669 } else if (tcp_key_is_ao(key)) {
670 ptr = process_tcp_ao_options(tp, tcprsk, opts, key, ptr);
671 }
672 if (unlikely(opts->mss)) {
673 *ptr++ = htonl((TCPOPT_MSS << 24) |
674 (TCPOLEN_MSS << 16) |
675 opts->mss);
676 }
677
678 if (likely(OPTION_TS & options)) {
679 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
680 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
681 (TCPOLEN_SACK_PERM << 16) |
682 (TCPOPT_TIMESTAMP << 8) |
683 TCPOLEN_TIMESTAMP);
684 options &= ~OPTION_SACK_ADVERTISE;
685 } else {
686 *ptr++ = htonl((TCPOPT_NOP << 24) |
687 (TCPOPT_NOP << 16) |
688 (TCPOPT_TIMESTAMP << 8) |
689 TCPOLEN_TIMESTAMP);
690 }
691 *ptr++ = htonl(opts->tsval);
692 *ptr++ = htonl(opts->tsecr);
693 }
694
695 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
696 *ptr++ = htonl((TCPOPT_NOP << 24) |
697 (TCPOPT_NOP << 16) |
698 (TCPOPT_SACK_PERM << 8) |
699 TCPOLEN_SACK_PERM);
700 }
701
702 if (unlikely(OPTION_WSCALE & options)) {
703 *ptr++ = htonl((TCPOPT_NOP << 24) |
704 (TCPOPT_WINDOW << 16) |
705 (TCPOLEN_WINDOW << 8) |
706 opts->ws);
707 }
708
709 if (unlikely(opts->num_sack_blocks)) {
710 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
711 tp->duplicate_sack : tp->selective_acks;
712 int this_sack;
713
714 *ptr++ = htonl((TCPOPT_NOP << 24) |
715 (TCPOPT_NOP << 16) |
716 (TCPOPT_SACK << 8) |
717 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
718 TCPOLEN_SACK_PERBLOCK)));
719
720 for (this_sack = 0; this_sack < opts->num_sack_blocks;
721 ++this_sack) {
722 *ptr++ = htonl(sp[this_sack].start_seq);
723 *ptr++ = htonl(sp[this_sack].end_seq);
724 }
725
726 tp->rx_opt.dsack = 0;
727 }
728
729 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
730 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
731 u8 *p = (u8 *)ptr;
732 u32 len; /* Fast Open option length */
733
734 if (foc->exp) {
735 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
736 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
737 TCPOPT_FASTOPEN_MAGIC);
738 p += TCPOLEN_EXP_FASTOPEN_BASE;
739 } else {
740 len = TCPOLEN_FASTOPEN_BASE + foc->len;
741 *p++ = TCPOPT_FASTOPEN;
742 *p++ = len;
743 }
744
745 memcpy(p, foc->val, foc->len);
746 if ((len & 3) == 2) {
747 p[foc->len] = TCPOPT_NOP;
748 p[foc->len + 1] = TCPOPT_NOP;
749 }
750 ptr += (len + 3) >> 2;
751 }
752
753 smc_options_write(ptr, &options);
754
755 mptcp_options_write(th, ptr, tp, opts);
756}
757
758static void smc_set_option(const struct tcp_sock *tp,
759 struct tcp_out_options *opts,
760 unsigned int *remaining)
761{
762#if IS_ENABLED(CONFIG_SMC)
763 if (static_branch_unlikely(&tcp_have_smc)) {
764 if (tp->syn_smc) {
765 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
766 opts->options |= OPTION_SMC;
767 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
768 }
769 }
770 }
771#endif
772}
773
774static void smc_set_option_cond(const struct tcp_sock *tp,
775 const struct inet_request_sock *ireq,
776 struct tcp_out_options *opts,
777 unsigned int *remaining)
778{
779#if IS_ENABLED(CONFIG_SMC)
780 if (static_branch_unlikely(&tcp_have_smc)) {
781 if (tp->syn_smc && ireq->smc_ok) {
782 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
783 opts->options |= OPTION_SMC;
784 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
785 }
786 }
787 }
788#endif
789}
790
791static void mptcp_set_option_cond(const struct request_sock *req,
792 struct tcp_out_options *opts,
793 unsigned int *remaining)
794{
795 if (rsk_is_mptcp(req)) {
796 unsigned int size;
797
798 if (mptcp_synack_options(req, &size, &opts->mptcp)) {
799 if (*remaining >= size) {
800 opts->options |= OPTION_MPTCP;
801 *remaining -= size;
802 }
803 }
804 }
805}
806
807/* Compute TCP options for SYN packets. This is not the final
808 * network wire format yet.
809 */
810static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
811 struct tcp_out_options *opts,
812 struct tcp_key *key)
813{
814 struct tcp_sock *tp = tcp_sk(sk);
815 unsigned int remaining = MAX_TCP_OPTION_SPACE;
816 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
817 bool timestamps;
818
819 /* Better than switch (key.type) as it has static branches */
820 if (tcp_key_is_md5(key)) {
821 timestamps = false;
822 opts->options |= OPTION_MD5;
823 remaining -= TCPOLEN_MD5SIG_ALIGNED;
824 } else {
825 timestamps = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps);
826 if (tcp_key_is_ao(key)) {
827 opts->options |= OPTION_AO;
828 remaining -= tcp_ao_len_aligned(key->ao_key);
829 }
830 }
831
832 /* We always get an MSS option. The option bytes which will be seen in
833 * normal data packets should timestamps be used, must be in the MSS
834 * advertised. But we subtract them from tp->mss_cache so that
835 * calculations in tcp_sendmsg are simpler etc. So account for this
836 * fact here if necessary. If we don't do this correctly, as a
837 * receiver we won't recognize data packets as being full sized when we
838 * should, and thus we won't abide by the delayed ACK rules correctly.
839 * SACKs don't matter, we never delay an ACK when we have any of those
840 * going out. */
841 opts->mss = tcp_advertise_mss(sk);
842 remaining -= TCPOLEN_MSS_ALIGNED;
843
844 if (likely(timestamps)) {
845 opts->options |= OPTION_TS;
846 opts->tsval = tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb) + tp->tsoffset;
847 opts->tsecr = tp->rx_opt.ts_recent;
848 remaining -= TCPOLEN_TSTAMP_ALIGNED;
849 }
850 if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_window_scaling))) {
851 opts->ws = tp->rx_opt.rcv_wscale;
852 opts->options |= OPTION_WSCALE;
853 remaining -= TCPOLEN_WSCALE_ALIGNED;
854 }
855 if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_sack))) {
856 opts->options |= OPTION_SACK_ADVERTISE;
857 if (unlikely(!(OPTION_TS & opts->options)))
858 remaining -= TCPOLEN_SACKPERM_ALIGNED;
859 }
860
861 if (fastopen && fastopen->cookie.len >= 0) {
862 u32 need = fastopen->cookie.len;
863
864 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
865 TCPOLEN_FASTOPEN_BASE;
866 need = (need + 3) & ~3U; /* Align to 32 bits */
867 if (remaining >= need) {
868 opts->options |= OPTION_FAST_OPEN_COOKIE;
869 opts->fastopen_cookie = &fastopen->cookie;
870 remaining -= need;
871 tp->syn_fastopen = 1;
872 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
873 }
874 }
875
876 smc_set_option(tp, opts, &remaining);
877
878 if (sk_is_mptcp(sk)) {
879 unsigned int size;
880
881 if (mptcp_syn_options(sk, skb, &size, &opts->mptcp)) {
882 opts->options |= OPTION_MPTCP;
883 remaining -= size;
884 }
885 }
886
887 bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
888
889 return MAX_TCP_OPTION_SPACE - remaining;
890}
891
892/* Set up TCP options for SYN-ACKs. */
893static unsigned int tcp_synack_options(const struct sock *sk,
894 struct request_sock *req,
895 unsigned int mss, struct sk_buff *skb,
896 struct tcp_out_options *opts,
897 const struct tcp_key *key,
898 struct tcp_fastopen_cookie *foc,
899 enum tcp_synack_type synack_type,
900 struct sk_buff *syn_skb)
901{
902 struct inet_request_sock *ireq = inet_rsk(req);
903 unsigned int remaining = MAX_TCP_OPTION_SPACE;
904
905 if (tcp_key_is_md5(key)) {
906 opts->options |= OPTION_MD5;
907 remaining -= TCPOLEN_MD5SIG_ALIGNED;
908
909 /* We can't fit any SACK blocks in a packet with MD5 + TS
910 * options. There was discussion about disabling SACK
911 * rather than TS in order to fit in better with old,
912 * buggy kernels, but that was deemed to be unnecessary.
913 */
914 if (synack_type != TCP_SYNACK_COOKIE)
915 ireq->tstamp_ok &= !ireq->sack_ok;
916 } else if (tcp_key_is_ao(key)) {
917 opts->options |= OPTION_AO;
918 remaining -= tcp_ao_len_aligned(key->ao_key);
919 ireq->tstamp_ok &= !ireq->sack_ok;
920 }
921
922 /* We always send an MSS option. */
923 opts->mss = mss;
924 remaining -= TCPOLEN_MSS_ALIGNED;
925
926 if (likely(ireq->wscale_ok)) {
927 opts->ws = ireq->rcv_wscale;
928 opts->options |= OPTION_WSCALE;
929 remaining -= TCPOLEN_WSCALE_ALIGNED;
930 }
931 if (likely(ireq->tstamp_ok)) {
932 opts->options |= OPTION_TS;
933 opts->tsval = tcp_skb_timestamp_ts(tcp_rsk(req)->req_usec_ts, skb) +
934 tcp_rsk(req)->ts_off;
935 opts->tsecr = READ_ONCE(req->ts_recent);
936 remaining -= TCPOLEN_TSTAMP_ALIGNED;
937 }
938 if (likely(ireq->sack_ok)) {
939 opts->options |= OPTION_SACK_ADVERTISE;
940 if (unlikely(!ireq->tstamp_ok))
941 remaining -= TCPOLEN_SACKPERM_ALIGNED;
942 }
943 if (foc != NULL && foc->len >= 0) {
944 u32 need = foc->len;
945
946 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
947 TCPOLEN_FASTOPEN_BASE;
948 need = (need + 3) & ~3U; /* Align to 32 bits */
949 if (remaining >= need) {
950 opts->options |= OPTION_FAST_OPEN_COOKIE;
951 opts->fastopen_cookie = foc;
952 remaining -= need;
953 }
954 }
955
956 mptcp_set_option_cond(req, opts, &remaining);
957
958 smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
959
960 bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb,
961 synack_type, opts, &remaining);
962
963 return MAX_TCP_OPTION_SPACE - remaining;
964}
965
966/* Compute TCP options for ESTABLISHED sockets. This is not the
967 * final wire format yet.
968 */
969static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
970 struct tcp_out_options *opts,
971 struct tcp_key *key)
972{
973 struct tcp_sock *tp = tcp_sk(sk);
974 unsigned int size = 0;
975 unsigned int eff_sacks;
976
977 opts->options = 0;
978
979 /* Better than switch (key.type) as it has static branches */
980 if (tcp_key_is_md5(key)) {
981 opts->options |= OPTION_MD5;
982 size += TCPOLEN_MD5SIG_ALIGNED;
983 } else if (tcp_key_is_ao(key)) {
984 opts->options |= OPTION_AO;
985 size += tcp_ao_len_aligned(key->ao_key);
986 }
987
988 if (likely(tp->rx_opt.tstamp_ok)) {
989 opts->options |= OPTION_TS;
990 opts->tsval = skb ? tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb) +
991 tp->tsoffset : 0;
992 opts->tsecr = tp->rx_opt.ts_recent;
993 size += TCPOLEN_TSTAMP_ALIGNED;
994 }
995
996 /* MPTCP options have precedence over SACK for the limited TCP
997 * option space because a MPTCP connection would be forced to
998 * fall back to regular TCP if a required multipath option is
999 * missing. SACK still gets a chance to use whatever space is
1000 * left.
1001 */
1002 if (sk_is_mptcp(sk)) {
1003 unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1004 unsigned int opt_size = 0;
1005
1006 if (mptcp_established_options(sk, skb, &opt_size, remaining,
1007 &opts->mptcp)) {
1008 opts->options |= OPTION_MPTCP;
1009 size += opt_size;
1010 }
1011 }
1012
1013 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
1014 if (unlikely(eff_sacks)) {
1015 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1016 if (unlikely(remaining < TCPOLEN_SACK_BASE_ALIGNED +
1017 TCPOLEN_SACK_PERBLOCK))
1018 return size;
1019
1020 opts->num_sack_blocks =
1021 min_t(unsigned int, eff_sacks,
1022 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
1023 TCPOLEN_SACK_PERBLOCK);
1024
1025 size += TCPOLEN_SACK_BASE_ALIGNED +
1026 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
1027 }
1028
1029 if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp,
1030 BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG))) {
1031 unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1032
1033 bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
1034
1035 size = MAX_TCP_OPTION_SPACE - remaining;
1036 }
1037
1038 return size;
1039}
1040
1041
1042/* TCP SMALL QUEUES (TSQ)
1043 *
1044 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
1045 * to reduce RTT and bufferbloat.
1046 * We do this using a special skb destructor (tcp_wfree).
1047 *
1048 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
1049 * needs to be reallocated in a driver.
1050 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
1051 *
1052 * Since transmit from skb destructor is forbidden, we use a tasklet
1053 * to process all sockets that eventually need to send more skbs.
1054 * We use one tasklet per cpu, with its own queue of sockets.
1055 */
1056struct tsq_tasklet {
1057 struct tasklet_struct tasklet;
1058 struct list_head head; /* queue of tcp sockets */
1059};
1060static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
1061
1062static void tcp_tsq_write(struct sock *sk)
1063{
1064 if ((1 << sk->sk_state) &
1065 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
1066 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
1067 struct tcp_sock *tp = tcp_sk(sk);
1068
1069 if (tp->lost_out > tp->retrans_out &&
1070 tcp_snd_cwnd(tp) > tcp_packets_in_flight(tp)) {
1071 tcp_mstamp_refresh(tp);
1072 tcp_xmit_retransmit_queue(sk);
1073 }
1074
1075 tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
1076 0, GFP_ATOMIC);
1077 }
1078}
1079
1080static void tcp_tsq_handler(struct sock *sk)
1081{
1082 bh_lock_sock(sk);
1083 if (!sock_owned_by_user(sk))
1084 tcp_tsq_write(sk);
1085 else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
1086 sock_hold(sk);
1087 bh_unlock_sock(sk);
1088}
1089/*
1090 * One tasklet per cpu tries to send more skbs.
1091 * We run in tasklet context but need to disable irqs when
1092 * transferring tsq->head because tcp_wfree() might
1093 * interrupt us (non NAPI drivers)
1094 */
1095static void tcp_tasklet_func(struct tasklet_struct *t)
1096{
1097 struct tsq_tasklet *tsq = from_tasklet(tsq, t, tasklet);
1098 LIST_HEAD(list);
1099 unsigned long flags;
1100 struct list_head *q, *n;
1101 struct tcp_sock *tp;
1102 struct sock *sk;
1103
1104 local_irq_save(flags);
1105 list_splice_init(&tsq->head, &list);
1106 local_irq_restore(flags);
1107
1108 list_for_each_safe(q, n, &list) {
1109 tp = list_entry(q, struct tcp_sock, tsq_node);
1110 list_del(&tp->tsq_node);
1111
1112 sk = (struct sock *)tp;
1113 smp_mb__before_atomic();
1114 clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
1115
1116 tcp_tsq_handler(sk);
1117 sk_free(sk);
1118 }
1119}
1120
1121#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
1122 TCPF_WRITE_TIMER_DEFERRED | \
1123 TCPF_DELACK_TIMER_DEFERRED | \
1124 TCPF_MTU_REDUCED_DEFERRED | \
1125 TCPF_ACK_DEFERRED)
1126/**
1127 * tcp_release_cb - tcp release_sock() callback
1128 * @sk: socket
1129 *
1130 * called from release_sock() to perform protocol dependent
1131 * actions before socket release.
1132 */
1133void tcp_release_cb(struct sock *sk)
1134{
1135 unsigned long flags = smp_load_acquire(&sk->sk_tsq_flags);
1136 unsigned long nflags;
1137
1138 /* perform an atomic operation only if at least one flag is set */
1139 do {
1140 if (!(flags & TCP_DEFERRED_ALL))
1141 return;
1142 nflags = flags & ~TCP_DEFERRED_ALL;
1143 } while (!try_cmpxchg(&sk->sk_tsq_flags, &flags, nflags));
1144
1145 if (flags & TCPF_TSQ_DEFERRED) {
1146 tcp_tsq_write(sk);
1147 __sock_put(sk);
1148 }
1149
1150 if (flags & TCPF_WRITE_TIMER_DEFERRED) {
1151 tcp_write_timer_handler(sk);
1152 __sock_put(sk);
1153 }
1154 if (flags & TCPF_DELACK_TIMER_DEFERRED) {
1155 tcp_delack_timer_handler(sk);
1156 __sock_put(sk);
1157 }
1158 if (flags & TCPF_MTU_REDUCED_DEFERRED) {
1159 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
1160 __sock_put(sk);
1161 }
1162 if ((flags & TCPF_ACK_DEFERRED) && inet_csk_ack_scheduled(sk))
1163 tcp_send_ack(sk);
1164}
1165EXPORT_SYMBOL(tcp_release_cb);
1166
1167void __init tcp_tasklet_init(void)
1168{
1169 int i;
1170
1171 for_each_possible_cpu(i) {
1172 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
1173
1174 INIT_LIST_HEAD(&tsq->head);
1175 tasklet_setup(&tsq->tasklet, tcp_tasklet_func);
1176 }
1177}
1178
1179/*
1180 * Write buffer destructor automatically called from kfree_skb.
1181 * We can't xmit new skbs from this context, as we might already
1182 * hold qdisc lock.
1183 */
1184void tcp_wfree(struct sk_buff *skb)
1185{
1186 struct sock *sk = skb->sk;
1187 struct tcp_sock *tp = tcp_sk(sk);
1188 unsigned long flags, nval, oval;
1189 struct tsq_tasklet *tsq;
1190 bool empty;
1191
1192 /* Keep one reference on sk_wmem_alloc.
1193 * Will be released by sk_free() from here or tcp_tasklet_func()
1194 */
1195 WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
1196
1197 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
1198 * Wait until our queues (qdisc + devices) are drained.
1199 * This gives :
1200 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
1201 * - chance for incoming ACK (processed by another cpu maybe)
1202 * to migrate this flow (skb->ooo_okay will be eventually set)
1203 */
1204 if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
1205 goto out;
1206
1207 oval = smp_load_acquire(&sk->sk_tsq_flags);
1208 do {
1209 if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
1210 goto out;
1211
1212 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
1213 } while (!try_cmpxchg(&sk->sk_tsq_flags, &oval, nval));
1214
1215 /* queue this socket to tasklet queue */
1216 local_irq_save(flags);
1217 tsq = this_cpu_ptr(&tsq_tasklet);
1218 empty = list_empty(&tsq->head);
1219 list_add(&tp->tsq_node, &tsq->head);
1220 if (empty)
1221 tasklet_schedule(&tsq->tasklet);
1222 local_irq_restore(flags);
1223 return;
1224out:
1225 sk_free(sk);
1226}
1227
1228/* Note: Called under soft irq.
1229 * We can call TCP stack right away, unless socket is owned by user.
1230 */
1231enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
1232{
1233 struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
1234 struct sock *sk = (struct sock *)tp;
1235
1236 tcp_tsq_handler(sk);
1237 sock_put(sk);
1238
1239 return HRTIMER_NORESTART;
1240}
1241
1242static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb,
1243 u64 prior_wstamp)
1244{
1245 struct tcp_sock *tp = tcp_sk(sk);
1246
1247 if (sk->sk_pacing_status != SK_PACING_NONE) {
1248 unsigned long rate = READ_ONCE(sk->sk_pacing_rate);
1249
1250 /* Original sch_fq does not pace first 10 MSS
1251 * Note that tp->data_segs_out overflows after 2^32 packets,
1252 * this is a minor annoyance.
1253 */
1254 if (rate != ~0UL && rate && tp->data_segs_out >= 10) {
1255 u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate);
1256 u64 credit = tp->tcp_wstamp_ns - prior_wstamp;
1257
1258 /* take into account OS jitter */
1259 len_ns -= min_t(u64, len_ns / 2, credit);
1260 tp->tcp_wstamp_ns += len_ns;
1261 }
1262 }
1263 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
1264}
1265
1266INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1267INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1268INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb));
1269
1270/* This routine actually transmits TCP packets queued in by
1271 * tcp_do_sendmsg(). This is used by both the initial
1272 * transmission and possible later retransmissions.
1273 * All SKB's seen here are completely headerless. It is our
1274 * job to build the TCP header, and pass the packet down to
1275 * IP so it can do the same plus pass the packet off to the
1276 * device.
1277 *
1278 * We are working here with either a clone of the original
1279 * SKB, or a fresh unique copy made by the retransmit engine.
1280 */
1281static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
1282 int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
1283{
1284 const struct inet_connection_sock *icsk = inet_csk(sk);
1285 struct inet_sock *inet;
1286 struct tcp_sock *tp;
1287 struct tcp_skb_cb *tcb;
1288 struct tcp_out_options opts;
1289 unsigned int tcp_options_size, tcp_header_size;
1290 struct sk_buff *oskb = NULL;
1291 struct tcp_key key;
1292 struct tcphdr *th;
1293 u64 prior_wstamp;
1294 int err;
1295
1296 BUG_ON(!skb || !tcp_skb_pcount(skb));
1297 tp = tcp_sk(sk);
1298 prior_wstamp = tp->tcp_wstamp_ns;
1299 tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
1300 skb_set_delivery_time(skb, tp->tcp_wstamp_ns, true);
1301 if (clone_it) {
1302 oskb = skb;
1303
1304 tcp_skb_tsorted_save(oskb) {
1305 if (unlikely(skb_cloned(oskb)))
1306 skb = pskb_copy(oskb, gfp_mask);
1307 else
1308 skb = skb_clone(oskb, gfp_mask);
1309 } tcp_skb_tsorted_restore(oskb);
1310
1311 if (unlikely(!skb))
1312 return -ENOBUFS;
1313 /* retransmit skbs might have a non zero value in skb->dev
1314 * because skb->dev is aliased with skb->rbnode.rb_left
1315 */
1316 skb->dev = NULL;
1317 }
1318
1319 inet = inet_sk(sk);
1320 tcb = TCP_SKB_CB(skb);
1321 memset(&opts, 0, sizeof(opts));
1322
1323 tcp_get_current_key(sk, &key);
1324 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
1325 tcp_options_size = tcp_syn_options(sk, skb, &opts, &key);
1326 } else {
1327 tcp_options_size = tcp_established_options(sk, skb, &opts, &key);
1328 /* Force a PSH flag on all (GSO) packets to expedite GRO flush
1329 * at receiver : This slightly improve GRO performance.
1330 * Note that we do not force the PSH flag for non GSO packets,
1331 * because they might be sent under high congestion events,
1332 * and in this case it is better to delay the delivery of 1-MSS
1333 * packets and thus the corresponding ACK packet that would
1334 * release the following packet.
1335 */
1336 if (tcp_skb_pcount(skb) > 1)
1337 tcb->tcp_flags |= TCPHDR_PSH;
1338 }
1339 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1340
1341 /* We set skb->ooo_okay to one if this packet can select
1342 * a different TX queue than prior packets of this flow,
1343 * to avoid self inflicted reorders.
1344 * The 'other' queue decision is based on current cpu number
1345 * if XPS is enabled, or sk->sk_txhash otherwise.
1346 * We can switch to another (and better) queue if:
1347 * 1) No packet with payload is in qdisc/device queues.
1348 * Delays in TX completion can defeat the test
1349 * even if packets were already sent.
1350 * 2) Or rtx queue is empty.
1351 * This mitigates above case if ACK packets for
1352 * all prior packets were already processed.
1353 */
1354 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1) ||
1355 tcp_rtx_queue_empty(sk);
1356
1357 /* If we had to use memory reserve to allocate this skb,
1358 * this might cause drops if packet is looped back :
1359 * Other socket might not have SOCK_MEMALLOC.
1360 * Packets not looped back do not care about pfmemalloc.
1361 */
1362 skb->pfmemalloc = 0;
1363
1364 skb_push(skb, tcp_header_size);
1365 skb_reset_transport_header(skb);
1366
1367 skb_orphan(skb);
1368 skb->sk = sk;
1369 skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1370 refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1371
1372 skb_set_dst_pending_confirm(skb, READ_ONCE(sk->sk_dst_pending_confirm));
1373
1374 /* Build TCP header and checksum it. */
1375 th = (struct tcphdr *)skb->data;
1376 th->source = inet->inet_sport;
1377 th->dest = inet->inet_dport;
1378 th->seq = htonl(tcb->seq);
1379 th->ack_seq = htonl(rcv_nxt);
1380 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
1381 tcb->tcp_flags);
1382
1383 th->check = 0;
1384 th->urg_ptr = 0;
1385
1386 /* The urg_mode check is necessary during a below snd_una win probe */
1387 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
1388 if (before(tp->snd_up, tcb->seq + 0x10000)) {
1389 th->urg_ptr = htons(tp->snd_up - tcb->seq);
1390 th->urg = 1;
1391 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1392 th->urg_ptr = htons(0xFFFF);
1393 th->urg = 1;
1394 }
1395 }
1396
1397 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1398 if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
1399 th->window = htons(tcp_select_window(sk));
1400 tcp_ecn_send(sk, skb, th, tcp_header_size);
1401 } else {
1402 /* RFC1323: The window in SYN & SYN/ACK segments
1403 * is never scaled.
1404 */
1405 th->window = htons(min(tp->rcv_wnd, 65535U));
1406 }
1407
1408 tcp_options_write(th, tp, NULL, &opts, &key);
1409
1410 if (tcp_key_is_md5(&key)) {
1411#ifdef CONFIG_TCP_MD5SIG
1412 /* Calculate the MD5 hash, as we have all we need now */
1413 sk_gso_disable(sk);
1414 tp->af_specific->calc_md5_hash(opts.hash_location,
1415 key.md5_key, sk, skb);
1416#endif
1417 } else if (tcp_key_is_ao(&key)) {
1418 int err;
1419
1420 err = tcp_ao_transmit_skb(sk, skb, key.ao_key, th,
1421 opts.hash_location);
1422 if (err) {
1423 kfree_skb_reason(skb, SKB_DROP_REASON_NOT_SPECIFIED);
1424 return -ENOMEM;
1425 }
1426 }
1427
1428 /* BPF prog is the last one writing header option */
1429 bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts);
1430
1431 INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check,
1432 tcp_v6_send_check, tcp_v4_send_check,
1433 sk, skb);
1434
1435 if (likely(tcb->tcp_flags & TCPHDR_ACK))
1436 tcp_event_ack_sent(sk, rcv_nxt);
1437
1438 if (skb->len != tcp_header_size) {
1439 tcp_event_data_sent(tp, sk);
1440 tp->data_segs_out += tcp_skb_pcount(skb);
1441 tp->bytes_sent += skb->len - tcp_header_size;
1442 }
1443
1444 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1445 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1446 tcp_skb_pcount(skb));
1447
1448 tp->segs_out += tcp_skb_pcount(skb);
1449 skb_set_hash_from_sk(skb, sk);
1450 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1451 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1452 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1453
1454 /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */
1455
1456 /* Cleanup our debris for IP stacks */
1457 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1458 sizeof(struct inet6_skb_parm)));
1459
1460 tcp_add_tx_delay(skb, tp);
1461
1462 err = INDIRECT_CALL_INET(icsk->icsk_af_ops->queue_xmit,
1463 inet6_csk_xmit, ip_queue_xmit,
1464 sk, skb, &inet->cork.fl);
1465
1466 if (unlikely(err > 0)) {
1467 tcp_enter_cwr(sk);
1468 err = net_xmit_eval(err);
1469 }
1470 if (!err && oskb) {
1471 tcp_update_skb_after_send(sk, oskb, prior_wstamp);
1472 tcp_rate_skb_sent(sk, oskb);
1473 }
1474 return err;
1475}
1476
1477static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
1478 gfp_t gfp_mask)
1479{
1480 return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask,
1481 tcp_sk(sk)->rcv_nxt);
1482}
1483
1484/* This routine just queues the buffer for sending.
1485 *
1486 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1487 * otherwise socket can stall.
1488 */
1489static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1490{
1491 struct tcp_sock *tp = tcp_sk(sk);
1492
1493 /* Advance write_seq and place onto the write_queue. */
1494 WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq);
1495 __skb_header_release(skb);
1496 tcp_add_write_queue_tail(sk, skb);
1497 sk_wmem_queued_add(sk, skb->truesize);
1498 sk_mem_charge(sk, skb->truesize);
1499}
1500
1501/* Initialize TSO segments for a packet. */
1502static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1503{
1504 if (skb->len <= mss_now) {
1505 /* Avoid the costly divide in the normal
1506 * non-TSO case.
1507 */
1508 tcp_skb_pcount_set(skb, 1);
1509 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1510 } else {
1511 tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1512 TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1513 }
1514}
1515
1516/* Pcount in the middle of the write queue got changed, we need to do various
1517 * tweaks to fix counters
1518 */
1519static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1520{
1521 struct tcp_sock *tp = tcp_sk(sk);
1522
1523 tp->packets_out -= decr;
1524
1525 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1526 tp->sacked_out -= decr;
1527 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1528 tp->retrans_out -= decr;
1529 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1530 tp->lost_out -= decr;
1531
1532 /* Reno case is special. Sigh... */
1533 if (tcp_is_reno(tp) && decr > 0)
1534 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1535
1536 if (tp->lost_skb_hint &&
1537 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1538 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
1539 tp->lost_cnt_hint -= decr;
1540
1541 tcp_verify_left_out(tp);
1542}
1543
1544static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
1545{
1546 return TCP_SKB_CB(skb)->txstamp_ack ||
1547 (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
1548}
1549
1550static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1551{
1552 struct skb_shared_info *shinfo = skb_shinfo(skb);
1553
1554 if (unlikely(tcp_has_tx_tstamp(skb)) &&
1555 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1556 struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1557 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1558
1559 shinfo->tx_flags &= ~tsflags;
1560 shinfo2->tx_flags |= tsflags;
1561 swap(shinfo->tskey, shinfo2->tskey);
1562 TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
1563 TCP_SKB_CB(skb)->txstamp_ack = 0;
1564 }
1565}
1566
1567static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
1568{
1569 TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
1570 TCP_SKB_CB(skb)->eor = 0;
1571}
1572
1573/* Insert buff after skb on the write or rtx queue of sk. */
1574static void tcp_insert_write_queue_after(struct sk_buff *skb,
1575 struct sk_buff *buff,
1576 struct sock *sk,
1577 enum tcp_queue tcp_queue)
1578{
1579 if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
1580 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1581 else
1582 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
1583}
1584
1585/* Function to create two new TCP segments. Shrinks the given segment
1586 * to the specified size and appends a new segment with the rest of the
1587 * packet to the list. This won't be called frequently, I hope.
1588 * Remember, these are still headerless SKBs at this point.
1589 */
1590int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1591 struct sk_buff *skb, u32 len,
1592 unsigned int mss_now, gfp_t gfp)
1593{
1594 struct tcp_sock *tp = tcp_sk(sk);
1595 struct sk_buff *buff;
1596 int old_factor;
1597 long limit;
1598 int nlen;
1599 u8 flags;
1600
1601 if (WARN_ON(len > skb->len))
1602 return -EINVAL;
1603
1604 DEBUG_NET_WARN_ON_ONCE(skb_headlen(skb));
1605
1606 /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb.
1607 * We need some allowance to not penalize applications setting small
1608 * SO_SNDBUF values.
1609 * Also allow first and last skb in retransmit queue to be split.
1610 */
1611 limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_LEGACY_MAX_SIZE);
1612 if (unlikely((sk->sk_wmem_queued >> 1) > limit &&
1613 tcp_queue != TCP_FRAG_IN_WRITE_QUEUE &&
1614 skb != tcp_rtx_queue_head(sk) &&
1615 skb != tcp_rtx_queue_tail(sk))) {
1616 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG);
1617 return -ENOMEM;
1618 }
1619
1620 if (skb_unclone_keeptruesize(skb, gfp))
1621 return -ENOMEM;
1622
1623 /* Get a new skb... force flag on. */
1624 buff = tcp_stream_alloc_skb(sk, gfp, true);
1625 if (!buff)
1626 return -ENOMEM; /* We'll just try again later. */
1627 skb_copy_decrypted(buff, skb);
1628 mptcp_skb_ext_copy(buff, skb);
1629
1630 sk_wmem_queued_add(sk, buff->truesize);
1631 sk_mem_charge(sk, buff->truesize);
1632 nlen = skb->len - len;
1633 buff->truesize += nlen;
1634 skb->truesize -= nlen;
1635
1636 /* Correct the sequence numbers. */
1637 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1638 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1639 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1640
1641 /* PSH and FIN should only be set in the second packet. */
1642 flags = TCP_SKB_CB(skb)->tcp_flags;
1643 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1644 TCP_SKB_CB(buff)->tcp_flags = flags;
1645 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1646 tcp_skb_fragment_eor(skb, buff);
1647
1648 skb_split(skb, buff, len);
1649
1650 skb_set_delivery_time(buff, skb->tstamp, true);
1651 tcp_fragment_tstamp(skb, buff);
1652
1653 old_factor = tcp_skb_pcount(skb);
1654
1655 /* Fix up tso_factor for both original and new SKB. */
1656 tcp_set_skb_tso_segs(skb, mss_now);
1657 tcp_set_skb_tso_segs(buff, mss_now);
1658
1659 /* Update delivered info for the new segment */
1660 TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
1661
1662 /* If this packet has been sent out already, we must
1663 * adjust the various packet counters.
1664 */
1665 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1666 int diff = old_factor - tcp_skb_pcount(skb) -
1667 tcp_skb_pcount(buff);
1668
1669 if (diff)
1670 tcp_adjust_pcount(sk, skb, diff);
1671 }
1672
1673 /* Link BUFF into the send queue. */
1674 __skb_header_release(buff);
1675 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1676 if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
1677 list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
1678
1679 return 0;
1680}
1681
1682/* This is similar to __pskb_pull_tail(). The difference is that pulled
1683 * data is not copied, but immediately discarded.
1684 */
1685static int __pskb_trim_head(struct sk_buff *skb, int len)
1686{
1687 struct skb_shared_info *shinfo;
1688 int i, k, eat;
1689
1690 DEBUG_NET_WARN_ON_ONCE(skb_headlen(skb));
1691 eat = len;
1692 k = 0;
1693 shinfo = skb_shinfo(skb);
1694 for (i = 0; i < shinfo->nr_frags; i++) {
1695 int size = skb_frag_size(&shinfo->frags[i]);
1696
1697 if (size <= eat) {
1698 skb_frag_unref(skb, i);
1699 eat -= size;
1700 } else {
1701 shinfo->frags[k] = shinfo->frags[i];
1702 if (eat) {
1703 skb_frag_off_add(&shinfo->frags[k], eat);
1704 skb_frag_size_sub(&shinfo->frags[k], eat);
1705 eat = 0;
1706 }
1707 k++;
1708 }
1709 }
1710 shinfo->nr_frags = k;
1711
1712 skb->data_len -= len;
1713 skb->len = skb->data_len;
1714 return len;
1715}
1716
1717/* Remove acked data from a packet in the transmit queue. */
1718int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1719{
1720 u32 delta_truesize;
1721
1722 if (skb_unclone_keeptruesize(skb, GFP_ATOMIC))
1723 return -ENOMEM;
1724
1725 delta_truesize = __pskb_trim_head(skb, len);
1726
1727 TCP_SKB_CB(skb)->seq += len;
1728
1729 skb->truesize -= delta_truesize;
1730 sk_wmem_queued_add(sk, -delta_truesize);
1731 if (!skb_zcopy_pure(skb))
1732 sk_mem_uncharge(sk, delta_truesize);
1733
1734 /* Any change of skb->len requires recalculation of tso factor. */
1735 if (tcp_skb_pcount(skb) > 1)
1736 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1737
1738 return 0;
1739}
1740
1741/* Calculate MSS not accounting any TCP options. */
1742static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1743{
1744 const struct tcp_sock *tp = tcp_sk(sk);
1745 const struct inet_connection_sock *icsk = inet_csk(sk);
1746 int mss_now;
1747
1748 /* Calculate base mss without TCP options:
1749 It is MMS_S - sizeof(tcphdr) of rfc1122
1750 */
1751 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1752
1753 /* Clamp it (mss_clamp does not include tcp options) */
1754 if (mss_now > tp->rx_opt.mss_clamp)
1755 mss_now = tp->rx_opt.mss_clamp;
1756
1757 /* Now subtract optional transport overhead */
1758 mss_now -= icsk->icsk_ext_hdr_len;
1759
1760 /* Then reserve room for full set of TCP options and 8 bytes of data */
1761 mss_now = max(mss_now,
1762 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss));
1763 return mss_now;
1764}
1765
1766/* Calculate MSS. Not accounting for SACKs here. */
1767int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1768{
1769 /* Subtract TCP options size, not including SACKs */
1770 return __tcp_mtu_to_mss(sk, pmtu) -
1771 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1772}
1773EXPORT_SYMBOL(tcp_mtu_to_mss);
1774
1775/* Inverse of above */
1776int tcp_mss_to_mtu(struct sock *sk, int mss)
1777{
1778 const struct tcp_sock *tp = tcp_sk(sk);
1779 const struct inet_connection_sock *icsk = inet_csk(sk);
1780
1781 return mss +
1782 tp->tcp_header_len +
1783 icsk->icsk_ext_hdr_len +
1784 icsk->icsk_af_ops->net_header_len;
1785}
1786EXPORT_SYMBOL(tcp_mss_to_mtu);
1787
1788/* MTU probing init per socket */
1789void tcp_mtup_init(struct sock *sk)
1790{
1791 struct tcp_sock *tp = tcp_sk(sk);
1792 struct inet_connection_sock *icsk = inet_csk(sk);
1793 struct net *net = sock_net(sk);
1794
1795 icsk->icsk_mtup.enabled = READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing) > 1;
1796 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1797 icsk->icsk_af_ops->net_header_len;
1798 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, READ_ONCE(net->ipv4.sysctl_tcp_base_mss));
1799 icsk->icsk_mtup.probe_size = 0;
1800 if (icsk->icsk_mtup.enabled)
1801 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1802}
1803EXPORT_SYMBOL(tcp_mtup_init);
1804
1805/* This function synchronize snd mss to current pmtu/exthdr set.
1806
1807 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1808 for TCP options, but includes only bare TCP header.
1809
1810 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1811 It is minimum of user_mss and mss received with SYN.
1812 It also does not include TCP options.
1813
1814 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1815
1816 tp->mss_cache is current effective sending mss, including
1817 all tcp options except for SACKs. It is evaluated,
1818 taking into account current pmtu, but never exceeds
1819 tp->rx_opt.mss_clamp.
1820
1821 NOTE1. rfc1122 clearly states that advertised MSS
1822 DOES NOT include either tcp or ip options.
1823
1824 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1825 are READ ONLY outside this function. --ANK (980731)
1826 */
1827unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1828{
1829 struct tcp_sock *tp = tcp_sk(sk);
1830 struct inet_connection_sock *icsk = inet_csk(sk);
1831 int mss_now;
1832
1833 if (icsk->icsk_mtup.search_high > pmtu)
1834 icsk->icsk_mtup.search_high = pmtu;
1835
1836 mss_now = tcp_mtu_to_mss(sk, pmtu);
1837 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1838
1839 /* And store cached results */
1840 icsk->icsk_pmtu_cookie = pmtu;
1841 if (icsk->icsk_mtup.enabled)
1842 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1843 tp->mss_cache = mss_now;
1844
1845 return mss_now;
1846}
1847EXPORT_SYMBOL(tcp_sync_mss);
1848
1849/* Compute the current effective MSS, taking SACKs and IP options,
1850 * and even PMTU discovery events into account.
1851 */
1852unsigned int tcp_current_mss(struct sock *sk)
1853{
1854 const struct tcp_sock *tp = tcp_sk(sk);
1855 const struct dst_entry *dst = __sk_dst_get(sk);
1856 u32 mss_now;
1857 unsigned int header_len;
1858 struct tcp_out_options opts;
1859 struct tcp_key key;
1860
1861 mss_now = tp->mss_cache;
1862
1863 if (dst) {
1864 u32 mtu = dst_mtu(dst);
1865 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1866 mss_now = tcp_sync_mss(sk, mtu);
1867 }
1868 tcp_get_current_key(sk, &key);
1869 header_len = tcp_established_options(sk, NULL, &opts, &key) +
1870 sizeof(struct tcphdr);
1871 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1872 * some common options. If this is an odd packet (because we have SACK
1873 * blocks etc) then our calculated header_len will be different, and
1874 * we have to adjust mss_now correspondingly */
1875 if (header_len != tp->tcp_header_len) {
1876 int delta = (int) header_len - tp->tcp_header_len;
1877 mss_now -= delta;
1878 }
1879
1880 return mss_now;
1881}
1882
1883/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1884 * As additional protections, we do not touch cwnd in retransmission phases,
1885 * and if application hit its sndbuf limit recently.
1886 */
1887static void tcp_cwnd_application_limited(struct sock *sk)
1888{
1889 struct tcp_sock *tp = tcp_sk(sk);
1890
1891 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
1892 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
1893 /* Limited by application or receiver window. */
1894 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
1895 u32 win_used = max(tp->snd_cwnd_used, init_win);
1896 if (win_used < tcp_snd_cwnd(tp)) {
1897 tp->snd_ssthresh = tcp_current_ssthresh(sk);
1898 tcp_snd_cwnd_set(tp, (tcp_snd_cwnd(tp) + win_used) >> 1);
1899 }
1900 tp->snd_cwnd_used = 0;
1901 }
1902 tp->snd_cwnd_stamp = tcp_jiffies32;
1903}
1904
1905static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1906{
1907 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1908 struct tcp_sock *tp = tcp_sk(sk);
1909
1910 /* Track the strongest available signal of the degree to which the cwnd
1911 * is fully utilized. If cwnd-limited then remember that fact for the
1912 * current window. If not cwnd-limited then track the maximum number of
1913 * outstanding packets in the current window. (If cwnd-limited then we
1914 * chose to not update tp->max_packets_out to avoid an extra else
1915 * clause with no functional impact.)
1916 */
1917 if (!before(tp->snd_una, tp->cwnd_usage_seq) ||
1918 is_cwnd_limited ||
1919 (!tp->is_cwnd_limited &&
1920 tp->packets_out > tp->max_packets_out)) {
1921 tp->is_cwnd_limited = is_cwnd_limited;
1922 tp->max_packets_out = tp->packets_out;
1923 tp->cwnd_usage_seq = tp->snd_nxt;
1924 }
1925
1926 if (tcp_is_cwnd_limited(sk)) {
1927 /* Network is feed fully. */
1928 tp->snd_cwnd_used = 0;
1929 tp->snd_cwnd_stamp = tcp_jiffies32;
1930 } else {
1931 /* Network starves. */
1932 if (tp->packets_out > tp->snd_cwnd_used)
1933 tp->snd_cwnd_used = tp->packets_out;
1934
1935 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle) &&
1936 (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1937 !ca_ops->cong_control)
1938 tcp_cwnd_application_limited(sk);
1939
1940 /* The following conditions together indicate the starvation
1941 * is caused by insufficient sender buffer:
1942 * 1) just sent some data (see tcp_write_xmit)
1943 * 2) not cwnd limited (this else condition)
1944 * 3) no more data to send (tcp_write_queue_empty())
1945 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1946 */
1947 if (tcp_write_queue_empty(sk) && sk->sk_socket &&
1948 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
1949 (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
1950 tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1951 }
1952}
1953
1954/* Minshall's variant of the Nagle send check. */
1955static bool tcp_minshall_check(const struct tcp_sock *tp)
1956{
1957 return after(tp->snd_sml, tp->snd_una) &&
1958 !after(tp->snd_sml, tp->snd_nxt);
1959}
1960
1961/* Update snd_sml if this skb is under mss
1962 * Note that a TSO packet might end with a sub-mss segment
1963 * The test is really :
1964 * if ((skb->len % mss) != 0)
1965 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1966 * But we can avoid doing the divide again given we already have
1967 * skb_pcount = skb->len / mss_now
1968 */
1969static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1970 const struct sk_buff *skb)
1971{
1972 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1973 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1974}
1975
1976/* Return false, if packet can be sent now without violation Nagle's rules:
1977 * 1. It is full sized. (provided by caller in %partial bool)
1978 * 2. Or it contains FIN. (already checked by caller)
1979 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1980 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1981 * With Minshall's modification: all sent small packets are ACKed.
1982 */
1983static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1984 int nonagle)
1985{
1986 return partial &&
1987 ((nonagle & TCP_NAGLE_CORK) ||
1988 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1989}
1990
1991/* Return how many segs we'd like on a TSO packet,
1992 * depending on current pacing rate, and how close the peer is.
1993 *
1994 * Rationale is:
1995 * - For close peers, we rather send bigger packets to reduce
1996 * cpu costs, because occasional losses will be repaired fast.
1997 * - For long distance/rtt flows, we would like to get ACK clocking
1998 * with 1 ACK per ms.
1999 *
2000 * Use min_rtt to help adapt TSO burst size, with smaller min_rtt resulting
2001 * in bigger TSO bursts. We we cut the RTT-based allowance in half
2002 * for every 2^9 usec (aka 512 us) of RTT, so that the RTT-based allowance
2003 * is below 1500 bytes after 6 * ~500 usec = 3ms.
2004 */
2005static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
2006 int min_tso_segs)
2007{
2008 unsigned long bytes;
2009 u32 r;
2010
2011 bytes = READ_ONCE(sk->sk_pacing_rate) >> READ_ONCE(sk->sk_pacing_shift);
2012
2013 r = tcp_min_rtt(tcp_sk(sk)) >> READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_rtt_log);
2014 if (r < BITS_PER_TYPE(sk->sk_gso_max_size))
2015 bytes += sk->sk_gso_max_size >> r;
2016
2017 bytes = min_t(unsigned long, bytes, sk->sk_gso_max_size);
2018
2019 return max_t(u32, bytes / mss_now, min_tso_segs);
2020}
2021
2022/* Return the number of segments we want in the skb we are transmitting.
2023 * See if congestion control module wants to decide; otherwise, autosize.
2024 */
2025static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
2026{
2027 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
2028 u32 min_tso, tso_segs;
2029
2030 min_tso = ca_ops->min_tso_segs ?
2031 ca_ops->min_tso_segs(sk) :
2032 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs);
2033
2034 tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
2035 return min_t(u32, tso_segs, sk->sk_gso_max_segs);
2036}
2037
2038/* Returns the portion of skb which can be sent right away */
2039static unsigned int tcp_mss_split_point(const struct sock *sk,
2040 const struct sk_buff *skb,
2041 unsigned int mss_now,
2042 unsigned int max_segs,
2043 int nonagle)
2044{
2045 const struct tcp_sock *tp = tcp_sk(sk);
2046 u32 partial, needed, window, max_len;
2047
2048 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2049 max_len = mss_now * max_segs;
2050
2051 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
2052 return max_len;
2053
2054 needed = min(skb->len, window);
2055
2056 if (max_len <= needed)
2057 return max_len;
2058
2059 partial = needed % mss_now;
2060 /* If last segment is not a full MSS, check if Nagle rules allow us
2061 * to include this last segment in this skb.
2062 * Otherwise, we'll split the skb at last MSS boundary
2063 */
2064 if (tcp_nagle_check(partial != 0, tp, nonagle))
2065 return needed - partial;
2066
2067 return needed;
2068}
2069
2070/* Can at least one segment of SKB be sent right now, according to the
2071 * congestion window rules? If so, return how many segments are allowed.
2072 */
2073static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
2074 const struct sk_buff *skb)
2075{
2076 u32 in_flight, cwnd, halfcwnd;
2077
2078 /* Don't be strict about the congestion window for the final FIN. */
2079 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
2080 tcp_skb_pcount(skb) == 1)
2081 return 1;
2082
2083 in_flight = tcp_packets_in_flight(tp);
2084 cwnd = tcp_snd_cwnd(tp);
2085 if (in_flight >= cwnd)
2086 return 0;
2087
2088 /* For better scheduling, ensure we have at least
2089 * 2 GSO packets in flight.
2090 */
2091 halfcwnd = max(cwnd >> 1, 1U);
2092 return min(halfcwnd, cwnd - in_flight);
2093}
2094
2095/* Initialize TSO state of a skb.
2096 * This must be invoked the first time we consider transmitting
2097 * SKB onto the wire.
2098 */
2099static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
2100{
2101 int tso_segs = tcp_skb_pcount(skb);
2102
2103 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
2104 tcp_set_skb_tso_segs(skb, mss_now);
2105 tso_segs = tcp_skb_pcount(skb);
2106 }
2107 return tso_segs;
2108}
2109
2110
2111/* Return true if the Nagle test allows this packet to be
2112 * sent now.
2113 */
2114static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
2115 unsigned int cur_mss, int nonagle)
2116{
2117 /* Nagle rule does not apply to frames, which sit in the middle of the
2118 * write_queue (they have no chances to get new data).
2119 *
2120 * This is implemented in the callers, where they modify the 'nonagle'
2121 * argument based upon the location of SKB in the send queue.
2122 */
2123 if (nonagle & TCP_NAGLE_PUSH)
2124 return true;
2125
2126 /* Don't use the nagle rule for urgent data (or for the final FIN). */
2127 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
2128 return true;
2129
2130 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
2131 return true;
2132
2133 return false;
2134}
2135
2136/* Does at least the first segment of SKB fit into the send window? */
2137static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
2138 const struct sk_buff *skb,
2139 unsigned int cur_mss)
2140{
2141 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2142
2143 if (skb->len > cur_mss)
2144 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
2145
2146 return !after(end_seq, tcp_wnd_end(tp));
2147}
2148
2149/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
2150 * which is put after SKB on the list. It is very much like
2151 * tcp_fragment() except that it may make several kinds of assumptions
2152 * in order to speed up the splitting operation. In particular, we
2153 * know that all the data is in scatter-gather pages, and that the
2154 * packet has never been sent out before (and thus is not cloned).
2155 */
2156static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
2157 unsigned int mss_now, gfp_t gfp)
2158{
2159 int nlen = skb->len - len;
2160 struct sk_buff *buff;
2161 u8 flags;
2162
2163 /* All of a TSO frame must be composed of paged data. */
2164 DEBUG_NET_WARN_ON_ONCE(skb->len != skb->data_len);
2165
2166 buff = tcp_stream_alloc_skb(sk, gfp, true);
2167 if (unlikely(!buff))
2168 return -ENOMEM;
2169 skb_copy_decrypted(buff, skb);
2170 mptcp_skb_ext_copy(buff, skb);
2171
2172 sk_wmem_queued_add(sk, buff->truesize);
2173 sk_mem_charge(sk, buff->truesize);
2174 buff->truesize += nlen;
2175 skb->truesize -= nlen;
2176
2177 /* Correct the sequence numbers. */
2178 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
2179 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
2180 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
2181
2182 /* PSH and FIN should only be set in the second packet. */
2183 flags = TCP_SKB_CB(skb)->tcp_flags;
2184 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
2185 TCP_SKB_CB(buff)->tcp_flags = flags;
2186
2187 tcp_skb_fragment_eor(skb, buff);
2188
2189 skb_split(skb, buff, len);
2190 tcp_fragment_tstamp(skb, buff);
2191
2192 /* Fix up tso_factor for both original and new SKB. */
2193 tcp_set_skb_tso_segs(skb, mss_now);
2194 tcp_set_skb_tso_segs(buff, mss_now);
2195
2196 /* Link BUFF into the send queue. */
2197 __skb_header_release(buff);
2198 tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE);
2199
2200 return 0;
2201}
2202
2203/* Try to defer sending, if possible, in order to minimize the amount
2204 * of TSO splitting we do. View it as a kind of TSO Nagle test.
2205 *
2206 * This algorithm is from John Heffner.
2207 */
2208static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
2209 bool *is_cwnd_limited,
2210 bool *is_rwnd_limited,
2211 u32 max_segs)
2212{
2213 const struct inet_connection_sock *icsk = inet_csk(sk);
2214 u32 send_win, cong_win, limit, in_flight;
2215 struct tcp_sock *tp = tcp_sk(sk);
2216 struct sk_buff *head;
2217 int win_divisor;
2218 s64 delta;
2219
2220 if (icsk->icsk_ca_state >= TCP_CA_Recovery)
2221 goto send_now;
2222
2223 /* Avoid bursty behavior by allowing defer
2224 * only if the last write was recent (1 ms).
2225 * Note that tp->tcp_wstamp_ns can be in the future if we have
2226 * packets waiting in a qdisc or device for EDT delivery.
2227 */
2228 delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC;
2229 if (delta > 0)
2230 goto send_now;
2231
2232 in_flight = tcp_packets_in_flight(tp);
2233
2234 BUG_ON(tcp_skb_pcount(skb) <= 1);
2235 BUG_ON(tcp_snd_cwnd(tp) <= in_flight);
2236
2237 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2238
2239 /* From in_flight test above, we know that cwnd > in_flight. */
2240 cong_win = (tcp_snd_cwnd(tp) - in_flight) * tp->mss_cache;
2241
2242 limit = min(send_win, cong_win);
2243
2244 /* If a full-sized TSO skb can be sent, do it. */
2245 if (limit >= max_segs * tp->mss_cache)
2246 goto send_now;
2247
2248 /* Middle in queue won't get any more data, full sendable already? */
2249 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
2250 goto send_now;
2251
2252 win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
2253 if (win_divisor) {
2254 u32 chunk = min(tp->snd_wnd, tcp_snd_cwnd(tp) * tp->mss_cache);
2255
2256 /* If at least some fraction of a window is available,
2257 * just use it.
2258 */
2259 chunk /= win_divisor;
2260 if (limit >= chunk)
2261 goto send_now;
2262 } else {
2263 /* Different approach, try not to defer past a single
2264 * ACK. Receiver should ACK every other full sized
2265 * frame, so if we have space for more than 3 frames
2266 * then send now.
2267 */
2268 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
2269 goto send_now;
2270 }
2271
2272 /* TODO : use tsorted_sent_queue ? */
2273 head = tcp_rtx_queue_head(sk);
2274 if (!head)
2275 goto send_now;
2276 delta = tp->tcp_clock_cache - head->tstamp;
2277 /* If next ACK is likely to come too late (half srtt), do not defer */
2278 if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0)
2279 goto send_now;
2280
2281 /* Ok, it looks like it is advisable to defer.
2282 * Three cases are tracked :
2283 * 1) We are cwnd-limited
2284 * 2) We are rwnd-limited
2285 * 3) We are application limited.
2286 */
2287 if (cong_win < send_win) {
2288 if (cong_win <= skb->len) {
2289 *is_cwnd_limited = true;
2290 return true;
2291 }
2292 } else {
2293 if (send_win <= skb->len) {
2294 *is_rwnd_limited = true;
2295 return true;
2296 }
2297 }
2298
2299 /* If this packet won't get more data, do not wait. */
2300 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
2301 TCP_SKB_CB(skb)->eor)
2302 goto send_now;
2303
2304 return true;
2305
2306send_now:
2307 return false;
2308}
2309
2310static inline void tcp_mtu_check_reprobe(struct sock *sk)
2311{
2312 struct inet_connection_sock *icsk = inet_csk(sk);
2313 struct tcp_sock *tp = tcp_sk(sk);
2314 struct net *net = sock_net(sk);
2315 u32 interval;
2316 s32 delta;
2317
2318 interval = READ_ONCE(net->ipv4.sysctl_tcp_probe_interval);
2319 delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2320 if (unlikely(delta >= interval * HZ)) {
2321 int mss = tcp_current_mss(sk);
2322
2323 /* Update current search range */
2324 icsk->icsk_mtup.probe_size = 0;
2325 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
2326 sizeof(struct tcphdr) +
2327 icsk->icsk_af_ops->net_header_len;
2328 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
2329
2330 /* Update probe time stamp */
2331 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2332 }
2333}
2334
2335static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
2336{
2337 struct sk_buff *skb, *next;
2338
2339 skb = tcp_send_head(sk);
2340 tcp_for_write_queue_from_safe(skb, next, sk) {
2341 if (len <= skb->len)
2342 break;
2343
2344 if (unlikely(TCP_SKB_CB(skb)->eor) ||
2345 tcp_has_tx_tstamp(skb) ||
2346 !skb_pure_zcopy_same(skb, next))
2347 return false;
2348
2349 len -= skb->len;
2350 }
2351
2352 return true;
2353}
2354
2355static int tcp_clone_payload(struct sock *sk, struct sk_buff *to,
2356 int probe_size)
2357{
2358 skb_frag_t *lastfrag = NULL, *fragto = skb_shinfo(to)->frags;
2359 int i, todo, len = 0, nr_frags = 0;
2360 const struct sk_buff *skb;
2361
2362 if (!sk_wmem_schedule(sk, to->truesize + probe_size))
2363 return -ENOMEM;
2364
2365 skb_queue_walk(&sk->sk_write_queue, skb) {
2366 const skb_frag_t *fragfrom = skb_shinfo(skb)->frags;
2367
2368 if (skb_headlen(skb))
2369 return -EINVAL;
2370
2371 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++, fragfrom++) {
2372 if (len >= probe_size)
2373 goto commit;
2374 todo = min_t(int, skb_frag_size(fragfrom),
2375 probe_size - len);
2376 len += todo;
2377 if (lastfrag &&
2378 skb_frag_page(fragfrom) == skb_frag_page(lastfrag) &&
2379 skb_frag_off(fragfrom) == skb_frag_off(lastfrag) +
2380 skb_frag_size(lastfrag)) {
2381 skb_frag_size_add(lastfrag, todo);
2382 continue;
2383 }
2384 if (unlikely(nr_frags == MAX_SKB_FRAGS))
2385 return -E2BIG;
2386 skb_frag_page_copy(fragto, fragfrom);
2387 skb_frag_off_copy(fragto, fragfrom);
2388 skb_frag_size_set(fragto, todo);
2389 nr_frags++;
2390 lastfrag = fragto++;
2391 }
2392 }
2393commit:
2394 WARN_ON_ONCE(len != probe_size);
2395 for (i = 0; i < nr_frags; i++)
2396 skb_frag_ref(to, i);
2397
2398 skb_shinfo(to)->nr_frags = nr_frags;
2399 to->truesize += probe_size;
2400 to->len += probe_size;
2401 to->data_len += probe_size;
2402 __skb_header_release(to);
2403 return 0;
2404}
2405
2406/* Create a new MTU probe if we are ready.
2407 * MTU probe is regularly attempting to increase the path MTU by
2408 * deliberately sending larger packets. This discovers routing
2409 * changes resulting in larger path MTUs.
2410 *
2411 * Returns 0 if we should wait to probe (no cwnd available),
2412 * 1 if a probe was sent,
2413 * -1 otherwise
2414 */
2415static int tcp_mtu_probe(struct sock *sk)
2416{
2417 struct inet_connection_sock *icsk = inet_csk(sk);
2418 struct tcp_sock *tp = tcp_sk(sk);
2419 struct sk_buff *skb, *nskb, *next;
2420 struct net *net = sock_net(sk);
2421 int probe_size;
2422 int size_needed;
2423 int copy, len;
2424 int mss_now;
2425 int interval;
2426
2427 /* Not currently probing/verifying,
2428 * not in recovery,
2429 * have enough cwnd, and
2430 * not SACKing (the variable headers throw things off)
2431 */
2432 if (likely(!icsk->icsk_mtup.enabled ||
2433 icsk->icsk_mtup.probe_size ||
2434 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
2435 tcp_snd_cwnd(tp) < 11 ||
2436 tp->rx_opt.num_sacks || tp->rx_opt.dsack))
2437 return -1;
2438
2439 /* Use binary search for probe_size between tcp_mss_base,
2440 * and current mss_clamp. if (search_high - search_low)
2441 * smaller than a threshold, backoff from probing.
2442 */
2443 mss_now = tcp_current_mss(sk);
2444 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
2445 icsk->icsk_mtup.search_low) >> 1);
2446 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2447 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2448 /* When misfortune happens, we are reprobing actively,
2449 * and then reprobe timer has expired. We stick with current
2450 * probing process by not resetting search range to its orignal.
2451 */
2452 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2453 interval < READ_ONCE(net->ipv4.sysctl_tcp_probe_threshold)) {
2454 /* Check whether enough time has elaplased for
2455 * another round of probing.
2456 */
2457 tcp_mtu_check_reprobe(sk);
2458 return -1;
2459 }
2460
2461 /* Have enough data in the send queue to probe? */
2462 if (tp->write_seq - tp->snd_nxt < size_needed)
2463 return -1;
2464
2465 if (tp->snd_wnd < size_needed)
2466 return -1;
2467 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2468 return 0;
2469
2470 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2471 if (tcp_packets_in_flight(tp) + 2 > tcp_snd_cwnd(tp)) {
2472 if (!tcp_packets_in_flight(tp))
2473 return -1;
2474 else
2475 return 0;
2476 }
2477
2478 if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
2479 return -1;
2480
2481 /* We're allowed to probe. Build it now. */
2482 nskb = tcp_stream_alloc_skb(sk, GFP_ATOMIC, false);
2483 if (!nskb)
2484 return -1;
2485
2486 /* build the payload, and be prepared to abort if this fails. */
2487 if (tcp_clone_payload(sk, nskb, probe_size)) {
2488 tcp_skb_tsorted_anchor_cleanup(nskb);
2489 consume_skb(nskb);
2490 return -1;
2491 }
2492 sk_wmem_queued_add(sk, nskb->truesize);
2493 sk_mem_charge(sk, nskb->truesize);
2494
2495 skb = tcp_send_head(sk);
2496 skb_copy_decrypted(nskb, skb);
2497 mptcp_skb_ext_copy(nskb, skb);
2498
2499 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
2500 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
2501 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
2502
2503 tcp_insert_write_queue_before(nskb, skb, sk);
2504 tcp_highest_sack_replace(sk, skb, nskb);
2505
2506 len = 0;
2507 tcp_for_write_queue_from_safe(skb, next, sk) {
2508 copy = min_t(int, skb->len, probe_size - len);
2509
2510 if (skb->len <= copy) {
2511 /* We've eaten all the data from this skb.
2512 * Throw it away. */
2513 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2514 /* If this is the last SKB we copy and eor is set
2515 * we need to propagate it to the new skb.
2516 */
2517 TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
2518 tcp_skb_collapse_tstamp(nskb, skb);
2519 tcp_unlink_write_queue(skb, sk);
2520 tcp_wmem_free_skb(sk, skb);
2521 } else {
2522 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
2523 ~(TCPHDR_FIN|TCPHDR_PSH);
2524 __pskb_trim_head(skb, copy);
2525 tcp_set_skb_tso_segs(skb, mss_now);
2526 TCP_SKB_CB(skb)->seq += copy;
2527 }
2528
2529 len += copy;
2530
2531 if (len >= probe_size)
2532 break;
2533 }
2534 tcp_init_tso_segs(nskb, nskb->len);
2535
2536 /* We're ready to send. If this fails, the probe will
2537 * be resegmented into mss-sized pieces by tcp_write_xmit().
2538 */
2539 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
2540 /* Decrement cwnd here because we are sending
2541 * effectively two packets. */
2542 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) - 1);
2543 tcp_event_new_data_sent(sk, nskb);
2544
2545 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2546 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
2547 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
2548
2549 return 1;
2550 }
2551
2552 return -1;
2553}
2554
2555static bool tcp_pacing_check(struct sock *sk)
2556{
2557 struct tcp_sock *tp = tcp_sk(sk);
2558
2559 if (!tcp_needs_internal_pacing(sk))
2560 return false;
2561
2562 if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache)
2563 return false;
2564
2565 if (!hrtimer_is_queued(&tp->pacing_timer)) {
2566 hrtimer_start(&tp->pacing_timer,
2567 ns_to_ktime(tp->tcp_wstamp_ns),
2568 HRTIMER_MODE_ABS_PINNED_SOFT);
2569 sock_hold(sk);
2570 }
2571 return true;
2572}
2573
2574static bool tcp_rtx_queue_empty_or_single_skb(const struct sock *sk)
2575{
2576 const struct rb_node *node = sk->tcp_rtx_queue.rb_node;
2577
2578 /* No skb in the rtx queue. */
2579 if (!node)
2580 return true;
2581
2582 /* Only one skb in rtx queue. */
2583 return !node->rb_left && !node->rb_right;
2584}
2585
2586/* TCP Small Queues :
2587 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2588 * (These limits are doubled for retransmits)
2589 * This allows for :
2590 * - better RTT estimation and ACK scheduling
2591 * - faster recovery
2592 * - high rates
2593 * Alas, some drivers / subsystems require a fair amount
2594 * of queued bytes to ensure line rate.
2595 * One example is wifi aggregation (802.11 AMPDU)
2596 */
2597static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
2598 unsigned int factor)
2599{
2600 unsigned long limit;
2601
2602 limit = max_t(unsigned long,
2603 2 * skb->truesize,
2604 READ_ONCE(sk->sk_pacing_rate) >> READ_ONCE(sk->sk_pacing_shift));
2605 if (sk->sk_pacing_status == SK_PACING_NONE)
2606 limit = min_t(unsigned long, limit,
2607 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes));
2608 limit <<= factor;
2609
2610 if (static_branch_unlikely(&tcp_tx_delay_enabled) &&
2611 tcp_sk(sk)->tcp_tx_delay) {
2612 u64 extra_bytes = (u64)READ_ONCE(sk->sk_pacing_rate) *
2613 tcp_sk(sk)->tcp_tx_delay;
2614
2615 /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we
2616 * approximate our needs assuming an ~100% skb->truesize overhead.
2617 * USEC_PER_SEC is approximated by 2^20.
2618 * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift.
2619 */
2620 extra_bytes >>= (20 - 1);
2621 limit += extra_bytes;
2622 }
2623 if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2624 /* Always send skb if rtx queue is empty or has one skb.
2625 * No need to wait for TX completion to call us back,
2626 * after softirq/tasklet schedule.
2627 * This helps when TX completions are delayed too much.
2628 */
2629 if (tcp_rtx_queue_empty_or_single_skb(sk))
2630 return false;
2631
2632 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2633 /* It is possible TX completion already happened
2634 * before we set TSQ_THROTTLED, so we must
2635 * test again the condition.
2636 */
2637 smp_mb__after_atomic();
2638 if (refcount_read(&sk->sk_wmem_alloc) > limit)
2639 return true;
2640 }
2641 return false;
2642}
2643
2644static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
2645{
2646 const u32 now = tcp_jiffies32;
2647 enum tcp_chrono old = tp->chrono_type;
2648
2649 if (old > TCP_CHRONO_UNSPEC)
2650 tp->chrono_stat[old - 1] += now - tp->chrono_start;
2651 tp->chrono_start = now;
2652 tp->chrono_type = new;
2653}
2654
2655void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
2656{
2657 struct tcp_sock *tp = tcp_sk(sk);
2658
2659 /* If there are multiple conditions worthy of tracking in a
2660 * chronograph then the highest priority enum takes precedence
2661 * over the other conditions. So that if something "more interesting"
2662 * starts happening, stop the previous chrono and start a new one.
2663 */
2664 if (type > tp->chrono_type)
2665 tcp_chrono_set(tp, type);
2666}
2667
2668void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
2669{
2670 struct tcp_sock *tp = tcp_sk(sk);
2671
2672
2673 /* There are multiple conditions worthy of tracking in a
2674 * chronograph, so that the highest priority enum takes
2675 * precedence over the other conditions (see tcp_chrono_start).
2676 * If a condition stops, we only stop chrono tracking if
2677 * it's the "most interesting" or current chrono we are
2678 * tracking and starts busy chrono if we have pending data.
2679 */
2680 if (tcp_rtx_and_write_queues_empty(sk))
2681 tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
2682 else if (type == tp->chrono_type)
2683 tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2684}
2685
2686/* This routine writes packets to the network. It advances the
2687 * send_head. This happens as incoming acks open up the remote
2688 * window for us.
2689 *
2690 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2691 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2692 * account rare use of URG, this is not a big flaw.
2693 *
2694 * Send at most one packet when push_one > 0. Temporarily ignore
2695 * cwnd limit to force at most one packet out when push_one == 2.
2696
2697 * Returns true, if no segments are in flight and we have queued segments,
2698 * but cannot send anything now because of SWS or another problem.
2699 */
2700static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2701 int push_one, gfp_t gfp)
2702{
2703 struct tcp_sock *tp = tcp_sk(sk);
2704 struct sk_buff *skb;
2705 unsigned int tso_segs, sent_pkts;
2706 int cwnd_quota;
2707 int result;
2708 bool is_cwnd_limited = false, is_rwnd_limited = false;
2709 u32 max_segs;
2710
2711 sent_pkts = 0;
2712
2713 tcp_mstamp_refresh(tp);
2714 if (!push_one) {
2715 /* Do MTU probing. */
2716 result = tcp_mtu_probe(sk);
2717 if (!result) {
2718 return false;
2719 } else if (result > 0) {
2720 sent_pkts = 1;
2721 }
2722 }
2723
2724 max_segs = tcp_tso_segs(sk, mss_now);
2725 while ((skb = tcp_send_head(sk))) {
2726 unsigned int limit;
2727
2728 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2729 /* "skb_mstamp_ns" is used as a start point for the retransmit timer */
2730 tp->tcp_wstamp_ns = tp->tcp_clock_cache;
2731 skb_set_delivery_time(skb, tp->tcp_wstamp_ns, true);
2732 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
2733 tcp_init_tso_segs(skb, mss_now);
2734 goto repair; /* Skip network transmission */
2735 }
2736
2737 if (tcp_pacing_check(sk))
2738 break;
2739
2740 tso_segs = tcp_init_tso_segs(skb, mss_now);
2741 BUG_ON(!tso_segs);
2742
2743 cwnd_quota = tcp_cwnd_test(tp, skb);
2744 if (!cwnd_quota) {
2745 if (push_one == 2)
2746 /* Force out a loss probe pkt. */
2747 cwnd_quota = 1;
2748 else
2749 break;
2750 }
2751
2752 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
2753 is_rwnd_limited = true;
2754 break;
2755 }
2756
2757 if (tso_segs == 1) {
2758 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2759 (tcp_skb_is_last(sk, skb) ?
2760 nonagle : TCP_NAGLE_PUSH))))
2761 break;
2762 } else {
2763 if (!push_one &&
2764 tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2765 &is_rwnd_limited, max_segs))
2766 break;
2767 }
2768
2769 limit = mss_now;
2770 if (tso_segs > 1 && !tcp_urg_mode(tp))
2771 limit = tcp_mss_split_point(sk, skb, mss_now,
2772 min_t(unsigned int,
2773 cwnd_quota,
2774 max_segs),
2775 nonagle);
2776
2777 if (skb->len > limit &&
2778 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
2779 break;
2780
2781 if (tcp_small_queue_check(sk, skb, 0))
2782 break;
2783
2784 /* Argh, we hit an empty skb(), presumably a thread
2785 * is sleeping in sendmsg()/sk_stream_wait_memory().
2786 * We do not want to send a pure-ack packet and have
2787 * a strange looking rtx queue with empty packet(s).
2788 */
2789 if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq)
2790 break;
2791
2792 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2793 break;
2794
2795repair:
2796 /* Advance the send_head. This one is sent out.
2797 * This call will increment packets_out.
2798 */
2799 tcp_event_new_data_sent(sk, skb);
2800
2801 tcp_minshall_update(tp, mss_now, skb);
2802 sent_pkts += tcp_skb_pcount(skb);
2803
2804 if (push_one)
2805 break;
2806 }
2807
2808 if (is_rwnd_limited)
2809 tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
2810 else
2811 tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
2812
2813 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tcp_snd_cwnd(tp));
2814 if (likely(sent_pkts || is_cwnd_limited))
2815 tcp_cwnd_validate(sk, is_cwnd_limited);
2816
2817 if (likely(sent_pkts)) {
2818 if (tcp_in_cwnd_reduction(sk))
2819 tp->prr_out += sent_pkts;
2820
2821 /* Send one loss probe per tail loss episode. */
2822 if (push_one != 2)
2823 tcp_schedule_loss_probe(sk, false);
2824 return false;
2825 }
2826 return !tp->packets_out && !tcp_write_queue_empty(sk);
2827}
2828
2829bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
2830{
2831 struct inet_connection_sock *icsk = inet_csk(sk);
2832 struct tcp_sock *tp = tcp_sk(sk);
2833 u32 timeout, timeout_us, rto_delta_us;
2834 int early_retrans;
2835
2836 /* Don't do any loss probe on a Fast Open connection before 3WHS
2837 * finishes.
2838 */
2839 if (rcu_access_pointer(tp->fastopen_rsk))
2840 return false;
2841
2842 early_retrans = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_early_retrans);
2843 /* Schedule a loss probe in 2*RTT for SACK capable connections
2844 * not in loss recovery, that are either limited by cwnd or application.
2845 */
2846 if ((early_retrans != 3 && early_retrans != 4) ||
2847 !tp->packets_out || !tcp_is_sack(tp) ||
2848 (icsk->icsk_ca_state != TCP_CA_Open &&
2849 icsk->icsk_ca_state != TCP_CA_CWR))
2850 return false;
2851
2852 /* Probe timeout is 2*rtt. Add minimum RTO to account
2853 * for delayed ack when there's one outstanding packet. If no RTT
2854 * sample is available then probe after TCP_TIMEOUT_INIT.
2855 */
2856 if (tp->srtt_us) {
2857 timeout_us = tp->srtt_us >> 2;
2858 if (tp->packets_out == 1)
2859 timeout_us += tcp_rto_min_us(sk);
2860 else
2861 timeout_us += TCP_TIMEOUT_MIN_US;
2862 timeout = usecs_to_jiffies(timeout_us);
2863 } else {
2864 timeout = TCP_TIMEOUT_INIT;
2865 }
2866
2867 /* If the RTO formula yields an earlier time, then use that time. */
2868 rto_delta_us = advancing_rto ?
2869 jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
2870 tcp_rto_delta_us(sk); /* How far in future is RTO? */
2871 if (rto_delta_us > 0)
2872 timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
2873
2874 tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, TCP_RTO_MAX);
2875 return true;
2876}
2877
2878/* Thanks to skb fast clones, we can detect if a prior transmit of
2879 * a packet is still in a qdisc or driver queue.
2880 * In this case, there is very little point doing a retransmit !
2881 */
2882static bool skb_still_in_host_queue(struct sock *sk,
2883 const struct sk_buff *skb)
2884{
2885 if (unlikely(skb_fclone_busy(sk, skb))) {
2886 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2887 smp_mb__after_atomic();
2888 if (skb_fclone_busy(sk, skb)) {
2889 NET_INC_STATS(sock_net(sk),
2890 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2891 return true;
2892 }
2893 }
2894 return false;
2895}
2896
2897/* When probe timeout (PTO) fires, try send a new segment if possible, else
2898 * retransmit the last segment.
2899 */
2900void tcp_send_loss_probe(struct sock *sk)
2901{
2902 struct tcp_sock *tp = tcp_sk(sk);
2903 struct sk_buff *skb;
2904 int pcount;
2905 int mss = tcp_current_mss(sk);
2906
2907 /* At most one outstanding TLP */
2908 if (tp->tlp_high_seq)
2909 goto rearm_timer;
2910
2911 tp->tlp_retrans = 0;
2912 skb = tcp_send_head(sk);
2913 if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
2914 pcount = tp->packets_out;
2915 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2916 if (tp->packets_out > pcount)
2917 goto probe_sent;
2918 goto rearm_timer;
2919 }
2920 skb = skb_rb_last(&sk->tcp_rtx_queue);
2921 if (unlikely(!skb)) {
2922 WARN_ONCE(tp->packets_out,
2923 "invalid inflight: %u state %u cwnd %u mss %d\n",
2924 tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss);
2925 inet_csk(sk)->icsk_pending = 0;
2926 return;
2927 }
2928
2929 if (skb_still_in_host_queue(sk, skb))
2930 goto rearm_timer;
2931
2932 pcount = tcp_skb_pcount(skb);
2933 if (WARN_ON(!pcount))
2934 goto rearm_timer;
2935
2936 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2937 if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
2938 (pcount - 1) * mss, mss,
2939 GFP_ATOMIC)))
2940 goto rearm_timer;
2941 skb = skb_rb_next(skb);
2942 }
2943
2944 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2945 goto rearm_timer;
2946
2947 if (__tcp_retransmit_skb(sk, skb, 1))
2948 goto rearm_timer;
2949
2950 tp->tlp_retrans = 1;
2951
2952probe_sent:
2953 /* Record snd_nxt for loss detection. */
2954 tp->tlp_high_seq = tp->snd_nxt;
2955
2956 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2957 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2958 inet_csk(sk)->icsk_pending = 0;
2959rearm_timer:
2960 tcp_rearm_rto(sk);
2961}
2962
2963/* Push out any pending frames which were held back due to
2964 * TCP_CORK or attempt at coalescing tiny packets.
2965 * The socket must be locked by the caller.
2966 */
2967void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2968 int nonagle)
2969{
2970 /* If we are closed, the bytes will have to remain here.
2971 * In time closedown will finish, we empty the write queue and
2972 * all will be happy.
2973 */
2974 if (unlikely(sk->sk_state == TCP_CLOSE))
2975 return;
2976
2977 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2978 sk_gfp_mask(sk, GFP_ATOMIC)))
2979 tcp_check_probe_timer(sk);
2980}
2981
2982/* Send _single_ skb sitting at the send head. This function requires
2983 * true push pending frames to setup probe timer etc.
2984 */
2985void tcp_push_one(struct sock *sk, unsigned int mss_now)
2986{
2987 struct sk_buff *skb = tcp_send_head(sk);
2988
2989 BUG_ON(!skb || skb->len < mss_now);
2990
2991 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2992}
2993
2994/* This function returns the amount that we can raise the
2995 * usable window based on the following constraints
2996 *
2997 * 1. The window can never be shrunk once it is offered (RFC 793)
2998 * 2. We limit memory per socket
2999 *
3000 * RFC 1122:
3001 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
3002 * RECV.NEXT + RCV.WIN fixed until:
3003 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
3004 *
3005 * i.e. don't raise the right edge of the window until you can raise
3006 * it at least MSS bytes.
3007 *
3008 * Unfortunately, the recommended algorithm breaks header prediction,
3009 * since header prediction assumes th->window stays fixed.
3010 *
3011 * Strictly speaking, keeping th->window fixed violates the receiver
3012 * side SWS prevention criteria. The problem is that under this rule
3013 * a stream of single byte packets will cause the right side of the
3014 * window to always advance by a single byte.
3015 *
3016 * Of course, if the sender implements sender side SWS prevention
3017 * then this will not be a problem.
3018 *
3019 * BSD seems to make the following compromise:
3020 *
3021 * If the free space is less than the 1/4 of the maximum
3022 * space available and the free space is less than 1/2 mss,
3023 * then set the window to 0.
3024 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
3025 * Otherwise, just prevent the window from shrinking
3026 * and from being larger than the largest representable value.
3027 *
3028 * This prevents incremental opening of the window in the regime
3029 * where TCP is limited by the speed of the reader side taking
3030 * data out of the TCP receive queue. It does nothing about
3031 * those cases where the window is constrained on the sender side
3032 * because the pipeline is full.
3033 *
3034 * BSD also seems to "accidentally" limit itself to windows that are a
3035 * multiple of MSS, at least until the free space gets quite small.
3036 * This would appear to be a side effect of the mbuf implementation.
3037 * Combining these two algorithms results in the observed behavior
3038 * of having a fixed window size at almost all times.
3039 *
3040 * Below we obtain similar behavior by forcing the offered window to
3041 * a multiple of the mss when it is feasible to do so.
3042 *
3043 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
3044 * Regular options like TIMESTAMP are taken into account.
3045 */
3046u32 __tcp_select_window(struct sock *sk)
3047{
3048 struct inet_connection_sock *icsk = inet_csk(sk);
3049 struct tcp_sock *tp = tcp_sk(sk);
3050 struct net *net = sock_net(sk);
3051 /* MSS for the peer's data. Previous versions used mss_clamp
3052 * here. I don't know if the value based on our guesses
3053 * of peer's MSS is better for the performance. It's more correct
3054 * but may be worse for the performance because of rcv_mss
3055 * fluctuations. --SAW 1998/11/1
3056 */
3057 int mss = icsk->icsk_ack.rcv_mss;
3058 int free_space = tcp_space(sk);
3059 int allowed_space = tcp_full_space(sk);
3060 int full_space, window;
3061
3062 if (sk_is_mptcp(sk))
3063 mptcp_space(sk, &free_space, &allowed_space);
3064
3065 full_space = min_t(int, tp->window_clamp, allowed_space);
3066
3067 if (unlikely(mss > full_space)) {
3068 mss = full_space;
3069 if (mss <= 0)
3070 return 0;
3071 }
3072
3073 /* Only allow window shrink if the sysctl is enabled and we have
3074 * a non-zero scaling factor in effect.
3075 */
3076 if (READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) && tp->rx_opt.rcv_wscale)
3077 goto shrink_window_allowed;
3078
3079 /* do not allow window to shrink */
3080
3081 if (free_space < (full_space >> 1)) {
3082 icsk->icsk_ack.quick = 0;
3083
3084 if (tcp_under_memory_pressure(sk))
3085 tcp_adjust_rcv_ssthresh(sk);
3086
3087 /* free_space might become our new window, make sure we don't
3088 * increase it due to wscale.
3089 */
3090 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
3091
3092 /* if free space is less than mss estimate, or is below 1/16th
3093 * of the maximum allowed, try to move to zero-window, else
3094 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
3095 * new incoming data is dropped due to memory limits.
3096 * With large window, mss test triggers way too late in order
3097 * to announce zero window in time before rmem limit kicks in.
3098 */
3099 if (free_space < (allowed_space >> 4) || free_space < mss)
3100 return 0;
3101 }
3102
3103 if (free_space > tp->rcv_ssthresh)
3104 free_space = tp->rcv_ssthresh;
3105
3106 /* Don't do rounding if we are using window scaling, since the
3107 * scaled window will not line up with the MSS boundary anyway.
3108 */
3109 if (tp->rx_opt.rcv_wscale) {
3110 window = free_space;
3111
3112 /* Advertise enough space so that it won't get scaled away.
3113 * Import case: prevent zero window announcement if
3114 * 1<<rcv_wscale > mss.
3115 */
3116 window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
3117 } else {
3118 window = tp->rcv_wnd;
3119 /* Get the largest window that is a nice multiple of mss.
3120 * Window clamp already applied above.
3121 * If our current window offering is within 1 mss of the
3122 * free space we just keep it. This prevents the divide
3123 * and multiply from happening most of the time.
3124 * We also don't do any window rounding when the free space
3125 * is too small.
3126 */
3127 if (window <= free_space - mss || window > free_space)
3128 window = rounddown(free_space, mss);
3129 else if (mss == full_space &&
3130 free_space > window + (full_space >> 1))
3131 window = free_space;
3132 }
3133
3134 return window;
3135
3136shrink_window_allowed:
3137 /* new window should always be an exact multiple of scaling factor */
3138 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
3139
3140 if (free_space < (full_space >> 1)) {
3141 icsk->icsk_ack.quick = 0;
3142
3143 if (tcp_under_memory_pressure(sk))
3144 tcp_adjust_rcv_ssthresh(sk);
3145
3146 /* if free space is too low, return a zero window */
3147 if (free_space < (allowed_space >> 4) || free_space < mss ||
3148 free_space < (1 << tp->rx_opt.rcv_wscale))
3149 return 0;
3150 }
3151
3152 if (free_space > tp->rcv_ssthresh) {
3153 free_space = tp->rcv_ssthresh;
3154 /* new window should always be an exact multiple of scaling factor
3155 *
3156 * For this case, we ALIGN "up" (increase free_space) because
3157 * we know free_space is not zero here, it has been reduced from
3158 * the memory-based limit, and rcv_ssthresh is not a hard limit
3159 * (unlike sk_rcvbuf).
3160 */
3161 free_space = ALIGN(free_space, (1 << tp->rx_opt.rcv_wscale));
3162 }
3163
3164 return free_space;
3165}
3166
3167void tcp_skb_collapse_tstamp(struct sk_buff *skb,
3168 const struct sk_buff *next_skb)
3169{
3170 if (unlikely(tcp_has_tx_tstamp(next_skb))) {
3171 const struct skb_shared_info *next_shinfo =
3172 skb_shinfo(next_skb);
3173 struct skb_shared_info *shinfo = skb_shinfo(skb);
3174
3175 shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
3176 shinfo->tskey = next_shinfo->tskey;
3177 TCP_SKB_CB(skb)->txstamp_ack |=
3178 TCP_SKB_CB(next_skb)->txstamp_ack;
3179 }
3180}
3181
3182/* Collapses two adjacent SKB's during retransmission. */
3183static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
3184{
3185 struct tcp_sock *tp = tcp_sk(sk);
3186 struct sk_buff *next_skb = skb_rb_next(skb);
3187 int next_skb_size;
3188
3189 next_skb_size = next_skb->len;
3190
3191 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
3192
3193 if (next_skb_size && !tcp_skb_shift(skb, next_skb, 1, next_skb_size))
3194 return false;
3195
3196 tcp_highest_sack_replace(sk, next_skb, skb);
3197
3198 /* Update sequence range on original skb. */
3199 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
3200
3201 /* Merge over control information. This moves PSH/FIN etc. over */
3202 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
3203
3204 /* All done, get rid of second SKB and account for it so
3205 * packet counting does not break.
3206 */
3207 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
3208 TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
3209
3210 /* changed transmit queue under us so clear hints */
3211 tcp_clear_retrans_hints_partial(tp);
3212 if (next_skb == tp->retransmit_skb_hint)
3213 tp->retransmit_skb_hint = skb;
3214
3215 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
3216
3217 tcp_skb_collapse_tstamp(skb, next_skb);
3218
3219 tcp_rtx_queue_unlink_and_free(next_skb, sk);
3220 return true;
3221}
3222
3223/* Check if coalescing SKBs is legal. */
3224static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
3225{
3226 if (tcp_skb_pcount(skb) > 1)
3227 return false;
3228 if (skb_cloned(skb))
3229 return false;
3230 /* Some heuristics for collapsing over SACK'd could be invented */
3231 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
3232 return false;
3233
3234 return true;
3235}
3236
3237/* Collapse packets in the retransmit queue to make to create
3238 * less packets on the wire. This is only done on retransmission.
3239 */
3240static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
3241 int space)
3242{
3243 struct tcp_sock *tp = tcp_sk(sk);
3244 struct sk_buff *skb = to, *tmp;
3245 bool first = true;
3246
3247 if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse))
3248 return;
3249 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3250 return;
3251
3252 skb_rbtree_walk_from_safe(skb, tmp) {
3253 if (!tcp_can_collapse(sk, skb))
3254 break;
3255
3256 if (!tcp_skb_can_collapse(to, skb))
3257 break;
3258
3259 space -= skb->len;
3260
3261 if (first) {
3262 first = false;
3263 continue;
3264 }
3265
3266 if (space < 0)
3267 break;
3268
3269 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
3270 break;
3271
3272 if (!tcp_collapse_retrans(sk, to))
3273 break;
3274 }
3275}
3276
3277/* This retransmits one SKB. Policy decisions and retransmit queue
3278 * state updates are done by the caller. Returns non-zero if an
3279 * error occurred which prevented the send.
3280 */
3281int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3282{
3283 struct inet_connection_sock *icsk = inet_csk(sk);
3284 struct tcp_sock *tp = tcp_sk(sk);
3285 unsigned int cur_mss;
3286 int diff, len, err;
3287 int avail_wnd;
3288
3289 /* Inconclusive MTU probe */
3290 if (icsk->icsk_mtup.probe_size)
3291 icsk->icsk_mtup.probe_size = 0;
3292
3293 if (skb_still_in_host_queue(sk, skb))
3294 return -EBUSY;
3295
3296start:
3297 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
3298 if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3299 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
3300 TCP_SKB_CB(skb)->seq++;
3301 goto start;
3302 }
3303 if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
3304 WARN_ON_ONCE(1);
3305 return -EINVAL;
3306 }
3307 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3308 return -ENOMEM;
3309 }
3310
3311 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3312 return -EHOSTUNREACH; /* Routing failure or similar. */
3313
3314 cur_mss = tcp_current_mss(sk);
3315 avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3316
3317 /* If receiver has shrunk his window, and skb is out of
3318 * new window, do not retransmit it. The exception is the
3319 * case, when window is shrunk to zero. In this case
3320 * our retransmit of one segment serves as a zero window probe.
3321 */
3322 if (avail_wnd <= 0) {
3323 if (TCP_SKB_CB(skb)->seq != tp->snd_una)
3324 return -EAGAIN;
3325 avail_wnd = cur_mss;
3326 }
3327
3328 len = cur_mss * segs;
3329 if (len > avail_wnd) {
3330 len = rounddown(avail_wnd, cur_mss);
3331 if (!len)
3332 len = avail_wnd;
3333 }
3334 if (skb->len > len) {
3335 if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
3336 cur_mss, GFP_ATOMIC))
3337 return -ENOMEM; /* We'll try again later. */
3338 } else {
3339 if (skb_unclone_keeptruesize(skb, GFP_ATOMIC))
3340 return -ENOMEM;
3341
3342 diff = tcp_skb_pcount(skb);
3343 tcp_set_skb_tso_segs(skb, cur_mss);
3344 diff -= tcp_skb_pcount(skb);
3345 if (diff)
3346 tcp_adjust_pcount(sk, skb, diff);
3347 avail_wnd = min_t(int, avail_wnd, cur_mss);
3348 if (skb->len < avail_wnd)
3349 tcp_retrans_try_collapse(sk, skb, avail_wnd);
3350 }
3351
3352 /* RFC3168, section 6.1.1.1. ECN fallback */
3353 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
3354 tcp_ecn_clear_syn(sk, skb);
3355
3356 /* Update global and local TCP statistics. */
3357 segs = tcp_skb_pcount(skb);
3358 TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
3359 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3360 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3361 tp->total_retrans += segs;
3362 tp->bytes_retrans += skb->len;
3363
3364 /* make sure skb->data is aligned on arches that require it
3365 * and check if ack-trimming & collapsing extended the headroom
3366 * beyond what csum_start can cover.
3367 */
3368 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
3369 skb_headroom(skb) >= 0xFFFF)) {
3370 struct sk_buff *nskb;
3371
3372 tcp_skb_tsorted_save(skb) {
3373 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
3374 if (nskb) {
3375 nskb->dev = NULL;
3376 err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC);
3377 } else {
3378 err = -ENOBUFS;
3379 }
3380 } tcp_skb_tsorted_restore(skb);
3381
3382 if (!err) {
3383 tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns);
3384 tcp_rate_skb_sent(sk, skb);
3385 }
3386 } else {
3387 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3388 }
3389
3390 /* To avoid taking spuriously low RTT samples based on a timestamp
3391 * for a transmit that never happened, always mark EVER_RETRANS
3392 */
3393 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
3394
3395 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
3396 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
3397 TCP_SKB_CB(skb)->seq, segs, err);
3398
3399 if (likely(!err)) {
3400 trace_tcp_retransmit_skb(sk, skb);
3401 } else if (err != -EBUSY) {
3402 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
3403 }
3404 return err;
3405}
3406
3407int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3408{
3409 struct tcp_sock *tp = tcp_sk(sk);
3410 int err = __tcp_retransmit_skb(sk, skb, segs);
3411
3412 if (err == 0) {
3413#if FASTRETRANS_DEBUG > 0
3414 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
3415 net_dbg_ratelimited("retrans_out leaked\n");
3416 }
3417#endif
3418 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
3419 tp->retrans_out += tcp_skb_pcount(skb);
3420 }
3421
3422 /* Save stamp of the first (attempted) retransmit. */
3423 if (!tp->retrans_stamp)
3424 tp->retrans_stamp = tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb);
3425
3426 if (tp->undo_retrans < 0)
3427 tp->undo_retrans = 0;
3428 tp->undo_retrans += tcp_skb_pcount(skb);
3429 return err;
3430}
3431
3432/* This gets called after a retransmit timeout, and the initially
3433 * retransmitted data is acknowledged. It tries to continue
3434 * resending the rest of the retransmit queue, until either
3435 * we've sent it all or the congestion window limit is reached.
3436 */
3437void tcp_xmit_retransmit_queue(struct sock *sk)
3438{
3439 const struct inet_connection_sock *icsk = inet_csk(sk);
3440 struct sk_buff *skb, *rtx_head, *hole = NULL;
3441 struct tcp_sock *tp = tcp_sk(sk);
3442 bool rearm_timer = false;
3443 u32 max_segs;
3444 int mib_idx;
3445
3446 if (!tp->packets_out)
3447 return;
3448
3449 rtx_head = tcp_rtx_queue_head(sk);
3450 skb = tp->retransmit_skb_hint ?: rtx_head;
3451 max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
3452 skb_rbtree_walk_from(skb) {
3453 __u8 sacked;
3454 int segs;
3455
3456 if (tcp_pacing_check(sk))
3457 break;
3458
3459 /* we could do better than to assign each time */
3460 if (!hole)
3461 tp->retransmit_skb_hint = skb;
3462
3463 segs = tcp_snd_cwnd(tp) - tcp_packets_in_flight(tp);
3464 if (segs <= 0)
3465 break;
3466 sacked = TCP_SKB_CB(skb)->sacked;
3467 /* In case tcp_shift_skb_data() have aggregated large skbs,
3468 * we need to make sure not sending too bigs TSO packets
3469 */
3470 segs = min_t(int, segs, max_segs);
3471
3472 if (tp->retrans_out >= tp->lost_out) {
3473 break;
3474 } else if (!(sacked & TCPCB_LOST)) {
3475 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
3476 hole = skb;
3477 continue;
3478
3479 } else {
3480 if (icsk->icsk_ca_state != TCP_CA_Loss)
3481 mib_idx = LINUX_MIB_TCPFASTRETRANS;
3482 else
3483 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
3484 }
3485
3486 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
3487 continue;
3488
3489 if (tcp_small_queue_check(sk, skb, 1))
3490 break;
3491
3492 if (tcp_retransmit_skb(sk, skb, segs))
3493 break;
3494
3495 NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
3496
3497 if (tcp_in_cwnd_reduction(sk))
3498 tp->prr_out += tcp_skb_pcount(skb);
3499
3500 if (skb == rtx_head &&
3501 icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3502 rearm_timer = true;
3503
3504 }
3505 if (rearm_timer)
3506 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3507 inet_csk(sk)->icsk_rto,
3508 TCP_RTO_MAX);
3509}
3510
3511/* We allow to exceed memory limits for FIN packets to expedite
3512 * connection tear down and (memory) recovery.
3513 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3514 * or even be forced to close flow without any FIN.
3515 * In general, we want to allow one skb per socket to avoid hangs
3516 * with edge trigger epoll()
3517 */
3518void sk_forced_mem_schedule(struct sock *sk, int size)
3519{
3520 int delta, amt;
3521
3522 delta = size - sk->sk_forward_alloc;
3523 if (delta <= 0)
3524 return;
3525 amt = sk_mem_pages(delta);
3526 sk_forward_alloc_add(sk, amt << PAGE_SHIFT);
3527 sk_memory_allocated_add(sk, amt);
3528
3529 if (mem_cgroup_sockets_enabled && sk->sk_memcg)
3530 mem_cgroup_charge_skmem(sk->sk_memcg, amt,
3531 gfp_memcg_charge() | __GFP_NOFAIL);
3532}
3533
3534/* Send a FIN. The caller locks the socket for us.
3535 * We should try to send a FIN packet really hard, but eventually give up.
3536 */
3537void tcp_send_fin(struct sock *sk)
3538{
3539 struct sk_buff *skb, *tskb, *tail = tcp_write_queue_tail(sk);
3540 struct tcp_sock *tp = tcp_sk(sk);
3541
3542 /* Optimization, tack on the FIN if we have one skb in write queue and
3543 * this skb was not yet sent, or we are under memory pressure.
3544 * Note: in the latter case, FIN packet will be sent after a timeout,
3545 * as TCP stack thinks it has already been transmitted.
3546 */
3547 tskb = tail;
3548 if (!tskb && tcp_under_memory_pressure(sk))
3549 tskb = skb_rb_last(&sk->tcp_rtx_queue);
3550
3551 if (tskb) {
3552 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
3553 TCP_SKB_CB(tskb)->end_seq++;
3554 tp->write_seq++;
3555 if (!tail) {
3556 /* This means tskb was already sent.
3557 * Pretend we included the FIN on previous transmit.
3558 * We need to set tp->snd_nxt to the value it would have
3559 * if FIN had been sent. This is because retransmit path
3560 * does not change tp->snd_nxt.
3561 */
3562 WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1);
3563 return;
3564 }
3565 } else {
3566 skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
3567 if (unlikely(!skb))
3568 return;
3569
3570 INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3571 skb_reserve(skb, MAX_TCP_HEADER);
3572 sk_forced_mem_schedule(sk, skb->truesize);
3573 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3574 tcp_init_nondata_skb(skb, tp->write_seq,
3575 TCPHDR_ACK | TCPHDR_FIN);
3576 tcp_queue_skb(sk, skb);
3577 }
3578 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
3579}
3580
3581/* We get here when a process closes a file descriptor (either due to
3582 * an explicit close() or as a byproduct of exit()'ing) and there
3583 * was unread data in the receive queue. This behavior is recommended
3584 * by RFC 2525, section 2.17. -DaveM
3585 */
3586void tcp_send_active_reset(struct sock *sk, gfp_t priority)
3587{
3588 struct sk_buff *skb;
3589
3590 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
3591
3592 /* NOTE: No TCP options attached and we never retransmit this. */
3593 skb = alloc_skb(MAX_TCP_HEADER, priority);
3594 if (!skb) {
3595 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3596 return;
3597 }
3598
3599 /* Reserve space for headers and prepare control bits. */
3600 skb_reserve(skb, MAX_TCP_HEADER);
3601 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
3602 TCPHDR_ACK | TCPHDR_RST);
3603 tcp_mstamp_refresh(tcp_sk(sk));
3604 /* Send it off. */
3605 if (tcp_transmit_skb(sk, skb, 0, priority))
3606 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3607
3608 /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3609 * skb here is different to the troublesome skb, so use NULL
3610 */
3611 trace_tcp_send_reset(sk, NULL);
3612}
3613
3614/* Send a crossed SYN-ACK during socket establishment.
3615 * WARNING: This routine must only be called when we have already sent
3616 * a SYN packet that crossed the incoming SYN that caused this routine
3617 * to get called. If this assumption fails then the initial rcv_wnd
3618 * and rcv_wscale values will not be correct.
3619 */
3620int tcp_send_synack(struct sock *sk)
3621{
3622 struct sk_buff *skb;
3623
3624 skb = tcp_rtx_queue_head(sk);
3625 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3626 pr_err("%s: wrong queue state\n", __func__);
3627 return -EFAULT;
3628 }
3629 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
3630 if (skb_cloned(skb)) {
3631 struct sk_buff *nskb;
3632
3633 tcp_skb_tsorted_save(skb) {
3634 nskb = skb_copy(skb, GFP_ATOMIC);
3635 } tcp_skb_tsorted_restore(skb);
3636 if (!nskb)
3637 return -ENOMEM;
3638 INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3639 tcp_highest_sack_replace(sk, skb, nskb);
3640 tcp_rtx_queue_unlink_and_free(skb, sk);
3641 __skb_header_release(nskb);
3642 tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3643 sk_wmem_queued_add(sk, nskb->truesize);
3644 sk_mem_charge(sk, nskb->truesize);
3645 skb = nskb;
3646 }
3647
3648 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3649 tcp_ecn_send_synack(sk, skb);
3650 }
3651 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3652}
3653
3654/**
3655 * tcp_make_synack - Allocate one skb and build a SYNACK packet.
3656 * @sk: listener socket
3657 * @dst: dst entry attached to the SYNACK. It is consumed and caller
3658 * should not use it again.
3659 * @req: request_sock pointer
3660 * @foc: cookie for tcp fast open
3661 * @synack_type: Type of synack to prepare
3662 * @syn_skb: SYN packet just received. It could be NULL for rtx case.
3663 */
3664struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3665 struct request_sock *req,
3666 struct tcp_fastopen_cookie *foc,
3667 enum tcp_synack_type synack_type,
3668 struct sk_buff *syn_skb)
3669{
3670 struct inet_request_sock *ireq = inet_rsk(req);
3671 const struct tcp_sock *tp = tcp_sk(sk);
3672 struct tcp_out_options opts;
3673 struct tcp_key key = {};
3674 struct sk_buff *skb;
3675 int tcp_header_size;
3676 struct tcphdr *th;
3677 int mss;
3678 u64 now;
3679
3680 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3681 if (unlikely(!skb)) {
3682 dst_release(dst);
3683 return NULL;
3684 }
3685 /* Reserve space for headers. */
3686 skb_reserve(skb, MAX_TCP_HEADER);
3687
3688 switch (synack_type) {
3689 case TCP_SYNACK_NORMAL:
3690 skb_set_owner_w(skb, req_to_sk(req));
3691 break;
3692 case TCP_SYNACK_COOKIE:
3693 /* Under synflood, we do not attach skb to a socket,
3694 * to avoid false sharing.
3695 */
3696 break;
3697 case TCP_SYNACK_FASTOPEN:
3698 /* sk is a const pointer, because we want to express multiple
3699 * cpu might call us concurrently.
3700 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3701 */
3702 skb_set_owner_w(skb, (struct sock *)sk);
3703 break;
3704 }
3705 skb_dst_set(skb, dst);
3706
3707 mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3708
3709 memset(&opts, 0, sizeof(opts));
3710 now = tcp_clock_ns();
3711#ifdef CONFIG_SYN_COOKIES
3712 if (unlikely(synack_type == TCP_SYNACK_COOKIE && ireq->tstamp_ok))
3713 skb_set_delivery_time(skb, cookie_init_timestamp(req, now),
3714 true);
3715 else
3716#endif
3717 {
3718 skb_set_delivery_time(skb, now, true);
3719 if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */
3720 tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);
3721 }
3722
3723#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
3724 rcu_read_lock();
3725#endif
3726 if (tcp_rsk_used_ao(req)) {
3727#ifdef CONFIG_TCP_AO
3728 struct tcp_ao_key *ao_key = NULL;
3729 u8 keyid = tcp_rsk(req)->ao_keyid;
3730
3731 ao_key = tcp_sk(sk)->af_specific->ao_lookup(sk, req_to_sk(req),
3732 keyid, -1);
3733 /* If there is no matching key - avoid sending anything,
3734 * especially usigned segments. It could try harder and lookup
3735 * for another peer-matching key, but the peer has requested
3736 * ao_keyid (RFC5925 RNextKeyID), so let's keep it simple here.
3737 */
3738 if (unlikely(!ao_key)) {
3739 rcu_read_unlock();
3740 kfree_skb(skb);
3741 net_warn_ratelimited("TCP-AO: the keyid %u from SYN packet is not present - not sending SYNACK\n",
3742 keyid);
3743 return NULL;
3744 }
3745 key.ao_key = ao_key;
3746 key.type = TCP_KEY_AO;
3747#endif
3748 } else {
3749#ifdef CONFIG_TCP_MD5SIG
3750 key.md5_key = tcp_rsk(req)->af_specific->req_md5_lookup(sk,
3751 req_to_sk(req));
3752 if (key.md5_key)
3753 key.type = TCP_KEY_MD5;
3754#endif
3755 }
3756 skb_set_hash(skb, READ_ONCE(tcp_rsk(req)->txhash), PKT_HASH_TYPE_L4);
3757 /* bpf program will be interested in the tcp_flags */
3758 TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK;
3759 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts,
3760 &key, foc, synack_type, syn_skb)
3761 + sizeof(*th);
3762
3763 skb_push(skb, tcp_header_size);
3764 skb_reset_transport_header(skb);
3765
3766 th = (struct tcphdr *)skb->data;
3767 memset(th, 0, sizeof(struct tcphdr));
3768 th->syn = 1;
3769 th->ack = 1;
3770 tcp_ecn_make_synack(req, th);
3771 th->source = htons(ireq->ir_num);
3772 th->dest = ireq->ir_rmt_port;
3773 skb->mark = ireq->ir_mark;
3774 skb->ip_summed = CHECKSUM_PARTIAL;
3775 th->seq = htonl(tcp_rsk(req)->snt_isn);
3776 /* XXX data is queued and acked as is. No buffer/window check */
3777 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
3778
3779 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3780 th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3781 tcp_options_write(th, NULL, tcp_rsk(req), &opts, &key);
3782 th->doff = (tcp_header_size >> 2);
3783 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3784
3785 /* Okay, we have all we need - do the md5 hash if needed */
3786 if (tcp_key_is_md5(&key)) {
3787#ifdef CONFIG_TCP_MD5SIG
3788 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3789 key.md5_key, req_to_sk(req), skb);
3790#endif
3791 } else if (tcp_key_is_ao(&key)) {
3792#ifdef CONFIG_TCP_AO
3793 tcp_rsk(req)->af_specific->ao_synack_hash(opts.hash_location,
3794 key.ao_key, req, skb,
3795 opts.hash_location - (u8 *)th, 0);
3796#endif
3797 }
3798#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
3799 rcu_read_unlock();
3800#endif
3801
3802 bpf_skops_write_hdr_opt((struct sock *)sk, skb, req, syn_skb,
3803 synack_type, &opts);
3804
3805 skb_set_delivery_time(skb, now, true);
3806 tcp_add_tx_delay(skb, tp);
3807
3808 return skb;
3809}
3810EXPORT_SYMBOL(tcp_make_synack);
3811
3812static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
3813{
3814 struct inet_connection_sock *icsk = inet_csk(sk);
3815 const struct tcp_congestion_ops *ca;
3816 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
3817
3818 if (ca_key == TCP_CA_UNSPEC)
3819 return;
3820
3821 rcu_read_lock();
3822 ca = tcp_ca_find_key(ca_key);
3823 if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
3824 bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
3825 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
3826 icsk->icsk_ca_ops = ca;
3827 }
3828 rcu_read_unlock();
3829}
3830
3831/* Do all connect socket setups that can be done AF independent. */
3832static void tcp_connect_init(struct sock *sk)
3833{
3834 const struct dst_entry *dst = __sk_dst_get(sk);
3835 struct tcp_sock *tp = tcp_sk(sk);
3836 __u8 rcv_wscale;
3837 u32 rcv_wnd;
3838
3839 /* We'll fix this up when we get a response from the other end.
3840 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3841 */
3842 tp->tcp_header_len = sizeof(struct tcphdr);
3843 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps))
3844 tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
3845
3846 tcp_ao_connect_init(sk);
3847
3848 /* If user gave his TCP_MAXSEG, record it to clamp */
3849 if (tp->rx_opt.user_mss)
3850 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3851 tp->max_window = 0;
3852 tcp_mtup_init(sk);
3853 tcp_sync_mss(sk, dst_mtu(dst));
3854
3855 tcp_ca_dst_init(sk, dst);
3856
3857 if (!tp->window_clamp)
3858 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3859 tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3860
3861 tcp_initialize_rcv_mss(sk);
3862
3863 /* limit the window selection if the user enforce a smaller rx buffer */
3864 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
3865 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
3866 tp->window_clamp = tcp_full_space(sk);
3867
3868 rcv_wnd = tcp_rwnd_init_bpf(sk);
3869 if (rcv_wnd == 0)
3870 rcv_wnd = dst_metric(dst, RTAX_INITRWND);
3871
3872 tcp_select_initial_window(sk, tcp_full_space(sk),
3873 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
3874 &tp->rcv_wnd,
3875 &tp->window_clamp,
3876 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_window_scaling),
3877 &rcv_wscale,
3878 rcv_wnd);
3879
3880 tp->rx_opt.rcv_wscale = rcv_wscale;
3881 tp->rcv_ssthresh = tp->rcv_wnd;
3882
3883 WRITE_ONCE(sk->sk_err, 0);
3884 sock_reset_flag(sk, SOCK_DONE);
3885 tp->snd_wnd = 0;
3886 tcp_init_wl(tp, 0);
3887 tcp_write_queue_purge(sk);
3888 tp->snd_una = tp->write_seq;
3889 tp->snd_sml = tp->write_seq;
3890 tp->snd_up = tp->write_seq;
3891 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3892
3893 if (likely(!tp->repair))
3894 tp->rcv_nxt = 0;
3895 else
3896 tp->rcv_tstamp = tcp_jiffies32;
3897 tp->rcv_wup = tp->rcv_nxt;
3898 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
3899
3900 inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3901 inet_csk(sk)->icsk_retransmits = 0;
3902 tcp_clear_retrans(tp);
3903}
3904
3905static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
3906{
3907 struct tcp_sock *tp = tcp_sk(sk);
3908 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
3909
3910 tcb->end_seq += skb->len;
3911 __skb_header_release(skb);
3912 sk_wmem_queued_add(sk, skb->truesize);
3913 sk_mem_charge(sk, skb->truesize);
3914 WRITE_ONCE(tp->write_seq, tcb->end_seq);
3915 tp->packets_out += tcp_skb_pcount(skb);
3916}
3917
3918/* Build and send a SYN with data and (cached) Fast Open cookie. However,
3919 * queue a data-only packet after the regular SYN, such that regular SYNs
3920 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3921 * only the SYN sequence, the data are retransmitted in the first ACK.
3922 * If cookie is not cached or other error occurs, falls back to send a
3923 * regular SYN with Fast Open cookie request option.
3924 */
3925static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
3926{
3927 struct inet_connection_sock *icsk = inet_csk(sk);
3928 struct tcp_sock *tp = tcp_sk(sk);
3929 struct tcp_fastopen_request *fo = tp->fastopen_req;
3930 struct page_frag *pfrag = sk_page_frag(sk);
3931 struct sk_buff *syn_data;
3932 int space, err = 0;
3933
3934 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
3935 if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3936 goto fallback;
3937
3938 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3939 * user-MSS. Reserve maximum option space for middleboxes that add
3940 * private TCP options. The cost is reduced data space in SYN :(
3941 */
3942 tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
3943 /* Sync mss_cache after updating the mss_clamp */
3944 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
3945
3946 space = __tcp_mtu_to_mss(sk, icsk->icsk_pmtu_cookie) -
3947 MAX_TCP_OPTION_SPACE;
3948
3949 space = min_t(size_t, space, fo->size);
3950
3951 if (space &&
3952 !skb_page_frag_refill(min_t(size_t, space, PAGE_SIZE),
3953 pfrag, sk->sk_allocation))
3954 goto fallback;
3955 syn_data = tcp_stream_alloc_skb(sk, sk->sk_allocation, false);
3956 if (!syn_data)
3957 goto fallback;
3958 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3959 if (space) {
3960 space = min_t(size_t, space, pfrag->size - pfrag->offset);
3961 space = tcp_wmem_schedule(sk, space);
3962 }
3963 if (space) {
3964 space = copy_page_from_iter(pfrag->page, pfrag->offset,
3965 space, &fo->data->msg_iter);
3966 if (unlikely(!space)) {
3967 tcp_skb_tsorted_anchor_cleanup(syn_data);
3968 kfree_skb(syn_data);
3969 goto fallback;
3970 }
3971 skb_fill_page_desc(syn_data, 0, pfrag->page,
3972 pfrag->offset, space);
3973 page_ref_inc(pfrag->page);
3974 pfrag->offset += space;
3975 skb_len_add(syn_data, space);
3976 skb_zcopy_set(syn_data, fo->uarg, NULL);
3977 }
3978 /* No more data pending in inet_wait_for_connect() */
3979 if (space == fo->size)
3980 fo->data = NULL;
3981 fo->copied = space;
3982
3983 tcp_connect_queue_skb(sk, syn_data);
3984 if (syn_data->len)
3985 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3986
3987 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3988
3989 skb_set_delivery_time(syn, syn_data->skb_mstamp_ns, true);
3990
3991 /* Now full SYN+DATA was cloned and sent (or not),
3992 * remove the SYN from the original skb (syn_data)
3993 * we keep in write queue in case of a retransmit, as we
3994 * also have the SYN packet (with no data) in the same queue.
3995 */
3996 TCP_SKB_CB(syn_data)->seq++;
3997 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
3998 if (!err) {
3999 tp->syn_data = (fo->copied > 0);
4000 tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
4001 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
4002 goto done;
4003 }
4004
4005 /* data was not sent, put it in write_queue */
4006 __skb_queue_tail(&sk->sk_write_queue, syn_data);
4007 tp->packets_out -= tcp_skb_pcount(syn_data);
4008
4009fallback:
4010 /* Send a regular SYN with Fast Open cookie request option */
4011 if (fo->cookie.len > 0)
4012 fo->cookie.len = 0;
4013 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
4014 if (err)
4015 tp->syn_fastopen = 0;
4016done:
4017 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
4018 return err;
4019}
4020
4021/* Build a SYN and send it off. */
4022int tcp_connect(struct sock *sk)
4023{
4024 struct tcp_sock *tp = tcp_sk(sk);
4025 struct sk_buff *buff;
4026 int err;
4027
4028 tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
4029
4030#if defined(CONFIG_TCP_MD5SIG) && defined(CONFIG_TCP_AO)
4031 /* Has to be checked late, after setting daddr/saddr/ops.
4032 * Return error if the peer has both a md5 and a tcp-ao key
4033 * configured as this is ambiguous.
4034 */
4035 if (unlikely(rcu_dereference_protected(tp->md5sig_info,
4036 lockdep_sock_is_held(sk)))) {
4037 bool needs_ao = !!tp->af_specific->ao_lookup(sk, sk, -1, -1);
4038 bool needs_md5 = !!tp->af_specific->md5_lookup(sk, sk);
4039 struct tcp_ao_info *ao_info;
4040
4041 ao_info = rcu_dereference_check(tp->ao_info,
4042 lockdep_sock_is_held(sk));
4043 if (ao_info) {
4044 /* This is an extra check: tcp_ao_required() in
4045 * tcp_v{4,6}_parse_md5_keys() should prevent adding
4046 * md5 keys on ao_required socket.
4047 */
4048 needs_ao |= ao_info->ao_required;
4049 WARN_ON_ONCE(ao_info->ao_required && needs_md5);
4050 }
4051 if (needs_md5 && needs_ao)
4052 return -EKEYREJECTED;
4053
4054 /* If we have a matching md5 key and no matching tcp-ao key
4055 * then free up ao_info if allocated.
4056 */
4057 if (needs_md5) {
4058 tcp_ao_destroy_sock(sk, false);
4059 } else if (needs_ao) {
4060 tcp_clear_md5_list(sk);
4061 kfree(rcu_replace_pointer(tp->md5sig_info, NULL,
4062 lockdep_sock_is_held(sk)));
4063 }
4064 }
4065#endif
4066#ifdef CONFIG_TCP_AO
4067 if (unlikely(rcu_dereference_protected(tp->ao_info,
4068 lockdep_sock_is_held(sk)))) {
4069 /* Don't allow connecting if ao is configured but no
4070 * matching key is found.
4071 */
4072 if (!tp->af_specific->ao_lookup(sk, sk, -1, -1))
4073 return -EKEYREJECTED;
4074 }
4075#endif
4076
4077 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
4078 return -EHOSTUNREACH; /* Routing failure or similar. */
4079
4080 tcp_connect_init(sk);
4081
4082 if (unlikely(tp->repair)) {
4083 tcp_finish_connect(sk, NULL);
4084 return 0;
4085 }
4086
4087 buff = tcp_stream_alloc_skb(sk, sk->sk_allocation, true);
4088 if (unlikely(!buff))
4089 return -ENOBUFS;
4090
4091 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
4092 tcp_mstamp_refresh(tp);
4093 tp->retrans_stamp = tcp_time_stamp_ts(tp);
4094 tcp_connect_queue_skb(sk, buff);
4095 tcp_ecn_send_syn(sk, buff);
4096 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
4097
4098 /* Send off SYN; include data in Fast Open. */
4099 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
4100 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
4101 if (err == -ECONNREFUSED)
4102 return err;
4103
4104 /* We change tp->snd_nxt after the tcp_transmit_skb() call
4105 * in order to make this packet get counted in tcpOutSegs.
4106 */
4107 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
4108 tp->pushed_seq = tp->write_seq;
4109 buff = tcp_send_head(sk);
4110 if (unlikely(buff)) {
4111 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq);
4112 tp->pushed_seq = TCP_SKB_CB(buff)->seq;
4113 }
4114 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
4115
4116 /* Timer for repeating the SYN until an answer. */
4117 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
4118 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
4119 return 0;
4120}
4121EXPORT_SYMBOL(tcp_connect);
4122
4123u32 tcp_delack_max(const struct sock *sk)
4124{
4125 const struct dst_entry *dst = __sk_dst_get(sk);
4126 u32 delack_max = inet_csk(sk)->icsk_delack_max;
4127
4128 if (dst && dst_metric_locked(dst, RTAX_RTO_MIN)) {
4129 u32 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
4130 u32 delack_from_rto_min = max_t(int, 1, rto_min - 1);
4131
4132 delack_max = min_t(u32, delack_max, delack_from_rto_min);
4133 }
4134 return delack_max;
4135}
4136
4137/* Send out a delayed ack, the caller does the policy checking
4138 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
4139 * for details.
4140 */
4141void tcp_send_delayed_ack(struct sock *sk)
4142{
4143 struct inet_connection_sock *icsk = inet_csk(sk);
4144 int ato = icsk->icsk_ack.ato;
4145 unsigned long timeout;
4146
4147 if (ato > TCP_DELACK_MIN) {
4148 const struct tcp_sock *tp = tcp_sk(sk);
4149 int max_ato = HZ / 2;
4150
4151 if (inet_csk_in_pingpong_mode(sk) ||
4152 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
4153 max_ato = TCP_DELACK_MAX;
4154
4155 /* Slow path, intersegment interval is "high". */
4156
4157 /* If some rtt estimate is known, use it to bound delayed ack.
4158 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
4159 * directly.
4160 */
4161 if (tp->srtt_us) {
4162 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
4163 TCP_DELACK_MIN);
4164
4165 if (rtt < max_ato)
4166 max_ato = rtt;
4167 }
4168
4169 ato = min(ato, max_ato);
4170 }
4171
4172 ato = min_t(u32, ato, tcp_delack_max(sk));
4173
4174 /* Stay within the limit we were given */
4175 timeout = jiffies + ato;
4176
4177 /* Use new timeout only if there wasn't a older one earlier. */
4178 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
4179 /* If delack timer is about to expire, send ACK now. */
4180 if (time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
4181 tcp_send_ack(sk);
4182 return;
4183 }
4184
4185 if (!time_before(timeout, icsk->icsk_ack.timeout))
4186 timeout = icsk->icsk_ack.timeout;
4187 }
4188 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
4189 icsk->icsk_ack.timeout = timeout;
4190 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
4191}
4192
4193/* This routine sends an ack and also updates the window. */
4194void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
4195{
4196 struct sk_buff *buff;
4197
4198 /* If we have been reset, we may not send again. */
4199 if (sk->sk_state == TCP_CLOSE)
4200 return;
4201
4202 /* We are not putting this on the write queue, so
4203 * tcp_transmit_skb() will set the ownership to this
4204 * sock.
4205 */
4206 buff = alloc_skb(MAX_TCP_HEADER,
4207 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
4208 if (unlikely(!buff)) {
4209 struct inet_connection_sock *icsk = inet_csk(sk);
4210 unsigned long delay;
4211
4212 delay = TCP_DELACK_MAX << icsk->icsk_ack.retry;
4213 if (delay < TCP_RTO_MAX)
4214 icsk->icsk_ack.retry++;
4215 inet_csk_schedule_ack(sk);
4216 icsk->icsk_ack.ato = TCP_ATO_MIN;
4217 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, delay, TCP_RTO_MAX);
4218 return;
4219 }
4220
4221 /* Reserve space for headers and prepare control bits. */
4222 skb_reserve(buff, MAX_TCP_HEADER);
4223 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
4224
4225 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
4226 * too much.
4227 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
4228 */
4229 skb_set_tcp_pure_ack(buff);
4230
4231 /* Send it off, this clears delayed acks for us. */
4232 __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
4233}
4234EXPORT_SYMBOL_GPL(__tcp_send_ack);
4235
4236void tcp_send_ack(struct sock *sk)
4237{
4238 __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
4239}
4240
4241/* This routine sends a packet with an out of date sequence
4242 * number. It assumes the other end will try to ack it.
4243 *
4244 * Question: what should we make while urgent mode?
4245 * 4.4BSD forces sending single byte of data. We cannot send
4246 * out of window data, because we have SND.NXT==SND.MAX...
4247 *
4248 * Current solution: to send TWO zero-length segments in urgent mode:
4249 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
4250 * out-of-date with SND.UNA-1 to probe window.
4251 */
4252static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
4253{
4254 struct tcp_sock *tp = tcp_sk(sk);
4255 struct sk_buff *skb;
4256
4257 /* We don't queue it, tcp_transmit_skb() sets ownership. */
4258 skb = alloc_skb(MAX_TCP_HEADER,
4259 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
4260 if (!skb)
4261 return -1;
4262
4263 /* Reserve space for headers and set control bits. */
4264 skb_reserve(skb, MAX_TCP_HEADER);
4265 /* Use a previous sequence. This should cause the other
4266 * end to send an ack. Don't queue or clone SKB, just
4267 * send it.
4268 */
4269 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
4270 NET_INC_STATS(sock_net(sk), mib);
4271 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
4272}
4273
4274/* Called from setsockopt( ... TCP_REPAIR ) */
4275void tcp_send_window_probe(struct sock *sk)
4276{
4277 if (sk->sk_state == TCP_ESTABLISHED) {
4278 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
4279 tcp_mstamp_refresh(tcp_sk(sk));
4280 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
4281 }
4282}
4283
4284/* Initiate keepalive or window probe from timer. */
4285int tcp_write_wakeup(struct sock *sk, int mib)
4286{
4287 struct tcp_sock *tp = tcp_sk(sk);
4288 struct sk_buff *skb;
4289
4290 if (sk->sk_state == TCP_CLOSE)
4291 return -1;
4292
4293 skb = tcp_send_head(sk);
4294 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
4295 int err;
4296 unsigned int mss = tcp_current_mss(sk);
4297 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
4298
4299 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
4300 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
4301
4302 /* We are probing the opening of a window
4303 * but the window size is != 0
4304 * must have been a result SWS avoidance ( sender )
4305 */
4306 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
4307 skb->len > mss) {
4308 seg_size = min(seg_size, mss);
4309 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
4310 if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
4311 skb, seg_size, mss, GFP_ATOMIC))
4312 return -1;
4313 } else if (!tcp_skb_pcount(skb))
4314 tcp_set_skb_tso_segs(skb, mss);
4315
4316 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
4317 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
4318 if (!err)
4319 tcp_event_new_data_sent(sk, skb);
4320 return err;
4321 } else {
4322 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
4323 tcp_xmit_probe_skb(sk, 1, mib);
4324 return tcp_xmit_probe_skb(sk, 0, mib);
4325 }
4326}
4327
4328/* A window probe timeout has occurred. If window is not closed send
4329 * a partial packet else a zero probe.
4330 */
4331void tcp_send_probe0(struct sock *sk)
4332{
4333 struct inet_connection_sock *icsk = inet_csk(sk);
4334 struct tcp_sock *tp = tcp_sk(sk);
4335 struct net *net = sock_net(sk);
4336 unsigned long timeout;
4337 int err;
4338
4339 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
4340
4341 if (tp->packets_out || tcp_write_queue_empty(sk)) {
4342 /* Cancel probe timer, if it is not required. */
4343 icsk->icsk_probes_out = 0;
4344 icsk->icsk_backoff = 0;
4345 icsk->icsk_probes_tstamp = 0;
4346 return;
4347 }
4348
4349 icsk->icsk_probes_out++;
4350 if (err <= 0) {
4351 if (icsk->icsk_backoff < READ_ONCE(net->ipv4.sysctl_tcp_retries2))
4352 icsk->icsk_backoff++;
4353 timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
4354 } else {
4355 /* If packet was not sent due to local congestion,
4356 * Let senders fight for local resources conservatively.
4357 */
4358 timeout = TCP_RESOURCE_PROBE_INTERVAL;
4359 }
4360
4361 timeout = tcp_clamp_probe0_to_user_timeout(sk, timeout);
4362 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX);
4363}
4364
4365int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
4366{
4367 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
4368 struct flowi fl;
4369 int res;
4370
4371 /* Paired with WRITE_ONCE() in sock_setsockopt() */
4372 if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED)
4373 WRITE_ONCE(tcp_rsk(req)->txhash, net_tx_rndhash());
4374 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL,
4375 NULL);
4376 if (!res) {
4377 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
4378 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
4379 if (unlikely(tcp_passive_fastopen(sk))) {
4380 /* sk has const attribute because listeners are lockless.
4381 * However in this case, we are dealing with a passive fastopen
4382 * socket thus we can change total_retrans value.
4383 */
4384 tcp_sk_rw(sk)->total_retrans++;
4385 }
4386 trace_tcp_retransmit_synack(sk, req);
4387 }
4388 return res;
4389}
4390EXPORT_SYMBOL(tcp_rtx_synack);