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1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Authors: Ross Biro
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
19 */
20
21/*
22 * Changes: Pedro Roque : Retransmit queue handled by TCP.
23 * : Fragmentation on mtu decrease
24 * : Segment collapse on retransmit
25 * : AF independence
26 *
27 * Linus Torvalds : send_delayed_ack
28 * David S. Miller : Charge memory using the right skb
29 * during syn/ack processing.
30 * David S. Miller : Output engine completely rewritten.
31 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
32 * Cacophonix Gaul : draft-minshall-nagle-01
33 * J Hadi Salim : ECN support
34 *
35 */
36
37#define pr_fmt(fmt) "TCP: " fmt
38
39#include <net/tcp.h>
40
41#include <linux/compiler.h>
42#include <linux/gfp.h>
43#include <linux/module.h>
44
45/* People can turn this off for buggy TCP's found in printers etc. */
46int sysctl_tcp_retrans_collapse __read_mostly = 1;
47
48/* People can turn this on to work with those rare, broken TCPs that
49 * interpret the window field as a signed quantity.
50 */
51int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
52
53/* Default TSQ limit of two TSO segments */
54int sysctl_tcp_limit_output_bytes __read_mostly = 131072;
55
56/* This limits the percentage of the congestion window which we
57 * will allow a single TSO frame to consume. Building TSO frames
58 * which are too large can cause TCP streams to be bursty.
59 */
60int sysctl_tcp_tso_win_divisor __read_mostly = 3;
61
62int sysctl_tcp_mtu_probing __read_mostly = 0;
63int sysctl_tcp_base_mss __read_mostly = TCP_BASE_MSS;
64
65/* By default, RFC2861 behavior. */
66int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
67
68unsigned int sysctl_tcp_notsent_lowat __read_mostly = UINT_MAX;
69EXPORT_SYMBOL(sysctl_tcp_notsent_lowat);
70
71static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
72 int push_one, gfp_t gfp);
73
74/* Account for new data that has been sent to the network. */
75static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
76{
77 struct inet_connection_sock *icsk = inet_csk(sk);
78 struct tcp_sock *tp = tcp_sk(sk);
79 unsigned int prior_packets = tp->packets_out;
80
81 tcp_advance_send_head(sk, skb);
82 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
83
84 tp->packets_out += tcp_skb_pcount(skb);
85 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
86 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
87 tcp_rearm_rto(sk);
88 }
89
90 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
91 tcp_skb_pcount(skb));
92}
93
94/* SND.NXT, if window was not shrunk.
95 * If window has been shrunk, what should we make? It is not clear at all.
96 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
97 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
98 * invalid. OK, let's make this for now:
99 */
100static inline __u32 tcp_acceptable_seq(const struct sock *sk)
101{
102 const struct tcp_sock *tp = tcp_sk(sk);
103
104 if (!before(tcp_wnd_end(tp), tp->snd_nxt))
105 return tp->snd_nxt;
106 else
107 return tcp_wnd_end(tp);
108}
109
110/* Calculate mss to advertise in SYN segment.
111 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
112 *
113 * 1. It is independent of path mtu.
114 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
115 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
116 * attached devices, because some buggy hosts are confused by
117 * large MSS.
118 * 4. We do not make 3, we advertise MSS, calculated from first
119 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
120 * This may be overridden via information stored in routing table.
121 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
122 * probably even Jumbo".
123 */
124static __u16 tcp_advertise_mss(struct sock *sk)
125{
126 struct tcp_sock *tp = tcp_sk(sk);
127 const struct dst_entry *dst = __sk_dst_get(sk);
128 int mss = tp->advmss;
129
130 if (dst) {
131 unsigned int metric = dst_metric_advmss(dst);
132
133 if (metric < mss) {
134 mss = metric;
135 tp->advmss = mss;
136 }
137 }
138
139 return (__u16)mss;
140}
141
142/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
143 * This is the first part of cwnd validation mechanism. */
144static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst)
145{
146 struct tcp_sock *tp = tcp_sk(sk);
147 s32 delta = tcp_time_stamp - tp->lsndtime;
148 u32 restart_cwnd = tcp_init_cwnd(tp, dst);
149 u32 cwnd = tp->snd_cwnd;
150
151 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
152
153 tp->snd_ssthresh = tcp_current_ssthresh(sk);
154 restart_cwnd = min(restart_cwnd, cwnd);
155
156 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
157 cwnd >>= 1;
158 tp->snd_cwnd = max(cwnd, restart_cwnd);
159 tp->snd_cwnd_stamp = tcp_time_stamp;
160 tp->snd_cwnd_used = 0;
161}
162
163/* Congestion state accounting after a packet has been sent. */
164static void tcp_event_data_sent(struct tcp_sock *tp,
165 struct sock *sk)
166{
167 struct inet_connection_sock *icsk = inet_csk(sk);
168 const u32 now = tcp_time_stamp;
169 const struct dst_entry *dst = __sk_dst_get(sk);
170
171 if (sysctl_tcp_slow_start_after_idle &&
172 (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
173 tcp_cwnd_restart(sk, __sk_dst_get(sk));
174
175 tp->lsndtime = now;
176
177 /* If it is a reply for ato after last received
178 * packet, enter pingpong mode.
179 */
180 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato &&
181 (!dst || !dst_metric(dst, RTAX_QUICKACK)))
182 icsk->icsk_ack.pingpong = 1;
183}
184
185/* Account for an ACK we sent. */
186static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
187{
188 tcp_dec_quickack_mode(sk, pkts);
189 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
190}
191
192
193u32 tcp_default_init_rwnd(u32 mss)
194{
195 /* Initial receive window should be twice of TCP_INIT_CWND to
196 * enable proper sending of new unsent data during fast recovery
197 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
198 * limit when mss is larger than 1460.
199 */
200 u32 init_rwnd = TCP_INIT_CWND * 2;
201
202 if (mss > 1460)
203 init_rwnd = max((1460 * init_rwnd) / mss, 2U);
204 return init_rwnd;
205}
206
207/* Determine a window scaling and initial window to offer.
208 * Based on the assumption that the given amount of space
209 * will be offered. Store the results in the tp structure.
210 * NOTE: for smooth operation initial space offering should
211 * be a multiple of mss if possible. We assume here that mss >= 1.
212 * This MUST be enforced by all callers.
213 */
214void tcp_select_initial_window(int __space, __u32 mss,
215 __u32 *rcv_wnd, __u32 *window_clamp,
216 int wscale_ok, __u8 *rcv_wscale,
217 __u32 init_rcv_wnd)
218{
219 unsigned int space = (__space < 0 ? 0 : __space);
220
221 /* If no clamp set the clamp to the max possible scaled window */
222 if (*window_clamp == 0)
223 (*window_clamp) = (65535 << 14);
224 space = min(*window_clamp, space);
225
226 /* Quantize space offering to a multiple of mss if possible. */
227 if (space > mss)
228 space = (space / mss) * mss;
229
230 /* NOTE: offering an initial window larger than 32767
231 * will break some buggy TCP stacks. If the admin tells us
232 * it is likely we could be speaking with such a buggy stack
233 * we will truncate our initial window offering to 32K-1
234 * unless the remote has sent us a window scaling option,
235 * which we interpret as a sign the remote TCP is not
236 * misinterpreting the window field as a signed quantity.
237 */
238 if (sysctl_tcp_workaround_signed_windows)
239 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
240 else
241 (*rcv_wnd) = space;
242
243 (*rcv_wscale) = 0;
244 if (wscale_ok) {
245 /* Set window scaling on max possible window
246 * See RFC1323 for an explanation of the limit to 14
247 */
248 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
249 space = min_t(u32, space, *window_clamp);
250 while (space > 65535 && (*rcv_wscale) < 14) {
251 space >>= 1;
252 (*rcv_wscale)++;
253 }
254 }
255
256 if (mss > (1 << *rcv_wscale)) {
257 if (!init_rcv_wnd) /* Use default unless specified otherwise */
258 init_rcv_wnd = tcp_default_init_rwnd(mss);
259 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
260 }
261
262 /* Set the clamp no higher than max representable value */
263 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
264}
265EXPORT_SYMBOL(tcp_select_initial_window);
266
267/* Chose a new window to advertise, update state in tcp_sock for the
268 * socket, and return result with RFC1323 scaling applied. The return
269 * value can be stuffed directly into th->window for an outgoing
270 * frame.
271 */
272static u16 tcp_select_window(struct sock *sk)
273{
274 struct tcp_sock *tp = tcp_sk(sk);
275 u32 old_win = tp->rcv_wnd;
276 u32 cur_win = tcp_receive_window(tp);
277 u32 new_win = __tcp_select_window(sk);
278
279 /* Never shrink the offered window */
280 if (new_win < cur_win) {
281 /* Danger Will Robinson!
282 * Don't update rcv_wup/rcv_wnd here or else
283 * we will not be able to advertise a zero
284 * window in time. --DaveM
285 *
286 * Relax Will Robinson.
287 */
288 if (new_win == 0)
289 NET_INC_STATS(sock_net(sk),
290 LINUX_MIB_TCPWANTZEROWINDOWADV);
291 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
292 }
293 tp->rcv_wnd = new_win;
294 tp->rcv_wup = tp->rcv_nxt;
295
296 /* Make sure we do not exceed the maximum possible
297 * scaled window.
298 */
299 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
300 new_win = min(new_win, MAX_TCP_WINDOW);
301 else
302 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
303
304 /* RFC1323 scaling applied */
305 new_win >>= tp->rx_opt.rcv_wscale;
306
307 /* If we advertise zero window, disable fast path. */
308 if (new_win == 0) {
309 tp->pred_flags = 0;
310 if (old_win)
311 NET_INC_STATS(sock_net(sk),
312 LINUX_MIB_TCPTOZEROWINDOWADV);
313 } else if (old_win == 0) {
314 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
315 }
316
317 return new_win;
318}
319
320/* Packet ECN state for a SYN-ACK */
321static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb)
322{
323 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
324 if (!(tp->ecn_flags & TCP_ECN_OK))
325 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
326}
327
328/* Packet ECN state for a SYN. */
329static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
330{
331 struct tcp_sock *tp = tcp_sk(sk);
332
333 tp->ecn_flags = 0;
334 if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1) {
335 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
336 tp->ecn_flags = TCP_ECN_OK;
337 }
338}
339
340static __inline__ void
341TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th)
342{
343 if (inet_rsk(req)->ecn_ok)
344 th->ece = 1;
345}
346
347/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
348 * be sent.
349 */
350static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
351 int tcp_header_len)
352{
353 struct tcp_sock *tp = tcp_sk(sk);
354
355 if (tp->ecn_flags & TCP_ECN_OK) {
356 /* Not-retransmitted data segment: set ECT and inject CWR. */
357 if (skb->len != tcp_header_len &&
358 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
359 INET_ECN_xmit(sk);
360 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
361 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
362 tcp_hdr(skb)->cwr = 1;
363 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
364 }
365 } else {
366 /* ACK or retransmitted segment: clear ECT|CE */
367 INET_ECN_dontxmit(sk);
368 }
369 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
370 tcp_hdr(skb)->ece = 1;
371 }
372}
373
374/* Constructs common control bits of non-data skb. If SYN/FIN is present,
375 * auto increment end seqno.
376 */
377static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
378{
379 struct skb_shared_info *shinfo = skb_shinfo(skb);
380
381 skb->ip_summed = CHECKSUM_PARTIAL;
382 skb->csum = 0;
383
384 TCP_SKB_CB(skb)->tcp_flags = flags;
385 TCP_SKB_CB(skb)->sacked = 0;
386
387 shinfo->gso_segs = 1;
388 shinfo->gso_size = 0;
389 shinfo->gso_type = 0;
390
391 TCP_SKB_CB(skb)->seq = seq;
392 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
393 seq++;
394 TCP_SKB_CB(skb)->end_seq = seq;
395}
396
397static inline bool tcp_urg_mode(const struct tcp_sock *tp)
398{
399 return tp->snd_una != tp->snd_up;
400}
401
402#define OPTION_SACK_ADVERTISE (1 << 0)
403#define OPTION_TS (1 << 1)
404#define OPTION_MD5 (1 << 2)
405#define OPTION_WSCALE (1 << 3)
406#define OPTION_FAST_OPEN_COOKIE (1 << 8)
407
408struct tcp_out_options {
409 u16 options; /* bit field of OPTION_* */
410 u16 mss; /* 0 to disable */
411 u8 ws; /* window scale, 0 to disable */
412 u8 num_sack_blocks; /* number of SACK blocks to include */
413 u8 hash_size; /* bytes in hash_location */
414 __u8 *hash_location; /* temporary pointer, overloaded */
415 __u32 tsval, tsecr; /* need to include OPTION_TS */
416 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
417};
418
419/* Write previously computed TCP options to the packet.
420 *
421 * Beware: Something in the Internet is very sensitive to the ordering of
422 * TCP options, we learned this through the hard way, so be careful here.
423 * Luckily we can at least blame others for their non-compliance but from
424 * inter-operability perspective it seems that we're somewhat stuck with
425 * the ordering which we have been using if we want to keep working with
426 * those broken things (not that it currently hurts anybody as there isn't
427 * particular reason why the ordering would need to be changed).
428 *
429 * At least SACK_PERM as the first option is known to lead to a disaster
430 * (but it may well be that other scenarios fail similarly).
431 */
432static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
433 struct tcp_out_options *opts)
434{
435 u16 options = opts->options; /* mungable copy */
436
437 if (unlikely(OPTION_MD5 & options)) {
438 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
439 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
440 /* overload cookie hash location */
441 opts->hash_location = (__u8 *)ptr;
442 ptr += 4;
443 }
444
445 if (unlikely(opts->mss)) {
446 *ptr++ = htonl((TCPOPT_MSS << 24) |
447 (TCPOLEN_MSS << 16) |
448 opts->mss);
449 }
450
451 if (likely(OPTION_TS & options)) {
452 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
453 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
454 (TCPOLEN_SACK_PERM << 16) |
455 (TCPOPT_TIMESTAMP << 8) |
456 TCPOLEN_TIMESTAMP);
457 options &= ~OPTION_SACK_ADVERTISE;
458 } else {
459 *ptr++ = htonl((TCPOPT_NOP << 24) |
460 (TCPOPT_NOP << 16) |
461 (TCPOPT_TIMESTAMP << 8) |
462 TCPOLEN_TIMESTAMP);
463 }
464 *ptr++ = htonl(opts->tsval);
465 *ptr++ = htonl(opts->tsecr);
466 }
467
468 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
469 *ptr++ = htonl((TCPOPT_NOP << 24) |
470 (TCPOPT_NOP << 16) |
471 (TCPOPT_SACK_PERM << 8) |
472 TCPOLEN_SACK_PERM);
473 }
474
475 if (unlikely(OPTION_WSCALE & options)) {
476 *ptr++ = htonl((TCPOPT_NOP << 24) |
477 (TCPOPT_WINDOW << 16) |
478 (TCPOLEN_WINDOW << 8) |
479 opts->ws);
480 }
481
482 if (unlikely(opts->num_sack_blocks)) {
483 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
484 tp->duplicate_sack : tp->selective_acks;
485 int this_sack;
486
487 *ptr++ = htonl((TCPOPT_NOP << 24) |
488 (TCPOPT_NOP << 16) |
489 (TCPOPT_SACK << 8) |
490 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
491 TCPOLEN_SACK_PERBLOCK)));
492
493 for (this_sack = 0; this_sack < opts->num_sack_blocks;
494 ++this_sack) {
495 *ptr++ = htonl(sp[this_sack].start_seq);
496 *ptr++ = htonl(sp[this_sack].end_seq);
497 }
498
499 tp->rx_opt.dsack = 0;
500 }
501
502 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
503 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
504
505 *ptr++ = htonl((TCPOPT_EXP << 24) |
506 ((TCPOLEN_EXP_FASTOPEN_BASE + foc->len) << 16) |
507 TCPOPT_FASTOPEN_MAGIC);
508
509 memcpy(ptr, foc->val, foc->len);
510 if ((foc->len & 3) == 2) {
511 u8 *align = ((u8 *)ptr) + foc->len;
512 align[0] = align[1] = TCPOPT_NOP;
513 }
514 ptr += (foc->len + 3) >> 2;
515 }
516}
517
518/* Compute TCP options for SYN packets. This is not the final
519 * network wire format yet.
520 */
521static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
522 struct tcp_out_options *opts,
523 struct tcp_md5sig_key **md5)
524{
525 struct tcp_sock *tp = tcp_sk(sk);
526 unsigned int remaining = MAX_TCP_OPTION_SPACE;
527 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
528
529#ifdef CONFIG_TCP_MD5SIG
530 *md5 = tp->af_specific->md5_lookup(sk, sk);
531 if (*md5) {
532 opts->options |= OPTION_MD5;
533 remaining -= TCPOLEN_MD5SIG_ALIGNED;
534 }
535#else
536 *md5 = NULL;
537#endif
538
539 /* We always get an MSS option. The option bytes which will be seen in
540 * normal data packets should timestamps be used, must be in the MSS
541 * advertised. But we subtract them from tp->mss_cache so that
542 * calculations in tcp_sendmsg are simpler etc. So account for this
543 * fact here if necessary. If we don't do this correctly, as a
544 * receiver we won't recognize data packets as being full sized when we
545 * should, and thus we won't abide by the delayed ACK rules correctly.
546 * SACKs don't matter, we never delay an ACK when we have any of those
547 * going out. */
548 opts->mss = tcp_advertise_mss(sk);
549 remaining -= TCPOLEN_MSS_ALIGNED;
550
551 if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
552 opts->options |= OPTION_TS;
553 opts->tsval = TCP_SKB_CB(skb)->when + tp->tsoffset;
554 opts->tsecr = tp->rx_opt.ts_recent;
555 remaining -= TCPOLEN_TSTAMP_ALIGNED;
556 }
557 if (likely(sysctl_tcp_window_scaling)) {
558 opts->ws = tp->rx_opt.rcv_wscale;
559 opts->options |= OPTION_WSCALE;
560 remaining -= TCPOLEN_WSCALE_ALIGNED;
561 }
562 if (likely(sysctl_tcp_sack)) {
563 opts->options |= OPTION_SACK_ADVERTISE;
564 if (unlikely(!(OPTION_TS & opts->options)))
565 remaining -= TCPOLEN_SACKPERM_ALIGNED;
566 }
567
568 if (fastopen && fastopen->cookie.len >= 0) {
569 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + fastopen->cookie.len;
570 need = (need + 3) & ~3U; /* Align to 32 bits */
571 if (remaining >= need) {
572 opts->options |= OPTION_FAST_OPEN_COOKIE;
573 opts->fastopen_cookie = &fastopen->cookie;
574 remaining -= need;
575 tp->syn_fastopen = 1;
576 }
577 }
578
579 return MAX_TCP_OPTION_SPACE - remaining;
580}
581
582/* Set up TCP options for SYN-ACKs. */
583static unsigned int tcp_synack_options(struct sock *sk,
584 struct request_sock *req,
585 unsigned int mss, struct sk_buff *skb,
586 struct tcp_out_options *opts,
587 struct tcp_md5sig_key **md5,
588 struct tcp_fastopen_cookie *foc)
589{
590 struct inet_request_sock *ireq = inet_rsk(req);
591 unsigned int remaining = MAX_TCP_OPTION_SPACE;
592
593#ifdef CONFIG_TCP_MD5SIG
594 *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
595 if (*md5) {
596 opts->options |= OPTION_MD5;
597 remaining -= TCPOLEN_MD5SIG_ALIGNED;
598
599 /* We can't fit any SACK blocks in a packet with MD5 + TS
600 * options. There was discussion about disabling SACK
601 * rather than TS in order to fit in better with old,
602 * buggy kernels, but that was deemed to be unnecessary.
603 */
604 ireq->tstamp_ok &= !ireq->sack_ok;
605 }
606#else
607 *md5 = NULL;
608#endif
609
610 /* We always send an MSS option. */
611 opts->mss = mss;
612 remaining -= TCPOLEN_MSS_ALIGNED;
613
614 if (likely(ireq->wscale_ok)) {
615 opts->ws = ireq->rcv_wscale;
616 opts->options |= OPTION_WSCALE;
617 remaining -= TCPOLEN_WSCALE_ALIGNED;
618 }
619 if (likely(ireq->tstamp_ok)) {
620 opts->options |= OPTION_TS;
621 opts->tsval = TCP_SKB_CB(skb)->when;
622 opts->tsecr = req->ts_recent;
623 remaining -= TCPOLEN_TSTAMP_ALIGNED;
624 }
625 if (likely(ireq->sack_ok)) {
626 opts->options |= OPTION_SACK_ADVERTISE;
627 if (unlikely(!ireq->tstamp_ok))
628 remaining -= TCPOLEN_SACKPERM_ALIGNED;
629 }
630 if (foc != NULL) {
631 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
632 need = (need + 3) & ~3U; /* Align to 32 bits */
633 if (remaining >= need) {
634 opts->options |= OPTION_FAST_OPEN_COOKIE;
635 opts->fastopen_cookie = foc;
636 remaining -= need;
637 }
638 }
639
640 return MAX_TCP_OPTION_SPACE - remaining;
641}
642
643/* Compute TCP options for ESTABLISHED sockets. This is not the
644 * final wire format yet.
645 */
646static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
647 struct tcp_out_options *opts,
648 struct tcp_md5sig_key **md5)
649{
650 struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
651 struct tcp_sock *tp = tcp_sk(sk);
652 unsigned int size = 0;
653 unsigned int eff_sacks;
654
655 opts->options = 0;
656
657#ifdef CONFIG_TCP_MD5SIG
658 *md5 = tp->af_specific->md5_lookup(sk, sk);
659 if (unlikely(*md5)) {
660 opts->options |= OPTION_MD5;
661 size += TCPOLEN_MD5SIG_ALIGNED;
662 }
663#else
664 *md5 = NULL;
665#endif
666
667 if (likely(tp->rx_opt.tstamp_ok)) {
668 opts->options |= OPTION_TS;
669 opts->tsval = tcb ? tcb->when + tp->tsoffset : 0;
670 opts->tsecr = tp->rx_opt.ts_recent;
671 size += TCPOLEN_TSTAMP_ALIGNED;
672 }
673
674 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
675 if (unlikely(eff_sacks)) {
676 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
677 opts->num_sack_blocks =
678 min_t(unsigned int, eff_sacks,
679 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
680 TCPOLEN_SACK_PERBLOCK);
681 size += TCPOLEN_SACK_BASE_ALIGNED +
682 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
683 }
684
685 return size;
686}
687
688
689/* TCP SMALL QUEUES (TSQ)
690 *
691 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
692 * to reduce RTT and bufferbloat.
693 * We do this using a special skb destructor (tcp_wfree).
694 *
695 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
696 * needs to be reallocated in a driver.
697 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
698 *
699 * Since transmit from skb destructor is forbidden, we use a tasklet
700 * to process all sockets that eventually need to send more skbs.
701 * We use one tasklet per cpu, with its own queue of sockets.
702 */
703struct tsq_tasklet {
704 struct tasklet_struct tasklet;
705 struct list_head head; /* queue of tcp sockets */
706};
707static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
708
709static void tcp_tsq_handler(struct sock *sk)
710{
711 if ((1 << sk->sk_state) &
712 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
713 TCPF_CLOSE_WAIT | TCPF_LAST_ACK))
714 tcp_write_xmit(sk, tcp_current_mss(sk), tcp_sk(sk)->nonagle,
715 0, GFP_ATOMIC);
716}
717/*
718 * One tasklet per cpu tries to send more skbs.
719 * We run in tasklet context but need to disable irqs when
720 * transferring tsq->head because tcp_wfree() might
721 * interrupt us (non NAPI drivers)
722 */
723static void tcp_tasklet_func(unsigned long data)
724{
725 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
726 LIST_HEAD(list);
727 unsigned long flags;
728 struct list_head *q, *n;
729 struct tcp_sock *tp;
730 struct sock *sk;
731
732 local_irq_save(flags);
733 list_splice_init(&tsq->head, &list);
734 local_irq_restore(flags);
735
736 list_for_each_safe(q, n, &list) {
737 tp = list_entry(q, struct tcp_sock, tsq_node);
738 list_del(&tp->tsq_node);
739
740 sk = (struct sock *)tp;
741 bh_lock_sock(sk);
742
743 if (!sock_owned_by_user(sk)) {
744 tcp_tsq_handler(sk);
745 } else {
746 /* defer the work to tcp_release_cb() */
747 set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
748 }
749 bh_unlock_sock(sk);
750
751 clear_bit(TSQ_QUEUED, &tp->tsq_flags);
752 sk_free(sk);
753 }
754}
755
756#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
757 (1UL << TCP_WRITE_TIMER_DEFERRED) | \
758 (1UL << TCP_DELACK_TIMER_DEFERRED) | \
759 (1UL << TCP_MTU_REDUCED_DEFERRED))
760/**
761 * tcp_release_cb - tcp release_sock() callback
762 * @sk: socket
763 *
764 * called from release_sock() to perform protocol dependent
765 * actions before socket release.
766 */
767void tcp_release_cb(struct sock *sk)
768{
769 struct tcp_sock *tp = tcp_sk(sk);
770 unsigned long flags, nflags;
771
772 /* perform an atomic operation only if at least one flag is set */
773 do {
774 flags = tp->tsq_flags;
775 if (!(flags & TCP_DEFERRED_ALL))
776 return;
777 nflags = flags & ~TCP_DEFERRED_ALL;
778 } while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);
779
780 if (flags & (1UL << TCP_TSQ_DEFERRED))
781 tcp_tsq_handler(sk);
782
783 /* Here begins the tricky part :
784 * We are called from release_sock() with :
785 * 1) BH disabled
786 * 2) sk_lock.slock spinlock held
787 * 3) socket owned by us (sk->sk_lock.owned == 1)
788 *
789 * But following code is meant to be called from BH handlers,
790 * so we should keep BH disabled, but early release socket ownership
791 */
792 sock_release_ownership(sk);
793
794 if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
795 tcp_write_timer_handler(sk);
796 __sock_put(sk);
797 }
798 if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) {
799 tcp_delack_timer_handler(sk);
800 __sock_put(sk);
801 }
802 if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) {
803 sk->sk_prot->mtu_reduced(sk);
804 __sock_put(sk);
805 }
806}
807EXPORT_SYMBOL(tcp_release_cb);
808
809void __init tcp_tasklet_init(void)
810{
811 int i;
812
813 for_each_possible_cpu(i) {
814 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
815
816 INIT_LIST_HEAD(&tsq->head);
817 tasklet_init(&tsq->tasklet,
818 tcp_tasklet_func,
819 (unsigned long)tsq);
820 }
821}
822
823/*
824 * Write buffer destructor automatically called from kfree_skb.
825 * We can't xmit new skbs from this context, as we might already
826 * hold qdisc lock.
827 */
828void tcp_wfree(struct sk_buff *skb)
829{
830 struct sock *sk = skb->sk;
831 struct tcp_sock *tp = tcp_sk(sk);
832
833 if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) &&
834 !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) {
835 unsigned long flags;
836 struct tsq_tasklet *tsq;
837
838 /* Keep a ref on socket.
839 * This last ref will be released in tcp_tasklet_func()
840 */
841 atomic_sub(skb->truesize - 1, &sk->sk_wmem_alloc);
842
843 /* queue this socket to tasklet queue */
844 local_irq_save(flags);
845 tsq = &__get_cpu_var(tsq_tasklet);
846 list_add(&tp->tsq_node, &tsq->head);
847 tasklet_schedule(&tsq->tasklet);
848 local_irq_restore(flags);
849 } else {
850 sock_wfree(skb);
851 }
852}
853
854/* This routine actually transmits TCP packets queued in by
855 * tcp_do_sendmsg(). This is used by both the initial
856 * transmission and possible later retransmissions.
857 * All SKB's seen here are completely headerless. It is our
858 * job to build the TCP header, and pass the packet down to
859 * IP so it can do the same plus pass the packet off to the
860 * device.
861 *
862 * We are working here with either a clone of the original
863 * SKB, or a fresh unique copy made by the retransmit engine.
864 */
865static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
866 gfp_t gfp_mask)
867{
868 const struct inet_connection_sock *icsk = inet_csk(sk);
869 struct inet_sock *inet;
870 struct tcp_sock *tp;
871 struct tcp_skb_cb *tcb;
872 struct tcp_out_options opts;
873 unsigned int tcp_options_size, tcp_header_size;
874 struct tcp_md5sig_key *md5;
875 struct tcphdr *th;
876 int err;
877
878 BUG_ON(!skb || !tcp_skb_pcount(skb));
879
880 if (clone_it) {
881 const struct sk_buff *fclone = skb + 1;
882
883 skb_mstamp_get(&skb->skb_mstamp);
884
885 if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
886 fclone->fclone == SKB_FCLONE_CLONE))
887 NET_INC_STATS(sock_net(sk),
888 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
889
890 if (unlikely(skb_cloned(skb)))
891 skb = pskb_copy(skb, gfp_mask);
892 else
893 skb = skb_clone(skb, gfp_mask);
894 if (unlikely(!skb))
895 return -ENOBUFS;
896 /* Our usage of tstamp should remain private */
897 skb->tstamp.tv64 = 0;
898 }
899
900 inet = inet_sk(sk);
901 tp = tcp_sk(sk);
902 tcb = TCP_SKB_CB(skb);
903 memset(&opts, 0, sizeof(opts));
904
905 if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
906 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
907 else
908 tcp_options_size = tcp_established_options(sk, skb, &opts,
909 &md5);
910 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
911
912 if (tcp_packets_in_flight(tp) == 0)
913 tcp_ca_event(sk, CA_EVENT_TX_START);
914
915 /* if no packet is in qdisc/device queue, then allow XPS to select
916 * another queue.
917 */
918 skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;
919
920 skb_push(skb, tcp_header_size);
921 skb_reset_transport_header(skb);
922
923 skb_orphan(skb);
924 skb->sk = sk;
925 skb->destructor = tcp_wfree;
926 atomic_add(skb->truesize, &sk->sk_wmem_alloc);
927
928 /* Build TCP header and checksum it. */
929 th = tcp_hdr(skb);
930 th->source = inet->inet_sport;
931 th->dest = inet->inet_dport;
932 th->seq = htonl(tcb->seq);
933 th->ack_seq = htonl(tp->rcv_nxt);
934 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
935 tcb->tcp_flags);
936
937 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
938 /* RFC1323: The window in SYN & SYN/ACK segments
939 * is never scaled.
940 */
941 th->window = htons(min(tp->rcv_wnd, 65535U));
942 } else {
943 th->window = htons(tcp_select_window(sk));
944 }
945 th->check = 0;
946 th->urg_ptr = 0;
947
948 /* The urg_mode check is necessary during a below snd_una win probe */
949 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
950 if (before(tp->snd_up, tcb->seq + 0x10000)) {
951 th->urg_ptr = htons(tp->snd_up - tcb->seq);
952 th->urg = 1;
953 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
954 th->urg_ptr = htons(0xFFFF);
955 th->urg = 1;
956 }
957 }
958
959 tcp_options_write((__be32 *)(th + 1), tp, &opts);
960 if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
961 TCP_ECN_send(sk, skb, tcp_header_size);
962
963#ifdef CONFIG_TCP_MD5SIG
964 /* Calculate the MD5 hash, as we have all we need now */
965 if (md5) {
966 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
967 tp->af_specific->calc_md5_hash(opts.hash_location,
968 md5, sk, NULL, skb);
969 }
970#endif
971
972 icsk->icsk_af_ops->send_check(sk, skb);
973
974 if (likely(tcb->tcp_flags & TCPHDR_ACK))
975 tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
976
977 if (skb->len != tcp_header_size)
978 tcp_event_data_sent(tp, sk);
979
980 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
981 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
982 tcp_skb_pcount(skb));
983
984 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
985 if (likely(err <= 0))
986 return err;
987
988 tcp_enter_cwr(sk, 1);
989
990 return net_xmit_eval(err);
991}
992
993/* This routine just queues the buffer for sending.
994 *
995 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
996 * otherwise socket can stall.
997 */
998static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
999{
1000 struct tcp_sock *tp = tcp_sk(sk);
1001
1002 /* Advance write_seq and place onto the write_queue. */
1003 tp->write_seq = TCP_SKB_CB(skb)->end_seq;
1004 skb_header_release(skb);
1005 tcp_add_write_queue_tail(sk, skb);
1006 sk->sk_wmem_queued += skb->truesize;
1007 sk_mem_charge(sk, skb->truesize);
1008}
1009
1010/* Initialize TSO segments for a packet. */
1011static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
1012 unsigned int mss_now)
1013{
1014 struct skb_shared_info *shinfo = skb_shinfo(skb);
1015
1016 /* Make sure we own this skb before messing gso_size/gso_segs */
1017 WARN_ON_ONCE(skb_cloned(skb));
1018
1019 if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1020 /* Avoid the costly divide in the normal
1021 * non-TSO case.
1022 */
1023 shinfo->gso_segs = 1;
1024 shinfo->gso_size = 0;
1025 shinfo->gso_type = 0;
1026 } else {
1027 shinfo->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
1028 shinfo->gso_size = mss_now;
1029 shinfo->gso_type = sk->sk_gso_type;
1030 }
1031}
1032
1033/* When a modification to fackets out becomes necessary, we need to check
1034 * skb is counted to fackets_out or not.
1035 */
1036static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
1037 int decr)
1038{
1039 struct tcp_sock *tp = tcp_sk(sk);
1040
1041 if (!tp->sacked_out || tcp_is_reno(tp))
1042 return;
1043
1044 if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
1045 tp->fackets_out -= decr;
1046}
1047
1048/* Pcount in the middle of the write queue got changed, we need to do various
1049 * tweaks to fix counters
1050 */
1051static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1052{
1053 struct tcp_sock *tp = tcp_sk(sk);
1054
1055 tp->packets_out -= decr;
1056
1057 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1058 tp->sacked_out -= decr;
1059 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1060 tp->retrans_out -= decr;
1061 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1062 tp->lost_out -= decr;
1063
1064 /* Reno case is special. Sigh... */
1065 if (tcp_is_reno(tp) && decr > 0)
1066 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1067
1068 tcp_adjust_fackets_out(sk, skb, decr);
1069
1070 if (tp->lost_skb_hint &&
1071 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1072 (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1073 tp->lost_cnt_hint -= decr;
1074
1075 tcp_verify_left_out(tp);
1076}
1077
1078/* Function to create two new TCP segments. Shrinks the given segment
1079 * to the specified size and appends a new segment with the rest of the
1080 * packet to the list. This won't be called frequently, I hope.
1081 * Remember, these are still headerless SKBs at this point.
1082 */
1083int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1084 unsigned int mss_now)
1085{
1086 struct tcp_sock *tp = tcp_sk(sk);
1087 struct sk_buff *buff;
1088 int nsize, old_factor;
1089 int nlen;
1090 u8 flags;
1091
1092 if (WARN_ON(len > skb->len))
1093 return -EINVAL;
1094
1095 nsize = skb_headlen(skb) - len;
1096 if (nsize < 0)
1097 nsize = 0;
1098
1099 if (skb_unclone(skb, GFP_ATOMIC))
1100 return -ENOMEM;
1101
1102 /* Get a new skb... force flag on. */
1103 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
1104 if (buff == NULL)
1105 return -ENOMEM; /* We'll just try again later. */
1106
1107 sk->sk_wmem_queued += buff->truesize;
1108 sk_mem_charge(sk, buff->truesize);
1109 nlen = skb->len - len - nsize;
1110 buff->truesize += nlen;
1111 skb->truesize -= nlen;
1112
1113 /* Correct the sequence numbers. */
1114 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1115 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1116 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1117
1118 /* PSH and FIN should only be set in the second packet. */
1119 flags = TCP_SKB_CB(skb)->tcp_flags;
1120 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1121 TCP_SKB_CB(buff)->tcp_flags = flags;
1122 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1123
1124 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
1125 /* Copy and checksum data tail into the new buffer. */
1126 buff->csum = csum_partial_copy_nocheck(skb->data + len,
1127 skb_put(buff, nsize),
1128 nsize, 0);
1129
1130 skb_trim(skb, len);
1131
1132 skb->csum = csum_block_sub(skb->csum, buff->csum, len);
1133 } else {
1134 skb->ip_summed = CHECKSUM_PARTIAL;
1135 skb_split(skb, buff, len);
1136 }
1137
1138 buff->ip_summed = skb->ip_summed;
1139
1140 /* Looks stupid, but our code really uses when of
1141 * skbs, which it never sent before. --ANK
1142 */
1143 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
1144 buff->tstamp = skb->tstamp;
1145
1146 old_factor = tcp_skb_pcount(skb);
1147
1148 /* Fix up tso_factor for both original and new SKB. */
1149 tcp_set_skb_tso_segs(sk, skb, mss_now);
1150 tcp_set_skb_tso_segs(sk, buff, mss_now);
1151
1152 /* If this packet has been sent out already, we must
1153 * adjust the various packet counters.
1154 */
1155 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1156 int diff = old_factor - tcp_skb_pcount(skb) -
1157 tcp_skb_pcount(buff);
1158
1159 if (diff)
1160 tcp_adjust_pcount(sk, skb, diff);
1161 }
1162
1163 /* Link BUFF into the send queue. */
1164 skb_header_release(buff);
1165 tcp_insert_write_queue_after(skb, buff, sk);
1166
1167 return 0;
1168}
1169
1170/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1171 * eventually). The difference is that pulled data not copied, but
1172 * immediately discarded.
1173 */
1174static void __pskb_trim_head(struct sk_buff *skb, int len)
1175{
1176 struct skb_shared_info *shinfo;
1177 int i, k, eat;
1178
1179 eat = min_t(int, len, skb_headlen(skb));
1180 if (eat) {
1181 __skb_pull(skb, eat);
1182 len -= eat;
1183 if (!len)
1184 return;
1185 }
1186 eat = len;
1187 k = 0;
1188 shinfo = skb_shinfo(skb);
1189 for (i = 0; i < shinfo->nr_frags; i++) {
1190 int size = skb_frag_size(&shinfo->frags[i]);
1191
1192 if (size <= eat) {
1193 skb_frag_unref(skb, i);
1194 eat -= size;
1195 } else {
1196 shinfo->frags[k] = shinfo->frags[i];
1197 if (eat) {
1198 shinfo->frags[k].page_offset += eat;
1199 skb_frag_size_sub(&shinfo->frags[k], eat);
1200 eat = 0;
1201 }
1202 k++;
1203 }
1204 }
1205 shinfo->nr_frags = k;
1206
1207 skb_reset_tail_pointer(skb);
1208 skb->data_len -= len;
1209 skb->len = skb->data_len;
1210}
1211
1212/* Remove acked data from a packet in the transmit queue. */
1213int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1214{
1215 if (skb_unclone(skb, GFP_ATOMIC))
1216 return -ENOMEM;
1217
1218 __pskb_trim_head(skb, len);
1219
1220 TCP_SKB_CB(skb)->seq += len;
1221 skb->ip_summed = CHECKSUM_PARTIAL;
1222
1223 skb->truesize -= len;
1224 sk->sk_wmem_queued -= len;
1225 sk_mem_uncharge(sk, len);
1226 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1227
1228 /* Any change of skb->len requires recalculation of tso factor. */
1229 if (tcp_skb_pcount(skb) > 1)
1230 tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb));
1231
1232 return 0;
1233}
1234
1235/* Calculate MSS not accounting any TCP options. */
1236static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1237{
1238 const struct tcp_sock *tp = tcp_sk(sk);
1239 const struct inet_connection_sock *icsk = inet_csk(sk);
1240 int mss_now;
1241
1242 /* Calculate base mss without TCP options:
1243 It is MMS_S - sizeof(tcphdr) of rfc1122
1244 */
1245 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1246
1247 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1248 if (icsk->icsk_af_ops->net_frag_header_len) {
1249 const struct dst_entry *dst = __sk_dst_get(sk);
1250
1251 if (dst && dst_allfrag(dst))
1252 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1253 }
1254
1255 /* Clamp it (mss_clamp does not include tcp options) */
1256 if (mss_now > tp->rx_opt.mss_clamp)
1257 mss_now = tp->rx_opt.mss_clamp;
1258
1259 /* Now subtract optional transport overhead */
1260 mss_now -= icsk->icsk_ext_hdr_len;
1261
1262 /* Then reserve room for full set of TCP options and 8 bytes of data */
1263 if (mss_now < 48)
1264 mss_now = 48;
1265 return mss_now;
1266}
1267
1268/* Calculate MSS. Not accounting for SACKs here. */
1269int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1270{
1271 /* Subtract TCP options size, not including SACKs */
1272 return __tcp_mtu_to_mss(sk, pmtu) -
1273 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1274}
1275
1276/* Inverse of above */
1277int tcp_mss_to_mtu(struct sock *sk, int mss)
1278{
1279 const struct tcp_sock *tp = tcp_sk(sk);
1280 const struct inet_connection_sock *icsk = inet_csk(sk);
1281 int mtu;
1282
1283 mtu = mss +
1284 tp->tcp_header_len +
1285 icsk->icsk_ext_hdr_len +
1286 icsk->icsk_af_ops->net_header_len;
1287
1288 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1289 if (icsk->icsk_af_ops->net_frag_header_len) {
1290 const struct dst_entry *dst = __sk_dst_get(sk);
1291
1292 if (dst && dst_allfrag(dst))
1293 mtu += icsk->icsk_af_ops->net_frag_header_len;
1294 }
1295 return mtu;
1296}
1297
1298/* MTU probing init per socket */
1299void tcp_mtup_init(struct sock *sk)
1300{
1301 struct tcp_sock *tp = tcp_sk(sk);
1302 struct inet_connection_sock *icsk = inet_csk(sk);
1303
1304 icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1;
1305 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1306 icsk->icsk_af_ops->net_header_len;
1307 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
1308 icsk->icsk_mtup.probe_size = 0;
1309}
1310EXPORT_SYMBOL(tcp_mtup_init);
1311
1312/* This function synchronize snd mss to current pmtu/exthdr set.
1313
1314 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1315 for TCP options, but includes only bare TCP header.
1316
1317 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1318 It is minimum of user_mss and mss received with SYN.
1319 It also does not include TCP options.
1320
1321 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1322
1323 tp->mss_cache is current effective sending mss, including
1324 all tcp options except for SACKs. It is evaluated,
1325 taking into account current pmtu, but never exceeds
1326 tp->rx_opt.mss_clamp.
1327
1328 NOTE1. rfc1122 clearly states that advertised MSS
1329 DOES NOT include either tcp or ip options.
1330
1331 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1332 are READ ONLY outside this function. --ANK (980731)
1333 */
1334unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1335{
1336 struct tcp_sock *tp = tcp_sk(sk);
1337 struct inet_connection_sock *icsk = inet_csk(sk);
1338 int mss_now;
1339
1340 if (icsk->icsk_mtup.search_high > pmtu)
1341 icsk->icsk_mtup.search_high = pmtu;
1342
1343 mss_now = tcp_mtu_to_mss(sk, pmtu);
1344 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1345
1346 /* And store cached results */
1347 icsk->icsk_pmtu_cookie = pmtu;
1348 if (icsk->icsk_mtup.enabled)
1349 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1350 tp->mss_cache = mss_now;
1351
1352 return mss_now;
1353}
1354EXPORT_SYMBOL(tcp_sync_mss);
1355
1356/* Compute the current effective MSS, taking SACKs and IP options,
1357 * and even PMTU discovery events into account.
1358 */
1359unsigned int tcp_current_mss(struct sock *sk)
1360{
1361 const struct tcp_sock *tp = tcp_sk(sk);
1362 const struct dst_entry *dst = __sk_dst_get(sk);
1363 u32 mss_now;
1364 unsigned int header_len;
1365 struct tcp_out_options opts;
1366 struct tcp_md5sig_key *md5;
1367
1368 mss_now = tp->mss_cache;
1369
1370 if (dst) {
1371 u32 mtu = dst_mtu(dst);
1372 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1373 mss_now = tcp_sync_mss(sk, mtu);
1374 }
1375
1376 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1377 sizeof(struct tcphdr);
1378 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1379 * some common options. If this is an odd packet (because we have SACK
1380 * blocks etc) then our calculated header_len will be different, and
1381 * we have to adjust mss_now correspondingly */
1382 if (header_len != tp->tcp_header_len) {
1383 int delta = (int) header_len - tp->tcp_header_len;
1384 mss_now -= delta;
1385 }
1386
1387 return mss_now;
1388}
1389
1390/* Congestion window validation. (RFC2861) */
1391static void tcp_cwnd_validate(struct sock *sk)
1392{
1393 struct tcp_sock *tp = tcp_sk(sk);
1394
1395 if (tp->packets_out >= tp->snd_cwnd) {
1396 /* Network is feed fully. */
1397 tp->snd_cwnd_used = 0;
1398 tp->snd_cwnd_stamp = tcp_time_stamp;
1399 } else {
1400 /* Network starves. */
1401 if (tp->packets_out > tp->snd_cwnd_used)
1402 tp->snd_cwnd_used = tp->packets_out;
1403
1404 if (sysctl_tcp_slow_start_after_idle &&
1405 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1406 tcp_cwnd_application_limited(sk);
1407 }
1408}
1409
1410/* Minshall's variant of the Nagle send check. */
1411static bool tcp_minshall_check(const struct tcp_sock *tp)
1412{
1413 return after(tp->snd_sml, tp->snd_una) &&
1414 !after(tp->snd_sml, tp->snd_nxt);
1415}
1416
1417/* Update snd_sml if this skb is under mss
1418 * Note that a TSO packet might end with a sub-mss segment
1419 * The test is really :
1420 * if ((skb->len % mss) != 0)
1421 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1422 * But we can avoid doing the divide again given we already have
1423 * skb_pcount = skb->len / mss_now
1424 */
1425static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1426 const struct sk_buff *skb)
1427{
1428 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1429 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1430}
1431
1432/* Return false, if packet can be sent now without violation Nagle's rules:
1433 * 1. It is full sized. (provided by caller in %partial bool)
1434 * 2. Or it contains FIN. (already checked by caller)
1435 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1436 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1437 * With Minshall's modification: all sent small packets are ACKed.
1438 */
1439static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1440 int nonagle)
1441{
1442 return partial &&
1443 ((nonagle & TCP_NAGLE_CORK) ||
1444 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1445}
1446/* Returns the portion of skb which can be sent right away */
1447static unsigned int tcp_mss_split_point(const struct sock *sk,
1448 const struct sk_buff *skb,
1449 unsigned int mss_now,
1450 unsigned int max_segs,
1451 int nonagle)
1452{
1453 const struct tcp_sock *tp = tcp_sk(sk);
1454 u32 partial, needed, window, max_len;
1455
1456 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1457 max_len = mss_now * max_segs;
1458
1459 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1460 return max_len;
1461
1462 needed = min(skb->len, window);
1463
1464 if (max_len <= needed)
1465 return max_len;
1466
1467 partial = needed % mss_now;
1468 /* If last segment is not a full MSS, check if Nagle rules allow us
1469 * to include this last segment in this skb.
1470 * Otherwise, we'll split the skb at last MSS boundary
1471 */
1472 if (tcp_nagle_check(partial != 0, tp, nonagle))
1473 return needed - partial;
1474
1475 return needed;
1476}
1477
1478/* Can at least one segment of SKB be sent right now, according to the
1479 * congestion window rules? If so, return how many segments are allowed.
1480 */
1481static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1482 const struct sk_buff *skb)
1483{
1484 u32 in_flight, cwnd;
1485
1486 /* Don't be strict about the congestion window for the final FIN. */
1487 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1488 tcp_skb_pcount(skb) == 1)
1489 return 1;
1490
1491 in_flight = tcp_packets_in_flight(tp);
1492 cwnd = tp->snd_cwnd;
1493 if (in_flight < cwnd)
1494 return (cwnd - in_flight);
1495
1496 return 0;
1497}
1498
1499/* Initialize TSO state of a skb.
1500 * This must be invoked the first time we consider transmitting
1501 * SKB onto the wire.
1502 */
1503static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb,
1504 unsigned int mss_now)
1505{
1506 int tso_segs = tcp_skb_pcount(skb);
1507
1508 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1509 tcp_set_skb_tso_segs(sk, skb, mss_now);
1510 tso_segs = tcp_skb_pcount(skb);
1511 }
1512 return tso_segs;
1513}
1514
1515
1516/* Return true if the Nagle test allows this packet to be
1517 * sent now.
1518 */
1519static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1520 unsigned int cur_mss, int nonagle)
1521{
1522 /* Nagle rule does not apply to frames, which sit in the middle of the
1523 * write_queue (they have no chances to get new data).
1524 *
1525 * This is implemented in the callers, where they modify the 'nonagle'
1526 * argument based upon the location of SKB in the send queue.
1527 */
1528 if (nonagle & TCP_NAGLE_PUSH)
1529 return true;
1530
1531 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1532 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1533 return true;
1534
1535 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
1536 return true;
1537
1538 return false;
1539}
1540
1541/* Does at least the first segment of SKB fit into the send window? */
1542static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1543 const struct sk_buff *skb,
1544 unsigned int cur_mss)
1545{
1546 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1547
1548 if (skb->len > cur_mss)
1549 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1550
1551 return !after(end_seq, tcp_wnd_end(tp));
1552}
1553
1554/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1555 * should be put on the wire right now. If so, it returns the number of
1556 * packets allowed by the congestion window.
1557 */
1558static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1559 unsigned int cur_mss, int nonagle)
1560{
1561 const struct tcp_sock *tp = tcp_sk(sk);
1562 unsigned int cwnd_quota;
1563
1564 tcp_init_tso_segs(sk, skb, cur_mss);
1565
1566 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
1567 return 0;
1568
1569 cwnd_quota = tcp_cwnd_test(tp, skb);
1570 if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1571 cwnd_quota = 0;
1572
1573 return cwnd_quota;
1574}
1575
1576/* Test if sending is allowed right now. */
1577bool tcp_may_send_now(struct sock *sk)
1578{
1579 const struct tcp_sock *tp = tcp_sk(sk);
1580 struct sk_buff *skb = tcp_send_head(sk);
1581
1582 return skb &&
1583 tcp_snd_test(sk, skb, tcp_current_mss(sk),
1584 (tcp_skb_is_last(sk, skb) ?
1585 tp->nonagle : TCP_NAGLE_PUSH));
1586}
1587
1588/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1589 * which is put after SKB on the list. It is very much like
1590 * tcp_fragment() except that it may make several kinds of assumptions
1591 * in order to speed up the splitting operation. In particular, we
1592 * know that all the data is in scatter-gather pages, and that the
1593 * packet has never been sent out before (and thus is not cloned).
1594 */
1595static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1596 unsigned int mss_now, gfp_t gfp)
1597{
1598 struct sk_buff *buff;
1599 int nlen = skb->len - len;
1600 u8 flags;
1601
1602 /* All of a TSO frame must be composed of paged data. */
1603 if (skb->len != skb->data_len)
1604 return tcp_fragment(sk, skb, len, mss_now);
1605
1606 buff = sk_stream_alloc_skb(sk, 0, gfp);
1607 if (unlikely(buff == NULL))
1608 return -ENOMEM;
1609
1610 sk->sk_wmem_queued += buff->truesize;
1611 sk_mem_charge(sk, buff->truesize);
1612 buff->truesize += nlen;
1613 skb->truesize -= nlen;
1614
1615 /* Correct the sequence numbers. */
1616 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1617 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1618 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1619
1620 /* PSH and FIN should only be set in the second packet. */
1621 flags = TCP_SKB_CB(skb)->tcp_flags;
1622 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1623 TCP_SKB_CB(buff)->tcp_flags = flags;
1624
1625 /* This packet was never sent out yet, so no SACK bits. */
1626 TCP_SKB_CB(buff)->sacked = 0;
1627
1628 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1629 skb_split(skb, buff, len);
1630
1631 /* Fix up tso_factor for both original and new SKB. */
1632 tcp_set_skb_tso_segs(sk, skb, mss_now);
1633 tcp_set_skb_tso_segs(sk, buff, mss_now);
1634
1635 /* Link BUFF into the send queue. */
1636 skb_header_release(buff);
1637 tcp_insert_write_queue_after(skb, buff, sk);
1638
1639 return 0;
1640}
1641
1642/* Try to defer sending, if possible, in order to minimize the amount
1643 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1644 *
1645 * This algorithm is from John Heffner.
1646 */
1647static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1648{
1649 struct tcp_sock *tp = tcp_sk(sk);
1650 const struct inet_connection_sock *icsk = inet_csk(sk);
1651 u32 send_win, cong_win, limit, in_flight;
1652 int win_divisor;
1653
1654 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1655 goto send_now;
1656
1657 if (icsk->icsk_ca_state != TCP_CA_Open)
1658 goto send_now;
1659
1660 /* Defer for less than two clock ticks. */
1661 if (tp->tso_deferred &&
1662 (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1)
1663 goto send_now;
1664
1665 in_flight = tcp_packets_in_flight(tp);
1666
1667 BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1668
1669 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1670
1671 /* From in_flight test above, we know that cwnd > in_flight. */
1672 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1673
1674 limit = min(send_win, cong_win);
1675
1676 /* If a full-sized TSO skb can be sent, do it. */
1677 if (limit >= min_t(unsigned int, sk->sk_gso_max_size,
1678 tp->xmit_size_goal_segs * tp->mss_cache))
1679 goto send_now;
1680
1681 /* Middle in queue won't get any more data, full sendable already? */
1682 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
1683 goto send_now;
1684
1685 win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
1686 if (win_divisor) {
1687 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1688
1689 /* If at least some fraction of a window is available,
1690 * just use it.
1691 */
1692 chunk /= win_divisor;
1693 if (limit >= chunk)
1694 goto send_now;
1695 } else {
1696 /* Different approach, try not to defer past a single
1697 * ACK. Receiver should ACK every other full sized
1698 * frame, so if we have space for more than 3 frames
1699 * then send now.
1700 */
1701 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
1702 goto send_now;
1703 }
1704
1705 /* Ok, it looks like it is advisable to defer.
1706 * Do not rearm the timer if already set to not break TCP ACK clocking.
1707 */
1708 if (!tp->tso_deferred)
1709 tp->tso_deferred = 1 | (jiffies << 1);
1710
1711 return true;
1712
1713send_now:
1714 tp->tso_deferred = 0;
1715 return false;
1716}
1717
1718/* Create a new MTU probe if we are ready.
1719 * MTU probe is regularly attempting to increase the path MTU by
1720 * deliberately sending larger packets. This discovers routing
1721 * changes resulting in larger path MTUs.
1722 *
1723 * Returns 0 if we should wait to probe (no cwnd available),
1724 * 1 if a probe was sent,
1725 * -1 otherwise
1726 */
1727static int tcp_mtu_probe(struct sock *sk)
1728{
1729 struct tcp_sock *tp = tcp_sk(sk);
1730 struct inet_connection_sock *icsk = inet_csk(sk);
1731 struct sk_buff *skb, *nskb, *next;
1732 int len;
1733 int probe_size;
1734 int size_needed;
1735 int copy;
1736 int mss_now;
1737
1738 /* Not currently probing/verifying,
1739 * not in recovery,
1740 * have enough cwnd, and
1741 * not SACKing (the variable headers throw things off) */
1742 if (!icsk->icsk_mtup.enabled ||
1743 icsk->icsk_mtup.probe_size ||
1744 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
1745 tp->snd_cwnd < 11 ||
1746 tp->rx_opt.num_sacks || tp->rx_opt.dsack)
1747 return -1;
1748
1749 /* Very simple search strategy: just double the MSS. */
1750 mss_now = tcp_current_mss(sk);
1751 probe_size = 2 * tp->mss_cache;
1752 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1753 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
1754 /* TODO: set timer for probe_converge_event */
1755 return -1;
1756 }
1757
1758 /* Have enough data in the send queue to probe? */
1759 if (tp->write_seq - tp->snd_nxt < size_needed)
1760 return -1;
1761
1762 if (tp->snd_wnd < size_needed)
1763 return -1;
1764 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1765 return 0;
1766
1767 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1768 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
1769 if (!tcp_packets_in_flight(tp))
1770 return -1;
1771 else
1772 return 0;
1773 }
1774
1775 /* We're allowed to probe. Build it now. */
1776 if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL)
1777 return -1;
1778 sk->sk_wmem_queued += nskb->truesize;
1779 sk_mem_charge(sk, nskb->truesize);
1780
1781 skb = tcp_send_head(sk);
1782
1783 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
1784 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
1785 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
1786 TCP_SKB_CB(nskb)->sacked = 0;
1787 nskb->csum = 0;
1788 nskb->ip_summed = skb->ip_summed;
1789
1790 tcp_insert_write_queue_before(nskb, skb, sk);
1791
1792 len = 0;
1793 tcp_for_write_queue_from_safe(skb, next, sk) {
1794 copy = min_t(int, skb->len, probe_size - len);
1795 if (nskb->ip_summed)
1796 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
1797 else
1798 nskb->csum = skb_copy_and_csum_bits(skb, 0,
1799 skb_put(nskb, copy),
1800 copy, nskb->csum);
1801
1802 if (skb->len <= copy) {
1803 /* We've eaten all the data from this skb.
1804 * Throw it away. */
1805 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1806 tcp_unlink_write_queue(skb, sk);
1807 sk_wmem_free_skb(sk, skb);
1808 } else {
1809 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
1810 ~(TCPHDR_FIN|TCPHDR_PSH);
1811 if (!skb_shinfo(skb)->nr_frags) {
1812 skb_pull(skb, copy);
1813 if (skb->ip_summed != CHECKSUM_PARTIAL)
1814 skb->csum = csum_partial(skb->data,
1815 skb->len, 0);
1816 } else {
1817 __pskb_trim_head(skb, copy);
1818 tcp_set_skb_tso_segs(sk, skb, mss_now);
1819 }
1820 TCP_SKB_CB(skb)->seq += copy;
1821 }
1822
1823 len += copy;
1824
1825 if (len >= probe_size)
1826 break;
1827 }
1828 tcp_init_tso_segs(sk, nskb, nskb->len);
1829
1830 /* We're ready to send. If this fails, the probe will
1831 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1832 TCP_SKB_CB(nskb)->when = tcp_time_stamp;
1833 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
1834 /* Decrement cwnd here because we are sending
1835 * effectively two packets. */
1836 tp->snd_cwnd--;
1837 tcp_event_new_data_sent(sk, nskb);
1838
1839 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1840 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
1841 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
1842
1843 return 1;
1844 }
1845
1846 return -1;
1847}
1848
1849/* This routine writes packets to the network. It advances the
1850 * send_head. This happens as incoming acks open up the remote
1851 * window for us.
1852 *
1853 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1854 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1855 * account rare use of URG, this is not a big flaw.
1856 *
1857 * Send at most one packet when push_one > 0. Temporarily ignore
1858 * cwnd limit to force at most one packet out when push_one == 2.
1859
1860 * Returns true, if no segments are in flight and we have queued segments,
1861 * but cannot send anything now because of SWS or another problem.
1862 */
1863static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
1864 int push_one, gfp_t gfp)
1865{
1866 struct tcp_sock *tp = tcp_sk(sk);
1867 struct sk_buff *skb;
1868 unsigned int tso_segs, sent_pkts;
1869 int cwnd_quota;
1870 int result;
1871
1872 sent_pkts = 0;
1873
1874 if (!push_one) {
1875 /* Do MTU probing. */
1876 result = tcp_mtu_probe(sk);
1877 if (!result) {
1878 return false;
1879 } else if (result > 0) {
1880 sent_pkts = 1;
1881 }
1882 }
1883
1884 while ((skb = tcp_send_head(sk))) {
1885 unsigned int limit;
1886
1887 tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1888 BUG_ON(!tso_segs);
1889
1890 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE)
1891 goto repair; /* Skip network transmission */
1892
1893 cwnd_quota = tcp_cwnd_test(tp, skb);
1894 if (!cwnd_quota) {
1895 if (push_one == 2)
1896 /* Force out a loss probe pkt. */
1897 cwnd_quota = 1;
1898 else
1899 break;
1900 }
1901
1902 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
1903 break;
1904
1905 if (tso_segs == 1) {
1906 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
1907 (tcp_skb_is_last(sk, skb) ?
1908 nonagle : TCP_NAGLE_PUSH))))
1909 break;
1910 } else {
1911 if (!push_one && tcp_tso_should_defer(sk, skb))
1912 break;
1913 }
1914
1915 /* TCP Small Queues :
1916 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
1917 * This allows for :
1918 * - better RTT estimation and ACK scheduling
1919 * - faster recovery
1920 * - high rates
1921 * Alas, some drivers / subsystems require a fair amount
1922 * of queued bytes to ensure line rate.
1923 * One example is wifi aggregation (802.11 AMPDU)
1924 */
1925 limit = max_t(unsigned int, sysctl_tcp_limit_output_bytes,
1926 sk->sk_pacing_rate >> 10);
1927
1928 if (atomic_read(&sk->sk_wmem_alloc) > limit) {
1929 set_bit(TSQ_THROTTLED, &tp->tsq_flags);
1930 /* It is possible TX completion already happened
1931 * before we set TSQ_THROTTLED, so we must
1932 * test again the condition.
1933 * We abuse smp_mb__after_clear_bit() because
1934 * there is no smp_mb__after_set_bit() yet
1935 */
1936 smp_mb__after_clear_bit();
1937 if (atomic_read(&sk->sk_wmem_alloc) > limit)
1938 break;
1939 }
1940
1941 limit = mss_now;
1942 if (tso_segs > 1 && !tcp_urg_mode(tp))
1943 limit = tcp_mss_split_point(sk, skb, mss_now,
1944 min_t(unsigned int,
1945 cwnd_quota,
1946 sk->sk_gso_max_segs),
1947 nonagle);
1948
1949 if (skb->len > limit &&
1950 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
1951 break;
1952
1953 TCP_SKB_CB(skb)->when = tcp_time_stamp;
1954
1955 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
1956 break;
1957
1958repair:
1959 /* Advance the send_head. This one is sent out.
1960 * This call will increment packets_out.
1961 */
1962 tcp_event_new_data_sent(sk, skb);
1963
1964 tcp_minshall_update(tp, mss_now, skb);
1965 sent_pkts += tcp_skb_pcount(skb);
1966
1967 if (push_one)
1968 break;
1969 }
1970
1971 if (likely(sent_pkts)) {
1972 if (tcp_in_cwnd_reduction(sk))
1973 tp->prr_out += sent_pkts;
1974
1975 /* Send one loss probe per tail loss episode. */
1976 if (push_one != 2)
1977 tcp_schedule_loss_probe(sk);
1978 tcp_cwnd_validate(sk);
1979 return false;
1980 }
1981 return (push_one == 2) || (!tp->packets_out && tcp_send_head(sk));
1982}
1983
1984bool tcp_schedule_loss_probe(struct sock *sk)
1985{
1986 struct inet_connection_sock *icsk = inet_csk(sk);
1987 struct tcp_sock *tp = tcp_sk(sk);
1988 u32 timeout, tlp_time_stamp, rto_time_stamp;
1989 u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
1990
1991 if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
1992 return false;
1993 /* No consecutive loss probes. */
1994 if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
1995 tcp_rearm_rto(sk);
1996 return false;
1997 }
1998 /* Don't do any loss probe on a Fast Open connection before 3WHS
1999 * finishes.
2000 */
2001 if (sk->sk_state == TCP_SYN_RECV)
2002 return false;
2003
2004 /* TLP is only scheduled when next timer event is RTO. */
2005 if (icsk->icsk_pending != ICSK_TIME_RETRANS)
2006 return false;
2007
2008 /* Schedule a loss probe in 2*RTT for SACK capable connections
2009 * in Open state, that are either limited by cwnd or application.
2010 */
2011 if (sysctl_tcp_early_retrans < 3 || !tp->srtt_us || !tp->packets_out ||
2012 !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
2013 return false;
2014
2015 if ((tp->snd_cwnd > tcp_packets_in_flight(tp)) &&
2016 tcp_send_head(sk))
2017 return false;
2018
2019 /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2020 * for delayed ack when there's one outstanding packet.
2021 */
2022 timeout = rtt << 1;
2023 if (tp->packets_out == 1)
2024 timeout = max_t(u32, timeout,
2025 (rtt + (rtt >> 1) + TCP_DELACK_MAX));
2026 timeout = max_t(u32, timeout, msecs_to_jiffies(10));
2027
2028 /* If RTO is shorter, just schedule TLP in its place. */
2029 tlp_time_stamp = tcp_time_stamp + timeout;
2030 rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout;
2031 if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) {
2032 s32 delta = rto_time_stamp - tcp_time_stamp;
2033 if (delta > 0)
2034 timeout = delta;
2035 }
2036
2037 inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
2038 TCP_RTO_MAX);
2039 return true;
2040}
2041
2042/* When probe timeout (PTO) fires, send a new segment if one exists, else
2043 * retransmit the last segment.
2044 */
2045void tcp_send_loss_probe(struct sock *sk)
2046{
2047 struct tcp_sock *tp = tcp_sk(sk);
2048 struct sk_buff *skb;
2049 int pcount;
2050 int mss = tcp_current_mss(sk);
2051 int err = -1;
2052
2053 if (tcp_send_head(sk) != NULL) {
2054 err = tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2055 goto rearm_timer;
2056 }
2057
2058 /* At most one outstanding TLP retransmission. */
2059 if (tp->tlp_high_seq)
2060 goto rearm_timer;
2061
2062 /* Retransmit last segment. */
2063 skb = tcp_write_queue_tail(sk);
2064 if (WARN_ON(!skb))
2065 goto rearm_timer;
2066
2067 pcount = tcp_skb_pcount(skb);
2068 if (WARN_ON(!pcount))
2069 goto rearm_timer;
2070
2071 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2072 if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss)))
2073 goto rearm_timer;
2074 skb = tcp_write_queue_tail(sk);
2075 }
2076
2077 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2078 goto rearm_timer;
2079
2080 /* Probe with zero data doesn't trigger fast recovery. */
2081 if (skb->len > 0)
2082 err = __tcp_retransmit_skb(sk, skb);
2083
2084 /* Record snd_nxt for loss detection. */
2085 if (likely(!err))
2086 tp->tlp_high_seq = tp->snd_nxt;
2087
2088rearm_timer:
2089 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2090 inet_csk(sk)->icsk_rto,
2091 TCP_RTO_MAX);
2092
2093 if (likely(!err))
2094 NET_INC_STATS_BH(sock_net(sk),
2095 LINUX_MIB_TCPLOSSPROBES);
2096}
2097
2098/* Push out any pending frames which were held back due to
2099 * TCP_CORK or attempt at coalescing tiny packets.
2100 * The socket must be locked by the caller.
2101 */
2102void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2103 int nonagle)
2104{
2105 /* If we are closed, the bytes will have to remain here.
2106 * In time closedown will finish, we empty the write queue and
2107 * all will be happy.
2108 */
2109 if (unlikely(sk->sk_state == TCP_CLOSE))
2110 return;
2111
2112 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2113 sk_gfp_atomic(sk, GFP_ATOMIC)))
2114 tcp_check_probe_timer(sk);
2115}
2116
2117/* Send _single_ skb sitting at the send head. This function requires
2118 * true push pending frames to setup probe timer etc.
2119 */
2120void tcp_push_one(struct sock *sk, unsigned int mss_now)
2121{
2122 struct sk_buff *skb = tcp_send_head(sk);
2123
2124 BUG_ON(!skb || skb->len < mss_now);
2125
2126 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2127}
2128
2129/* This function returns the amount that we can raise the
2130 * usable window based on the following constraints
2131 *
2132 * 1. The window can never be shrunk once it is offered (RFC 793)
2133 * 2. We limit memory per socket
2134 *
2135 * RFC 1122:
2136 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2137 * RECV.NEXT + RCV.WIN fixed until:
2138 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2139 *
2140 * i.e. don't raise the right edge of the window until you can raise
2141 * it at least MSS bytes.
2142 *
2143 * Unfortunately, the recommended algorithm breaks header prediction,
2144 * since header prediction assumes th->window stays fixed.
2145 *
2146 * Strictly speaking, keeping th->window fixed violates the receiver
2147 * side SWS prevention criteria. The problem is that under this rule
2148 * a stream of single byte packets will cause the right side of the
2149 * window to always advance by a single byte.
2150 *
2151 * Of course, if the sender implements sender side SWS prevention
2152 * then this will not be a problem.
2153 *
2154 * BSD seems to make the following compromise:
2155 *
2156 * If the free space is less than the 1/4 of the maximum
2157 * space available and the free space is less than 1/2 mss,
2158 * then set the window to 0.
2159 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2160 * Otherwise, just prevent the window from shrinking
2161 * and from being larger than the largest representable value.
2162 *
2163 * This prevents incremental opening of the window in the regime
2164 * where TCP is limited by the speed of the reader side taking
2165 * data out of the TCP receive queue. It does nothing about
2166 * those cases where the window is constrained on the sender side
2167 * because the pipeline is full.
2168 *
2169 * BSD also seems to "accidentally" limit itself to windows that are a
2170 * multiple of MSS, at least until the free space gets quite small.
2171 * This would appear to be a side effect of the mbuf implementation.
2172 * Combining these two algorithms results in the observed behavior
2173 * of having a fixed window size at almost all times.
2174 *
2175 * Below we obtain similar behavior by forcing the offered window to
2176 * a multiple of the mss when it is feasible to do so.
2177 *
2178 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2179 * Regular options like TIMESTAMP are taken into account.
2180 */
2181u32 __tcp_select_window(struct sock *sk)
2182{
2183 struct inet_connection_sock *icsk = inet_csk(sk);
2184 struct tcp_sock *tp = tcp_sk(sk);
2185 /* MSS for the peer's data. Previous versions used mss_clamp
2186 * here. I don't know if the value based on our guesses
2187 * of peer's MSS is better for the performance. It's more correct
2188 * but may be worse for the performance because of rcv_mss
2189 * fluctuations. --SAW 1998/11/1
2190 */
2191 int mss = icsk->icsk_ack.rcv_mss;
2192 int free_space = tcp_space(sk);
2193 int allowed_space = tcp_full_space(sk);
2194 int full_space = min_t(int, tp->window_clamp, allowed_space);
2195 int window;
2196
2197 if (mss > full_space)
2198 mss = full_space;
2199
2200 if (free_space < (full_space >> 1)) {
2201 icsk->icsk_ack.quick = 0;
2202
2203 if (sk_under_memory_pressure(sk))
2204 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2205 4U * tp->advmss);
2206
2207 /* free_space might become our new window, make sure we don't
2208 * increase it due to wscale.
2209 */
2210 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2211
2212 /* if free space is less than mss estimate, or is below 1/16th
2213 * of the maximum allowed, try to move to zero-window, else
2214 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2215 * new incoming data is dropped due to memory limits.
2216 * With large window, mss test triggers way too late in order
2217 * to announce zero window in time before rmem limit kicks in.
2218 */
2219 if (free_space < (allowed_space >> 4) || free_space < mss)
2220 return 0;
2221 }
2222
2223 if (free_space > tp->rcv_ssthresh)
2224 free_space = tp->rcv_ssthresh;
2225
2226 /* Don't do rounding if we are using window scaling, since the
2227 * scaled window will not line up with the MSS boundary anyway.
2228 */
2229 window = tp->rcv_wnd;
2230 if (tp->rx_opt.rcv_wscale) {
2231 window = free_space;
2232
2233 /* Advertise enough space so that it won't get scaled away.
2234 * Import case: prevent zero window announcement if
2235 * 1<<rcv_wscale > mss.
2236 */
2237 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
2238 window = (((window >> tp->rx_opt.rcv_wscale) + 1)
2239 << tp->rx_opt.rcv_wscale);
2240 } else {
2241 /* Get the largest window that is a nice multiple of mss.
2242 * Window clamp already applied above.
2243 * If our current window offering is within 1 mss of the
2244 * free space we just keep it. This prevents the divide
2245 * and multiply from happening most of the time.
2246 * We also don't do any window rounding when the free space
2247 * is too small.
2248 */
2249 if (window <= free_space - mss || window > free_space)
2250 window = (free_space / mss) * mss;
2251 else if (mss == full_space &&
2252 free_space > window + (full_space >> 1))
2253 window = free_space;
2254 }
2255
2256 return window;
2257}
2258
2259/* Collapses two adjacent SKB's during retransmission. */
2260static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
2261{
2262 struct tcp_sock *tp = tcp_sk(sk);
2263 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2264 int skb_size, next_skb_size;
2265
2266 skb_size = skb->len;
2267 next_skb_size = next_skb->len;
2268
2269 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2270
2271 tcp_highest_sack_combine(sk, next_skb, skb);
2272
2273 tcp_unlink_write_queue(next_skb, sk);
2274
2275 skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
2276 next_skb_size);
2277
2278 if (next_skb->ip_summed == CHECKSUM_PARTIAL)
2279 skb->ip_summed = CHECKSUM_PARTIAL;
2280
2281 if (skb->ip_summed != CHECKSUM_PARTIAL)
2282 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
2283
2284 /* Update sequence range on original skb. */
2285 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2286
2287 /* Merge over control information. This moves PSH/FIN etc. over */
2288 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2289
2290 /* All done, get rid of second SKB and account for it so
2291 * packet counting does not break.
2292 */
2293 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2294
2295 /* changed transmit queue under us so clear hints */
2296 tcp_clear_retrans_hints_partial(tp);
2297 if (next_skb == tp->retransmit_skb_hint)
2298 tp->retransmit_skb_hint = skb;
2299
2300 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2301
2302 sk_wmem_free_skb(sk, next_skb);
2303}
2304
2305/* Check if coalescing SKBs is legal. */
2306static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2307{
2308 if (tcp_skb_pcount(skb) > 1)
2309 return false;
2310 /* TODO: SACK collapsing could be used to remove this condition */
2311 if (skb_shinfo(skb)->nr_frags != 0)
2312 return false;
2313 if (skb_cloned(skb))
2314 return false;
2315 if (skb == tcp_send_head(sk))
2316 return false;
2317 /* Some heurestics for collapsing over SACK'd could be invented */
2318 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2319 return false;
2320
2321 return true;
2322}
2323
2324/* Collapse packets in the retransmit queue to make to create
2325 * less packets on the wire. This is only done on retransmission.
2326 */
2327static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2328 int space)
2329{
2330 struct tcp_sock *tp = tcp_sk(sk);
2331 struct sk_buff *skb = to, *tmp;
2332 bool first = true;
2333
2334 if (!sysctl_tcp_retrans_collapse)
2335 return;
2336 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2337 return;
2338
2339 tcp_for_write_queue_from_safe(skb, tmp, sk) {
2340 if (!tcp_can_collapse(sk, skb))
2341 break;
2342
2343 space -= skb->len;
2344
2345 if (first) {
2346 first = false;
2347 continue;
2348 }
2349
2350 if (space < 0)
2351 break;
2352 /* Punt if not enough space exists in the first SKB for
2353 * the data in the second
2354 */
2355 if (skb->len > skb_availroom(to))
2356 break;
2357
2358 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2359 break;
2360
2361 tcp_collapse_retrans(sk, to);
2362 }
2363}
2364
2365/* This retransmits one SKB. Policy decisions and retransmit queue
2366 * state updates are done by the caller. Returns non-zero if an
2367 * error occurred which prevented the send.
2368 */
2369int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2370{
2371 struct tcp_sock *tp = tcp_sk(sk);
2372 struct inet_connection_sock *icsk = inet_csk(sk);
2373 unsigned int cur_mss;
2374 int err;
2375
2376 /* Inconslusive MTU probe */
2377 if (icsk->icsk_mtup.probe_size) {
2378 icsk->icsk_mtup.probe_size = 0;
2379 }
2380
2381 /* Do not sent more than we queued. 1/4 is reserved for possible
2382 * copying overhead: fragmentation, tunneling, mangling etc.
2383 */
2384 if (atomic_read(&sk->sk_wmem_alloc) >
2385 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
2386 return -EAGAIN;
2387
2388 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2389 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
2390 BUG();
2391 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
2392 return -ENOMEM;
2393 }
2394
2395 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
2396 return -EHOSTUNREACH; /* Routing failure or similar. */
2397
2398 cur_mss = tcp_current_mss(sk);
2399
2400 /* If receiver has shrunk his window, and skb is out of
2401 * new window, do not retransmit it. The exception is the
2402 * case, when window is shrunk to zero. In this case
2403 * our retransmit serves as a zero window probe.
2404 */
2405 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
2406 TCP_SKB_CB(skb)->seq != tp->snd_una)
2407 return -EAGAIN;
2408
2409 if (skb->len > cur_mss) {
2410 if (tcp_fragment(sk, skb, cur_mss, cur_mss))
2411 return -ENOMEM; /* We'll try again later. */
2412 } else {
2413 int oldpcount = tcp_skb_pcount(skb);
2414
2415 if (unlikely(oldpcount > 1)) {
2416 if (skb_unclone(skb, GFP_ATOMIC))
2417 return -ENOMEM;
2418 tcp_init_tso_segs(sk, skb, cur_mss);
2419 tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
2420 }
2421 }
2422
2423 tcp_retrans_try_collapse(sk, skb, cur_mss);
2424
2425 /* Make a copy, if the first transmission SKB clone we made
2426 * is still in somebody's hands, else make a clone.
2427 */
2428 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2429
2430 /* make sure skb->data is aligned on arches that require it
2431 * and check if ack-trimming & collapsing extended the headroom
2432 * beyond what csum_start can cover.
2433 */
2434 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
2435 skb_headroom(skb) >= 0xFFFF)) {
2436 struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
2437 GFP_ATOMIC);
2438 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
2439 -ENOBUFS;
2440 } else {
2441 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2442 }
2443
2444 if (likely(!err)) {
2445 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2446 /* Update global TCP statistics. */
2447 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
2448 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2449 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2450 tp->total_retrans++;
2451 }
2452 return err;
2453}
2454
2455int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2456{
2457 struct tcp_sock *tp = tcp_sk(sk);
2458 int err = __tcp_retransmit_skb(sk, skb);
2459
2460 if (err == 0) {
2461#if FASTRETRANS_DEBUG > 0
2462 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2463 net_dbg_ratelimited("retrans_out leaked\n");
2464 }
2465#endif
2466 if (!tp->retrans_out)
2467 tp->lost_retrans_low = tp->snd_nxt;
2468 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
2469 tp->retrans_out += tcp_skb_pcount(skb);
2470
2471 /* Save stamp of the first retransmit. */
2472 if (!tp->retrans_stamp)
2473 tp->retrans_stamp = TCP_SKB_CB(skb)->when;
2474
2475 tp->undo_retrans += tcp_skb_pcount(skb);
2476
2477 /* snd_nxt is stored to detect loss of retransmitted segment,
2478 * see tcp_input.c tcp_sacktag_write_queue().
2479 */
2480 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
2481 } else {
2482 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2483 }
2484 return err;
2485}
2486
2487/* Check if we forward retransmits are possible in the current
2488 * window/congestion state.
2489 */
2490static bool tcp_can_forward_retransmit(struct sock *sk)
2491{
2492 const struct inet_connection_sock *icsk = inet_csk(sk);
2493 const struct tcp_sock *tp = tcp_sk(sk);
2494
2495 /* Forward retransmissions are possible only during Recovery. */
2496 if (icsk->icsk_ca_state != TCP_CA_Recovery)
2497 return false;
2498
2499 /* No forward retransmissions in Reno are possible. */
2500 if (tcp_is_reno(tp))
2501 return false;
2502
2503 /* Yeah, we have to make difficult choice between forward transmission
2504 * and retransmission... Both ways have their merits...
2505 *
2506 * For now we do not retransmit anything, while we have some new
2507 * segments to send. In the other cases, follow rule 3 for
2508 * NextSeg() specified in RFC3517.
2509 */
2510
2511 if (tcp_may_send_now(sk))
2512 return false;
2513
2514 return true;
2515}
2516
2517/* This gets called after a retransmit timeout, and the initially
2518 * retransmitted data is acknowledged. It tries to continue
2519 * resending the rest of the retransmit queue, until either
2520 * we've sent it all or the congestion window limit is reached.
2521 * If doing SACK, the first ACK which comes back for a timeout
2522 * based retransmit packet might feed us FACK information again.
2523 * If so, we use it to avoid unnecessarily retransmissions.
2524 */
2525void tcp_xmit_retransmit_queue(struct sock *sk)
2526{
2527 const struct inet_connection_sock *icsk = inet_csk(sk);
2528 struct tcp_sock *tp = tcp_sk(sk);
2529 struct sk_buff *skb;
2530 struct sk_buff *hole = NULL;
2531 u32 last_lost;
2532 int mib_idx;
2533 int fwd_rexmitting = 0;
2534
2535 if (!tp->packets_out)
2536 return;
2537
2538 if (!tp->lost_out)
2539 tp->retransmit_high = tp->snd_una;
2540
2541 if (tp->retransmit_skb_hint) {
2542 skb = tp->retransmit_skb_hint;
2543 last_lost = TCP_SKB_CB(skb)->end_seq;
2544 if (after(last_lost, tp->retransmit_high))
2545 last_lost = tp->retransmit_high;
2546 } else {
2547 skb = tcp_write_queue_head(sk);
2548 last_lost = tp->snd_una;
2549 }
2550
2551 tcp_for_write_queue_from(skb, sk) {
2552 __u8 sacked = TCP_SKB_CB(skb)->sacked;
2553
2554 if (skb == tcp_send_head(sk))
2555 break;
2556 /* we could do better than to assign each time */
2557 if (hole == NULL)
2558 tp->retransmit_skb_hint = skb;
2559
2560 /* Assume this retransmit will generate
2561 * only one packet for congestion window
2562 * calculation purposes. This works because
2563 * tcp_retransmit_skb() will chop up the
2564 * packet to be MSS sized and all the
2565 * packet counting works out.
2566 */
2567 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
2568 return;
2569
2570 if (fwd_rexmitting) {
2571begin_fwd:
2572 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
2573 break;
2574 mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2575
2576 } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2577 tp->retransmit_high = last_lost;
2578 if (!tcp_can_forward_retransmit(sk))
2579 break;
2580 /* Backtrack if necessary to non-L'ed skb */
2581 if (hole != NULL) {
2582 skb = hole;
2583 hole = NULL;
2584 }
2585 fwd_rexmitting = 1;
2586 goto begin_fwd;
2587
2588 } else if (!(sacked & TCPCB_LOST)) {
2589 if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2590 hole = skb;
2591 continue;
2592
2593 } else {
2594 last_lost = TCP_SKB_CB(skb)->end_seq;
2595 if (icsk->icsk_ca_state != TCP_CA_Loss)
2596 mib_idx = LINUX_MIB_TCPFASTRETRANS;
2597 else
2598 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
2599 }
2600
2601 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
2602 continue;
2603
2604 if (tcp_retransmit_skb(sk, skb))
2605 return;
2606
2607 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2608
2609 if (tcp_in_cwnd_reduction(sk))
2610 tp->prr_out += tcp_skb_pcount(skb);
2611
2612 if (skb == tcp_write_queue_head(sk))
2613 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2614 inet_csk(sk)->icsk_rto,
2615 TCP_RTO_MAX);
2616 }
2617}
2618
2619/* Send a fin. The caller locks the socket for us. This cannot be
2620 * allowed to fail queueing a FIN frame under any circumstances.
2621 */
2622void tcp_send_fin(struct sock *sk)
2623{
2624 struct tcp_sock *tp = tcp_sk(sk);
2625 struct sk_buff *skb = tcp_write_queue_tail(sk);
2626 int mss_now;
2627
2628 /* Optimization, tack on the FIN if we have a queue of
2629 * unsent frames. But be careful about outgoing SACKS
2630 * and IP options.
2631 */
2632 mss_now = tcp_current_mss(sk);
2633
2634 if (tcp_send_head(sk) != NULL) {
2635 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_FIN;
2636 TCP_SKB_CB(skb)->end_seq++;
2637 tp->write_seq++;
2638 } else {
2639 /* Socket is locked, keep trying until memory is available. */
2640 for (;;) {
2641 skb = alloc_skb_fclone(MAX_TCP_HEADER,
2642 sk->sk_allocation);
2643 if (skb)
2644 break;
2645 yield();
2646 }
2647
2648 /* Reserve space for headers and prepare control bits. */
2649 skb_reserve(skb, MAX_TCP_HEADER);
2650 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2651 tcp_init_nondata_skb(skb, tp->write_seq,
2652 TCPHDR_ACK | TCPHDR_FIN);
2653 tcp_queue_skb(sk, skb);
2654 }
2655 __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
2656}
2657
2658/* We get here when a process closes a file descriptor (either due to
2659 * an explicit close() or as a byproduct of exit()'ing) and there
2660 * was unread data in the receive queue. This behavior is recommended
2661 * by RFC 2525, section 2.17. -DaveM
2662 */
2663void tcp_send_active_reset(struct sock *sk, gfp_t priority)
2664{
2665 struct sk_buff *skb;
2666
2667 /* NOTE: No TCP options attached and we never retransmit this. */
2668 skb = alloc_skb(MAX_TCP_HEADER, priority);
2669 if (!skb) {
2670 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2671 return;
2672 }
2673
2674 /* Reserve space for headers and prepare control bits. */
2675 skb_reserve(skb, MAX_TCP_HEADER);
2676 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
2677 TCPHDR_ACK | TCPHDR_RST);
2678 /* Send it off. */
2679 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2680 if (tcp_transmit_skb(sk, skb, 0, priority))
2681 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2682
2683 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
2684}
2685
2686/* Send a crossed SYN-ACK during socket establishment.
2687 * WARNING: This routine must only be called when we have already sent
2688 * a SYN packet that crossed the incoming SYN that caused this routine
2689 * to get called. If this assumption fails then the initial rcv_wnd
2690 * and rcv_wscale values will not be correct.
2691 */
2692int tcp_send_synack(struct sock *sk)
2693{
2694 struct sk_buff *skb;
2695
2696 skb = tcp_write_queue_head(sk);
2697 if (skb == NULL || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
2698 pr_debug("%s: wrong queue state\n", __func__);
2699 return -EFAULT;
2700 }
2701 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
2702 if (skb_cloned(skb)) {
2703 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
2704 if (nskb == NULL)
2705 return -ENOMEM;
2706 tcp_unlink_write_queue(skb, sk);
2707 skb_header_release(nskb);
2708 __tcp_add_write_queue_head(sk, nskb);
2709 sk_wmem_free_skb(sk, skb);
2710 sk->sk_wmem_queued += nskb->truesize;
2711 sk_mem_charge(sk, nskb->truesize);
2712 skb = nskb;
2713 }
2714
2715 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
2716 TCP_ECN_send_synack(tcp_sk(sk), skb);
2717 }
2718 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2719 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2720}
2721
2722/**
2723 * tcp_make_synack - Prepare a SYN-ACK.
2724 * sk: listener socket
2725 * dst: dst entry attached to the SYNACK
2726 * req: request_sock pointer
2727 *
2728 * Allocate one skb and build a SYNACK packet.
2729 * @dst is consumed : Caller should not use it again.
2730 */
2731struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2732 struct request_sock *req,
2733 struct tcp_fastopen_cookie *foc)
2734{
2735 struct tcp_out_options opts;
2736 struct inet_request_sock *ireq = inet_rsk(req);
2737 struct tcp_sock *tp = tcp_sk(sk);
2738 struct tcphdr *th;
2739 struct sk_buff *skb;
2740 struct tcp_md5sig_key *md5;
2741 int tcp_header_size;
2742 int mss;
2743
2744 skb = sock_wmalloc(sk, MAX_TCP_HEADER, 1, GFP_ATOMIC);
2745 if (unlikely(!skb)) {
2746 dst_release(dst);
2747 return NULL;
2748 }
2749 /* Reserve space for headers. */
2750 skb_reserve(skb, MAX_TCP_HEADER);
2751
2752 skb_dst_set(skb, dst);
2753 security_skb_owned_by(skb, sk);
2754
2755 mss = dst_metric_advmss(dst);
2756 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
2757 mss = tp->rx_opt.user_mss;
2758
2759 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
2760 __u8 rcv_wscale;
2761 /* Set this up on the first call only */
2762 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
2763
2764 /* limit the window selection if the user enforce a smaller rx buffer */
2765 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
2766 (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
2767 req->window_clamp = tcp_full_space(sk);
2768
2769 /* tcp_full_space because it is guaranteed to be the first packet */
2770 tcp_select_initial_window(tcp_full_space(sk),
2771 mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
2772 &req->rcv_wnd,
2773 &req->window_clamp,
2774 ireq->wscale_ok,
2775 &rcv_wscale,
2776 dst_metric(dst, RTAX_INITRWND));
2777 ireq->rcv_wscale = rcv_wscale;
2778 }
2779
2780 memset(&opts, 0, sizeof(opts));
2781#ifdef CONFIG_SYN_COOKIES
2782 if (unlikely(req->cookie_ts))
2783 TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
2784 else
2785#endif
2786 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2787 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5,
2788 foc) + sizeof(*th);
2789
2790 skb_push(skb, tcp_header_size);
2791 skb_reset_transport_header(skb);
2792
2793 th = tcp_hdr(skb);
2794 memset(th, 0, sizeof(struct tcphdr));
2795 th->syn = 1;
2796 th->ack = 1;
2797 TCP_ECN_make_synack(req, th);
2798 th->source = htons(ireq->ir_num);
2799 th->dest = ireq->ir_rmt_port;
2800 /* Setting of flags are superfluous here for callers (and ECE is
2801 * not even correctly set)
2802 */
2803 tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
2804 TCPHDR_SYN | TCPHDR_ACK);
2805
2806 th->seq = htonl(TCP_SKB_CB(skb)->seq);
2807 /* XXX data is queued and acked as is. No buffer/window check */
2808 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
2809
2810 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2811 th->window = htons(min(req->rcv_wnd, 65535U));
2812 tcp_options_write((__be32 *)(th + 1), tp, &opts);
2813 th->doff = (tcp_header_size >> 2);
2814 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_OUTSEGS);
2815
2816#ifdef CONFIG_TCP_MD5SIG
2817 /* Okay, we have all we need - do the md5 hash if needed */
2818 if (md5) {
2819 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
2820 md5, NULL, req, skb);
2821 }
2822#endif
2823
2824 return skb;
2825}
2826EXPORT_SYMBOL(tcp_make_synack);
2827
2828/* Do all connect socket setups that can be done AF independent. */
2829static void tcp_connect_init(struct sock *sk)
2830{
2831 const struct dst_entry *dst = __sk_dst_get(sk);
2832 struct tcp_sock *tp = tcp_sk(sk);
2833 __u8 rcv_wscale;
2834
2835 /* We'll fix this up when we get a response from the other end.
2836 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2837 */
2838 tp->tcp_header_len = sizeof(struct tcphdr) +
2839 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
2840
2841#ifdef CONFIG_TCP_MD5SIG
2842 if (tp->af_specific->md5_lookup(sk, sk) != NULL)
2843 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
2844#endif
2845
2846 /* If user gave his TCP_MAXSEG, record it to clamp */
2847 if (tp->rx_opt.user_mss)
2848 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
2849 tp->max_window = 0;
2850 tcp_mtup_init(sk);
2851 tcp_sync_mss(sk, dst_mtu(dst));
2852
2853 if (!tp->window_clamp)
2854 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
2855 tp->advmss = dst_metric_advmss(dst);
2856 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
2857 tp->advmss = tp->rx_opt.user_mss;
2858
2859 tcp_initialize_rcv_mss(sk);
2860
2861 /* limit the window selection if the user enforce a smaller rx buffer */
2862 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
2863 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
2864 tp->window_clamp = tcp_full_space(sk);
2865
2866 tcp_select_initial_window(tcp_full_space(sk),
2867 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
2868 &tp->rcv_wnd,
2869 &tp->window_clamp,
2870 sysctl_tcp_window_scaling,
2871 &rcv_wscale,
2872 dst_metric(dst, RTAX_INITRWND));
2873
2874 tp->rx_opt.rcv_wscale = rcv_wscale;
2875 tp->rcv_ssthresh = tp->rcv_wnd;
2876
2877 sk->sk_err = 0;
2878 sock_reset_flag(sk, SOCK_DONE);
2879 tp->snd_wnd = 0;
2880 tcp_init_wl(tp, 0);
2881 tp->snd_una = tp->write_seq;
2882 tp->snd_sml = tp->write_seq;
2883 tp->snd_up = tp->write_seq;
2884 tp->snd_nxt = tp->write_seq;
2885
2886 if (likely(!tp->repair))
2887 tp->rcv_nxt = 0;
2888 else
2889 tp->rcv_tstamp = tcp_time_stamp;
2890 tp->rcv_wup = tp->rcv_nxt;
2891 tp->copied_seq = tp->rcv_nxt;
2892
2893 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
2894 inet_csk(sk)->icsk_retransmits = 0;
2895 tcp_clear_retrans(tp);
2896}
2897
2898static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
2899{
2900 struct tcp_sock *tp = tcp_sk(sk);
2901 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
2902
2903 tcb->end_seq += skb->len;
2904 skb_header_release(skb);
2905 __tcp_add_write_queue_tail(sk, skb);
2906 sk->sk_wmem_queued += skb->truesize;
2907 sk_mem_charge(sk, skb->truesize);
2908 tp->write_seq = tcb->end_seq;
2909 tp->packets_out += tcp_skb_pcount(skb);
2910}
2911
2912/* Build and send a SYN with data and (cached) Fast Open cookie. However,
2913 * queue a data-only packet after the regular SYN, such that regular SYNs
2914 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
2915 * only the SYN sequence, the data are retransmitted in the first ACK.
2916 * If cookie is not cached or other error occurs, falls back to send a
2917 * regular SYN with Fast Open cookie request option.
2918 */
2919static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
2920{
2921 struct tcp_sock *tp = tcp_sk(sk);
2922 struct tcp_fastopen_request *fo = tp->fastopen_req;
2923 int syn_loss = 0, space, i, err = 0, iovlen = fo->data->msg_iovlen;
2924 struct sk_buff *syn_data = NULL, *data;
2925 unsigned long last_syn_loss = 0;
2926
2927 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
2928 tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
2929 &syn_loss, &last_syn_loss);
2930 /* Recurring FO SYN losses: revert to regular handshake temporarily */
2931 if (syn_loss > 1 &&
2932 time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
2933 fo->cookie.len = -1;
2934 goto fallback;
2935 }
2936
2937 if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
2938 fo->cookie.len = -1;
2939 else if (fo->cookie.len <= 0)
2940 goto fallback;
2941
2942 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
2943 * user-MSS. Reserve maximum option space for middleboxes that add
2944 * private TCP options. The cost is reduced data space in SYN :(
2945 */
2946 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
2947 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
2948 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
2949 MAX_TCP_OPTION_SPACE;
2950
2951 space = min_t(size_t, space, fo->size);
2952
2953 /* limit to order-0 allocations */
2954 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
2955
2956 syn_data = skb_copy_expand(syn, MAX_TCP_HEADER, space,
2957 sk->sk_allocation);
2958 if (syn_data == NULL)
2959 goto fallback;
2960
2961 for (i = 0; i < iovlen && syn_data->len < space; ++i) {
2962 struct iovec *iov = &fo->data->msg_iov[i];
2963 unsigned char __user *from = iov->iov_base;
2964 int len = iov->iov_len;
2965
2966 if (syn_data->len + len > space)
2967 len = space - syn_data->len;
2968 else if (i + 1 == iovlen)
2969 /* No more data pending in inet_wait_for_connect() */
2970 fo->data = NULL;
2971
2972 if (skb_add_data(syn_data, from, len))
2973 goto fallback;
2974 }
2975
2976 /* Queue a data-only packet after the regular SYN for retransmission */
2977 data = pskb_copy(syn_data, sk->sk_allocation);
2978 if (data == NULL)
2979 goto fallback;
2980 TCP_SKB_CB(data)->seq++;
2981 TCP_SKB_CB(data)->tcp_flags &= ~TCPHDR_SYN;
2982 TCP_SKB_CB(data)->tcp_flags = (TCPHDR_ACK|TCPHDR_PSH);
2983 tcp_connect_queue_skb(sk, data);
2984 fo->copied = data->len;
2985
2986 /* syn_data is about to be sent, we need to take current time stamps
2987 * for the packets that are in write queue : SYN packet and DATA
2988 */
2989 skb_mstamp_get(&syn->skb_mstamp);
2990 data->skb_mstamp = syn->skb_mstamp;
2991
2992 if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {
2993 tp->syn_data = (fo->copied > 0);
2994 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
2995 goto done;
2996 }
2997 syn_data = NULL;
2998
2999fallback:
3000 /* Send a regular SYN with Fast Open cookie request option */
3001 if (fo->cookie.len > 0)
3002 fo->cookie.len = 0;
3003 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3004 if (err)
3005 tp->syn_fastopen = 0;
3006 kfree_skb(syn_data);
3007done:
3008 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3009 return err;
3010}
3011
3012/* Build a SYN and send it off. */
3013int tcp_connect(struct sock *sk)
3014{
3015 struct tcp_sock *tp = tcp_sk(sk);
3016 struct sk_buff *buff;
3017 int err;
3018
3019 tcp_connect_init(sk);
3020
3021 if (unlikely(tp->repair)) {
3022 tcp_finish_connect(sk, NULL);
3023 return 0;
3024 }
3025
3026 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
3027 if (unlikely(buff == NULL))
3028 return -ENOBUFS;
3029
3030 /* Reserve space for headers. */
3031 skb_reserve(buff, MAX_TCP_HEADER);
3032
3033 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3034 tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp;
3035 tcp_connect_queue_skb(sk, buff);
3036 TCP_ECN_send_syn(sk, buff);
3037
3038 /* Send off SYN; include data in Fast Open. */
3039 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3040 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3041 if (err == -ECONNREFUSED)
3042 return err;
3043
3044 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3045 * in order to make this packet get counted in tcpOutSegs.
3046 */
3047 tp->snd_nxt = tp->write_seq;
3048 tp->pushed_seq = tp->write_seq;
3049 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3050
3051 /* Timer for repeating the SYN until an answer. */
3052 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3053 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3054 return 0;
3055}
3056EXPORT_SYMBOL(tcp_connect);
3057
3058/* Send out a delayed ack, the caller does the policy checking
3059 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3060 * for details.
3061 */
3062void tcp_send_delayed_ack(struct sock *sk)
3063{
3064 struct inet_connection_sock *icsk = inet_csk(sk);
3065 int ato = icsk->icsk_ack.ato;
3066 unsigned long timeout;
3067
3068 if (ato > TCP_DELACK_MIN) {
3069 const struct tcp_sock *tp = tcp_sk(sk);
3070 int max_ato = HZ / 2;
3071
3072 if (icsk->icsk_ack.pingpong ||
3073 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3074 max_ato = TCP_DELACK_MAX;
3075
3076 /* Slow path, intersegment interval is "high". */
3077
3078 /* If some rtt estimate is known, use it to bound delayed ack.
3079 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3080 * directly.
3081 */
3082 if (tp->srtt_us) {
3083 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3084 TCP_DELACK_MIN);
3085
3086 if (rtt < max_ato)
3087 max_ato = rtt;
3088 }
3089
3090 ato = min(ato, max_ato);
3091 }
3092
3093 /* Stay within the limit we were given */
3094 timeout = jiffies + ato;
3095
3096 /* Use new timeout only if there wasn't a older one earlier. */
3097 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3098 /* If delack timer was blocked or is about to expire,
3099 * send ACK now.
3100 */
3101 if (icsk->icsk_ack.blocked ||
3102 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3103 tcp_send_ack(sk);
3104 return;
3105 }
3106
3107 if (!time_before(timeout, icsk->icsk_ack.timeout))
3108 timeout = icsk->icsk_ack.timeout;
3109 }
3110 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3111 icsk->icsk_ack.timeout = timeout;
3112 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3113}
3114
3115/* This routine sends an ack and also updates the window. */
3116void tcp_send_ack(struct sock *sk)
3117{
3118 struct sk_buff *buff;
3119
3120 /* If we have been reset, we may not send again. */
3121 if (sk->sk_state == TCP_CLOSE)
3122 return;
3123
3124 /* We are not putting this on the write queue, so
3125 * tcp_transmit_skb() will set the ownership to this
3126 * sock.
3127 */
3128 buff = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3129 if (buff == NULL) {
3130 inet_csk_schedule_ack(sk);
3131 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
3132 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
3133 TCP_DELACK_MAX, TCP_RTO_MAX);
3134 return;
3135 }
3136
3137 /* Reserve space for headers and prepare control bits. */
3138 skb_reserve(buff, MAX_TCP_HEADER);
3139 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3140
3141 /* Send it off, this clears delayed acks for us. */
3142 TCP_SKB_CB(buff)->when = tcp_time_stamp;
3143 tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC));
3144}
3145
3146/* This routine sends a packet with an out of date sequence
3147 * number. It assumes the other end will try to ack it.
3148 *
3149 * Question: what should we make while urgent mode?
3150 * 4.4BSD forces sending single byte of data. We cannot send
3151 * out of window data, because we have SND.NXT==SND.MAX...
3152 *
3153 * Current solution: to send TWO zero-length segments in urgent mode:
3154 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3155 * out-of-date with SND.UNA-1 to probe window.
3156 */
3157static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
3158{
3159 struct tcp_sock *tp = tcp_sk(sk);
3160 struct sk_buff *skb;
3161
3162 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3163 skb = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3164 if (skb == NULL)
3165 return -1;
3166
3167 /* Reserve space for headers and set control bits. */
3168 skb_reserve(skb, MAX_TCP_HEADER);
3169 /* Use a previous sequence. This should cause the other
3170 * end to send an ack. Don't queue or clone SKB, just
3171 * send it.
3172 */
3173 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3174 TCP_SKB_CB(skb)->when = tcp_time_stamp;
3175 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
3176}
3177
3178void tcp_send_window_probe(struct sock *sk)
3179{
3180 if (sk->sk_state == TCP_ESTABLISHED) {
3181 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3182 tcp_xmit_probe_skb(sk, 0);
3183 }
3184}
3185
3186/* Initiate keepalive or window probe from timer. */
3187int tcp_write_wakeup(struct sock *sk)
3188{
3189 struct tcp_sock *tp = tcp_sk(sk);
3190 struct sk_buff *skb;
3191
3192 if (sk->sk_state == TCP_CLOSE)
3193 return -1;
3194
3195 if ((skb = tcp_send_head(sk)) != NULL &&
3196 before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3197 int err;
3198 unsigned int mss = tcp_current_mss(sk);
3199 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3200
3201 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
3202 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
3203
3204 /* We are probing the opening of a window
3205 * but the window size is != 0
3206 * must have been a result SWS avoidance ( sender )
3207 */
3208 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
3209 skb->len > mss) {
3210 seg_size = min(seg_size, mss);
3211 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3212 if (tcp_fragment(sk, skb, seg_size, mss))
3213 return -1;
3214 } else if (!tcp_skb_pcount(skb))
3215 tcp_set_skb_tso_segs(sk, skb, mss);
3216
3217 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3218 TCP_SKB_CB(skb)->when = tcp_time_stamp;
3219 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3220 if (!err)
3221 tcp_event_new_data_sent(sk, skb);
3222 return err;
3223 } else {
3224 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3225 tcp_xmit_probe_skb(sk, 1);
3226 return tcp_xmit_probe_skb(sk, 0);
3227 }
3228}
3229
3230/* A window probe timeout has occurred. If window is not closed send
3231 * a partial packet else a zero probe.
3232 */
3233void tcp_send_probe0(struct sock *sk)
3234{
3235 struct inet_connection_sock *icsk = inet_csk(sk);
3236 struct tcp_sock *tp = tcp_sk(sk);
3237 int err;
3238
3239 err = tcp_write_wakeup(sk);
3240
3241 if (tp->packets_out || !tcp_send_head(sk)) {
3242 /* Cancel probe timer, if it is not required. */
3243 icsk->icsk_probes_out = 0;
3244 icsk->icsk_backoff = 0;
3245 return;
3246 }
3247
3248 if (err <= 0) {
3249 if (icsk->icsk_backoff < sysctl_tcp_retries2)
3250 icsk->icsk_backoff++;
3251 icsk->icsk_probes_out++;
3252 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3253 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
3254 TCP_RTO_MAX);
3255 } else {
3256 /* If packet was not sent due to local congestion,
3257 * do not backoff and do not remember icsk_probes_out.
3258 * Let local senders to fight for local resources.
3259 *
3260 * Use accumulated backoff yet.
3261 */
3262 if (!icsk->icsk_probes_out)
3263 icsk->icsk_probes_out = 1;
3264 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3265 min(icsk->icsk_rto << icsk->icsk_backoff,
3266 TCP_RESOURCE_PROBE_INTERVAL),
3267 TCP_RTO_MAX);
3268 }
3269}
1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Authors: Ross Biro
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
19 */
20
21/*
22 * Changes: Pedro Roque : Retransmit queue handled by TCP.
23 * : Fragmentation on mtu decrease
24 * : Segment collapse on retransmit
25 * : AF independence
26 *
27 * Linus Torvalds : send_delayed_ack
28 * David S. Miller : Charge memory using the right skb
29 * during syn/ack processing.
30 * David S. Miller : Output engine completely rewritten.
31 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
32 * Cacophonix Gaul : draft-minshall-nagle-01
33 * J Hadi Salim : ECN support
34 *
35 */
36
37#define pr_fmt(fmt) "TCP: " fmt
38
39#include <net/tcp.h>
40
41#include <linux/compiler.h>
42#include <linux/gfp.h>
43#include <linux/module.h>
44#include <linux/static_key.h>
45
46#include <trace/events/tcp.h>
47
48static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
49 int push_one, gfp_t gfp);
50
51/* Account for new data that has been sent to the network. */
52static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
53{
54 struct inet_connection_sock *icsk = inet_csk(sk);
55 struct tcp_sock *tp = tcp_sk(sk);
56 unsigned int prior_packets = tp->packets_out;
57
58 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
59
60 __skb_unlink(skb, &sk->sk_write_queue);
61 tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
62
63 tp->packets_out += tcp_skb_pcount(skb);
64 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
65 tcp_rearm_rto(sk);
66
67 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
68 tcp_skb_pcount(skb));
69}
70
71/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
72 * window scaling factor due to loss of precision.
73 * If window has been shrunk, what should we make? It is not clear at all.
74 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
75 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
76 * invalid. OK, let's make this for now:
77 */
78static inline __u32 tcp_acceptable_seq(const struct sock *sk)
79{
80 const struct tcp_sock *tp = tcp_sk(sk);
81
82 if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
83 (tp->rx_opt.wscale_ok &&
84 ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
85 return tp->snd_nxt;
86 else
87 return tcp_wnd_end(tp);
88}
89
90/* Calculate mss to advertise in SYN segment.
91 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
92 *
93 * 1. It is independent of path mtu.
94 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
95 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
96 * attached devices, because some buggy hosts are confused by
97 * large MSS.
98 * 4. We do not make 3, we advertise MSS, calculated from first
99 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
100 * This may be overridden via information stored in routing table.
101 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
102 * probably even Jumbo".
103 */
104static __u16 tcp_advertise_mss(struct sock *sk)
105{
106 struct tcp_sock *tp = tcp_sk(sk);
107 const struct dst_entry *dst = __sk_dst_get(sk);
108 int mss = tp->advmss;
109
110 if (dst) {
111 unsigned int metric = dst_metric_advmss(dst);
112
113 if (metric < mss) {
114 mss = metric;
115 tp->advmss = mss;
116 }
117 }
118
119 return (__u16)mss;
120}
121
122/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
123 * This is the first part of cwnd validation mechanism.
124 */
125void tcp_cwnd_restart(struct sock *sk, s32 delta)
126{
127 struct tcp_sock *tp = tcp_sk(sk);
128 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
129 u32 cwnd = tp->snd_cwnd;
130
131 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
132
133 tp->snd_ssthresh = tcp_current_ssthresh(sk);
134 restart_cwnd = min(restart_cwnd, cwnd);
135
136 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
137 cwnd >>= 1;
138 tp->snd_cwnd = max(cwnd, restart_cwnd);
139 tp->snd_cwnd_stamp = tcp_jiffies32;
140 tp->snd_cwnd_used = 0;
141}
142
143/* Congestion state accounting after a packet has been sent. */
144static void tcp_event_data_sent(struct tcp_sock *tp,
145 struct sock *sk)
146{
147 struct inet_connection_sock *icsk = inet_csk(sk);
148 const u32 now = tcp_jiffies32;
149
150 if (tcp_packets_in_flight(tp) == 0)
151 tcp_ca_event(sk, CA_EVENT_TX_START);
152
153 tp->lsndtime = now;
154
155 /* If it is a reply for ato after last received
156 * packet, enter pingpong mode.
157 */
158 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
159 icsk->icsk_ack.pingpong = 1;
160}
161
162/* Account for an ACK we sent. */
163static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
164{
165 tcp_dec_quickack_mode(sk, pkts);
166 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
167}
168
169
170u32 tcp_default_init_rwnd(u32 mss)
171{
172 /* Initial receive window should be twice of TCP_INIT_CWND to
173 * enable proper sending of new unsent data during fast recovery
174 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
175 * limit when mss is larger than 1460.
176 */
177 u32 init_rwnd = TCP_INIT_CWND * 2;
178
179 if (mss > 1460)
180 init_rwnd = max((1460 * init_rwnd) / mss, 2U);
181 return init_rwnd;
182}
183
184/* Determine a window scaling and initial window to offer.
185 * Based on the assumption that the given amount of space
186 * will be offered. Store the results in the tp structure.
187 * NOTE: for smooth operation initial space offering should
188 * be a multiple of mss if possible. We assume here that mss >= 1.
189 * This MUST be enforced by all callers.
190 */
191void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
192 __u32 *rcv_wnd, __u32 *window_clamp,
193 int wscale_ok, __u8 *rcv_wscale,
194 __u32 init_rcv_wnd)
195{
196 unsigned int space = (__space < 0 ? 0 : __space);
197
198 /* If no clamp set the clamp to the max possible scaled window */
199 if (*window_clamp == 0)
200 (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
201 space = min(*window_clamp, space);
202
203 /* Quantize space offering to a multiple of mss if possible. */
204 if (space > mss)
205 space = rounddown(space, mss);
206
207 /* NOTE: offering an initial window larger than 32767
208 * will break some buggy TCP stacks. If the admin tells us
209 * it is likely we could be speaking with such a buggy stack
210 * we will truncate our initial window offering to 32K-1
211 * unless the remote has sent us a window scaling option,
212 * which we interpret as a sign the remote TCP is not
213 * misinterpreting the window field as a signed quantity.
214 */
215 if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
216 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
217 else
218 (*rcv_wnd) = space;
219
220 (*rcv_wscale) = 0;
221 if (wscale_ok) {
222 /* Set window scaling on max possible window */
223 space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
224 space = max_t(u32, space, sysctl_rmem_max);
225 space = min_t(u32, space, *window_clamp);
226 while (space > U16_MAX && (*rcv_wscale) < TCP_MAX_WSCALE) {
227 space >>= 1;
228 (*rcv_wscale)++;
229 }
230 }
231
232 if (mss > (1 << *rcv_wscale)) {
233 if (!init_rcv_wnd) /* Use default unless specified otherwise */
234 init_rcv_wnd = tcp_default_init_rwnd(mss);
235 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
236 }
237
238 /* Set the clamp no higher than max representable value */
239 (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
240}
241EXPORT_SYMBOL(tcp_select_initial_window);
242
243/* Chose a new window to advertise, update state in tcp_sock for the
244 * socket, and return result with RFC1323 scaling applied. The return
245 * value can be stuffed directly into th->window for an outgoing
246 * frame.
247 */
248static u16 tcp_select_window(struct sock *sk)
249{
250 struct tcp_sock *tp = tcp_sk(sk);
251 u32 old_win = tp->rcv_wnd;
252 u32 cur_win = tcp_receive_window(tp);
253 u32 new_win = __tcp_select_window(sk);
254
255 /* Never shrink the offered window */
256 if (new_win < cur_win) {
257 /* Danger Will Robinson!
258 * Don't update rcv_wup/rcv_wnd here or else
259 * we will not be able to advertise a zero
260 * window in time. --DaveM
261 *
262 * Relax Will Robinson.
263 */
264 if (new_win == 0)
265 NET_INC_STATS(sock_net(sk),
266 LINUX_MIB_TCPWANTZEROWINDOWADV);
267 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
268 }
269 tp->rcv_wnd = new_win;
270 tp->rcv_wup = tp->rcv_nxt;
271
272 /* Make sure we do not exceed the maximum possible
273 * scaled window.
274 */
275 if (!tp->rx_opt.rcv_wscale &&
276 sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
277 new_win = min(new_win, MAX_TCP_WINDOW);
278 else
279 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
280
281 /* RFC1323 scaling applied */
282 new_win >>= tp->rx_opt.rcv_wscale;
283
284 /* If we advertise zero window, disable fast path. */
285 if (new_win == 0) {
286 tp->pred_flags = 0;
287 if (old_win)
288 NET_INC_STATS(sock_net(sk),
289 LINUX_MIB_TCPTOZEROWINDOWADV);
290 } else if (old_win == 0) {
291 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
292 }
293
294 return new_win;
295}
296
297/* Packet ECN state for a SYN-ACK */
298static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
299{
300 const struct tcp_sock *tp = tcp_sk(sk);
301
302 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
303 if (!(tp->ecn_flags & TCP_ECN_OK))
304 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
305 else if (tcp_ca_needs_ecn(sk) ||
306 tcp_bpf_ca_needs_ecn(sk))
307 INET_ECN_xmit(sk);
308}
309
310/* Packet ECN state for a SYN. */
311static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
312{
313 struct tcp_sock *tp = tcp_sk(sk);
314 bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
315 bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
316 tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
317
318 if (!use_ecn) {
319 const struct dst_entry *dst = __sk_dst_get(sk);
320
321 if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
322 use_ecn = true;
323 }
324
325 tp->ecn_flags = 0;
326
327 if (use_ecn) {
328 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
329 tp->ecn_flags = TCP_ECN_OK;
330 if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
331 INET_ECN_xmit(sk);
332 }
333}
334
335static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
336{
337 if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
338 /* tp->ecn_flags are cleared at a later point in time when
339 * SYN ACK is ultimatively being received.
340 */
341 TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
342}
343
344static void
345tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
346{
347 if (inet_rsk(req)->ecn_ok)
348 th->ece = 1;
349}
350
351/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
352 * be sent.
353 */
354static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
355 struct tcphdr *th, int tcp_header_len)
356{
357 struct tcp_sock *tp = tcp_sk(sk);
358
359 if (tp->ecn_flags & TCP_ECN_OK) {
360 /* Not-retransmitted data segment: set ECT and inject CWR. */
361 if (skb->len != tcp_header_len &&
362 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
363 INET_ECN_xmit(sk);
364 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
365 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
366 th->cwr = 1;
367 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
368 }
369 } else if (!tcp_ca_needs_ecn(sk)) {
370 /* ACK or retransmitted segment: clear ECT|CE */
371 INET_ECN_dontxmit(sk);
372 }
373 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
374 th->ece = 1;
375 }
376}
377
378/* Constructs common control bits of non-data skb. If SYN/FIN is present,
379 * auto increment end seqno.
380 */
381static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
382{
383 skb->ip_summed = CHECKSUM_PARTIAL;
384
385 TCP_SKB_CB(skb)->tcp_flags = flags;
386 TCP_SKB_CB(skb)->sacked = 0;
387
388 tcp_skb_pcount_set(skb, 1);
389
390 TCP_SKB_CB(skb)->seq = seq;
391 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
392 seq++;
393 TCP_SKB_CB(skb)->end_seq = seq;
394}
395
396static inline bool tcp_urg_mode(const struct tcp_sock *tp)
397{
398 return tp->snd_una != tp->snd_up;
399}
400
401#define OPTION_SACK_ADVERTISE (1 << 0)
402#define OPTION_TS (1 << 1)
403#define OPTION_MD5 (1 << 2)
404#define OPTION_WSCALE (1 << 3)
405#define OPTION_FAST_OPEN_COOKIE (1 << 8)
406#define OPTION_SMC (1 << 9)
407
408static void smc_options_write(__be32 *ptr, u16 *options)
409{
410#if IS_ENABLED(CONFIG_SMC)
411 if (static_branch_unlikely(&tcp_have_smc)) {
412 if (unlikely(OPTION_SMC & *options)) {
413 *ptr++ = htonl((TCPOPT_NOP << 24) |
414 (TCPOPT_NOP << 16) |
415 (TCPOPT_EXP << 8) |
416 (TCPOLEN_EXP_SMC_BASE));
417 *ptr++ = htonl(TCPOPT_SMC_MAGIC);
418 }
419 }
420#endif
421}
422
423struct tcp_out_options {
424 u16 options; /* bit field of OPTION_* */
425 u16 mss; /* 0 to disable */
426 u8 ws; /* window scale, 0 to disable */
427 u8 num_sack_blocks; /* number of SACK blocks to include */
428 u8 hash_size; /* bytes in hash_location */
429 __u8 *hash_location; /* temporary pointer, overloaded */
430 __u32 tsval, tsecr; /* need to include OPTION_TS */
431 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
432};
433
434/* Write previously computed TCP options to the packet.
435 *
436 * Beware: Something in the Internet is very sensitive to the ordering of
437 * TCP options, we learned this through the hard way, so be careful here.
438 * Luckily we can at least blame others for their non-compliance but from
439 * inter-operability perspective it seems that we're somewhat stuck with
440 * the ordering which we have been using if we want to keep working with
441 * those broken things (not that it currently hurts anybody as there isn't
442 * particular reason why the ordering would need to be changed).
443 *
444 * At least SACK_PERM as the first option is known to lead to a disaster
445 * (but it may well be that other scenarios fail similarly).
446 */
447static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
448 struct tcp_out_options *opts)
449{
450 u16 options = opts->options; /* mungable copy */
451
452 if (unlikely(OPTION_MD5 & options)) {
453 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
454 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
455 /* overload cookie hash location */
456 opts->hash_location = (__u8 *)ptr;
457 ptr += 4;
458 }
459
460 if (unlikely(opts->mss)) {
461 *ptr++ = htonl((TCPOPT_MSS << 24) |
462 (TCPOLEN_MSS << 16) |
463 opts->mss);
464 }
465
466 if (likely(OPTION_TS & options)) {
467 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
468 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
469 (TCPOLEN_SACK_PERM << 16) |
470 (TCPOPT_TIMESTAMP << 8) |
471 TCPOLEN_TIMESTAMP);
472 options &= ~OPTION_SACK_ADVERTISE;
473 } else {
474 *ptr++ = htonl((TCPOPT_NOP << 24) |
475 (TCPOPT_NOP << 16) |
476 (TCPOPT_TIMESTAMP << 8) |
477 TCPOLEN_TIMESTAMP);
478 }
479 *ptr++ = htonl(opts->tsval);
480 *ptr++ = htonl(opts->tsecr);
481 }
482
483 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
484 *ptr++ = htonl((TCPOPT_NOP << 24) |
485 (TCPOPT_NOP << 16) |
486 (TCPOPT_SACK_PERM << 8) |
487 TCPOLEN_SACK_PERM);
488 }
489
490 if (unlikely(OPTION_WSCALE & options)) {
491 *ptr++ = htonl((TCPOPT_NOP << 24) |
492 (TCPOPT_WINDOW << 16) |
493 (TCPOLEN_WINDOW << 8) |
494 opts->ws);
495 }
496
497 if (unlikely(opts->num_sack_blocks)) {
498 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
499 tp->duplicate_sack : tp->selective_acks;
500 int this_sack;
501
502 *ptr++ = htonl((TCPOPT_NOP << 24) |
503 (TCPOPT_NOP << 16) |
504 (TCPOPT_SACK << 8) |
505 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
506 TCPOLEN_SACK_PERBLOCK)));
507
508 for (this_sack = 0; this_sack < opts->num_sack_blocks;
509 ++this_sack) {
510 *ptr++ = htonl(sp[this_sack].start_seq);
511 *ptr++ = htonl(sp[this_sack].end_seq);
512 }
513
514 tp->rx_opt.dsack = 0;
515 }
516
517 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
518 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
519 u8 *p = (u8 *)ptr;
520 u32 len; /* Fast Open option length */
521
522 if (foc->exp) {
523 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
524 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
525 TCPOPT_FASTOPEN_MAGIC);
526 p += TCPOLEN_EXP_FASTOPEN_BASE;
527 } else {
528 len = TCPOLEN_FASTOPEN_BASE + foc->len;
529 *p++ = TCPOPT_FASTOPEN;
530 *p++ = len;
531 }
532
533 memcpy(p, foc->val, foc->len);
534 if ((len & 3) == 2) {
535 p[foc->len] = TCPOPT_NOP;
536 p[foc->len + 1] = TCPOPT_NOP;
537 }
538 ptr += (len + 3) >> 2;
539 }
540
541 smc_options_write(ptr, &options);
542}
543
544static void smc_set_option(const struct tcp_sock *tp,
545 struct tcp_out_options *opts,
546 unsigned int *remaining)
547{
548#if IS_ENABLED(CONFIG_SMC)
549 if (static_branch_unlikely(&tcp_have_smc)) {
550 if (tp->syn_smc) {
551 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
552 opts->options |= OPTION_SMC;
553 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
554 }
555 }
556 }
557#endif
558}
559
560static void smc_set_option_cond(const struct tcp_sock *tp,
561 const struct inet_request_sock *ireq,
562 struct tcp_out_options *opts,
563 unsigned int *remaining)
564{
565#if IS_ENABLED(CONFIG_SMC)
566 if (static_branch_unlikely(&tcp_have_smc)) {
567 if (tp->syn_smc && ireq->smc_ok) {
568 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
569 opts->options |= OPTION_SMC;
570 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
571 }
572 }
573 }
574#endif
575}
576
577/* Compute TCP options for SYN packets. This is not the final
578 * network wire format yet.
579 */
580static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
581 struct tcp_out_options *opts,
582 struct tcp_md5sig_key **md5)
583{
584 struct tcp_sock *tp = tcp_sk(sk);
585 unsigned int remaining = MAX_TCP_OPTION_SPACE;
586 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
587
588#ifdef CONFIG_TCP_MD5SIG
589 *md5 = tp->af_specific->md5_lookup(sk, sk);
590 if (*md5) {
591 opts->options |= OPTION_MD5;
592 remaining -= TCPOLEN_MD5SIG_ALIGNED;
593 }
594#else
595 *md5 = NULL;
596#endif
597
598 /* We always get an MSS option. The option bytes which will be seen in
599 * normal data packets should timestamps be used, must be in the MSS
600 * advertised. But we subtract them from tp->mss_cache so that
601 * calculations in tcp_sendmsg are simpler etc. So account for this
602 * fact here if necessary. If we don't do this correctly, as a
603 * receiver we won't recognize data packets as being full sized when we
604 * should, and thus we won't abide by the delayed ACK rules correctly.
605 * SACKs don't matter, we never delay an ACK when we have any of those
606 * going out. */
607 opts->mss = tcp_advertise_mss(sk);
608 remaining -= TCPOLEN_MSS_ALIGNED;
609
610 if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) {
611 opts->options |= OPTION_TS;
612 opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
613 opts->tsecr = tp->rx_opt.ts_recent;
614 remaining -= TCPOLEN_TSTAMP_ALIGNED;
615 }
616 if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) {
617 opts->ws = tp->rx_opt.rcv_wscale;
618 opts->options |= OPTION_WSCALE;
619 remaining -= TCPOLEN_WSCALE_ALIGNED;
620 }
621 if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) {
622 opts->options |= OPTION_SACK_ADVERTISE;
623 if (unlikely(!(OPTION_TS & opts->options)))
624 remaining -= TCPOLEN_SACKPERM_ALIGNED;
625 }
626
627 if (fastopen && fastopen->cookie.len >= 0) {
628 u32 need = fastopen->cookie.len;
629
630 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
631 TCPOLEN_FASTOPEN_BASE;
632 need = (need + 3) & ~3U; /* Align to 32 bits */
633 if (remaining >= need) {
634 opts->options |= OPTION_FAST_OPEN_COOKIE;
635 opts->fastopen_cookie = &fastopen->cookie;
636 remaining -= need;
637 tp->syn_fastopen = 1;
638 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
639 }
640 }
641
642 smc_set_option(tp, opts, &remaining);
643
644 return MAX_TCP_OPTION_SPACE - remaining;
645}
646
647/* Set up TCP options for SYN-ACKs. */
648static unsigned int tcp_synack_options(const struct sock *sk,
649 struct request_sock *req,
650 unsigned int mss, struct sk_buff *skb,
651 struct tcp_out_options *opts,
652 const struct tcp_md5sig_key *md5,
653 struct tcp_fastopen_cookie *foc)
654{
655 struct inet_request_sock *ireq = inet_rsk(req);
656 unsigned int remaining = MAX_TCP_OPTION_SPACE;
657
658#ifdef CONFIG_TCP_MD5SIG
659 if (md5) {
660 opts->options |= OPTION_MD5;
661 remaining -= TCPOLEN_MD5SIG_ALIGNED;
662
663 /* We can't fit any SACK blocks in a packet with MD5 + TS
664 * options. There was discussion about disabling SACK
665 * rather than TS in order to fit in better with old,
666 * buggy kernels, but that was deemed to be unnecessary.
667 */
668 ireq->tstamp_ok &= !ireq->sack_ok;
669 }
670#endif
671
672 /* We always send an MSS option. */
673 opts->mss = mss;
674 remaining -= TCPOLEN_MSS_ALIGNED;
675
676 if (likely(ireq->wscale_ok)) {
677 opts->ws = ireq->rcv_wscale;
678 opts->options |= OPTION_WSCALE;
679 remaining -= TCPOLEN_WSCALE_ALIGNED;
680 }
681 if (likely(ireq->tstamp_ok)) {
682 opts->options |= OPTION_TS;
683 opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
684 opts->tsecr = req->ts_recent;
685 remaining -= TCPOLEN_TSTAMP_ALIGNED;
686 }
687 if (likely(ireq->sack_ok)) {
688 opts->options |= OPTION_SACK_ADVERTISE;
689 if (unlikely(!ireq->tstamp_ok))
690 remaining -= TCPOLEN_SACKPERM_ALIGNED;
691 }
692 if (foc != NULL && foc->len >= 0) {
693 u32 need = foc->len;
694
695 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
696 TCPOLEN_FASTOPEN_BASE;
697 need = (need + 3) & ~3U; /* Align to 32 bits */
698 if (remaining >= need) {
699 opts->options |= OPTION_FAST_OPEN_COOKIE;
700 opts->fastopen_cookie = foc;
701 remaining -= need;
702 }
703 }
704
705 smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
706
707 return MAX_TCP_OPTION_SPACE - remaining;
708}
709
710/* Compute TCP options for ESTABLISHED sockets. This is not the
711 * final wire format yet.
712 */
713static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
714 struct tcp_out_options *opts,
715 struct tcp_md5sig_key **md5)
716{
717 struct tcp_sock *tp = tcp_sk(sk);
718 unsigned int size = 0;
719 unsigned int eff_sacks;
720
721 opts->options = 0;
722
723#ifdef CONFIG_TCP_MD5SIG
724 *md5 = tp->af_specific->md5_lookup(sk, sk);
725 if (unlikely(*md5)) {
726 opts->options |= OPTION_MD5;
727 size += TCPOLEN_MD5SIG_ALIGNED;
728 }
729#else
730 *md5 = NULL;
731#endif
732
733 if (likely(tp->rx_opt.tstamp_ok)) {
734 opts->options |= OPTION_TS;
735 opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
736 opts->tsecr = tp->rx_opt.ts_recent;
737 size += TCPOLEN_TSTAMP_ALIGNED;
738 }
739
740 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
741 if (unlikely(eff_sacks)) {
742 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
743 opts->num_sack_blocks =
744 min_t(unsigned int, eff_sacks,
745 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
746 TCPOLEN_SACK_PERBLOCK);
747 size += TCPOLEN_SACK_BASE_ALIGNED +
748 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
749 }
750
751 return size;
752}
753
754
755/* TCP SMALL QUEUES (TSQ)
756 *
757 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
758 * to reduce RTT and bufferbloat.
759 * We do this using a special skb destructor (tcp_wfree).
760 *
761 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
762 * needs to be reallocated in a driver.
763 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
764 *
765 * Since transmit from skb destructor is forbidden, we use a tasklet
766 * to process all sockets that eventually need to send more skbs.
767 * We use one tasklet per cpu, with its own queue of sockets.
768 */
769struct tsq_tasklet {
770 struct tasklet_struct tasklet;
771 struct list_head head; /* queue of tcp sockets */
772};
773static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
774
775static void tcp_tsq_handler(struct sock *sk)
776{
777 if ((1 << sk->sk_state) &
778 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
779 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
780 struct tcp_sock *tp = tcp_sk(sk);
781
782 if (tp->lost_out > tp->retrans_out &&
783 tp->snd_cwnd > tcp_packets_in_flight(tp)) {
784 tcp_mstamp_refresh(tp);
785 tcp_xmit_retransmit_queue(sk);
786 }
787
788 tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
789 0, GFP_ATOMIC);
790 }
791}
792/*
793 * One tasklet per cpu tries to send more skbs.
794 * We run in tasklet context but need to disable irqs when
795 * transferring tsq->head because tcp_wfree() might
796 * interrupt us (non NAPI drivers)
797 */
798static void tcp_tasklet_func(unsigned long data)
799{
800 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
801 LIST_HEAD(list);
802 unsigned long flags;
803 struct list_head *q, *n;
804 struct tcp_sock *tp;
805 struct sock *sk;
806
807 local_irq_save(flags);
808 list_splice_init(&tsq->head, &list);
809 local_irq_restore(flags);
810
811 list_for_each_safe(q, n, &list) {
812 tp = list_entry(q, struct tcp_sock, tsq_node);
813 list_del(&tp->tsq_node);
814
815 sk = (struct sock *)tp;
816 smp_mb__before_atomic();
817 clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
818
819 if (!sk->sk_lock.owned &&
820 test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags)) {
821 bh_lock_sock(sk);
822 if (!sock_owned_by_user(sk)) {
823 clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
824 tcp_tsq_handler(sk);
825 }
826 bh_unlock_sock(sk);
827 }
828
829 sk_free(sk);
830 }
831}
832
833#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
834 TCPF_WRITE_TIMER_DEFERRED | \
835 TCPF_DELACK_TIMER_DEFERRED | \
836 TCPF_MTU_REDUCED_DEFERRED)
837/**
838 * tcp_release_cb - tcp release_sock() callback
839 * @sk: socket
840 *
841 * called from release_sock() to perform protocol dependent
842 * actions before socket release.
843 */
844void tcp_release_cb(struct sock *sk)
845{
846 unsigned long flags, nflags;
847
848 /* perform an atomic operation only if at least one flag is set */
849 do {
850 flags = sk->sk_tsq_flags;
851 if (!(flags & TCP_DEFERRED_ALL))
852 return;
853 nflags = flags & ~TCP_DEFERRED_ALL;
854 } while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
855
856 if (flags & TCPF_TSQ_DEFERRED)
857 tcp_tsq_handler(sk);
858
859 /* Here begins the tricky part :
860 * We are called from release_sock() with :
861 * 1) BH disabled
862 * 2) sk_lock.slock spinlock held
863 * 3) socket owned by us (sk->sk_lock.owned == 1)
864 *
865 * But following code is meant to be called from BH handlers,
866 * so we should keep BH disabled, but early release socket ownership
867 */
868 sock_release_ownership(sk);
869
870 if (flags & TCPF_WRITE_TIMER_DEFERRED) {
871 tcp_write_timer_handler(sk);
872 __sock_put(sk);
873 }
874 if (flags & TCPF_DELACK_TIMER_DEFERRED) {
875 tcp_delack_timer_handler(sk);
876 __sock_put(sk);
877 }
878 if (flags & TCPF_MTU_REDUCED_DEFERRED) {
879 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
880 __sock_put(sk);
881 }
882}
883EXPORT_SYMBOL(tcp_release_cb);
884
885void __init tcp_tasklet_init(void)
886{
887 int i;
888
889 for_each_possible_cpu(i) {
890 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
891
892 INIT_LIST_HEAD(&tsq->head);
893 tasklet_init(&tsq->tasklet,
894 tcp_tasklet_func,
895 (unsigned long)tsq);
896 }
897}
898
899/*
900 * Write buffer destructor automatically called from kfree_skb.
901 * We can't xmit new skbs from this context, as we might already
902 * hold qdisc lock.
903 */
904void tcp_wfree(struct sk_buff *skb)
905{
906 struct sock *sk = skb->sk;
907 struct tcp_sock *tp = tcp_sk(sk);
908 unsigned long flags, nval, oval;
909
910 /* Keep one reference on sk_wmem_alloc.
911 * Will be released by sk_free() from here or tcp_tasklet_func()
912 */
913 WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
914
915 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
916 * Wait until our queues (qdisc + devices) are drained.
917 * This gives :
918 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
919 * - chance for incoming ACK (processed by another cpu maybe)
920 * to migrate this flow (skb->ooo_okay will be eventually set)
921 */
922 if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
923 goto out;
924
925 for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
926 struct tsq_tasklet *tsq;
927 bool empty;
928
929 if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
930 goto out;
931
932 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED | TCPF_TSQ_DEFERRED;
933 nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
934 if (nval != oval)
935 continue;
936
937 /* queue this socket to tasklet queue */
938 local_irq_save(flags);
939 tsq = this_cpu_ptr(&tsq_tasklet);
940 empty = list_empty(&tsq->head);
941 list_add(&tp->tsq_node, &tsq->head);
942 if (empty)
943 tasklet_schedule(&tsq->tasklet);
944 local_irq_restore(flags);
945 return;
946 }
947out:
948 sk_free(sk);
949}
950
951/* Note: Called under hard irq.
952 * We can not call TCP stack right away.
953 */
954enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
955{
956 struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
957 struct sock *sk = (struct sock *)tp;
958 unsigned long nval, oval;
959
960 for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
961 struct tsq_tasklet *tsq;
962 bool empty;
963
964 if (oval & TSQF_QUEUED)
965 break;
966
967 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED | TCPF_TSQ_DEFERRED;
968 nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
969 if (nval != oval)
970 continue;
971
972 if (!refcount_inc_not_zero(&sk->sk_wmem_alloc))
973 break;
974 /* queue this socket to tasklet queue */
975 tsq = this_cpu_ptr(&tsq_tasklet);
976 empty = list_empty(&tsq->head);
977 list_add(&tp->tsq_node, &tsq->head);
978 if (empty)
979 tasklet_schedule(&tsq->tasklet);
980 break;
981 }
982 return HRTIMER_NORESTART;
983}
984
985/* BBR congestion control needs pacing.
986 * Same remark for SO_MAX_PACING_RATE.
987 * sch_fq packet scheduler is efficiently handling pacing,
988 * but is not always installed/used.
989 * Return true if TCP stack should pace packets itself.
990 */
991static bool tcp_needs_internal_pacing(const struct sock *sk)
992{
993 return smp_load_acquire(&sk->sk_pacing_status) == SK_PACING_NEEDED;
994}
995
996static void tcp_internal_pacing(struct sock *sk, const struct sk_buff *skb)
997{
998 u64 len_ns;
999 u32 rate;
1000
1001 if (!tcp_needs_internal_pacing(sk))
1002 return;
1003 rate = sk->sk_pacing_rate;
1004 if (!rate || rate == ~0U)
1005 return;
1006
1007 /* Should account for header sizes as sch_fq does,
1008 * but lets make things simple.
1009 */
1010 len_ns = (u64)skb->len * NSEC_PER_SEC;
1011 do_div(len_ns, rate);
1012 hrtimer_start(&tcp_sk(sk)->pacing_timer,
1013 ktime_add_ns(ktime_get(), len_ns),
1014 HRTIMER_MODE_ABS_PINNED);
1015}
1016
1017static void tcp_update_skb_after_send(struct tcp_sock *tp, struct sk_buff *skb)
1018{
1019 skb->skb_mstamp = tp->tcp_mstamp;
1020 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
1021}
1022
1023/* This routine actually transmits TCP packets queued in by
1024 * tcp_do_sendmsg(). This is used by both the initial
1025 * transmission and possible later retransmissions.
1026 * All SKB's seen here are completely headerless. It is our
1027 * job to build the TCP header, and pass the packet down to
1028 * IP so it can do the same plus pass the packet off to the
1029 * device.
1030 *
1031 * We are working here with either a clone of the original
1032 * SKB, or a fresh unique copy made by the retransmit engine.
1033 */
1034static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
1035 gfp_t gfp_mask)
1036{
1037 const struct inet_connection_sock *icsk = inet_csk(sk);
1038 struct inet_sock *inet;
1039 struct tcp_sock *tp;
1040 struct tcp_skb_cb *tcb;
1041 struct tcp_out_options opts;
1042 unsigned int tcp_options_size, tcp_header_size;
1043 struct sk_buff *oskb = NULL;
1044 struct tcp_md5sig_key *md5;
1045 struct tcphdr *th;
1046 int err;
1047
1048 BUG_ON(!skb || !tcp_skb_pcount(skb));
1049 tp = tcp_sk(sk);
1050
1051 if (clone_it) {
1052 TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
1053 - tp->snd_una;
1054 oskb = skb;
1055
1056 tcp_skb_tsorted_save(oskb) {
1057 if (unlikely(skb_cloned(oskb)))
1058 skb = pskb_copy(oskb, gfp_mask);
1059 else
1060 skb = skb_clone(oskb, gfp_mask);
1061 } tcp_skb_tsorted_restore(oskb);
1062
1063 if (unlikely(!skb))
1064 return -ENOBUFS;
1065 }
1066 skb->skb_mstamp = tp->tcp_mstamp;
1067
1068 inet = inet_sk(sk);
1069 tcb = TCP_SKB_CB(skb);
1070 memset(&opts, 0, sizeof(opts));
1071
1072 if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
1073 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
1074 else
1075 tcp_options_size = tcp_established_options(sk, skb, &opts,
1076 &md5);
1077 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1078
1079 /* if no packet is in qdisc/device queue, then allow XPS to select
1080 * another queue. We can be called from tcp_tsq_handler()
1081 * which holds one reference to sk_wmem_alloc.
1082 *
1083 * TODO: Ideally, in-flight pure ACK packets should not matter here.
1084 * One way to get this would be to set skb->truesize = 2 on them.
1085 */
1086 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1087
1088 /* If we had to use memory reserve to allocate this skb,
1089 * this might cause drops if packet is looped back :
1090 * Other socket might not have SOCK_MEMALLOC.
1091 * Packets not looped back do not care about pfmemalloc.
1092 */
1093 skb->pfmemalloc = 0;
1094
1095 skb_push(skb, tcp_header_size);
1096 skb_reset_transport_header(skb);
1097
1098 skb_orphan(skb);
1099 skb->sk = sk;
1100 skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1101 skb_set_hash_from_sk(skb, sk);
1102 refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1103
1104 skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);
1105
1106 /* Build TCP header and checksum it. */
1107 th = (struct tcphdr *)skb->data;
1108 th->source = inet->inet_sport;
1109 th->dest = inet->inet_dport;
1110 th->seq = htonl(tcb->seq);
1111 th->ack_seq = htonl(tp->rcv_nxt);
1112 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
1113 tcb->tcp_flags);
1114
1115 th->check = 0;
1116 th->urg_ptr = 0;
1117
1118 /* The urg_mode check is necessary during a below snd_una win probe */
1119 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
1120 if (before(tp->snd_up, tcb->seq + 0x10000)) {
1121 th->urg_ptr = htons(tp->snd_up - tcb->seq);
1122 th->urg = 1;
1123 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1124 th->urg_ptr = htons(0xFFFF);
1125 th->urg = 1;
1126 }
1127 }
1128
1129 tcp_options_write((__be32 *)(th + 1), tp, &opts);
1130 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1131 if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
1132 th->window = htons(tcp_select_window(sk));
1133 tcp_ecn_send(sk, skb, th, tcp_header_size);
1134 } else {
1135 /* RFC1323: The window in SYN & SYN/ACK segments
1136 * is never scaled.
1137 */
1138 th->window = htons(min(tp->rcv_wnd, 65535U));
1139 }
1140#ifdef CONFIG_TCP_MD5SIG
1141 /* Calculate the MD5 hash, as we have all we need now */
1142 if (md5) {
1143 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1144 tp->af_specific->calc_md5_hash(opts.hash_location,
1145 md5, sk, skb);
1146 }
1147#endif
1148
1149 icsk->icsk_af_ops->send_check(sk, skb);
1150
1151 if (likely(tcb->tcp_flags & TCPHDR_ACK))
1152 tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
1153
1154 if (skb->len != tcp_header_size) {
1155 tcp_event_data_sent(tp, sk);
1156 tp->data_segs_out += tcp_skb_pcount(skb);
1157 tcp_internal_pacing(sk, skb);
1158 }
1159
1160 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1161 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1162 tcp_skb_pcount(skb));
1163
1164 tp->segs_out += tcp_skb_pcount(skb);
1165 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1166 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1167 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1168
1169 /* Our usage of tstamp should remain private */
1170 skb->tstamp = 0;
1171
1172 /* Cleanup our debris for IP stacks */
1173 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1174 sizeof(struct inet6_skb_parm)));
1175
1176 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
1177
1178 if (unlikely(err > 0)) {
1179 tcp_enter_cwr(sk);
1180 err = net_xmit_eval(err);
1181 }
1182 if (!err && oskb) {
1183 tcp_update_skb_after_send(tp, oskb);
1184 tcp_rate_skb_sent(sk, oskb);
1185 }
1186 return err;
1187}
1188
1189/* This routine just queues the buffer for sending.
1190 *
1191 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1192 * otherwise socket can stall.
1193 */
1194static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1195{
1196 struct tcp_sock *tp = tcp_sk(sk);
1197
1198 /* Advance write_seq and place onto the write_queue. */
1199 tp->write_seq = TCP_SKB_CB(skb)->end_seq;
1200 __skb_header_release(skb);
1201 tcp_add_write_queue_tail(sk, skb);
1202 sk->sk_wmem_queued += skb->truesize;
1203 sk_mem_charge(sk, skb->truesize);
1204}
1205
1206/* Initialize TSO segments for a packet. */
1207static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1208{
1209 if (skb->len <= mss_now) {
1210 /* Avoid the costly divide in the normal
1211 * non-TSO case.
1212 */
1213 tcp_skb_pcount_set(skb, 1);
1214 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1215 } else {
1216 tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1217 TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1218 }
1219}
1220
1221/* Pcount in the middle of the write queue got changed, we need to do various
1222 * tweaks to fix counters
1223 */
1224static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1225{
1226 struct tcp_sock *tp = tcp_sk(sk);
1227
1228 tp->packets_out -= decr;
1229
1230 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1231 tp->sacked_out -= decr;
1232 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1233 tp->retrans_out -= decr;
1234 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1235 tp->lost_out -= decr;
1236
1237 /* Reno case is special. Sigh... */
1238 if (tcp_is_reno(tp) && decr > 0)
1239 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1240
1241 if (tp->lost_skb_hint &&
1242 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1243 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
1244 tp->lost_cnt_hint -= decr;
1245
1246 tcp_verify_left_out(tp);
1247}
1248
1249static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
1250{
1251 return TCP_SKB_CB(skb)->txstamp_ack ||
1252 (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
1253}
1254
1255static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1256{
1257 struct skb_shared_info *shinfo = skb_shinfo(skb);
1258
1259 if (unlikely(tcp_has_tx_tstamp(skb)) &&
1260 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1261 struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1262 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1263
1264 shinfo->tx_flags &= ~tsflags;
1265 shinfo2->tx_flags |= tsflags;
1266 swap(shinfo->tskey, shinfo2->tskey);
1267 TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
1268 TCP_SKB_CB(skb)->txstamp_ack = 0;
1269 }
1270}
1271
1272static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
1273{
1274 TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
1275 TCP_SKB_CB(skb)->eor = 0;
1276}
1277
1278/* Insert buff after skb on the write or rtx queue of sk. */
1279static void tcp_insert_write_queue_after(struct sk_buff *skb,
1280 struct sk_buff *buff,
1281 struct sock *sk,
1282 enum tcp_queue tcp_queue)
1283{
1284 if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
1285 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1286 else
1287 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
1288}
1289
1290/* Function to create two new TCP segments. Shrinks the given segment
1291 * to the specified size and appends a new segment with the rest of the
1292 * packet to the list. This won't be called frequently, I hope.
1293 * Remember, these are still headerless SKBs at this point.
1294 */
1295int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1296 struct sk_buff *skb, u32 len,
1297 unsigned int mss_now, gfp_t gfp)
1298{
1299 struct tcp_sock *tp = tcp_sk(sk);
1300 struct sk_buff *buff;
1301 int nsize, old_factor;
1302 int nlen;
1303 u8 flags;
1304
1305 if (WARN_ON(len > skb->len))
1306 return -EINVAL;
1307
1308 nsize = skb_headlen(skb) - len;
1309 if (nsize < 0)
1310 nsize = 0;
1311
1312 if (skb_unclone(skb, gfp))
1313 return -ENOMEM;
1314
1315 /* Get a new skb... force flag on. */
1316 buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1317 if (!buff)
1318 return -ENOMEM; /* We'll just try again later. */
1319
1320 sk->sk_wmem_queued += buff->truesize;
1321 sk_mem_charge(sk, buff->truesize);
1322 nlen = skb->len - len - nsize;
1323 buff->truesize += nlen;
1324 skb->truesize -= nlen;
1325
1326 /* Correct the sequence numbers. */
1327 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1328 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1329 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1330
1331 /* PSH and FIN should only be set in the second packet. */
1332 flags = TCP_SKB_CB(skb)->tcp_flags;
1333 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1334 TCP_SKB_CB(buff)->tcp_flags = flags;
1335 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1336 tcp_skb_fragment_eor(skb, buff);
1337
1338 skb_split(skb, buff, len);
1339
1340 buff->ip_summed = CHECKSUM_PARTIAL;
1341
1342 buff->tstamp = skb->tstamp;
1343 tcp_fragment_tstamp(skb, buff);
1344
1345 old_factor = tcp_skb_pcount(skb);
1346
1347 /* Fix up tso_factor for both original and new SKB. */
1348 tcp_set_skb_tso_segs(skb, mss_now);
1349 tcp_set_skb_tso_segs(buff, mss_now);
1350
1351 /* Update delivered info for the new segment */
1352 TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
1353
1354 /* If this packet has been sent out already, we must
1355 * adjust the various packet counters.
1356 */
1357 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1358 int diff = old_factor - tcp_skb_pcount(skb) -
1359 tcp_skb_pcount(buff);
1360
1361 if (diff)
1362 tcp_adjust_pcount(sk, skb, diff);
1363 }
1364
1365 /* Link BUFF into the send queue. */
1366 __skb_header_release(buff);
1367 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1368 if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
1369 list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
1370
1371 return 0;
1372}
1373
1374/* This is similar to __pskb_pull_tail(). The difference is that pulled
1375 * data is not copied, but immediately discarded.
1376 */
1377static int __pskb_trim_head(struct sk_buff *skb, int len)
1378{
1379 struct skb_shared_info *shinfo;
1380 int i, k, eat;
1381
1382 eat = min_t(int, len, skb_headlen(skb));
1383 if (eat) {
1384 __skb_pull(skb, eat);
1385 len -= eat;
1386 if (!len)
1387 return 0;
1388 }
1389 eat = len;
1390 k = 0;
1391 shinfo = skb_shinfo(skb);
1392 for (i = 0; i < shinfo->nr_frags; i++) {
1393 int size = skb_frag_size(&shinfo->frags[i]);
1394
1395 if (size <= eat) {
1396 skb_frag_unref(skb, i);
1397 eat -= size;
1398 } else {
1399 shinfo->frags[k] = shinfo->frags[i];
1400 if (eat) {
1401 shinfo->frags[k].page_offset += eat;
1402 skb_frag_size_sub(&shinfo->frags[k], eat);
1403 eat = 0;
1404 }
1405 k++;
1406 }
1407 }
1408 shinfo->nr_frags = k;
1409
1410 skb->data_len -= len;
1411 skb->len = skb->data_len;
1412 return len;
1413}
1414
1415/* Remove acked data from a packet in the transmit queue. */
1416int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1417{
1418 u32 delta_truesize;
1419
1420 if (skb_unclone(skb, GFP_ATOMIC))
1421 return -ENOMEM;
1422
1423 delta_truesize = __pskb_trim_head(skb, len);
1424
1425 TCP_SKB_CB(skb)->seq += len;
1426 skb->ip_summed = CHECKSUM_PARTIAL;
1427
1428 if (delta_truesize) {
1429 skb->truesize -= delta_truesize;
1430 sk->sk_wmem_queued -= delta_truesize;
1431 sk_mem_uncharge(sk, delta_truesize);
1432 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1433 }
1434
1435 /* Any change of skb->len requires recalculation of tso factor. */
1436 if (tcp_skb_pcount(skb) > 1)
1437 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1438
1439 return 0;
1440}
1441
1442/* Calculate MSS not accounting any TCP options. */
1443static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1444{
1445 const struct tcp_sock *tp = tcp_sk(sk);
1446 const struct inet_connection_sock *icsk = inet_csk(sk);
1447 int mss_now;
1448
1449 /* Calculate base mss without TCP options:
1450 It is MMS_S - sizeof(tcphdr) of rfc1122
1451 */
1452 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1453
1454 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1455 if (icsk->icsk_af_ops->net_frag_header_len) {
1456 const struct dst_entry *dst = __sk_dst_get(sk);
1457
1458 if (dst && dst_allfrag(dst))
1459 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1460 }
1461
1462 /* Clamp it (mss_clamp does not include tcp options) */
1463 if (mss_now > tp->rx_opt.mss_clamp)
1464 mss_now = tp->rx_opt.mss_clamp;
1465
1466 /* Now subtract optional transport overhead */
1467 mss_now -= icsk->icsk_ext_hdr_len;
1468
1469 /* Then reserve room for full set of TCP options and 8 bytes of data */
1470 if (mss_now < 48)
1471 mss_now = 48;
1472 return mss_now;
1473}
1474
1475/* Calculate MSS. Not accounting for SACKs here. */
1476int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1477{
1478 /* Subtract TCP options size, not including SACKs */
1479 return __tcp_mtu_to_mss(sk, pmtu) -
1480 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1481}
1482
1483/* Inverse of above */
1484int tcp_mss_to_mtu(struct sock *sk, int mss)
1485{
1486 const struct tcp_sock *tp = tcp_sk(sk);
1487 const struct inet_connection_sock *icsk = inet_csk(sk);
1488 int mtu;
1489
1490 mtu = mss +
1491 tp->tcp_header_len +
1492 icsk->icsk_ext_hdr_len +
1493 icsk->icsk_af_ops->net_header_len;
1494
1495 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1496 if (icsk->icsk_af_ops->net_frag_header_len) {
1497 const struct dst_entry *dst = __sk_dst_get(sk);
1498
1499 if (dst && dst_allfrag(dst))
1500 mtu += icsk->icsk_af_ops->net_frag_header_len;
1501 }
1502 return mtu;
1503}
1504EXPORT_SYMBOL(tcp_mss_to_mtu);
1505
1506/* MTU probing init per socket */
1507void tcp_mtup_init(struct sock *sk)
1508{
1509 struct tcp_sock *tp = tcp_sk(sk);
1510 struct inet_connection_sock *icsk = inet_csk(sk);
1511 struct net *net = sock_net(sk);
1512
1513 icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
1514 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1515 icsk->icsk_af_ops->net_header_len;
1516 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
1517 icsk->icsk_mtup.probe_size = 0;
1518 if (icsk->icsk_mtup.enabled)
1519 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1520}
1521EXPORT_SYMBOL(tcp_mtup_init);
1522
1523/* This function synchronize snd mss to current pmtu/exthdr set.
1524
1525 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1526 for TCP options, but includes only bare TCP header.
1527
1528 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1529 It is minimum of user_mss and mss received with SYN.
1530 It also does not include TCP options.
1531
1532 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1533
1534 tp->mss_cache is current effective sending mss, including
1535 all tcp options except for SACKs. It is evaluated,
1536 taking into account current pmtu, but never exceeds
1537 tp->rx_opt.mss_clamp.
1538
1539 NOTE1. rfc1122 clearly states that advertised MSS
1540 DOES NOT include either tcp or ip options.
1541
1542 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1543 are READ ONLY outside this function. --ANK (980731)
1544 */
1545unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1546{
1547 struct tcp_sock *tp = tcp_sk(sk);
1548 struct inet_connection_sock *icsk = inet_csk(sk);
1549 int mss_now;
1550
1551 if (icsk->icsk_mtup.search_high > pmtu)
1552 icsk->icsk_mtup.search_high = pmtu;
1553
1554 mss_now = tcp_mtu_to_mss(sk, pmtu);
1555 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1556
1557 /* And store cached results */
1558 icsk->icsk_pmtu_cookie = pmtu;
1559 if (icsk->icsk_mtup.enabled)
1560 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1561 tp->mss_cache = mss_now;
1562
1563 return mss_now;
1564}
1565EXPORT_SYMBOL(tcp_sync_mss);
1566
1567/* Compute the current effective MSS, taking SACKs and IP options,
1568 * and even PMTU discovery events into account.
1569 */
1570unsigned int tcp_current_mss(struct sock *sk)
1571{
1572 const struct tcp_sock *tp = tcp_sk(sk);
1573 const struct dst_entry *dst = __sk_dst_get(sk);
1574 u32 mss_now;
1575 unsigned int header_len;
1576 struct tcp_out_options opts;
1577 struct tcp_md5sig_key *md5;
1578
1579 mss_now = tp->mss_cache;
1580
1581 if (dst) {
1582 u32 mtu = dst_mtu(dst);
1583 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1584 mss_now = tcp_sync_mss(sk, mtu);
1585 }
1586
1587 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1588 sizeof(struct tcphdr);
1589 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1590 * some common options. If this is an odd packet (because we have SACK
1591 * blocks etc) then our calculated header_len will be different, and
1592 * we have to adjust mss_now correspondingly */
1593 if (header_len != tp->tcp_header_len) {
1594 int delta = (int) header_len - tp->tcp_header_len;
1595 mss_now -= delta;
1596 }
1597
1598 return mss_now;
1599}
1600
1601/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1602 * As additional protections, we do not touch cwnd in retransmission phases,
1603 * and if application hit its sndbuf limit recently.
1604 */
1605static void tcp_cwnd_application_limited(struct sock *sk)
1606{
1607 struct tcp_sock *tp = tcp_sk(sk);
1608
1609 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
1610 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
1611 /* Limited by application or receiver window. */
1612 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
1613 u32 win_used = max(tp->snd_cwnd_used, init_win);
1614 if (win_used < tp->snd_cwnd) {
1615 tp->snd_ssthresh = tcp_current_ssthresh(sk);
1616 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
1617 }
1618 tp->snd_cwnd_used = 0;
1619 }
1620 tp->snd_cwnd_stamp = tcp_jiffies32;
1621}
1622
1623static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1624{
1625 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1626 struct tcp_sock *tp = tcp_sk(sk);
1627
1628 /* Track the maximum number of outstanding packets in each
1629 * window, and remember whether we were cwnd-limited then.
1630 */
1631 if (!before(tp->snd_una, tp->max_packets_seq) ||
1632 tp->packets_out > tp->max_packets_out) {
1633 tp->max_packets_out = tp->packets_out;
1634 tp->max_packets_seq = tp->snd_nxt;
1635 tp->is_cwnd_limited = is_cwnd_limited;
1636 }
1637
1638 if (tcp_is_cwnd_limited(sk)) {
1639 /* Network is feed fully. */
1640 tp->snd_cwnd_used = 0;
1641 tp->snd_cwnd_stamp = tcp_jiffies32;
1642 } else {
1643 /* Network starves. */
1644 if (tp->packets_out > tp->snd_cwnd_used)
1645 tp->snd_cwnd_used = tp->packets_out;
1646
1647 if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle &&
1648 (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1649 !ca_ops->cong_control)
1650 tcp_cwnd_application_limited(sk);
1651
1652 /* The following conditions together indicate the starvation
1653 * is caused by insufficient sender buffer:
1654 * 1) just sent some data (see tcp_write_xmit)
1655 * 2) not cwnd limited (this else condition)
1656 * 3) no more data to send (tcp_write_queue_empty())
1657 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1658 */
1659 if (tcp_write_queue_empty(sk) && sk->sk_socket &&
1660 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
1661 (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
1662 tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1663 }
1664}
1665
1666/* Minshall's variant of the Nagle send check. */
1667static bool tcp_minshall_check(const struct tcp_sock *tp)
1668{
1669 return after(tp->snd_sml, tp->snd_una) &&
1670 !after(tp->snd_sml, tp->snd_nxt);
1671}
1672
1673/* Update snd_sml if this skb is under mss
1674 * Note that a TSO packet might end with a sub-mss segment
1675 * The test is really :
1676 * if ((skb->len % mss) != 0)
1677 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1678 * But we can avoid doing the divide again given we already have
1679 * skb_pcount = skb->len / mss_now
1680 */
1681static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1682 const struct sk_buff *skb)
1683{
1684 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1685 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1686}
1687
1688/* Return false, if packet can be sent now without violation Nagle's rules:
1689 * 1. It is full sized. (provided by caller in %partial bool)
1690 * 2. Or it contains FIN. (already checked by caller)
1691 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1692 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1693 * With Minshall's modification: all sent small packets are ACKed.
1694 */
1695static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1696 int nonagle)
1697{
1698 return partial &&
1699 ((nonagle & TCP_NAGLE_CORK) ||
1700 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1701}
1702
1703/* Return how many segs we'd like on a TSO packet,
1704 * to send one TSO packet per ms
1705 */
1706static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
1707 int min_tso_segs)
1708{
1709 u32 bytes, segs;
1710
1711 bytes = min(sk->sk_pacing_rate >> sk->sk_pacing_shift,
1712 sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);
1713
1714 /* Goal is to send at least one packet per ms,
1715 * not one big TSO packet every 100 ms.
1716 * This preserves ACK clocking and is consistent
1717 * with tcp_tso_should_defer() heuristic.
1718 */
1719 segs = max_t(u32, bytes / mss_now, min_tso_segs);
1720
1721 return segs;
1722}
1723
1724/* Return the number of segments we want in the skb we are transmitting.
1725 * See if congestion control module wants to decide; otherwise, autosize.
1726 */
1727static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
1728{
1729 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1730 u32 min_tso, tso_segs;
1731
1732 min_tso = ca_ops->min_tso_segs ?
1733 ca_ops->min_tso_segs(sk) :
1734 sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
1735
1736 tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
1737 return min_t(u32, tso_segs, sk->sk_gso_max_segs);
1738}
1739
1740/* Returns the portion of skb which can be sent right away */
1741static unsigned int tcp_mss_split_point(const struct sock *sk,
1742 const struct sk_buff *skb,
1743 unsigned int mss_now,
1744 unsigned int max_segs,
1745 int nonagle)
1746{
1747 const struct tcp_sock *tp = tcp_sk(sk);
1748 u32 partial, needed, window, max_len;
1749
1750 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1751 max_len = mss_now * max_segs;
1752
1753 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1754 return max_len;
1755
1756 needed = min(skb->len, window);
1757
1758 if (max_len <= needed)
1759 return max_len;
1760
1761 partial = needed % mss_now;
1762 /* If last segment is not a full MSS, check if Nagle rules allow us
1763 * to include this last segment in this skb.
1764 * Otherwise, we'll split the skb at last MSS boundary
1765 */
1766 if (tcp_nagle_check(partial != 0, tp, nonagle))
1767 return needed - partial;
1768
1769 return needed;
1770}
1771
1772/* Can at least one segment of SKB be sent right now, according to the
1773 * congestion window rules? If so, return how many segments are allowed.
1774 */
1775static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1776 const struct sk_buff *skb)
1777{
1778 u32 in_flight, cwnd, halfcwnd;
1779
1780 /* Don't be strict about the congestion window for the final FIN. */
1781 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1782 tcp_skb_pcount(skb) == 1)
1783 return 1;
1784
1785 in_flight = tcp_packets_in_flight(tp);
1786 cwnd = tp->snd_cwnd;
1787 if (in_flight >= cwnd)
1788 return 0;
1789
1790 /* For better scheduling, ensure we have at least
1791 * 2 GSO packets in flight.
1792 */
1793 halfcwnd = max(cwnd >> 1, 1U);
1794 return min(halfcwnd, cwnd - in_flight);
1795}
1796
1797/* Initialize TSO state of a skb.
1798 * This must be invoked the first time we consider transmitting
1799 * SKB onto the wire.
1800 */
1801static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1802{
1803 int tso_segs = tcp_skb_pcount(skb);
1804
1805 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1806 tcp_set_skb_tso_segs(skb, mss_now);
1807 tso_segs = tcp_skb_pcount(skb);
1808 }
1809 return tso_segs;
1810}
1811
1812
1813/* Return true if the Nagle test allows this packet to be
1814 * sent now.
1815 */
1816static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1817 unsigned int cur_mss, int nonagle)
1818{
1819 /* Nagle rule does not apply to frames, which sit in the middle of the
1820 * write_queue (they have no chances to get new data).
1821 *
1822 * This is implemented in the callers, where they modify the 'nonagle'
1823 * argument based upon the location of SKB in the send queue.
1824 */
1825 if (nonagle & TCP_NAGLE_PUSH)
1826 return true;
1827
1828 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1829 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1830 return true;
1831
1832 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
1833 return true;
1834
1835 return false;
1836}
1837
1838/* Does at least the first segment of SKB fit into the send window? */
1839static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1840 const struct sk_buff *skb,
1841 unsigned int cur_mss)
1842{
1843 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1844
1845 if (skb->len > cur_mss)
1846 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1847
1848 return !after(end_seq, tcp_wnd_end(tp));
1849}
1850
1851/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1852 * which is put after SKB on the list. It is very much like
1853 * tcp_fragment() except that it may make several kinds of assumptions
1854 * in order to speed up the splitting operation. In particular, we
1855 * know that all the data is in scatter-gather pages, and that the
1856 * packet has never been sent out before (and thus is not cloned).
1857 */
1858static int tso_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1859 struct sk_buff *skb, unsigned int len,
1860 unsigned int mss_now, gfp_t gfp)
1861{
1862 struct sk_buff *buff;
1863 int nlen = skb->len - len;
1864 u8 flags;
1865
1866 /* All of a TSO frame must be composed of paged data. */
1867 if (skb->len != skb->data_len)
1868 return tcp_fragment(sk, tcp_queue, skb, len, mss_now, gfp);
1869
1870 buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1871 if (unlikely(!buff))
1872 return -ENOMEM;
1873
1874 sk->sk_wmem_queued += buff->truesize;
1875 sk_mem_charge(sk, buff->truesize);
1876 buff->truesize += nlen;
1877 skb->truesize -= nlen;
1878
1879 /* Correct the sequence numbers. */
1880 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1881 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1882 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1883
1884 /* PSH and FIN should only be set in the second packet. */
1885 flags = TCP_SKB_CB(skb)->tcp_flags;
1886 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1887 TCP_SKB_CB(buff)->tcp_flags = flags;
1888
1889 /* This packet was never sent out yet, so no SACK bits. */
1890 TCP_SKB_CB(buff)->sacked = 0;
1891
1892 tcp_skb_fragment_eor(skb, buff);
1893
1894 buff->ip_summed = CHECKSUM_PARTIAL;
1895 skb_split(skb, buff, len);
1896 tcp_fragment_tstamp(skb, buff);
1897
1898 /* Fix up tso_factor for both original and new SKB. */
1899 tcp_set_skb_tso_segs(skb, mss_now);
1900 tcp_set_skb_tso_segs(buff, mss_now);
1901
1902 /* Link BUFF into the send queue. */
1903 __skb_header_release(buff);
1904 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1905
1906 return 0;
1907}
1908
1909/* Try to defer sending, if possible, in order to minimize the amount
1910 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1911 *
1912 * This algorithm is from John Heffner.
1913 */
1914static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
1915 bool *is_cwnd_limited, u32 max_segs)
1916{
1917 const struct inet_connection_sock *icsk = inet_csk(sk);
1918 u32 age, send_win, cong_win, limit, in_flight;
1919 struct tcp_sock *tp = tcp_sk(sk);
1920 struct sk_buff *head;
1921 int win_divisor;
1922
1923 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1924 goto send_now;
1925
1926 if (icsk->icsk_ca_state >= TCP_CA_Recovery)
1927 goto send_now;
1928
1929 /* Avoid bursty behavior by allowing defer
1930 * only if the last write was recent.
1931 */
1932 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 0)
1933 goto send_now;
1934
1935 in_flight = tcp_packets_in_flight(tp);
1936
1937 BUG_ON(tcp_skb_pcount(skb) <= 1);
1938 BUG_ON(tp->snd_cwnd <= in_flight);
1939
1940 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1941
1942 /* From in_flight test above, we know that cwnd > in_flight. */
1943 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1944
1945 limit = min(send_win, cong_win);
1946
1947 /* If a full-sized TSO skb can be sent, do it. */
1948 if (limit >= max_segs * tp->mss_cache)
1949 goto send_now;
1950
1951 /* Middle in queue won't get any more data, full sendable already? */
1952 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
1953 goto send_now;
1954
1955 win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
1956 if (win_divisor) {
1957 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1958
1959 /* If at least some fraction of a window is available,
1960 * just use it.
1961 */
1962 chunk /= win_divisor;
1963 if (limit >= chunk)
1964 goto send_now;
1965 } else {
1966 /* Different approach, try not to defer past a single
1967 * ACK. Receiver should ACK every other full sized
1968 * frame, so if we have space for more than 3 frames
1969 * then send now.
1970 */
1971 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
1972 goto send_now;
1973 }
1974
1975 /* TODO : use tsorted_sent_queue ? */
1976 head = tcp_rtx_queue_head(sk);
1977 if (!head)
1978 goto send_now;
1979 age = tcp_stamp_us_delta(tp->tcp_mstamp, head->skb_mstamp);
1980 /* If next ACK is likely to come too late (half srtt), do not defer */
1981 if (age < (tp->srtt_us >> 4))
1982 goto send_now;
1983
1984 /* Ok, it looks like it is advisable to defer. */
1985
1986 if (cong_win < send_win && cong_win <= skb->len)
1987 *is_cwnd_limited = true;
1988
1989 return true;
1990
1991send_now:
1992 return false;
1993}
1994
1995static inline void tcp_mtu_check_reprobe(struct sock *sk)
1996{
1997 struct inet_connection_sock *icsk = inet_csk(sk);
1998 struct tcp_sock *tp = tcp_sk(sk);
1999 struct net *net = sock_net(sk);
2000 u32 interval;
2001 s32 delta;
2002
2003 interval = net->ipv4.sysctl_tcp_probe_interval;
2004 delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2005 if (unlikely(delta >= interval * HZ)) {
2006 int mss = tcp_current_mss(sk);
2007
2008 /* Update current search range */
2009 icsk->icsk_mtup.probe_size = 0;
2010 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
2011 sizeof(struct tcphdr) +
2012 icsk->icsk_af_ops->net_header_len;
2013 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
2014
2015 /* Update probe time stamp */
2016 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2017 }
2018}
2019
2020static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
2021{
2022 struct sk_buff *skb, *next;
2023
2024 skb = tcp_send_head(sk);
2025 tcp_for_write_queue_from_safe(skb, next, sk) {
2026 if (len <= skb->len)
2027 break;
2028
2029 if (unlikely(TCP_SKB_CB(skb)->eor))
2030 return false;
2031
2032 len -= skb->len;
2033 }
2034
2035 return true;
2036}
2037
2038/* Create a new MTU probe if we are ready.
2039 * MTU probe is regularly attempting to increase the path MTU by
2040 * deliberately sending larger packets. This discovers routing
2041 * changes resulting in larger path MTUs.
2042 *
2043 * Returns 0 if we should wait to probe (no cwnd available),
2044 * 1 if a probe was sent,
2045 * -1 otherwise
2046 */
2047static int tcp_mtu_probe(struct sock *sk)
2048{
2049 struct inet_connection_sock *icsk = inet_csk(sk);
2050 struct tcp_sock *tp = tcp_sk(sk);
2051 struct sk_buff *skb, *nskb, *next;
2052 struct net *net = sock_net(sk);
2053 int probe_size;
2054 int size_needed;
2055 int copy, len;
2056 int mss_now;
2057 int interval;
2058
2059 /* Not currently probing/verifying,
2060 * not in recovery,
2061 * have enough cwnd, and
2062 * not SACKing (the variable headers throw things off)
2063 */
2064 if (likely(!icsk->icsk_mtup.enabled ||
2065 icsk->icsk_mtup.probe_size ||
2066 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
2067 tp->snd_cwnd < 11 ||
2068 tp->rx_opt.num_sacks || tp->rx_opt.dsack))
2069 return -1;
2070
2071 /* Use binary search for probe_size between tcp_mss_base,
2072 * and current mss_clamp. if (search_high - search_low)
2073 * smaller than a threshold, backoff from probing.
2074 */
2075 mss_now = tcp_current_mss(sk);
2076 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
2077 icsk->icsk_mtup.search_low) >> 1);
2078 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2079 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2080 /* When misfortune happens, we are reprobing actively,
2081 * and then reprobe timer has expired. We stick with current
2082 * probing process by not resetting search range to its orignal.
2083 */
2084 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2085 interval < net->ipv4.sysctl_tcp_probe_threshold) {
2086 /* Check whether enough time has elaplased for
2087 * another round of probing.
2088 */
2089 tcp_mtu_check_reprobe(sk);
2090 return -1;
2091 }
2092
2093 /* Have enough data in the send queue to probe? */
2094 if (tp->write_seq - tp->snd_nxt < size_needed)
2095 return -1;
2096
2097 if (tp->snd_wnd < size_needed)
2098 return -1;
2099 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2100 return 0;
2101
2102 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2103 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
2104 if (!tcp_packets_in_flight(tp))
2105 return -1;
2106 else
2107 return 0;
2108 }
2109
2110 if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
2111 return -1;
2112
2113 /* We're allowed to probe. Build it now. */
2114 nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2115 if (!nskb)
2116 return -1;
2117 sk->sk_wmem_queued += nskb->truesize;
2118 sk_mem_charge(sk, nskb->truesize);
2119
2120 skb = tcp_send_head(sk);
2121
2122 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
2123 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
2124 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
2125 TCP_SKB_CB(nskb)->sacked = 0;
2126 nskb->csum = 0;
2127 nskb->ip_summed = CHECKSUM_PARTIAL;
2128
2129 tcp_insert_write_queue_before(nskb, skb, sk);
2130 tcp_highest_sack_replace(sk, skb, nskb);
2131
2132 len = 0;
2133 tcp_for_write_queue_from_safe(skb, next, sk) {
2134 copy = min_t(int, skb->len, probe_size - len);
2135 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2136
2137 if (skb->len <= copy) {
2138 /* We've eaten all the data from this skb.
2139 * Throw it away. */
2140 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2141 /* If this is the last SKB we copy and eor is set
2142 * we need to propagate it to the new skb.
2143 */
2144 TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
2145 tcp_unlink_write_queue(skb, sk);
2146 sk_wmem_free_skb(sk, skb);
2147 } else {
2148 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
2149 ~(TCPHDR_FIN|TCPHDR_PSH);
2150 if (!skb_shinfo(skb)->nr_frags) {
2151 skb_pull(skb, copy);
2152 } else {
2153 __pskb_trim_head(skb, copy);
2154 tcp_set_skb_tso_segs(skb, mss_now);
2155 }
2156 TCP_SKB_CB(skb)->seq += copy;
2157 }
2158
2159 len += copy;
2160
2161 if (len >= probe_size)
2162 break;
2163 }
2164 tcp_init_tso_segs(nskb, nskb->len);
2165
2166 /* We're ready to send. If this fails, the probe will
2167 * be resegmented into mss-sized pieces by tcp_write_xmit().
2168 */
2169 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
2170 /* Decrement cwnd here because we are sending
2171 * effectively two packets. */
2172 tp->snd_cwnd--;
2173 tcp_event_new_data_sent(sk, nskb);
2174
2175 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2176 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
2177 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
2178
2179 return 1;
2180 }
2181
2182 return -1;
2183}
2184
2185static bool tcp_pacing_check(const struct sock *sk)
2186{
2187 return tcp_needs_internal_pacing(sk) &&
2188 hrtimer_active(&tcp_sk(sk)->pacing_timer);
2189}
2190
2191/* TCP Small Queues :
2192 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2193 * (These limits are doubled for retransmits)
2194 * This allows for :
2195 * - better RTT estimation and ACK scheduling
2196 * - faster recovery
2197 * - high rates
2198 * Alas, some drivers / subsystems require a fair amount
2199 * of queued bytes to ensure line rate.
2200 * One example is wifi aggregation (802.11 AMPDU)
2201 */
2202static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
2203 unsigned int factor)
2204{
2205 unsigned int limit;
2206
2207 limit = max(2 * skb->truesize, sk->sk_pacing_rate >> sk->sk_pacing_shift);
2208 limit = min_t(u32, limit,
2209 sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
2210 limit <<= factor;
2211
2212 if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2213 /* Always send skb if rtx queue is empty.
2214 * No need to wait for TX completion to call us back,
2215 * after softirq/tasklet schedule.
2216 * This helps when TX completions are delayed too much.
2217 */
2218 if (tcp_rtx_queue_empty(sk))
2219 return false;
2220
2221 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2222 /* It is possible TX completion already happened
2223 * before we set TSQ_THROTTLED, so we must
2224 * test again the condition.
2225 */
2226 smp_mb__after_atomic();
2227 if (refcount_read(&sk->sk_wmem_alloc) > limit)
2228 return true;
2229 }
2230 return false;
2231}
2232
2233static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
2234{
2235 const u32 now = tcp_jiffies32;
2236 enum tcp_chrono old = tp->chrono_type;
2237
2238 if (old > TCP_CHRONO_UNSPEC)
2239 tp->chrono_stat[old - 1] += now - tp->chrono_start;
2240 tp->chrono_start = now;
2241 tp->chrono_type = new;
2242}
2243
2244void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
2245{
2246 struct tcp_sock *tp = tcp_sk(sk);
2247
2248 /* If there are multiple conditions worthy of tracking in a
2249 * chronograph then the highest priority enum takes precedence
2250 * over the other conditions. So that if something "more interesting"
2251 * starts happening, stop the previous chrono and start a new one.
2252 */
2253 if (type > tp->chrono_type)
2254 tcp_chrono_set(tp, type);
2255}
2256
2257void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
2258{
2259 struct tcp_sock *tp = tcp_sk(sk);
2260
2261
2262 /* There are multiple conditions worthy of tracking in a
2263 * chronograph, so that the highest priority enum takes
2264 * precedence over the other conditions (see tcp_chrono_start).
2265 * If a condition stops, we only stop chrono tracking if
2266 * it's the "most interesting" or current chrono we are
2267 * tracking and starts busy chrono if we have pending data.
2268 */
2269 if (tcp_rtx_and_write_queues_empty(sk))
2270 tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
2271 else if (type == tp->chrono_type)
2272 tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2273}
2274
2275/* This routine writes packets to the network. It advances the
2276 * send_head. This happens as incoming acks open up the remote
2277 * window for us.
2278 *
2279 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2280 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2281 * account rare use of URG, this is not a big flaw.
2282 *
2283 * Send at most one packet when push_one > 0. Temporarily ignore
2284 * cwnd limit to force at most one packet out when push_one == 2.
2285
2286 * Returns true, if no segments are in flight and we have queued segments,
2287 * but cannot send anything now because of SWS or another problem.
2288 */
2289static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2290 int push_one, gfp_t gfp)
2291{
2292 struct tcp_sock *tp = tcp_sk(sk);
2293 struct sk_buff *skb;
2294 unsigned int tso_segs, sent_pkts;
2295 int cwnd_quota;
2296 int result;
2297 bool is_cwnd_limited = false, is_rwnd_limited = false;
2298 u32 max_segs;
2299
2300 sent_pkts = 0;
2301
2302 tcp_mstamp_refresh(tp);
2303 if (!push_one) {
2304 /* Do MTU probing. */
2305 result = tcp_mtu_probe(sk);
2306 if (!result) {
2307 return false;
2308 } else if (result > 0) {
2309 sent_pkts = 1;
2310 }
2311 }
2312
2313 max_segs = tcp_tso_segs(sk, mss_now);
2314 while ((skb = tcp_send_head(sk))) {
2315 unsigned int limit;
2316
2317 if (tcp_pacing_check(sk))
2318 break;
2319
2320 tso_segs = tcp_init_tso_segs(skb, mss_now);
2321 BUG_ON(!tso_segs);
2322
2323 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2324 /* "skb_mstamp" is used as a start point for the retransmit timer */
2325 tcp_update_skb_after_send(tp, skb);
2326 goto repair; /* Skip network transmission */
2327 }
2328
2329 cwnd_quota = tcp_cwnd_test(tp, skb);
2330 if (!cwnd_quota) {
2331 if (push_one == 2)
2332 /* Force out a loss probe pkt. */
2333 cwnd_quota = 1;
2334 else
2335 break;
2336 }
2337
2338 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
2339 is_rwnd_limited = true;
2340 break;
2341 }
2342
2343 if (tso_segs == 1) {
2344 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2345 (tcp_skb_is_last(sk, skb) ?
2346 nonagle : TCP_NAGLE_PUSH))))
2347 break;
2348 } else {
2349 if (!push_one &&
2350 tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2351 max_segs))
2352 break;
2353 }
2354
2355 limit = mss_now;
2356 if (tso_segs > 1 && !tcp_urg_mode(tp))
2357 limit = tcp_mss_split_point(sk, skb, mss_now,
2358 min_t(unsigned int,
2359 cwnd_quota,
2360 max_segs),
2361 nonagle);
2362
2363 if (skb->len > limit &&
2364 unlikely(tso_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
2365 skb, limit, mss_now, gfp)))
2366 break;
2367
2368 if (test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
2369 clear_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags);
2370 if (tcp_small_queue_check(sk, skb, 0))
2371 break;
2372
2373 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2374 break;
2375
2376repair:
2377 /* Advance the send_head. This one is sent out.
2378 * This call will increment packets_out.
2379 */
2380 tcp_event_new_data_sent(sk, skb);
2381
2382 tcp_minshall_update(tp, mss_now, skb);
2383 sent_pkts += tcp_skb_pcount(skb);
2384
2385 if (push_one)
2386 break;
2387 }
2388
2389 if (is_rwnd_limited)
2390 tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
2391 else
2392 tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
2393
2394 if (likely(sent_pkts)) {
2395 if (tcp_in_cwnd_reduction(sk))
2396 tp->prr_out += sent_pkts;
2397
2398 /* Send one loss probe per tail loss episode. */
2399 if (push_one != 2)
2400 tcp_schedule_loss_probe(sk, false);
2401 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2402 tcp_cwnd_validate(sk, is_cwnd_limited);
2403 return false;
2404 }
2405 return !tp->packets_out && !tcp_write_queue_empty(sk);
2406}
2407
2408bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
2409{
2410 struct inet_connection_sock *icsk = inet_csk(sk);
2411 struct tcp_sock *tp = tcp_sk(sk);
2412 u32 timeout, rto_delta_us;
2413 int early_retrans;
2414
2415 /* Don't do any loss probe on a Fast Open connection before 3WHS
2416 * finishes.
2417 */
2418 if (tp->fastopen_rsk)
2419 return false;
2420
2421 early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
2422 /* Schedule a loss probe in 2*RTT for SACK capable connections
2423 * not in loss recovery, that are either limited by cwnd or application.
2424 */
2425 if ((early_retrans != 3 && early_retrans != 4) ||
2426 !tp->packets_out || !tcp_is_sack(tp) ||
2427 (icsk->icsk_ca_state != TCP_CA_Open &&
2428 icsk->icsk_ca_state != TCP_CA_CWR))
2429 return false;
2430
2431 /* Probe timeout is 2*rtt. Add minimum RTO to account
2432 * for delayed ack when there's one outstanding packet. If no RTT
2433 * sample is available then probe after TCP_TIMEOUT_INIT.
2434 */
2435 if (tp->srtt_us) {
2436 timeout = usecs_to_jiffies(tp->srtt_us >> 2);
2437 if (tp->packets_out == 1)
2438 timeout += TCP_RTO_MIN;
2439 else
2440 timeout += TCP_TIMEOUT_MIN;
2441 } else {
2442 timeout = TCP_TIMEOUT_INIT;
2443 }
2444
2445 /* If the RTO formula yields an earlier time, then use that time. */
2446 rto_delta_us = advancing_rto ?
2447 jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
2448 tcp_rto_delta_us(sk); /* How far in future is RTO? */
2449 if (rto_delta_us > 0)
2450 timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
2451
2452 inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
2453 TCP_RTO_MAX);
2454 return true;
2455}
2456
2457/* Thanks to skb fast clones, we can detect if a prior transmit of
2458 * a packet is still in a qdisc or driver queue.
2459 * In this case, there is very little point doing a retransmit !
2460 */
2461static bool skb_still_in_host_queue(const struct sock *sk,
2462 const struct sk_buff *skb)
2463{
2464 if (unlikely(skb_fclone_busy(sk, skb))) {
2465 NET_INC_STATS(sock_net(sk),
2466 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2467 return true;
2468 }
2469 return false;
2470}
2471
2472/* When probe timeout (PTO) fires, try send a new segment if possible, else
2473 * retransmit the last segment.
2474 */
2475void tcp_send_loss_probe(struct sock *sk)
2476{
2477 struct tcp_sock *tp = tcp_sk(sk);
2478 struct sk_buff *skb;
2479 int pcount;
2480 int mss = tcp_current_mss(sk);
2481
2482 skb = tcp_send_head(sk);
2483 if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
2484 pcount = tp->packets_out;
2485 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2486 if (tp->packets_out > pcount)
2487 goto probe_sent;
2488 goto rearm_timer;
2489 }
2490 skb = skb_rb_last(&sk->tcp_rtx_queue);
2491
2492 /* At most one outstanding TLP retransmission. */
2493 if (tp->tlp_high_seq)
2494 goto rearm_timer;
2495
2496 /* Retransmit last segment. */
2497 if (WARN_ON(!skb))
2498 goto rearm_timer;
2499
2500 if (skb_still_in_host_queue(sk, skb))
2501 goto rearm_timer;
2502
2503 pcount = tcp_skb_pcount(skb);
2504 if (WARN_ON(!pcount))
2505 goto rearm_timer;
2506
2507 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2508 if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
2509 (pcount - 1) * mss, mss,
2510 GFP_ATOMIC)))
2511 goto rearm_timer;
2512 skb = skb_rb_next(skb);
2513 }
2514
2515 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2516 goto rearm_timer;
2517
2518 if (__tcp_retransmit_skb(sk, skb, 1))
2519 goto rearm_timer;
2520
2521 /* Record snd_nxt for loss detection. */
2522 tp->tlp_high_seq = tp->snd_nxt;
2523
2524probe_sent:
2525 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2526 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2527 inet_csk(sk)->icsk_pending = 0;
2528rearm_timer:
2529 tcp_rearm_rto(sk);
2530}
2531
2532/* Push out any pending frames which were held back due to
2533 * TCP_CORK or attempt at coalescing tiny packets.
2534 * The socket must be locked by the caller.
2535 */
2536void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2537 int nonagle)
2538{
2539 /* If we are closed, the bytes will have to remain here.
2540 * In time closedown will finish, we empty the write queue and
2541 * all will be happy.
2542 */
2543 if (unlikely(sk->sk_state == TCP_CLOSE))
2544 return;
2545
2546 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2547 sk_gfp_mask(sk, GFP_ATOMIC)))
2548 tcp_check_probe_timer(sk);
2549}
2550
2551/* Send _single_ skb sitting at the send head. This function requires
2552 * true push pending frames to setup probe timer etc.
2553 */
2554void tcp_push_one(struct sock *sk, unsigned int mss_now)
2555{
2556 struct sk_buff *skb = tcp_send_head(sk);
2557
2558 BUG_ON(!skb || skb->len < mss_now);
2559
2560 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2561}
2562
2563/* This function returns the amount that we can raise the
2564 * usable window based on the following constraints
2565 *
2566 * 1. The window can never be shrunk once it is offered (RFC 793)
2567 * 2. We limit memory per socket
2568 *
2569 * RFC 1122:
2570 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2571 * RECV.NEXT + RCV.WIN fixed until:
2572 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2573 *
2574 * i.e. don't raise the right edge of the window until you can raise
2575 * it at least MSS bytes.
2576 *
2577 * Unfortunately, the recommended algorithm breaks header prediction,
2578 * since header prediction assumes th->window stays fixed.
2579 *
2580 * Strictly speaking, keeping th->window fixed violates the receiver
2581 * side SWS prevention criteria. The problem is that under this rule
2582 * a stream of single byte packets will cause the right side of the
2583 * window to always advance by a single byte.
2584 *
2585 * Of course, if the sender implements sender side SWS prevention
2586 * then this will not be a problem.
2587 *
2588 * BSD seems to make the following compromise:
2589 *
2590 * If the free space is less than the 1/4 of the maximum
2591 * space available and the free space is less than 1/2 mss,
2592 * then set the window to 0.
2593 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2594 * Otherwise, just prevent the window from shrinking
2595 * and from being larger than the largest representable value.
2596 *
2597 * This prevents incremental opening of the window in the regime
2598 * where TCP is limited by the speed of the reader side taking
2599 * data out of the TCP receive queue. It does nothing about
2600 * those cases where the window is constrained on the sender side
2601 * because the pipeline is full.
2602 *
2603 * BSD also seems to "accidentally" limit itself to windows that are a
2604 * multiple of MSS, at least until the free space gets quite small.
2605 * This would appear to be a side effect of the mbuf implementation.
2606 * Combining these two algorithms results in the observed behavior
2607 * of having a fixed window size at almost all times.
2608 *
2609 * Below we obtain similar behavior by forcing the offered window to
2610 * a multiple of the mss when it is feasible to do so.
2611 *
2612 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2613 * Regular options like TIMESTAMP are taken into account.
2614 */
2615u32 __tcp_select_window(struct sock *sk)
2616{
2617 struct inet_connection_sock *icsk = inet_csk(sk);
2618 struct tcp_sock *tp = tcp_sk(sk);
2619 /* MSS for the peer's data. Previous versions used mss_clamp
2620 * here. I don't know if the value based on our guesses
2621 * of peer's MSS is better for the performance. It's more correct
2622 * but may be worse for the performance because of rcv_mss
2623 * fluctuations. --SAW 1998/11/1
2624 */
2625 int mss = icsk->icsk_ack.rcv_mss;
2626 int free_space = tcp_space(sk);
2627 int allowed_space = tcp_full_space(sk);
2628 int full_space = min_t(int, tp->window_clamp, allowed_space);
2629 int window;
2630
2631 if (unlikely(mss > full_space)) {
2632 mss = full_space;
2633 if (mss <= 0)
2634 return 0;
2635 }
2636 if (free_space < (full_space >> 1)) {
2637 icsk->icsk_ack.quick = 0;
2638
2639 if (tcp_under_memory_pressure(sk))
2640 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2641 4U * tp->advmss);
2642
2643 /* free_space might become our new window, make sure we don't
2644 * increase it due to wscale.
2645 */
2646 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2647
2648 /* if free space is less than mss estimate, or is below 1/16th
2649 * of the maximum allowed, try to move to zero-window, else
2650 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2651 * new incoming data is dropped due to memory limits.
2652 * With large window, mss test triggers way too late in order
2653 * to announce zero window in time before rmem limit kicks in.
2654 */
2655 if (free_space < (allowed_space >> 4) || free_space < mss)
2656 return 0;
2657 }
2658
2659 if (free_space > tp->rcv_ssthresh)
2660 free_space = tp->rcv_ssthresh;
2661
2662 /* Don't do rounding if we are using window scaling, since the
2663 * scaled window will not line up with the MSS boundary anyway.
2664 */
2665 if (tp->rx_opt.rcv_wscale) {
2666 window = free_space;
2667
2668 /* Advertise enough space so that it won't get scaled away.
2669 * Import case: prevent zero window announcement if
2670 * 1<<rcv_wscale > mss.
2671 */
2672 window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
2673 } else {
2674 window = tp->rcv_wnd;
2675 /* Get the largest window that is a nice multiple of mss.
2676 * Window clamp already applied above.
2677 * If our current window offering is within 1 mss of the
2678 * free space we just keep it. This prevents the divide
2679 * and multiply from happening most of the time.
2680 * We also don't do any window rounding when the free space
2681 * is too small.
2682 */
2683 if (window <= free_space - mss || window > free_space)
2684 window = rounddown(free_space, mss);
2685 else if (mss == full_space &&
2686 free_space > window + (full_space >> 1))
2687 window = free_space;
2688 }
2689
2690 return window;
2691}
2692
2693void tcp_skb_collapse_tstamp(struct sk_buff *skb,
2694 const struct sk_buff *next_skb)
2695{
2696 if (unlikely(tcp_has_tx_tstamp(next_skb))) {
2697 const struct skb_shared_info *next_shinfo =
2698 skb_shinfo(next_skb);
2699 struct skb_shared_info *shinfo = skb_shinfo(skb);
2700
2701 shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2702 shinfo->tskey = next_shinfo->tskey;
2703 TCP_SKB_CB(skb)->txstamp_ack |=
2704 TCP_SKB_CB(next_skb)->txstamp_ack;
2705 }
2706}
2707
2708/* Collapses two adjacent SKB's during retransmission. */
2709static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
2710{
2711 struct tcp_sock *tp = tcp_sk(sk);
2712 struct sk_buff *next_skb = skb_rb_next(skb);
2713 int skb_size, next_skb_size;
2714
2715 skb_size = skb->len;
2716 next_skb_size = next_skb->len;
2717
2718 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2719
2720 if (next_skb_size) {
2721 if (next_skb_size <= skb_availroom(skb))
2722 skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
2723 next_skb_size);
2724 else if (!skb_shift(skb, next_skb, next_skb_size))
2725 return false;
2726 }
2727 tcp_highest_sack_replace(sk, next_skb, skb);
2728
2729 /* Update sequence range on original skb. */
2730 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2731
2732 /* Merge over control information. This moves PSH/FIN etc. over */
2733 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2734
2735 /* All done, get rid of second SKB and account for it so
2736 * packet counting does not break.
2737 */
2738 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2739 TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2740
2741 /* changed transmit queue under us so clear hints */
2742 tcp_clear_retrans_hints_partial(tp);
2743 if (next_skb == tp->retransmit_skb_hint)
2744 tp->retransmit_skb_hint = skb;
2745
2746 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2747
2748 tcp_skb_collapse_tstamp(skb, next_skb);
2749
2750 tcp_rtx_queue_unlink_and_free(next_skb, sk);
2751 return true;
2752}
2753
2754/* Check if coalescing SKBs is legal. */
2755static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2756{
2757 if (tcp_skb_pcount(skb) > 1)
2758 return false;
2759 if (skb_cloned(skb))
2760 return false;
2761 /* Some heuristics for collapsing over SACK'd could be invented */
2762 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2763 return false;
2764
2765 return true;
2766}
2767
2768/* Collapse packets in the retransmit queue to make to create
2769 * less packets on the wire. This is only done on retransmission.
2770 */
2771static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2772 int space)
2773{
2774 struct tcp_sock *tp = tcp_sk(sk);
2775 struct sk_buff *skb = to, *tmp;
2776 bool first = true;
2777
2778 if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
2779 return;
2780 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2781 return;
2782
2783 skb_rbtree_walk_from_safe(skb, tmp) {
2784 if (!tcp_can_collapse(sk, skb))
2785 break;
2786
2787 if (!tcp_skb_can_collapse_to(to))
2788 break;
2789
2790 space -= skb->len;
2791
2792 if (first) {
2793 first = false;
2794 continue;
2795 }
2796
2797 if (space < 0)
2798 break;
2799
2800 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2801 break;
2802
2803 if (!tcp_collapse_retrans(sk, to))
2804 break;
2805 }
2806}
2807
2808/* This retransmits one SKB. Policy decisions and retransmit queue
2809 * state updates are done by the caller. Returns non-zero if an
2810 * error occurred which prevented the send.
2811 */
2812int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2813{
2814 struct inet_connection_sock *icsk = inet_csk(sk);
2815 struct tcp_sock *tp = tcp_sk(sk);
2816 unsigned int cur_mss;
2817 int diff, len, err;
2818
2819
2820 /* Inconclusive MTU probe */
2821 if (icsk->icsk_mtup.probe_size)
2822 icsk->icsk_mtup.probe_size = 0;
2823
2824 /* Do not sent more than we queued. 1/4 is reserved for possible
2825 * copying overhead: fragmentation, tunneling, mangling etc.
2826 */
2827 if (refcount_read(&sk->sk_wmem_alloc) >
2828 min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
2829 sk->sk_sndbuf))
2830 return -EAGAIN;
2831
2832 if (skb_still_in_host_queue(sk, skb))
2833 return -EBUSY;
2834
2835 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2836 if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
2837 WARN_ON_ONCE(1);
2838 return -EINVAL;
2839 }
2840 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
2841 return -ENOMEM;
2842 }
2843
2844 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
2845 return -EHOSTUNREACH; /* Routing failure or similar. */
2846
2847 cur_mss = tcp_current_mss(sk);
2848
2849 /* If receiver has shrunk his window, and skb is out of
2850 * new window, do not retransmit it. The exception is the
2851 * case, when window is shrunk to zero. In this case
2852 * our retransmit serves as a zero window probe.
2853 */
2854 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
2855 TCP_SKB_CB(skb)->seq != tp->snd_una)
2856 return -EAGAIN;
2857
2858 len = cur_mss * segs;
2859 if (skb->len > len) {
2860 if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
2861 cur_mss, GFP_ATOMIC))
2862 return -ENOMEM; /* We'll try again later. */
2863 } else {
2864 if (skb_unclone(skb, GFP_ATOMIC))
2865 return -ENOMEM;
2866
2867 diff = tcp_skb_pcount(skb);
2868 tcp_set_skb_tso_segs(skb, cur_mss);
2869 diff -= tcp_skb_pcount(skb);
2870 if (diff)
2871 tcp_adjust_pcount(sk, skb, diff);
2872 if (skb->len < cur_mss)
2873 tcp_retrans_try_collapse(sk, skb, cur_mss);
2874 }
2875
2876 /* RFC3168, section 6.1.1.1. ECN fallback */
2877 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
2878 tcp_ecn_clear_syn(sk, skb);
2879
2880 /* Update global and local TCP statistics. */
2881 segs = tcp_skb_pcount(skb);
2882 TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
2883 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2884 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2885 tp->total_retrans += segs;
2886
2887 /* make sure skb->data is aligned on arches that require it
2888 * and check if ack-trimming & collapsing extended the headroom
2889 * beyond what csum_start can cover.
2890 */
2891 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
2892 skb_headroom(skb) >= 0xFFFF)) {
2893 struct sk_buff *nskb;
2894
2895 tcp_skb_tsorted_save(skb) {
2896 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2897 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
2898 -ENOBUFS;
2899 } tcp_skb_tsorted_restore(skb);
2900
2901 if (!err) {
2902 tcp_update_skb_after_send(tp, skb);
2903 tcp_rate_skb_sent(sk, skb);
2904 }
2905 } else {
2906 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2907 }
2908
2909 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
2910 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
2911 TCP_SKB_CB(skb)->seq, segs, err);
2912
2913 if (likely(!err)) {
2914 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2915 trace_tcp_retransmit_skb(sk, skb);
2916 } else if (err != -EBUSY) {
2917 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2918 }
2919 return err;
2920}
2921
2922int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2923{
2924 struct tcp_sock *tp = tcp_sk(sk);
2925 int err = __tcp_retransmit_skb(sk, skb, segs);
2926
2927 if (err == 0) {
2928#if FASTRETRANS_DEBUG > 0
2929 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2930 net_dbg_ratelimited("retrans_out leaked\n");
2931 }
2932#endif
2933 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
2934 tp->retrans_out += tcp_skb_pcount(skb);
2935
2936 /* Save stamp of the first retransmit. */
2937 if (!tp->retrans_stamp)
2938 tp->retrans_stamp = tcp_skb_timestamp(skb);
2939
2940 }
2941
2942 if (tp->undo_retrans < 0)
2943 tp->undo_retrans = 0;
2944 tp->undo_retrans += tcp_skb_pcount(skb);
2945 return err;
2946}
2947
2948/* This gets called after a retransmit timeout, and the initially
2949 * retransmitted data is acknowledged. It tries to continue
2950 * resending the rest of the retransmit queue, until either
2951 * we've sent it all or the congestion window limit is reached.
2952 */
2953void tcp_xmit_retransmit_queue(struct sock *sk)
2954{
2955 const struct inet_connection_sock *icsk = inet_csk(sk);
2956 struct sk_buff *skb, *rtx_head, *hole = NULL;
2957 struct tcp_sock *tp = tcp_sk(sk);
2958 u32 max_segs;
2959 int mib_idx;
2960
2961 if (!tp->packets_out)
2962 return;
2963
2964 rtx_head = tcp_rtx_queue_head(sk);
2965 skb = tp->retransmit_skb_hint ?: rtx_head;
2966 max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
2967 skb_rbtree_walk_from(skb) {
2968 __u8 sacked;
2969 int segs;
2970
2971 if (tcp_pacing_check(sk))
2972 break;
2973
2974 /* we could do better than to assign each time */
2975 if (!hole)
2976 tp->retransmit_skb_hint = skb;
2977
2978 segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
2979 if (segs <= 0)
2980 return;
2981 sacked = TCP_SKB_CB(skb)->sacked;
2982 /* In case tcp_shift_skb_data() have aggregated large skbs,
2983 * we need to make sure not sending too bigs TSO packets
2984 */
2985 segs = min_t(int, segs, max_segs);
2986
2987 if (tp->retrans_out >= tp->lost_out) {
2988 break;
2989 } else if (!(sacked & TCPCB_LOST)) {
2990 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2991 hole = skb;
2992 continue;
2993
2994 } else {
2995 if (icsk->icsk_ca_state != TCP_CA_Loss)
2996 mib_idx = LINUX_MIB_TCPFASTRETRANS;
2997 else
2998 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
2999 }
3000
3001 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
3002 continue;
3003
3004 if (tcp_small_queue_check(sk, skb, 1))
3005 return;
3006
3007 if (tcp_retransmit_skb(sk, skb, segs))
3008 return;
3009
3010 NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
3011
3012 if (tcp_in_cwnd_reduction(sk))
3013 tp->prr_out += tcp_skb_pcount(skb);
3014
3015 if (skb == rtx_head &&
3016 icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3017 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3018 inet_csk(sk)->icsk_rto,
3019 TCP_RTO_MAX);
3020 }
3021}
3022
3023/* We allow to exceed memory limits for FIN packets to expedite
3024 * connection tear down and (memory) recovery.
3025 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3026 * or even be forced to close flow without any FIN.
3027 * In general, we want to allow one skb per socket to avoid hangs
3028 * with edge trigger epoll()
3029 */
3030void sk_forced_mem_schedule(struct sock *sk, int size)
3031{
3032 int amt;
3033
3034 if (size <= sk->sk_forward_alloc)
3035 return;
3036 amt = sk_mem_pages(size);
3037 sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
3038 sk_memory_allocated_add(sk, amt);
3039
3040 if (mem_cgroup_sockets_enabled && sk->sk_memcg)
3041 mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3042}
3043
3044/* Send a FIN. The caller locks the socket for us.
3045 * We should try to send a FIN packet really hard, but eventually give up.
3046 */
3047void tcp_send_fin(struct sock *sk)
3048{
3049 struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
3050 struct tcp_sock *tp = tcp_sk(sk);
3051
3052 /* Optimization, tack on the FIN if we have one skb in write queue and
3053 * this skb was not yet sent, or we are under memory pressure.
3054 * Note: in the latter case, FIN packet will be sent after a timeout,
3055 * as TCP stack thinks it has already been transmitted.
3056 */
3057 if (!tskb && tcp_under_memory_pressure(sk))
3058 tskb = skb_rb_last(&sk->tcp_rtx_queue);
3059
3060 if (tskb) {
3061coalesce:
3062 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
3063 TCP_SKB_CB(tskb)->end_seq++;
3064 tp->write_seq++;
3065 if (tcp_write_queue_empty(sk)) {
3066 /* This means tskb was already sent.
3067 * Pretend we included the FIN on previous transmit.
3068 * We need to set tp->snd_nxt to the value it would have
3069 * if FIN had been sent. This is because retransmit path
3070 * does not change tp->snd_nxt.
3071 */
3072 tp->snd_nxt++;
3073 return;
3074 }
3075 } else {
3076 skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
3077 if (unlikely(!skb)) {
3078 if (tskb)
3079 goto coalesce;
3080 return;
3081 }
3082 INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3083 skb_reserve(skb, MAX_TCP_HEADER);
3084 sk_forced_mem_schedule(sk, skb->truesize);
3085 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3086 tcp_init_nondata_skb(skb, tp->write_seq,
3087 TCPHDR_ACK | TCPHDR_FIN);
3088 tcp_queue_skb(sk, skb);
3089 }
3090 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
3091}
3092
3093/* We get here when a process closes a file descriptor (either due to
3094 * an explicit close() or as a byproduct of exit()'ing) and there
3095 * was unread data in the receive queue. This behavior is recommended
3096 * by RFC 2525, section 2.17. -DaveM
3097 */
3098void tcp_send_active_reset(struct sock *sk, gfp_t priority)
3099{
3100 struct sk_buff *skb;
3101
3102 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
3103
3104 /* NOTE: No TCP options attached and we never retransmit this. */
3105 skb = alloc_skb(MAX_TCP_HEADER, priority);
3106 if (!skb) {
3107 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3108 return;
3109 }
3110
3111 /* Reserve space for headers and prepare control bits. */
3112 skb_reserve(skb, MAX_TCP_HEADER);
3113 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
3114 TCPHDR_ACK | TCPHDR_RST);
3115 tcp_mstamp_refresh(tcp_sk(sk));
3116 /* Send it off. */
3117 if (tcp_transmit_skb(sk, skb, 0, priority))
3118 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3119
3120 /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3121 * skb here is different to the troublesome skb, so use NULL
3122 */
3123 trace_tcp_send_reset(sk, NULL);
3124}
3125
3126/* Send a crossed SYN-ACK during socket establishment.
3127 * WARNING: This routine must only be called when we have already sent
3128 * a SYN packet that crossed the incoming SYN that caused this routine
3129 * to get called. If this assumption fails then the initial rcv_wnd
3130 * and rcv_wscale values will not be correct.
3131 */
3132int tcp_send_synack(struct sock *sk)
3133{
3134 struct sk_buff *skb;
3135
3136 skb = tcp_rtx_queue_head(sk);
3137 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3138 pr_err("%s: wrong queue state\n", __func__);
3139 return -EFAULT;
3140 }
3141 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
3142 if (skb_cloned(skb)) {
3143 struct sk_buff *nskb;
3144
3145 tcp_skb_tsorted_save(skb) {
3146 nskb = skb_copy(skb, GFP_ATOMIC);
3147 } tcp_skb_tsorted_restore(skb);
3148 if (!nskb)
3149 return -ENOMEM;
3150 INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3151 tcp_rtx_queue_unlink_and_free(skb, sk);
3152 __skb_header_release(nskb);
3153 tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3154 sk->sk_wmem_queued += nskb->truesize;
3155 sk_mem_charge(sk, nskb->truesize);
3156 skb = nskb;
3157 }
3158
3159 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3160 tcp_ecn_send_synack(sk, skb);
3161 }
3162 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3163}
3164
3165/**
3166 * tcp_make_synack - Prepare a SYN-ACK.
3167 * sk: listener socket
3168 * dst: dst entry attached to the SYNACK
3169 * req: request_sock pointer
3170 *
3171 * Allocate one skb and build a SYNACK packet.
3172 * @dst is consumed : Caller should not use it again.
3173 */
3174struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3175 struct request_sock *req,
3176 struct tcp_fastopen_cookie *foc,
3177 enum tcp_synack_type synack_type)
3178{
3179 struct inet_request_sock *ireq = inet_rsk(req);
3180 const struct tcp_sock *tp = tcp_sk(sk);
3181 struct tcp_md5sig_key *md5 = NULL;
3182 struct tcp_out_options opts;
3183 struct sk_buff *skb;
3184 int tcp_header_size;
3185 struct tcphdr *th;
3186 int mss;
3187
3188 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3189 if (unlikely(!skb)) {
3190 dst_release(dst);
3191 return NULL;
3192 }
3193 /* Reserve space for headers. */
3194 skb_reserve(skb, MAX_TCP_HEADER);
3195
3196 switch (synack_type) {
3197 case TCP_SYNACK_NORMAL:
3198 skb_set_owner_w(skb, req_to_sk(req));
3199 break;
3200 case TCP_SYNACK_COOKIE:
3201 /* Under synflood, we do not attach skb to a socket,
3202 * to avoid false sharing.
3203 */
3204 break;
3205 case TCP_SYNACK_FASTOPEN:
3206 /* sk is a const pointer, because we want to express multiple
3207 * cpu might call us concurrently.
3208 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3209 */
3210 skb_set_owner_w(skb, (struct sock *)sk);
3211 break;
3212 }
3213 skb_dst_set(skb, dst);
3214
3215 mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3216
3217 memset(&opts, 0, sizeof(opts));
3218#ifdef CONFIG_SYN_COOKIES
3219 if (unlikely(req->cookie_ts))
3220 skb->skb_mstamp = cookie_init_timestamp(req);
3221 else
3222#endif
3223 skb->skb_mstamp = tcp_clock_us();
3224
3225#ifdef CONFIG_TCP_MD5SIG
3226 rcu_read_lock();
3227 md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
3228#endif
3229 skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3230 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
3231 foc) + sizeof(*th);
3232
3233 skb_push(skb, tcp_header_size);
3234 skb_reset_transport_header(skb);
3235
3236 th = (struct tcphdr *)skb->data;
3237 memset(th, 0, sizeof(struct tcphdr));
3238 th->syn = 1;
3239 th->ack = 1;
3240 tcp_ecn_make_synack(req, th);
3241 th->source = htons(ireq->ir_num);
3242 th->dest = ireq->ir_rmt_port;
3243 skb->mark = ireq->ir_mark;
3244 skb->ip_summed = CHECKSUM_PARTIAL;
3245 th->seq = htonl(tcp_rsk(req)->snt_isn);
3246 /* XXX data is queued and acked as is. No buffer/window check */
3247 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
3248
3249 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3250 th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3251 tcp_options_write((__be32 *)(th + 1), NULL, &opts);
3252 th->doff = (tcp_header_size >> 2);
3253 __TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3254
3255#ifdef CONFIG_TCP_MD5SIG
3256 /* Okay, we have all we need - do the md5 hash if needed */
3257 if (md5)
3258 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3259 md5, req_to_sk(req), skb);
3260 rcu_read_unlock();
3261#endif
3262
3263 /* Do not fool tcpdump (if any), clean our debris */
3264 skb->tstamp = 0;
3265 return skb;
3266}
3267EXPORT_SYMBOL(tcp_make_synack);
3268
3269static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
3270{
3271 struct inet_connection_sock *icsk = inet_csk(sk);
3272 const struct tcp_congestion_ops *ca;
3273 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
3274
3275 if (ca_key == TCP_CA_UNSPEC)
3276 return;
3277
3278 rcu_read_lock();
3279 ca = tcp_ca_find_key(ca_key);
3280 if (likely(ca && try_module_get(ca->owner))) {
3281 module_put(icsk->icsk_ca_ops->owner);
3282 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
3283 icsk->icsk_ca_ops = ca;
3284 }
3285 rcu_read_unlock();
3286}
3287
3288/* Do all connect socket setups that can be done AF independent. */
3289static void tcp_connect_init(struct sock *sk)
3290{
3291 const struct dst_entry *dst = __sk_dst_get(sk);
3292 struct tcp_sock *tp = tcp_sk(sk);
3293 __u8 rcv_wscale;
3294 u32 rcv_wnd;
3295
3296 /* We'll fix this up when we get a response from the other end.
3297 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3298 */
3299 tp->tcp_header_len = sizeof(struct tcphdr);
3300 if (sock_net(sk)->ipv4.sysctl_tcp_timestamps)
3301 tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
3302
3303#ifdef CONFIG_TCP_MD5SIG
3304 if (tp->af_specific->md5_lookup(sk, sk))
3305 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
3306#endif
3307
3308 /* If user gave his TCP_MAXSEG, record it to clamp */
3309 if (tp->rx_opt.user_mss)
3310 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3311 tp->max_window = 0;
3312 tcp_mtup_init(sk);
3313 tcp_sync_mss(sk, dst_mtu(dst));
3314
3315 tcp_ca_dst_init(sk, dst);
3316
3317 if (!tp->window_clamp)
3318 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3319 tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3320
3321 tcp_initialize_rcv_mss(sk);
3322
3323 /* limit the window selection if the user enforce a smaller rx buffer */
3324 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
3325 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
3326 tp->window_clamp = tcp_full_space(sk);
3327
3328 rcv_wnd = tcp_rwnd_init_bpf(sk);
3329 if (rcv_wnd == 0)
3330 rcv_wnd = dst_metric(dst, RTAX_INITRWND);
3331
3332 tcp_select_initial_window(sk, tcp_full_space(sk),
3333 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
3334 &tp->rcv_wnd,
3335 &tp->window_clamp,
3336 sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
3337 &rcv_wscale,
3338 rcv_wnd);
3339
3340 tp->rx_opt.rcv_wscale = rcv_wscale;
3341 tp->rcv_ssthresh = tp->rcv_wnd;
3342
3343 sk->sk_err = 0;
3344 sock_reset_flag(sk, SOCK_DONE);
3345 tp->snd_wnd = 0;
3346 tcp_init_wl(tp, 0);
3347 tcp_write_queue_purge(sk);
3348 tp->snd_una = tp->write_seq;
3349 tp->snd_sml = tp->write_seq;
3350 tp->snd_up = tp->write_seq;
3351 tp->snd_nxt = tp->write_seq;
3352
3353 if (likely(!tp->repair))
3354 tp->rcv_nxt = 0;
3355 else
3356 tp->rcv_tstamp = tcp_jiffies32;
3357 tp->rcv_wup = tp->rcv_nxt;
3358 tp->copied_seq = tp->rcv_nxt;
3359
3360 inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3361 inet_csk(sk)->icsk_retransmits = 0;
3362 tcp_clear_retrans(tp);
3363}
3364
3365static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
3366{
3367 struct tcp_sock *tp = tcp_sk(sk);
3368 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
3369
3370 tcb->end_seq += skb->len;
3371 __skb_header_release(skb);
3372 sk->sk_wmem_queued += skb->truesize;
3373 sk_mem_charge(sk, skb->truesize);
3374 tp->write_seq = tcb->end_seq;
3375 tp->packets_out += tcp_skb_pcount(skb);
3376}
3377
3378/* Build and send a SYN with data and (cached) Fast Open cookie. However,
3379 * queue a data-only packet after the regular SYN, such that regular SYNs
3380 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3381 * only the SYN sequence, the data are retransmitted in the first ACK.
3382 * If cookie is not cached or other error occurs, falls back to send a
3383 * regular SYN with Fast Open cookie request option.
3384 */
3385static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
3386{
3387 struct tcp_sock *tp = tcp_sk(sk);
3388 struct tcp_fastopen_request *fo = tp->fastopen_req;
3389 int space, err = 0;
3390 struct sk_buff *syn_data;
3391
3392 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
3393 if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3394 goto fallback;
3395
3396 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3397 * user-MSS. Reserve maximum option space for middleboxes that add
3398 * private TCP options. The cost is reduced data space in SYN :(
3399 */
3400 tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
3401
3402 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3403 MAX_TCP_OPTION_SPACE;
3404
3405 space = min_t(size_t, space, fo->size);
3406
3407 /* limit to order-0 allocations */
3408 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
3409
3410 syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3411 if (!syn_data)
3412 goto fallback;
3413 syn_data->ip_summed = CHECKSUM_PARTIAL;
3414 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3415 if (space) {
3416 int copied = copy_from_iter(skb_put(syn_data, space), space,
3417 &fo->data->msg_iter);
3418 if (unlikely(!copied)) {
3419 tcp_skb_tsorted_anchor_cleanup(syn_data);
3420 kfree_skb(syn_data);
3421 goto fallback;
3422 }
3423 if (copied != space) {
3424 skb_trim(syn_data, copied);
3425 space = copied;
3426 }
3427 }
3428 /* No more data pending in inet_wait_for_connect() */
3429 if (space == fo->size)
3430 fo->data = NULL;
3431 fo->copied = space;
3432
3433 tcp_connect_queue_skb(sk, syn_data);
3434 if (syn_data->len)
3435 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3436
3437 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3438
3439 syn->skb_mstamp = syn_data->skb_mstamp;
3440
3441 /* Now full SYN+DATA was cloned and sent (or not),
3442 * remove the SYN from the original skb (syn_data)
3443 * we keep in write queue in case of a retransmit, as we
3444 * also have the SYN packet (with no data) in the same queue.
3445 */
3446 TCP_SKB_CB(syn_data)->seq++;
3447 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
3448 if (!err) {
3449 tp->syn_data = (fo->copied > 0);
3450 tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
3451 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3452 goto done;
3453 }
3454
3455 /* data was not sent, put it in write_queue */
3456 __skb_queue_tail(&sk->sk_write_queue, syn_data);
3457 tp->packets_out -= tcp_skb_pcount(syn_data);
3458
3459fallback:
3460 /* Send a regular SYN with Fast Open cookie request option */
3461 if (fo->cookie.len > 0)
3462 fo->cookie.len = 0;
3463 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3464 if (err)
3465 tp->syn_fastopen = 0;
3466done:
3467 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3468 return err;
3469}
3470
3471/* Build a SYN and send it off. */
3472int tcp_connect(struct sock *sk)
3473{
3474 struct tcp_sock *tp = tcp_sk(sk);
3475 struct sk_buff *buff;
3476 int err;
3477
3478 tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
3479
3480 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3481 return -EHOSTUNREACH; /* Routing failure or similar. */
3482
3483 tcp_connect_init(sk);
3484
3485 if (unlikely(tp->repair)) {
3486 tcp_finish_connect(sk, NULL);
3487 return 0;
3488 }
3489
3490 buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3491 if (unlikely(!buff))
3492 return -ENOBUFS;
3493
3494 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3495 tcp_mstamp_refresh(tp);
3496 tp->retrans_stamp = tcp_time_stamp(tp);
3497 tcp_connect_queue_skb(sk, buff);
3498 tcp_ecn_send_syn(sk, buff);
3499 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
3500
3501 /* Send off SYN; include data in Fast Open. */
3502 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3503 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3504 if (err == -ECONNREFUSED)
3505 return err;
3506
3507 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3508 * in order to make this packet get counted in tcpOutSegs.
3509 */
3510 tp->snd_nxt = tp->write_seq;
3511 tp->pushed_seq = tp->write_seq;
3512 buff = tcp_send_head(sk);
3513 if (unlikely(buff)) {
3514 tp->snd_nxt = TCP_SKB_CB(buff)->seq;
3515 tp->pushed_seq = TCP_SKB_CB(buff)->seq;
3516 }
3517 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3518
3519 /* Timer for repeating the SYN until an answer. */
3520 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3521 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3522 return 0;
3523}
3524EXPORT_SYMBOL(tcp_connect);
3525
3526/* Send out a delayed ack, the caller does the policy checking
3527 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3528 * for details.
3529 */
3530void tcp_send_delayed_ack(struct sock *sk)
3531{
3532 struct inet_connection_sock *icsk = inet_csk(sk);
3533 int ato = icsk->icsk_ack.ato;
3534 unsigned long timeout;
3535
3536 tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);
3537
3538 if (ato > TCP_DELACK_MIN) {
3539 const struct tcp_sock *tp = tcp_sk(sk);
3540 int max_ato = HZ / 2;
3541
3542 if (icsk->icsk_ack.pingpong ||
3543 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3544 max_ato = TCP_DELACK_MAX;
3545
3546 /* Slow path, intersegment interval is "high". */
3547
3548 /* If some rtt estimate is known, use it to bound delayed ack.
3549 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3550 * directly.
3551 */
3552 if (tp->srtt_us) {
3553 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3554 TCP_DELACK_MIN);
3555
3556 if (rtt < max_ato)
3557 max_ato = rtt;
3558 }
3559
3560 ato = min(ato, max_ato);
3561 }
3562
3563 /* Stay within the limit we were given */
3564 timeout = jiffies + ato;
3565
3566 /* Use new timeout only if there wasn't a older one earlier. */
3567 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3568 /* If delack timer was blocked or is about to expire,
3569 * send ACK now.
3570 */
3571 if (icsk->icsk_ack.blocked ||
3572 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3573 tcp_send_ack(sk);
3574 return;
3575 }
3576
3577 if (!time_before(timeout, icsk->icsk_ack.timeout))
3578 timeout = icsk->icsk_ack.timeout;
3579 }
3580 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3581 icsk->icsk_ack.timeout = timeout;
3582 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3583}
3584
3585/* This routine sends an ack and also updates the window. */
3586void tcp_send_ack(struct sock *sk)
3587{
3588 struct sk_buff *buff;
3589
3590 /* If we have been reset, we may not send again. */
3591 if (sk->sk_state == TCP_CLOSE)
3592 return;
3593
3594 tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);
3595
3596 /* We are not putting this on the write queue, so
3597 * tcp_transmit_skb() will set the ownership to this
3598 * sock.
3599 */
3600 buff = alloc_skb(MAX_TCP_HEADER,
3601 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3602 if (unlikely(!buff)) {
3603 inet_csk_schedule_ack(sk);
3604 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
3605 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
3606 TCP_DELACK_MAX, TCP_RTO_MAX);
3607 return;
3608 }
3609
3610 /* Reserve space for headers and prepare control bits. */
3611 skb_reserve(buff, MAX_TCP_HEADER);
3612 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3613
3614 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
3615 * too much.
3616 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
3617 */
3618 skb_set_tcp_pure_ack(buff);
3619
3620 /* Send it off, this clears delayed acks for us. */
3621 tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
3622}
3623EXPORT_SYMBOL_GPL(tcp_send_ack);
3624
3625/* This routine sends a packet with an out of date sequence
3626 * number. It assumes the other end will try to ack it.
3627 *
3628 * Question: what should we make while urgent mode?
3629 * 4.4BSD forces sending single byte of data. We cannot send
3630 * out of window data, because we have SND.NXT==SND.MAX...
3631 *
3632 * Current solution: to send TWO zero-length segments in urgent mode:
3633 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3634 * out-of-date with SND.UNA-1 to probe window.
3635 */
3636static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
3637{
3638 struct tcp_sock *tp = tcp_sk(sk);
3639 struct sk_buff *skb;
3640
3641 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3642 skb = alloc_skb(MAX_TCP_HEADER,
3643 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3644 if (!skb)
3645 return -1;
3646
3647 /* Reserve space for headers and set control bits. */
3648 skb_reserve(skb, MAX_TCP_HEADER);
3649 /* Use a previous sequence. This should cause the other
3650 * end to send an ack. Don't queue or clone SKB, just
3651 * send it.
3652 */
3653 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3654 NET_INC_STATS(sock_net(sk), mib);
3655 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
3656}
3657
3658/* Called from setsockopt( ... TCP_REPAIR ) */
3659void tcp_send_window_probe(struct sock *sk)
3660{
3661 if (sk->sk_state == TCP_ESTABLISHED) {
3662 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3663 tcp_mstamp_refresh(tcp_sk(sk));
3664 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
3665 }
3666}
3667
3668/* Initiate keepalive or window probe from timer. */
3669int tcp_write_wakeup(struct sock *sk, int mib)
3670{
3671 struct tcp_sock *tp = tcp_sk(sk);
3672 struct sk_buff *skb;
3673
3674 if (sk->sk_state == TCP_CLOSE)
3675 return -1;
3676
3677 skb = tcp_send_head(sk);
3678 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3679 int err;
3680 unsigned int mss = tcp_current_mss(sk);
3681 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3682
3683 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
3684 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
3685
3686 /* We are probing the opening of a window
3687 * but the window size is != 0
3688 * must have been a result SWS avoidance ( sender )
3689 */
3690 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
3691 skb->len > mss) {
3692 seg_size = min(seg_size, mss);
3693 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3694 if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
3695 skb, seg_size, mss, GFP_ATOMIC))
3696 return -1;
3697 } else if (!tcp_skb_pcount(skb))
3698 tcp_set_skb_tso_segs(skb, mss);
3699
3700 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3701 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3702 if (!err)
3703 tcp_event_new_data_sent(sk, skb);
3704 return err;
3705 } else {
3706 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3707 tcp_xmit_probe_skb(sk, 1, mib);
3708 return tcp_xmit_probe_skb(sk, 0, mib);
3709 }
3710}
3711
3712/* A window probe timeout has occurred. If window is not closed send
3713 * a partial packet else a zero probe.
3714 */
3715void tcp_send_probe0(struct sock *sk)
3716{
3717 struct inet_connection_sock *icsk = inet_csk(sk);
3718 struct tcp_sock *tp = tcp_sk(sk);
3719 struct net *net = sock_net(sk);
3720 unsigned long probe_max;
3721 int err;
3722
3723 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
3724
3725 if (tp->packets_out || tcp_write_queue_empty(sk)) {
3726 /* Cancel probe timer, if it is not required. */
3727 icsk->icsk_probes_out = 0;
3728 icsk->icsk_backoff = 0;
3729 return;
3730 }
3731
3732 if (err <= 0) {
3733 if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3734 icsk->icsk_backoff++;
3735 icsk->icsk_probes_out++;
3736 probe_max = TCP_RTO_MAX;
3737 } else {
3738 /* If packet was not sent due to local congestion,
3739 * do not backoff and do not remember icsk_probes_out.
3740 * Let local senders to fight for local resources.
3741 *
3742 * Use accumulated backoff yet.
3743 */
3744 if (!icsk->icsk_probes_out)
3745 icsk->icsk_probes_out = 1;
3746 probe_max = TCP_RESOURCE_PROBE_INTERVAL;
3747 }
3748 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3749 tcp_probe0_when(sk, probe_max),
3750 TCP_RTO_MAX);
3751}
3752
3753int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3754{
3755 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
3756 struct flowi fl;
3757 int res;
3758
3759 tcp_rsk(req)->txhash = net_tx_rndhash();
3760 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3761 if (!res) {
3762 __TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3763 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3764 if (unlikely(tcp_passive_fastopen(sk)))
3765 tcp_sk(sk)->total_retrans++;
3766 trace_tcp_retransmit_synack(sk, req);
3767 }
3768 return res;
3769}
3770EXPORT_SYMBOL(tcp_rtx_synack);