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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// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * Implementation of the Transmission Control Protocol(TCP).
8 *
9 * Authors: Ross Biro
10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 * Mark Evans, <evansmp@uhura.aston.ac.uk>
12 * Corey Minyard <wf-rch!minyard@relay.EU.net>
13 * Florian La Roche, <flla@stud.uni-sb.de>
14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
15 * Linus Torvalds, <torvalds@cs.helsinki.fi>
16 * Alan Cox, <gw4pts@gw4pts.ampr.org>
17 * Matthew Dillon, <dillon@apollo.west.oic.com>
18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
19 * Jorge Cwik, <jorge@laser.satlink.net>
20 */
21
22/*
23 * Changes: Pedro Roque : Retransmit queue handled by TCP.
24 * : Fragmentation on mtu decrease
25 * : Segment collapse on retransmit
26 * : AF independence
27 *
28 * Linus Torvalds : send_delayed_ack
29 * David S. Miller : Charge memory using the right skb
30 * during syn/ack processing.
31 * David S. Miller : Output engine completely rewritten.
32 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
33 * Cacophonix Gaul : draft-minshall-nagle-01
34 * J Hadi Salim : ECN support
35 *
36 */
37
38#define pr_fmt(fmt) "TCP: " fmt
39
40#include <net/tcp.h>
41#include <net/mptcp.h>
42#include <net/proto_memory.h>
43
44#include <linux/compiler.h>
45#include <linux/gfp.h>
46#include <linux/module.h>
47#include <linux/static_key.h>
48#include <linux/skbuff_ref.h>
49
50#include <trace/events/tcp.h>
51
52/* Refresh clocks of a TCP socket,
53 * ensuring monotically increasing values.
54 */
55void tcp_mstamp_refresh(struct tcp_sock *tp)
56{
57 u64 val = tcp_clock_ns();
58
59 tp->tcp_clock_cache = val;
60 tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
61}
62
63static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
64 int push_one, gfp_t gfp);
65
66/* Account for new data that has been sent to the network. */
67static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
68{
69 struct inet_connection_sock *icsk = inet_csk(sk);
70 struct tcp_sock *tp = tcp_sk(sk);
71 unsigned int prior_packets = tp->packets_out;
72
73 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
74
75 __skb_unlink(skb, &sk->sk_write_queue);
76 tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
77
78 if (tp->highest_sack == NULL)
79 tp->highest_sack = skb;
80
81 tp->packets_out += tcp_skb_pcount(skb);
82 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
83 tcp_rearm_rto(sk);
84
85 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
86 tcp_skb_pcount(skb));
87 tcp_check_space(sk);
88}
89
90/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
91 * window scaling factor due to loss of precision.
92 * If window has been shrunk, what should we make? It is not clear at all.
93 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
94 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
95 * invalid. OK, let's make this for now:
96 */
97static inline __u32 tcp_acceptable_seq(const struct sock *sk)
98{
99 const struct tcp_sock *tp = tcp_sk(sk);
100
101 if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
102 (tp->rx_opt.wscale_ok &&
103 ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
104 return tp->snd_nxt;
105 else
106 return tcp_wnd_end(tp);
107}
108
109/* Calculate mss to advertise in SYN segment.
110 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
111 *
112 * 1. It is independent of path mtu.
113 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
114 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
115 * attached devices, because some buggy hosts are confused by
116 * large MSS.
117 * 4. We do not make 3, we advertise MSS, calculated from first
118 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
119 * This may be overridden via information stored in routing table.
120 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
121 * probably even Jumbo".
122 */
123static __u16 tcp_advertise_mss(struct sock *sk)
124{
125 struct tcp_sock *tp = tcp_sk(sk);
126 const struct dst_entry *dst = __sk_dst_get(sk);
127 int mss = tp->advmss;
128
129 if (dst) {
130 unsigned int metric = dst_metric_advmss(dst);
131
132 if (metric < mss) {
133 mss = metric;
134 tp->advmss = mss;
135 }
136 }
137
138 return (__u16)mss;
139}
140
141/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
142 * This is the first part of cwnd validation mechanism.
143 */
144void tcp_cwnd_restart(struct sock *sk, s32 delta)
145{
146 struct tcp_sock *tp = tcp_sk(sk);
147 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
148 u32 cwnd = tcp_snd_cwnd(tp);
149
150 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
151
152 tp->snd_ssthresh = tcp_current_ssthresh(sk);
153 restart_cwnd = min(restart_cwnd, cwnd);
154
155 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
156 cwnd >>= 1;
157 tcp_snd_cwnd_set(tp, max(cwnd, restart_cwnd));
158 tp->snd_cwnd_stamp = tcp_jiffies32;
159 tp->snd_cwnd_used = 0;
160}
161
162/* Congestion state accounting after a packet has been sent. */
163static void tcp_event_data_sent(struct tcp_sock *tp,
164 struct sock *sk)
165{
166 struct inet_connection_sock *icsk = inet_csk(sk);
167 const u32 now = tcp_jiffies32;
168
169 if (tcp_packets_in_flight(tp) == 0)
170 tcp_ca_event(sk, CA_EVENT_TX_START);
171
172 tp->lsndtime = now;
173
174 /* If it is a reply for ato after last received
175 * packet, increase pingpong count.
176 */
177 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
178 inet_csk_inc_pingpong_cnt(sk);
179}
180
181/* Account for an ACK we sent. */
182static inline void tcp_event_ack_sent(struct sock *sk, u32 rcv_nxt)
183{
184 struct tcp_sock *tp = tcp_sk(sk);
185
186 if (unlikely(tp->compressed_ack)) {
187 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
188 tp->compressed_ack);
189 tp->compressed_ack = 0;
190 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
191 __sock_put(sk);
192 }
193
194 if (unlikely(rcv_nxt != tp->rcv_nxt))
195 return; /* Special ACK sent by DCTCP to reflect ECN */
196 tcp_dec_quickack_mode(sk);
197 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
198}
199
200/* Determine a window scaling and initial window to offer.
201 * Based on the assumption that the given amount of space
202 * will be offered. Store the results in the tp structure.
203 * NOTE: for smooth operation initial space offering should
204 * be a multiple of mss if possible. We assume here that mss >= 1.
205 * This MUST be enforced by all callers.
206 */
207void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
208 __u32 *rcv_wnd, __u32 *__window_clamp,
209 int wscale_ok, __u8 *rcv_wscale,
210 __u32 init_rcv_wnd)
211{
212 unsigned int space = (__space < 0 ? 0 : __space);
213 u32 window_clamp = READ_ONCE(*__window_clamp);
214
215 /* If no clamp set the clamp to the max possible scaled window */
216 if (window_clamp == 0)
217 window_clamp = (U16_MAX << TCP_MAX_WSCALE);
218 space = min(window_clamp, space);
219
220 /* Quantize space offering to a multiple of mss if possible. */
221 if (space > mss)
222 space = rounddown(space, mss);
223
224 /* NOTE: offering an initial window larger than 32767
225 * will break some buggy TCP stacks. If the admin tells us
226 * it is likely we could be speaking with such a buggy stack
227 * we will truncate our initial window offering to 32K-1
228 * unless the remote has sent us a window scaling option,
229 * which we interpret as a sign the remote TCP is not
230 * misinterpreting the window field as a signed quantity.
231 */
232 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows))
233 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
234 else
235 (*rcv_wnd) = space;
236
237 if (init_rcv_wnd)
238 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
239
240 *rcv_wscale = 0;
241 if (wscale_ok) {
242 /* Set window scaling on max possible window */
243 space = max_t(u32, space, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]));
244 space = max_t(u32, space, READ_ONCE(sysctl_rmem_max));
245 space = min_t(u32, space, window_clamp);
246 *rcv_wscale = clamp_t(int, ilog2(space) - 15,
247 0, TCP_MAX_WSCALE);
248 }
249 /* Set the clamp no higher than max representable value */
250 WRITE_ONCE(*__window_clamp,
251 min_t(__u32, U16_MAX << (*rcv_wscale), window_clamp));
252}
253EXPORT_SYMBOL(tcp_select_initial_window);
254
255/* Chose a new window to advertise, update state in tcp_sock for the
256 * socket, and return result with RFC1323 scaling applied. The return
257 * value can be stuffed directly into th->window for an outgoing
258 * frame.
259 */
260static u16 tcp_select_window(struct sock *sk)
261{
262 struct tcp_sock *tp = tcp_sk(sk);
263 struct net *net = sock_net(sk);
264 u32 old_win = tp->rcv_wnd;
265 u32 cur_win, new_win;
266
267 /* Make the window 0 if we failed to queue the data because we
268 * are out of memory.
269 */
270 if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM)) {
271 tp->pred_flags = 0;
272 tp->rcv_wnd = 0;
273 tp->rcv_wup = tp->rcv_nxt;
274 return 0;
275 }
276
277 cur_win = tcp_receive_window(tp);
278 new_win = __tcp_select_window(sk);
279 if (new_win < cur_win) {
280 /* Danger Will Robinson!
281 * Don't update rcv_wup/rcv_wnd here or else
282 * we will not be able to advertise a zero
283 * window in time. --DaveM
284 *
285 * Relax Will Robinson.
286 */
287 if (!READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) || !tp->rx_opt.rcv_wscale) {
288 /* Never shrink the offered window */
289 if (new_win == 0)
290 NET_INC_STATS(net, LINUX_MIB_TCPWANTZEROWINDOWADV);
291 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
292 }
293 }
294
295 tp->rcv_wnd = new_win;
296 tp->rcv_wup = tp->rcv_nxt;
297
298 /* Make sure we do not exceed the maximum possible
299 * scaled window.
300 */
301 if (!tp->rx_opt.rcv_wscale &&
302 READ_ONCE(net->ipv4.sysctl_tcp_workaround_signed_windows))
303 new_win = min(new_win, MAX_TCP_WINDOW);
304 else
305 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
306
307 /* RFC1323 scaling applied */
308 new_win >>= tp->rx_opt.rcv_wscale;
309
310 /* If we advertise zero window, disable fast path. */
311 if (new_win == 0) {
312 tp->pred_flags = 0;
313 if (old_win)
314 NET_INC_STATS(net, LINUX_MIB_TCPTOZEROWINDOWADV);
315 } else if (old_win == 0) {
316 NET_INC_STATS(net, LINUX_MIB_TCPFROMZEROWINDOWADV);
317 }
318
319 return new_win;
320}
321
322/* Packet ECN state for a SYN-ACK */
323static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
324{
325 const struct tcp_sock *tp = tcp_sk(sk);
326
327 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
328 if (!(tp->ecn_flags & TCP_ECN_OK))
329 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
330 else if (tcp_ca_needs_ecn(sk) ||
331 tcp_bpf_ca_needs_ecn(sk))
332 INET_ECN_xmit(sk);
333}
334
335/* Packet ECN state for a SYN. */
336static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
337{
338 struct tcp_sock *tp = tcp_sk(sk);
339 bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
340 bool use_ecn = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn) == 1 ||
341 tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
342
343 if (!use_ecn) {
344 const struct dst_entry *dst = __sk_dst_get(sk);
345
346 if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
347 use_ecn = true;
348 }
349
350 tp->ecn_flags = 0;
351
352 if (use_ecn) {
353 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
354 tp->ecn_flags = TCP_ECN_OK;
355 if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
356 INET_ECN_xmit(sk);
357 }
358}
359
360static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
361{
362 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback))
363 /* tp->ecn_flags are cleared at a later point in time when
364 * SYN ACK is ultimatively being received.
365 */
366 TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
367}
368
369static void
370tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
371{
372 if (inet_rsk(req)->ecn_ok)
373 th->ece = 1;
374}
375
376/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
377 * be sent.
378 */
379static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
380 struct tcphdr *th, int tcp_header_len)
381{
382 struct tcp_sock *tp = tcp_sk(sk);
383
384 if (tp->ecn_flags & TCP_ECN_OK) {
385 /* Not-retransmitted data segment: set ECT and inject CWR. */
386 if (skb->len != tcp_header_len &&
387 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
388 INET_ECN_xmit(sk);
389 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
390 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
391 th->cwr = 1;
392 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
393 }
394 } else if (!tcp_ca_needs_ecn(sk)) {
395 /* ACK or retransmitted segment: clear ECT|CE */
396 INET_ECN_dontxmit(sk);
397 }
398 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
399 th->ece = 1;
400 }
401}
402
403/* Constructs common control bits of non-data skb. If SYN/FIN is present,
404 * auto increment end seqno.
405 */
406static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
407{
408 skb->ip_summed = CHECKSUM_PARTIAL;
409
410 TCP_SKB_CB(skb)->tcp_flags = flags;
411
412 tcp_skb_pcount_set(skb, 1);
413
414 TCP_SKB_CB(skb)->seq = seq;
415 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
416 seq++;
417 TCP_SKB_CB(skb)->end_seq = seq;
418}
419
420static inline bool tcp_urg_mode(const struct tcp_sock *tp)
421{
422 return tp->snd_una != tp->snd_up;
423}
424
425#define OPTION_SACK_ADVERTISE BIT(0)
426#define OPTION_TS BIT(1)
427#define OPTION_MD5 BIT(2)
428#define OPTION_WSCALE BIT(3)
429#define OPTION_FAST_OPEN_COOKIE BIT(8)
430#define OPTION_SMC BIT(9)
431#define OPTION_MPTCP BIT(10)
432#define OPTION_AO BIT(11)
433
434static void smc_options_write(__be32 *ptr, u16 *options)
435{
436#if IS_ENABLED(CONFIG_SMC)
437 if (static_branch_unlikely(&tcp_have_smc)) {
438 if (unlikely(OPTION_SMC & *options)) {
439 *ptr++ = htonl((TCPOPT_NOP << 24) |
440 (TCPOPT_NOP << 16) |
441 (TCPOPT_EXP << 8) |
442 (TCPOLEN_EXP_SMC_BASE));
443 *ptr++ = htonl(TCPOPT_SMC_MAGIC);
444 }
445 }
446#endif
447}
448
449struct tcp_out_options {
450 u16 options; /* bit field of OPTION_* */
451 u16 mss; /* 0 to disable */
452 u8 ws; /* window scale, 0 to disable */
453 u8 num_sack_blocks; /* number of SACK blocks to include */
454 u8 hash_size; /* bytes in hash_location */
455 u8 bpf_opt_len; /* length of BPF hdr option */
456 __u8 *hash_location; /* temporary pointer, overloaded */
457 __u32 tsval, tsecr; /* need to include OPTION_TS */
458 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
459 struct mptcp_out_options mptcp;
460};
461
462static void mptcp_options_write(struct tcphdr *th, __be32 *ptr,
463 struct tcp_sock *tp,
464 struct tcp_out_options *opts)
465{
466#if IS_ENABLED(CONFIG_MPTCP)
467 if (unlikely(OPTION_MPTCP & opts->options))
468 mptcp_write_options(th, ptr, tp, &opts->mptcp);
469#endif
470}
471
472#ifdef CONFIG_CGROUP_BPF
473static int bpf_skops_write_hdr_opt_arg0(struct sk_buff *skb,
474 enum tcp_synack_type synack_type)
475{
476 if (unlikely(!skb))
477 return BPF_WRITE_HDR_TCP_CURRENT_MSS;
478
479 if (unlikely(synack_type == TCP_SYNACK_COOKIE))
480 return BPF_WRITE_HDR_TCP_SYNACK_COOKIE;
481
482 return 0;
483}
484
485/* req, syn_skb and synack_type are used when writing synack */
486static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
487 struct request_sock *req,
488 struct sk_buff *syn_skb,
489 enum tcp_synack_type synack_type,
490 struct tcp_out_options *opts,
491 unsigned int *remaining)
492{
493 struct bpf_sock_ops_kern sock_ops;
494 int err;
495
496 if (likely(!BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk),
497 BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG)) ||
498 !*remaining)
499 return;
500
501 /* *remaining has already been aligned to 4 bytes, so *remaining >= 4 */
502
503 /* init sock_ops */
504 memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
505
506 sock_ops.op = BPF_SOCK_OPS_HDR_OPT_LEN_CB;
507
508 if (req) {
509 /* The listen "sk" cannot be passed here because
510 * it is not locked. It would not make too much
511 * sense to do bpf_setsockopt(listen_sk) based
512 * on individual connection request also.
513 *
514 * Thus, "req" is passed here and the cgroup-bpf-progs
515 * of the listen "sk" will be run.
516 *
517 * "req" is also used here for fastopen even the "sk" here is
518 * a fullsock "child" sk. It is to keep the behavior
519 * consistent between fastopen and non-fastopen on
520 * the bpf programming side.
521 */
522 sock_ops.sk = (struct sock *)req;
523 sock_ops.syn_skb = syn_skb;
524 } else {
525 sock_owned_by_me(sk);
526
527 sock_ops.is_fullsock = 1;
528 sock_ops.sk = sk;
529 }
530
531 sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
532 sock_ops.remaining_opt_len = *remaining;
533 /* tcp_current_mss() does not pass a skb */
534 if (skb)
535 bpf_skops_init_skb(&sock_ops, skb, 0);
536
537 err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
538
539 if (err || sock_ops.remaining_opt_len == *remaining)
540 return;
541
542 opts->bpf_opt_len = *remaining - sock_ops.remaining_opt_len;
543 /* round up to 4 bytes */
544 opts->bpf_opt_len = (opts->bpf_opt_len + 3) & ~3;
545
546 *remaining -= opts->bpf_opt_len;
547}
548
549static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
550 struct request_sock *req,
551 struct sk_buff *syn_skb,
552 enum tcp_synack_type synack_type,
553 struct tcp_out_options *opts)
554{
555 u8 first_opt_off, nr_written, max_opt_len = opts->bpf_opt_len;
556 struct bpf_sock_ops_kern sock_ops;
557 int err;
558
559 if (likely(!max_opt_len))
560 return;
561
562 memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
563
564 sock_ops.op = BPF_SOCK_OPS_WRITE_HDR_OPT_CB;
565
566 if (req) {
567 sock_ops.sk = (struct sock *)req;
568 sock_ops.syn_skb = syn_skb;
569 } else {
570 sock_owned_by_me(sk);
571
572 sock_ops.is_fullsock = 1;
573 sock_ops.sk = sk;
574 }
575
576 sock_ops.args[0] = bpf_skops_write_hdr_opt_arg0(skb, synack_type);
577 sock_ops.remaining_opt_len = max_opt_len;
578 first_opt_off = tcp_hdrlen(skb) - max_opt_len;
579 bpf_skops_init_skb(&sock_ops, skb, first_opt_off);
580
581 err = BPF_CGROUP_RUN_PROG_SOCK_OPS_SK(&sock_ops, sk);
582
583 if (err)
584 nr_written = 0;
585 else
586 nr_written = max_opt_len - sock_ops.remaining_opt_len;
587
588 if (nr_written < max_opt_len)
589 memset(skb->data + first_opt_off + nr_written, TCPOPT_NOP,
590 max_opt_len - nr_written);
591}
592#else
593static void bpf_skops_hdr_opt_len(struct sock *sk, struct sk_buff *skb,
594 struct request_sock *req,
595 struct sk_buff *syn_skb,
596 enum tcp_synack_type synack_type,
597 struct tcp_out_options *opts,
598 unsigned int *remaining)
599{
600}
601
602static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
603 struct request_sock *req,
604 struct sk_buff *syn_skb,
605 enum tcp_synack_type synack_type,
606 struct tcp_out_options *opts)
607{
608}
609#endif
610
611static __be32 *process_tcp_ao_options(struct tcp_sock *tp,
612 const struct tcp_request_sock *tcprsk,
613 struct tcp_out_options *opts,
614 struct tcp_key *key, __be32 *ptr)
615{
616#ifdef CONFIG_TCP_AO
617 u8 maclen = tcp_ao_maclen(key->ao_key);
618
619 if (tcprsk) {
620 u8 aolen = maclen + sizeof(struct tcp_ao_hdr);
621
622 *ptr++ = htonl((TCPOPT_AO << 24) | (aolen << 16) |
623 (tcprsk->ao_keyid << 8) |
624 (tcprsk->ao_rcv_next));
625 } else {
626 struct tcp_ao_key *rnext_key;
627 struct tcp_ao_info *ao_info;
628
629 ao_info = rcu_dereference_check(tp->ao_info,
630 lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk));
631 rnext_key = READ_ONCE(ao_info->rnext_key);
632 if (WARN_ON_ONCE(!rnext_key))
633 return ptr;
634 *ptr++ = htonl((TCPOPT_AO << 24) |
635 (tcp_ao_len(key->ao_key) << 16) |
636 (key->ao_key->sndid << 8) |
637 (rnext_key->rcvid));
638 }
639 opts->hash_location = (__u8 *)ptr;
640 ptr += maclen / sizeof(*ptr);
641 if (unlikely(maclen % sizeof(*ptr))) {
642 memset(ptr, TCPOPT_NOP, sizeof(*ptr));
643 ptr++;
644 }
645#endif
646 return ptr;
647}
648
649/* Write previously computed TCP options to the packet.
650 *
651 * Beware: Something in the Internet is very sensitive to the ordering of
652 * TCP options, we learned this through the hard way, so be careful here.
653 * Luckily we can at least blame others for their non-compliance but from
654 * inter-operability perspective it seems that we're somewhat stuck with
655 * the ordering which we have been using if we want to keep working with
656 * those broken things (not that it currently hurts anybody as there isn't
657 * particular reason why the ordering would need to be changed).
658 *
659 * At least SACK_PERM as the first option is known to lead to a disaster
660 * (but it may well be that other scenarios fail similarly).
661 */
662static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
663 const struct tcp_request_sock *tcprsk,
664 struct tcp_out_options *opts,
665 struct tcp_key *key)
666{
667 __be32 *ptr = (__be32 *)(th + 1);
668 u16 options = opts->options; /* mungable copy */
669
670 if (tcp_key_is_md5(key)) {
671 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
672 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
673 /* overload cookie hash location */
674 opts->hash_location = (__u8 *)ptr;
675 ptr += 4;
676 } else if (tcp_key_is_ao(key)) {
677 ptr = process_tcp_ao_options(tp, tcprsk, opts, key, ptr);
678 }
679 if (unlikely(opts->mss)) {
680 *ptr++ = htonl((TCPOPT_MSS << 24) |
681 (TCPOLEN_MSS << 16) |
682 opts->mss);
683 }
684
685 if (likely(OPTION_TS & options)) {
686 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
687 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
688 (TCPOLEN_SACK_PERM << 16) |
689 (TCPOPT_TIMESTAMP << 8) |
690 TCPOLEN_TIMESTAMP);
691 options &= ~OPTION_SACK_ADVERTISE;
692 } else {
693 *ptr++ = htonl((TCPOPT_NOP << 24) |
694 (TCPOPT_NOP << 16) |
695 (TCPOPT_TIMESTAMP << 8) |
696 TCPOLEN_TIMESTAMP);
697 }
698 *ptr++ = htonl(opts->tsval);
699 *ptr++ = htonl(opts->tsecr);
700 }
701
702 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
703 *ptr++ = htonl((TCPOPT_NOP << 24) |
704 (TCPOPT_NOP << 16) |
705 (TCPOPT_SACK_PERM << 8) |
706 TCPOLEN_SACK_PERM);
707 }
708
709 if (unlikely(OPTION_WSCALE & options)) {
710 *ptr++ = htonl((TCPOPT_NOP << 24) |
711 (TCPOPT_WINDOW << 16) |
712 (TCPOLEN_WINDOW << 8) |
713 opts->ws);
714 }
715
716 if (unlikely(opts->num_sack_blocks)) {
717 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
718 tp->duplicate_sack : tp->selective_acks;
719 int this_sack;
720
721 *ptr++ = htonl((TCPOPT_NOP << 24) |
722 (TCPOPT_NOP << 16) |
723 (TCPOPT_SACK << 8) |
724 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
725 TCPOLEN_SACK_PERBLOCK)));
726
727 for (this_sack = 0; this_sack < opts->num_sack_blocks;
728 ++this_sack) {
729 *ptr++ = htonl(sp[this_sack].start_seq);
730 *ptr++ = htonl(sp[this_sack].end_seq);
731 }
732
733 tp->rx_opt.dsack = 0;
734 }
735
736 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
737 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
738 u8 *p = (u8 *)ptr;
739 u32 len; /* Fast Open option length */
740
741 if (foc->exp) {
742 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
743 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
744 TCPOPT_FASTOPEN_MAGIC);
745 p += TCPOLEN_EXP_FASTOPEN_BASE;
746 } else {
747 len = TCPOLEN_FASTOPEN_BASE + foc->len;
748 *p++ = TCPOPT_FASTOPEN;
749 *p++ = len;
750 }
751
752 memcpy(p, foc->val, foc->len);
753 if ((len & 3) == 2) {
754 p[foc->len] = TCPOPT_NOP;
755 p[foc->len + 1] = TCPOPT_NOP;
756 }
757 ptr += (len + 3) >> 2;
758 }
759
760 smc_options_write(ptr, &options);
761
762 mptcp_options_write(th, ptr, tp, opts);
763}
764
765static void smc_set_option(const struct tcp_sock *tp,
766 struct tcp_out_options *opts,
767 unsigned int *remaining)
768{
769#if IS_ENABLED(CONFIG_SMC)
770 if (static_branch_unlikely(&tcp_have_smc)) {
771 if (tp->syn_smc) {
772 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
773 opts->options |= OPTION_SMC;
774 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
775 }
776 }
777 }
778#endif
779}
780
781static void smc_set_option_cond(const struct tcp_sock *tp,
782 const struct inet_request_sock *ireq,
783 struct tcp_out_options *opts,
784 unsigned int *remaining)
785{
786#if IS_ENABLED(CONFIG_SMC)
787 if (static_branch_unlikely(&tcp_have_smc)) {
788 if (tp->syn_smc && ireq->smc_ok) {
789 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
790 opts->options |= OPTION_SMC;
791 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
792 }
793 }
794 }
795#endif
796}
797
798static void mptcp_set_option_cond(const struct request_sock *req,
799 struct tcp_out_options *opts,
800 unsigned int *remaining)
801{
802 if (rsk_is_mptcp(req)) {
803 unsigned int size;
804
805 if (mptcp_synack_options(req, &size, &opts->mptcp)) {
806 if (*remaining >= size) {
807 opts->options |= OPTION_MPTCP;
808 *remaining -= size;
809 }
810 }
811 }
812}
813
814/* Compute TCP options for SYN packets. This is not the final
815 * network wire format yet.
816 */
817static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
818 struct tcp_out_options *opts,
819 struct tcp_key *key)
820{
821 struct tcp_sock *tp = tcp_sk(sk);
822 unsigned int remaining = MAX_TCP_OPTION_SPACE;
823 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
824 bool timestamps;
825
826 /* Better than switch (key.type) as it has static branches */
827 if (tcp_key_is_md5(key)) {
828 timestamps = false;
829 opts->options |= OPTION_MD5;
830 remaining -= TCPOLEN_MD5SIG_ALIGNED;
831 } else {
832 timestamps = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps);
833 if (tcp_key_is_ao(key)) {
834 opts->options |= OPTION_AO;
835 remaining -= tcp_ao_len_aligned(key->ao_key);
836 }
837 }
838
839 /* We always get an MSS option. The option bytes which will be seen in
840 * normal data packets should timestamps be used, must be in the MSS
841 * advertised. But we subtract them from tp->mss_cache so that
842 * calculations in tcp_sendmsg are simpler etc. So account for this
843 * fact here if necessary. If we don't do this correctly, as a
844 * receiver we won't recognize data packets as being full sized when we
845 * should, and thus we won't abide by the delayed ACK rules correctly.
846 * SACKs don't matter, we never delay an ACK when we have any of those
847 * going out. */
848 opts->mss = tcp_advertise_mss(sk);
849 remaining -= TCPOLEN_MSS_ALIGNED;
850
851 if (likely(timestamps)) {
852 opts->options |= OPTION_TS;
853 opts->tsval = tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb) + tp->tsoffset;
854 opts->tsecr = tp->rx_opt.ts_recent;
855 remaining -= TCPOLEN_TSTAMP_ALIGNED;
856 }
857 if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_window_scaling))) {
858 opts->ws = tp->rx_opt.rcv_wscale;
859 opts->options |= OPTION_WSCALE;
860 remaining -= TCPOLEN_WSCALE_ALIGNED;
861 }
862 if (likely(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_sack))) {
863 opts->options |= OPTION_SACK_ADVERTISE;
864 if (unlikely(!(OPTION_TS & opts->options)))
865 remaining -= TCPOLEN_SACKPERM_ALIGNED;
866 }
867
868 if (fastopen && fastopen->cookie.len >= 0) {
869 u32 need = fastopen->cookie.len;
870
871 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
872 TCPOLEN_FASTOPEN_BASE;
873 need = (need + 3) & ~3U; /* Align to 32 bits */
874 if (remaining >= need) {
875 opts->options |= OPTION_FAST_OPEN_COOKIE;
876 opts->fastopen_cookie = &fastopen->cookie;
877 remaining -= need;
878 tp->syn_fastopen = 1;
879 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
880 }
881 }
882
883 smc_set_option(tp, opts, &remaining);
884
885 if (sk_is_mptcp(sk)) {
886 unsigned int size;
887
888 if (mptcp_syn_options(sk, skb, &size, &opts->mptcp)) {
889 if (remaining >= size) {
890 opts->options |= OPTION_MPTCP;
891 remaining -= size;
892 }
893 }
894 }
895
896 bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
897
898 return MAX_TCP_OPTION_SPACE - remaining;
899}
900
901/* Set up TCP options for SYN-ACKs. */
902static unsigned int tcp_synack_options(const struct sock *sk,
903 struct request_sock *req,
904 unsigned int mss, struct sk_buff *skb,
905 struct tcp_out_options *opts,
906 const struct tcp_key *key,
907 struct tcp_fastopen_cookie *foc,
908 enum tcp_synack_type synack_type,
909 struct sk_buff *syn_skb)
910{
911 struct inet_request_sock *ireq = inet_rsk(req);
912 unsigned int remaining = MAX_TCP_OPTION_SPACE;
913
914 if (tcp_key_is_md5(key)) {
915 opts->options |= OPTION_MD5;
916 remaining -= TCPOLEN_MD5SIG_ALIGNED;
917
918 /* We can't fit any SACK blocks in a packet with MD5 + TS
919 * options. There was discussion about disabling SACK
920 * rather than TS in order to fit in better with old,
921 * buggy kernels, but that was deemed to be unnecessary.
922 */
923 if (synack_type != TCP_SYNACK_COOKIE)
924 ireq->tstamp_ok &= !ireq->sack_ok;
925 } else if (tcp_key_is_ao(key)) {
926 opts->options |= OPTION_AO;
927 remaining -= tcp_ao_len_aligned(key->ao_key);
928 ireq->tstamp_ok &= !ireq->sack_ok;
929 }
930
931 /* We always send an MSS option. */
932 opts->mss = mss;
933 remaining -= TCPOLEN_MSS_ALIGNED;
934
935 if (likely(ireq->wscale_ok)) {
936 opts->ws = ireq->rcv_wscale;
937 opts->options |= OPTION_WSCALE;
938 remaining -= TCPOLEN_WSCALE_ALIGNED;
939 }
940 if (likely(ireq->tstamp_ok)) {
941 opts->options |= OPTION_TS;
942 opts->tsval = tcp_skb_timestamp_ts(tcp_rsk(req)->req_usec_ts, skb) +
943 tcp_rsk(req)->ts_off;
944 opts->tsecr = READ_ONCE(req->ts_recent);
945 remaining -= TCPOLEN_TSTAMP_ALIGNED;
946 }
947 if (likely(ireq->sack_ok)) {
948 opts->options |= OPTION_SACK_ADVERTISE;
949 if (unlikely(!ireq->tstamp_ok))
950 remaining -= TCPOLEN_SACKPERM_ALIGNED;
951 }
952 if (foc != NULL && foc->len >= 0) {
953 u32 need = foc->len;
954
955 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
956 TCPOLEN_FASTOPEN_BASE;
957 need = (need + 3) & ~3U; /* Align to 32 bits */
958 if (remaining >= need) {
959 opts->options |= OPTION_FAST_OPEN_COOKIE;
960 opts->fastopen_cookie = foc;
961 remaining -= need;
962 }
963 }
964
965 mptcp_set_option_cond(req, opts, &remaining);
966
967 smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
968
969 bpf_skops_hdr_opt_len((struct sock *)sk, skb, req, syn_skb,
970 synack_type, opts, &remaining);
971
972 return MAX_TCP_OPTION_SPACE - remaining;
973}
974
975/* Compute TCP options for ESTABLISHED sockets. This is not the
976 * final wire format yet.
977 */
978static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
979 struct tcp_out_options *opts,
980 struct tcp_key *key)
981{
982 struct tcp_sock *tp = tcp_sk(sk);
983 unsigned int size = 0;
984 unsigned int eff_sacks;
985
986 opts->options = 0;
987
988 /* Better than switch (key.type) as it has static branches */
989 if (tcp_key_is_md5(key)) {
990 opts->options |= OPTION_MD5;
991 size += TCPOLEN_MD5SIG_ALIGNED;
992 } else if (tcp_key_is_ao(key)) {
993 opts->options |= OPTION_AO;
994 size += tcp_ao_len_aligned(key->ao_key);
995 }
996
997 if (likely(tp->rx_opt.tstamp_ok)) {
998 opts->options |= OPTION_TS;
999 opts->tsval = skb ? tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb) +
1000 tp->tsoffset : 0;
1001 opts->tsecr = tp->rx_opt.ts_recent;
1002 size += TCPOLEN_TSTAMP_ALIGNED;
1003 }
1004
1005 /* MPTCP options have precedence over SACK for the limited TCP
1006 * option space because a MPTCP connection would be forced to
1007 * fall back to regular TCP if a required multipath option is
1008 * missing. SACK still gets a chance to use whatever space is
1009 * left.
1010 */
1011 if (sk_is_mptcp(sk)) {
1012 unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1013 unsigned int opt_size = 0;
1014
1015 if (mptcp_established_options(sk, skb, &opt_size, remaining,
1016 &opts->mptcp)) {
1017 opts->options |= OPTION_MPTCP;
1018 size += opt_size;
1019 }
1020 }
1021
1022 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
1023 if (unlikely(eff_sacks)) {
1024 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1025 if (unlikely(remaining < TCPOLEN_SACK_BASE_ALIGNED +
1026 TCPOLEN_SACK_PERBLOCK))
1027 return size;
1028
1029 opts->num_sack_blocks =
1030 min_t(unsigned int, eff_sacks,
1031 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
1032 TCPOLEN_SACK_PERBLOCK);
1033
1034 size += TCPOLEN_SACK_BASE_ALIGNED +
1035 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
1036 }
1037
1038 if (unlikely(BPF_SOCK_OPS_TEST_FLAG(tp,
1039 BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG))) {
1040 unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
1041
1042 bpf_skops_hdr_opt_len(sk, skb, NULL, NULL, 0, opts, &remaining);
1043
1044 size = MAX_TCP_OPTION_SPACE - remaining;
1045 }
1046
1047 return size;
1048}
1049
1050
1051/* TCP SMALL QUEUES (TSQ)
1052 *
1053 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
1054 * to reduce RTT and bufferbloat.
1055 * We do this using a special skb destructor (tcp_wfree).
1056 *
1057 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
1058 * needs to be reallocated in a driver.
1059 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
1060 *
1061 * Since transmit from skb destructor is forbidden, we use a tasklet
1062 * to process all sockets that eventually need to send more skbs.
1063 * We use one tasklet per cpu, with its own queue of sockets.
1064 */
1065struct tsq_tasklet {
1066 struct tasklet_struct tasklet;
1067 struct list_head head; /* queue of tcp sockets */
1068};
1069static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
1070
1071static void tcp_tsq_write(struct sock *sk)
1072{
1073 if ((1 << sk->sk_state) &
1074 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
1075 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
1076 struct tcp_sock *tp = tcp_sk(sk);
1077
1078 if (tp->lost_out > tp->retrans_out &&
1079 tcp_snd_cwnd(tp) > tcp_packets_in_flight(tp)) {
1080 tcp_mstamp_refresh(tp);
1081 tcp_xmit_retransmit_queue(sk);
1082 }
1083
1084 tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
1085 0, GFP_ATOMIC);
1086 }
1087}
1088
1089static void tcp_tsq_handler(struct sock *sk)
1090{
1091 bh_lock_sock(sk);
1092 if (!sock_owned_by_user(sk))
1093 tcp_tsq_write(sk);
1094 else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
1095 sock_hold(sk);
1096 bh_unlock_sock(sk);
1097}
1098/*
1099 * One tasklet per cpu tries to send more skbs.
1100 * We run in tasklet context but need to disable irqs when
1101 * transferring tsq->head because tcp_wfree() might
1102 * interrupt us (non NAPI drivers)
1103 */
1104static void tcp_tasklet_func(struct tasklet_struct *t)
1105{
1106 struct tsq_tasklet *tsq = from_tasklet(tsq, t, tasklet);
1107 LIST_HEAD(list);
1108 unsigned long flags;
1109 struct list_head *q, *n;
1110 struct tcp_sock *tp;
1111 struct sock *sk;
1112
1113 local_irq_save(flags);
1114 list_splice_init(&tsq->head, &list);
1115 local_irq_restore(flags);
1116
1117 list_for_each_safe(q, n, &list) {
1118 tp = list_entry(q, struct tcp_sock, tsq_node);
1119 list_del(&tp->tsq_node);
1120
1121 sk = (struct sock *)tp;
1122 smp_mb__before_atomic();
1123 clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
1124
1125 tcp_tsq_handler(sk);
1126 sk_free(sk);
1127 }
1128}
1129
1130#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
1131 TCPF_WRITE_TIMER_DEFERRED | \
1132 TCPF_DELACK_TIMER_DEFERRED | \
1133 TCPF_MTU_REDUCED_DEFERRED | \
1134 TCPF_ACK_DEFERRED)
1135/**
1136 * tcp_release_cb - tcp release_sock() callback
1137 * @sk: socket
1138 *
1139 * called from release_sock() to perform protocol dependent
1140 * actions before socket release.
1141 */
1142void tcp_release_cb(struct sock *sk)
1143{
1144 unsigned long flags = smp_load_acquire(&sk->sk_tsq_flags);
1145 unsigned long nflags;
1146
1147 /* perform an atomic operation only if at least one flag is set */
1148 do {
1149 if (!(flags & TCP_DEFERRED_ALL))
1150 return;
1151 nflags = flags & ~TCP_DEFERRED_ALL;
1152 } while (!try_cmpxchg(&sk->sk_tsq_flags, &flags, nflags));
1153
1154 if (flags & TCPF_TSQ_DEFERRED) {
1155 tcp_tsq_write(sk);
1156 __sock_put(sk);
1157 }
1158
1159 if (flags & TCPF_WRITE_TIMER_DEFERRED) {
1160 tcp_write_timer_handler(sk);
1161 __sock_put(sk);
1162 }
1163 if (flags & TCPF_DELACK_TIMER_DEFERRED) {
1164 tcp_delack_timer_handler(sk);
1165 __sock_put(sk);
1166 }
1167 if (flags & TCPF_MTU_REDUCED_DEFERRED) {
1168 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
1169 __sock_put(sk);
1170 }
1171 if ((flags & TCPF_ACK_DEFERRED) && inet_csk_ack_scheduled(sk))
1172 tcp_send_ack(sk);
1173}
1174EXPORT_SYMBOL(tcp_release_cb);
1175
1176void __init tcp_tasklet_init(void)
1177{
1178 int i;
1179
1180 for_each_possible_cpu(i) {
1181 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
1182
1183 INIT_LIST_HEAD(&tsq->head);
1184 tasklet_setup(&tsq->tasklet, tcp_tasklet_func);
1185 }
1186}
1187
1188/*
1189 * Write buffer destructor automatically called from kfree_skb.
1190 * We can't xmit new skbs from this context, as we might already
1191 * hold qdisc lock.
1192 */
1193void tcp_wfree(struct sk_buff *skb)
1194{
1195 struct sock *sk = skb->sk;
1196 struct tcp_sock *tp = tcp_sk(sk);
1197 unsigned long flags, nval, oval;
1198 struct tsq_tasklet *tsq;
1199 bool empty;
1200
1201 /* Keep one reference on sk_wmem_alloc.
1202 * Will be released by sk_free() from here or tcp_tasklet_func()
1203 */
1204 WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
1205
1206 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
1207 * Wait until our queues (qdisc + devices) are drained.
1208 * This gives :
1209 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
1210 * - chance for incoming ACK (processed by another cpu maybe)
1211 * to migrate this flow (skb->ooo_okay will be eventually set)
1212 */
1213 if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
1214 goto out;
1215
1216 oval = smp_load_acquire(&sk->sk_tsq_flags);
1217 do {
1218 if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
1219 goto out;
1220
1221 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
1222 } while (!try_cmpxchg(&sk->sk_tsq_flags, &oval, nval));
1223
1224 /* queue this socket to tasklet queue */
1225 local_irq_save(flags);
1226 tsq = this_cpu_ptr(&tsq_tasklet);
1227 empty = list_empty(&tsq->head);
1228 list_add(&tp->tsq_node, &tsq->head);
1229 if (empty)
1230 tasklet_schedule(&tsq->tasklet);
1231 local_irq_restore(flags);
1232 return;
1233out:
1234 sk_free(sk);
1235}
1236
1237/* Note: Called under soft irq.
1238 * We can call TCP stack right away, unless socket is owned by user.
1239 */
1240enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
1241{
1242 struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
1243 struct sock *sk = (struct sock *)tp;
1244
1245 tcp_tsq_handler(sk);
1246 sock_put(sk);
1247
1248 return HRTIMER_NORESTART;
1249}
1250
1251static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb,
1252 u64 prior_wstamp)
1253{
1254 struct tcp_sock *tp = tcp_sk(sk);
1255
1256 if (sk->sk_pacing_status != SK_PACING_NONE) {
1257 unsigned long rate = READ_ONCE(sk->sk_pacing_rate);
1258
1259 /* Original sch_fq does not pace first 10 MSS
1260 * Note that tp->data_segs_out overflows after 2^32 packets,
1261 * this is a minor annoyance.
1262 */
1263 if (rate != ~0UL && rate && tp->data_segs_out >= 10) {
1264 u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate);
1265 u64 credit = tp->tcp_wstamp_ns - prior_wstamp;
1266
1267 /* take into account OS jitter */
1268 len_ns -= min_t(u64, len_ns / 2, credit);
1269 tp->tcp_wstamp_ns += len_ns;
1270 }
1271 }
1272 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
1273}
1274
1275INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1276INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1277INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb));
1278
1279/* This routine actually transmits TCP packets queued in by
1280 * tcp_do_sendmsg(). This is used by both the initial
1281 * transmission and possible later retransmissions.
1282 * All SKB's seen here are completely headerless. It is our
1283 * job to build the TCP header, and pass the packet down to
1284 * IP so it can do the same plus pass the packet off to the
1285 * device.
1286 *
1287 * We are working here with either a clone of the original
1288 * SKB, or a fresh unique copy made by the retransmit engine.
1289 */
1290static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
1291 int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
1292{
1293 const struct inet_connection_sock *icsk = inet_csk(sk);
1294 struct inet_sock *inet;
1295 struct tcp_sock *tp;
1296 struct tcp_skb_cb *tcb;
1297 struct tcp_out_options opts;
1298 unsigned int tcp_options_size, tcp_header_size;
1299 struct sk_buff *oskb = NULL;
1300 struct tcp_key key;
1301 struct tcphdr *th;
1302 u64 prior_wstamp;
1303 int err;
1304
1305 BUG_ON(!skb || !tcp_skb_pcount(skb));
1306 tp = tcp_sk(sk);
1307 prior_wstamp = tp->tcp_wstamp_ns;
1308 tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
1309 skb_set_delivery_time(skb, tp->tcp_wstamp_ns, SKB_CLOCK_MONOTONIC);
1310 if (clone_it) {
1311 oskb = skb;
1312
1313 tcp_skb_tsorted_save(oskb) {
1314 if (unlikely(skb_cloned(oskb)))
1315 skb = pskb_copy(oskb, gfp_mask);
1316 else
1317 skb = skb_clone(oskb, gfp_mask);
1318 } tcp_skb_tsorted_restore(oskb);
1319
1320 if (unlikely(!skb))
1321 return -ENOBUFS;
1322 /* retransmit skbs might have a non zero value in skb->dev
1323 * because skb->dev is aliased with skb->rbnode.rb_left
1324 */
1325 skb->dev = NULL;
1326 }
1327
1328 inet = inet_sk(sk);
1329 tcb = TCP_SKB_CB(skb);
1330 memset(&opts, 0, sizeof(opts));
1331
1332 tcp_get_current_key(sk, &key);
1333 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
1334 tcp_options_size = tcp_syn_options(sk, skb, &opts, &key);
1335 } else {
1336 tcp_options_size = tcp_established_options(sk, skb, &opts, &key);
1337 /* Force a PSH flag on all (GSO) packets to expedite GRO flush
1338 * at receiver : This slightly improve GRO performance.
1339 * Note that we do not force the PSH flag for non GSO packets,
1340 * because they might be sent under high congestion events,
1341 * and in this case it is better to delay the delivery of 1-MSS
1342 * packets and thus the corresponding ACK packet that would
1343 * release the following packet.
1344 */
1345 if (tcp_skb_pcount(skb) > 1)
1346 tcb->tcp_flags |= TCPHDR_PSH;
1347 }
1348 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1349
1350 /* We set skb->ooo_okay to one if this packet can select
1351 * a different TX queue than prior packets of this flow,
1352 * to avoid self inflicted reorders.
1353 * The 'other' queue decision is based on current cpu number
1354 * if XPS is enabled, or sk->sk_txhash otherwise.
1355 * We can switch to another (and better) queue if:
1356 * 1) No packet with payload is in qdisc/device queues.
1357 * Delays in TX completion can defeat the test
1358 * even if packets were already sent.
1359 * 2) Or rtx queue is empty.
1360 * This mitigates above case if ACK packets for
1361 * all prior packets were already processed.
1362 */
1363 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1) ||
1364 tcp_rtx_queue_empty(sk);
1365
1366 /* If we had to use memory reserve to allocate this skb,
1367 * this might cause drops if packet is looped back :
1368 * Other socket might not have SOCK_MEMALLOC.
1369 * Packets not looped back do not care about pfmemalloc.
1370 */
1371 skb->pfmemalloc = 0;
1372
1373 skb_push(skb, tcp_header_size);
1374 skb_reset_transport_header(skb);
1375
1376 skb_orphan(skb);
1377 skb->sk = sk;
1378 skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1379 refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1380
1381 skb_set_dst_pending_confirm(skb, READ_ONCE(sk->sk_dst_pending_confirm));
1382
1383 /* Build TCP header and checksum it. */
1384 th = (struct tcphdr *)skb->data;
1385 th->source = inet->inet_sport;
1386 th->dest = inet->inet_dport;
1387 th->seq = htonl(tcb->seq);
1388 th->ack_seq = htonl(rcv_nxt);
1389 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
1390 tcb->tcp_flags);
1391
1392 th->check = 0;
1393 th->urg_ptr = 0;
1394
1395 /* The urg_mode check is necessary during a below snd_una win probe */
1396 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
1397 if (before(tp->snd_up, tcb->seq + 0x10000)) {
1398 th->urg_ptr = htons(tp->snd_up - tcb->seq);
1399 th->urg = 1;
1400 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1401 th->urg_ptr = htons(0xFFFF);
1402 th->urg = 1;
1403 }
1404 }
1405
1406 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1407 if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
1408 th->window = htons(tcp_select_window(sk));
1409 tcp_ecn_send(sk, skb, th, tcp_header_size);
1410 } else {
1411 /* RFC1323: The window in SYN & SYN/ACK segments
1412 * is never scaled.
1413 */
1414 th->window = htons(min(tp->rcv_wnd, 65535U));
1415 }
1416
1417 tcp_options_write(th, tp, NULL, &opts, &key);
1418
1419 if (tcp_key_is_md5(&key)) {
1420#ifdef CONFIG_TCP_MD5SIG
1421 /* Calculate the MD5 hash, as we have all we need now */
1422 sk_gso_disable(sk);
1423 tp->af_specific->calc_md5_hash(opts.hash_location,
1424 key.md5_key, sk, skb);
1425#endif
1426 } else if (tcp_key_is_ao(&key)) {
1427 int err;
1428
1429 err = tcp_ao_transmit_skb(sk, skb, key.ao_key, th,
1430 opts.hash_location);
1431 if (err) {
1432 kfree_skb_reason(skb, SKB_DROP_REASON_NOT_SPECIFIED);
1433 return -ENOMEM;
1434 }
1435 }
1436
1437 /* BPF prog is the last one writing header option */
1438 bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts);
1439
1440 INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check,
1441 tcp_v6_send_check, tcp_v4_send_check,
1442 sk, skb);
1443
1444 if (likely(tcb->tcp_flags & TCPHDR_ACK))
1445 tcp_event_ack_sent(sk, rcv_nxt);
1446
1447 if (skb->len != tcp_header_size) {
1448 tcp_event_data_sent(tp, sk);
1449 tp->data_segs_out += tcp_skb_pcount(skb);
1450 tp->bytes_sent += skb->len - tcp_header_size;
1451 }
1452
1453 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1454 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1455 tcp_skb_pcount(skb));
1456
1457 tp->segs_out += tcp_skb_pcount(skb);
1458 skb_set_hash_from_sk(skb, sk);
1459 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1460 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1461 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1462
1463 /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */
1464
1465 /* Cleanup our debris for IP stacks */
1466 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1467 sizeof(struct inet6_skb_parm)));
1468
1469 tcp_add_tx_delay(skb, tp);
1470
1471 err = INDIRECT_CALL_INET(icsk->icsk_af_ops->queue_xmit,
1472 inet6_csk_xmit, ip_queue_xmit,
1473 sk, skb, &inet->cork.fl);
1474
1475 if (unlikely(err > 0)) {
1476 tcp_enter_cwr(sk);
1477 err = net_xmit_eval(err);
1478 }
1479 if (!err && oskb) {
1480 tcp_update_skb_after_send(sk, oskb, prior_wstamp);
1481 tcp_rate_skb_sent(sk, oskb);
1482 }
1483 return err;
1484}
1485
1486static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
1487 gfp_t gfp_mask)
1488{
1489 return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask,
1490 tcp_sk(sk)->rcv_nxt);
1491}
1492
1493/* This routine just queues the buffer for sending.
1494 *
1495 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1496 * otherwise socket can stall.
1497 */
1498static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1499{
1500 struct tcp_sock *tp = tcp_sk(sk);
1501
1502 /* Advance write_seq and place onto the write_queue. */
1503 WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq);
1504 __skb_header_release(skb);
1505 tcp_add_write_queue_tail(sk, skb);
1506 sk_wmem_queued_add(sk, skb->truesize);
1507 sk_mem_charge(sk, skb->truesize);
1508}
1509
1510/* Initialize TSO segments for a packet. */
1511static int tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1512{
1513 int tso_segs;
1514
1515 if (skb->len <= mss_now) {
1516 /* Avoid the costly divide in the normal
1517 * non-TSO case.
1518 */
1519 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1520 tcp_skb_pcount_set(skb, 1);
1521 return 1;
1522 }
1523 TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1524 tso_segs = DIV_ROUND_UP(skb->len, mss_now);
1525 tcp_skb_pcount_set(skb, tso_segs);
1526 return tso_segs;
1527}
1528
1529/* Pcount in the middle of the write queue got changed, we need to do various
1530 * tweaks to fix counters
1531 */
1532static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1533{
1534 struct tcp_sock *tp = tcp_sk(sk);
1535
1536 tp->packets_out -= decr;
1537
1538 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1539 tp->sacked_out -= decr;
1540 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1541 tp->retrans_out -= decr;
1542 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1543 tp->lost_out -= decr;
1544
1545 /* Reno case is special. Sigh... */
1546 if (tcp_is_reno(tp) && decr > 0)
1547 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1548
1549 if (tp->lost_skb_hint &&
1550 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1551 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
1552 tp->lost_cnt_hint -= decr;
1553
1554 tcp_verify_left_out(tp);
1555}
1556
1557static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
1558{
1559 return TCP_SKB_CB(skb)->txstamp_ack ||
1560 (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
1561}
1562
1563static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1564{
1565 struct skb_shared_info *shinfo = skb_shinfo(skb);
1566
1567 if (unlikely(tcp_has_tx_tstamp(skb)) &&
1568 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1569 struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1570 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1571
1572 shinfo->tx_flags &= ~tsflags;
1573 shinfo2->tx_flags |= tsflags;
1574 swap(shinfo->tskey, shinfo2->tskey);
1575 TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
1576 TCP_SKB_CB(skb)->txstamp_ack = 0;
1577 }
1578}
1579
1580static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
1581{
1582 TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
1583 TCP_SKB_CB(skb)->eor = 0;
1584}
1585
1586/* Insert buff after skb on the write or rtx queue of sk. */
1587static void tcp_insert_write_queue_after(struct sk_buff *skb,
1588 struct sk_buff *buff,
1589 struct sock *sk,
1590 enum tcp_queue tcp_queue)
1591{
1592 if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
1593 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1594 else
1595 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
1596}
1597
1598/* Function to create two new TCP segments. Shrinks the given segment
1599 * to the specified size and appends a new segment with the rest of the
1600 * packet to the list. This won't be called frequently, I hope.
1601 * Remember, these are still headerless SKBs at this point.
1602 */
1603int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1604 struct sk_buff *skb, u32 len,
1605 unsigned int mss_now, gfp_t gfp)
1606{
1607 struct tcp_sock *tp = tcp_sk(sk);
1608 struct sk_buff *buff;
1609 int old_factor;
1610 long limit;
1611 int nlen;
1612 u8 flags;
1613
1614 if (WARN_ON(len > skb->len))
1615 return -EINVAL;
1616
1617 DEBUG_NET_WARN_ON_ONCE(skb_headlen(skb));
1618
1619 /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb.
1620 * We need some allowance to not penalize applications setting small
1621 * SO_SNDBUF values.
1622 * Also allow first and last skb in retransmit queue to be split.
1623 */
1624 limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_LEGACY_MAX_SIZE);
1625 if (unlikely((sk->sk_wmem_queued >> 1) > limit &&
1626 tcp_queue != TCP_FRAG_IN_WRITE_QUEUE &&
1627 skb != tcp_rtx_queue_head(sk) &&
1628 skb != tcp_rtx_queue_tail(sk))) {
1629 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG);
1630 return -ENOMEM;
1631 }
1632
1633 if (skb_unclone_keeptruesize(skb, gfp))
1634 return -ENOMEM;
1635
1636 /* Get a new skb... force flag on. */
1637 buff = tcp_stream_alloc_skb(sk, gfp, true);
1638 if (!buff)
1639 return -ENOMEM; /* We'll just try again later. */
1640 skb_copy_decrypted(buff, skb);
1641 mptcp_skb_ext_copy(buff, skb);
1642
1643 sk_wmem_queued_add(sk, buff->truesize);
1644 sk_mem_charge(sk, buff->truesize);
1645 nlen = skb->len - len;
1646 buff->truesize += nlen;
1647 skb->truesize -= nlen;
1648
1649 /* Correct the sequence numbers. */
1650 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1651 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1652 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1653
1654 /* PSH and FIN should only be set in the second packet. */
1655 flags = TCP_SKB_CB(skb)->tcp_flags;
1656 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1657 TCP_SKB_CB(buff)->tcp_flags = flags;
1658 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1659 tcp_skb_fragment_eor(skb, buff);
1660
1661 skb_split(skb, buff, len);
1662
1663 skb_set_delivery_time(buff, skb->tstamp, SKB_CLOCK_MONOTONIC);
1664 tcp_fragment_tstamp(skb, buff);
1665
1666 old_factor = tcp_skb_pcount(skb);
1667
1668 /* Fix up tso_factor for both original and new SKB. */
1669 tcp_set_skb_tso_segs(skb, mss_now);
1670 tcp_set_skb_tso_segs(buff, mss_now);
1671
1672 /* Update delivered info for the new segment */
1673 TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
1674
1675 /* If this packet has been sent out already, we must
1676 * adjust the various packet counters.
1677 */
1678 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1679 int diff = old_factor - tcp_skb_pcount(skb) -
1680 tcp_skb_pcount(buff);
1681
1682 if (diff)
1683 tcp_adjust_pcount(sk, skb, diff);
1684 }
1685
1686 /* Link BUFF into the send queue. */
1687 __skb_header_release(buff);
1688 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1689 if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
1690 list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
1691
1692 return 0;
1693}
1694
1695/* This is similar to __pskb_pull_tail(). The difference is that pulled
1696 * data is not copied, but immediately discarded.
1697 */
1698static int __pskb_trim_head(struct sk_buff *skb, int len)
1699{
1700 struct skb_shared_info *shinfo;
1701 int i, k, eat;
1702
1703 DEBUG_NET_WARN_ON_ONCE(skb_headlen(skb));
1704 eat = len;
1705 k = 0;
1706 shinfo = skb_shinfo(skb);
1707 for (i = 0; i < shinfo->nr_frags; i++) {
1708 int size = skb_frag_size(&shinfo->frags[i]);
1709
1710 if (size <= eat) {
1711 skb_frag_unref(skb, i);
1712 eat -= size;
1713 } else {
1714 shinfo->frags[k] = shinfo->frags[i];
1715 if (eat) {
1716 skb_frag_off_add(&shinfo->frags[k], eat);
1717 skb_frag_size_sub(&shinfo->frags[k], eat);
1718 eat = 0;
1719 }
1720 k++;
1721 }
1722 }
1723 shinfo->nr_frags = k;
1724
1725 skb->data_len -= len;
1726 skb->len = skb->data_len;
1727 return len;
1728}
1729
1730/* Remove acked data from a packet in the transmit queue. */
1731int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1732{
1733 u32 delta_truesize;
1734
1735 if (skb_unclone_keeptruesize(skb, GFP_ATOMIC))
1736 return -ENOMEM;
1737
1738 delta_truesize = __pskb_trim_head(skb, len);
1739
1740 TCP_SKB_CB(skb)->seq += len;
1741
1742 skb->truesize -= delta_truesize;
1743 sk_wmem_queued_add(sk, -delta_truesize);
1744 if (!skb_zcopy_pure(skb))
1745 sk_mem_uncharge(sk, delta_truesize);
1746
1747 /* Any change of skb->len requires recalculation of tso factor. */
1748 if (tcp_skb_pcount(skb) > 1)
1749 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1750
1751 return 0;
1752}
1753
1754/* Calculate MSS not accounting any TCP options. */
1755static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1756{
1757 const struct tcp_sock *tp = tcp_sk(sk);
1758 const struct inet_connection_sock *icsk = inet_csk(sk);
1759 int mss_now;
1760
1761 /* Calculate base mss without TCP options:
1762 It is MMS_S - sizeof(tcphdr) of rfc1122
1763 */
1764 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1765
1766 /* Clamp it (mss_clamp does not include tcp options) */
1767 if (mss_now > tp->rx_opt.mss_clamp)
1768 mss_now = tp->rx_opt.mss_clamp;
1769
1770 /* Now subtract optional transport overhead */
1771 mss_now -= icsk->icsk_ext_hdr_len;
1772
1773 /* Then reserve room for full set of TCP options and 8 bytes of data */
1774 mss_now = max(mss_now,
1775 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss));
1776 return mss_now;
1777}
1778
1779/* Calculate MSS. Not accounting for SACKs here. */
1780int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1781{
1782 /* Subtract TCP options size, not including SACKs */
1783 return __tcp_mtu_to_mss(sk, pmtu) -
1784 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1785}
1786EXPORT_SYMBOL(tcp_mtu_to_mss);
1787
1788/* Inverse of above */
1789int tcp_mss_to_mtu(struct sock *sk, int mss)
1790{
1791 const struct tcp_sock *tp = tcp_sk(sk);
1792 const struct inet_connection_sock *icsk = inet_csk(sk);
1793
1794 return mss +
1795 tp->tcp_header_len +
1796 icsk->icsk_ext_hdr_len +
1797 icsk->icsk_af_ops->net_header_len;
1798}
1799EXPORT_SYMBOL(tcp_mss_to_mtu);
1800
1801/* MTU probing init per socket */
1802void tcp_mtup_init(struct sock *sk)
1803{
1804 struct tcp_sock *tp = tcp_sk(sk);
1805 struct inet_connection_sock *icsk = inet_csk(sk);
1806 struct net *net = sock_net(sk);
1807
1808 icsk->icsk_mtup.enabled = READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing) > 1;
1809 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1810 icsk->icsk_af_ops->net_header_len;
1811 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, READ_ONCE(net->ipv4.sysctl_tcp_base_mss));
1812 icsk->icsk_mtup.probe_size = 0;
1813 if (icsk->icsk_mtup.enabled)
1814 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1815}
1816EXPORT_SYMBOL(tcp_mtup_init);
1817
1818/* This function synchronize snd mss to current pmtu/exthdr set.
1819
1820 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1821 for TCP options, but includes only bare TCP header.
1822
1823 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1824 It is minimum of user_mss and mss received with SYN.
1825 It also does not include TCP options.
1826
1827 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1828
1829 tp->mss_cache is current effective sending mss, including
1830 all tcp options except for SACKs. It is evaluated,
1831 taking into account current pmtu, but never exceeds
1832 tp->rx_opt.mss_clamp.
1833
1834 NOTE1. rfc1122 clearly states that advertised MSS
1835 DOES NOT include either tcp or ip options.
1836
1837 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1838 are READ ONLY outside this function. --ANK (980731)
1839 */
1840unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1841{
1842 struct tcp_sock *tp = tcp_sk(sk);
1843 struct inet_connection_sock *icsk = inet_csk(sk);
1844 int mss_now;
1845
1846 if (icsk->icsk_mtup.search_high > pmtu)
1847 icsk->icsk_mtup.search_high = pmtu;
1848
1849 mss_now = tcp_mtu_to_mss(sk, pmtu);
1850 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1851
1852 /* And store cached results */
1853 icsk->icsk_pmtu_cookie = pmtu;
1854 if (icsk->icsk_mtup.enabled)
1855 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1856 tp->mss_cache = mss_now;
1857
1858 return mss_now;
1859}
1860EXPORT_SYMBOL(tcp_sync_mss);
1861
1862/* Compute the current effective MSS, taking SACKs and IP options,
1863 * and even PMTU discovery events into account.
1864 */
1865unsigned int tcp_current_mss(struct sock *sk)
1866{
1867 const struct tcp_sock *tp = tcp_sk(sk);
1868 const struct dst_entry *dst = __sk_dst_get(sk);
1869 u32 mss_now;
1870 unsigned int header_len;
1871 struct tcp_out_options opts;
1872 struct tcp_key key;
1873
1874 mss_now = tp->mss_cache;
1875
1876 if (dst) {
1877 u32 mtu = dst_mtu(dst);
1878 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1879 mss_now = tcp_sync_mss(sk, mtu);
1880 }
1881 tcp_get_current_key(sk, &key);
1882 header_len = tcp_established_options(sk, NULL, &opts, &key) +
1883 sizeof(struct tcphdr);
1884 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1885 * some common options. If this is an odd packet (because we have SACK
1886 * blocks etc) then our calculated header_len will be different, and
1887 * we have to adjust mss_now correspondingly */
1888 if (header_len != tp->tcp_header_len) {
1889 int delta = (int) header_len - tp->tcp_header_len;
1890 mss_now -= delta;
1891 }
1892
1893 return mss_now;
1894}
1895
1896/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1897 * As additional protections, we do not touch cwnd in retransmission phases,
1898 * and if application hit its sndbuf limit recently.
1899 */
1900static void tcp_cwnd_application_limited(struct sock *sk)
1901{
1902 struct tcp_sock *tp = tcp_sk(sk);
1903
1904 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
1905 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
1906 /* Limited by application or receiver window. */
1907 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
1908 u32 win_used = max(tp->snd_cwnd_used, init_win);
1909 if (win_used < tcp_snd_cwnd(tp)) {
1910 tp->snd_ssthresh = tcp_current_ssthresh(sk);
1911 tcp_snd_cwnd_set(tp, (tcp_snd_cwnd(tp) + win_used) >> 1);
1912 }
1913 tp->snd_cwnd_used = 0;
1914 }
1915 tp->snd_cwnd_stamp = tcp_jiffies32;
1916}
1917
1918static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1919{
1920 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1921 struct tcp_sock *tp = tcp_sk(sk);
1922
1923 /* Track the strongest available signal of the degree to which the cwnd
1924 * is fully utilized. If cwnd-limited then remember that fact for the
1925 * current window. If not cwnd-limited then track the maximum number of
1926 * outstanding packets in the current window. (If cwnd-limited then we
1927 * chose to not update tp->max_packets_out to avoid an extra else
1928 * clause with no functional impact.)
1929 */
1930 if (!before(tp->snd_una, tp->cwnd_usage_seq) ||
1931 is_cwnd_limited ||
1932 (!tp->is_cwnd_limited &&
1933 tp->packets_out > tp->max_packets_out)) {
1934 tp->is_cwnd_limited = is_cwnd_limited;
1935 tp->max_packets_out = tp->packets_out;
1936 tp->cwnd_usage_seq = tp->snd_nxt;
1937 }
1938
1939 if (tcp_is_cwnd_limited(sk)) {
1940 /* Network is feed fully. */
1941 tp->snd_cwnd_used = 0;
1942 tp->snd_cwnd_stamp = tcp_jiffies32;
1943 } else {
1944 /* Network starves. */
1945 if (tp->packets_out > tp->snd_cwnd_used)
1946 tp->snd_cwnd_used = tp->packets_out;
1947
1948 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle) &&
1949 (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1950 !ca_ops->cong_control)
1951 tcp_cwnd_application_limited(sk);
1952
1953 /* The following conditions together indicate the starvation
1954 * is caused by insufficient sender buffer:
1955 * 1) just sent some data (see tcp_write_xmit)
1956 * 2) not cwnd limited (this else condition)
1957 * 3) no more data to send (tcp_write_queue_empty())
1958 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1959 */
1960 if (tcp_write_queue_empty(sk) && sk->sk_socket &&
1961 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
1962 (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
1963 tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1964 }
1965}
1966
1967/* Minshall's variant of the Nagle send check. */
1968static bool tcp_minshall_check(const struct tcp_sock *tp)
1969{
1970 return after(tp->snd_sml, tp->snd_una) &&
1971 !after(tp->snd_sml, tp->snd_nxt);
1972}
1973
1974/* Update snd_sml if this skb is under mss
1975 * Note that a TSO packet might end with a sub-mss segment
1976 * The test is really :
1977 * if ((skb->len % mss) != 0)
1978 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1979 * But we can avoid doing the divide again given we already have
1980 * skb_pcount = skb->len / mss_now
1981 */
1982static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1983 const struct sk_buff *skb)
1984{
1985 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1986 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1987}
1988
1989/* Return false, if packet can be sent now without violation Nagle's rules:
1990 * 1. It is full sized. (provided by caller in %partial bool)
1991 * 2. Or it contains FIN. (already checked by caller)
1992 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1993 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1994 * With Minshall's modification: all sent small packets are ACKed.
1995 */
1996static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1997 int nonagle)
1998{
1999 return partial &&
2000 ((nonagle & TCP_NAGLE_CORK) ||
2001 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
2002}
2003
2004/* Return how many segs we'd like on a TSO packet,
2005 * depending on current pacing rate, and how close the peer is.
2006 *
2007 * Rationale is:
2008 * - For close peers, we rather send bigger packets to reduce
2009 * cpu costs, because occasional losses will be repaired fast.
2010 * - For long distance/rtt flows, we would like to get ACK clocking
2011 * with 1 ACK per ms.
2012 *
2013 * Use min_rtt to help adapt TSO burst size, with smaller min_rtt resulting
2014 * in bigger TSO bursts. We we cut the RTT-based allowance in half
2015 * for every 2^9 usec (aka 512 us) of RTT, so that the RTT-based allowance
2016 * is below 1500 bytes after 6 * ~500 usec = 3ms.
2017 */
2018static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
2019 int min_tso_segs)
2020{
2021 unsigned long bytes;
2022 u32 r;
2023
2024 bytes = READ_ONCE(sk->sk_pacing_rate) >> READ_ONCE(sk->sk_pacing_shift);
2025
2026 r = tcp_min_rtt(tcp_sk(sk)) >> READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_rtt_log);
2027 if (r < BITS_PER_TYPE(sk->sk_gso_max_size))
2028 bytes += sk->sk_gso_max_size >> r;
2029
2030 bytes = min_t(unsigned long, bytes, sk->sk_gso_max_size);
2031
2032 return max_t(u32, bytes / mss_now, min_tso_segs);
2033}
2034
2035/* Return the number of segments we want in the skb we are transmitting.
2036 * See if congestion control module wants to decide; otherwise, autosize.
2037 */
2038static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
2039{
2040 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
2041 u32 min_tso, tso_segs;
2042
2043 min_tso = ca_ops->min_tso_segs ?
2044 ca_ops->min_tso_segs(sk) :
2045 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs);
2046
2047 tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
2048 return min_t(u32, tso_segs, sk->sk_gso_max_segs);
2049}
2050
2051/* Returns the portion of skb which can be sent right away */
2052static unsigned int tcp_mss_split_point(const struct sock *sk,
2053 const struct sk_buff *skb,
2054 unsigned int mss_now,
2055 unsigned int max_segs,
2056 int nonagle)
2057{
2058 const struct tcp_sock *tp = tcp_sk(sk);
2059 u32 partial, needed, window, max_len;
2060
2061 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2062 max_len = mss_now * max_segs;
2063
2064 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
2065 return max_len;
2066
2067 needed = min(skb->len, window);
2068
2069 if (max_len <= needed)
2070 return max_len;
2071
2072 partial = needed % mss_now;
2073 /* If last segment is not a full MSS, check if Nagle rules allow us
2074 * to include this last segment in this skb.
2075 * Otherwise, we'll split the skb at last MSS boundary
2076 */
2077 if (tcp_nagle_check(partial != 0, tp, nonagle))
2078 return needed - partial;
2079
2080 return needed;
2081}
2082
2083/* Can at least one segment of SKB be sent right now, according to the
2084 * congestion window rules? If so, return how many segments are allowed.
2085 */
2086static u32 tcp_cwnd_test(const struct tcp_sock *tp)
2087{
2088 u32 in_flight, cwnd, halfcwnd;
2089
2090 in_flight = tcp_packets_in_flight(tp);
2091 cwnd = tcp_snd_cwnd(tp);
2092 if (in_flight >= cwnd)
2093 return 0;
2094
2095 /* For better scheduling, ensure we have at least
2096 * 2 GSO packets in flight.
2097 */
2098 halfcwnd = max(cwnd >> 1, 1U);
2099 return min(halfcwnd, cwnd - in_flight);
2100}
2101
2102/* Initialize TSO state of a skb.
2103 * This must be invoked the first time we consider transmitting
2104 * SKB onto the wire.
2105 */
2106static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
2107{
2108 int tso_segs = tcp_skb_pcount(skb);
2109
2110 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now))
2111 return tcp_set_skb_tso_segs(skb, mss_now);
2112
2113 return tso_segs;
2114}
2115
2116
2117/* Return true if the Nagle test allows this packet to be
2118 * sent now.
2119 */
2120static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
2121 unsigned int cur_mss, int nonagle)
2122{
2123 /* Nagle rule does not apply to frames, which sit in the middle of the
2124 * write_queue (they have no chances to get new data).
2125 *
2126 * This is implemented in the callers, where they modify the 'nonagle'
2127 * argument based upon the location of SKB in the send queue.
2128 */
2129 if (nonagle & TCP_NAGLE_PUSH)
2130 return true;
2131
2132 /* Don't use the nagle rule for urgent data (or for the final FIN). */
2133 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
2134 return true;
2135
2136 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
2137 return true;
2138
2139 return false;
2140}
2141
2142/* Does at least the first segment of SKB fit into the send window? */
2143static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
2144 const struct sk_buff *skb,
2145 unsigned int cur_mss)
2146{
2147 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2148
2149 if (skb->len > cur_mss)
2150 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
2151
2152 return !after(end_seq, tcp_wnd_end(tp));
2153}
2154
2155/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
2156 * which is put after SKB on the list. It is very much like
2157 * tcp_fragment() except that it may make several kinds of assumptions
2158 * in order to speed up the splitting operation. In particular, we
2159 * know that all the data is in scatter-gather pages, and that the
2160 * packet has never been sent out before (and thus is not cloned).
2161 */
2162static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
2163 unsigned int mss_now, gfp_t gfp)
2164{
2165 int nlen = skb->len - len;
2166 struct sk_buff *buff;
2167 u8 flags;
2168
2169 /* All of a TSO frame must be composed of paged data. */
2170 DEBUG_NET_WARN_ON_ONCE(skb->len != skb->data_len);
2171
2172 buff = tcp_stream_alloc_skb(sk, gfp, true);
2173 if (unlikely(!buff))
2174 return -ENOMEM;
2175 skb_copy_decrypted(buff, skb);
2176 mptcp_skb_ext_copy(buff, skb);
2177
2178 sk_wmem_queued_add(sk, buff->truesize);
2179 sk_mem_charge(sk, buff->truesize);
2180 buff->truesize += nlen;
2181 skb->truesize -= nlen;
2182
2183 /* Correct the sequence numbers. */
2184 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
2185 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
2186 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
2187
2188 /* PSH and FIN should only be set in the second packet. */
2189 flags = TCP_SKB_CB(skb)->tcp_flags;
2190 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
2191 TCP_SKB_CB(buff)->tcp_flags = flags;
2192
2193 tcp_skb_fragment_eor(skb, buff);
2194
2195 skb_split(skb, buff, len);
2196 tcp_fragment_tstamp(skb, buff);
2197
2198 /* Fix up tso_factor for both original and new SKB. */
2199 tcp_set_skb_tso_segs(skb, mss_now);
2200 tcp_set_skb_tso_segs(buff, mss_now);
2201
2202 /* Link BUFF into the send queue. */
2203 __skb_header_release(buff);
2204 tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE);
2205
2206 return 0;
2207}
2208
2209/* Try to defer sending, if possible, in order to minimize the amount
2210 * of TSO splitting we do. View it as a kind of TSO Nagle test.
2211 *
2212 * This algorithm is from John Heffner.
2213 */
2214static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
2215 bool *is_cwnd_limited,
2216 bool *is_rwnd_limited,
2217 u32 max_segs)
2218{
2219 const struct inet_connection_sock *icsk = inet_csk(sk);
2220 u32 send_win, cong_win, limit, in_flight;
2221 struct tcp_sock *tp = tcp_sk(sk);
2222 struct sk_buff *head;
2223 int win_divisor;
2224 s64 delta;
2225
2226 if (icsk->icsk_ca_state >= TCP_CA_Recovery)
2227 goto send_now;
2228
2229 /* Avoid bursty behavior by allowing defer
2230 * only if the last write was recent (1 ms).
2231 * Note that tp->tcp_wstamp_ns can be in the future if we have
2232 * packets waiting in a qdisc or device for EDT delivery.
2233 */
2234 delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC;
2235 if (delta > 0)
2236 goto send_now;
2237
2238 in_flight = tcp_packets_in_flight(tp);
2239
2240 BUG_ON(tcp_skb_pcount(skb) <= 1);
2241 BUG_ON(tcp_snd_cwnd(tp) <= in_flight);
2242
2243 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2244
2245 /* From in_flight test above, we know that cwnd > in_flight. */
2246 cong_win = (tcp_snd_cwnd(tp) - in_flight) * tp->mss_cache;
2247
2248 limit = min(send_win, cong_win);
2249
2250 /* If a full-sized TSO skb can be sent, do it. */
2251 if (limit >= max_segs * tp->mss_cache)
2252 goto send_now;
2253
2254 /* Middle in queue won't get any more data, full sendable already? */
2255 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
2256 goto send_now;
2257
2258 win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
2259 if (win_divisor) {
2260 u32 chunk = min(tp->snd_wnd, tcp_snd_cwnd(tp) * tp->mss_cache);
2261
2262 /* If at least some fraction of a window is available,
2263 * just use it.
2264 */
2265 chunk /= win_divisor;
2266 if (limit >= chunk)
2267 goto send_now;
2268 } else {
2269 /* Different approach, try not to defer past a single
2270 * ACK. Receiver should ACK every other full sized
2271 * frame, so if we have space for more than 3 frames
2272 * then send now.
2273 */
2274 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
2275 goto send_now;
2276 }
2277
2278 /* TODO : use tsorted_sent_queue ? */
2279 head = tcp_rtx_queue_head(sk);
2280 if (!head)
2281 goto send_now;
2282 delta = tp->tcp_clock_cache - head->tstamp;
2283 /* If next ACK is likely to come too late (half srtt), do not defer */
2284 if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0)
2285 goto send_now;
2286
2287 /* Ok, it looks like it is advisable to defer.
2288 * Three cases are tracked :
2289 * 1) We are cwnd-limited
2290 * 2) We are rwnd-limited
2291 * 3) We are application limited.
2292 */
2293 if (cong_win < send_win) {
2294 if (cong_win <= skb->len) {
2295 *is_cwnd_limited = true;
2296 return true;
2297 }
2298 } else {
2299 if (send_win <= skb->len) {
2300 *is_rwnd_limited = true;
2301 return true;
2302 }
2303 }
2304
2305 /* If this packet won't get more data, do not wait. */
2306 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
2307 TCP_SKB_CB(skb)->eor)
2308 goto send_now;
2309
2310 return true;
2311
2312send_now:
2313 return false;
2314}
2315
2316static inline void tcp_mtu_check_reprobe(struct sock *sk)
2317{
2318 struct inet_connection_sock *icsk = inet_csk(sk);
2319 struct tcp_sock *tp = tcp_sk(sk);
2320 struct net *net = sock_net(sk);
2321 u32 interval;
2322 s32 delta;
2323
2324 interval = READ_ONCE(net->ipv4.sysctl_tcp_probe_interval);
2325 delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2326 if (unlikely(delta >= interval * HZ)) {
2327 int mss = tcp_current_mss(sk);
2328
2329 /* Update current search range */
2330 icsk->icsk_mtup.probe_size = 0;
2331 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
2332 sizeof(struct tcphdr) +
2333 icsk->icsk_af_ops->net_header_len;
2334 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
2335
2336 /* Update probe time stamp */
2337 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2338 }
2339}
2340
2341static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
2342{
2343 struct sk_buff *skb, *next;
2344
2345 skb = tcp_send_head(sk);
2346 tcp_for_write_queue_from_safe(skb, next, sk) {
2347 if (len <= skb->len)
2348 break;
2349
2350 if (tcp_has_tx_tstamp(skb) || !tcp_skb_can_collapse(skb, next))
2351 return false;
2352
2353 len -= skb->len;
2354 }
2355
2356 return true;
2357}
2358
2359static int tcp_clone_payload(struct sock *sk, struct sk_buff *to,
2360 int probe_size)
2361{
2362 skb_frag_t *lastfrag = NULL, *fragto = skb_shinfo(to)->frags;
2363 int i, todo, len = 0, nr_frags = 0;
2364 const struct sk_buff *skb;
2365
2366 if (!sk_wmem_schedule(sk, to->truesize + probe_size))
2367 return -ENOMEM;
2368
2369 skb_queue_walk(&sk->sk_write_queue, skb) {
2370 const skb_frag_t *fragfrom = skb_shinfo(skb)->frags;
2371
2372 if (skb_headlen(skb))
2373 return -EINVAL;
2374
2375 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++, fragfrom++) {
2376 if (len >= probe_size)
2377 goto commit;
2378 todo = min_t(int, skb_frag_size(fragfrom),
2379 probe_size - len);
2380 len += todo;
2381 if (lastfrag &&
2382 skb_frag_page(fragfrom) == skb_frag_page(lastfrag) &&
2383 skb_frag_off(fragfrom) == skb_frag_off(lastfrag) +
2384 skb_frag_size(lastfrag)) {
2385 skb_frag_size_add(lastfrag, todo);
2386 continue;
2387 }
2388 if (unlikely(nr_frags == MAX_SKB_FRAGS))
2389 return -E2BIG;
2390 skb_frag_page_copy(fragto, fragfrom);
2391 skb_frag_off_copy(fragto, fragfrom);
2392 skb_frag_size_set(fragto, todo);
2393 nr_frags++;
2394 lastfrag = fragto++;
2395 }
2396 }
2397commit:
2398 WARN_ON_ONCE(len != probe_size);
2399 for (i = 0; i < nr_frags; i++)
2400 skb_frag_ref(to, i);
2401
2402 skb_shinfo(to)->nr_frags = nr_frags;
2403 to->truesize += probe_size;
2404 to->len += probe_size;
2405 to->data_len += probe_size;
2406 __skb_header_release(to);
2407 return 0;
2408}
2409
2410/* tcp_mtu_probe() and tcp_grow_skb() can both eat an skb (src) if
2411 * all its payload was moved to another one (dst).
2412 * Make sure to transfer tcp_flags, eor, and tstamp.
2413 */
2414static void tcp_eat_one_skb(struct sock *sk,
2415 struct sk_buff *dst,
2416 struct sk_buff *src)
2417{
2418 TCP_SKB_CB(dst)->tcp_flags |= TCP_SKB_CB(src)->tcp_flags;
2419 TCP_SKB_CB(dst)->eor = TCP_SKB_CB(src)->eor;
2420 tcp_skb_collapse_tstamp(dst, src);
2421 tcp_unlink_write_queue(src, sk);
2422 tcp_wmem_free_skb(sk, src);
2423}
2424
2425/* Create a new MTU probe if we are ready.
2426 * MTU probe is regularly attempting to increase the path MTU by
2427 * deliberately sending larger packets. This discovers routing
2428 * changes resulting in larger path MTUs.
2429 *
2430 * Returns 0 if we should wait to probe (no cwnd available),
2431 * 1 if a probe was sent,
2432 * -1 otherwise
2433 */
2434static int tcp_mtu_probe(struct sock *sk)
2435{
2436 struct inet_connection_sock *icsk = inet_csk(sk);
2437 struct tcp_sock *tp = tcp_sk(sk);
2438 struct sk_buff *skb, *nskb, *next;
2439 struct net *net = sock_net(sk);
2440 int probe_size;
2441 int size_needed;
2442 int copy, len;
2443 int mss_now;
2444 int interval;
2445
2446 /* Not currently probing/verifying,
2447 * not in recovery,
2448 * have enough cwnd, and
2449 * not SACKing (the variable headers throw things off)
2450 */
2451 if (likely(!icsk->icsk_mtup.enabled ||
2452 icsk->icsk_mtup.probe_size ||
2453 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
2454 tcp_snd_cwnd(tp) < 11 ||
2455 tp->rx_opt.num_sacks || tp->rx_opt.dsack))
2456 return -1;
2457
2458 /* Use binary search for probe_size between tcp_mss_base,
2459 * and current mss_clamp. if (search_high - search_low)
2460 * smaller than a threshold, backoff from probing.
2461 */
2462 mss_now = tcp_current_mss(sk);
2463 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
2464 icsk->icsk_mtup.search_low) >> 1);
2465 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2466 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2467 /* When misfortune happens, we are reprobing actively,
2468 * and then reprobe timer has expired. We stick with current
2469 * probing process by not resetting search range to its orignal.
2470 */
2471 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2472 interval < READ_ONCE(net->ipv4.sysctl_tcp_probe_threshold)) {
2473 /* Check whether enough time has elaplased for
2474 * another round of probing.
2475 */
2476 tcp_mtu_check_reprobe(sk);
2477 return -1;
2478 }
2479
2480 /* Have enough data in the send queue to probe? */
2481 if (tp->write_seq - tp->snd_nxt < size_needed)
2482 return -1;
2483
2484 if (tp->snd_wnd < size_needed)
2485 return -1;
2486 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2487 return 0;
2488
2489 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2490 if (tcp_packets_in_flight(tp) + 2 > tcp_snd_cwnd(tp)) {
2491 if (!tcp_packets_in_flight(tp))
2492 return -1;
2493 else
2494 return 0;
2495 }
2496
2497 if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
2498 return -1;
2499
2500 /* We're allowed to probe. Build it now. */
2501 nskb = tcp_stream_alloc_skb(sk, GFP_ATOMIC, false);
2502 if (!nskb)
2503 return -1;
2504
2505 /* build the payload, and be prepared to abort if this fails. */
2506 if (tcp_clone_payload(sk, nskb, probe_size)) {
2507 tcp_skb_tsorted_anchor_cleanup(nskb);
2508 consume_skb(nskb);
2509 return -1;
2510 }
2511 sk_wmem_queued_add(sk, nskb->truesize);
2512 sk_mem_charge(sk, nskb->truesize);
2513
2514 skb = tcp_send_head(sk);
2515 skb_copy_decrypted(nskb, skb);
2516 mptcp_skb_ext_copy(nskb, skb);
2517
2518 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
2519 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
2520 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
2521
2522 tcp_insert_write_queue_before(nskb, skb, sk);
2523 tcp_highest_sack_replace(sk, skb, nskb);
2524
2525 len = 0;
2526 tcp_for_write_queue_from_safe(skb, next, sk) {
2527 copy = min_t(int, skb->len, probe_size - len);
2528
2529 if (skb->len <= copy) {
2530 tcp_eat_one_skb(sk, nskb, skb);
2531 } else {
2532 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
2533 ~(TCPHDR_FIN|TCPHDR_PSH);
2534 __pskb_trim_head(skb, copy);
2535 tcp_set_skb_tso_segs(skb, mss_now);
2536 TCP_SKB_CB(skb)->seq += copy;
2537 }
2538
2539 len += copy;
2540
2541 if (len >= probe_size)
2542 break;
2543 }
2544 tcp_init_tso_segs(nskb, nskb->len);
2545
2546 /* We're ready to send. If this fails, the probe will
2547 * be resegmented into mss-sized pieces by tcp_write_xmit().
2548 */
2549 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
2550 /* Decrement cwnd here because we are sending
2551 * effectively two packets. */
2552 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) - 1);
2553 tcp_event_new_data_sent(sk, nskb);
2554
2555 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2556 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
2557 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
2558
2559 return 1;
2560 }
2561
2562 return -1;
2563}
2564
2565static bool tcp_pacing_check(struct sock *sk)
2566{
2567 struct tcp_sock *tp = tcp_sk(sk);
2568
2569 if (!tcp_needs_internal_pacing(sk))
2570 return false;
2571
2572 if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache)
2573 return false;
2574
2575 if (!hrtimer_is_queued(&tp->pacing_timer)) {
2576 hrtimer_start(&tp->pacing_timer,
2577 ns_to_ktime(tp->tcp_wstamp_ns),
2578 HRTIMER_MODE_ABS_PINNED_SOFT);
2579 sock_hold(sk);
2580 }
2581 return true;
2582}
2583
2584static bool tcp_rtx_queue_empty_or_single_skb(const struct sock *sk)
2585{
2586 const struct rb_node *node = sk->tcp_rtx_queue.rb_node;
2587
2588 /* No skb in the rtx queue. */
2589 if (!node)
2590 return true;
2591
2592 /* Only one skb in rtx queue. */
2593 return !node->rb_left && !node->rb_right;
2594}
2595
2596/* TCP Small Queues :
2597 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2598 * (These limits are doubled for retransmits)
2599 * This allows for :
2600 * - better RTT estimation and ACK scheduling
2601 * - faster recovery
2602 * - high rates
2603 * Alas, some drivers / subsystems require a fair amount
2604 * of queued bytes to ensure line rate.
2605 * One example is wifi aggregation (802.11 AMPDU)
2606 */
2607static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
2608 unsigned int factor)
2609{
2610 unsigned long limit;
2611
2612 limit = max_t(unsigned long,
2613 2 * skb->truesize,
2614 READ_ONCE(sk->sk_pacing_rate) >> READ_ONCE(sk->sk_pacing_shift));
2615 if (sk->sk_pacing_status == SK_PACING_NONE)
2616 limit = min_t(unsigned long, limit,
2617 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes));
2618 limit <<= factor;
2619
2620 if (static_branch_unlikely(&tcp_tx_delay_enabled) &&
2621 tcp_sk(sk)->tcp_tx_delay) {
2622 u64 extra_bytes = (u64)READ_ONCE(sk->sk_pacing_rate) *
2623 tcp_sk(sk)->tcp_tx_delay;
2624
2625 /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we
2626 * approximate our needs assuming an ~100% skb->truesize overhead.
2627 * USEC_PER_SEC is approximated by 2^20.
2628 * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift.
2629 */
2630 extra_bytes >>= (20 - 1);
2631 limit += extra_bytes;
2632 }
2633 if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2634 /* Always send skb if rtx queue is empty or has one skb.
2635 * No need to wait for TX completion to call us back,
2636 * after softirq/tasklet schedule.
2637 * This helps when TX completions are delayed too much.
2638 */
2639 if (tcp_rtx_queue_empty_or_single_skb(sk))
2640 return false;
2641
2642 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2643 /* It is possible TX completion already happened
2644 * before we set TSQ_THROTTLED, so we must
2645 * test again the condition.
2646 */
2647 smp_mb__after_atomic();
2648 if (refcount_read(&sk->sk_wmem_alloc) > limit)
2649 return true;
2650 }
2651 return false;
2652}
2653
2654static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
2655{
2656 const u32 now = tcp_jiffies32;
2657 enum tcp_chrono old = tp->chrono_type;
2658
2659 if (old > TCP_CHRONO_UNSPEC)
2660 tp->chrono_stat[old - 1] += now - tp->chrono_start;
2661 tp->chrono_start = now;
2662 tp->chrono_type = new;
2663}
2664
2665void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
2666{
2667 struct tcp_sock *tp = tcp_sk(sk);
2668
2669 /* If there are multiple conditions worthy of tracking in a
2670 * chronograph then the highest priority enum takes precedence
2671 * over the other conditions. So that if something "more interesting"
2672 * starts happening, stop the previous chrono and start a new one.
2673 */
2674 if (type > tp->chrono_type)
2675 tcp_chrono_set(tp, type);
2676}
2677
2678void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
2679{
2680 struct tcp_sock *tp = tcp_sk(sk);
2681
2682
2683 /* There are multiple conditions worthy of tracking in a
2684 * chronograph, so that the highest priority enum takes
2685 * precedence over the other conditions (see tcp_chrono_start).
2686 * If a condition stops, we only stop chrono tracking if
2687 * it's the "most interesting" or current chrono we are
2688 * tracking and starts busy chrono if we have pending data.
2689 */
2690 if (tcp_rtx_and_write_queues_empty(sk))
2691 tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
2692 else if (type == tp->chrono_type)
2693 tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2694}
2695
2696/* First skb in the write queue is smaller than ideal packet size.
2697 * Check if we can move payload from the second skb in the queue.
2698 */
2699static void tcp_grow_skb(struct sock *sk, struct sk_buff *skb, int amount)
2700{
2701 struct sk_buff *next_skb = skb->next;
2702 unsigned int nlen;
2703
2704 if (tcp_skb_is_last(sk, skb))
2705 return;
2706
2707 if (!tcp_skb_can_collapse(skb, next_skb))
2708 return;
2709
2710 nlen = min_t(u32, amount, next_skb->len);
2711 if (!nlen || !skb_shift(skb, next_skb, nlen))
2712 return;
2713
2714 TCP_SKB_CB(skb)->end_seq += nlen;
2715 TCP_SKB_CB(next_skb)->seq += nlen;
2716
2717 if (!next_skb->len) {
2718 /* In case FIN is set, we need to update end_seq */
2719 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2720
2721 tcp_eat_one_skb(sk, skb, next_skb);
2722 }
2723}
2724
2725/* This routine writes packets to the network. It advances the
2726 * send_head. This happens as incoming acks open up the remote
2727 * window for us.
2728 *
2729 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2730 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2731 * account rare use of URG, this is not a big flaw.
2732 *
2733 * Send at most one packet when push_one > 0. Temporarily ignore
2734 * cwnd limit to force at most one packet out when push_one == 2.
2735
2736 * Returns true, if no segments are in flight and we have queued segments,
2737 * but cannot send anything now because of SWS or another problem.
2738 */
2739static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2740 int push_one, gfp_t gfp)
2741{
2742 struct tcp_sock *tp = tcp_sk(sk);
2743 struct sk_buff *skb;
2744 unsigned int tso_segs, sent_pkts;
2745 u32 cwnd_quota, max_segs;
2746 int result;
2747 bool is_cwnd_limited = false, is_rwnd_limited = false;
2748
2749 sent_pkts = 0;
2750
2751 tcp_mstamp_refresh(tp);
2752 if (!push_one) {
2753 /* Do MTU probing. */
2754 result = tcp_mtu_probe(sk);
2755 if (!result) {
2756 return false;
2757 } else if (result > 0) {
2758 sent_pkts = 1;
2759 }
2760 }
2761
2762 max_segs = tcp_tso_segs(sk, mss_now);
2763 while ((skb = tcp_send_head(sk))) {
2764 unsigned int limit;
2765 int missing_bytes;
2766
2767 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2768 /* "skb_mstamp_ns" is used as a start point for the retransmit timer */
2769 tp->tcp_wstamp_ns = tp->tcp_clock_cache;
2770 skb_set_delivery_time(skb, tp->tcp_wstamp_ns, SKB_CLOCK_MONOTONIC);
2771 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
2772 tcp_init_tso_segs(skb, mss_now);
2773 goto repair; /* Skip network transmission */
2774 }
2775
2776 if (tcp_pacing_check(sk))
2777 break;
2778
2779 cwnd_quota = tcp_cwnd_test(tp);
2780 if (!cwnd_quota) {
2781 if (push_one == 2)
2782 /* Force out a loss probe pkt. */
2783 cwnd_quota = 1;
2784 else
2785 break;
2786 }
2787 cwnd_quota = min(cwnd_quota, max_segs);
2788 missing_bytes = cwnd_quota * mss_now - skb->len;
2789 if (missing_bytes > 0)
2790 tcp_grow_skb(sk, skb, missing_bytes);
2791
2792 tso_segs = tcp_set_skb_tso_segs(skb, mss_now);
2793
2794 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
2795 is_rwnd_limited = true;
2796 break;
2797 }
2798
2799 if (tso_segs == 1) {
2800 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2801 (tcp_skb_is_last(sk, skb) ?
2802 nonagle : TCP_NAGLE_PUSH))))
2803 break;
2804 } else {
2805 if (!push_one &&
2806 tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2807 &is_rwnd_limited, max_segs))
2808 break;
2809 }
2810
2811 limit = mss_now;
2812 if (tso_segs > 1 && !tcp_urg_mode(tp))
2813 limit = tcp_mss_split_point(sk, skb, mss_now,
2814 cwnd_quota,
2815 nonagle);
2816
2817 if (skb->len > limit &&
2818 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
2819 break;
2820
2821 if (tcp_small_queue_check(sk, skb, 0))
2822 break;
2823
2824 /* Argh, we hit an empty skb(), presumably a thread
2825 * is sleeping in sendmsg()/sk_stream_wait_memory().
2826 * We do not want to send a pure-ack packet and have
2827 * a strange looking rtx queue with empty packet(s).
2828 */
2829 if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq)
2830 break;
2831
2832 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2833 break;
2834
2835repair:
2836 /* Advance the send_head. This one is sent out.
2837 * This call will increment packets_out.
2838 */
2839 tcp_event_new_data_sent(sk, skb);
2840
2841 tcp_minshall_update(tp, mss_now, skb);
2842 sent_pkts += tcp_skb_pcount(skb);
2843
2844 if (push_one)
2845 break;
2846 }
2847
2848 if (is_rwnd_limited)
2849 tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
2850 else
2851 tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
2852
2853 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tcp_snd_cwnd(tp));
2854 if (likely(sent_pkts || is_cwnd_limited))
2855 tcp_cwnd_validate(sk, is_cwnd_limited);
2856
2857 if (likely(sent_pkts)) {
2858 if (tcp_in_cwnd_reduction(sk))
2859 tp->prr_out += sent_pkts;
2860
2861 /* Send one loss probe per tail loss episode. */
2862 if (push_one != 2)
2863 tcp_schedule_loss_probe(sk, false);
2864 return false;
2865 }
2866 return !tp->packets_out && !tcp_write_queue_empty(sk);
2867}
2868
2869bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
2870{
2871 struct inet_connection_sock *icsk = inet_csk(sk);
2872 struct tcp_sock *tp = tcp_sk(sk);
2873 u32 timeout, timeout_us, rto_delta_us;
2874 int early_retrans;
2875
2876 /* Don't do any loss probe on a Fast Open connection before 3WHS
2877 * finishes.
2878 */
2879 if (rcu_access_pointer(tp->fastopen_rsk))
2880 return false;
2881
2882 early_retrans = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_early_retrans);
2883 /* Schedule a loss probe in 2*RTT for SACK capable connections
2884 * not in loss recovery, that are either limited by cwnd or application.
2885 */
2886 if ((early_retrans != 3 && early_retrans != 4) ||
2887 !tp->packets_out || !tcp_is_sack(tp) ||
2888 (icsk->icsk_ca_state != TCP_CA_Open &&
2889 icsk->icsk_ca_state != TCP_CA_CWR))
2890 return false;
2891
2892 /* Probe timeout is 2*rtt. Add minimum RTO to account
2893 * for delayed ack when there's one outstanding packet. If no RTT
2894 * sample is available then probe after TCP_TIMEOUT_INIT.
2895 */
2896 if (tp->srtt_us) {
2897 timeout_us = tp->srtt_us >> 2;
2898 if (tp->packets_out == 1)
2899 timeout_us += tcp_rto_min_us(sk);
2900 else
2901 timeout_us += TCP_TIMEOUT_MIN_US;
2902 timeout = usecs_to_jiffies(timeout_us);
2903 } else {
2904 timeout = TCP_TIMEOUT_INIT;
2905 }
2906
2907 /* If the RTO formula yields an earlier time, then use that time. */
2908 rto_delta_us = advancing_rto ?
2909 jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
2910 tcp_rto_delta_us(sk); /* How far in future is RTO? */
2911 if (rto_delta_us > 0)
2912 timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
2913
2914 tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, TCP_RTO_MAX);
2915 return true;
2916}
2917
2918/* Thanks to skb fast clones, we can detect if a prior transmit of
2919 * a packet is still in a qdisc or driver queue.
2920 * In this case, there is very little point doing a retransmit !
2921 */
2922static bool skb_still_in_host_queue(struct sock *sk,
2923 const struct sk_buff *skb)
2924{
2925 if (unlikely(skb_fclone_busy(sk, skb))) {
2926 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2927 smp_mb__after_atomic();
2928 if (skb_fclone_busy(sk, skb)) {
2929 NET_INC_STATS(sock_net(sk),
2930 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2931 return true;
2932 }
2933 }
2934 return false;
2935}
2936
2937/* When probe timeout (PTO) fires, try send a new segment if possible, else
2938 * retransmit the last segment.
2939 */
2940void tcp_send_loss_probe(struct sock *sk)
2941{
2942 struct tcp_sock *tp = tcp_sk(sk);
2943 struct sk_buff *skb;
2944 int pcount;
2945 int mss = tcp_current_mss(sk);
2946
2947 /* At most one outstanding TLP */
2948 if (tp->tlp_high_seq)
2949 goto rearm_timer;
2950
2951 tp->tlp_retrans = 0;
2952 skb = tcp_send_head(sk);
2953 if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
2954 pcount = tp->packets_out;
2955 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2956 if (tp->packets_out > pcount)
2957 goto probe_sent;
2958 goto rearm_timer;
2959 }
2960 skb = skb_rb_last(&sk->tcp_rtx_queue);
2961 if (unlikely(!skb)) {
2962 tcp_warn_once(sk, tp->packets_out, "invalid inflight: ");
2963 smp_store_release(&inet_csk(sk)->icsk_pending, 0);
2964 return;
2965 }
2966
2967 if (skb_still_in_host_queue(sk, skb))
2968 goto rearm_timer;
2969
2970 pcount = tcp_skb_pcount(skb);
2971 if (WARN_ON(!pcount))
2972 goto rearm_timer;
2973
2974 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2975 if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
2976 (pcount - 1) * mss, mss,
2977 GFP_ATOMIC)))
2978 goto rearm_timer;
2979 skb = skb_rb_next(skb);
2980 }
2981
2982 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2983 goto rearm_timer;
2984
2985 if (__tcp_retransmit_skb(sk, skb, 1))
2986 goto rearm_timer;
2987
2988 tp->tlp_retrans = 1;
2989
2990probe_sent:
2991 /* Record snd_nxt for loss detection. */
2992 tp->tlp_high_seq = tp->snd_nxt;
2993
2994 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2995 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2996 smp_store_release(&inet_csk(sk)->icsk_pending, 0);
2997rearm_timer:
2998 tcp_rearm_rto(sk);
2999}
3000
3001/* Push out any pending frames which were held back due to
3002 * TCP_CORK or attempt at coalescing tiny packets.
3003 * The socket must be locked by the caller.
3004 */
3005void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
3006 int nonagle)
3007{
3008 /* If we are closed, the bytes will have to remain here.
3009 * In time closedown will finish, we empty the write queue and
3010 * all will be happy.
3011 */
3012 if (unlikely(sk->sk_state == TCP_CLOSE))
3013 return;
3014
3015 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
3016 sk_gfp_mask(sk, GFP_ATOMIC)))
3017 tcp_check_probe_timer(sk);
3018}
3019
3020/* Send _single_ skb sitting at the send head. This function requires
3021 * true push pending frames to setup probe timer etc.
3022 */
3023void tcp_push_one(struct sock *sk, unsigned int mss_now)
3024{
3025 struct sk_buff *skb = tcp_send_head(sk);
3026
3027 BUG_ON(!skb || skb->len < mss_now);
3028
3029 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
3030}
3031
3032/* This function returns the amount that we can raise the
3033 * usable window based on the following constraints
3034 *
3035 * 1. The window can never be shrunk once it is offered (RFC 793)
3036 * 2. We limit memory per socket
3037 *
3038 * RFC 1122:
3039 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
3040 * RECV.NEXT + RCV.WIN fixed until:
3041 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
3042 *
3043 * i.e. don't raise the right edge of the window until you can raise
3044 * it at least MSS bytes.
3045 *
3046 * Unfortunately, the recommended algorithm breaks header prediction,
3047 * since header prediction assumes th->window stays fixed.
3048 *
3049 * Strictly speaking, keeping th->window fixed violates the receiver
3050 * side SWS prevention criteria. The problem is that under this rule
3051 * a stream of single byte packets will cause the right side of the
3052 * window to always advance by a single byte.
3053 *
3054 * Of course, if the sender implements sender side SWS prevention
3055 * then this will not be a problem.
3056 *
3057 * BSD seems to make the following compromise:
3058 *
3059 * If the free space is less than the 1/4 of the maximum
3060 * space available and the free space is less than 1/2 mss,
3061 * then set the window to 0.
3062 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
3063 * Otherwise, just prevent the window from shrinking
3064 * and from being larger than the largest representable value.
3065 *
3066 * This prevents incremental opening of the window in the regime
3067 * where TCP is limited by the speed of the reader side taking
3068 * data out of the TCP receive queue. It does nothing about
3069 * those cases where the window is constrained on the sender side
3070 * because the pipeline is full.
3071 *
3072 * BSD also seems to "accidentally" limit itself to windows that are a
3073 * multiple of MSS, at least until the free space gets quite small.
3074 * This would appear to be a side effect of the mbuf implementation.
3075 * Combining these two algorithms results in the observed behavior
3076 * of having a fixed window size at almost all times.
3077 *
3078 * Below we obtain similar behavior by forcing the offered window to
3079 * a multiple of the mss when it is feasible to do so.
3080 *
3081 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
3082 * Regular options like TIMESTAMP are taken into account.
3083 */
3084u32 __tcp_select_window(struct sock *sk)
3085{
3086 struct inet_connection_sock *icsk = inet_csk(sk);
3087 struct tcp_sock *tp = tcp_sk(sk);
3088 struct net *net = sock_net(sk);
3089 /* MSS for the peer's data. Previous versions used mss_clamp
3090 * here. I don't know if the value based on our guesses
3091 * of peer's MSS is better for the performance. It's more correct
3092 * but may be worse for the performance because of rcv_mss
3093 * fluctuations. --SAW 1998/11/1
3094 */
3095 int mss = icsk->icsk_ack.rcv_mss;
3096 int free_space = tcp_space(sk);
3097 int allowed_space = tcp_full_space(sk);
3098 int full_space, window;
3099
3100 if (sk_is_mptcp(sk))
3101 mptcp_space(sk, &free_space, &allowed_space);
3102
3103 full_space = min_t(int, tp->window_clamp, allowed_space);
3104
3105 if (unlikely(mss > full_space)) {
3106 mss = full_space;
3107 if (mss <= 0)
3108 return 0;
3109 }
3110
3111 /* Only allow window shrink if the sysctl is enabled and we have
3112 * a non-zero scaling factor in effect.
3113 */
3114 if (READ_ONCE(net->ipv4.sysctl_tcp_shrink_window) && tp->rx_opt.rcv_wscale)
3115 goto shrink_window_allowed;
3116
3117 /* do not allow window to shrink */
3118
3119 if (free_space < (full_space >> 1)) {
3120 icsk->icsk_ack.quick = 0;
3121
3122 if (tcp_under_memory_pressure(sk))
3123 tcp_adjust_rcv_ssthresh(sk);
3124
3125 /* free_space might become our new window, make sure we don't
3126 * increase it due to wscale.
3127 */
3128 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
3129
3130 /* if free space is less than mss estimate, or is below 1/16th
3131 * of the maximum allowed, try to move to zero-window, else
3132 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
3133 * new incoming data is dropped due to memory limits.
3134 * With large window, mss test triggers way too late in order
3135 * to announce zero window in time before rmem limit kicks in.
3136 */
3137 if (free_space < (allowed_space >> 4) || free_space < mss)
3138 return 0;
3139 }
3140
3141 if (free_space > tp->rcv_ssthresh)
3142 free_space = tp->rcv_ssthresh;
3143
3144 /* Don't do rounding if we are using window scaling, since the
3145 * scaled window will not line up with the MSS boundary anyway.
3146 */
3147 if (tp->rx_opt.rcv_wscale) {
3148 window = free_space;
3149
3150 /* Advertise enough space so that it won't get scaled away.
3151 * Import case: prevent zero window announcement if
3152 * 1<<rcv_wscale > mss.
3153 */
3154 window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
3155 } else {
3156 window = tp->rcv_wnd;
3157 /* Get the largest window that is a nice multiple of mss.
3158 * Window clamp already applied above.
3159 * If our current window offering is within 1 mss of the
3160 * free space we just keep it. This prevents the divide
3161 * and multiply from happening most of the time.
3162 * We also don't do any window rounding when the free space
3163 * is too small.
3164 */
3165 if (window <= free_space - mss || window > free_space)
3166 window = rounddown(free_space, mss);
3167 else if (mss == full_space &&
3168 free_space > window + (full_space >> 1))
3169 window = free_space;
3170 }
3171
3172 return window;
3173
3174shrink_window_allowed:
3175 /* new window should always be an exact multiple of scaling factor */
3176 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
3177
3178 if (free_space < (full_space >> 1)) {
3179 icsk->icsk_ack.quick = 0;
3180
3181 if (tcp_under_memory_pressure(sk))
3182 tcp_adjust_rcv_ssthresh(sk);
3183
3184 /* if free space is too low, return a zero window */
3185 if (free_space < (allowed_space >> 4) || free_space < mss ||
3186 free_space < (1 << tp->rx_opt.rcv_wscale))
3187 return 0;
3188 }
3189
3190 if (free_space > tp->rcv_ssthresh) {
3191 free_space = tp->rcv_ssthresh;
3192 /* new window should always be an exact multiple of scaling factor
3193 *
3194 * For this case, we ALIGN "up" (increase free_space) because
3195 * we know free_space is not zero here, it has been reduced from
3196 * the memory-based limit, and rcv_ssthresh is not a hard limit
3197 * (unlike sk_rcvbuf).
3198 */
3199 free_space = ALIGN(free_space, (1 << tp->rx_opt.rcv_wscale));
3200 }
3201
3202 return free_space;
3203}
3204
3205void tcp_skb_collapse_tstamp(struct sk_buff *skb,
3206 const struct sk_buff *next_skb)
3207{
3208 if (unlikely(tcp_has_tx_tstamp(next_skb))) {
3209 const struct skb_shared_info *next_shinfo =
3210 skb_shinfo(next_skb);
3211 struct skb_shared_info *shinfo = skb_shinfo(skb);
3212
3213 shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
3214 shinfo->tskey = next_shinfo->tskey;
3215 TCP_SKB_CB(skb)->txstamp_ack |=
3216 TCP_SKB_CB(next_skb)->txstamp_ack;
3217 }
3218}
3219
3220/* Collapses two adjacent SKB's during retransmission. */
3221static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
3222{
3223 struct tcp_sock *tp = tcp_sk(sk);
3224 struct sk_buff *next_skb = skb_rb_next(skb);
3225 int next_skb_size;
3226
3227 next_skb_size = next_skb->len;
3228
3229 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
3230
3231 if (next_skb_size && !tcp_skb_shift(skb, next_skb, 1, next_skb_size))
3232 return false;
3233
3234 tcp_highest_sack_replace(sk, next_skb, skb);
3235
3236 /* Update sequence range on original skb. */
3237 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
3238
3239 /* Merge over control information. This moves PSH/FIN etc. over */
3240 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
3241
3242 /* All done, get rid of second SKB and account for it so
3243 * packet counting does not break.
3244 */
3245 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
3246 TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
3247
3248 /* changed transmit queue under us so clear hints */
3249 tcp_clear_retrans_hints_partial(tp);
3250 if (next_skb == tp->retransmit_skb_hint)
3251 tp->retransmit_skb_hint = skb;
3252
3253 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
3254
3255 tcp_skb_collapse_tstamp(skb, next_skb);
3256
3257 tcp_rtx_queue_unlink_and_free(next_skb, sk);
3258 return true;
3259}
3260
3261/* Check if coalescing SKBs is legal. */
3262static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
3263{
3264 if (tcp_skb_pcount(skb) > 1)
3265 return false;
3266 if (skb_cloned(skb))
3267 return false;
3268 if (!skb_frags_readable(skb))
3269 return false;
3270 /* Some heuristics for collapsing over SACK'd could be invented */
3271 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
3272 return false;
3273
3274 return true;
3275}
3276
3277/* Collapse packets in the retransmit queue to make to create
3278 * less packets on the wire. This is only done on retransmission.
3279 */
3280static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
3281 int space)
3282{
3283 struct tcp_sock *tp = tcp_sk(sk);
3284 struct sk_buff *skb = to, *tmp;
3285 bool first = true;
3286
3287 if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse))
3288 return;
3289 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3290 return;
3291
3292 skb_rbtree_walk_from_safe(skb, tmp) {
3293 if (!tcp_can_collapse(sk, skb))
3294 break;
3295
3296 if (!tcp_skb_can_collapse(to, skb))
3297 break;
3298
3299 space -= skb->len;
3300
3301 if (first) {
3302 first = false;
3303 continue;
3304 }
3305
3306 if (space < 0)
3307 break;
3308
3309 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
3310 break;
3311
3312 if (!tcp_collapse_retrans(sk, to))
3313 break;
3314 }
3315}
3316
3317/* This retransmits one SKB. Policy decisions and retransmit queue
3318 * state updates are done by the caller. Returns non-zero if an
3319 * error occurred which prevented the send.
3320 */
3321int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3322{
3323 struct inet_connection_sock *icsk = inet_csk(sk);
3324 struct tcp_sock *tp = tcp_sk(sk);
3325 unsigned int cur_mss;
3326 int diff, len, err;
3327 int avail_wnd;
3328
3329 /* Inconclusive MTU probe */
3330 if (icsk->icsk_mtup.probe_size)
3331 icsk->icsk_mtup.probe_size = 0;
3332
3333 if (skb_still_in_host_queue(sk, skb))
3334 return -EBUSY;
3335
3336start:
3337 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
3338 if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3339 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
3340 TCP_SKB_CB(skb)->seq++;
3341 goto start;
3342 }
3343 if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
3344 WARN_ON_ONCE(1);
3345 return -EINVAL;
3346 }
3347 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3348 return -ENOMEM;
3349 }
3350
3351 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3352 return -EHOSTUNREACH; /* Routing failure or similar. */
3353
3354 cur_mss = tcp_current_mss(sk);
3355 avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3356
3357 /* If receiver has shrunk his window, and skb is out of
3358 * new window, do not retransmit it. The exception is the
3359 * case, when window is shrunk to zero. In this case
3360 * our retransmit of one segment serves as a zero window probe.
3361 */
3362 if (avail_wnd <= 0) {
3363 if (TCP_SKB_CB(skb)->seq != tp->snd_una)
3364 return -EAGAIN;
3365 avail_wnd = cur_mss;
3366 }
3367
3368 len = cur_mss * segs;
3369 if (len > avail_wnd) {
3370 len = rounddown(avail_wnd, cur_mss);
3371 if (!len)
3372 len = avail_wnd;
3373 }
3374 if (skb->len > len) {
3375 if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
3376 cur_mss, GFP_ATOMIC))
3377 return -ENOMEM; /* We'll try again later. */
3378 } else {
3379 if (skb_unclone_keeptruesize(skb, GFP_ATOMIC))
3380 return -ENOMEM;
3381
3382 diff = tcp_skb_pcount(skb);
3383 tcp_set_skb_tso_segs(skb, cur_mss);
3384 diff -= tcp_skb_pcount(skb);
3385 if (diff)
3386 tcp_adjust_pcount(sk, skb, diff);
3387 avail_wnd = min_t(int, avail_wnd, cur_mss);
3388 if (skb->len < avail_wnd)
3389 tcp_retrans_try_collapse(sk, skb, avail_wnd);
3390 }
3391
3392 /* RFC3168, section 6.1.1.1. ECN fallback */
3393 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
3394 tcp_ecn_clear_syn(sk, skb);
3395
3396 /* Update global and local TCP statistics. */
3397 segs = tcp_skb_pcount(skb);
3398 TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
3399 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3400 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3401 tp->total_retrans += segs;
3402 tp->bytes_retrans += skb->len;
3403
3404 /* make sure skb->data is aligned on arches that require it
3405 * and check if ack-trimming & collapsing extended the headroom
3406 * beyond what csum_start can cover.
3407 */
3408 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
3409 skb_headroom(skb) >= 0xFFFF)) {
3410 struct sk_buff *nskb;
3411
3412 tcp_skb_tsorted_save(skb) {
3413 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
3414 if (nskb) {
3415 nskb->dev = NULL;
3416 err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC);
3417 } else {
3418 err = -ENOBUFS;
3419 }
3420 } tcp_skb_tsorted_restore(skb);
3421
3422 if (!err) {
3423 tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns);
3424 tcp_rate_skb_sent(sk, skb);
3425 }
3426 } else {
3427 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3428 }
3429
3430 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
3431 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
3432 TCP_SKB_CB(skb)->seq, segs, err);
3433
3434 if (likely(!err)) {
3435 trace_tcp_retransmit_skb(sk, skb);
3436 } else if (err != -EBUSY) {
3437 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
3438 }
3439
3440 /* To avoid taking spuriously low RTT samples based on a timestamp
3441 * for a transmit that never happened, always mark EVER_RETRANS
3442 */
3443 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
3444
3445 return err;
3446}
3447
3448int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3449{
3450 struct tcp_sock *tp = tcp_sk(sk);
3451 int err = __tcp_retransmit_skb(sk, skb, segs);
3452
3453 if (err == 0) {
3454#if FASTRETRANS_DEBUG > 0
3455 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
3456 net_dbg_ratelimited("retrans_out leaked\n");
3457 }
3458#endif
3459 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
3460 tp->retrans_out += tcp_skb_pcount(skb);
3461 }
3462
3463 /* Save stamp of the first (attempted) retransmit. */
3464 if (!tp->retrans_stamp)
3465 tp->retrans_stamp = tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb);
3466
3467 if (tp->undo_retrans < 0)
3468 tp->undo_retrans = 0;
3469 tp->undo_retrans += tcp_skb_pcount(skb);
3470 return err;
3471}
3472
3473/* This gets called after a retransmit timeout, and the initially
3474 * retransmitted data is acknowledged. It tries to continue
3475 * resending the rest of the retransmit queue, until either
3476 * we've sent it all or the congestion window limit is reached.
3477 */
3478void tcp_xmit_retransmit_queue(struct sock *sk)
3479{
3480 const struct inet_connection_sock *icsk = inet_csk(sk);
3481 struct sk_buff *skb, *rtx_head, *hole = NULL;
3482 struct tcp_sock *tp = tcp_sk(sk);
3483 bool rearm_timer = false;
3484 u32 max_segs;
3485 int mib_idx;
3486
3487 if (!tp->packets_out)
3488 return;
3489
3490 rtx_head = tcp_rtx_queue_head(sk);
3491 skb = tp->retransmit_skb_hint ?: rtx_head;
3492 max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
3493 skb_rbtree_walk_from(skb) {
3494 __u8 sacked;
3495 int segs;
3496
3497 if (tcp_pacing_check(sk))
3498 break;
3499
3500 /* we could do better than to assign each time */
3501 if (!hole)
3502 tp->retransmit_skb_hint = skb;
3503
3504 segs = tcp_snd_cwnd(tp) - tcp_packets_in_flight(tp);
3505 if (segs <= 0)
3506 break;
3507 sacked = TCP_SKB_CB(skb)->sacked;
3508 /* In case tcp_shift_skb_data() have aggregated large skbs,
3509 * we need to make sure not sending too bigs TSO packets
3510 */
3511 segs = min_t(int, segs, max_segs);
3512
3513 if (tp->retrans_out >= tp->lost_out) {
3514 break;
3515 } else if (!(sacked & TCPCB_LOST)) {
3516 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
3517 hole = skb;
3518 continue;
3519
3520 } else {
3521 if (icsk->icsk_ca_state != TCP_CA_Loss)
3522 mib_idx = LINUX_MIB_TCPFASTRETRANS;
3523 else
3524 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
3525 }
3526
3527 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
3528 continue;
3529
3530 if (tcp_small_queue_check(sk, skb, 1))
3531 break;
3532
3533 if (tcp_retransmit_skb(sk, skb, segs))
3534 break;
3535
3536 NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
3537
3538 if (tcp_in_cwnd_reduction(sk))
3539 tp->prr_out += tcp_skb_pcount(skb);
3540
3541 if (skb == rtx_head &&
3542 icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3543 rearm_timer = true;
3544
3545 }
3546 if (rearm_timer)
3547 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3548 inet_csk(sk)->icsk_rto,
3549 TCP_RTO_MAX);
3550}
3551
3552/* We allow to exceed memory limits for FIN packets to expedite
3553 * connection tear down and (memory) recovery.
3554 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3555 * or even be forced to close flow without any FIN.
3556 * In general, we want to allow one skb per socket to avoid hangs
3557 * with edge trigger epoll()
3558 */
3559void sk_forced_mem_schedule(struct sock *sk, int size)
3560{
3561 int delta, amt;
3562
3563 delta = size - sk->sk_forward_alloc;
3564 if (delta <= 0)
3565 return;
3566 amt = sk_mem_pages(delta);
3567 sk_forward_alloc_add(sk, amt << PAGE_SHIFT);
3568 sk_memory_allocated_add(sk, amt);
3569
3570 if (mem_cgroup_sockets_enabled && sk->sk_memcg)
3571 mem_cgroup_charge_skmem(sk->sk_memcg, amt,
3572 gfp_memcg_charge() | __GFP_NOFAIL);
3573}
3574
3575/* Send a FIN. The caller locks the socket for us.
3576 * We should try to send a FIN packet really hard, but eventually give up.
3577 */
3578void tcp_send_fin(struct sock *sk)
3579{
3580 struct sk_buff *skb, *tskb, *tail = tcp_write_queue_tail(sk);
3581 struct tcp_sock *tp = tcp_sk(sk);
3582
3583 /* Optimization, tack on the FIN if we have one skb in write queue and
3584 * this skb was not yet sent, or we are under memory pressure.
3585 * Note: in the latter case, FIN packet will be sent after a timeout,
3586 * as TCP stack thinks it has already been transmitted.
3587 */
3588 tskb = tail;
3589 if (!tskb && tcp_under_memory_pressure(sk))
3590 tskb = skb_rb_last(&sk->tcp_rtx_queue);
3591
3592 if (tskb) {
3593 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
3594 TCP_SKB_CB(tskb)->end_seq++;
3595 tp->write_seq++;
3596 if (!tail) {
3597 /* This means tskb was already sent.
3598 * Pretend we included the FIN on previous transmit.
3599 * We need to set tp->snd_nxt to the value it would have
3600 * if FIN had been sent. This is because retransmit path
3601 * does not change tp->snd_nxt.
3602 */
3603 WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1);
3604 return;
3605 }
3606 } else {
3607 skb = alloc_skb_fclone(MAX_TCP_HEADER,
3608 sk_gfp_mask(sk, GFP_ATOMIC |
3609 __GFP_NOWARN));
3610 if (unlikely(!skb))
3611 return;
3612
3613 INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3614 skb_reserve(skb, MAX_TCP_HEADER);
3615 sk_forced_mem_schedule(sk, skb->truesize);
3616 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3617 tcp_init_nondata_skb(skb, tp->write_seq,
3618 TCPHDR_ACK | TCPHDR_FIN);
3619 tcp_queue_skb(sk, skb);
3620 }
3621 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
3622}
3623
3624/* We get here when a process closes a file descriptor (either due to
3625 * an explicit close() or as a byproduct of exit()'ing) and there
3626 * was unread data in the receive queue. This behavior is recommended
3627 * by RFC 2525, section 2.17. -DaveM
3628 */
3629void tcp_send_active_reset(struct sock *sk, gfp_t priority,
3630 enum sk_rst_reason reason)
3631{
3632 struct sk_buff *skb;
3633
3634 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
3635
3636 /* NOTE: No TCP options attached and we never retransmit this. */
3637 skb = alloc_skb(MAX_TCP_HEADER, priority);
3638 if (!skb) {
3639 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3640 return;
3641 }
3642
3643 /* Reserve space for headers and prepare control bits. */
3644 skb_reserve(skb, MAX_TCP_HEADER);
3645 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
3646 TCPHDR_ACK | TCPHDR_RST);
3647 tcp_mstamp_refresh(tcp_sk(sk));
3648 /* Send it off. */
3649 if (tcp_transmit_skb(sk, skb, 0, priority))
3650 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3651
3652 /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3653 * skb here is different to the troublesome skb, so use NULL
3654 */
3655 trace_tcp_send_reset(sk, NULL, reason);
3656}
3657
3658/* Send a crossed SYN-ACK during socket establishment.
3659 * WARNING: This routine must only be called when we have already sent
3660 * a SYN packet that crossed the incoming SYN that caused this routine
3661 * to get called. If this assumption fails then the initial rcv_wnd
3662 * and rcv_wscale values will not be correct.
3663 */
3664int tcp_send_synack(struct sock *sk)
3665{
3666 struct sk_buff *skb;
3667
3668 skb = tcp_rtx_queue_head(sk);
3669 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3670 pr_err("%s: wrong queue state\n", __func__);
3671 return -EFAULT;
3672 }
3673 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
3674 if (skb_cloned(skb)) {
3675 struct sk_buff *nskb;
3676
3677 tcp_skb_tsorted_save(skb) {
3678 nskb = skb_copy(skb, GFP_ATOMIC);
3679 } tcp_skb_tsorted_restore(skb);
3680 if (!nskb)
3681 return -ENOMEM;
3682 INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3683 tcp_highest_sack_replace(sk, skb, nskb);
3684 tcp_rtx_queue_unlink_and_free(skb, sk);
3685 __skb_header_release(nskb);
3686 tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3687 sk_wmem_queued_add(sk, nskb->truesize);
3688 sk_mem_charge(sk, nskb->truesize);
3689 skb = nskb;
3690 }
3691
3692 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3693 tcp_ecn_send_synack(sk, skb);
3694 }
3695 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3696}
3697
3698/**
3699 * tcp_make_synack - Allocate one skb and build a SYNACK packet.
3700 * @sk: listener socket
3701 * @dst: dst entry attached to the SYNACK. It is consumed and caller
3702 * should not use it again.
3703 * @req: request_sock pointer
3704 * @foc: cookie for tcp fast open
3705 * @synack_type: Type of synack to prepare
3706 * @syn_skb: SYN packet just received. It could be NULL for rtx case.
3707 */
3708struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3709 struct request_sock *req,
3710 struct tcp_fastopen_cookie *foc,
3711 enum tcp_synack_type synack_type,
3712 struct sk_buff *syn_skb)
3713{
3714 struct inet_request_sock *ireq = inet_rsk(req);
3715 const struct tcp_sock *tp = tcp_sk(sk);
3716 struct tcp_out_options opts;
3717 struct tcp_key key = {};
3718 struct sk_buff *skb;
3719 int tcp_header_size;
3720 struct tcphdr *th;
3721 int mss;
3722 u64 now;
3723
3724 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3725 if (unlikely(!skb)) {
3726 dst_release(dst);
3727 return NULL;
3728 }
3729 /* Reserve space for headers. */
3730 skb_reserve(skb, MAX_TCP_HEADER);
3731
3732 switch (synack_type) {
3733 case TCP_SYNACK_NORMAL:
3734 skb_set_owner_edemux(skb, req_to_sk(req));
3735 break;
3736 case TCP_SYNACK_COOKIE:
3737 /* Under synflood, we do not attach skb to a socket,
3738 * to avoid false sharing.
3739 */
3740 break;
3741 case TCP_SYNACK_FASTOPEN:
3742 /* sk is a const pointer, because we want to express multiple
3743 * cpu might call us concurrently.
3744 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3745 */
3746 skb_set_owner_w(skb, (struct sock *)sk);
3747 break;
3748 }
3749 skb_dst_set(skb, dst);
3750
3751 mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3752
3753 memset(&opts, 0, sizeof(opts));
3754 now = tcp_clock_ns();
3755#ifdef CONFIG_SYN_COOKIES
3756 if (unlikely(synack_type == TCP_SYNACK_COOKIE && ireq->tstamp_ok))
3757 skb_set_delivery_time(skb, cookie_init_timestamp(req, now),
3758 SKB_CLOCK_MONOTONIC);
3759 else
3760#endif
3761 {
3762 skb_set_delivery_time(skb, now, SKB_CLOCK_MONOTONIC);
3763 if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */
3764 tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);
3765 }
3766
3767#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
3768 rcu_read_lock();
3769#endif
3770 if (tcp_rsk_used_ao(req)) {
3771#ifdef CONFIG_TCP_AO
3772 struct tcp_ao_key *ao_key = NULL;
3773 u8 keyid = tcp_rsk(req)->ao_keyid;
3774 u8 rnext = tcp_rsk(req)->ao_rcv_next;
3775
3776 ao_key = tcp_sk(sk)->af_specific->ao_lookup(sk, req_to_sk(req),
3777 keyid, -1);
3778 /* If there is no matching key - avoid sending anything,
3779 * especially usigned segments. It could try harder and lookup
3780 * for another peer-matching key, but the peer has requested
3781 * ao_keyid (RFC5925 RNextKeyID), so let's keep it simple here.
3782 */
3783 if (unlikely(!ao_key)) {
3784 trace_tcp_ao_synack_no_key(sk, keyid, rnext);
3785 rcu_read_unlock();
3786 kfree_skb(skb);
3787 net_warn_ratelimited("TCP-AO: the keyid %u from SYN packet is not present - not sending SYNACK\n",
3788 keyid);
3789 return NULL;
3790 }
3791 key.ao_key = ao_key;
3792 key.type = TCP_KEY_AO;
3793#endif
3794 } else {
3795#ifdef CONFIG_TCP_MD5SIG
3796 key.md5_key = tcp_rsk(req)->af_specific->req_md5_lookup(sk,
3797 req_to_sk(req));
3798 if (key.md5_key)
3799 key.type = TCP_KEY_MD5;
3800#endif
3801 }
3802 skb_set_hash(skb, READ_ONCE(tcp_rsk(req)->txhash), PKT_HASH_TYPE_L4);
3803 /* bpf program will be interested in the tcp_flags */
3804 TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK;
3805 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts,
3806 &key, foc, synack_type, syn_skb)
3807 + sizeof(*th);
3808
3809 skb_push(skb, tcp_header_size);
3810 skb_reset_transport_header(skb);
3811
3812 th = (struct tcphdr *)skb->data;
3813 memset(th, 0, sizeof(struct tcphdr));
3814 th->syn = 1;
3815 th->ack = 1;
3816 tcp_ecn_make_synack(req, th);
3817 th->source = htons(ireq->ir_num);
3818 th->dest = ireq->ir_rmt_port;
3819 skb->mark = ireq->ir_mark;
3820 skb->ip_summed = CHECKSUM_PARTIAL;
3821 th->seq = htonl(tcp_rsk(req)->snt_isn);
3822 /* XXX data is queued and acked as is. No buffer/window check */
3823 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
3824
3825 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3826 th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3827 tcp_options_write(th, NULL, tcp_rsk(req), &opts, &key);
3828 th->doff = (tcp_header_size >> 2);
3829 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3830
3831 /* Okay, we have all we need - do the md5 hash if needed */
3832 if (tcp_key_is_md5(&key)) {
3833#ifdef CONFIG_TCP_MD5SIG
3834 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3835 key.md5_key, req_to_sk(req), skb);
3836#endif
3837 } else if (tcp_key_is_ao(&key)) {
3838#ifdef CONFIG_TCP_AO
3839 tcp_rsk(req)->af_specific->ao_synack_hash(opts.hash_location,
3840 key.ao_key, req, skb,
3841 opts.hash_location - (u8 *)th, 0);
3842#endif
3843 }
3844#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
3845 rcu_read_unlock();
3846#endif
3847
3848 bpf_skops_write_hdr_opt((struct sock *)sk, skb, req, syn_skb,
3849 synack_type, &opts);
3850
3851 skb_set_delivery_time(skb, now, SKB_CLOCK_MONOTONIC);
3852 tcp_add_tx_delay(skb, tp);
3853
3854 return skb;
3855}
3856EXPORT_SYMBOL(tcp_make_synack);
3857
3858static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
3859{
3860 struct inet_connection_sock *icsk = inet_csk(sk);
3861 const struct tcp_congestion_ops *ca;
3862 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
3863
3864 if (ca_key == TCP_CA_UNSPEC)
3865 return;
3866
3867 rcu_read_lock();
3868 ca = tcp_ca_find_key(ca_key);
3869 if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
3870 bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
3871 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
3872 icsk->icsk_ca_ops = ca;
3873 }
3874 rcu_read_unlock();
3875}
3876
3877/* Do all connect socket setups that can be done AF independent. */
3878static void tcp_connect_init(struct sock *sk)
3879{
3880 const struct dst_entry *dst = __sk_dst_get(sk);
3881 struct tcp_sock *tp = tcp_sk(sk);
3882 __u8 rcv_wscale;
3883 u32 rcv_wnd;
3884
3885 /* We'll fix this up when we get a response from the other end.
3886 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3887 */
3888 tp->tcp_header_len = sizeof(struct tcphdr);
3889 if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps))
3890 tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
3891
3892 tcp_ao_connect_init(sk);
3893
3894 /* If user gave his TCP_MAXSEG, record it to clamp */
3895 if (tp->rx_opt.user_mss)
3896 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3897 tp->max_window = 0;
3898 tcp_mtup_init(sk);
3899 tcp_sync_mss(sk, dst_mtu(dst));
3900
3901 tcp_ca_dst_init(sk, dst);
3902
3903 if (!tp->window_clamp)
3904 WRITE_ONCE(tp->window_clamp, dst_metric(dst, RTAX_WINDOW));
3905 tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3906
3907 tcp_initialize_rcv_mss(sk);
3908
3909 /* limit the window selection if the user enforce a smaller rx buffer */
3910 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
3911 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
3912 WRITE_ONCE(tp->window_clamp, tcp_full_space(sk));
3913
3914 rcv_wnd = tcp_rwnd_init_bpf(sk);
3915 if (rcv_wnd == 0)
3916 rcv_wnd = dst_metric(dst, RTAX_INITRWND);
3917
3918 tcp_select_initial_window(sk, tcp_full_space(sk),
3919 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
3920 &tp->rcv_wnd,
3921 &tp->window_clamp,
3922 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_window_scaling),
3923 &rcv_wscale,
3924 rcv_wnd);
3925
3926 tp->rx_opt.rcv_wscale = rcv_wscale;
3927 tp->rcv_ssthresh = tp->rcv_wnd;
3928
3929 WRITE_ONCE(sk->sk_err, 0);
3930 sock_reset_flag(sk, SOCK_DONE);
3931 tp->snd_wnd = 0;
3932 tcp_init_wl(tp, 0);
3933 tcp_write_queue_purge(sk);
3934 tp->snd_una = tp->write_seq;
3935 tp->snd_sml = tp->write_seq;
3936 tp->snd_up = tp->write_seq;
3937 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3938
3939 if (likely(!tp->repair))
3940 tp->rcv_nxt = 0;
3941 else
3942 tp->rcv_tstamp = tcp_jiffies32;
3943 tp->rcv_wup = tp->rcv_nxt;
3944 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
3945
3946 inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3947 inet_csk(sk)->icsk_retransmits = 0;
3948 tcp_clear_retrans(tp);
3949}
3950
3951static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
3952{
3953 struct tcp_sock *tp = tcp_sk(sk);
3954 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
3955
3956 tcb->end_seq += skb->len;
3957 __skb_header_release(skb);
3958 sk_wmem_queued_add(sk, skb->truesize);
3959 sk_mem_charge(sk, skb->truesize);
3960 WRITE_ONCE(tp->write_seq, tcb->end_seq);
3961 tp->packets_out += tcp_skb_pcount(skb);
3962}
3963
3964/* Build and send a SYN with data and (cached) Fast Open cookie. However,
3965 * queue a data-only packet after the regular SYN, such that regular SYNs
3966 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3967 * only the SYN sequence, the data are retransmitted in the first ACK.
3968 * If cookie is not cached or other error occurs, falls back to send a
3969 * regular SYN with Fast Open cookie request option.
3970 */
3971static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
3972{
3973 struct inet_connection_sock *icsk = inet_csk(sk);
3974 struct tcp_sock *tp = tcp_sk(sk);
3975 struct tcp_fastopen_request *fo = tp->fastopen_req;
3976 struct page_frag *pfrag = sk_page_frag(sk);
3977 struct sk_buff *syn_data;
3978 int space, err = 0;
3979
3980 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
3981 if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3982 goto fallback;
3983
3984 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3985 * user-MSS. Reserve maximum option space for middleboxes that add
3986 * private TCP options. The cost is reduced data space in SYN :(
3987 */
3988 tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
3989 /* Sync mss_cache after updating the mss_clamp */
3990 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
3991
3992 space = __tcp_mtu_to_mss(sk, icsk->icsk_pmtu_cookie) -
3993 MAX_TCP_OPTION_SPACE;
3994
3995 space = min_t(size_t, space, fo->size);
3996
3997 if (space &&
3998 !skb_page_frag_refill(min_t(size_t, space, PAGE_SIZE),
3999 pfrag, sk->sk_allocation))
4000 goto fallback;
4001 syn_data = tcp_stream_alloc_skb(sk, sk->sk_allocation, false);
4002 if (!syn_data)
4003 goto fallback;
4004 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
4005 if (space) {
4006 space = min_t(size_t, space, pfrag->size - pfrag->offset);
4007 space = tcp_wmem_schedule(sk, space);
4008 }
4009 if (space) {
4010 space = copy_page_from_iter(pfrag->page, pfrag->offset,
4011 space, &fo->data->msg_iter);
4012 if (unlikely(!space)) {
4013 tcp_skb_tsorted_anchor_cleanup(syn_data);
4014 kfree_skb(syn_data);
4015 goto fallback;
4016 }
4017 skb_fill_page_desc(syn_data, 0, pfrag->page,
4018 pfrag->offset, space);
4019 page_ref_inc(pfrag->page);
4020 pfrag->offset += space;
4021 skb_len_add(syn_data, space);
4022 skb_zcopy_set(syn_data, fo->uarg, NULL);
4023 }
4024 /* No more data pending in inet_wait_for_connect() */
4025 if (space == fo->size)
4026 fo->data = NULL;
4027 fo->copied = space;
4028
4029 tcp_connect_queue_skb(sk, syn_data);
4030 if (syn_data->len)
4031 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
4032
4033 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
4034
4035 skb_set_delivery_time(syn, syn_data->skb_mstamp_ns, SKB_CLOCK_MONOTONIC);
4036
4037 /* Now full SYN+DATA was cloned and sent (or not),
4038 * remove the SYN from the original skb (syn_data)
4039 * we keep in write queue in case of a retransmit, as we
4040 * also have the SYN packet (with no data) in the same queue.
4041 */
4042 TCP_SKB_CB(syn_data)->seq++;
4043 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
4044 if (!err) {
4045 tp->syn_data = (fo->copied > 0);
4046 tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
4047 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
4048 goto done;
4049 }
4050
4051 /* data was not sent, put it in write_queue */
4052 __skb_queue_tail(&sk->sk_write_queue, syn_data);
4053 tp->packets_out -= tcp_skb_pcount(syn_data);
4054
4055fallback:
4056 /* Send a regular SYN with Fast Open cookie request option */
4057 if (fo->cookie.len > 0)
4058 fo->cookie.len = 0;
4059 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
4060 if (err)
4061 tp->syn_fastopen = 0;
4062done:
4063 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
4064 return err;
4065}
4066
4067/* Build a SYN and send it off. */
4068int tcp_connect(struct sock *sk)
4069{
4070 struct tcp_sock *tp = tcp_sk(sk);
4071 struct sk_buff *buff;
4072 int err;
4073
4074 tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
4075
4076#if defined(CONFIG_TCP_MD5SIG) && defined(CONFIG_TCP_AO)
4077 /* Has to be checked late, after setting daddr/saddr/ops.
4078 * Return error if the peer has both a md5 and a tcp-ao key
4079 * configured as this is ambiguous.
4080 */
4081 if (unlikely(rcu_dereference_protected(tp->md5sig_info,
4082 lockdep_sock_is_held(sk)))) {
4083 bool needs_ao = !!tp->af_specific->ao_lookup(sk, sk, -1, -1);
4084 bool needs_md5 = !!tp->af_specific->md5_lookup(sk, sk);
4085 struct tcp_ao_info *ao_info;
4086
4087 ao_info = rcu_dereference_check(tp->ao_info,
4088 lockdep_sock_is_held(sk));
4089 if (ao_info) {
4090 /* This is an extra check: tcp_ao_required() in
4091 * tcp_v{4,6}_parse_md5_keys() should prevent adding
4092 * md5 keys on ao_required socket.
4093 */
4094 needs_ao |= ao_info->ao_required;
4095 WARN_ON_ONCE(ao_info->ao_required && needs_md5);
4096 }
4097 if (needs_md5 && needs_ao)
4098 return -EKEYREJECTED;
4099
4100 /* If we have a matching md5 key and no matching tcp-ao key
4101 * then free up ao_info if allocated.
4102 */
4103 if (needs_md5) {
4104 tcp_ao_destroy_sock(sk, false);
4105 } else if (needs_ao) {
4106 tcp_clear_md5_list(sk);
4107 kfree(rcu_replace_pointer(tp->md5sig_info, NULL,
4108 lockdep_sock_is_held(sk)));
4109 }
4110 }
4111#endif
4112#ifdef CONFIG_TCP_AO
4113 if (unlikely(rcu_dereference_protected(tp->ao_info,
4114 lockdep_sock_is_held(sk)))) {
4115 /* Don't allow connecting if ao is configured but no
4116 * matching key is found.
4117 */
4118 if (!tp->af_specific->ao_lookup(sk, sk, -1, -1))
4119 return -EKEYREJECTED;
4120 }
4121#endif
4122
4123 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
4124 return -EHOSTUNREACH; /* Routing failure or similar. */
4125
4126 tcp_connect_init(sk);
4127
4128 if (unlikely(tp->repair)) {
4129 tcp_finish_connect(sk, NULL);
4130 return 0;
4131 }
4132
4133 buff = tcp_stream_alloc_skb(sk, sk->sk_allocation, true);
4134 if (unlikely(!buff))
4135 return -ENOBUFS;
4136
4137 /* SYN eats a sequence byte, write_seq updated by
4138 * tcp_connect_queue_skb().
4139 */
4140 tcp_init_nondata_skb(buff, tp->write_seq, TCPHDR_SYN);
4141 tcp_mstamp_refresh(tp);
4142 tp->retrans_stamp = tcp_time_stamp_ts(tp);
4143 tcp_connect_queue_skb(sk, buff);
4144 tcp_ecn_send_syn(sk, buff);
4145 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
4146
4147 /* Send off SYN; include data in Fast Open. */
4148 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
4149 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
4150 if (err == -ECONNREFUSED)
4151 return err;
4152
4153 /* We change tp->snd_nxt after the tcp_transmit_skb() call
4154 * in order to make this packet get counted in tcpOutSegs.
4155 */
4156 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
4157 tp->pushed_seq = tp->write_seq;
4158 buff = tcp_send_head(sk);
4159 if (unlikely(buff)) {
4160 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq);
4161 tp->pushed_seq = TCP_SKB_CB(buff)->seq;
4162 }
4163 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
4164
4165 /* Timer for repeating the SYN until an answer. */
4166 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
4167 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
4168 return 0;
4169}
4170EXPORT_SYMBOL(tcp_connect);
4171
4172u32 tcp_delack_max(const struct sock *sk)
4173{
4174 u32 delack_from_rto_min = max(tcp_rto_min(sk), 2) - 1;
4175
4176 return min(inet_csk(sk)->icsk_delack_max, delack_from_rto_min);
4177}
4178
4179/* Send out a delayed ack, the caller does the policy checking
4180 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
4181 * for details.
4182 */
4183void tcp_send_delayed_ack(struct sock *sk)
4184{
4185 struct inet_connection_sock *icsk = inet_csk(sk);
4186 int ato = icsk->icsk_ack.ato;
4187 unsigned long timeout;
4188
4189 if (ato > TCP_DELACK_MIN) {
4190 const struct tcp_sock *tp = tcp_sk(sk);
4191 int max_ato = HZ / 2;
4192
4193 if (inet_csk_in_pingpong_mode(sk) ||
4194 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
4195 max_ato = TCP_DELACK_MAX;
4196
4197 /* Slow path, intersegment interval is "high". */
4198
4199 /* If some rtt estimate is known, use it to bound delayed ack.
4200 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
4201 * directly.
4202 */
4203 if (tp->srtt_us) {
4204 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
4205 TCP_DELACK_MIN);
4206
4207 if (rtt < max_ato)
4208 max_ato = rtt;
4209 }
4210
4211 ato = min(ato, max_ato);
4212 }
4213
4214 ato = min_t(u32, ato, tcp_delack_max(sk));
4215
4216 /* Stay within the limit we were given */
4217 timeout = jiffies + ato;
4218
4219 /* Use new timeout only if there wasn't a older one earlier. */
4220 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
4221 /* If delack timer is about to expire, send ACK now. */
4222 if (time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
4223 tcp_send_ack(sk);
4224 return;
4225 }
4226
4227 if (!time_before(timeout, icsk->icsk_ack.timeout))
4228 timeout = icsk->icsk_ack.timeout;
4229 }
4230 smp_store_release(&icsk->icsk_ack.pending,
4231 icsk->icsk_ack.pending | ICSK_ACK_SCHED | ICSK_ACK_TIMER);
4232 icsk->icsk_ack.timeout = timeout;
4233 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
4234}
4235
4236/* This routine sends an ack and also updates the window. */
4237void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
4238{
4239 struct sk_buff *buff;
4240
4241 /* If we have been reset, we may not send again. */
4242 if (sk->sk_state == TCP_CLOSE)
4243 return;
4244
4245 /* We are not putting this on the write queue, so
4246 * tcp_transmit_skb() will set the ownership to this
4247 * sock.
4248 */
4249 buff = alloc_skb(MAX_TCP_HEADER,
4250 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
4251 if (unlikely(!buff)) {
4252 struct inet_connection_sock *icsk = inet_csk(sk);
4253 unsigned long delay;
4254
4255 delay = TCP_DELACK_MAX << icsk->icsk_ack.retry;
4256 if (delay < TCP_RTO_MAX)
4257 icsk->icsk_ack.retry++;
4258 inet_csk_schedule_ack(sk);
4259 icsk->icsk_ack.ato = TCP_ATO_MIN;
4260 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, delay, TCP_RTO_MAX);
4261 return;
4262 }
4263
4264 /* Reserve space for headers and prepare control bits. */
4265 skb_reserve(buff, MAX_TCP_HEADER);
4266 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
4267
4268 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
4269 * too much.
4270 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
4271 */
4272 skb_set_tcp_pure_ack(buff);
4273
4274 /* Send it off, this clears delayed acks for us. */
4275 __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
4276}
4277EXPORT_SYMBOL_GPL(__tcp_send_ack);
4278
4279void tcp_send_ack(struct sock *sk)
4280{
4281 __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
4282}
4283
4284/* This routine sends a packet with an out of date sequence
4285 * number. It assumes the other end will try to ack it.
4286 *
4287 * Question: what should we make while urgent mode?
4288 * 4.4BSD forces sending single byte of data. We cannot send
4289 * out of window data, because we have SND.NXT==SND.MAX...
4290 *
4291 * Current solution: to send TWO zero-length segments in urgent mode:
4292 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
4293 * out-of-date with SND.UNA-1 to probe window.
4294 */
4295static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
4296{
4297 struct tcp_sock *tp = tcp_sk(sk);
4298 struct sk_buff *skb;
4299
4300 /* We don't queue it, tcp_transmit_skb() sets ownership. */
4301 skb = alloc_skb(MAX_TCP_HEADER,
4302 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
4303 if (!skb)
4304 return -1;
4305
4306 /* Reserve space for headers and set control bits. */
4307 skb_reserve(skb, MAX_TCP_HEADER);
4308 /* Use a previous sequence. This should cause the other
4309 * end to send an ack. Don't queue or clone SKB, just
4310 * send it.
4311 */
4312 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
4313 NET_INC_STATS(sock_net(sk), mib);
4314 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
4315}
4316
4317/* Called from setsockopt( ... TCP_REPAIR ) */
4318void tcp_send_window_probe(struct sock *sk)
4319{
4320 if (sk->sk_state == TCP_ESTABLISHED) {
4321 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
4322 tcp_mstamp_refresh(tcp_sk(sk));
4323 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
4324 }
4325}
4326
4327/* Initiate keepalive or window probe from timer. */
4328int tcp_write_wakeup(struct sock *sk, int mib)
4329{
4330 struct tcp_sock *tp = tcp_sk(sk);
4331 struct sk_buff *skb;
4332
4333 if (sk->sk_state == TCP_CLOSE)
4334 return -1;
4335
4336 skb = tcp_send_head(sk);
4337 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
4338 int err;
4339 unsigned int mss = tcp_current_mss(sk);
4340 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
4341
4342 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
4343 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
4344
4345 /* We are probing the opening of a window
4346 * but the window size is != 0
4347 * must have been a result SWS avoidance ( sender )
4348 */
4349 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
4350 skb->len > mss) {
4351 seg_size = min(seg_size, mss);
4352 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
4353 if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
4354 skb, seg_size, mss, GFP_ATOMIC))
4355 return -1;
4356 } else if (!tcp_skb_pcount(skb))
4357 tcp_set_skb_tso_segs(skb, mss);
4358
4359 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
4360 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
4361 if (!err)
4362 tcp_event_new_data_sent(sk, skb);
4363 return err;
4364 } else {
4365 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
4366 tcp_xmit_probe_skb(sk, 1, mib);
4367 return tcp_xmit_probe_skb(sk, 0, mib);
4368 }
4369}
4370
4371/* A window probe timeout has occurred. If window is not closed send
4372 * a partial packet else a zero probe.
4373 */
4374void tcp_send_probe0(struct sock *sk)
4375{
4376 struct inet_connection_sock *icsk = inet_csk(sk);
4377 struct tcp_sock *tp = tcp_sk(sk);
4378 struct net *net = sock_net(sk);
4379 unsigned long timeout;
4380 int err;
4381
4382 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
4383
4384 if (tp->packets_out || tcp_write_queue_empty(sk)) {
4385 /* Cancel probe timer, if it is not required. */
4386 icsk->icsk_probes_out = 0;
4387 icsk->icsk_backoff = 0;
4388 icsk->icsk_probes_tstamp = 0;
4389 return;
4390 }
4391
4392 icsk->icsk_probes_out++;
4393 if (err <= 0) {
4394 if (icsk->icsk_backoff < READ_ONCE(net->ipv4.sysctl_tcp_retries2))
4395 icsk->icsk_backoff++;
4396 timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
4397 } else {
4398 /* If packet was not sent due to local congestion,
4399 * Let senders fight for local resources conservatively.
4400 */
4401 timeout = TCP_RESOURCE_PROBE_INTERVAL;
4402 }
4403
4404 timeout = tcp_clamp_probe0_to_user_timeout(sk, timeout);
4405 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX);
4406}
4407
4408int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
4409{
4410 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
4411 struct flowi fl;
4412 int res;
4413
4414 /* Paired with WRITE_ONCE() in sock_setsockopt() */
4415 if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED)
4416 WRITE_ONCE(tcp_rsk(req)->txhash, net_tx_rndhash());
4417 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL,
4418 NULL);
4419 if (!res) {
4420 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
4421 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
4422 if (unlikely(tcp_passive_fastopen(sk))) {
4423 /* sk has const attribute because listeners are lockless.
4424 * However in this case, we are dealing with a passive fastopen
4425 * socket thus we can change total_retrans value.
4426 */
4427 tcp_sk_rw(sk)->total_retrans++;
4428 }
4429 trace_tcp_retransmit_synack(sk, req);
4430 }
4431 return res;
4432}
4433EXPORT_SYMBOL(tcp_rtx_synack);