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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * Implementation of the Transmission Control Protocol(TCP).
8 *
9 * Authors: Ross Biro
10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 * Mark Evans, <evansmp@uhura.aston.ac.uk>
12 * Corey Minyard <wf-rch!minyard@relay.EU.net>
13 * Florian La Roche, <flla@stud.uni-sb.de>
14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
15 * Linus Torvalds, <torvalds@cs.helsinki.fi>
16 * Alan Cox, <gw4pts@gw4pts.ampr.org>
17 * Matthew Dillon, <dillon@apollo.west.oic.com>
18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
19 * Jorge Cwik, <jorge@laser.satlink.net>
20 */
21
22/*
23 * Changes: Pedro Roque : Retransmit queue handled by TCP.
24 * : Fragmentation on mtu decrease
25 * : Segment collapse on retransmit
26 * : AF independence
27 *
28 * Linus Torvalds : send_delayed_ack
29 * David S. Miller : Charge memory using the right skb
30 * during syn/ack processing.
31 * David S. Miller : Output engine completely rewritten.
32 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
33 * Cacophonix Gaul : draft-minshall-nagle-01
34 * J Hadi Salim : ECN support
35 *
36 */
37
38#define pr_fmt(fmt) "TCP: " fmt
39
40#include <net/tcp.h>
41
42#include <linux/compiler.h>
43#include <linux/gfp.h>
44#include <linux/module.h>
45#include <linux/static_key.h>
46
47#include <trace/events/tcp.h>
48
49/* Refresh clocks of a TCP socket,
50 * ensuring monotically increasing values.
51 */
52void tcp_mstamp_refresh(struct tcp_sock *tp)
53{
54 u64 val = tcp_clock_ns();
55
56 tp->tcp_clock_cache = val;
57 tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
58}
59
60static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
61 int push_one, gfp_t gfp);
62
63/* Account for new data that has been sent to the network. */
64static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
65{
66 struct inet_connection_sock *icsk = inet_csk(sk);
67 struct tcp_sock *tp = tcp_sk(sk);
68 unsigned int prior_packets = tp->packets_out;
69
70 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
71
72 __skb_unlink(skb, &sk->sk_write_queue);
73 tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
74
75 tp->packets_out += tcp_skb_pcount(skb);
76 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
77 tcp_rearm_rto(sk);
78
79 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
80 tcp_skb_pcount(skb));
81}
82
83/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
84 * window scaling factor due to loss of precision.
85 * If window has been shrunk, what should we make? It is not clear at all.
86 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
87 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
88 * invalid. OK, let's make this for now:
89 */
90static inline __u32 tcp_acceptable_seq(const struct sock *sk)
91{
92 const struct tcp_sock *tp = tcp_sk(sk);
93
94 if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
95 (tp->rx_opt.wscale_ok &&
96 ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
97 return tp->snd_nxt;
98 else
99 return tcp_wnd_end(tp);
100}
101
102/* Calculate mss to advertise in SYN segment.
103 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
104 *
105 * 1. It is independent of path mtu.
106 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
107 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
108 * attached devices, because some buggy hosts are confused by
109 * large MSS.
110 * 4. We do not make 3, we advertise MSS, calculated from first
111 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
112 * This may be overridden via information stored in routing table.
113 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
114 * probably even Jumbo".
115 */
116static __u16 tcp_advertise_mss(struct sock *sk)
117{
118 struct tcp_sock *tp = tcp_sk(sk);
119 const struct dst_entry *dst = __sk_dst_get(sk);
120 int mss = tp->advmss;
121
122 if (dst) {
123 unsigned int metric = dst_metric_advmss(dst);
124
125 if (metric < mss) {
126 mss = metric;
127 tp->advmss = mss;
128 }
129 }
130
131 return (__u16)mss;
132}
133
134/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
135 * This is the first part of cwnd validation mechanism.
136 */
137void tcp_cwnd_restart(struct sock *sk, s32 delta)
138{
139 struct tcp_sock *tp = tcp_sk(sk);
140 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
141 u32 cwnd = tp->snd_cwnd;
142
143 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
144
145 tp->snd_ssthresh = tcp_current_ssthresh(sk);
146 restart_cwnd = min(restart_cwnd, cwnd);
147
148 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
149 cwnd >>= 1;
150 tp->snd_cwnd = max(cwnd, restart_cwnd);
151 tp->snd_cwnd_stamp = tcp_jiffies32;
152 tp->snd_cwnd_used = 0;
153}
154
155/* Congestion state accounting after a packet has been sent. */
156static void tcp_event_data_sent(struct tcp_sock *tp,
157 struct sock *sk)
158{
159 struct inet_connection_sock *icsk = inet_csk(sk);
160 const u32 now = tcp_jiffies32;
161
162 if (tcp_packets_in_flight(tp) == 0)
163 tcp_ca_event(sk, CA_EVENT_TX_START);
164
165 /* If this is the first data packet sent in response to the
166 * previous received data,
167 * and it is a reply for ato after last received packet,
168 * increase pingpong count.
169 */
170 if (before(tp->lsndtime, icsk->icsk_ack.lrcvtime) &&
171 (u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
172 inet_csk_inc_pingpong_cnt(sk);
173
174 tp->lsndtime = now;
175}
176
177/* Account for an ACK we sent. */
178static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts,
179 u32 rcv_nxt)
180{
181 struct tcp_sock *tp = tcp_sk(sk);
182
183 if (unlikely(tp->compressed_ack > TCP_FASTRETRANS_THRESH)) {
184 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
185 tp->compressed_ack - TCP_FASTRETRANS_THRESH);
186 tp->compressed_ack = TCP_FASTRETRANS_THRESH;
187 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
188 __sock_put(sk);
189 }
190
191 if (unlikely(rcv_nxt != tp->rcv_nxt))
192 return; /* Special ACK sent by DCTCP to reflect ECN */
193 tcp_dec_quickack_mode(sk, pkts);
194 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
195}
196
197/* Determine a window scaling and initial window to offer.
198 * Based on the assumption that the given amount of space
199 * will be offered. Store the results in the tp structure.
200 * NOTE: for smooth operation initial space offering should
201 * be a multiple of mss if possible. We assume here that mss >= 1.
202 * This MUST be enforced by all callers.
203 */
204void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
205 __u32 *rcv_wnd, __u32 *window_clamp,
206 int wscale_ok, __u8 *rcv_wscale,
207 __u32 init_rcv_wnd)
208{
209 unsigned int space = (__space < 0 ? 0 : __space);
210
211 /* If no clamp set the clamp to the max possible scaled window */
212 if (*window_clamp == 0)
213 (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
214 space = min(*window_clamp, space);
215
216 /* Quantize space offering to a multiple of mss if possible. */
217 if (space > mss)
218 space = rounddown(space, mss);
219
220 /* NOTE: offering an initial window larger than 32767
221 * will break some buggy TCP stacks. If the admin tells us
222 * it is likely we could be speaking with such a buggy stack
223 * we will truncate our initial window offering to 32K-1
224 * unless the remote has sent us a window scaling option,
225 * which we interpret as a sign the remote TCP is not
226 * misinterpreting the window field as a signed quantity.
227 */
228 if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
229 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
230 else
231 (*rcv_wnd) = min_t(u32, space, U16_MAX);
232
233 if (init_rcv_wnd)
234 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
235
236 *rcv_wscale = 0;
237 if (wscale_ok) {
238 /* Set window scaling on max possible window */
239 space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
240 space = max_t(u32, space, sysctl_rmem_max);
241 space = min_t(u32, space, *window_clamp);
242 *rcv_wscale = clamp_t(int, ilog2(space) - 15,
243 0, TCP_MAX_WSCALE);
244 }
245 /* Set the clamp no higher than max representable value */
246 (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
247}
248EXPORT_SYMBOL(tcp_select_initial_window);
249
250/* Chose a new window to advertise, update state in tcp_sock for the
251 * socket, and return result with RFC1323 scaling applied. The return
252 * value can be stuffed directly into th->window for an outgoing
253 * frame.
254 */
255static u16 tcp_select_window(struct sock *sk)
256{
257 struct tcp_sock *tp = tcp_sk(sk);
258 u32 old_win = tp->rcv_wnd;
259 u32 cur_win = tcp_receive_window(tp);
260 u32 new_win = __tcp_select_window(sk);
261
262 /* Never shrink the offered window */
263 if (new_win < cur_win) {
264 /* Danger Will Robinson!
265 * Don't update rcv_wup/rcv_wnd here or else
266 * we will not be able to advertise a zero
267 * window in time. --DaveM
268 *
269 * Relax Will Robinson.
270 */
271 if (new_win == 0)
272 NET_INC_STATS(sock_net(sk),
273 LINUX_MIB_TCPWANTZEROWINDOWADV);
274 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
275 }
276 tp->rcv_wnd = new_win;
277 tp->rcv_wup = tp->rcv_nxt;
278
279 /* Make sure we do not exceed the maximum possible
280 * scaled window.
281 */
282 if (!tp->rx_opt.rcv_wscale &&
283 sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
284 new_win = min(new_win, MAX_TCP_WINDOW);
285 else
286 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
287
288 /* RFC1323 scaling applied */
289 new_win >>= tp->rx_opt.rcv_wscale;
290
291 /* If we advertise zero window, disable fast path. */
292 if (new_win == 0) {
293 tp->pred_flags = 0;
294 if (old_win)
295 NET_INC_STATS(sock_net(sk),
296 LINUX_MIB_TCPTOZEROWINDOWADV);
297 } else if (old_win == 0) {
298 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
299 }
300
301 return new_win;
302}
303
304/* Packet ECN state for a SYN-ACK */
305static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
306{
307 const struct tcp_sock *tp = tcp_sk(sk);
308
309 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
310 if (!(tp->ecn_flags & TCP_ECN_OK))
311 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
312 else if (tcp_ca_needs_ecn(sk) ||
313 tcp_bpf_ca_needs_ecn(sk))
314 INET_ECN_xmit(sk);
315}
316
317/* Packet ECN state for a SYN. */
318static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
319{
320 struct tcp_sock *tp = tcp_sk(sk);
321 bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
322 bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
323 tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
324
325 if (!use_ecn) {
326 const struct dst_entry *dst = __sk_dst_get(sk);
327
328 if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
329 use_ecn = true;
330 }
331
332 tp->ecn_flags = 0;
333
334 if (use_ecn) {
335 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
336 tp->ecn_flags = TCP_ECN_OK;
337 if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
338 INET_ECN_xmit(sk);
339 }
340}
341
342static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
343{
344 if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
345 /* tp->ecn_flags are cleared at a later point in time when
346 * SYN ACK is ultimatively being received.
347 */
348 TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
349}
350
351static void
352tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
353{
354 if (inet_rsk(req)->ecn_ok)
355 th->ece = 1;
356}
357
358/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
359 * be sent.
360 */
361static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
362 struct tcphdr *th, int tcp_header_len)
363{
364 struct tcp_sock *tp = tcp_sk(sk);
365
366 if (tp->ecn_flags & TCP_ECN_OK) {
367 /* Not-retransmitted data segment: set ECT and inject CWR. */
368 if (skb->len != tcp_header_len &&
369 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
370 INET_ECN_xmit(sk);
371 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
372 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
373 th->cwr = 1;
374 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
375 }
376 } else if (!tcp_ca_needs_ecn(sk)) {
377 /* ACK or retransmitted segment: clear ECT|CE */
378 INET_ECN_dontxmit(sk);
379 }
380 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
381 th->ece = 1;
382 }
383}
384
385/* Constructs common control bits of non-data skb. If SYN/FIN is present,
386 * auto increment end seqno.
387 */
388static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
389{
390 skb->ip_summed = CHECKSUM_PARTIAL;
391
392 TCP_SKB_CB(skb)->tcp_flags = flags;
393 TCP_SKB_CB(skb)->sacked = 0;
394
395 tcp_skb_pcount_set(skb, 1);
396
397 TCP_SKB_CB(skb)->seq = seq;
398 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
399 seq++;
400 TCP_SKB_CB(skb)->end_seq = seq;
401}
402
403static inline bool tcp_urg_mode(const struct tcp_sock *tp)
404{
405 return tp->snd_una != tp->snd_up;
406}
407
408#define OPTION_SACK_ADVERTISE (1 << 0)
409#define OPTION_TS (1 << 1)
410#define OPTION_MD5 (1 << 2)
411#define OPTION_WSCALE (1 << 3)
412#define OPTION_FAST_OPEN_COOKIE (1 << 8)
413#define OPTION_SMC (1 << 9)
414
415static void smc_options_write(__be32 *ptr, u16 *options)
416{
417#if IS_ENABLED(CONFIG_SMC)
418 if (static_branch_unlikely(&tcp_have_smc)) {
419 if (unlikely(OPTION_SMC & *options)) {
420 *ptr++ = htonl((TCPOPT_NOP << 24) |
421 (TCPOPT_NOP << 16) |
422 (TCPOPT_EXP << 8) |
423 (TCPOLEN_EXP_SMC_BASE));
424 *ptr++ = htonl(TCPOPT_SMC_MAGIC);
425 }
426 }
427#endif
428}
429
430struct tcp_out_options {
431 u16 options; /* bit field of OPTION_* */
432 u16 mss; /* 0 to disable */
433 u8 ws; /* window scale, 0 to disable */
434 u8 num_sack_blocks; /* number of SACK blocks to include */
435 u8 hash_size; /* bytes in hash_location */
436 __u8 *hash_location; /* temporary pointer, overloaded */
437 __u32 tsval, tsecr; /* need to include OPTION_TS */
438 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
439};
440
441/* Write previously computed TCP options to the packet.
442 *
443 * Beware: Something in the Internet is very sensitive to the ordering of
444 * TCP options, we learned this through the hard way, so be careful here.
445 * Luckily we can at least blame others for their non-compliance but from
446 * inter-operability perspective it seems that we're somewhat stuck with
447 * the ordering which we have been using if we want to keep working with
448 * those broken things (not that it currently hurts anybody as there isn't
449 * particular reason why the ordering would need to be changed).
450 *
451 * At least SACK_PERM as the first option is known to lead to a disaster
452 * (but it may well be that other scenarios fail similarly).
453 */
454static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
455 struct tcp_out_options *opts)
456{
457 u16 options = opts->options; /* mungable copy */
458
459 if (unlikely(OPTION_MD5 & options)) {
460 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
461 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
462 /* overload cookie hash location */
463 opts->hash_location = (__u8 *)ptr;
464 ptr += 4;
465 }
466
467 if (unlikely(opts->mss)) {
468 *ptr++ = htonl((TCPOPT_MSS << 24) |
469 (TCPOLEN_MSS << 16) |
470 opts->mss);
471 }
472
473 if (likely(OPTION_TS & options)) {
474 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
475 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
476 (TCPOLEN_SACK_PERM << 16) |
477 (TCPOPT_TIMESTAMP << 8) |
478 TCPOLEN_TIMESTAMP);
479 options &= ~OPTION_SACK_ADVERTISE;
480 } else {
481 *ptr++ = htonl((TCPOPT_NOP << 24) |
482 (TCPOPT_NOP << 16) |
483 (TCPOPT_TIMESTAMP << 8) |
484 TCPOLEN_TIMESTAMP);
485 }
486 *ptr++ = htonl(opts->tsval);
487 *ptr++ = htonl(opts->tsecr);
488 }
489
490 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
491 *ptr++ = htonl((TCPOPT_NOP << 24) |
492 (TCPOPT_NOP << 16) |
493 (TCPOPT_SACK_PERM << 8) |
494 TCPOLEN_SACK_PERM);
495 }
496
497 if (unlikely(OPTION_WSCALE & options)) {
498 *ptr++ = htonl((TCPOPT_NOP << 24) |
499 (TCPOPT_WINDOW << 16) |
500 (TCPOLEN_WINDOW << 8) |
501 opts->ws);
502 }
503
504 if (unlikely(opts->num_sack_blocks)) {
505 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
506 tp->duplicate_sack : tp->selective_acks;
507 int this_sack;
508
509 *ptr++ = htonl((TCPOPT_NOP << 24) |
510 (TCPOPT_NOP << 16) |
511 (TCPOPT_SACK << 8) |
512 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
513 TCPOLEN_SACK_PERBLOCK)));
514
515 for (this_sack = 0; this_sack < opts->num_sack_blocks;
516 ++this_sack) {
517 *ptr++ = htonl(sp[this_sack].start_seq);
518 *ptr++ = htonl(sp[this_sack].end_seq);
519 }
520
521 tp->rx_opt.dsack = 0;
522 }
523
524 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
525 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
526 u8 *p = (u8 *)ptr;
527 u32 len; /* Fast Open option length */
528
529 if (foc->exp) {
530 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
531 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
532 TCPOPT_FASTOPEN_MAGIC);
533 p += TCPOLEN_EXP_FASTOPEN_BASE;
534 } else {
535 len = TCPOLEN_FASTOPEN_BASE + foc->len;
536 *p++ = TCPOPT_FASTOPEN;
537 *p++ = len;
538 }
539
540 memcpy(p, foc->val, foc->len);
541 if ((len & 3) == 2) {
542 p[foc->len] = TCPOPT_NOP;
543 p[foc->len + 1] = TCPOPT_NOP;
544 }
545 ptr += (len + 3) >> 2;
546 }
547
548 smc_options_write(ptr, &options);
549}
550
551static void smc_set_option(const struct tcp_sock *tp,
552 struct tcp_out_options *opts,
553 unsigned int *remaining)
554{
555#if IS_ENABLED(CONFIG_SMC)
556 if (static_branch_unlikely(&tcp_have_smc)) {
557 if (tp->syn_smc) {
558 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
559 opts->options |= OPTION_SMC;
560 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
561 }
562 }
563 }
564#endif
565}
566
567static void smc_set_option_cond(const struct tcp_sock *tp,
568 const struct inet_request_sock *ireq,
569 struct tcp_out_options *opts,
570 unsigned int *remaining)
571{
572#if IS_ENABLED(CONFIG_SMC)
573 if (static_branch_unlikely(&tcp_have_smc)) {
574 if (tp->syn_smc && ireq->smc_ok) {
575 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
576 opts->options |= OPTION_SMC;
577 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
578 }
579 }
580 }
581#endif
582}
583
584/* Compute TCP options for SYN packets. This is not the final
585 * network wire format yet.
586 */
587static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
588 struct tcp_out_options *opts,
589 struct tcp_md5sig_key **md5)
590{
591 struct tcp_sock *tp = tcp_sk(sk);
592 unsigned int remaining = MAX_TCP_OPTION_SPACE;
593 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
594
595 *md5 = NULL;
596#ifdef CONFIG_TCP_MD5SIG
597 if (static_branch_unlikely(&tcp_md5_needed) &&
598 rcu_access_pointer(tp->md5sig_info)) {
599 *md5 = tp->af_specific->md5_lookup(sk, sk);
600 if (*md5) {
601 opts->options |= OPTION_MD5;
602 remaining -= TCPOLEN_MD5SIG_ALIGNED;
603 }
604 }
605#endif
606
607 /* We always get an MSS option. The option bytes which will be seen in
608 * normal data packets should timestamps be used, must be in the MSS
609 * advertised. But we subtract them from tp->mss_cache so that
610 * calculations in tcp_sendmsg are simpler etc. So account for this
611 * fact here if necessary. If we don't do this correctly, as a
612 * receiver we won't recognize data packets as being full sized when we
613 * should, and thus we won't abide by the delayed ACK rules correctly.
614 * SACKs don't matter, we never delay an ACK when we have any of those
615 * going out. */
616 opts->mss = tcp_advertise_mss(sk);
617 remaining -= TCPOLEN_MSS_ALIGNED;
618
619 if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) {
620 opts->options |= OPTION_TS;
621 opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
622 opts->tsecr = tp->rx_opt.ts_recent;
623 remaining -= TCPOLEN_TSTAMP_ALIGNED;
624 }
625 if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) {
626 opts->ws = tp->rx_opt.rcv_wscale;
627 opts->options |= OPTION_WSCALE;
628 remaining -= TCPOLEN_WSCALE_ALIGNED;
629 }
630 if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) {
631 opts->options |= OPTION_SACK_ADVERTISE;
632 if (unlikely(!(OPTION_TS & opts->options)))
633 remaining -= TCPOLEN_SACKPERM_ALIGNED;
634 }
635
636 if (fastopen && fastopen->cookie.len >= 0) {
637 u32 need = fastopen->cookie.len;
638
639 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
640 TCPOLEN_FASTOPEN_BASE;
641 need = (need + 3) & ~3U; /* Align to 32 bits */
642 if (remaining >= need) {
643 opts->options |= OPTION_FAST_OPEN_COOKIE;
644 opts->fastopen_cookie = &fastopen->cookie;
645 remaining -= need;
646 tp->syn_fastopen = 1;
647 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
648 }
649 }
650
651 smc_set_option(tp, opts, &remaining);
652
653 return MAX_TCP_OPTION_SPACE - remaining;
654}
655
656/* Set up TCP options for SYN-ACKs. */
657static unsigned int tcp_synack_options(const struct sock *sk,
658 struct request_sock *req,
659 unsigned int mss, struct sk_buff *skb,
660 struct tcp_out_options *opts,
661 const struct tcp_md5sig_key *md5,
662 struct tcp_fastopen_cookie *foc)
663{
664 struct inet_request_sock *ireq = inet_rsk(req);
665 unsigned int remaining = MAX_TCP_OPTION_SPACE;
666
667#ifdef CONFIG_TCP_MD5SIG
668 if (md5) {
669 opts->options |= OPTION_MD5;
670 remaining -= TCPOLEN_MD5SIG_ALIGNED;
671
672 /* We can't fit any SACK blocks in a packet with MD5 + TS
673 * options. There was discussion about disabling SACK
674 * rather than TS in order to fit in better with old,
675 * buggy kernels, but that was deemed to be unnecessary.
676 */
677 ireq->tstamp_ok &= !ireq->sack_ok;
678 }
679#endif
680
681 /* We always send an MSS option. */
682 opts->mss = mss;
683 remaining -= TCPOLEN_MSS_ALIGNED;
684
685 if (likely(ireq->wscale_ok)) {
686 opts->ws = ireq->rcv_wscale;
687 opts->options |= OPTION_WSCALE;
688 remaining -= TCPOLEN_WSCALE_ALIGNED;
689 }
690 if (likely(ireq->tstamp_ok)) {
691 opts->options |= OPTION_TS;
692 opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
693 opts->tsecr = req->ts_recent;
694 remaining -= TCPOLEN_TSTAMP_ALIGNED;
695 }
696 if (likely(ireq->sack_ok)) {
697 opts->options |= OPTION_SACK_ADVERTISE;
698 if (unlikely(!ireq->tstamp_ok))
699 remaining -= TCPOLEN_SACKPERM_ALIGNED;
700 }
701 if (foc != NULL && foc->len >= 0) {
702 u32 need = foc->len;
703
704 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
705 TCPOLEN_FASTOPEN_BASE;
706 need = (need + 3) & ~3U; /* Align to 32 bits */
707 if (remaining >= need) {
708 opts->options |= OPTION_FAST_OPEN_COOKIE;
709 opts->fastopen_cookie = foc;
710 remaining -= need;
711 }
712 }
713
714 smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
715
716 return MAX_TCP_OPTION_SPACE - remaining;
717}
718
719/* Compute TCP options for ESTABLISHED sockets. This is not the
720 * final wire format yet.
721 */
722static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
723 struct tcp_out_options *opts,
724 struct tcp_md5sig_key **md5)
725{
726 struct tcp_sock *tp = tcp_sk(sk);
727 unsigned int size = 0;
728 unsigned int eff_sacks;
729
730 opts->options = 0;
731
732 *md5 = NULL;
733#ifdef CONFIG_TCP_MD5SIG
734 if (static_branch_unlikely(&tcp_md5_needed) &&
735 rcu_access_pointer(tp->md5sig_info)) {
736 *md5 = tp->af_specific->md5_lookup(sk, sk);
737 if (*md5) {
738 opts->options |= OPTION_MD5;
739 size += TCPOLEN_MD5SIG_ALIGNED;
740 }
741 }
742#endif
743
744 if (likely(tp->rx_opt.tstamp_ok)) {
745 opts->options |= OPTION_TS;
746 opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
747 opts->tsecr = tp->rx_opt.ts_recent;
748 size += TCPOLEN_TSTAMP_ALIGNED;
749 }
750
751 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
752 if (unlikely(eff_sacks)) {
753 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
754 opts->num_sack_blocks =
755 min_t(unsigned int, eff_sacks,
756 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
757 TCPOLEN_SACK_PERBLOCK);
758 size += TCPOLEN_SACK_BASE_ALIGNED +
759 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
760 }
761
762 return size;
763}
764
765
766/* TCP SMALL QUEUES (TSQ)
767 *
768 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
769 * to reduce RTT and bufferbloat.
770 * We do this using a special skb destructor (tcp_wfree).
771 *
772 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
773 * needs to be reallocated in a driver.
774 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
775 *
776 * Since transmit from skb destructor is forbidden, we use a tasklet
777 * to process all sockets that eventually need to send more skbs.
778 * We use one tasklet per cpu, with its own queue of sockets.
779 */
780struct tsq_tasklet {
781 struct tasklet_struct tasklet;
782 struct list_head head; /* queue of tcp sockets */
783};
784static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
785
786static void tcp_tsq_write(struct sock *sk)
787{
788 if ((1 << sk->sk_state) &
789 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
790 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
791 struct tcp_sock *tp = tcp_sk(sk);
792
793 if (tp->lost_out > tp->retrans_out &&
794 tp->snd_cwnd > tcp_packets_in_flight(tp)) {
795 tcp_mstamp_refresh(tp);
796 tcp_xmit_retransmit_queue(sk);
797 }
798
799 tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
800 0, GFP_ATOMIC);
801 }
802}
803
804static void tcp_tsq_handler(struct sock *sk)
805{
806 bh_lock_sock(sk);
807 if (!sock_owned_by_user(sk))
808 tcp_tsq_write(sk);
809 else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
810 sock_hold(sk);
811 bh_unlock_sock(sk);
812}
813/*
814 * One tasklet per cpu tries to send more skbs.
815 * We run in tasklet context but need to disable irqs when
816 * transferring tsq->head because tcp_wfree() might
817 * interrupt us (non NAPI drivers)
818 */
819static void tcp_tasklet_func(unsigned long data)
820{
821 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
822 LIST_HEAD(list);
823 unsigned long flags;
824 struct list_head *q, *n;
825 struct tcp_sock *tp;
826 struct sock *sk;
827
828 local_irq_save(flags);
829 list_splice_init(&tsq->head, &list);
830 local_irq_restore(flags);
831
832 list_for_each_safe(q, n, &list) {
833 tp = list_entry(q, struct tcp_sock, tsq_node);
834 list_del(&tp->tsq_node);
835
836 sk = (struct sock *)tp;
837 smp_mb__before_atomic();
838 clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
839
840 tcp_tsq_handler(sk);
841 sk_free(sk);
842 }
843}
844
845#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
846 TCPF_WRITE_TIMER_DEFERRED | \
847 TCPF_DELACK_TIMER_DEFERRED | \
848 TCPF_MTU_REDUCED_DEFERRED)
849/**
850 * tcp_release_cb - tcp release_sock() callback
851 * @sk: socket
852 *
853 * called from release_sock() to perform protocol dependent
854 * actions before socket release.
855 */
856void tcp_release_cb(struct sock *sk)
857{
858 unsigned long flags, nflags;
859
860 /* perform an atomic operation only if at least one flag is set */
861 do {
862 flags = sk->sk_tsq_flags;
863 if (!(flags & TCP_DEFERRED_ALL))
864 return;
865 nflags = flags & ~TCP_DEFERRED_ALL;
866 } while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
867
868 if (flags & TCPF_TSQ_DEFERRED) {
869 tcp_tsq_write(sk);
870 __sock_put(sk);
871 }
872 /* Here begins the tricky part :
873 * We are called from release_sock() with :
874 * 1) BH disabled
875 * 2) sk_lock.slock spinlock held
876 * 3) socket owned by us (sk->sk_lock.owned == 1)
877 *
878 * But following code is meant to be called from BH handlers,
879 * so we should keep BH disabled, but early release socket ownership
880 */
881 sock_release_ownership(sk);
882
883 if (flags & TCPF_WRITE_TIMER_DEFERRED) {
884 tcp_write_timer_handler(sk);
885 __sock_put(sk);
886 }
887 if (flags & TCPF_DELACK_TIMER_DEFERRED) {
888 tcp_delack_timer_handler(sk);
889 __sock_put(sk);
890 }
891 if (flags & TCPF_MTU_REDUCED_DEFERRED) {
892 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
893 __sock_put(sk);
894 }
895}
896EXPORT_SYMBOL(tcp_release_cb);
897
898void __init tcp_tasklet_init(void)
899{
900 int i;
901
902 for_each_possible_cpu(i) {
903 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
904
905 INIT_LIST_HEAD(&tsq->head);
906 tasklet_init(&tsq->tasklet,
907 tcp_tasklet_func,
908 (unsigned long)tsq);
909 }
910}
911
912/*
913 * Write buffer destructor automatically called from kfree_skb.
914 * We can't xmit new skbs from this context, as we might already
915 * hold qdisc lock.
916 */
917void tcp_wfree(struct sk_buff *skb)
918{
919 struct sock *sk = skb->sk;
920 struct tcp_sock *tp = tcp_sk(sk);
921 unsigned long flags, nval, oval;
922
923 /* Keep one reference on sk_wmem_alloc.
924 * Will be released by sk_free() from here or tcp_tasklet_func()
925 */
926 WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
927
928 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
929 * Wait until our queues (qdisc + devices) are drained.
930 * This gives :
931 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
932 * - chance for incoming ACK (processed by another cpu maybe)
933 * to migrate this flow (skb->ooo_okay will be eventually set)
934 */
935 if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
936 goto out;
937
938 for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
939 struct tsq_tasklet *tsq;
940 bool empty;
941
942 if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
943 goto out;
944
945 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
946 nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
947 if (nval != oval)
948 continue;
949
950 /* queue this socket to tasklet queue */
951 local_irq_save(flags);
952 tsq = this_cpu_ptr(&tsq_tasklet);
953 empty = list_empty(&tsq->head);
954 list_add(&tp->tsq_node, &tsq->head);
955 if (empty)
956 tasklet_schedule(&tsq->tasklet);
957 local_irq_restore(flags);
958 return;
959 }
960out:
961 sk_free(sk);
962}
963
964/* Note: Called under soft irq.
965 * We can call TCP stack right away, unless socket is owned by user.
966 */
967enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
968{
969 struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
970 struct sock *sk = (struct sock *)tp;
971
972 tcp_tsq_handler(sk);
973 sock_put(sk);
974
975 return HRTIMER_NORESTART;
976}
977
978static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb,
979 u64 prior_wstamp)
980{
981 struct tcp_sock *tp = tcp_sk(sk);
982
983 if (sk->sk_pacing_status != SK_PACING_NONE) {
984 unsigned long rate = sk->sk_pacing_rate;
985
986 /* Original sch_fq does not pace first 10 MSS
987 * Note that tp->data_segs_out overflows after 2^32 packets,
988 * this is a minor annoyance.
989 */
990 if (rate != ~0UL && rate && tp->data_segs_out >= 10) {
991 u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate);
992 u64 credit = tp->tcp_wstamp_ns - prior_wstamp;
993
994 /* take into account OS jitter */
995 len_ns -= min_t(u64, len_ns / 2, credit);
996 tp->tcp_wstamp_ns += len_ns;
997 }
998 }
999 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
1000}
1001
1002/* This routine actually transmits TCP packets queued in by
1003 * tcp_do_sendmsg(). This is used by both the initial
1004 * transmission and possible later retransmissions.
1005 * All SKB's seen here are completely headerless. It is our
1006 * job to build the TCP header, and pass the packet down to
1007 * IP so it can do the same plus pass the packet off to the
1008 * device.
1009 *
1010 * We are working here with either a clone of the original
1011 * SKB, or a fresh unique copy made by the retransmit engine.
1012 */
1013static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
1014 int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
1015{
1016 const struct inet_connection_sock *icsk = inet_csk(sk);
1017 struct inet_sock *inet;
1018 struct tcp_sock *tp;
1019 struct tcp_skb_cb *tcb;
1020 struct tcp_out_options opts;
1021 unsigned int tcp_options_size, tcp_header_size;
1022 struct sk_buff *oskb = NULL;
1023 struct tcp_md5sig_key *md5;
1024 struct tcphdr *th;
1025 u64 prior_wstamp;
1026 int err;
1027
1028 BUG_ON(!skb || !tcp_skb_pcount(skb));
1029 tp = tcp_sk(sk);
1030 prior_wstamp = tp->tcp_wstamp_ns;
1031 tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
1032 skb->skb_mstamp_ns = tp->tcp_wstamp_ns;
1033 if (clone_it) {
1034 TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
1035 - tp->snd_una;
1036 oskb = skb;
1037
1038 tcp_skb_tsorted_save(oskb) {
1039 if (unlikely(skb_cloned(oskb)))
1040 skb = pskb_copy(oskb, gfp_mask);
1041 else
1042 skb = skb_clone(oskb, gfp_mask);
1043 } tcp_skb_tsorted_restore(oskb);
1044
1045 if (unlikely(!skb))
1046 return -ENOBUFS;
1047 }
1048
1049 inet = inet_sk(sk);
1050 tcb = TCP_SKB_CB(skb);
1051 memset(&opts, 0, sizeof(opts));
1052
1053 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
1054 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
1055 } else {
1056 tcp_options_size = tcp_established_options(sk, skb, &opts,
1057 &md5);
1058 /* Force a PSH flag on all (GSO) packets to expedite GRO flush
1059 * at receiver : This slightly improve GRO performance.
1060 * Note that we do not force the PSH flag for non GSO packets,
1061 * because they might be sent under high congestion events,
1062 * and in this case it is better to delay the delivery of 1-MSS
1063 * packets and thus the corresponding ACK packet that would
1064 * release the following packet.
1065 */
1066 if (tcp_skb_pcount(skb) > 1)
1067 tcb->tcp_flags |= TCPHDR_PSH;
1068 }
1069 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1070
1071 /* if no packet is in qdisc/device queue, then allow XPS to select
1072 * another queue. We can be called from tcp_tsq_handler()
1073 * which holds one reference to sk.
1074 *
1075 * TODO: Ideally, in-flight pure ACK packets should not matter here.
1076 * One way to get this would be to set skb->truesize = 2 on them.
1077 */
1078 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1079
1080 /* If we had to use memory reserve to allocate this skb,
1081 * this might cause drops if packet is looped back :
1082 * Other socket might not have SOCK_MEMALLOC.
1083 * Packets not looped back do not care about pfmemalloc.
1084 */
1085 skb->pfmemalloc = 0;
1086
1087 skb_push(skb, tcp_header_size);
1088 skb_reset_transport_header(skb);
1089
1090 skb_orphan(skb);
1091 skb->sk = sk;
1092 skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1093 skb_set_hash_from_sk(skb, sk);
1094 refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1095
1096 skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);
1097
1098 /* Build TCP header and checksum it. */
1099 th = (struct tcphdr *)skb->data;
1100 th->source = inet->inet_sport;
1101 th->dest = inet->inet_dport;
1102 th->seq = htonl(tcb->seq);
1103 th->ack_seq = htonl(rcv_nxt);
1104 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
1105 tcb->tcp_flags);
1106
1107 th->check = 0;
1108 th->urg_ptr = 0;
1109
1110 /* The urg_mode check is necessary during a below snd_una win probe */
1111 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
1112 if (before(tp->snd_up, tcb->seq + 0x10000)) {
1113 th->urg_ptr = htons(tp->snd_up - tcb->seq);
1114 th->urg = 1;
1115 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1116 th->urg_ptr = htons(0xFFFF);
1117 th->urg = 1;
1118 }
1119 }
1120
1121 tcp_options_write((__be32 *)(th + 1), tp, &opts);
1122 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1123 if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
1124 th->window = htons(tcp_select_window(sk));
1125 tcp_ecn_send(sk, skb, th, tcp_header_size);
1126 } else {
1127 /* RFC1323: The window in SYN & SYN/ACK segments
1128 * is never scaled.
1129 */
1130 th->window = htons(min(tp->rcv_wnd, 65535U));
1131 }
1132#ifdef CONFIG_TCP_MD5SIG
1133 /* Calculate the MD5 hash, as we have all we need now */
1134 if (md5) {
1135 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1136 tp->af_specific->calc_md5_hash(opts.hash_location,
1137 md5, sk, skb);
1138 }
1139#endif
1140
1141 icsk->icsk_af_ops->send_check(sk, skb);
1142
1143 if (likely(tcb->tcp_flags & TCPHDR_ACK))
1144 tcp_event_ack_sent(sk, tcp_skb_pcount(skb), rcv_nxt);
1145
1146 if (skb->len != tcp_header_size) {
1147 tcp_event_data_sent(tp, sk);
1148 tp->data_segs_out += tcp_skb_pcount(skb);
1149 tp->bytes_sent += skb->len - tcp_header_size;
1150 }
1151
1152 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1153 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1154 tcp_skb_pcount(skb));
1155
1156 tp->segs_out += tcp_skb_pcount(skb);
1157 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1158 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1159 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1160
1161 /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */
1162
1163 /* Cleanup our debris for IP stacks */
1164 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1165 sizeof(struct inet6_skb_parm)));
1166
1167 tcp_add_tx_delay(skb, tp);
1168
1169 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
1170
1171 if (unlikely(err > 0)) {
1172 tcp_enter_cwr(sk);
1173 err = net_xmit_eval(err);
1174 }
1175 if (!err && oskb) {
1176 tcp_update_skb_after_send(sk, oskb, prior_wstamp);
1177 tcp_rate_skb_sent(sk, oskb);
1178 }
1179 return err;
1180}
1181
1182static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
1183 gfp_t gfp_mask)
1184{
1185 return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask,
1186 tcp_sk(sk)->rcv_nxt);
1187}
1188
1189/* This routine just queues the buffer for sending.
1190 *
1191 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1192 * otherwise socket can stall.
1193 */
1194static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1195{
1196 struct tcp_sock *tp = tcp_sk(sk);
1197
1198 /* Advance write_seq and place onto the write_queue. */
1199 WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq);
1200 __skb_header_release(skb);
1201 tcp_add_write_queue_tail(sk, skb);
1202 sk_wmem_queued_add(sk, skb->truesize);
1203 sk_mem_charge(sk, skb->truesize);
1204}
1205
1206/* Initialize TSO segments for a packet. */
1207static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1208{
1209 if (skb->len <= mss_now) {
1210 /* Avoid the costly divide in the normal
1211 * non-TSO case.
1212 */
1213 tcp_skb_pcount_set(skb, 1);
1214 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1215 } else {
1216 tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1217 TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1218 }
1219}
1220
1221/* Pcount in the middle of the write queue got changed, we need to do various
1222 * tweaks to fix counters
1223 */
1224static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1225{
1226 struct tcp_sock *tp = tcp_sk(sk);
1227
1228 tp->packets_out -= decr;
1229
1230 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1231 tp->sacked_out -= decr;
1232 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1233 tp->retrans_out -= decr;
1234 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1235 tp->lost_out -= decr;
1236
1237 /* Reno case is special. Sigh... */
1238 if (tcp_is_reno(tp) && decr > 0)
1239 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1240
1241 if (tp->lost_skb_hint &&
1242 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1243 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
1244 tp->lost_cnt_hint -= decr;
1245
1246 tcp_verify_left_out(tp);
1247}
1248
1249static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
1250{
1251 return TCP_SKB_CB(skb)->txstamp_ack ||
1252 (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
1253}
1254
1255static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1256{
1257 struct skb_shared_info *shinfo = skb_shinfo(skb);
1258
1259 if (unlikely(tcp_has_tx_tstamp(skb)) &&
1260 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1261 struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1262 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1263
1264 shinfo->tx_flags &= ~tsflags;
1265 shinfo2->tx_flags |= tsflags;
1266 swap(shinfo->tskey, shinfo2->tskey);
1267 TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
1268 TCP_SKB_CB(skb)->txstamp_ack = 0;
1269 }
1270}
1271
1272static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
1273{
1274 TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
1275 TCP_SKB_CB(skb)->eor = 0;
1276}
1277
1278/* Insert buff after skb on the write or rtx queue of sk. */
1279static void tcp_insert_write_queue_after(struct sk_buff *skb,
1280 struct sk_buff *buff,
1281 struct sock *sk,
1282 enum tcp_queue tcp_queue)
1283{
1284 if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
1285 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1286 else
1287 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
1288}
1289
1290/* Function to create two new TCP segments. Shrinks the given segment
1291 * to the specified size and appends a new segment with the rest of the
1292 * packet to the list. This won't be called frequently, I hope.
1293 * Remember, these are still headerless SKBs at this point.
1294 */
1295int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1296 struct sk_buff *skb, u32 len,
1297 unsigned int mss_now, gfp_t gfp)
1298{
1299 struct tcp_sock *tp = tcp_sk(sk);
1300 struct sk_buff *buff;
1301 int nsize, old_factor;
1302 long limit;
1303 int nlen;
1304 u8 flags;
1305
1306 if (WARN_ON(len > skb->len))
1307 return -EINVAL;
1308
1309 nsize = skb_headlen(skb) - len;
1310 if (nsize < 0)
1311 nsize = 0;
1312
1313 /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb.
1314 * We need some allowance to not penalize applications setting small
1315 * SO_SNDBUF values.
1316 * Also allow first and last skb in retransmit queue to be split.
1317 */
1318 limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_MAX_SIZE);
1319 if (unlikely((sk->sk_wmem_queued >> 1) > limit &&
1320 tcp_queue != TCP_FRAG_IN_WRITE_QUEUE &&
1321 skb != tcp_rtx_queue_head(sk) &&
1322 skb != tcp_rtx_queue_tail(sk))) {
1323 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG);
1324 return -ENOMEM;
1325 }
1326
1327 if (skb_unclone(skb, gfp))
1328 return -ENOMEM;
1329
1330 /* Get a new skb... force flag on. */
1331 buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1332 if (!buff)
1333 return -ENOMEM; /* We'll just try again later. */
1334 skb_copy_decrypted(buff, skb);
1335
1336 sk_wmem_queued_add(sk, buff->truesize);
1337 sk_mem_charge(sk, buff->truesize);
1338 nlen = skb->len - len - nsize;
1339 buff->truesize += nlen;
1340 skb->truesize -= nlen;
1341
1342 /* Correct the sequence numbers. */
1343 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1344 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1345 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1346
1347 /* PSH and FIN should only be set in the second packet. */
1348 flags = TCP_SKB_CB(skb)->tcp_flags;
1349 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1350 TCP_SKB_CB(buff)->tcp_flags = flags;
1351 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1352 tcp_skb_fragment_eor(skb, buff);
1353
1354 skb_split(skb, buff, len);
1355
1356 buff->ip_summed = CHECKSUM_PARTIAL;
1357
1358 buff->tstamp = skb->tstamp;
1359 tcp_fragment_tstamp(skb, buff);
1360
1361 old_factor = tcp_skb_pcount(skb);
1362
1363 /* Fix up tso_factor for both original and new SKB. */
1364 tcp_set_skb_tso_segs(skb, mss_now);
1365 tcp_set_skb_tso_segs(buff, mss_now);
1366
1367 /* Update delivered info for the new segment */
1368 TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
1369
1370 /* If this packet has been sent out already, we must
1371 * adjust the various packet counters.
1372 */
1373 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1374 int diff = old_factor - tcp_skb_pcount(skb) -
1375 tcp_skb_pcount(buff);
1376
1377 if (diff)
1378 tcp_adjust_pcount(sk, skb, diff);
1379 }
1380
1381 /* Link BUFF into the send queue. */
1382 __skb_header_release(buff);
1383 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1384 if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
1385 list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
1386
1387 return 0;
1388}
1389
1390/* This is similar to __pskb_pull_tail(). The difference is that pulled
1391 * data is not copied, but immediately discarded.
1392 */
1393static int __pskb_trim_head(struct sk_buff *skb, int len)
1394{
1395 struct skb_shared_info *shinfo;
1396 int i, k, eat;
1397
1398 eat = min_t(int, len, skb_headlen(skb));
1399 if (eat) {
1400 __skb_pull(skb, eat);
1401 len -= eat;
1402 if (!len)
1403 return 0;
1404 }
1405 eat = len;
1406 k = 0;
1407 shinfo = skb_shinfo(skb);
1408 for (i = 0; i < shinfo->nr_frags; i++) {
1409 int size = skb_frag_size(&shinfo->frags[i]);
1410
1411 if (size <= eat) {
1412 skb_frag_unref(skb, i);
1413 eat -= size;
1414 } else {
1415 shinfo->frags[k] = shinfo->frags[i];
1416 if (eat) {
1417 skb_frag_off_add(&shinfo->frags[k], eat);
1418 skb_frag_size_sub(&shinfo->frags[k], eat);
1419 eat = 0;
1420 }
1421 k++;
1422 }
1423 }
1424 shinfo->nr_frags = k;
1425
1426 skb->data_len -= len;
1427 skb->len = skb->data_len;
1428 return len;
1429}
1430
1431/* Remove acked data from a packet in the transmit queue. */
1432int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1433{
1434 u32 delta_truesize;
1435
1436 if (skb_unclone(skb, GFP_ATOMIC))
1437 return -ENOMEM;
1438
1439 delta_truesize = __pskb_trim_head(skb, len);
1440
1441 TCP_SKB_CB(skb)->seq += len;
1442 skb->ip_summed = CHECKSUM_PARTIAL;
1443
1444 if (delta_truesize) {
1445 skb->truesize -= delta_truesize;
1446 sk_wmem_queued_add(sk, -delta_truesize);
1447 sk_mem_uncharge(sk, delta_truesize);
1448 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1449 }
1450
1451 /* Any change of skb->len requires recalculation of tso factor. */
1452 if (tcp_skb_pcount(skb) > 1)
1453 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1454
1455 return 0;
1456}
1457
1458/* Calculate MSS not accounting any TCP options. */
1459static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1460{
1461 const struct tcp_sock *tp = tcp_sk(sk);
1462 const struct inet_connection_sock *icsk = inet_csk(sk);
1463 int mss_now;
1464
1465 /* Calculate base mss without TCP options:
1466 It is MMS_S - sizeof(tcphdr) of rfc1122
1467 */
1468 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1469
1470 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1471 if (icsk->icsk_af_ops->net_frag_header_len) {
1472 const struct dst_entry *dst = __sk_dst_get(sk);
1473
1474 if (dst && dst_allfrag(dst))
1475 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1476 }
1477
1478 /* Clamp it (mss_clamp does not include tcp options) */
1479 if (mss_now > tp->rx_opt.mss_clamp)
1480 mss_now = tp->rx_opt.mss_clamp;
1481
1482 /* Now subtract optional transport overhead */
1483 mss_now -= icsk->icsk_ext_hdr_len;
1484
1485 /* Then reserve room for full set of TCP options and 8 bytes of data */
1486 mss_now = max(mss_now, sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss);
1487 return mss_now;
1488}
1489
1490/* Calculate MSS. Not accounting for SACKs here. */
1491int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1492{
1493 /* Subtract TCP options size, not including SACKs */
1494 return __tcp_mtu_to_mss(sk, pmtu) -
1495 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1496}
1497
1498/* Inverse of above */
1499int tcp_mss_to_mtu(struct sock *sk, int mss)
1500{
1501 const struct tcp_sock *tp = tcp_sk(sk);
1502 const struct inet_connection_sock *icsk = inet_csk(sk);
1503 int mtu;
1504
1505 mtu = mss +
1506 tp->tcp_header_len +
1507 icsk->icsk_ext_hdr_len +
1508 icsk->icsk_af_ops->net_header_len;
1509
1510 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1511 if (icsk->icsk_af_ops->net_frag_header_len) {
1512 const struct dst_entry *dst = __sk_dst_get(sk);
1513
1514 if (dst && dst_allfrag(dst))
1515 mtu += icsk->icsk_af_ops->net_frag_header_len;
1516 }
1517 return mtu;
1518}
1519EXPORT_SYMBOL(tcp_mss_to_mtu);
1520
1521/* MTU probing init per socket */
1522void tcp_mtup_init(struct sock *sk)
1523{
1524 struct tcp_sock *tp = tcp_sk(sk);
1525 struct inet_connection_sock *icsk = inet_csk(sk);
1526 struct net *net = sock_net(sk);
1527
1528 icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
1529 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1530 icsk->icsk_af_ops->net_header_len;
1531 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
1532 icsk->icsk_mtup.probe_size = 0;
1533 if (icsk->icsk_mtup.enabled)
1534 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1535}
1536EXPORT_SYMBOL(tcp_mtup_init);
1537
1538/* This function synchronize snd mss to current pmtu/exthdr set.
1539
1540 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1541 for TCP options, but includes only bare TCP header.
1542
1543 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1544 It is minimum of user_mss and mss received with SYN.
1545 It also does not include TCP options.
1546
1547 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1548
1549 tp->mss_cache is current effective sending mss, including
1550 all tcp options except for SACKs. It is evaluated,
1551 taking into account current pmtu, but never exceeds
1552 tp->rx_opt.mss_clamp.
1553
1554 NOTE1. rfc1122 clearly states that advertised MSS
1555 DOES NOT include either tcp or ip options.
1556
1557 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1558 are READ ONLY outside this function. --ANK (980731)
1559 */
1560unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1561{
1562 struct tcp_sock *tp = tcp_sk(sk);
1563 struct inet_connection_sock *icsk = inet_csk(sk);
1564 int mss_now;
1565
1566 if (icsk->icsk_mtup.search_high > pmtu)
1567 icsk->icsk_mtup.search_high = pmtu;
1568
1569 mss_now = tcp_mtu_to_mss(sk, pmtu);
1570 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1571
1572 /* And store cached results */
1573 icsk->icsk_pmtu_cookie = pmtu;
1574 if (icsk->icsk_mtup.enabled)
1575 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1576 tp->mss_cache = mss_now;
1577
1578 return mss_now;
1579}
1580EXPORT_SYMBOL(tcp_sync_mss);
1581
1582/* Compute the current effective MSS, taking SACKs and IP options,
1583 * and even PMTU discovery events into account.
1584 */
1585unsigned int tcp_current_mss(struct sock *sk)
1586{
1587 const struct tcp_sock *tp = tcp_sk(sk);
1588 const struct dst_entry *dst = __sk_dst_get(sk);
1589 u32 mss_now;
1590 unsigned int header_len;
1591 struct tcp_out_options opts;
1592 struct tcp_md5sig_key *md5;
1593
1594 mss_now = tp->mss_cache;
1595
1596 if (dst) {
1597 u32 mtu = dst_mtu(dst);
1598 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1599 mss_now = tcp_sync_mss(sk, mtu);
1600 }
1601
1602 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1603 sizeof(struct tcphdr);
1604 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1605 * some common options. If this is an odd packet (because we have SACK
1606 * blocks etc) then our calculated header_len will be different, and
1607 * we have to adjust mss_now correspondingly */
1608 if (header_len != tp->tcp_header_len) {
1609 int delta = (int) header_len - tp->tcp_header_len;
1610 mss_now -= delta;
1611 }
1612
1613 return mss_now;
1614}
1615
1616/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1617 * As additional protections, we do not touch cwnd in retransmission phases,
1618 * and if application hit its sndbuf limit recently.
1619 */
1620static void tcp_cwnd_application_limited(struct sock *sk)
1621{
1622 struct tcp_sock *tp = tcp_sk(sk);
1623
1624 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
1625 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
1626 /* Limited by application or receiver window. */
1627 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
1628 u32 win_used = max(tp->snd_cwnd_used, init_win);
1629 if (win_used < tp->snd_cwnd) {
1630 tp->snd_ssthresh = tcp_current_ssthresh(sk);
1631 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
1632 }
1633 tp->snd_cwnd_used = 0;
1634 }
1635 tp->snd_cwnd_stamp = tcp_jiffies32;
1636}
1637
1638static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1639{
1640 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1641 struct tcp_sock *tp = tcp_sk(sk);
1642
1643 /* Track the maximum number of outstanding packets in each
1644 * window, and remember whether we were cwnd-limited then.
1645 */
1646 if (!before(tp->snd_una, tp->max_packets_seq) ||
1647 tp->packets_out > tp->max_packets_out) {
1648 tp->max_packets_out = tp->packets_out;
1649 tp->max_packets_seq = tp->snd_nxt;
1650 tp->is_cwnd_limited = is_cwnd_limited;
1651 }
1652
1653 if (tcp_is_cwnd_limited(sk)) {
1654 /* Network is feed fully. */
1655 tp->snd_cwnd_used = 0;
1656 tp->snd_cwnd_stamp = tcp_jiffies32;
1657 } else {
1658 /* Network starves. */
1659 if (tp->packets_out > tp->snd_cwnd_used)
1660 tp->snd_cwnd_used = tp->packets_out;
1661
1662 if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle &&
1663 (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1664 !ca_ops->cong_control)
1665 tcp_cwnd_application_limited(sk);
1666
1667 /* The following conditions together indicate the starvation
1668 * is caused by insufficient sender buffer:
1669 * 1) just sent some data (see tcp_write_xmit)
1670 * 2) not cwnd limited (this else condition)
1671 * 3) no more data to send (tcp_write_queue_empty())
1672 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1673 */
1674 if (tcp_write_queue_empty(sk) && sk->sk_socket &&
1675 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
1676 (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
1677 tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1678 }
1679}
1680
1681/* Minshall's variant of the Nagle send check. */
1682static bool tcp_minshall_check(const struct tcp_sock *tp)
1683{
1684 return after(tp->snd_sml, tp->snd_una) &&
1685 !after(tp->snd_sml, tp->snd_nxt);
1686}
1687
1688/* Update snd_sml if this skb is under mss
1689 * Note that a TSO packet might end with a sub-mss segment
1690 * The test is really :
1691 * if ((skb->len % mss) != 0)
1692 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1693 * But we can avoid doing the divide again given we already have
1694 * skb_pcount = skb->len / mss_now
1695 */
1696static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1697 const struct sk_buff *skb)
1698{
1699 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1700 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1701}
1702
1703/* Return false, if packet can be sent now without violation Nagle's rules:
1704 * 1. It is full sized. (provided by caller in %partial bool)
1705 * 2. Or it contains FIN. (already checked by caller)
1706 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1707 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1708 * With Minshall's modification: all sent small packets are ACKed.
1709 */
1710static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1711 int nonagle)
1712{
1713 return partial &&
1714 ((nonagle & TCP_NAGLE_CORK) ||
1715 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1716}
1717
1718/* Return how many segs we'd like on a TSO packet,
1719 * to send one TSO packet per ms
1720 */
1721static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
1722 int min_tso_segs)
1723{
1724 u32 bytes, segs;
1725
1726 bytes = min_t(unsigned long,
1727 sk->sk_pacing_rate >> sk->sk_pacing_shift,
1728 sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);
1729
1730 /* Goal is to send at least one packet per ms,
1731 * not one big TSO packet every 100 ms.
1732 * This preserves ACK clocking and is consistent
1733 * with tcp_tso_should_defer() heuristic.
1734 */
1735 segs = max_t(u32, bytes / mss_now, min_tso_segs);
1736
1737 return segs;
1738}
1739
1740/* Return the number of segments we want in the skb we are transmitting.
1741 * See if congestion control module wants to decide; otherwise, autosize.
1742 */
1743static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
1744{
1745 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1746 u32 min_tso, tso_segs;
1747
1748 min_tso = ca_ops->min_tso_segs ?
1749 ca_ops->min_tso_segs(sk) :
1750 sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
1751
1752 tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
1753 return min_t(u32, tso_segs, sk->sk_gso_max_segs);
1754}
1755
1756/* Returns the portion of skb which can be sent right away */
1757static unsigned int tcp_mss_split_point(const struct sock *sk,
1758 const struct sk_buff *skb,
1759 unsigned int mss_now,
1760 unsigned int max_segs,
1761 int nonagle)
1762{
1763 const struct tcp_sock *tp = tcp_sk(sk);
1764 u32 partial, needed, window, max_len;
1765
1766 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1767 max_len = mss_now * max_segs;
1768
1769 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1770 return max_len;
1771
1772 needed = min(skb->len, window);
1773
1774 if (max_len <= needed)
1775 return max_len;
1776
1777 partial = needed % mss_now;
1778 /* If last segment is not a full MSS, check if Nagle rules allow us
1779 * to include this last segment in this skb.
1780 * Otherwise, we'll split the skb at last MSS boundary
1781 */
1782 if (tcp_nagle_check(partial != 0, tp, nonagle))
1783 return needed - partial;
1784
1785 return needed;
1786}
1787
1788/* Can at least one segment of SKB be sent right now, according to the
1789 * congestion window rules? If so, return how many segments are allowed.
1790 */
1791static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1792 const struct sk_buff *skb)
1793{
1794 u32 in_flight, cwnd, halfcwnd;
1795
1796 /* Don't be strict about the congestion window for the final FIN. */
1797 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1798 tcp_skb_pcount(skb) == 1)
1799 return 1;
1800
1801 in_flight = tcp_packets_in_flight(tp);
1802 cwnd = tp->snd_cwnd;
1803 if (in_flight >= cwnd)
1804 return 0;
1805
1806 /* For better scheduling, ensure we have at least
1807 * 2 GSO packets in flight.
1808 */
1809 halfcwnd = max(cwnd >> 1, 1U);
1810 return min(halfcwnd, cwnd - in_flight);
1811}
1812
1813/* Initialize TSO state of a skb.
1814 * This must be invoked the first time we consider transmitting
1815 * SKB onto the wire.
1816 */
1817static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1818{
1819 int tso_segs = tcp_skb_pcount(skb);
1820
1821 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1822 tcp_set_skb_tso_segs(skb, mss_now);
1823 tso_segs = tcp_skb_pcount(skb);
1824 }
1825 return tso_segs;
1826}
1827
1828
1829/* Return true if the Nagle test allows this packet to be
1830 * sent now.
1831 */
1832static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1833 unsigned int cur_mss, int nonagle)
1834{
1835 /* Nagle rule does not apply to frames, which sit in the middle of the
1836 * write_queue (they have no chances to get new data).
1837 *
1838 * This is implemented in the callers, where they modify the 'nonagle'
1839 * argument based upon the location of SKB in the send queue.
1840 */
1841 if (nonagle & TCP_NAGLE_PUSH)
1842 return true;
1843
1844 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1845 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1846 return true;
1847
1848 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
1849 return true;
1850
1851 return false;
1852}
1853
1854/* Does at least the first segment of SKB fit into the send window? */
1855static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1856 const struct sk_buff *skb,
1857 unsigned int cur_mss)
1858{
1859 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1860
1861 if (skb->len > cur_mss)
1862 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1863
1864 return !after(end_seq, tcp_wnd_end(tp));
1865}
1866
1867/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1868 * which is put after SKB on the list. It is very much like
1869 * tcp_fragment() except that it may make several kinds of assumptions
1870 * in order to speed up the splitting operation. In particular, we
1871 * know that all the data is in scatter-gather pages, and that the
1872 * packet has never been sent out before (and thus is not cloned).
1873 */
1874static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1875 unsigned int mss_now, gfp_t gfp)
1876{
1877 int nlen = skb->len - len;
1878 struct sk_buff *buff;
1879 u8 flags;
1880
1881 /* All of a TSO frame must be composed of paged data. */
1882 if (skb->len != skb->data_len)
1883 return tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
1884 skb, len, mss_now, gfp);
1885
1886 buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1887 if (unlikely(!buff))
1888 return -ENOMEM;
1889 skb_copy_decrypted(buff, skb);
1890
1891 sk_wmem_queued_add(sk, buff->truesize);
1892 sk_mem_charge(sk, buff->truesize);
1893 buff->truesize += nlen;
1894 skb->truesize -= nlen;
1895
1896 /* Correct the sequence numbers. */
1897 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1898 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1899 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1900
1901 /* PSH and FIN should only be set in the second packet. */
1902 flags = TCP_SKB_CB(skb)->tcp_flags;
1903 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1904 TCP_SKB_CB(buff)->tcp_flags = flags;
1905
1906 /* This packet was never sent out yet, so no SACK bits. */
1907 TCP_SKB_CB(buff)->sacked = 0;
1908
1909 tcp_skb_fragment_eor(skb, buff);
1910
1911 buff->ip_summed = CHECKSUM_PARTIAL;
1912 skb_split(skb, buff, len);
1913 tcp_fragment_tstamp(skb, buff);
1914
1915 /* Fix up tso_factor for both original and new SKB. */
1916 tcp_set_skb_tso_segs(skb, mss_now);
1917 tcp_set_skb_tso_segs(buff, mss_now);
1918
1919 /* Link BUFF into the send queue. */
1920 __skb_header_release(buff);
1921 tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE);
1922
1923 return 0;
1924}
1925
1926/* Try to defer sending, if possible, in order to minimize the amount
1927 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1928 *
1929 * This algorithm is from John Heffner.
1930 */
1931static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
1932 bool *is_cwnd_limited,
1933 bool *is_rwnd_limited,
1934 u32 max_segs)
1935{
1936 const struct inet_connection_sock *icsk = inet_csk(sk);
1937 u32 send_win, cong_win, limit, in_flight;
1938 struct tcp_sock *tp = tcp_sk(sk);
1939 struct sk_buff *head;
1940 int win_divisor;
1941 s64 delta;
1942
1943 if (icsk->icsk_ca_state >= TCP_CA_Recovery)
1944 goto send_now;
1945
1946 /* Avoid bursty behavior by allowing defer
1947 * only if the last write was recent (1 ms).
1948 * Note that tp->tcp_wstamp_ns can be in the future if we have
1949 * packets waiting in a qdisc or device for EDT delivery.
1950 */
1951 delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC;
1952 if (delta > 0)
1953 goto send_now;
1954
1955 in_flight = tcp_packets_in_flight(tp);
1956
1957 BUG_ON(tcp_skb_pcount(skb) <= 1);
1958 BUG_ON(tp->snd_cwnd <= in_flight);
1959
1960 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1961
1962 /* From in_flight test above, we know that cwnd > in_flight. */
1963 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1964
1965 limit = min(send_win, cong_win);
1966
1967 /* If a full-sized TSO skb can be sent, do it. */
1968 if (limit >= max_segs * tp->mss_cache)
1969 goto send_now;
1970
1971 /* Middle in queue won't get any more data, full sendable already? */
1972 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
1973 goto send_now;
1974
1975 win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
1976 if (win_divisor) {
1977 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1978
1979 /* If at least some fraction of a window is available,
1980 * just use it.
1981 */
1982 chunk /= win_divisor;
1983 if (limit >= chunk)
1984 goto send_now;
1985 } else {
1986 /* Different approach, try not to defer past a single
1987 * ACK. Receiver should ACK every other full sized
1988 * frame, so if we have space for more than 3 frames
1989 * then send now.
1990 */
1991 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
1992 goto send_now;
1993 }
1994
1995 /* TODO : use tsorted_sent_queue ? */
1996 head = tcp_rtx_queue_head(sk);
1997 if (!head)
1998 goto send_now;
1999 delta = tp->tcp_clock_cache - head->tstamp;
2000 /* If next ACK is likely to come too late (half srtt), do not defer */
2001 if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0)
2002 goto send_now;
2003
2004 /* Ok, it looks like it is advisable to defer.
2005 * Three cases are tracked :
2006 * 1) We are cwnd-limited
2007 * 2) We are rwnd-limited
2008 * 3) We are application limited.
2009 */
2010 if (cong_win < send_win) {
2011 if (cong_win <= skb->len) {
2012 *is_cwnd_limited = true;
2013 return true;
2014 }
2015 } else {
2016 if (send_win <= skb->len) {
2017 *is_rwnd_limited = true;
2018 return true;
2019 }
2020 }
2021
2022 /* If this packet won't get more data, do not wait. */
2023 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
2024 TCP_SKB_CB(skb)->eor)
2025 goto send_now;
2026
2027 return true;
2028
2029send_now:
2030 return false;
2031}
2032
2033static inline void tcp_mtu_check_reprobe(struct sock *sk)
2034{
2035 struct inet_connection_sock *icsk = inet_csk(sk);
2036 struct tcp_sock *tp = tcp_sk(sk);
2037 struct net *net = sock_net(sk);
2038 u32 interval;
2039 s32 delta;
2040
2041 interval = net->ipv4.sysctl_tcp_probe_interval;
2042 delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2043 if (unlikely(delta >= interval * HZ)) {
2044 int mss = tcp_current_mss(sk);
2045
2046 /* Update current search range */
2047 icsk->icsk_mtup.probe_size = 0;
2048 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
2049 sizeof(struct tcphdr) +
2050 icsk->icsk_af_ops->net_header_len;
2051 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
2052
2053 /* Update probe time stamp */
2054 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2055 }
2056}
2057
2058static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
2059{
2060 struct sk_buff *skb, *next;
2061
2062 skb = tcp_send_head(sk);
2063 tcp_for_write_queue_from_safe(skb, next, sk) {
2064 if (len <= skb->len)
2065 break;
2066
2067 if (unlikely(TCP_SKB_CB(skb)->eor) || tcp_has_tx_tstamp(skb))
2068 return false;
2069
2070 len -= skb->len;
2071 }
2072
2073 return true;
2074}
2075
2076/* Create a new MTU probe if we are ready.
2077 * MTU probe is regularly attempting to increase the path MTU by
2078 * deliberately sending larger packets. This discovers routing
2079 * changes resulting in larger path MTUs.
2080 *
2081 * Returns 0 if we should wait to probe (no cwnd available),
2082 * 1 if a probe was sent,
2083 * -1 otherwise
2084 */
2085static int tcp_mtu_probe(struct sock *sk)
2086{
2087 struct inet_connection_sock *icsk = inet_csk(sk);
2088 struct tcp_sock *tp = tcp_sk(sk);
2089 struct sk_buff *skb, *nskb, *next;
2090 struct net *net = sock_net(sk);
2091 int probe_size;
2092 int size_needed;
2093 int copy, len;
2094 int mss_now;
2095 int interval;
2096
2097 /* Not currently probing/verifying,
2098 * not in recovery,
2099 * have enough cwnd, and
2100 * not SACKing (the variable headers throw things off)
2101 */
2102 if (likely(!icsk->icsk_mtup.enabled ||
2103 icsk->icsk_mtup.probe_size ||
2104 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
2105 tp->snd_cwnd < 11 ||
2106 tp->rx_opt.num_sacks || tp->rx_opt.dsack))
2107 return -1;
2108
2109 /* Use binary search for probe_size between tcp_mss_base,
2110 * and current mss_clamp. if (search_high - search_low)
2111 * smaller than a threshold, backoff from probing.
2112 */
2113 mss_now = tcp_current_mss(sk);
2114 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
2115 icsk->icsk_mtup.search_low) >> 1);
2116 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2117 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2118 /* When misfortune happens, we are reprobing actively,
2119 * and then reprobe timer has expired. We stick with current
2120 * probing process by not resetting search range to its orignal.
2121 */
2122 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2123 interval < net->ipv4.sysctl_tcp_probe_threshold) {
2124 /* Check whether enough time has elaplased for
2125 * another round of probing.
2126 */
2127 tcp_mtu_check_reprobe(sk);
2128 return -1;
2129 }
2130
2131 /* Have enough data in the send queue to probe? */
2132 if (tp->write_seq - tp->snd_nxt < size_needed)
2133 return -1;
2134
2135 if (tp->snd_wnd < size_needed)
2136 return -1;
2137 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2138 return 0;
2139
2140 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2141 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
2142 if (!tcp_packets_in_flight(tp))
2143 return -1;
2144 else
2145 return 0;
2146 }
2147
2148 if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
2149 return -1;
2150
2151 /* We're allowed to probe. Build it now. */
2152 nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2153 if (!nskb)
2154 return -1;
2155 sk_wmem_queued_add(sk, nskb->truesize);
2156 sk_mem_charge(sk, nskb->truesize);
2157
2158 skb = tcp_send_head(sk);
2159 skb_copy_decrypted(nskb, skb);
2160
2161 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
2162 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
2163 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
2164 TCP_SKB_CB(nskb)->sacked = 0;
2165 nskb->csum = 0;
2166 nskb->ip_summed = CHECKSUM_PARTIAL;
2167
2168 tcp_insert_write_queue_before(nskb, skb, sk);
2169 tcp_highest_sack_replace(sk, skb, nskb);
2170
2171 len = 0;
2172 tcp_for_write_queue_from_safe(skb, next, sk) {
2173 copy = min_t(int, skb->len, probe_size - len);
2174 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2175
2176 if (skb->len <= copy) {
2177 /* We've eaten all the data from this skb.
2178 * Throw it away. */
2179 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2180 /* If this is the last SKB we copy and eor is set
2181 * we need to propagate it to the new skb.
2182 */
2183 TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
2184 tcp_skb_collapse_tstamp(nskb, skb);
2185 tcp_unlink_write_queue(skb, sk);
2186 sk_wmem_free_skb(sk, skb);
2187 } else {
2188 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
2189 ~(TCPHDR_FIN|TCPHDR_PSH);
2190 if (!skb_shinfo(skb)->nr_frags) {
2191 skb_pull(skb, copy);
2192 } else {
2193 __pskb_trim_head(skb, copy);
2194 tcp_set_skb_tso_segs(skb, mss_now);
2195 }
2196 TCP_SKB_CB(skb)->seq += copy;
2197 }
2198
2199 len += copy;
2200
2201 if (len >= probe_size)
2202 break;
2203 }
2204 tcp_init_tso_segs(nskb, nskb->len);
2205
2206 /* We're ready to send. If this fails, the probe will
2207 * be resegmented into mss-sized pieces by tcp_write_xmit().
2208 */
2209 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
2210 /* Decrement cwnd here because we are sending
2211 * effectively two packets. */
2212 tp->snd_cwnd--;
2213 tcp_event_new_data_sent(sk, nskb);
2214
2215 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2216 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
2217 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
2218
2219 return 1;
2220 }
2221
2222 return -1;
2223}
2224
2225static bool tcp_pacing_check(struct sock *sk)
2226{
2227 struct tcp_sock *tp = tcp_sk(sk);
2228
2229 if (!tcp_needs_internal_pacing(sk))
2230 return false;
2231
2232 if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache)
2233 return false;
2234
2235 if (!hrtimer_is_queued(&tp->pacing_timer)) {
2236 hrtimer_start(&tp->pacing_timer,
2237 ns_to_ktime(tp->tcp_wstamp_ns),
2238 HRTIMER_MODE_ABS_PINNED_SOFT);
2239 sock_hold(sk);
2240 }
2241 return true;
2242}
2243
2244/* TCP Small Queues :
2245 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2246 * (These limits are doubled for retransmits)
2247 * This allows for :
2248 * - better RTT estimation and ACK scheduling
2249 * - faster recovery
2250 * - high rates
2251 * Alas, some drivers / subsystems require a fair amount
2252 * of queued bytes to ensure line rate.
2253 * One example is wifi aggregation (802.11 AMPDU)
2254 */
2255static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
2256 unsigned int factor)
2257{
2258 unsigned long limit;
2259
2260 limit = max_t(unsigned long,
2261 2 * skb->truesize,
2262 sk->sk_pacing_rate >> sk->sk_pacing_shift);
2263 if (sk->sk_pacing_status == SK_PACING_NONE)
2264 limit = min_t(unsigned long, limit,
2265 sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
2266 limit <<= factor;
2267
2268 if (static_branch_unlikely(&tcp_tx_delay_enabled) &&
2269 tcp_sk(sk)->tcp_tx_delay) {
2270 u64 extra_bytes = (u64)sk->sk_pacing_rate * tcp_sk(sk)->tcp_tx_delay;
2271
2272 /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we
2273 * approximate our needs assuming an ~100% skb->truesize overhead.
2274 * USEC_PER_SEC is approximated by 2^20.
2275 * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift.
2276 */
2277 extra_bytes >>= (20 - 1);
2278 limit += extra_bytes;
2279 }
2280 if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2281 /* Always send skb if rtx queue is empty.
2282 * No need to wait for TX completion to call us back,
2283 * after softirq/tasklet schedule.
2284 * This helps when TX completions are delayed too much.
2285 */
2286 if (tcp_rtx_queue_empty(sk))
2287 return false;
2288
2289 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2290 /* It is possible TX completion already happened
2291 * before we set TSQ_THROTTLED, so we must
2292 * test again the condition.
2293 */
2294 smp_mb__after_atomic();
2295 if (refcount_read(&sk->sk_wmem_alloc) > limit)
2296 return true;
2297 }
2298 return false;
2299}
2300
2301static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
2302{
2303 const u32 now = tcp_jiffies32;
2304 enum tcp_chrono old = tp->chrono_type;
2305
2306 if (old > TCP_CHRONO_UNSPEC)
2307 tp->chrono_stat[old - 1] += now - tp->chrono_start;
2308 tp->chrono_start = now;
2309 tp->chrono_type = new;
2310}
2311
2312void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
2313{
2314 struct tcp_sock *tp = tcp_sk(sk);
2315
2316 /* If there are multiple conditions worthy of tracking in a
2317 * chronograph then the highest priority enum takes precedence
2318 * over the other conditions. So that if something "more interesting"
2319 * starts happening, stop the previous chrono and start a new one.
2320 */
2321 if (type > tp->chrono_type)
2322 tcp_chrono_set(tp, type);
2323}
2324
2325void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
2326{
2327 struct tcp_sock *tp = tcp_sk(sk);
2328
2329
2330 /* There are multiple conditions worthy of tracking in a
2331 * chronograph, so that the highest priority enum takes
2332 * precedence over the other conditions (see tcp_chrono_start).
2333 * If a condition stops, we only stop chrono tracking if
2334 * it's the "most interesting" or current chrono we are
2335 * tracking and starts busy chrono if we have pending data.
2336 */
2337 if (tcp_rtx_and_write_queues_empty(sk))
2338 tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
2339 else if (type == tp->chrono_type)
2340 tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2341}
2342
2343/* This routine writes packets to the network. It advances the
2344 * send_head. This happens as incoming acks open up the remote
2345 * window for us.
2346 *
2347 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2348 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2349 * account rare use of URG, this is not a big flaw.
2350 *
2351 * Send at most one packet when push_one > 0. Temporarily ignore
2352 * cwnd limit to force at most one packet out when push_one == 2.
2353
2354 * Returns true, if no segments are in flight and we have queued segments,
2355 * but cannot send anything now because of SWS or another problem.
2356 */
2357static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2358 int push_one, gfp_t gfp)
2359{
2360 struct tcp_sock *tp = tcp_sk(sk);
2361 struct sk_buff *skb;
2362 unsigned int tso_segs, sent_pkts;
2363 int cwnd_quota;
2364 int result;
2365 bool is_cwnd_limited = false, is_rwnd_limited = false;
2366 u32 max_segs;
2367
2368 sent_pkts = 0;
2369
2370 tcp_mstamp_refresh(tp);
2371 if (!push_one) {
2372 /* Do MTU probing. */
2373 result = tcp_mtu_probe(sk);
2374 if (!result) {
2375 return false;
2376 } else if (result > 0) {
2377 sent_pkts = 1;
2378 }
2379 }
2380
2381 max_segs = tcp_tso_segs(sk, mss_now);
2382 while ((skb = tcp_send_head(sk))) {
2383 unsigned int limit;
2384
2385 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2386 /* "skb_mstamp_ns" is used as a start point for the retransmit timer */
2387 skb->skb_mstamp_ns = tp->tcp_wstamp_ns = tp->tcp_clock_cache;
2388 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
2389 tcp_init_tso_segs(skb, mss_now);
2390 goto repair; /* Skip network transmission */
2391 }
2392
2393 if (tcp_pacing_check(sk))
2394 break;
2395
2396 tso_segs = tcp_init_tso_segs(skb, mss_now);
2397 BUG_ON(!tso_segs);
2398
2399 cwnd_quota = tcp_cwnd_test(tp, skb);
2400 if (!cwnd_quota) {
2401 if (push_one == 2)
2402 /* Force out a loss probe pkt. */
2403 cwnd_quota = 1;
2404 else
2405 break;
2406 }
2407
2408 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
2409 is_rwnd_limited = true;
2410 break;
2411 }
2412
2413 if (tso_segs == 1) {
2414 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2415 (tcp_skb_is_last(sk, skb) ?
2416 nonagle : TCP_NAGLE_PUSH))))
2417 break;
2418 } else {
2419 if (!push_one &&
2420 tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2421 &is_rwnd_limited, max_segs))
2422 break;
2423 }
2424
2425 limit = mss_now;
2426 if (tso_segs > 1 && !tcp_urg_mode(tp))
2427 limit = tcp_mss_split_point(sk, skb, mss_now,
2428 min_t(unsigned int,
2429 cwnd_quota,
2430 max_segs),
2431 nonagle);
2432
2433 if (skb->len > limit &&
2434 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
2435 break;
2436
2437 if (tcp_small_queue_check(sk, skb, 0))
2438 break;
2439
2440 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2441 break;
2442
2443repair:
2444 /* Advance the send_head. This one is sent out.
2445 * This call will increment packets_out.
2446 */
2447 tcp_event_new_data_sent(sk, skb);
2448
2449 tcp_minshall_update(tp, mss_now, skb);
2450 sent_pkts += tcp_skb_pcount(skb);
2451
2452 if (push_one)
2453 break;
2454 }
2455
2456 if (is_rwnd_limited)
2457 tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
2458 else
2459 tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
2460
2461 if (likely(sent_pkts)) {
2462 if (tcp_in_cwnd_reduction(sk))
2463 tp->prr_out += sent_pkts;
2464
2465 /* Send one loss probe per tail loss episode. */
2466 if (push_one != 2)
2467 tcp_schedule_loss_probe(sk, false);
2468 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2469 tcp_cwnd_validate(sk, is_cwnd_limited);
2470 return false;
2471 }
2472 return !tp->packets_out && !tcp_write_queue_empty(sk);
2473}
2474
2475bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
2476{
2477 struct inet_connection_sock *icsk = inet_csk(sk);
2478 struct tcp_sock *tp = tcp_sk(sk);
2479 u32 timeout, rto_delta_us;
2480 int early_retrans;
2481
2482 /* Don't do any loss probe on a Fast Open connection before 3WHS
2483 * finishes.
2484 */
2485 if (rcu_access_pointer(tp->fastopen_rsk))
2486 return false;
2487
2488 early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
2489 /* Schedule a loss probe in 2*RTT for SACK capable connections
2490 * not in loss recovery, that are either limited by cwnd or application.
2491 */
2492 if ((early_retrans != 3 && early_retrans != 4) ||
2493 !tp->packets_out || !tcp_is_sack(tp) ||
2494 (icsk->icsk_ca_state != TCP_CA_Open &&
2495 icsk->icsk_ca_state != TCP_CA_CWR))
2496 return false;
2497
2498 /* Probe timeout is 2*rtt. Add minimum RTO to account
2499 * for delayed ack when there's one outstanding packet. If no RTT
2500 * sample is available then probe after TCP_TIMEOUT_INIT.
2501 */
2502 if (tp->srtt_us) {
2503 timeout = usecs_to_jiffies(tp->srtt_us >> 2);
2504 if (tp->packets_out == 1)
2505 timeout += TCP_RTO_MIN;
2506 else
2507 timeout += TCP_TIMEOUT_MIN;
2508 } else {
2509 timeout = TCP_TIMEOUT_INIT;
2510 }
2511
2512 /* If the RTO formula yields an earlier time, then use that time. */
2513 rto_delta_us = advancing_rto ?
2514 jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
2515 tcp_rto_delta_us(sk); /* How far in future is RTO? */
2516 if (rto_delta_us > 0)
2517 timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
2518
2519 tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
2520 TCP_RTO_MAX, NULL);
2521 return true;
2522}
2523
2524/* Thanks to skb fast clones, we can detect if a prior transmit of
2525 * a packet is still in a qdisc or driver queue.
2526 * In this case, there is very little point doing a retransmit !
2527 */
2528static bool skb_still_in_host_queue(const struct sock *sk,
2529 const struct sk_buff *skb)
2530{
2531 if (unlikely(skb_fclone_busy(sk, skb))) {
2532 NET_INC_STATS(sock_net(sk),
2533 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2534 return true;
2535 }
2536 return false;
2537}
2538
2539/* When probe timeout (PTO) fires, try send a new segment if possible, else
2540 * retransmit the last segment.
2541 */
2542void tcp_send_loss_probe(struct sock *sk)
2543{
2544 struct tcp_sock *tp = tcp_sk(sk);
2545 struct sk_buff *skb;
2546 int pcount;
2547 int mss = tcp_current_mss(sk);
2548
2549 skb = tcp_send_head(sk);
2550 if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
2551 pcount = tp->packets_out;
2552 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2553 if (tp->packets_out > pcount)
2554 goto probe_sent;
2555 goto rearm_timer;
2556 }
2557 skb = skb_rb_last(&sk->tcp_rtx_queue);
2558 if (unlikely(!skb)) {
2559 WARN_ONCE(tp->packets_out,
2560 "invalid inflight: %u state %u cwnd %u mss %d\n",
2561 tp->packets_out, sk->sk_state, tp->snd_cwnd, mss);
2562 inet_csk(sk)->icsk_pending = 0;
2563 return;
2564 }
2565
2566 /* At most one outstanding TLP retransmission. */
2567 if (tp->tlp_high_seq)
2568 goto rearm_timer;
2569
2570 if (skb_still_in_host_queue(sk, skb))
2571 goto rearm_timer;
2572
2573 pcount = tcp_skb_pcount(skb);
2574 if (WARN_ON(!pcount))
2575 goto rearm_timer;
2576
2577 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2578 if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
2579 (pcount - 1) * mss, mss,
2580 GFP_ATOMIC)))
2581 goto rearm_timer;
2582 skb = skb_rb_next(skb);
2583 }
2584
2585 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2586 goto rearm_timer;
2587
2588 if (__tcp_retransmit_skb(sk, skb, 1))
2589 goto rearm_timer;
2590
2591 /* Record snd_nxt for loss detection. */
2592 tp->tlp_high_seq = tp->snd_nxt;
2593
2594probe_sent:
2595 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2596 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2597 inet_csk(sk)->icsk_pending = 0;
2598rearm_timer:
2599 tcp_rearm_rto(sk);
2600}
2601
2602/* Push out any pending frames which were held back due to
2603 * TCP_CORK or attempt at coalescing tiny packets.
2604 * The socket must be locked by the caller.
2605 */
2606void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2607 int nonagle)
2608{
2609 /* If we are closed, the bytes will have to remain here.
2610 * In time closedown will finish, we empty the write queue and
2611 * all will be happy.
2612 */
2613 if (unlikely(sk->sk_state == TCP_CLOSE))
2614 return;
2615
2616 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2617 sk_gfp_mask(sk, GFP_ATOMIC)))
2618 tcp_check_probe_timer(sk);
2619}
2620
2621/* Send _single_ skb sitting at the send head. This function requires
2622 * true push pending frames to setup probe timer etc.
2623 */
2624void tcp_push_one(struct sock *sk, unsigned int mss_now)
2625{
2626 struct sk_buff *skb = tcp_send_head(sk);
2627
2628 BUG_ON(!skb || skb->len < mss_now);
2629
2630 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2631}
2632
2633/* This function returns the amount that we can raise the
2634 * usable window based on the following constraints
2635 *
2636 * 1. The window can never be shrunk once it is offered (RFC 793)
2637 * 2. We limit memory per socket
2638 *
2639 * RFC 1122:
2640 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2641 * RECV.NEXT + RCV.WIN fixed until:
2642 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2643 *
2644 * i.e. don't raise the right edge of the window until you can raise
2645 * it at least MSS bytes.
2646 *
2647 * Unfortunately, the recommended algorithm breaks header prediction,
2648 * since header prediction assumes th->window stays fixed.
2649 *
2650 * Strictly speaking, keeping th->window fixed violates the receiver
2651 * side SWS prevention criteria. The problem is that under this rule
2652 * a stream of single byte packets will cause the right side of the
2653 * window to always advance by a single byte.
2654 *
2655 * Of course, if the sender implements sender side SWS prevention
2656 * then this will not be a problem.
2657 *
2658 * BSD seems to make the following compromise:
2659 *
2660 * If the free space is less than the 1/4 of the maximum
2661 * space available and the free space is less than 1/2 mss,
2662 * then set the window to 0.
2663 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2664 * Otherwise, just prevent the window from shrinking
2665 * and from being larger than the largest representable value.
2666 *
2667 * This prevents incremental opening of the window in the regime
2668 * where TCP is limited by the speed of the reader side taking
2669 * data out of the TCP receive queue. It does nothing about
2670 * those cases where the window is constrained on the sender side
2671 * because the pipeline is full.
2672 *
2673 * BSD also seems to "accidentally" limit itself to windows that are a
2674 * multiple of MSS, at least until the free space gets quite small.
2675 * This would appear to be a side effect of the mbuf implementation.
2676 * Combining these two algorithms results in the observed behavior
2677 * of having a fixed window size at almost all times.
2678 *
2679 * Below we obtain similar behavior by forcing the offered window to
2680 * a multiple of the mss when it is feasible to do so.
2681 *
2682 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2683 * Regular options like TIMESTAMP are taken into account.
2684 */
2685u32 __tcp_select_window(struct sock *sk)
2686{
2687 struct inet_connection_sock *icsk = inet_csk(sk);
2688 struct tcp_sock *tp = tcp_sk(sk);
2689 /* MSS for the peer's data. Previous versions used mss_clamp
2690 * here. I don't know if the value based on our guesses
2691 * of peer's MSS is better for the performance. It's more correct
2692 * but may be worse for the performance because of rcv_mss
2693 * fluctuations. --SAW 1998/11/1
2694 */
2695 int mss = icsk->icsk_ack.rcv_mss;
2696 int free_space = tcp_space(sk);
2697 int allowed_space = tcp_full_space(sk);
2698 int full_space = min_t(int, tp->window_clamp, allowed_space);
2699 int window;
2700
2701 if (unlikely(mss > full_space)) {
2702 mss = full_space;
2703 if (mss <= 0)
2704 return 0;
2705 }
2706 if (free_space < (full_space >> 1)) {
2707 icsk->icsk_ack.quick = 0;
2708
2709 if (tcp_under_memory_pressure(sk))
2710 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2711 4U * tp->advmss);
2712
2713 /* free_space might become our new window, make sure we don't
2714 * increase it due to wscale.
2715 */
2716 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2717
2718 /* if free space is less than mss estimate, or is below 1/16th
2719 * of the maximum allowed, try to move to zero-window, else
2720 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2721 * new incoming data is dropped due to memory limits.
2722 * With large window, mss test triggers way too late in order
2723 * to announce zero window in time before rmem limit kicks in.
2724 */
2725 if (free_space < (allowed_space >> 4) || free_space < mss)
2726 return 0;
2727 }
2728
2729 if (free_space > tp->rcv_ssthresh)
2730 free_space = tp->rcv_ssthresh;
2731
2732 /* Don't do rounding if we are using window scaling, since the
2733 * scaled window will not line up with the MSS boundary anyway.
2734 */
2735 if (tp->rx_opt.rcv_wscale) {
2736 window = free_space;
2737
2738 /* Advertise enough space so that it won't get scaled away.
2739 * Import case: prevent zero window announcement if
2740 * 1<<rcv_wscale > mss.
2741 */
2742 window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
2743 } else {
2744 window = tp->rcv_wnd;
2745 /* Get the largest window that is a nice multiple of mss.
2746 * Window clamp already applied above.
2747 * If our current window offering is within 1 mss of the
2748 * free space we just keep it. This prevents the divide
2749 * and multiply from happening most of the time.
2750 * We also don't do any window rounding when the free space
2751 * is too small.
2752 */
2753 if (window <= free_space - mss || window > free_space)
2754 window = rounddown(free_space, mss);
2755 else if (mss == full_space &&
2756 free_space > window + (full_space >> 1))
2757 window = free_space;
2758 }
2759
2760 return window;
2761}
2762
2763void tcp_skb_collapse_tstamp(struct sk_buff *skb,
2764 const struct sk_buff *next_skb)
2765{
2766 if (unlikely(tcp_has_tx_tstamp(next_skb))) {
2767 const struct skb_shared_info *next_shinfo =
2768 skb_shinfo(next_skb);
2769 struct skb_shared_info *shinfo = skb_shinfo(skb);
2770
2771 shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2772 shinfo->tskey = next_shinfo->tskey;
2773 TCP_SKB_CB(skb)->txstamp_ack |=
2774 TCP_SKB_CB(next_skb)->txstamp_ack;
2775 }
2776}
2777
2778/* Collapses two adjacent SKB's during retransmission. */
2779static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
2780{
2781 struct tcp_sock *tp = tcp_sk(sk);
2782 struct sk_buff *next_skb = skb_rb_next(skb);
2783 int next_skb_size;
2784
2785 next_skb_size = next_skb->len;
2786
2787 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2788
2789 if (next_skb_size) {
2790 if (next_skb_size <= skb_availroom(skb))
2791 skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
2792 next_skb_size);
2793 else if (!tcp_skb_shift(skb, next_skb, 1, next_skb_size))
2794 return false;
2795 }
2796 tcp_highest_sack_replace(sk, next_skb, skb);
2797
2798 /* Update sequence range on original skb. */
2799 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2800
2801 /* Merge over control information. This moves PSH/FIN etc. over */
2802 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2803
2804 /* All done, get rid of second SKB and account for it so
2805 * packet counting does not break.
2806 */
2807 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2808 TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2809
2810 /* changed transmit queue under us so clear hints */
2811 tcp_clear_retrans_hints_partial(tp);
2812 if (next_skb == tp->retransmit_skb_hint)
2813 tp->retransmit_skb_hint = skb;
2814
2815 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2816
2817 tcp_skb_collapse_tstamp(skb, next_skb);
2818
2819 tcp_rtx_queue_unlink_and_free(next_skb, sk);
2820 return true;
2821}
2822
2823/* Check if coalescing SKBs is legal. */
2824static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2825{
2826 if (tcp_skb_pcount(skb) > 1)
2827 return false;
2828 if (skb_cloned(skb))
2829 return false;
2830 /* Some heuristics for collapsing over SACK'd could be invented */
2831 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2832 return false;
2833
2834 return true;
2835}
2836
2837/* Collapse packets in the retransmit queue to make to create
2838 * less packets on the wire. This is only done on retransmission.
2839 */
2840static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2841 int space)
2842{
2843 struct tcp_sock *tp = tcp_sk(sk);
2844 struct sk_buff *skb = to, *tmp;
2845 bool first = true;
2846
2847 if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
2848 return;
2849 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2850 return;
2851
2852 skb_rbtree_walk_from_safe(skb, tmp) {
2853 if (!tcp_can_collapse(sk, skb))
2854 break;
2855
2856 if (!tcp_skb_can_collapse_to(to))
2857 break;
2858
2859 space -= skb->len;
2860
2861 if (first) {
2862 first = false;
2863 continue;
2864 }
2865
2866 if (space < 0)
2867 break;
2868
2869 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2870 break;
2871
2872 if (!tcp_collapse_retrans(sk, to))
2873 break;
2874 }
2875}
2876
2877/* This retransmits one SKB. Policy decisions and retransmit queue
2878 * state updates are done by the caller. Returns non-zero if an
2879 * error occurred which prevented the send.
2880 */
2881int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2882{
2883 struct inet_connection_sock *icsk = inet_csk(sk);
2884 struct tcp_sock *tp = tcp_sk(sk);
2885 unsigned int cur_mss;
2886 int diff, len, err;
2887
2888
2889 /* Inconclusive MTU probe */
2890 if (icsk->icsk_mtup.probe_size)
2891 icsk->icsk_mtup.probe_size = 0;
2892
2893 /* Do not sent more than we queued. 1/4 is reserved for possible
2894 * copying overhead: fragmentation, tunneling, mangling etc.
2895 */
2896 if (refcount_read(&sk->sk_wmem_alloc) >
2897 min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
2898 sk->sk_sndbuf))
2899 return -EAGAIN;
2900
2901 if (skb_still_in_host_queue(sk, skb))
2902 return -EBUSY;
2903
2904 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2905 if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
2906 WARN_ON_ONCE(1);
2907 return -EINVAL;
2908 }
2909 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
2910 return -ENOMEM;
2911 }
2912
2913 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
2914 return -EHOSTUNREACH; /* Routing failure or similar. */
2915
2916 cur_mss = tcp_current_mss(sk);
2917
2918 /* If receiver has shrunk his window, and skb is out of
2919 * new window, do not retransmit it. The exception is the
2920 * case, when window is shrunk to zero. In this case
2921 * our retransmit serves as a zero window probe.
2922 */
2923 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
2924 TCP_SKB_CB(skb)->seq != tp->snd_una)
2925 return -EAGAIN;
2926
2927 len = cur_mss * segs;
2928 if (skb->len > len) {
2929 if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
2930 cur_mss, GFP_ATOMIC))
2931 return -ENOMEM; /* We'll try again later. */
2932 } else {
2933 if (skb_unclone(skb, GFP_ATOMIC))
2934 return -ENOMEM;
2935
2936 diff = tcp_skb_pcount(skb);
2937 tcp_set_skb_tso_segs(skb, cur_mss);
2938 diff -= tcp_skb_pcount(skb);
2939 if (diff)
2940 tcp_adjust_pcount(sk, skb, diff);
2941 if (skb->len < cur_mss)
2942 tcp_retrans_try_collapse(sk, skb, cur_mss);
2943 }
2944
2945 /* RFC3168, section 6.1.1.1. ECN fallback */
2946 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
2947 tcp_ecn_clear_syn(sk, skb);
2948
2949 /* Update global and local TCP statistics. */
2950 segs = tcp_skb_pcount(skb);
2951 TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
2952 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2953 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2954 tp->total_retrans += segs;
2955 tp->bytes_retrans += skb->len;
2956
2957 /* make sure skb->data is aligned on arches that require it
2958 * and check if ack-trimming & collapsing extended the headroom
2959 * beyond what csum_start can cover.
2960 */
2961 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
2962 skb_headroom(skb) >= 0xFFFF)) {
2963 struct sk_buff *nskb;
2964
2965 tcp_skb_tsorted_save(skb) {
2966 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2967 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
2968 -ENOBUFS;
2969 } tcp_skb_tsorted_restore(skb);
2970
2971 if (!err) {
2972 tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns);
2973 tcp_rate_skb_sent(sk, skb);
2974 }
2975 } else {
2976 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2977 }
2978
2979 /* To avoid taking spuriously low RTT samples based on a timestamp
2980 * for a transmit that never happened, always mark EVER_RETRANS
2981 */
2982 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2983
2984 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
2985 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
2986 TCP_SKB_CB(skb)->seq, segs, err);
2987
2988 if (likely(!err)) {
2989 trace_tcp_retransmit_skb(sk, skb);
2990 } else if (err != -EBUSY) {
2991 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
2992 }
2993 return err;
2994}
2995
2996int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2997{
2998 struct tcp_sock *tp = tcp_sk(sk);
2999 int err = __tcp_retransmit_skb(sk, skb, segs);
3000
3001 if (err == 0) {
3002#if FASTRETRANS_DEBUG > 0
3003 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
3004 net_dbg_ratelimited("retrans_out leaked\n");
3005 }
3006#endif
3007 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
3008 tp->retrans_out += tcp_skb_pcount(skb);
3009 }
3010
3011 /* Save stamp of the first (attempted) retransmit. */
3012 if (!tp->retrans_stamp)
3013 tp->retrans_stamp = tcp_skb_timestamp(skb);
3014
3015 if (tp->undo_retrans < 0)
3016 tp->undo_retrans = 0;
3017 tp->undo_retrans += tcp_skb_pcount(skb);
3018 return err;
3019}
3020
3021/* This gets called after a retransmit timeout, and the initially
3022 * retransmitted data is acknowledged. It tries to continue
3023 * resending the rest of the retransmit queue, until either
3024 * we've sent it all or the congestion window limit is reached.
3025 */
3026void tcp_xmit_retransmit_queue(struct sock *sk)
3027{
3028 const struct inet_connection_sock *icsk = inet_csk(sk);
3029 struct sk_buff *skb, *rtx_head, *hole = NULL;
3030 struct tcp_sock *tp = tcp_sk(sk);
3031 u32 max_segs;
3032 int mib_idx;
3033
3034 if (!tp->packets_out)
3035 return;
3036
3037 rtx_head = tcp_rtx_queue_head(sk);
3038 skb = tp->retransmit_skb_hint ?: rtx_head;
3039 max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
3040 skb_rbtree_walk_from(skb) {
3041 __u8 sacked;
3042 int segs;
3043
3044 if (tcp_pacing_check(sk))
3045 break;
3046
3047 /* we could do better than to assign each time */
3048 if (!hole)
3049 tp->retransmit_skb_hint = skb;
3050
3051 segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
3052 if (segs <= 0)
3053 return;
3054 sacked = TCP_SKB_CB(skb)->sacked;
3055 /* In case tcp_shift_skb_data() have aggregated large skbs,
3056 * we need to make sure not sending too bigs TSO packets
3057 */
3058 segs = min_t(int, segs, max_segs);
3059
3060 if (tp->retrans_out >= tp->lost_out) {
3061 break;
3062 } else if (!(sacked & TCPCB_LOST)) {
3063 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
3064 hole = skb;
3065 continue;
3066
3067 } else {
3068 if (icsk->icsk_ca_state != TCP_CA_Loss)
3069 mib_idx = LINUX_MIB_TCPFASTRETRANS;
3070 else
3071 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
3072 }
3073
3074 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
3075 continue;
3076
3077 if (tcp_small_queue_check(sk, skb, 1))
3078 return;
3079
3080 if (tcp_retransmit_skb(sk, skb, segs))
3081 return;
3082
3083 NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
3084
3085 if (tcp_in_cwnd_reduction(sk))
3086 tp->prr_out += tcp_skb_pcount(skb);
3087
3088 if (skb == rtx_head &&
3089 icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3090 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3091 inet_csk(sk)->icsk_rto,
3092 TCP_RTO_MAX,
3093 skb);
3094 }
3095}
3096
3097/* We allow to exceed memory limits for FIN packets to expedite
3098 * connection tear down and (memory) recovery.
3099 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3100 * or even be forced to close flow without any FIN.
3101 * In general, we want to allow one skb per socket to avoid hangs
3102 * with edge trigger epoll()
3103 */
3104void sk_forced_mem_schedule(struct sock *sk, int size)
3105{
3106 int amt;
3107
3108 if (size <= sk->sk_forward_alloc)
3109 return;
3110 amt = sk_mem_pages(size);
3111 sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
3112 sk_memory_allocated_add(sk, amt);
3113
3114 if (mem_cgroup_sockets_enabled && sk->sk_memcg)
3115 mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3116}
3117
3118/* Send a FIN. The caller locks the socket for us.
3119 * We should try to send a FIN packet really hard, but eventually give up.
3120 */
3121void tcp_send_fin(struct sock *sk)
3122{
3123 struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
3124 struct tcp_sock *tp = tcp_sk(sk);
3125
3126 /* Optimization, tack on the FIN if we have one skb in write queue and
3127 * this skb was not yet sent, or we are under memory pressure.
3128 * Note: in the latter case, FIN packet will be sent after a timeout,
3129 * as TCP stack thinks it has already been transmitted.
3130 */
3131 if (!tskb && tcp_under_memory_pressure(sk))
3132 tskb = skb_rb_last(&sk->tcp_rtx_queue);
3133
3134 if (tskb) {
3135 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
3136 TCP_SKB_CB(tskb)->end_seq++;
3137 tp->write_seq++;
3138 if (tcp_write_queue_empty(sk)) {
3139 /* This means tskb was already sent.
3140 * Pretend we included the FIN on previous transmit.
3141 * We need to set tp->snd_nxt to the value it would have
3142 * if FIN had been sent. This is because retransmit path
3143 * does not change tp->snd_nxt.
3144 */
3145 WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1);
3146 return;
3147 }
3148 } else {
3149 skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
3150 if (unlikely(!skb))
3151 return;
3152
3153 INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3154 skb_reserve(skb, MAX_TCP_HEADER);
3155 sk_forced_mem_schedule(sk, skb->truesize);
3156 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3157 tcp_init_nondata_skb(skb, tp->write_seq,
3158 TCPHDR_ACK | TCPHDR_FIN);
3159 tcp_queue_skb(sk, skb);
3160 }
3161 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
3162}
3163
3164/* We get here when a process closes a file descriptor (either due to
3165 * an explicit close() or as a byproduct of exit()'ing) and there
3166 * was unread data in the receive queue. This behavior is recommended
3167 * by RFC 2525, section 2.17. -DaveM
3168 */
3169void tcp_send_active_reset(struct sock *sk, gfp_t priority)
3170{
3171 struct sk_buff *skb;
3172
3173 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
3174
3175 /* NOTE: No TCP options attached and we never retransmit this. */
3176 skb = alloc_skb(MAX_TCP_HEADER, priority);
3177 if (!skb) {
3178 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3179 return;
3180 }
3181
3182 /* Reserve space for headers and prepare control bits. */
3183 skb_reserve(skb, MAX_TCP_HEADER);
3184 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
3185 TCPHDR_ACK | TCPHDR_RST);
3186 tcp_mstamp_refresh(tcp_sk(sk));
3187 /* Send it off. */
3188 if (tcp_transmit_skb(sk, skb, 0, priority))
3189 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3190
3191 /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3192 * skb here is different to the troublesome skb, so use NULL
3193 */
3194 trace_tcp_send_reset(sk, NULL);
3195}
3196
3197/* Send a crossed SYN-ACK during socket establishment.
3198 * WARNING: This routine must only be called when we have already sent
3199 * a SYN packet that crossed the incoming SYN that caused this routine
3200 * to get called. If this assumption fails then the initial rcv_wnd
3201 * and rcv_wscale values will not be correct.
3202 */
3203int tcp_send_synack(struct sock *sk)
3204{
3205 struct sk_buff *skb;
3206
3207 skb = tcp_rtx_queue_head(sk);
3208 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3209 pr_err("%s: wrong queue state\n", __func__);
3210 return -EFAULT;
3211 }
3212 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
3213 if (skb_cloned(skb)) {
3214 struct sk_buff *nskb;
3215
3216 tcp_skb_tsorted_save(skb) {
3217 nskb = skb_copy(skb, GFP_ATOMIC);
3218 } tcp_skb_tsorted_restore(skb);
3219 if (!nskb)
3220 return -ENOMEM;
3221 INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3222 tcp_rtx_queue_unlink_and_free(skb, sk);
3223 __skb_header_release(nskb);
3224 tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3225 sk_wmem_queued_add(sk, nskb->truesize);
3226 sk_mem_charge(sk, nskb->truesize);
3227 skb = nskb;
3228 }
3229
3230 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3231 tcp_ecn_send_synack(sk, skb);
3232 }
3233 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3234}
3235
3236/**
3237 * tcp_make_synack - Prepare a SYN-ACK.
3238 * sk: listener socket
3239 * dst: dst entry attached to the SYNACK
3240 * req: request_sock pointer
3241 *
3242 * Allocate one skb and build a SYNACK packet.
3243 * @dst is consumed : Caller should not use it again.
3244 */
3245struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3246 struct request_sock *req,
3247 struct tcp_fastopen_cookie *foc,
3248 enum tcp_synack_type synack_type)
3249{
3250 struct inet_request_sock *ireq = inet_rsk(req);
3251 const struct tcp_sock *tp = tcp_sk(sk);
3252 struct tcp_md5sig_key *md5 = NULL;
3253 struct tcp_out_options opts;
3254 struct sk_buff *skb;
3255 int tcp_header_size;
3256 struct tcphdr *th;
3257 int mss;
3258 u64 now;
3259
3260 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3261 if (unlikely(!skb)) {
3262 dst_release(dst);
3263 return NULL;
3264 }
3265 /* Reserve space for headers. */
3266 skb_reserve(skb, MAX_TCP_HEADER);
3267
3268 switch (synack_type) {
3269 case TCP_SYNACK_NORMAL:
3270 skb_set_owner_w(skb, req_to_sk(req));
3271 break;
3272 case TCP_SYNACK_COOKIE:
3273 /* Under synflood, we do not attach skb to a socket,
3274 * to avoid false sharing.
3275 */
3276 break;
3277 case TCP_SYNACK_FASTOPEN:
3278 /* sk is a const pointer, because we want to express multiple
3279 * cpu might call us concurrently.
3280 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3281 */
3282 skb_set_owner_w(skb, (struct sock *)sk);
3283 break;
3284 }
3285 skb_dst_set(skb, dst);
3286
3287 mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3288
3289 memset(&opts, 0, sizeof(opts));
3290 now = tcp_clock_ns();
3291#ifdef CONFIG_SYN_COOKIES
3292 if (unlikely(req->cookie_ts))
3293 skb->skb_mstamp_ns = cookie_init_timestamp(req);
3294 else
3295#endif
3296 {
3297 skb->skb_mstamp_ns = now;
3298 if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */
3299 tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);
3300 }
3301
3302#ifdef CONFIG_TCP_MD5SIG
3303 rcu_read_lock();
3304 md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
3305#endif
3306 skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3307 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
3308 foc) + sizeof(*th);
3309
3310 skb_push(skb, tcp_header_size);
3311 skb_reset_transport_header(skb);
3312
3313 th = (struct tcphdr *)skb->data;
3314 memset(th, 0, sizeof(struct tcphdr));
3315 th->syn = 1;
3316 th->ack = 1;
3317 tcp_ecn_make_synack(req, th);
3318 th->source = htons(ireq->ir_num);
3319 th->dest = ireq->ir_rmt_port;
3320 skb->mark = ireq->ir_mark;
3321 skb->ip_summed = CHECKSUM_PARTIAL;
3322 th->seq = htonl(tcp_rsk(req)->snt_isn);
3323 /* XXX data is queued and acked as is. No buffer/window check */
3324 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
3325
3326 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3327 th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3328 tcp_options_write((__be32 *)(th + 1), NULL, &opts);
3329 th->doff = (tcp_header_size >> 2);
3330 __TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3331
3332#ifdef CONFIG_TCP_MD5SIG
3333 /* Okay, we have all we need - do the md5 hash if needed */
3334 if (md5)
3335 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3336 md5, req_to_sk(req), skb);
3337 rcu_read_unlock();
3338#endif
3339
3340 skb->skb_mstamp_ns = now;
3341 tcp_add_tx_delay(skb, tp);
3342
3343 return skb;
3344}
3345EXPORT_SYMBOL(tcp_make_synack);
3346
3347static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
3348{
3349 struct inet_connection_sock *icsk = inet_csk(sk);
3350 const struct tcp_congestion_ops *ca;
3351 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
3352
3353 if (ca_key == TCP_CA_UNSPEC)
3354 return;
3355
3356 rcu_read_lock();
3357 ca = tcp_ca_find_key(ca_key);
3358 if (likely(ca && try_module_get(ca->owner))) {
3359 module_put(icsk->icsk_ca_ops->owner);
3360 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
3361 icsk->icsk_ca_ops = ca;
3362 }
3363 rcu_read_unlock();
3364}
3365
3366/* Do all connect socket setups that can be done AF independent. */
3367static void tcp_connect_init(struct sock *sk)
3368{
3369 const struct dst_entry *dst = __sk_dst_get(sk);
3370 struct tcp_sock *tp = tcp_sk(sk);
3371 __u8 rcv_wscale;
3372 u32 rcv_wnd;
3373
3374 /* We'll fix this up when we get a response from the other end.
3375 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3376 */
3377 tp->tcp_header_len = sizeof(struct tcphdr);
3378 if (sock_net(sk)->ipv4.sysctl_tcp_timestamps)
3379 tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
3380
3381#ifdef CONFIG_TCP_MD5SIG
3382 if (tp->af_specific->md5_lookup(sk, sk))
3383 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
3384#endif
3385
3386 /* If user gave his TCP_MAXSEG, record it to clamp */
3387 if (tp->rx_opt.user_mss)
3388 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3389 tp->max_window = 0;
3390 tcp_mtup_init(sk);
3391 tcp_sync_mss(sk, dst_mtu(dst));
3392
3393 tcp_ca_dst_init(sk, dst);
3394
3395 if (!tp->window_clamp)
3396 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3397 tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3398
3399 tcp_initialize_rcv_mss(sk);
3400
3401 /* limit the window selection if the user enforce a smaller rx buffer */
3402 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
3403 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
3404 tp->window_clamp = tcp_full_space(sk);
3405
3406 rcv_wnd = tcp_rwnd_init_bpf(sk);
3407 if (rcv_wnd == 0)
3408 rcv_wnd = dst_metric(dst, RTAX_INITRWND);
3409
3410 tcp_select_initial_window(sk, tcp_full_space(sk),
3411 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
3412 &tp->rcv_wnd,
3413 &tp->window_clamp,
3414 sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
3415 &rcv_wscale,
3416 rcv_wnd);
3417
3418 tp->rx_opt.rcv_wscale = rcv_wscale;
3419 tp->rcv_ssthresh = tp->rcv_wnd;
3420
3421 sk->sk_err = 0;
3422 sock_reset_flag(sk, SOCK_DONE);
3423 tp->snd_wnd = 0;
3424 tcp_init_wl(tp, 0);
3425 tcp_write_queue_purge(sk);
3426 tp->snd_una = tp->write_seq;
3427 tp->snd_sml = tp->write_seq;
3428 tp->snd_up = tp->write_seq;
3429 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3430
3431 if (likely(!tp->repair))
3432 tp->rcv_nxt = 0;
3433 else
3434 tp->rcv_tstamp = tcp_jiffies32;
3435 tp->rcv_wup = tp->rcv_nxt;
3436 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
3437
3438 inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3439 inet_csk(sk)->icsk_retransmits = 0;
3440 tcp_clear_retrans(tp);
3441}
3442
3443static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
3444{
3445 struct tcp_sock *tp = tcp_sk(sk);
3446 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
3447
3448 tcb->end_seq += skb->len;
3449 __skb_header_release(skb);
3450 sk_wmem_queued_add(sk, skb->truesize);
3451 sk_mem_charge(sk, skb->truesize);
3452 WRITE_ONCE(tp->write_seq, tcb->end_seq);
3453 tp->packets_out += tcp_skb_pcount(skb);
3454}
3455
3456/* Build and send a SYN with data and (cached) Fast Open cookie. However,
3457 * queue a data-only packet after the regular SYN, such that regular SYNs
3458 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3459 * only the SYN sequence, the data are retransmitted in the first ACK.
3460 * If cookie is not cached or other error occurs, falls back to send a
3461 * regular SYN with Fast Open cookie request option.
3462 */
3463static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
3464{
3465 struct tcp_sock *tp = tcp_sk(sk);
3466 struct tcp_fastopen_request *fo = tp->fastopen_req;
3467 int space, err = 0;
3468 struct sk_buff *syn_data;
3469
3470 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
3471 if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3472 goto fallback;
3473
3474 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3475 * user-MSS. Reserve maximum option space for middleboxes that add
3476 * private TCP options. The cost is reduced data space in SYN :(
3477 */
3478 tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
3479
3480 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3481 MAX_TCP_OPTION_SPACE;
3482
3483 space = min_t(size_t, space, fo->size);
3484
3485 /* limit to order-0 allocations */
3486 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
3487
3488 syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3489 if (!syn_data)
3490 goto fallback;
3491 syn_data->ip_summed = CHECKSUM_PARTIAL;
3492 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3493 if (space) {
3494 int copied = copy_from_iter(skb_put(syn_data, space), space,
3495 &fo->data->msg_iter);
3496 if (unlikely(!copied)) {
3497 tcp_skb_tsorted_anchor_cleanup(syn_data);
3498 kfree_skb(syn_data);
3499 goto fallback;
3500 }
3501 if (copied != space) {
3502 skb_trim(syn_data, copied);
3503 space = copied;
3504 }
3505 skb_zcopy_set(syn_data, fo->uarg, NULL);
3506 }
3507 /* No more data pending in inet_wait_for_connect() */
3508 if (space == fo->size)
3509 fo->data = NULL;
3510 fo->copied = space;
3511
3512 tcp_connect_queue_skb(sk, syn_data);
3513 if (syn_data->len)
3514 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3515
3516 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3517
3518 syn->skb_mstamp_ns = syn_data->skb_mstamp_ns;
3519
3520 /* Now full SYN+DATA was cloned and sent (or not),
3521 * remove the SYN from the original skb (syn_data)
3522 * we keep in write queue in case of a retransmit, as we
3523 * also have the SYN packet (with no data) in the same queue.
3524 */
3525 TCP_SKB_CB(syn_data)->seq++;
3526 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
3527 if (!err) {
3528 tp->syn_data = (fo->copied > 0);
3529 tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
3530 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3531 goto done;
3532 }
3533
3534 /* data was not sent, put it in write_queue */
3535 __skb_queue_tail(&sk->sk_write_queue, syn_data);
3536 tp->packets_out -= tcp_skb_pcount(syn_data);
3537
3538fallback:
3539 /* Send a regular SYN with Fast Open cookie request option */
3540 if (fo->cookie.len > 0)
3541 fo->cookie.len = 0;
3542 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3543 if (err)
3544 tp->syn_fastopen = 0;
3545done:
3546 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3547 return err;
3548}
3549
3550/* Build a SYN and send it off. */
3551int tcp_connect(struct sock *sk)
3552{
3553 struct tcp_sock *tp = tcp_sk(sk);
3554 struct sk_buff *buff;
3555 int err;
3556
3557 tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
3558
3559 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3560 return -EHOSTUNREACH; /* Routing failure or similar. */
3561
3562 tcp_connect_init(sk);
3563
3564 if (unlikely(tp->repair)) {
3565 tcp_finish_connect(sk, NULL);
3566 return 0;
3567 }
3568
3569 buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3570 if (unlikely(!buff))
3571 return -ENOBUFS;
3572
3573 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3574 tcp_mstamp_refresh(tp);
3575 tp->retrans_stamp = tcp_time_stamp(tp);
3576 tcp_connect_queue_skb(sk, buff);
3577 tcp_ecn_send_syn(sk, buff);
3578 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
3579
3580 /* Send off SYN; include data in Fast Open. */
3581 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3582 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3583 if (err == -ECONNREFUSED)
3584 return err;
3585
3586 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3587 * in order to make this packet get counted in tcpOutSegs.
3588 */
3589 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3590 tp->pushed_seq = tp->write_seq;
3591 buff = tcp_send_head(sk);
3592 if (unlikely(buff)) {
3593 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq);
3594 tp->pushed_seq = TCP_SKB_CB(buff)->seq;
3595 }
3596 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3597
3598 /* Timer for repeating the SYN until an answer. */
3599 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3600 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3601 return 0;
3602}
3603EXPORT_SYMBOL(tcp_connect);
3604
3605/* Send out a delayed ack, the caller does the policy checking
3606 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3607 * for details.
3608 */
3609void tcp_send_delayed_ack(struct sock *sk)
3610{
3611 struct inet_connection_sock *icsk = inet_csk(sk);
3612 int ato = icsk->icsk_ack.ato;
3613 unsigned long timeout;
3614
3615 if (ato > TCP_DELACK_MIN) {
3616 const struct tcp_sock *tp = tcp_sk(sk);
3617 int max_ato = HZ / 2;
3618
3619 if (inet_csk_in_pingpong_mode(sk) ||
3620 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3621 max_ato = TCP_DELACK_MAX;
3622
3623 /* Slow path, intersegment interval is "high". */
3624
3625 /* If some rtt estimate is known, use it to bound delayed ack.
3626 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3627 * directly.
3628 */
3629 if (tp->srtt_us) {
3630 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3631 TCP_DELACK_MIN);
3632
3633 if (rtt < max_ato)
3634 max_ato = rtt;
3635 }
3636
3637 ato = min(ato, max_ato);
3638 }
3639
3640 /* Stay within the limit we were given */
3641 timeout = jiffies + ato;
3642
3643 /* Use new timeout only if there wasn't a older one earlier. */
3644 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3645 /* If delack timer was blocked or is about to expire,
3646 * send ACK now.
3647 */
3648 if (icsk->icsk_ack.blocked ||
3649 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3650 tcp_send_ack(sk);
3651 return;
3652 }
3653
3654 if (!time_before(timeout, icsk->icsk_ack.timeout))
3655 timeout = icsk->icsk_ack.timeout;
3656 }
3657 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3658 icsk->icsk_ack.timeout = timeout;
3659 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3660}
3661
3662/* This routine sends an ack and also updates the window. */
3663void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
3664{
3665 struct sk_buff *buff;
3666
3667 /* If we have been reset, we may not send again. */
3668 if (sk->sk_state == TCP_CLOSE)
3669 return;
3670
3671 /* We are not putting this on the write queue, so
3672 * tcp_transmit_skb() will set the ownership to this
3673 * sock.
3674 */
3675 buff = alloc_skb(MAX_TCP_HEADER,
3676 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3677 if (unlikely(!buff)) {
3678 inet_csk_schedule_ack(sk);
3679 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
3680 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
3681 TCP_DELACK_MAX, TCP_RTO_MAX);
3682 return;
3683 }
3684
3685 /* Reserve space for headers and prepare control bits. */
3686 skb_reserve(buff, MAX_TCP_HEADER);
3687 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3688
3689 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
3690 * too much.
3691 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
3692 */
3693 skb_set_tcp_pure_ack(buff);
3694
3695 /* Send it off, this clears delayed acks for us. */
3696 __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
3697}
3698EXPORT_SYMBOL_GPL(__tcp_send_ack);
3699
3700void tcp_send_ack(struct sock *sk)
3701{
3702 __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
3703}
3704
3705/* This routine sends a packet with an out of date sequence
3706 * number. It assumes the other end will try to ack it.
3707 *
3708 * Question: what should we make while urgent mode?
3709 * 4.4BSD forces sending single byte of data. We cannot send
3710 * out of window data, because we have SND.NXT==SND.MAX...
3711 *
3712 * Current solution: to send TWO zero-length segments in urgent mode:
3713 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3714 * out-of-date with SND.UNA-1 to probe window.
3715 */
3716static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
3717{
3718 struct tcp_sock *tp = tcp_sk(sk);
3719 struct sk_buff *skb;
3720
3721 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3722 skb = alloc_skb(MAX_TCP_HEADER,
3723 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3724 if (!skb)
3725 return -1;
3726
3727 /* Reserve space for headers and set control bits. */
3728 skb_reserve(skb, MAX_TCP_HEADER);
3729 /* Use a previous sequence. This should cause the other
3730 * end to send an ack. Don't queue or clone SKB, just
3731 * send it.
3732 */
3733 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3734 NET_INC_STATS(sock_net(sk), mib);
3735 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
3736}
3737
3738/* Called from setsockopt( ... TCP_REPAIR ) */
3739void tcp_send_window_probe(struct sock *sk)
3740{
3741 if (sk->sk_state == TCP_ESTABLISHED) {
3742 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3743 tcp_mstamp_refresh(tcp_sk(sk));
3744 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
3745 }
3746}
3747
3748/* Initiate keepalive or window probe from timer. */
3749int tcp_write_wakeup(struct sock *sk, int mib)
3750{
3751 struct tcp_sock *tp = tcp_sk(sk);
3752 struct sk_buff *skb;
3753
3754 if (sk->sk_state == TCP_CLOSE)
3755 return -1;
3756
3757 skb = tcp_send_head(sk);
3758 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3759 int err;
3760 unsigned int mss = tcp_current_mss(sk);
3761 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3762
3763 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
3764 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
3765
3766 /* We are probing the opening of a window
3767 * but the window size is != 0
3768 * must have been a result SWS avoidance ( sender )
3769 */
3770 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
3771 skb->len > mss) {
3772 seg_size = min(seg_size, mss);
3773 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3774 if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
3775 skb, seg_size, mss, GFP_ATOMIC))
3776 return -1;
3777 } else if (!tcp_skb_pcount(skb))
3778 tcp_set_skb_tso_segs(skb, mss);
3779
3780 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3781 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3782 if (!err)
3783 tcp_event_new_data_sent(sk, skb);
3784 return err;
3785 } else {
3786 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3787 tcp_xmit_probe_skb(sk, 1, mib);
3788 return tcp_xmit_probe_skb(sk, 0, mib);
3789 }
3790}
3791
3792/* A window probe timeout has occurred. If window is not closed send
3793 * a partial packet else a zero probe.
3794 */
3795void tcp_send_probe0(struct sock *sk)
3796{
3797 struct inet_connection_sock *icsk = inet_csk(sk);
3798 struct tcp_sock *tp = tcp_sk(sk);
3799 struct net *net = sock_net(sk);
3800 unsigned long timeout;
3801 int err;
3802
3803 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
3804
3805 if (tp->packets_out || tcp_write_queue_empty(sk)) {
3806 /* Cancel probe timer, if it is not required. */
3807 icsk->icsk_probes_out = 0;
3808 icsk->icsk_backoff = 0;
3809 return;
3810 }
3811
3812 icsk->icsk_probes_out++;
3813 if (err <= 0) {
3814 if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3815 icsk->icsk_backoff++;
3816 timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
3817 } else {
3818 /* If packet was not sent due to local congestion,
3819 * Let senders fight for local resources conservatively.
3820 */
3821 timeout = TCP_RESOURCE_PROBE_INTERVAL;
3822 }
3823 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX, NULL);
3824}
3825
3826int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3827{
3828 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
3829 struct flowi fl;
3830 int res;
3831
3832 tcp_rsk(req)->txhash = net_tx_rndhash();
3833 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3834 if (!res) {
3835 __TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3836 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3837 if (unlikely(tcp_passive_fastopen(sk)))
3838 tcp_sk(sk)->total_retrans++;
3839 trace_tcp_retransmit_synack(sk, req);
3840 }
3841 return res;
3842}
3843EXPORT_SYMBOL(tcp_rtx_synack);
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/* This limits the percentage of the congestion window which we
54 * will allow a single TSO frame to consume. Building TSO frames
55 * which are too large can cause TCP streams to be bursty.
56 */
57int sysctl_tcp_tso_win_divisor __read_mostly = 3;
58
59int sysctl_tcp_mtu_probing __read_mostly = 0;
60int sysctl_tcp_base_mss __read_mostly = TCP_BASE_MSS;
61
62/* By default, RFC2861 behavior. */
63int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
64
65int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */
66EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size);
67
68
69/* Account for new data that has been sent to the network. */
70static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
71{
72 struct tcp_sock *tp = tcp_sk(sk);
73 unsigned int prior_packets = tp->packets_out;
74
75 tcp_advance_send_head(sk, skb);
76 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
77
78 /* Don't override Nagle indefinitely with F-RTO */
79 if (tp->frto_counter == 2)
80 tp->frto_counter = 3;
81
82 tp->packets_out += tcp_skb_pcount(skb);
83 if (!prior_packets || tp->early_retrans_delayed)
84 tcp_rearm_rto(sk);
85}
86
87/* SND.NXT, if window was not shrunk.
88 * If window has been shrunk, what should we make? It is not clear at all.
89 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
90 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
91 * invalid. OK, let's make this for now:
92 */
93static inline __u32 tcp_acceptable_seq(const struct sock *sk)
94{
95 const struct tcp_sock *tp = tcp_sk(sk);
96
97 if (!before(tcp_wnd_end(tp), tp->snd_nxt))
98 return tp->snd_nxt;
99 else
100 return tcp_wnd_end(tp);
101}
102
103/* Calculate mss to advertise in SYN segment.
104 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
105 *
106 * 1. It is independent of path mtu.
107 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
108 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
109 * attached devices, because some buggy hosts are confused by
110 * large MSS.
111 * 4. We do not make 3, we advertise MSS, calculated from first
112 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
113 * This may be overridden via information stored in routing table.
114 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
115 * probably even Jumbo".
116 */
117static __u16 tcp_advertise_mss(struct sock *sk)
118{
119 struct tcp_sock *tp = tcp_sk(sk);
120 const struct dst_entry *dst = __sk_dst_get(sk);
121 int mss = tp->advmss;
122
123 if (dst) {
124 unsigned int metric = dst_metric_advmss(dst);
125
126 if (metric < mss) {
127 mss = metric;
128 tp->advmss = mss;
129 }
130 }
131
132 return (__u16)mss;
133}
134
135/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
136 * This is the first part of cwnd validation mechanism. */
137static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst)
138{
139 struct tcp_sock *tp = tcp_sk(sk);
140 s32 delta = tcp_time_stamp - tp->lsndtime;
141 u32 restart_cwnd = tcp_init_cwnd(tp, dst);
142 u32 cwnd = tp->snd_cwnd;
143
144 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
145
146 tp->snd_ssthresh = tcp_current_ssthresh(sk);
147 restart_cwnd = min(restart_cwnd, cwnd);
148
149 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
150 cwnd >>= 1;
151 tp->snd_cwnd = max(cwnd, restart_cwnd);
152 tp->snd_cwnd_stamp = tcp_time_stamp;
153 tp->snd_cwnd_used = 0;
154}
155
156/* Congestion state accounting after a packet has been sent. */
157static void tcp_event_data_sent(struct tcp_sock *tp,
158 struct sock *sk)
159{
160 struct inet_connection_sock *icsk = inet_csk(sk);
161 const u32 now = tcp_time_stamp;
162
163 if (sysctl_tcp_slow_start_after_idle &&
164 (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
165 tcp_cwnd_restart(sk, __sk_dst_get(sk));
166
167 tp->lsndtime = now;
168
169 /* If it is a reply for ato after last received
170 * packet, enter pingpong mode.
171 */
172 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
173 icsk->icsk_ack.pingpong = 1;
174}
175
176/* Account for an ACK we sent. */
177static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
178{
179 tcp_dec_quickack_mode(sk, pkts);
180 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
181}
182
183/* Determine a window scaling and initial window to offer.
184 * Based on the assumption that the given amount of space
185 * will be offered. Store the results in the tp structure.
186 * NOTE: for smooth operation initial space offering should
187 * be a multiple of mss if possible. We assume here that mss >= 1.
188 * This MUST be enforced by all callers.
189 */
190void tcp_select_initial_window(int __space, __u32 mss,
191 __u32 *rcv_wnd, __u32 *window_clamp,
192 int wscale_ok, __u8 *rcv_wscale,
193 __u32 init_rcv_wnd)
194{
195 unsigned int space = (__space < 0 ? 0 : __space);
196
197 /* If no clamp set the clamp to the max possible scaled window */
198 if (*window_clamp == 0)
199 (*window_clamp) = (65535 << 14);
200 space = min(*window_clamp, space);
201
202 /* Quantize space offering to a multiple of mss if possible. */
203 if (space > mss)
204 space = (space / mss) * mss;
205
206 /* NOTE: offering an initial window larger than 32767
207 * will break some buggy TCP stacks. If the admin tells us
208 * it is likely we could be speaking with such a buggy stack
209 * we will truncate our initial window offering to 32K-1
210 * unless the remote has sent us a window scaling option,
211 * which we interpret as a sign the remote TCP is not
212 * misinterpreting the window field as a signed quantity.
213 */
214 if (sysctl_tcp_workaround_signed_windows)
215 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
216 else
217 (*rcv_wnd) = space;
218
219 (*rcv_wscale) = 0;
220 if (wscale_ok) {
221 /* Set window scaling on max possible window
222 * See RFC1323 for an explanation of the limit to 14
223 */
224 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
225 space = min_t(u32, space, *window_clamp);
226 while (space > 65535 && (*rcv_wscale) < 14) {
227 space >>= 1;
228 (*rcv_wscale)++;
229 }
230 }
231
232 /* Set initial window to a value enough for senders starting with
233 * initial congestion window of TCP_DEFAULT_INIT_RCVWND. Place
234 * a limit on the initial window when mss is larger than 1460.
235 */
236 if (mss > (1 << *rcv_wscale)) {
237 int init_cwnd = TCP_DEFAULT_INIT_RCVWND;
238 if (mss > 1460)
239 init_cwnd =
240 max_t(u32, (1460 * TCP_DEFAULT_INIT_RCVWND) / mss, 2);
241 /* when initializing use the value from init_rcv_wnd
242 * rather than the default from above
243 */
244 if (init_rcv_wnd)
245 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
246 else
247 *rcv_wnd = min(*rcv_wnd, init_cwnd * mss);
248 }
249
250 /* Set the clamp no higher than max representable value */
251 (*window_clamp) = min(65535U << (*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 u32 cur_win = tcp_receive_window(tp);
264 u32 new_win = __tcp_select_window(sk);
265
266 /* Never shrink the offered window */
267 if (new_win < cur_win) {
268 /* Danger Will Robinson!
269 * Don't update rcv_wup/rcv_wnd here or else
270 * we will not be able to advertise a zero
271 * window in time. --DaveM
272 *
273 * Relax Will Robinson.
274 */
275 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
276 }
277 tp->rcv_wnd = new_win;
278 tp->rcv_wup = tp->rcv_nxt;
279
280 /* Make sure we do not exceed the maximum possible
281 * scaled window.
282 */
283 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
284 new_win = min(new_win, MAX_TCP_WINDOW);
285 else
286 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
287
288 /* RFC1323 scaling applied */
289 new_win >>= tp->rx_opt.rcv_wscale;
290
291 /* If we advertise zero window, disable fast path. */
292 if (new_win == 0)
293 tp->pred_flags = 0;
294
295 return new_win;
296}
297
298/* Packet ECN state for a SYN-ACK */
299static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb)
300{
301 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
302 if (!(tp->ecn_flags & TCP_ECN_OK))
303 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
304}
305
306/* Packet ECN state for a SYN. */
307static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
308{
309 struct tcp_sock *tp = tcp_sk(sk);
310
311 tp->ecn_flags = 0;
312 if (sysctl_tcp_ecn == 1) {
313 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
314 tp->ecn_flags = TCP_ECN_OK;
315 }
316}
317
318static __inline__ void
319TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th)
320{
321 if (inet_rsk(req)->ecn_ok)
322 th->ece = 1;
323}
324
325/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
326 * be sent.
327 */
328static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
329 int tcp_header_len)
330{
331 struct tcp_sock *tp = tcp_sk(sk);
332
333 if (tp->ecn_flags & TCP_ECN_OK) {
334 /* Not-retransmitted data segment: set ECT and inject CWR. */
335 if (skb->len != tcp_header_len &&
336 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
337 INET_ECN_xmit(sk);
338 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
339 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
340 tcp_hdr(skb)->cwr = 1;
341 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
342 }
343 } else {
344 /* ACK or retransmitted segment: clear ECT|CE */
345 INET_ECN_dontxmit(sk);
346 }
347 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
348 tcp_hdr(skb)->ece = 1;
349 }
350}
351
352/* Constructs common control bits of non-data skb. If SYN/FIN is present,
353 * auto increment end seqno.
354 */
355static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
356{
357 skb->ip_summed = CHECKSUM_PARTIAL;
358 skb->csum = 0;
359
360 TCP_SKB_CB(skb)->tcp_flags = flags;
361 TCP_SKB_CB(skb)->sacked = 0;
362
363 skb_shinfo(skb)->gso_segs = 1;
364 skb_shinfo(skb)->gso_size = 0;
365 skb_shinfo(skb)->gso_type = 0;
366
367 TCP_SKB_CB(skb)->seq = seq;
368 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
369 seq++;
370 TCP_SKB_CB(skb)->end_seq = seq;
371}
372
373static inline bool tcp_urg_mode(const struct tcp_sock *tp)
374{
375 return tp->snd_una != tp->snd_up;
376}
377
378#define OPTION_SACK_ADVERTISE (1 << 0)
379#define OPTION_TS (1 << 1)
380#define OPTION_MD5 (1 << 2)
381#define OPTION_WSCALE (1 << 3)
382#define OPTION_COOKIE_EXTENSION (1 << 4)
383
384struct tcp_out_options {
385 u8 options; /* bit field of OPTION_* */
386 u8 ws; /* window scale, 0 to disable */
387 u8 num_sack_blocks; /* number of SACK blocks to include */
388 u8 hash_size; /* bytes in hash_location */
389 u16 mss; /* 0 to disable */
390 __u32 tsval, tsecr; /* need to include OPTION_TS */
391 __u8 *hash_location; /* temporary pointer, overloaded */
392};
393
394/* The sysctl int routines are generic, so check consistency here.
395 */
396static u8 tcp_cookie_size_check(u8 desired)
397{
398 int cookie_size;
399
400 if (desired > 0)
401 /* previously specified */
402 return desired;
403
404 cookie_size = ACCESS_ONCE(sysctl_tcp_cookie_size);
405 if (cookie_size <= 0)
406 /* no default specified */
407 return 0;
408
409 if (cookie_size <= TCP_COOKIE_MIN)
410 /* value too small, specify minimum */
411 return TCP_COOKIE_MIN;
412
413 if (cookie_size >= TCP_COOKIE_MAX)
414 /* value too large, specify maximum */
415 return TCP_COOKIE_MAX;
416
417 if (cookie_size & 1)
418 /* 8-bit multiple, illegal, fix it */
419 cookie_size++;
420
421 return (u8)cookie_size;
422}
423
424/* Write previously computed TCP options to the packet.
425 *
426 * Beware: Something in the Internet is very sensitive to the ordering of
427 * TCP options, we learned this through the hard way, so be careful here.
428 * Luckily we can at least blame others for their non-compliance but from
429 * inter-operatibility perspective it seems that we're somewhat stuck with
430 * the ordering which we have been using if we want to keep working with
431 * those broken things (not that it currently hurts anybody as there isn't
432 * particular reason why the ordering would need to be changed).
433 *
434 * At least SACK_PERM as the first option is known to lead to a disaster
435 * (but it may well be that other scenarios fail similarly).
436 */
437static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
438 struct tcp_out_options *opts)
439{
440 u8 options = opts->options; /* mungable copy */
441
442 /* Having both authentication and cookies for security is redundant,
443 * and there's certainly not enough room. Instead, the cookie-less
444 * extension variant is proposed.
445 *
446 * Consider the pessimal case with authentication. The options
447 * could look like:
448 * COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40
449 */
450 if (unlikely(OPTION_MD5 & options)) {
451 if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
452 *ptr++ = htonl((TCPOPT_COOKIE << 24) |
453 (TCPOLEN_COOKIE_BASE << 16) |
454 (TCPOPT_MD5SIG << 8) |
455 TCPOLEN_MD5SIG);
456 } else {
457 *ptr++ = htonl((TCPOPT_NOP << 24) |
458 (TCPOPT_NOP << 16) |
459 (TCPOPT_MD5SIG << 8) |
460 TCPOLEN_MD5SIG);
461 }
462 options &= ~OPTION_COOKIE_EXTENSION;
463 /* overload cookie hash location */
464 opts->hash_location = (__u8 *)ptr;
465 ptr += 4;
466 }
467
468 if (unlikely(opts->mss)) {
469 *ptr++ = htonl((TCPOPT_MSS << 24) |
470 (TCPOLEN_MSS << 16) |
471 opts->mss);
472 }
473
474 if (likely(OPTION_TS & options)) {
475 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
476 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
477 (TCPOLEN_SACK_PERM << 16) |
478 (TCPOPT_TIMESTAMP << 8) |
479 TCPOLEN_TIMESTAMP);
480 options &= ~OPTION_SACK_ADVERTISE;
481 } else {
482 *ptr++ = htonl((TCPOPT_NOP << 24) |
483 (TCPOPT_NOP << 16) |
484 (TCPOPT_TIMESTAMP << 8) |
485 TCPOLEN_TIMESTAMP);
486 }
487 *ptr++ = htonl(opts->tsval);
488 *ptr++ = htonl(opts->tsecr);
489 }
490
491 /* Specification requires after timestamp, so do it now.
492 *
493 * Consider the pessimal case without authentication. The options
494 * could look like:
495 * MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40
496 */
497 if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
498 __u8 *cookie_copy = opts->hash_location;
499 u8 cookie_size = opts->hash_size;
500
501 /* 8-bit multiple handled in tcp_cookie_size_check() above,
502 * and elsewhere.
503 */
504 if (0x2 & cookie_size) {
505 __u8 *p = (__u8 *)ptr;
506
507 /* 16-bit multiple */
508 *p++ = TCPOPT_COOKIE;
509 *p++ = TCPOLEN_COOKIE_BASE + cookie_size;
510 *p++ = *cookie_copy++;
511 *p++ = *cookie_copy++;
512 ptr++;
513 cookie_size -= 2;
514 } else {
515 /* 32-bit multiple */
516 *ptr++ = htonl(((TCPOPT_NOP << 24) |
517 (TCPOPT_NOP << 16) |
518 (TCPOPT_COOKIE << 8) |
519 TCPOLEN_COOKIE_BASE) +
520 cookie_size);
521 }
522
523 if (cookie_size > 0) {
524 memcpy(ptr, cookie_copy, cookie_size);
525 ptr += (cookie_size / 4);
526 }
527 }
528
529 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
530 *ptr++ = htonl((TCPOPT_NOP << 24) |
531 (TCPOPT_NOP << 16) |
532 (TCPOPT_SACK_PERM << 8) |
533 TCPOLEN_SACK_PERM);
534 }
535
536 if (unlikely(OPTION_WSCALE & options)) {
537 *ptr++ = htonl((TCPOPT_NOP << 24) |
538 (TCPOPT_WINDOW << 16) |
539 (TCPOLEN_WINDOW << 8) |
540 opts->ws);
541 }
542
543 if (unlikely(opts->num_sack_blocks)) {
544 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
545 tp->duplicate_sack : tp->selective_acks;
546 int this_sack;
547
548 *ptr++ = htonl((TCPOPT_NOP << 24) |
549 (TCPOPT_NOP << 16) |
550 (TCPOPT_SACK << 8) |
551 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
552 TCPOLEN_SACK_PERBLOCK)));
553
554 for (this_sack = 0; this_sack < opts->num_sack_blocks;
555 ++this_sack) {
556 *ptr++ = htonl(sp[this_sack].start_seq);
557 *ptr++ = htonl(sp[this_sack].end_seq);
558 }
559
560 tp->rx_opt.dsack = 0;
561 }
562}
563
564/* Compute TCP options for SYN packets. This is not the final
565 * network wire format yet.
566 */
567static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
568 struct tcp_out_options *opts,
569 struct tcp_md5sig_key **md5)
570{
571 struct tcp_sock *tp = tcp_sk(sk);
572 struct tcp_cookie_values *cvp = tp->cookie_values;
573 unsigned int remaining = MAX_TCP_OPTION_SPACE;
574 u8 cookie_size = (!tp->rx_opt.cookie_out_never && cvp != NULL) ?
575 tcp_cookie_size_check(cvp->cookie_desired) :
576 0;
577
578#ifdef CONFIG_TCP_MD5SIG
579 *md5 = tp->af_specific->md5_lookup(sk, sk);
580 if (*md5) {
581 opts->options |= OPTION_MD5;
582 remaining -= TCPOLEN_MD5SIG_ALIGNED;
583 }
584#else
585 *md5 = NULL;
586#endif
587
588 /* We always get an MSS option. The option bytes which will be seen in
589 * normal data packets should timestamps be used, must be in the MSS
590 * advertised. But we subtract them from tp->mss_cache so that
591 * calculations in tcp_sendmsg are simpler etc. So account for this
592 * fact here if necessary. If we don't do this correctly, as a
593 * receiver we won't recognize data packets as being full sized when we
594 * should, and thus we won't abide by the delayed ACK rules correctly.
595 * SACKs don't matter, we never delay an ACK when we have any of those
596 * going out. */
597 opts->mss = tcp_advertise_mss(sk);
598 remaining -= TCPOLEN_MSS_ALIGNED;
599
600 if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
601 opts->options |= OPTION_TS;
602 opts->tsval = TCP_SKB_CB(skb)->when;
603 opts->tsecr = tp->rx_opt.ts_recent;
604 remaining -= TCPOLEN_TSTAMP_ALIGNED;
605 }
606 if (likely(sysctl_tcp_window_scaling)) {
607 opts->ws = tp->rx_opt.rcv_wscale;
608 opts->options |= OPTION_WSCALE;
609 remaining -= TCPOLEN_WSCALE_ALIGNED;
610 }
611 if (likely(sysctl_tcp_sack)) {
612 opts->options |= OPTION_SACK_ADVERTISE;
613 if (unlikely(!(OPTION_TS & opts->options)))
614 remaining -= TCPOLEN_SACKPERM_ALIGNED;
615 }
616
617 /* Note that timestamps are required by the specification.
618 *
619 * Odd numbers of bytes are prohibited by the specification, ensuring
620 * that the cookie is 16-bit aligned, and the resulting cookie pair is
621 * 32-bit aligned.
622 */
623 if (*md5 == NULL &&
624 (OPTION_TS & opts->options) &&
625 cookie_size > 0) {
626 int need = TCPOLEN_COOKIE_BASE + cookie_size;
627
628 if (0x2 & need) {
629 /* 32-bit multiple */
630 need += 2; /* NOPs */
631
632 if (need > remaining) {
633 /* try shrinking cookie to fit */
634 cookie_size -= 2;
635 need -= 4;
636 }
637 }
638 while (need > remaining && TCP_COOKIE_MIN <= cookie_size) {
639 cookie_size -= 4;
640 need -= 4;
641 }
642 if (TCP_COOKIE_MIN <= cookie_size) {
643 opts->options |= OPTION_COOKIE_EXTENSION;
644 opts->hash_location = (__u8 *)&cvp->cookie_pair[0];
645 opts->hash_size = cookie_size;
646
647 /* Remember for future incarnations. */
648 cvp->cookie_desired = cookie_size;
649
650 if (cvp->cookie_desired != cvp->cookie_pair_size) {
651 /* Currently use random bytes as a nonce,
652 * assuming these are completely unpredictable
653 * by hostile users of the same system.
654 */
655 get_random_bytes(&cvp->cookie_pair[0],
656 cookie_size);
657 cvp->cookie_pair_size = cookie_size;
658 }
659
660 remaining -= need;
661 }
662 }
663 return MAX_TCP_OPTION_SPACE - remaining;
664}
665
666/* Set up TCP options for SYN-ACKs. */
667static unsigned int tcp_synack_options(struct sock *sk,
668 struct request_sock *req,
669 unsigned int mss, struct sk_buff *skb,
670 struct tcp_out_options *opts,
671 struct tcp_md5sig_key **md5,
672 struct tcp_extend_values *xvp)
673{
674 struct inet_request_sock *ireq = inet_rsk(req);
675 unsigned int remaining = MAX_TCP_OPTION_SPACE;
676 u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ?
677 xvp->cookie_plus :
678 0;
679
680#ifdef CONFIG_TCP_MD5SIG
681 *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
682 if (*md5) {
683 opts->options |= OPTION_MD5;
684 remaining -= TCPOLEN_MD5SIG_ALIGNED;
685
686 /* We can't fit any SACK blocks in a packet with MD5 + TS
687 * options. There was discussion about disabling SACK
688 * rather than TS in order to fit in better with old,
689 * buggy kernels, but that was deemed to be unnecessary.
690 */
691 ireq->tstamp_ok &= !ireq->sack_ok;
692 }
693#else
694 *md5 = NULL;
695#endif
696
697 /* We always send an MSS option. */
698 opts->mss = mss;
699 remaining -= TCPOLEN_MSS_ALIGNED;
700
701 if (likely(ireq->wscale_ok)) {
702 opts->ws = ireq->rcv_wscale;
703 opts->options |= OPTION_WSCALE;
704 remaining -= TCPOLEN_WSCALE_ALIGNED;
705 }
706 if (likely(ireq->tstamp_ok)) {
707 opts->options |= OPTION_TS;
708 opts->tsval = TCP_SKB_CB(skb)->when;
709 opts->tsecr = req->ts_recent;
710 remaining -= TCPOLEN_TSTAMP_ALIGNED;
711 }
712 if (likely(ireq->sack_ok)) {
713 opts->options |= OPTION_SACK_ADVERTISE;
714 if (unlikely(!ireq->tstamp_ok))
715 remaining -= TCPOLEN_SACKPERM_ALIGNED;
716 }
717
718 /* Similar rationale to tcp_syn_options() applies here, too.
719 * If the <SYN> options fit, the same options should fit now!
720 */
721 if (*md5 == NULL &&
722 ireq->tstamp_ok &&
723 cookie_plus > TCPOLEN_COOKIE_BASE) {
724 int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */
725
726 if (0x2 & need) {
727 /* 32-bit multiple */
728 need += 2; /* NOPs */
729 }
730 if (need <= remaining) {
731 opts->options |= OPTION_COOKIE_EXTENSION;
732 opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE;
733 remaining -= need;
734 } else {
735 /* There's no error return, so flag it. */
736 xvp->cookie_out_never = 1; /* true */
737 opts->hash_size = 0;
738 }
739 }
740 return MAX_TCP_OPTION_SPACE - remaining;
741}
742
743/* Compute TCP options for ESTABLISHED sockets. This is not the
744 * final wire format yet.
745 */
746static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
747 struct tcp_out_options *opts,
748 struct tcp_md5sig_key **md5)
749{
750 struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
751 struct tcp_sock *tp = tcp_sk(sk);
752 unsigned int size = 0;
753 unsigned int eff_sacks;
754
755#ifdef CONFIG_TCP_MD5SIG
756 *md5 = tp->af_specific->md5_lookup(sk, sk);
757 if (unlikely(*md5)) {
758 opts->options |= OPTION_MD5;
759 size += TCPOLEN_MD5SIG_ALIGNED;
760 }
761#else
762 *md5 = NULL;
763#endif
764
765 if (likely(tp->rx_opt.tstamp_ok)) {
766 opts->options |= OPTION_TS;
767 opts->tsval = tcb ? tcb->when : 0;
768 opts->tsecr = tp->rx_opt.ts_recent;
769 size += TCPOLEN_TSTAMP_ALIGNED;
770 }
771
772 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
773 if (unlikely(eff_sacks)) {
774 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
775 opts->num_sack_blocks =
776 min_t(unsigned int, eff_sacks,
777 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
778 TCPOLEN_SACK_PERBLOCK);
779 size += TCPOLEN_SACK_BASE_ALIGNED +
780 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
781 }
782
783 return size;
784}
785
786/* This routine actually transmits TCP packets queued in by
787 * tcp_do_sendmsg(). This is used by both the initial
788 * transmission and possible later retransmissions.
789 * All SKB's seen here are completely headerless. It is our
790 * job to build the TCP header, and pass the packet down to
791 * IP so it can do the same plus pass the packet off to the
792 * device.
793 *
794 * We are working here with either a clone of the original
795 * SKB, or a fresh unique copy made by the retransmit engine.
796 */
797static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
798 gfp_t gfp_mask)
799{
800 const struct inet_connection_sock *icsk = inet_csk(sk);
801 struct inet_sock *inet;
802 struct tcp_sock *tp;
803 struct tcp_skb_cb *tcb;
804 struct tcp_out_options opts;
805 unsigned int tcp_options_size, tcp_header_size;
806 struct tcp_md5sig_key *md5;
807 struct tcphdr *th;
808 int err;
809
810 BUG_ON(!skb || !tcp_skb_pcount(skb));
811
812 /* If congestion control is doing timestamping, we must
813 * take such a timestamp before we potentially clone/copy.
814 */
815 if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP)
816 __net_timestamp(skb);
817
818 if (likely(clone_it)) {
819 if (unlikely(skb_cloned(skb)))
820 skb = pskb_copy(skb, gfp_mask);
821 else
822 skb = skb_clone(skb, gfp_mask);
823 if (unlikely(!skb))
824 return -ENOBUFS;
825 }
826
827 inet = inet_sk(sk);
828 tp = tcp_sk(sk);
829 tcb = TCP_SKB_CB(skb);
830 memset(&opts, 0, sizeof(opts));
831
832 if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
833 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
834 else
835 tcp_options_size = tcp_established_options(sk, skb, &opts,
836 &md5);
837 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
838
839 if (tcp_packets_in_flight(tp) == 0) {
840 tcp_ca_event(sk, CA_EVENT_TX_START);
841 skb->ooo_okay = 1;
842 } else
843 skb->ooo_okay = 0;
844
845 skb_push(skb, tcp_header_size);
846 skb_reset_transport_header(skb);
847 skb_set_owner_w(skb, sk);
848
849 /* Build TCP header and checksum it. */
850 th = tcp_hdr(skb);
851 th->source = inet->inet_sport;
852 th->dest = inet->inet_dport;
853 th->seq = htonl(tcb->seq);
854 th->ack_seq = htonl(tp->rcv_nxt);
855 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
856 tcb->tcp_flags);
857
858 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
859 /* RFC1323: The window in SYN & SYN/ACK segments
860 * is never scaled.
861 */
862 th->window = htons(min(tp->rcv_wnd, 65535U));
863 } else {
864 th->window = htons(tcp_select_window(sk));
865 }
866 th->check = 0;
867 th->urg_ptr = 0;
868
869 /* The urg_mode check is necessary during a below snd_una win probe */
870 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
871 if (before(tp->snd_up, tcb->seq + 0x10000)) {
872 th->urg_ptr = htons(tp->snd_up - tcb->seq);
873 th->urg = 1;
874 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
875 th->urg_ptr = htons(0xFFFF);
876 th->urg = 1;
877 }
878 }
879
880 tcp_options_write((__be32 *)(th + 1), tp, &opts);
881 if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
882 TCP_ECN_send(sk, skb, tcp_header_size);
883
884#ifdef CONFIG_TCP_MD5SIG
885 /* Calculate the MD5 hash, as we have all we need now */
886 if (md5) {
887 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
888 tp->af_specific->calc_md5_hash(opts.hash_location,
889 md5, sk, NULL, skb);
890 }
891#endif
892
893 icsk->icsk_af_ops->send_check(sk, skb);
894
895 if (likely(tcb->tcp_flags & TCPHDR_ACK))
896 tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
897
898 if (skb->len != tcp_header_size)
899 tcp_event_data_sent(tp, sk);
900
901 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
902 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
903 tcp_skb_pcount(skb));
904
905 err = icsk->icsk_af_ops->queue_xmit(skb, &inet->cork.fl);
906 if (likely(err <= 0))
907 return err;
908
909 tcp_enter_cwr(sk, 1);
910
911 return net_xmit_eval(err);
912}
913
914/* This routine just queues the buffer for sending.
915 *
916 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
917 * otherwise socket can stall.
918 */
919static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
920{
921 struct tcp_sock *tp = tcp_sk(sk);
922
923 /* Advance write_seq and place onto the write_queue. */
924 tp->write_seq = TCP_SKB_CB(skb)->end_seq;
925 skb_header_release(skb);
926 tcp_add_write_queue_tail(sk, skb);
927 sk->sk_wmem_queued += skb->truesize;
928 sk_mem_charge(sk, skb->truesize);
929}
930
931/* Initialize TSO segments for a packet. */
932static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
933 unsigned int mss_now)
934{
935 if (skb->len <= mss_now || !sk_can_gso(sk) ||
936 skb->ip_summed == CHECKSUM_NONE) {
937 /* Avoid the costly divide in the normal
938 * non-TSO case.
939 */
940 skb_shinfo(skb)->gso_segs = 1;
941 skb_shinfo(skb)->gso_size = 0;
942 skb_shinfo(skb)->gso_type = 0;
943 } else {
944 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
945 skb_shinfo(skb)->gso_size = mss_now;
946 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
947 }
948}
949
950/* When a modification to fackets out becomes necessary, we need to check
951 * skb is counted to fackets_out or not.
952 */
953static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
954 int decr)
955{
956 struct tcp_sock *tp = tcp_sk(sk);
957
958 if (!tp->sacked_out || tcp_is_reno(tp))
959 return;
960
961 if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
962 tp->fackets_out -= decr;
963}
964
965/* Pcount in the middle of the write queue got changed, we need to do various
966 * tweaks to fix counters
967 */
968static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
969{
970 struct tcp_sock *tp = tcp_sk(sk);
971
972 tp->packets_out -= decr;
973
974 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
975 tp->sacked_out -= decr;
976 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
977 tp->retrans_out -= decr;
978 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
979 tp->lost_out -= decr;
980
981 /* Reno case is special. Sigh... */
982 if (tcp_is_reno(tp) && decr > 0)
983 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
984
985 tcp_adjust_fackets_out(sk, skb, decr);
986
987 if (tp->lost_skb_hint &&
988 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
989 (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
990 tp->lost_cnt_hint -= decr;
991
992 tcp_verify_left_out(tp);
993}
994
995/* Function to create two new TCP segments. Shrinks the given segment
996 * to the specified size and appends a new segment with the rest of the
997 * packet to the list. This won't be called frequently, I hope.
998 * Remember, these are still headerless SKBs at this point.
999 */
1000int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1001 unsigned int mss_now)
1002{
1003 struct tcp_sock *tp = tcp_sk(sk);
1004 struct sk_buff *buff;
1005 int nsize, old_factor;
1006 int nlen;
1007 u8 flags;
1008
1009 if (WARN_ON(len > skb->len))
1010 return -EINVAL;
1011
1012 nsize = skb_headlen(skb) - len;
1013 if (nsize < 0)
1014 nsize = 0;
1015
1016 if (skb_cloned(skb) &&
1017 skb_is_nonlinear(skb) &&
1018 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
1019 return -ENOMEM;
1020
1021 /* Get a new skb... force flag on. */
1022 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
1023 if (buff == NULL)
1024 return -ENOMEM; /* We'll just try again later. */
1025
1026 sk->sk_wmem_queued += buff->truesize;
1027 sk_mem_charge(sk, buff->truesize);
1028 nlen = skb->len - len - nsize;
1029 buff->truesize += nlen;
1030 skb->truesize -= nlen;
1031
1032 /* Correct the sequence numbers. */
1033 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1034 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1035 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1036
1037 /* PSH and FIN should only be set in the second packet. */
1038 flags = TCP_SKB_CB(skb)->tcp_flags;
1039 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1040 TCP_SKB_CB(buff)->tcp_flags = flags;
1041 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1042
1043 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
1044 /* Copy and checksum data tail into the new buffer. */
1045 buff->csum = csum_partial_copy_nocheck(skb->data + len,
1046 skb_put(buff, nsize),
1047 nsize, 0);
1048
1049 skb_trim(skb, len);
1050
1051 skb->csum = csum_block_sub(skb->csum, buff->csum, len);
1052 } else {
1053 skb->ip_summed = CHECKSUM_PARTIAL;
1054 skb_split(skb, buff, len);
1055 }
1056
1057 buff->ip_summed = skb->ip_summed;
1058
1059 /* Looks stupid, but our code really uses when of
1060 * skbs, which it never sent before. --ANK
1061 */
1062 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
1063 buff->tstamp = skb->tstamp;
1064
1065 old_factor = tcp_skb_pcount(skb);
1066
1067 /* Fix up tso_factor for both original and new SKB. */
1068 tcp_set_skb_tso_segs(sk, skb, mss_now);
1069 tcp_set_skb_tso_segs(sk, buff, mss_now);
1070
1071 /* If this packet has been sent out already, we must
1072 * adjust the various packet counters.
1073 */
1074 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1075 int diff = old_factor - tcp_skb_pcount(skb) -
1076 tcp_skb_pcount(buff);
1077
1078 if (diff)
1079 tcp_adjust_pcount(sk, skb, diff);
1080 }
1081
1082 /* Link BUFF into the send queue. */
1083 skb_header_release(buff);
1084 tcp_insert_write_queue_after(skb, buff, sk);
1085
1086 return 0;
1087}
1088
1089/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1090 * eventually). The difference is that pulled data not copied, but
1091 * immediately discarded.
1092 */
1093static void __pskb_trim_head(struct sk_buff *skb, int len)
1094{
1095 int i, k, eat;
1096
1097 eat = min_t(int, len, skb_headlen(skb));
1098 if (eat) {
1099 __skb_pull(skb, eat);
1100 skb->avail_size -= eat;
1101 len -= eat;
1102 if (!len)
1103 return;
1104 }
1105 eat = len;
1106 k = 0;
1107 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
1108 int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
1109
1110 if (size <= eat) {
1111 skb_frag_unref(skb, i);
1112 eat -= size;
1113 } else {
1114 skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
1115 if (eat) {
1116 skb_shinfo(skb)->frags[k].page_offset += eat;
1117 skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat);
1118 eat = 0;
1119 }
1120 k++;
1121 }
1122 }
1123 skb_shinfo(skb)->nr_frags = k;
1124
1125 skb_reset_tail_pointer(skb);
1126 skb->data_len -= len;
1127 skb->len = skb->data_len;
1128}
1129
1130/* Remove acked data from a packet in the transmit queue. */
1131int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1132{
1133 if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
1134 return -ENOMEM;
1135
1136 __pskb_trim_head(skb, len);
1137
1138 TCP_SKB_CB(skb)->seq += len;
1139 skb->ip_summed = CHECKSUM_PARTIAL;
1140
1141 skb->truesize -= len;
1142 sk->sk_wmem_queued -= len;
1143 sk_mem_uncharge(sk, len);
1144 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1145
1146 /* Any change of skb->len requires recalculation of tso factor. */
1147 if (tcp_skb_pcount(skb) > 1)
1148 tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb));
1149
1150 return 0;
1151}
1152
1153/* Calculate MSS. Not accounting for SACKs here. */
1154int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1155{
1156 const struct tcp_sock *tp = tcp_sk(sk);
1157 const struct inet_connection_sock *icsk = inet_csk(sk);
1158 int mss_now;
1159
1160 /* Calculate base mss without TCP options:
1161 It is MMS_S - sizeof(tcphdr) of rfc1122
1162 */
1163 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1164
1165 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1166 if (icsk->icsk_af_ops->net_frag_header_len) {
1167 const struct dst_entry *dst = __sk_dst_get(sk);
1168
1169 if (dst && dst_allfrag(dst))
1170 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1171 }
1172
1173 /* Clamp it (mss_clamp does not include tcp options) */
1174 if (mss_now > tp->rx_opt.mss_clamp)
1175 mss_now = tp->rx_opt.mss_clamp;
1176
1177 /* Now subtract optional transport overhead */
1178 mss_now -= icsk->icsk_ext_hdr_len;
1179
1180 /* Then reserve room for full set of TCP options and 8 bytes of data */
1181 if (mss_now < 48)
1182 mss_now = 48;
1183
1184 /* Now subtract TCP options size, not including SACKs */
1185 mss_now -= tp->tcp_header_len - sizeof(struct tcphdr);
1186
1187 return mss_now;
1188}
1189
1190/* Inverse of above */
1191int tcp_mss_to_mtu(struct sock *sk, int mss)
1192{
1193 const struct tcp_sock *tp = tcp_sk(sk);
1194 const struct inet_connection_sock *icsk = inet_csk(sk);
1195 int mtu;
1196
1197 mtu = mss +
1198 tp->tcp_header_len +
1199 icsk->icsk_ext_hdr_len +
1200 icsk->icsk_af_ops->net_header_len;
1201
1202 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1203 if (icsk->icsk_af_ops->net_frag_header_len) {
1204 const struct dst_entry *dst = __sk_dst_get(sk);
1205
1206 if (dst && dst_allfrag(dst))
1207 mtu += icsk->icsk_af_ops->net_frag_header_len;
1208 }
1209 return mtu;
1210}
1211
1212/* MTU probing init per socket */
1213void tcp_mtup_init(struct sock *sk)
1214{
1215 struct tcp_sock *tp = tcp_sk(sk);
1216 struct inet_connection_sock *icsk = inet_csk(sk);
1217
1218 icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1;
1219 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1220 icsk->icsk_af_ops->net_header_len;
1221 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
1222 icsk->icsk_mtup.probe_size = 0;
1223}
1224EXPORT_SYMBOL(tcp_mtup_init);
1225
1226/* This function synchronize snd mss to current pmtu/exthdr set.
1227
1228 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1229 for TCP options, but includes only bare TCP header.
1230
1231 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1232 It is minimum of user_mss and mss received with SYN.
1233 It also does not include TCP options.
1234
1235 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1236
1237 tp->mss_cache is current effective sending mss, including
1238 all tcp options except for SACKs. It is evaluated,
1239 taking into account current pmtu, but never exceeds
1240 tp->rx_opt.mss_clamp.
1241
1242 NOTE1. rfc1122 clearly states that advertised MSS
1243 DOES NOT include either tcp or ip options.
1244
1245 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1246 are READ ONLY outside this function. --ANK (980731)
1247 */
1248unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1249{
1250 struct tcp_sock *tp = tcp_sk(sk);
1251 struct inet_connection_sock *icsk = inet_csk(sk);
1252 int mss_now;
1253
1254 if (icsk->icsk_mtup.search_high > pmtu)
1255 icsk->icsk_mtup.search_high = pmtu;
1256
1257 mss_now = tcp_mtu_to_mss(sk, pmtu);
1258 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1259
1260 /* And store cached results */
1261 icsk->icsk_pmtu_cookie = pmtu;
1262 if (icsk->icsk_mtup.enabled)
1263 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1264 tp->mss_cache = mss_now;
1265
1266 return mss_now;
1267}
1268EXPORT_SYMBOL(tcp_sync_mss);
1269
1270/* Compute the current effective MSS, taking SACKs and IP options,
1271 * and even PMTU discovery events into account.
1272 */
1273unsigned int tcp_current_mss(struct sock *sk)
1274{
1275 const struct tcp_sock *tp = tcp_sk(sk);
1276 const struct dst_entry *dst = __sk_dst_get(sk);
1277 u32 mss_now;
1278 unsigned int header_len;
1279 struct tcp_out_options opts;
1280 struct tcp_md5sig_key *md5;
1281
1282 mss_now = tp->mss_cache;
1283
1284 if (dst) {
1285 u32 mtu = dst_mtu(dst);
1286 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1287 mss_now = tcp_sync_mss(sk, mtu);
1288 }
1289
1290 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1291 sizeof(struct tcphdr);
1292 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1293 * some common options. If this is an odd packet (because we have SACK
1294 * blocks etc) then our calculated header_len will be different, and
1295 * we have to adjust mss_now correspondingly */
1296 if (header_len != tp->tcp_header_len) {
1297 int delta = (int) header_len - tp->tcp_header_len;
1298 mss_now -= delta;
1299 }
1300
1301 return mss_now;
1302}
1303
1304/* Congestion window validation. (RFC2861) */
1305static void tcp_cwnd_validate(struct sock *sk)
1306{
1307 struct tcp_sock *tp = tcp_sk(sk);
1308
1309 if (tp->packets_out >= tp->snd_cwnd) {
1310 /* Network is feed fully. */
1311 tp->snd_cwnd_used = 0;
1312 tp->snd_cwnd_stamp = tcp_time_stamp;
1313 } else {
1314 /* Network starves. */
1315 if (tp->packets_out > tp->snd_cwnd_used)
1316 tp->snd_cwnd_used = tp->packets_out;
1317
1318 if (sysctl_tcp_slow_start_after_idle &&
1319 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1320 tcp_cwnd_application_limited(sk);
1321 }
1322}
1323
1324/* Returns the portion of skb which can be sent right away without
1325 * introducing MSS oddities to segment boundaries. In rare cases where
1326 * mss_now != mss_cache, we will request caller to create a small skb
1327 * per input skb which could be mostly avoided here (if desired).
1328 *
1329 * We explicitly want to create a request for splitting write queue tail
1330 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
1331 * thus all the complexity (cwnd_len is always MSS multiple which we
1332 * return whenever allowed by the other factors). Basically we need the
1333 * modulo only when the receiver window alone is the limiting factor or
1334 * when we would be allowed to send the split-due-to-Nagle skb fully.
1335 */
1336static unsigned int tcp_mss_split_point(const struct sock *sk, const struct sk_buff *skb,
1337 unsigned int mss_now, unsigned int max_segs)
1338{
1339 const struct tcp_sock *tp = tcp_sk(sk);
1340 u32 needed, window, max_len;
1341
1342 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1343 max_len = mss_now * max_segs;
1344
1345 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1346 return max_len;
1347
1348 needed = min(skb->len, window);
1349
1350 if (max_len <= needed)
1351 return max_len;
1352
1353 return needed - needed % mss_now;
1354}
1355
1356/* Can at least one segment of SKB be sent right now, according to the
1357 * congestion window rules? If so, return how many segments are allowed.
1358 */
1359static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1360 const struct sk_buff *skb)
1361{
1362 u32 in_flight, cwnd;
1363
1364 /* Don't be strict about the congestion window for the final FIN. */
1365 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1366 tcp_skb_pcount(skb) == 1)
1367 return 1;
1368
1369 in_flight = tcp_packets_in_flight(tp);
1370 cwnd = tp->snd_cwnd;
1371 if (in_flight < cwnd)
1372 return (cwnd - in_flight);
1373
1374 return 0;
1375}
1376
1377/* Initialize TSO state of a skb.
1378 * This must be invoked the first time we consider transmitting
1379 * SKB onto the wire.
1380 */
1381static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb,
1382 unsigned int mss_now)
1383{
1384 int tso_segs = tcp_skb_pcount(skb);
1385
1386 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1387 tcp_set_skb_tso_segs(sk, skb, mss_now);
1388 tso_segs = tcp_skb_pcount(skb);
1389 }
1390 return tso_segs;
1391}
1392
1393/* Minshall's variant of the Nagle send check. */
1394static inline bool tcp_minshall_check(const struct tcp_sock *tp)
1395{
1396 return after(tp->snd_sml, tp->snd_una) &&
1397 !after(tp->snd_sml, tp->snd_nxt);
1398}
1399
1400/* Return false, if packet can be sent now without violation Nagle's rules:
1401 * 1. It is full sized.
1402 * 2. Or it contains FIN. (already checked by caller)
1403 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1404 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1405 * With Minshall's modification: all sent small packets are ACKed.
1406 */
1407static inline bool tcp_nagle_check(const struct tcp_sock *tp,
1408 const struct sk_buff *skb,
1409 unsigned int mss_now, int nonagle)
1410{
1411 return skb->len < mss_now &&
1412 ((nonagle & TCP_NAGLE_CORK) ||
1413 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1414}
1415
1416/* Return true if the Nagle test allows this packet to be
1417 * sent now.
1418 */
1419static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1420 unsigned int cur_mss, int nonagle)
1421{
1422 /* Nagle rule does not apply to frames, which sit in the middle of the
1423 * write_queue (they have no chances to get new data).
1424 *
1425 * This is implemented in the callers, where they modify the 'nonagle'
1426 * argument based upon the location of SKB in the send queue.
1427 */
1428 if (nonagle & TCP_NAGLE_PUSH)
1429 return true;
1430
1431 /* Don't use the nagle rule for urgent data (or for the final FIN).
1432 * Nagle can be ignored during F-RTO too (see RFC4138).
1433 */
1434 if (tcp_urg_mode(tp) || (tp->frto_counter == 2) ||
1435 (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1436 return true;
1437
1438 if (!tcp_nagle_check(tp, skb, cur_mss, nonagle))
1439 return true;
1440
1441 return false;
1442}
1443
1444/* Does at least the first segment of SKB fit into the send window? */
1445static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1446 const struct sk_buff *skb,
1447 unsigned int cur_mss)
1448{
1449 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1450
1451 if (skb->len > cur_mss)
1452 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1453
1454 return !after(end_seq, tcp_wnd_end(tp));
1455}
1456
1457/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1458 * should be put on the wire right now. If so, it returns the number of
1459 * packets allowed by the congestion window.
1460 */
1461static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1462 unsigned int cur_mss, int nonagle)
1463{
1464 const struct tcp_sock *tp = tcp_sk(sk);
1465 unsigned int cwnd_quota;
1466
1467 tcp_init_tso_segs(sk, skb, cur_mss);
1468
1469 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
1470 return 0;
1471
1472 cwnd_quota = tcp_cwnd_test(tp, skb);
1473 if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1474 cwnd_quota = 0;
1475
1476 return cwnd_quota;
1477}
1478
1479/* Test if sending is allowed right now. */
1480bool tcp_may_send_now(struct sock *sk)
1481{
1482 const struct tcp_sock *tp = tcp_sk(sk);
1483 struct sk_buff *skb = tcp_send_head(sk);
1484
1485 return skb &&
1486 tcp_snd_test(sk, skb, tcp_current_mss(sk),
1487 (tcp_skb_is_last(sk, skb) ?
1488 tp->nonagle : TCP_NAGLE_PUSH));
1489}
1490
1491/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1492 * which is put after SKB on the list. It is very much like
1493 * tcp_fragment() except that it may make several kinds of assumptions
1494 * in order to speed up the splitting operation. In particular, we
1495 * know that all the data is in scatter-gather pages, and that the
1496 * packet has never been sent out before (and thus is not cloned).
1497 */
1498static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1499 unsigned int mss_now, gfp_t gfp)
1500{
1501 struct sk_buff *buff;
1502 int nlen = skb->len - len;
1503 u8 flags;
1504
1505 /* All of a TSO frame must be composed of paged data. */
1506 if (skb->len != skb->data_len)
1507 return tcp_fragment(sk, skb, len, mss_now);
1508
1509 buff = sk_stream_alloc_skb(sk, 0, gfp);
1510 if (unlikely(buff == NULL))
1511 return -ENOMEM;
1512
1513 sk->sk_wmem_queued += buff->truesize;
1514 sk_mem_charge(sk, buff->truesize);
1515 buff->truesize += nlen;
1516 skb->truesize -= nlen;
1517
1518 /* Correct the sequence numbers. */
1519 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1520 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1521 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1522
1523 /* PSH and FIN should only be set in the second packet. */
1524 flags = TCP_SKB_CB(skb)->tcp_flags;
1525 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1526 TCP_SKB_CB(buff)->tcp_flags = flags;
1527
1528 /* This packet was never sent out yet, so no SACK bits. */
1529 TCP_SKB_CB(buff)->sacked = 0;
1530
1531 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1532 skb_split(skb, buff, len);
1533
1534 /* Fix up tso_factor for both original and new SKB. */
1535 tcp_set_skb_tso_segs(sk, skb, mss_now);
1536 tcp_set_skb_tso_segs(sk, buff, mss_now);
1537
1538 /* Link BUFF into the send queue. */
1539 skb_header_release(buff);
1540 tcp_insert_write_queue_after(skb, buff, sk);
1541
1542 return 0;
1543}
1544
1545/* Try to defer sending, if possible, in order to minimize the amount
1546 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1547 *
1548 * This algorithm is from John Heffner.
1549 */
1550static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1551{
1552 struct tcp_sock *tp = tcp_sk(sk);
1553 const struct inet_connection_sock *icsk = inet_csk(sk);
1554 u32 send_win, cong_win, limit, in_flight;
1555 int win_divisor;
1556
1557 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1558 goto send_now;
1559
1560 if (icsk->icsk_ca_state != TCP_CA_Open)
1561 goto send_now;
1562
1563 /* Defer for less than two clock ticks. */
1564 if (tp->tso_deferred &&
1565 (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1)
1566 goto send_now;
1567
1568 in_flight = tcp_packets_in_flight(tp);
1569
1570 BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1571
1572 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1573
1574 /* From in_flight test above, we know that cwnd > in_flight. */
1575 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1576
1577 limit = min(send_win, cong_win);
1578
1579 /* If a full-sized TSO skb can be sent, do it. */
1580 if (limit >= min_t(unsigned int, sk->sk_gso_max_size,
1581 sk->sk_gso_max_segs * tp->mss_cache))
1582 goto send_now;
1583
1584 /* Middle in queue won't get any more data, full sendable already? */
1585 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
1586 goto send_now;
1587
1588 win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
1589 if (win_divisor) {
1590 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1591
1592 /* If at least some fraction of a window is available,
1593 * just use it.
1594 */
1595 chunk /= win_divisor;
1596 if (limit >= chunk)
1597 goto send_now;
1598 } else {
1599 /* Different approach, try not to defer past a single
1600 * ACK. Receiver should ACK every other full sized
1601 * frame, so if we have space for more than 3 frames
1602 * then send now.
1603 */
1604 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
1605 goto send_now;
1606 }
1607
1608 /* Ok, it looks like it is advisable to defer. */
1609 tp->tso_deferred = 1 | (jiffies << 1);
1610
1611 return true;
1612
1613send_now:
1614 tp->tso_deferred = 0;
1615 return false;
1616}
1617
1618/* Create a new MTU probe if we are ready.
1619 * MTU probe is regularly attempting to increase the path MTU by
1620 * deliberately sending larger packets. This discovers routing
1621 * changes resulting in larger path MTUs.
1622 *
1623 * Returns 0 if we should wait to probe (no cwnd available),
1624 * 1 if a probe was sent,
1625 * -1 otherwise
1626 */
1627static int tcp_mtu_probe(struct sock *sk)
1628{
1629 struct tcp_sock *tp = tcp_sk(sk);
1630 struct inet_connection_sock *icsk = inet_csk(sk);
1631 struct sk_buff *skb, *nskb, *next;
1632 int len;
1633 int probe_size;
1634 int size_needed;
1635 int copy;
1636 int mss_now;
1637
1638 /* Not currently probing/verifying,
1639 * not in recovery,
1640 * have enough cwnd, and
1641 * not SACKing (the variable headers throw things off) */
1642 if (!icsk->icsk_mtup.enabled ||
1643 icsk->icsk_mtup.probe_size ||
1644 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
1645 tp->snd_cwnd < 11 ||
1646 tp->rx_opt.num_sacks || tp->rx_opt.dsack)
1647 return -1;
1648
1649 /* Very simple search strategy: just double the MSS. */
1650 mss_now = tcp_current_mss(sk);
1651 probe_size = 2 * tp->mss_cache;
1652 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1653 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
1654 /* TODO: set timer for probe_converge_event */
1655 return -1;
1656 }
1657
1658 /* Have enough data in the send queue to probe? */
1659 if (tp->write_seq - tp->snd_nxt < size_needed)
1660 return -1;
1661
1662 if (tp->snd_wnd < size_needed)
1663 return -1;
1664 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1665 return 0;
1666
1667 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1668 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
1669 if (!tcp_packets_in_flight(tp))
1670 return -1;
1671 else
1672 return 0;
1673 }
1674
1675 /* We're allowed to probe. Build it now. */
1676 if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL)
1677 return -1;
1678 sk->sk_wmem_queued += nskb->truesize;
1679 sk_mem_charge(sk, nskb->truesize);
1680
1681 skb = tcp_send_head(sk);
1682
1683 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
1684 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
1685 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
1686 TCP_SKB_CB(nskb)->sacked = 0;
1687 nskb->csum = 0;
1688 nskb->ip_summed = skb->ip_summed;
1689
1690 tcp_insert_write_queue_before(nskb, skb, sk);
1691
1692 len = 0;
1693 tcp_for_write_queue_from_safe(skb, next, sk) {
1694 copy = min_t(int, skb->len, probe_size - len);
1695 if (nskb->ip_summed)
1696 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
1697 else
1698 nskb->csum = skb_copy_and_csum_bits(skb, 0,
1699 skb_put(nskb, copy),
1700 copy, nskb->csum);
1701
1702 if (skb->len <= copy) {
1703 /* We've eaten all the data from this skb.
1704 * Throw it away. */
1705 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1706 tcp_unlink_write_queue(skb, sk);
1707 sk_wmem_free_skb(sk, skb);
1708 } else {
1709 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
1710 ~(TCPHDR_FIN|TCPHDR_PSH);
1711 if (!skb_shinfo(skb)->nr_frags) {
1712 skb_pull(skb, copy);
1713 if (skb->ip_summed != CHECKSUM_PARTIAL)
1714 skb->csum = csum_partial(skb->data,
1715 skb->len, 0);
1716 } else {
1717 __pskb_trim_head(skb, copy);
1718 tcp_set_skb_tso_segs(sk, skb, mss_now);
1719 }
1720 TCP_SKB_CB(skb)->seq += copy;
1721 }
1722
1723 len += copy;
1724
1725 if (len >= probe_size)
1726 break;
1727 }
1728 tcp_init_tso_segs(sk, nskb, nskb->len);
1729
1730 /* We're ready to send. If this fails, the probe will
1731 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1732 TCP_SKB_CB(nskb)->when = tcp_time_stamp;
1733 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
1734 /* Decrement cwnd here because we are sending
1735 * effectively two packets. */
1736 tp->snd_cwnd--;
1737 tcp_event_new_data_sent(sk, nskb);
1738
1739 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1740 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
1741 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
1742
1743 return 1;
1744 }
1745
1746 return -1;
1747}
1748
1749/* This routine writes packets to the network. It advances the
1750 * send_head. This happens as incoming acks open up the remote
1751 * window for us.
1752 *
1753 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1754 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1755 * account rare use of URG, this is not a big flaw.
1756 *
1757 * Returns true, if no segments are in flight and we have queued segments,
1758 * but cannot send anything now because of SWS or another problem.
1759 */
1760static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
1761 int push_one, gfp_t gfp)
1762{
1763 struct tcp_sock *tp = tcp_sk(sk);
1764 struct sk_buff *skb;
1765 unsigned int tso_segs, sent_pkts;
1766 int cwnd_quota;
1767 int result;
1768
1769 sent_pkts = 0;
1770
1771 if (!push_one) {
1772 /* Do MTU probing. */
1773 result = tcp_mtu_probe(sk);
1774 if (!result) {
1775 return false;
1776 } else if (result > 0) {
1777 sent_pkts = 1;
1778 }
1779 }
1780
1781 while ((skb = tcp_send_head(sk))) {
1782 unsigned int limit;
1783
1784 tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1785 BUG_ON(!tso_segs);
1786
1787 cwnd_quota = tcp_cwnd_test(tp, skb);
1788 if (!cwnd_quota)
1789 break;
1790
1791 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
1792 break;
1793
1794 if (tso_segs == 1) {
1795 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
1796 (tcp_skb_is_last(sk, skb) ?
1797 nonagle : TCP_NAGLE_PUSH))))
1798 break;
1799 } else {
1800 if (!push_one && tcp_tso_should_defer(sk, skb))
1801 break;
1802 }
1803
1804 limit = mss_now;
1805 if (tso_segs > 1 && !tcp_urg_mode(tp))
1806 limit = tcp_mss_split_point(sk, skb, mss_now,
1807 min_t(unsigned int,
1808 cwnd_quota,
1809 sk->sk_gso_max_segs));
1810
1811 if (skb->len > limit &&
1812 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
1813 break;
1814
1815 TCP_SKB_CB(skb)->when = tcp_time_stamp;
1816
1817 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
1818 break;
1819
1820 /* Advance the send_head. This one is sent out.
1821 * This call will increment packets_out.
1822 */
1823 tcp_event_new_data_sent(sk, skb);
1824
1825 tcp_minshall_update(tp, mss_now, skb);
1826 sent_pkts += tcp_skb_pcount(skb);
1827
1828 if (push_one)
1829 break;
1830 }
1831 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Recovery)
1832 tp->prr_out += sent_pkts;
1833
1834 if (likely(sent_pkts)) {
1835 tcp_cwnd_validate(sk);
1836 return false;
1837 }
1838 return !tp->packets_out && tcp_send_head(sk);
1839}
1840
1841/* Push out any pending frames which were held back due to
1842 * TCP_CORK or attempt at coalescing tiny packets.
1843 * The socket must be locked by the caller.
1844 */
1845void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
1846 int nonagle)
1847{
1848 /* If we are closed, the bytes will have to remain here.
1849 * In time closedown will finish, we empty the write queue and
1850 * all will be happy.
1851 */
1852 if (unlikely(sk->sk_state == TCP_CLOSE))
1853 return;
1854
1855 if (tcp_write_xmit(sk, cur_mss, nonagle, 0, GFP_ATOMIC))
1856 tcp_check_probe_timer(sk);
1857}
1858
1859/* Send _single_ skb sitting at the send head. This function requires
1860 * true push pending frames to setup probe timer etc.
1861 */
1862void tcp_push_one(struct sock *sk, unsigned int mss_now)
1863{
1864 struct sk_buff *skb = tcp_send_head(sk);
1865
1866 BUG_ON(!skb || skb->len < mss_now);
1867
1868 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
1869}
1870
1871/* This function returns the amount that we can raise the
1872 * usable window based on the following constraints
1873 *
1874 * 1. The window can never be shrunk once it is offered (RFC 793)
1875 * 2. We limit memory per socket
1876 *
1877 * RFC 1122:
1878 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1879 * RECV.NEXT + RCV.WIN fixed until:
1880 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1881 *
1882 * i.e. don't raise the right edge of the window until you can raise
1883 * it at least MSS bytes.
1884 *
1885 * Unfortunately, the recommended algorithm breaks header prediction,
1886 * since header prediction assumes th->window stays fixed.
1887 *
1888 * Strictly speaking, keeping th->window fixed violates the receiver
1889 * side SWS prevention criteria. The problem is that under this rule
1890 * a stream of single byte packets will cause the right side of the
1891 * window to always advance by a single byte.
1892 *
1893 * Of course, if the sender implements sender side SWS prevention
1894 * then this will not be a problem.
1895 *
1896 * BSD seems to make the following compromise:
1897 *
1898 * If the free space is less than the 1/4 of the maximum
1899 * space available and the free space is less than 1/2 mss,
1900 * then set the window to 0.
1901 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1902 * Otherwise, just prevent the window from shrinking
1903 * and from being larger than the largest representable value.
1904 *
1905 * This prevents incremental opening of the window in the regime
1906 * where TCP is limited by the speed of the reader side taking
1907 * data out of the TCP receive queue. It does nothing about
1908 * those cases where the window is constrained on the sender side
1909 * because the pipeline is full.
1910 *
1911 * BSD also seems to "accidentally" limit itself to windows that are a
1912 * multiple of MSS, at least until the free space gets quite small.
1913 * This would appear to be a side effect of the mbuf implementation.
1914 * Combining these two algorithms results in the observed behavior
1915 * of having a fixed window size at almost all times.
1916 *
1917 * Below we obtain similar behavior by forcing the offered window to
1918 * a multiple of the mss when it is feasible to do so.
1919 *
1920 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1921 * Regular options like TIMESTAMP are taken into account.
1922 */
1923u32 __tcp_select_window(struct sock *sk)
1924{
1925 struct inet_connection_sock *icsk = inet_csk(sk);
1926 struct tcp_sock *tp = tcp_sk(sk);
1927 /* MSS for the peer's data. Previous versions used mss_clamp
1928 * here. I don't know if the value based on our guesses
1929 * of peer's MSS is better for the performance. It's more correct
1930 * but may be worse for the performance because of rcv_mss
1931 * fluctuations. --SAW 1998/11/1
1932 */
1933 int mss = icsk->icsk_ack.rcv_mss;
1934 int free_space = tcp_space(sk);
1935 int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk));
1936 int window;
1937
1938 if (mss > full_space)
1939 mss = full_space;
1940
1941 if (free_space < (full_space >> 1)) {
1942 icsk->icsk_ack.quick = 0;
1943
1944 if (sk_under_memory_pressure(sk))
1945 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
1946 4U * tp->advmss);
1947
1948 if (free_space < mss)
1949 return 0;
1950 }
1951
1952 if (free_space > tp->rcv_ssthresh)
1953 free_space = tp->rcv_ssthresh;
1954
1955 /* Don't do rounding if we are using window scaling, since the
1956 * scaled window will not line up with the MSS boundary anyway.
1957 */
1958 window = tp->rcv_wnd;
1959 if (tp->rx_opt.rcv_wscale) {
1960 window = free_space;
1961
1962 /* Advertise enough space so that it won't get scaled away.
1963 * Import case: prevent zero window announcement if
1964 * 1<<rcv_wscale > mss.
1965 */
1966 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
1967 window = (((window >> tp->rx_opt.rcv_wscale) + 1)
1968 << tp->rx_opt.rcv_wscale);
1969 } else {
1970 /* Get the largest window that is a nice multiple of mss.
1971 * Window clamp already applied above.
1972 * If our current window offering is within 1 mss of the
1973 * free space we just keep it. This prevents the divide
1974 * and multiply from happening most of the time.
1975 * We also don't do any window rounding when the free space
1976 * is too small.
1977 */
1978 if (window <= free_space - mss || window > free_space)
1979 window = (free_space / mss) * mss;
1980 else if (mss == full_space &&
1981 free_space > window + (full_space >> 1))
1982 window = free_space;
1983 }
1984
1985 return window;
1986}
1987
1988/* Collapses two adjacent SKB's during retransmission. */
1989static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
1990{
1991 struct tcp_sock *tp = tcp_sk(sk);
1992 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
1993 int skb_size, next_skb_size;
1994
1995 skb_size = skb->len;
1996 next_skb_size = next_skb->len;
1997
1998 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
1999
2000 tcp_highest_sack_combine(sk, next_skb, skb);
2001
2002 tcp_unlink_write_queue(next_skb, sk);
2003
2004 skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
2005 next_skb_size);
2006
2007 if (next_skb->ip_summed == CHECKSUM_PARTIAL)
2008 skb->ip_summed = CHECKSUM_PARTIAL;
2009
2010 if (skb->ip_summed != CHECKSUM_PARTIAL)
2011 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
2012
2013 /* Update sequence range on original skb. */
2014 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2015
2016 /* Merge over control information. This moves PSH/FIN etc. over */
2017 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2018
2019 /* All done, get rid of second SKB and account for it so
2020 * packet counting does not break.
2021 */
2022 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2023
2024 /* changed transmit queue under us so clear hints */
2025 tcp_clear_retrans_hints_partial(tp);
2026 if (next_skb == tp->retransmit_skb_hint)
2027 tp->retransmit_skb_hint = skb;
2028
2029 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2030
2031 sk_wmem_free_skb(sk, next_skb);
2032}
2033
2034/* Check if coalescing SKBs is legal. */
2035static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2036{
2037 if (tcp_skb_pcount(skb) > 1)
2038 return false;
2039 /* TODO: SACK collapsing could be used to remove this condition */
2040 if (skb_shinfo(skb)->nr_frags != 0)
2041 return false;
2042 if (skb_cloned(skb))
2043 return false;
2044 if (skb == tcp_send_head(sk))
2045 return false;
2046 /* Some heurestics for collapsing over SACK'd could be invented */
2047 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2048 return false;
2049
2050 return true;
2051}
2052
2053/* Collapse packets in the retransmit queue to make to create
2054 * less packets on the wire. This is only done on retransmission.
2055 */
2056static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2057 int space)
2058{
2059 struct tcp_sock *tp = tcp_sk(sk);
2060 struct sk_buff *skb = to, *tmp;
2061 bool first = true;
2062
2063 if (!sysctl_tcp_retrans_collapse)
2064 return;
2065 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2066 return;
2067
2068 tcp_for_write_queue_from_safe(skb, tmp, sk) {
2069 if (!tcp_can_collapse(sk, skb))
2070 break;
2071
2072 space -= skb->len;
2073
2074 if (first) {
2075 first = false;
2076 continue;
2077 }
2078
2079 if (space < 0)
2080 break;
2081 /* Punt if not enough space exists in the first SKB for
2082 * the data in the second
2083 */
2084 if (skb->len > skb_availroom(to))
2085 break;
2086
2087 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2088 break;
2089
2090 tcp_collapse_retrans(sk, to);
2091 }
2092}
2093
2094/* This retransmits one SKB. Policy decisions and retransmit queue
2095 * state updates are done by the caller. Returns non-zero if an
2096 * error occurred which prevented the send.
2097 */
2098int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2099{
2100 struct tcp_sock *tp = tcp_sk(sk);
2101 struct inet_connection_sock *icsk = inet_csk(sk);
2102 unsigned int cur_mss;
2103 int err;
2104
2105 /* Inconslusive MTU probe */
2106 if (icsk->icsk_mtup.probe_size) {
2107 icsk->icsk_mtup.probe_size = 0;
2108 }
2109
2110 /* Do not sent more than we queued. 1/4 is reserved for possible
2111 * copying overhead: fragmentation, tunneling, mangling etc.
2112 */
2113 if (atomic_read(&sk->sk_wmem_alloc) >
2114 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
2115 return -EAGAIN;
2116
2117 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2118 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
2119 BUG();
2120 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
2121 return -ENOMEM;
2122 }
2123
2124 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
2125 return -EHOSTUNREACH; /* Routing failure or similar. */
2126
2127 cur_mss = tcp_current_mss(sk);
2128
2129 /* If receiver has shrunk his window, and skb is out of
2130 * new window, do not retransmit it. The exception is the
2131 * case, when window is shrunk to zero. In this case
2132 * our retransmit serves as a zero window probe.
2133 */
2134 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
2135 TCP_SKB_CB(skb)->seq != tp->snd_una)
2136 return -EAGAIN;
2137
2138 if (skb->len > cur_mss) {
2139 if (tcp_fragment(sk, skb, cur_mss, cur_mss))
2140 return -ENOMEM; /* We'll try again later. */
2141 } else {
2142 int oldpcount = tcp_skb_pcount(skb);
2143
2144 if (unlikely(oldpcount > 1)) {
2145 tcp_init_tso_segs(sk, skb, cur_mss);
2146 tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
2147 }
2148 }
2149
2150 tcp_retrans_try_collapse(sk, skb, cur_mss);
2151
2152 /* Some Solaris stacks overoptimize and ignore the FIN on a
2153 * retransmit when old data is attached. So strip it off
2154 * since it is cheap to do so and saves bytes on the network.
2155 */
2156 if (skb->len > 0 &&
2157 (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
2158 tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
2159 if (!pskb_trim(skb, 0)) {
2160 /* Reuse, even though it does some unnecessary work */
2161 tcp_init_nondata_skb(skb, TCP_SKB_CB(skb)->end_seq - 1,
2162 TCP_SKB_CB(skb)->tcp_flags);
2163 skb->ip_summed = CHECKSUM_NONE;
2164 }
2165 }
2166
2167 /* Make a copy, if the first transmission SKB clone we made
2168 * is still in somebody's hands, else make a clone.
2169 */
2170 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2171
2172 /* make sure skb->data is aligned on arches that require it */
2173 if (unlikely(NET_IP_ALIGN && ((unsigned long)skb->data & 3))) {
2174 struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
2175 GFP_ATOMIC);
2176 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
2177 -ENOBUFS;
2178 } else {
2179 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2180 }
2181
2182 if (err == 0) {
2183 /* Update global TCP statistics. */
2184 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
2185
2186 tp->total_retrans++;
2187
2188#if FASTRETRANS_DEBUG > 0
2189 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2190 net_dbg_ratelimited("retrans_out leaked\n");
2191 }
2192#endif
2193 if (!tp->retrans_out)
2194 tp->lost_retrans_low = tp->snd_nxt;
2195 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
2196 tp->retrans_out += tcp_skb_pcount(skb);
2197
2198 /* Save stamp of the first retransmit. */
2199 if (!tp->retrans_stamp)
2200 tp->retrans_stamp = TCP_SKB_CB(skb)->when;
2201
2202 tp->undo_retrans += tcp_skb_pcount(skb);
2203
2204 /* snd_nxt is stored to detect loss of retransmitted segment,
2205 * see tcp_input.c tcp_sacktag_write_queue().
2206 */
2207 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
2208 }
2209 return err;
2210}
2211
2212/* Check if we forward retransmits are possible in the current
2213 * window/congestion state.
2214 */
2215static bool tcp_can_forward_retransmit(struct sock *sk)
2216{
2217 const struct inet_connection_sock *icsk = inet_csk(sk);
2218 const struct tcp_sock *tp = tcp_sk(sk);
2219
2220 /* Forward retransmissions are possible only during Recovery. */
2221 if (icsk->icsk_ca_state != TCP_CA_Recovery)
2222 return false;
2223
2224 /* No forward retransmissions in Reno are possible. */
2225 if (tcp_is_reno(tp))
2226 return false;
2227
2228 /* Yeah, we have to make difficult choice between forward transmission
2229 * and retransmission... Both ways have their merits...
2230 *
2231 * For now we do not retransmit anything, while we have some new
2232 * segments to send. In the other cases, follow rule 3 for
2233 * NextSeg() specified in RFC3517.
2234 */
2235
2236 if (tcp_may_send_now(sk))
2237 return false;
2238
2239 return true;
2240}
2241
2242/* This gets called after a retransmit timeout, and the initially
2243 * retransmitted data is acknowledged. It tries to continue
2244 * resending the rest of the retransmit queue, until either
2245 * we've sent it all or the congestion window limit is reached.
2246 * If doing SACK, the first ACK which comes back for a timeout
2247 * based retransmit packet might feed us FACK information again.
2248 * If so, we use it to avoid unnecessarily retransmissions.
2249 */
2250void tcp_xmit_retransmit_queue(struct sock *sk)
2251{
2252 const struct inet_connection_sock *icsk = inet_csk(sk);
2253 struct tcp_sock *tp = tcp_sk(sk);
2254 struct sk_buff *skb;
2255 struct sk_buff *hole = NULL;
2256 u32 last_lost;
2257 int mib_idx;
2258 int fwd_rexmitting = 0;
2259
2260 if (!tp->packets_out)
2261 return;
2262
2263 if (!tp->lost_out)
2264 tp->retransmit_high = tp->snd_una;
2265
2266 if (tp->retransmit_skb_hint) {
2267 skb = tp->retransmit_skb_hint;
2268 last_lost = TCP_SKB_CB(skb)->end_seq;
2269 if (after(last_lost, tp->retransmit_high))
2270 last_lost = tp->retransmit_high;
2271 } else {
2272 skb = tcp_write_queue_head(sk);
2273 last_lost = tp->snd_una;
2274 }
2275
2276 tcp_for_write_queue_from(skb, sk) {
2277 __u8 sacked = TCP_SKB_CB(skb)->sacked;
2278
2279 if (skb == tcp_send_head(sk))
2280 break;
2281 /* we could do better than to assign each time */
2282 if (hole == NULL)
2283 tp->retransmit_skb_hint = skb;
2284
2285 /* Assume this retransmit will generate
2286 * only one packet for congestion window
2287 * calculation purposes. This works because
2288 * tcp_retransmit_skb() will chop up the
2289 * packet to be MSS sized and all the
2290 * packet counting works out.
2291 */
2292 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
2293 return;
2294
2295 if (fwd_rexmitting) {
2296begin_fwd:
2297 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
2298 break;
2299 mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2300
2301 } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2302 tp->retransmit_high = last_lost;
2303 if (!tcp_can_forward_retransmit(sk))
2304 break;
2305 /* Backtrack if necessary to non-L'ed skb */
2306 if (hole != NULL) {
2307 skb = hole;
2308 hole = NULL;
2309 }
2310 fwd_rexmitting = 1;
2311 goto begin_fwd;
2312
2313 } else if (!(sacked & TCPCB_LOST)) {
2314 if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2315 hole = skb;
2316 continue;
2317
2318 } else {
2319 last_lost = TCP_SKB_CB(skb)->end_seq;
2320 if (icsk->icsk_ca_state != TCP_CA_Loss)
2321 mib_idx = LINUX_MIB_TCPFASTRETRANS;
2322 else
2323 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
2324 }
2325
2326 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
2327 continue;
2328
2329 if (tcp_retransmit_skb(sk, skb)) {
2330 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2331 return;
2332 }
2333 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2334
2335 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Recovery)
2336 tp->prr_out += tcp_skb_pcount(skb);
2337
2338 if (skb == tcp_write_queue_head(sk))
2339 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2340 inet_csk(sk)->icsk_rto,
2341 TCP_RTO_MAX);
2342 }
2343}
2344
2345/* Send a fin. The caller locks the socket for us. This cannot be
2346 * allowed to fail queueing a FIN frame under any circumstances.
2347 */
2348void tcp_send_fin(struct sock *sk)
2349{
2350 struct tcp_sock *tp = tcp_sk(sk);
2351 struct sk_buff *skb = tcp_write_queue_tail(sk);
2352 int mss_now;
2353
2354 /* Optimization, tack on the FIN if we have a queue of
2355 * unsent frames. But be careful about outgoing SACKS
2356 * and IP options.
2357 */
2358 mss_now = tcp_current_mss(sk);
2359
2360 if (tcp_send_head(sk) != NULL) {
2361 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_FIN;
2362 TCP_SKB_CB(skb)->end_seq++;
2363 tp->write_seq++;
2364 } else {
2365 /* Socket is locked, keep trying until memory is available. */
2366 for (;;) {
2367 skb = alloc_skb_fclone(MAX_TCP_HEADER,
2368 sk->sk_allocation);
2369 if (skb)
2370 break;
2371 yield();
2372 }
2373
2374 /* Reserve space for headers and prepare control bits. */
2375 skb_reserve(skb, MAX_TCP_HEADER);
2376 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2377 tcp_init_nondata_skb(skb, tp->write_seq,
2378 TCPHDR_ACK | TCPHDR_FIN);
2379 tcp_queue_skb(sk, skb);
2380 }
2381 __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
2382}
2383
2384/* We get here when a process closes a file descriptor (either due to
2385 * an explicit close() or as a byproduct of exit()'ing) and there
2386 * was unread data in the receive queue. This behavior is recommended
2387 * by RFC 2525, section 2.17. -DaveM
2388 */
2389void tcp_send_active_reset(struct sock *sk, gfp_t priority)
2390{
2391 struct sk_buff *skb;
2392
2393 /* NOTE: No TCP options attached and we never retransmit this. */
2394 skb = alloc_skb(MAX_TCP_HEADER, priority);
2395 if (!skb) {
2396 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2397 return;
2398 }
2399
2400 /* Reserve space for headers and prepare control bits. */
2401 skb_reserve(skb, MAX_TCP_HEADER);
2402 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
2403 TCPHDR_ACK | TCPHDR_RST);
2404 /* Send it off. */
2405 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2406 if (tcp_transmit_skb(sk, skb, 0, priority))
2407 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2408
2409 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
2410}
2411
2412/* Send a crossed SYN-ACK during socket establishment.
2413 * WARNING: This routine must only be called when we have already sent
2414 * a SYN packet that crossed the incoming SYN that caused this routine
2415 * to get called. If this assumption fails then the initial rcv_wnd
2416 * and rcv_wscale values will not be correct.
2417 */
2418int tcp_send_synack(struct sock *sk)
2419{
2420 struct sk_buff *skb;
2421
2422 skb = tcp_write_queue_head(sk);
2423 if (skb == NULL || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
2424 pr_debug("%s: wrong queue state\n", __func__);
2425 return -EFAULT;
2426 }
2427 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
2428 if (skb_cloned(skb)) {
2429 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
2430 if (nskb == NULL)
2431 return -ENOMEM;
2432 tcp_unlink_write_queue(skb, sk);
2433 skb_header_release(nskb);
2434 __tcp_add_write_queue_head(sk, nskb);
2435 sk_wmem_free_skb(sk, skb);
2436 sk->sk_wmem_queued += nskb->truesize;
2437 sk_mem_charge(sk, nskb->truesize);
2438 skb = nskb;
2439 }
2440
2441 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
2442 TCP_ECN_send_synack(tcp_sk(sk), skb);
2443 }
2444 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2445 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2446}
2447
2448/* Prepare a SYN-ACK. */
2449struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2450 struct request_sock *req,
2451 struct request_values *rvp)
2452{
2453 struct tcp_out_options opts;
2454 struct tcp_extend_values *xvp = tcp_xv(rvp);
2455 struct inet_request_sock *ireq = inet_rsk(req);
2456 struct tcp_sock *tp = tcp_sk(sk);
2457 const struct tcp_cookie_values *cvp = tp->cookie_values;
2458 struct tcphdr *th;
2459 struct sk_buff *skb;
2460 struct tcp_md5sig_key *md5;
2461 int tcp_header_size;
2462 int mss;
2463 int s_data_desired = 0;
2464
2465 if (cvp != NULL && cvp->s_data_constant && cvp->s_data_desired)
2466 s_data_desired = cvp->s_data_desired;
2467 skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15 + s_data_desired, 1, GFP_ATOMIC);
2468 if (skb == NULL)
2469 return NULL;
2470
2471 /* Reserve space for headers. */
2472 skb_reserve(skb, MAX_TCP_HEADER);
2473
2474 skb_dst_set(skb, dst_clone(dst));
2475
2476 mss = dst_metric_advmss(dst);
2477 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
2478 mss = tp->rx_opt.user_mss;
2479
2480 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
2481 __u8 rcv_wscale;
2482 /* Set this up on the first call only */
2483 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
2484
2485 /* limit the window selection if the user enforce a smaller rx buffer */
2486 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
2487 (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
2488 req->window_clamp = tcp_full_space(sk);
2489
2490 /* tcp_full_space because it is guaranteed to be the first packet */
2491 tcp_select_initial_window(tcp_full_space(sk),
2492 mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
2493 &req->rcv_wnd,
2494 &req->window_clamp,
2495 ireq->wscale_ok,
2496 &rcv_wscale,
2497 dst_metric(dst, RTAX_INITRWND));
2498 ireq->rcv_wscale = rcv_wscale;
2499 }
2500
2501 memset(&opts, 0, sizeof(opts));
2502#ifdef CONFIG_SYN_COOKIES
2503 if (unlikely(req->cookie_ts))
2504 TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
2505 else
2506#endif
2507 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2508 tcp_header_size = tcp_synack_options(sk, req, mss,
2509 skb, &opts, &md5, xvp)
2510 + sizeof(*th);
2511
2512 skb_push(skb, tcp_header_size);
2513 skb_reset_transport_header(skb);
2514
2515 th = tcp_hdr(skb);
2516 memset(th, 0, sizeof(struct tcphdr));
2517 th->syn = 1;
2518 th->ack = 1;
2519 TCP_ECN_make_synack(req, th);
2520 th->source = ireq->loc_port;
2521 th->dest = ireq->rmt_port;
2522 /* Setting of flags are superfluous here for callers (and ECE is
2523 * not even correctly set)
2524 */
2525 tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
2526 TCPHDR_SYN | TCPHDR_ACK);
2527
2528 if (OPTION_COOKIE_EXTENSION & opts.options) {
2529 if (s_data_desired) {
2530 u8 *buf = skb_put(skb, s_data_desired);
2531
2532 /* copy data directly from the listening socket. */
2533 memcpy(buf, cvp->s_data_payload, s_data_desired);
2534 TCP_SKB_CB(skb)->end_seq += s_data_desired;
2535 }
2536
2537 if (opts.hash_size > 0) {
2538 __u32 workspace[SHA_WORKSPACE_WORDS];
2539 u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS];
2540 u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1];
2541
2542 /* Secret recipe depends on the Timestamp, (future)
2543 * Sequence and Acknowledgment Numbers, Initiator
2544 * Cookie, and others handled by IP variant caller.
2545 */
2546 *tail-- ^= opts.tsval;
2547 *tail-- ^= tcp_rsk(req)->rcv_isn + 1;
2548 *tail-- ^= TCP_SKB_CB(skb)->seq + 1;
2549
2550 /* recommended */
2551 *tail-- ^= (((__force u32)th->dest << 16) | (__force u32)th->source);
2552 *tail-- ^= (u32)(unsigned long)cvp; /* per sockopt */
2553
2554 sha_transform((__u32 *)&xvp->cookie_bakery[0],
2555 (char *)mess,
2556 &workspace[0]);
2557 opts.hash_location =
2558 (__u8 *)&xvp->cookie_bakery[0];
2559 }
2560 }
2561
2562 th->seq = htonl(TCP_SKB_CB(skb)->seq);
2563 th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
2564
2565 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2566 th->window = htons(min(req->rcv_wnd, 65535U));
2567 tcp_options_write((__be32 *)(th + 1), tp, &opts);
2568 th->doff = (tcp_header_size >> 2);
2569 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, tcp_skb_pcount(skb));
2570
2571#ifdef CONFIG_TCP_MD5SIG
2572 /* Okay, we have all we need - do the md5 hash if needed */
2573 if (md5) {
2574 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
2575 md5, NULL, req, skb);
2576 }
2577#endif
2578
2579 return skb;
2580}
2581EXPORT_SYMBOL(tcp_make_synack);
2582
2583/* Do all connect socket setups that can be done AF independent. */
2584void tcp_connect_init(struct sock *sk)
2585{
2586 const struct dst_entry *dst = __sk_dst_get(sk);
2587 struct tcp_sock *tp = tcp_sk(sk);
2588 __u8 rcv_wscale;
2589
2590 /* We'll fix this up when we get a response from the other end.
2591 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2592 */
2593 tp->tcp_header_len = sizeof(struct tcphdr) +
2594 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
2595
2596#ifdef CONFIG_TCP_MD5SIG
2597 if (tp->af_specific->md5_lookup(sk, sk) != NULL)
2598 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
2599#endif
2600
2601 /* If user gave his TCP_MAXSEG, record it to clamp */
2602 if (tp->rx_opt.user_mss)
2603 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
2604 tp->max_window = 0;
2605 tcp_mtup_init(sk);
2606 tcp_sync_mss(sk, dst_mtu(dst));
2607
2608 if (!tp->window_clamp)
2609 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
2610 tp->advmss = dst_metric_advmss(dst);
2611 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
2612 tp->advmss = tp->rx_opt.user_mss;
2613
2614 tcp_initialize_rcv_mss(sk);
2615
2616 /* limit the window selection if the user enforce a smaller rx buffer */
2617 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
2618 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
2619 tp->window_clamp = tcp_full_space(sk);
2620
2621 tcp_select_initial_window(tcp_full_space(sk),
2622 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
2623 &tp->rcv_wnd,
2624 &tp->window_clamp,
2625 sysctl_tcp_window_scaling,
2626 &rcv_wscale,
2627 dst_metric(dst, RTAX_INITRWND));
2628
2629 tp->rx_opt.rcv_wscale = rcv_wscale;
2630 tp->rcv_ssthresh = tp->rcv_wnd;
2631
2632 sk->sk_err = 0;
2633 sock_reset_flag(sk, SOCK_DONE);
2634 tp->snd_wnd = 0;
2635 tcp_init_wl(tp, 0);
2636 tp->snd_una = tp->write_seq;
2637 tp->snd_sml = tp->write_seq;
2638 tp->snd_up = tp->write_seq;
2639 tp->snd_nxt = tp->write_seq;
2640
2641 if (likely(!tp->repair))
2642 tp->rcv_nxt = 0;
2643 tp->rcv_wup = tp->rcv_nxt;
2644 tp->copied_seq = tp->rcv_nxt;
2645
2646 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
2647 inet_csk(sk)->icsk_retransmits = 0;
2648 tcp_clear_retrans(tp);
2649}
2650
2651/* Build a SYN and send it off. */
2652int tcp_connect(struct sock *sk)
2653{
2654 struct tcp_sock *tp = tcp_sk(sk);
2655 struct sk_buff *buff;
2656 int err;
2657
2658 tcp_connect_init(sk);
2659
2660 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
2661 if (unlikely(buff == NULL))
2662 return -ENOBUFS;
2663
2664 /* Reserve space for headers. */
2665 skb_reserve(buff, MAX_TCP_HEADER);
2666
2667 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
2668 TCP_ECN_send_syn(sk, buff);
2669
2670 /* Send it off. */
2671 TCP_SKB_CB(buff)->when = tcp_time_stamp;
2672 tp->retrans_stamp = TCP_SKB_CB(buff)->when;
2673 skb_header_release(buff);
2674 __tcp_add_write_queue_tail(sk, buff);
2675 sk->sk_wmem_queued += buff->truesize;
2676 sk_mem_charge(sk, buff->truesize);
2677 tp->packets_out += tcp_skb_pcount(buff);
2678 err = tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
2679 if (err == -ECONNREFUSED)
2680 return err;
2681
2682 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2683 * in order to make this packet get counted in tcpOutSegs.
2684 */
2685 tp->snd_nxt = tp->write_seq;
2686 tp->pushed_seq = tp->write_seq;
2687 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
2688
2689 /* Timer for repeating the SYN until an answer. */
2690 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2691 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
2692 return 0;
2693}
2694EXPORT_SYMBOL(tcp_connect);
2695
2696/* Send out a delayed ack, the caller does the policy checking
2697 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
2698 * for details.
2699 */
2700void tcp_send_delayed_ack(struct sock *sk)
2701{
2702 struct inet_connection_sock *icsk = inet_csk(sk);
2703 int ato = icsk->icsk_ack.ato;
2704 unsigned long timeout;
2705
2706 if (ato > TCP_DELACK_MIN) {
2707 const struct tcp_sock *tp = tcp_sk(sk);
2708 int max_ato = HZ / 2;
2709
2710 if (icsk->icsk_ack.pingpong ||
2711 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
2712 max_ato = TCP_DELACK_MAX;
2713
2714 /* Slow path, intersegment interval is "high". */
2715
2716 /* If some rtt estimate is known, use it to bound delayed ack.
2717 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
2718 * directly.
2719 */
2720 if (tp->srtt) {
2721 int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN);
2722
2723 if (rtt < max_ato)
2724 max_ato = rtt;
2725 }
2726
2727 ato = min(ato, max_ato);
2728 }
2729
2730 /* Stay within the limit we were given */
2731 timeout = jiffies + ato;
2732
2733 /* Use new timeout only if there wasn't a older one earlier. */
2734 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
2735 /* If delack timer was blocked or is about to expire,
2736 * send ACK now.
2737 */
2738 if (icsk->icsk_ack.blocked ||
2739 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
2740 tcp_send_ack(sk);
2741 return;
2742 }
2743
2744 if (!time_before(timeout, icsk->icsk_ack.timeout))
2745 timeout = icsk->icsk_ack.timeout;
2746 }
2747 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
2748 icsk->icsk_ack.timeout = timeout;
2749 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
2750}
2751
2752/* This routine sends an ack and also updates the window. */
2753void tcp_send_ack(struct sock *sk)
2754{
2755 struct sk_buff *buff;
2756
2757 /* If we have been reset, we may not send again. */
2758 if (sk->sk_state == TCP_CLOSE)
2759 return;
2760
2761 /* We are not putting this on the write queue, so
2762 * tcp_transmit_skb() will set the ownership to this
2763 * sock.
2764 */
2765 buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2766 if (buff == NULL) {
2767 inet_csk_schedule_ack(sk);
2768 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
2769 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
2770 TCP_DELACK_MAX, TCP_RTO_MAX);
2771 return;
2772 }
2773
2774 /* Reserve space for headers and prepare control bits. */
2775 skb_reserve(buff, MAX_TCP_HEADER);
2776 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
2777
2778 /* Send it off, this clears delayed acks for us. */
2779 TCP_SKB_CB(buff)->when = tcp_time_stamp;
2780 tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC);
2781}
2782
2783/* This routine sends a packet with an out of date sequence
2784 * number. It assumes the other end will try to ack it.
2785 *
2786 * Question: what should we make while urgent mode?
2787 * 4.4BSD forces sending single byte of data. We cannot send
2788 * out of window data, because we have SND.NXT==SND.MAX...
2789 *
2790 * Current solution: to send TWO zero-length segments in urgent mode:
2791 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2792 * out-of-date with SND.UNA-1 to probe window.
2793 */
2794static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
2795{
2796 struct tcp_sock *tp = tcp_sk(sk);
2797 struct sk_buff *skb;
2798
2799 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2800 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2801 if (skb == NULL)
2802 return -1;
2803
2804 /* Reserve space for headers and set control bits. */
2805 skb_reserve(skb, MAX_TCP_HEADER);
2806 /* Use a previous sequence. This should cause the other
2807 * end to send an ack. Don't queue or clone SKB, just
2808 * send it.
2809 */
2810 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
2811 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2812 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
2813}
2814
2815void tcp_send_window_probe(struct sock *sk)
2816{
2817 if (sk->sk_state == TCP_ESTABLISHED) {
2818 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
2819 tcp_sk(sk)->snd_nxt = tcp_sk(sk)->write_seq;
2820 tcp_xmit_probe_skb(sk, 0);
2821 }
2822}
2823
2824/* Initiate keepalive or window probe from timer. */
2825int tcp_write_wakeup(struct sock *sk)
2826{
2827 struct tcp_sock *tp = tcp_sk(sk);
2828 struct sk_buff *skb;
2829
2830 if (sk->sk_state == TCP_CLOSE)
2831 return -1;
2832
2833 if ((skb = tcp_send_head(sk)) != NULL &&
2834 before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
2835 int err;
2836 unsigned int mss = tcp_current_mss(sk);
2837 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2838
2839 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
2840 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
2841
2842 /* We are probing the opening of a window
2843 * but the window size is != 0
2844 * must have been a result SWS avoidance ( sender )
2845 */
2846 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
2847 skb->len > mss) {
2848 seg_size = min(seg_size, mss);
2849 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
2850 if (tcp_fragment(sk, skb, seg_size, mss))
2851 return -1;
2852 } else if (!tcp_skb_pcount(skb))
2853 tcp_set_skb_tso_segs(sk, skb, mss);
2854
2855 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
2856 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2857 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2858 if (!err)
2859 tcp_event_new_data_sent(sk, skb);
2860 return err;
2861 } else {
2862 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
2863 tcp_xmit_probe_skb(sk, 1);
2864 return tcp_xmit_probe_skb(sk, 0);
2865 }
2866}
2867
2868/* A window probe timeout has occurred. If window is not closed send
2869 * a partial packet else a zero probe.
2870 */
2871void tcp_send_probe0(struct sock *sk)
2872{
2873 struct inet_connection_sock *icsk = inet_csk(sk);
2874 struct tcp_sock *tp = tcp_sk(sk);
2875 int err;
2876
2877 err = tcp_write_wakeup(sk);
2878
2879 if (tp->packets_out || !tcp_send_head(sk)) {
2880 /* Cancel probe timer, if it is not required. */
2881 icsk->icsk_probes_out = 0;
2882 icsk->icsk_backoff = 0;
2883 return;
2884 }
2885
2886 if (err <= 0) {
2887 if (icsk->icsk_backoff < sysctl_tcp_retries2)
2888 icsk->icsk_backoff++;
2889 icsk->icsk_probes_out++;
2890 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2891 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2892 TCP_RTO_MAX);
2893 } else {
2894 /* If packet was not sent due to local congestion,
2895 * do not backoff and do not remember icsk_probes_out.
2896 * Let local senders to fight for local resources.
2897 *
2898 * Use accumulated backoff yet.
2899 */
2900 if (!icsk->icsk_probes_out)
2901 icsk->icsk_probes_out = 1;
2902 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2903 min(icsk->icsk_rto << icsk->icsk_backoff,
2904 TCP_RESOURCE_PROBE_INTERVAL),
2905 TCP_RTO_MAX);
2906 }
2907}