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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * Implementation of the Transmission Control Protocol(TCP).
8 *
9 * Authors: Ross Biro
10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11 * Mark Evans, <evansmp@uhura.aston.ac.uk>
12 * Corey Minyard <wf-rch!minyard@relay.EU.net>
13 * Florian La Roche, <flla@stud.uni-sb.de>
14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
15 * Linus Torvalds, <torvalds@cs.helsinki.fi>
16 * Alan Cox, <gw4pts@gw4pts.ampr.org>
17 * Matthew Dillon, <dillon@apollo.west.oic.com>
18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
19 * Jorge Cwik, <jorge@laser.satlink.net>
20 */
21
22/*
23 * Changes: Pedro Roque : Retransmit queue handled by TCP.
24 * : Fragmentation on mtu decrease
25 * : Segment collapse on retransmit
26 * : AF independence
27 *
28 * Linus Torvalds : send_delayed_ack
29 * David S. Miller : Charge memory using the right skb
30 * during syn/ack processing.
31 * David S. Miller : Output engine completely rewritten.
32 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
33 * Cacophonix Gaul : draft-minshall-nagle-01
34 * J Hadi Salim : ECN support
35 *
36 */
37
38#define pr_fmt(fmt) "TCP: " fmt
39
40#include <net/tcp.h>
41#include <net/mptcp.h>
42
43#include <linux/compiler.h>
44#include <linux/gfp.h>
45#include <linux/module.h>
46#include <linux/static_key.h>
47
48#include <trace/events/tcp.h>
49
50/* Refresh clocks of a TCP socket,
51 * ensuring monotically increasing values.
52 */
53void tcp_mstamp_refresh(struct tcp_sock *tp)
54{
55 u64 val = tcp_clock_ns();
56
57 tp->tcp_clock_cache = val;
58 tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
59}
60
61static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
62 int push_one, gfp_t gfp);
63
64/* Account for new data that has been sent to the network. */
65static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
66{
67 struct inet_connection_sock *icsk = inet_csk(sk);
68 struct tcp_sock *tp = tcp_sk(sk);
69 unsigned int prior_packets = tp->packets_out;
70
71 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);
72
73 __skb_unlink(skb, &sk->sk_write_queue);
74 tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
75
76 if (tp->highest_sack == NULL)
77 tp->highest_sack = skb;
78
79 tp->packets_out += tcp_skb_pcount(skb);
80 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
81 tcp_rearm_rto(sk);
82
83 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
84 tcp_skb_pcount(skb));
85}
86
87/* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
88 * window scaling factor due to loss of precision.
89 * If window has been shrunk, what should we make? It is not clear at all.
90 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
91 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
92 * invalid. OK, let's make this for now:
93 */
94static inline __u32 tcp_acceptable_seq(const struct sock *sk)
95{
96 const struct tcp_sock *tp = tcp_sk(sk);
97
98 if (!before(tcp_wnd_end(tp), tp->snd_nxt) ||
99 (tp->rx_opt.wscale_ok &&
100 ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale))))
101 return tp->snd_nxt;
102 else
103 return tcp_wnd_end(tp);
104}
105
106/* Calculate mss to advertise in SYN segment.
107 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
108 *
109 * 1. It is independent of path mtu.
110 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
111 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
112 * attached devices, because some buggy hosts are confused by
113 * large MSS.
114 * 4. We do not make 3, we advertise MSS, calculated from first
115 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
116 * This may be overridden via information stored in routing table.
117 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
118 * probably even Jumbo".
119 */
120static __u16 tcp_advertise_mss(struct sock *sk)
121{
122 struct tcp_sock *tp = tcp_sk(sk);
123 const struct dst_entry *dst = __sk_dst_get(sk);
124 int mss = tp->advmss;
125
126 if (dst) {
127 unsigned int metric = dst_metric_advmss(dst);
128
129 if (metric < mss) {
130 mss = metric;
131 tp->advmss = mss;
132 }
133 }
134
135 return (__u16)mss;
136}
137
138/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
139 * This is the first part of cwnd validation mechanism.
140 */
141void tcp_cwnd_restart(struct sock *sk, s32 delta)
142{
143 struct tcp_sock *tp = tcp_sk(sk);
144 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
145 u32 cwnd = tp->snd_cwnd;
146
147 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
148
149 tp->snd_ssthresh = tcp_current_ssthresh(sk);
150 restart_cwnd = min(restart_cwnd, cwnd);
151
152 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
153 cwnd >>= 1;
154 tp->snd_cwnd = max(cwnd, restart_cwnd);
155 tp->snd_cwnd_stamp = tcp_jiffies32;
156 tp->snd_cwnd_used = 0;
157}
158
159/* Congestion state accounting after a packet has been sent. */
160static void tcp_event_data_sent(struct tcp_sock *tp,
161 struct sock *sk)
162{
163 struct inet_connection_sock *icsk = inet_csk(sk);
164 const u32 now = tcp_jiffies32;
165
166 if (tcp_packets_in_flight(tp) == 0)
167 tcp_ca_event(sk, CA_EVENT_TX_START);
168
169 /* If this is the first data packet sent in response to the
170 * previous received data,
171 * and it is a reply for ato after last received packet,
172 * increase pingpong count.
173 */
174 if (before(tp->lsndtime, icsk->icsk_ack.lrcvtime) &&
175 (u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
176 inet_csk_inc_pingpong_cnt(sk);
177
178 tp->lsndtime = now;
179}
180
181/* Account for an ACK we sent. */
182static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts,
183 u32 rcv_nxt)
184{
185 struct tcp_sock *tp = tcp_sk(sk);
186
187 if (unlikely(tp->compressed_ack)) {
188 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
189 tp->compressed_ack);
190 tp->compressed_ack = 0;
191 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
192 __sock_put(sk);
193 }
194
195 if (unlikely(rcv_nxt != tp->rcv_nxt))
196 return; /* Special ACK sent by DCTCP to reflect ECN */
197 tcp_dec_quickack_mode(sk, pkts);
198 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
199}
200
201/* Determine a window scaling and initial window to offer.
202 * Based on the assumption that the given amount of space
203 * will be offered. Store the results in the tp structure.
204 * NOTE: for smooth operation initial space offering should
205 * be a multiple of mss if possible. We assume here that mss >= 1.
206 * This MUST be enforced by all callers.
207 */
208void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,
209 __u32 *rcv_wnd, __u32 *window_clamp,
210 int wscale_ok, __u8 *rcv_wscale,
211 __u32 init_rcv_wnd)
212{
213 unsigned int space = (__space < 0 ? 0 : __space);
214
215 /* If no clamp set the clamp to the max possible scaled window */
216 if (*window_clamp == 0)
217 (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);
218 space = min(*window_clamp, space);
219
220 /* Quantize space offering to a multiple of mss if possible. */
221 if (space > mss)
222 space = rounddown(space, mss);
223
224 /* NOTE: offering an initial window larger than 32767
225 * will break some buggy TCP stacks. If the admin tells us
226 * it is likely we could be speaking with such a buggy stack
227 * we will truncate our initial window offering to 32K-1
228 * unless the remote has sent us a window scaling option,
229 * which we interpret as a sign the remote TCP is not
230 * misinterpreting the window field as a signed quantity.
231 */
232 if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
233 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
234 else
235 (*rcv_wnd) = min_t(u32, space, U16_MAX);
236
237 if (init_rcv_wnd)
238 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
239
240 *rcv_wscale = 0;
241 if (wscale_ok) {
242 /* Set window scaling on max possible window */
243 space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
244 space = max_t(u32, space, sysctl_rmem_max);
245 space = min_t(u32, space, *window_clamp);
246 *rcv_wscale = clamp_t(int, ilog2(space) - 15,
247 0, TCP_MAX_WSCALE);
248 }
249 /* Set the clamp no higher than max representable value */
250 (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);
251}
252EXPORT_SYMBOL(tcp_select_initial_window);
253
254/* Chose a new window to advertise, update state in tcp_sock for the
255 * socket, and return result with RFC1323 scaling applied. The return
256 * value can be stuffed directly into th->window for an outgoing
257 * frame.
258 */
259static u16 tcp_select_window(struct sock *sk)
260{
261 struct tcp_sock *tp = tcp_sk(sk);
262 u32 old_win = tp->rcv_wnd;
263 u32 cur_win = tcp_receive_window(tp);
264 u32 new_win = __tcp_select_window(sk);
265
266 /* Never shrink the offered window */
267 if (new_win < cur_win) {
268 /* Danger Will Robinson!
269 * Don't update rcv_wup/rcv_wnd here or else
270 * we will not be able to advertise a zero
271 * window in time. --DaveM
272 *
273 * Relax Will Robinson.
274 */
275 if (new_win == 0)
276 NET_INC_STATS(sock_net(sk),
277 LINUX_MIB_TCPWANTZEROWINDOWADV);
278 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
279 }
280 tp->rcv_wnd = new_win;
281 tp->rcv_wup = tp->rcv_nxt;
282
283 /* Make sure we do not exceed the maximum possible
284 * scaled window.
285 */
286 if (!tp->rx_opt.rcv_wscale &&
287 sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows)
288 new_win = min(new_win, MAX_TCP_WINDOW);
289 else
290 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
291
292 /* RFC1323 scaling applied */
293 new_win >>= tp->rx_opt.rcv_wscale;
294
295 /* If we advertise zero window, disable fast path. */
296 if (new_win == 0) {
297 tp->pred_flags = 0;
298 if (old_win)
299 NET_INC_STATS(sock_net(sk),
300 LINUX_MIB_TCPTOZEROWINDOWADV);
301 } else if (old_win == 0) {
302 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
303 }
304
305 return new_win;
306}
307
308/* Packet ECN state for a SYN-ACK */
309static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
310{
311 const struct tcp_sock *tp = tcp_sk(sk);
312
313 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
314 if (!(tp->ecn_flags & TCP_ECN_OK))
315 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
316 else if (tcp_ca_needs_ecn(sk) ||
317 tcp_bpf_ca_needs_ecn(sk))
318 INET_ECN_xmit(sk);
319}
320
321/* Packet ECN state for a SYN. */
322static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
323{
324 struct tcp_sock *tp = tcp_sk(sk);
325 bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
326 bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
327 tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
328
329 if (!use_ecn) {
330 const struct dst_entry *dst = __sk_dst_get(sk);
331
332 if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
333 use_ecn = true;
334 }
335
336 tp->ecn_flags = 0;
337
338 if (use_ecn) {
339 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
340 tp->ecn_flags = TCP_ECN_OK;
341 if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
342 INET_ECN_xmit(sk);
343 }
344}
345
346static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
347{
348 if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
349 /* tp->ecn_flags are cleared at a later point in time when
350 * SYN ACK is ultimatively being received.
351 */
352 TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
353}
354
355static void
356tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
357{
358 if (inet_rsk(req)->ecn_ok)
359 th->ece = 1;
360}
361
362/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
363 * be sent.
364 */
365static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
366 struct tcphdr *th, int tcp_header_len)
367{
368 struct tcp_sock *tp = tcp_sk(sk);
369
370 if (tp->ecn_flags & TCP_ECN_OK) {
371 /* Not-retransmitted data segment: set ECT and inject CWR. */
372 if (skb->len != tcp_header_len &&
373 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
374 INET_ECN_xmit(sk);
375 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
376 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
377 th->cwr = 1;
378 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
379 }
380 } else if (!tcp_ca_needs_ecn(sk)) {
381 /* ACK or retransmitted segment: clear ECT|CE */
382 INET_ECN_dontxmit(sk);
383 }
384 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
385 th->ece = 1;
386 }
387}
388
389/* Constructs common control bits of non-data skb. If SYN/FIN is present,
390 * auto increment end seqno.
391 */
392static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
393{
394 skb->ip_summed = CHECKSUM_PARTIAL;
395
396 TCP_SKB_CB(skb)->tcp_flags = flags;
397 TCP_SKB_CB(skb)->sacked = 0;
398
399 tcp_skb_pcount_set(skb, 1);
400
401 TCP_SKB_CB(skb)->seq = seq;
402 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
403 seq++;
404 TCP_SKB_CB(skb)->end_seq = seq;
405}
406
407static inline bool tcp_urg_mode(const struct tcp_sock *tp)
408{
409 return tp->snd_una != tp->snd_up;
410}
411
412#define OPTION_SACK_ADVERTISE (1 << 0)
413#define OPTION_TS (1 << 1)
414#define OPTION_MD5 (1 << 2)
415#define OPTION_WSCALE (1 << 3)
416#define OPTION_FAST_OPEN_COOKIE (1 << 8)
417#define OPTION_SMC (1 << 9)
418#define OPTION_MPTCP (1 << 10)
419
420static void smc_options_write(__be32 *ptr, u16 *options)
421{
422#if IS_ENABLED(CONFIG_SMC)
423 if (static_branch_unlikely(&tcp_have_smc)) {
424 if (unlikely(OPTION_SMC & *options)) {
425 *ptr++ = htonl((TCPOPT_NOP << 24) |
426 (TCPOPT_NOP << 16) |
427 (TCPOPT_EXP << 8) |
428 (TCPOLEN_EXP_SMC_BASE));
429 *ptr++ = htonl(TCPOPT_SMC_MAGIC);
430 }
431 }
432#endif
433}
434
435struct tcp_out_options {
436 u16 options; /* bit field of OPTION_* */
437 u16 mss; /* 0 to disable */
438 u8 ws; /* window scale, 0 to disable */
439 u8 num_sack_blocks; /* number of SACK blocks to include */
440 u8 hash_size; /* bytes in hash_location */
441 __u8 *hash_location; /* temporary pointer, overloaded */
442 __u32 tsval, tsecr; /* need to include OPTION_TS */
443 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
444 struct mptcp_out_options mptcp;
445};
446
447static void mptcp_options_write(__be32 *ptr, struct tcp_out_options *opts)
448{
449#if IS_ENABLED(CONFIG_MPTCP)
450 if (unlikely(OPTION_MPTCP & opts->options))
451 mptcp_write_options(ptr, &opts->mptcp);
452#endif
453}
454
455/* Write previously computed TCP options to the packet.
456 *
457 * Beware: Something in the Internet is very sensitive to the ordering of
458 * TCP options, we learned this through the hard way, so be careful here.
459 * Luckily we can at least blame others for their non-compliance but from
460 * inter-operability perspective it seems that we're somewhat stuck with
461 * the ordering which we have been using if we want to keep working with
462 * those broken things (not that it currently hurts anybody as there isn't
463 * particular reason why the ordering would need to be changed).
464 *
465 * At least SACK_PERM as the first option is known to lead to a disaster
466 * (but it may well be that other scenarios fail similarly).
467 */
468static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
469 struct tcp_out_options *opts)
470{
471 u16 options = opts->options; /* mungable copy */
472
473 if (unlikely(OPTION_MD5 & options)) {
474 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
475 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
476 /* overload cookie hash location */
477 opts->hash_location = (__u8 *)ptr;
478 ptr += 4;
479 }
480
481 if (unlikely(opts->mss)) {
482 *ptr++ = htonl((TCPOPT_MSS << 24) |
483 (TCPOLEN_MSS << 16) |
484 opts->mss);
485 }
486
487 if (likely(OPTION_TS & options)) {
488 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
489 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
490 (TCPOLEN_SACK_PERM << 16) |
491 (TCPOPT_TIMESTAMP << 8) |
492 TCPOLEN_TIMESTAMP);
493 options &= ~OPTION_SACK_ADVERTISE;
494 } else {
495 *ptr++ = htonl((TCPOPT_NOP << 24) |
496 (TCPOPT_NOP << 16) |
497 (TCPOPT_TIMESTAMP << 8) |
498 TCPOLEN_TIMESTAMP);
499 }
500 *ptr++ = htonl(opts->tsval);
501 *ptr++ = htonl(opts->tsecr);
502 }
503
504 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
505 *ptr++ = htonl((TCPOPT_NOP << 24) |
506 (TCPOPT_NOP << 16) |
507 (TCPOPT_SACK_PERM << 8) |
508 TCPOLEN_SACK_PERM);
509 }
510
511 if (unlikely(OPTION_WSCALE & options)) {
512 *ptr++ = htonl((TCPOPT_NOP << 24) |
513 (TCPOPT_WINDOW << 16) |
514 (TCPOLEN_WINDOW << 8) |
515 opts->ws);
516 }
517
518 if (unlikely(opts->num_sack_blocks)) {
519 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
520 tp->duplicate_sack : tp->selective_acks;
521 int this_sack;
522
523 *ptr++ = htonl((TCPOPT_NOP << 24) |
524 (TCPOPT_NOP << 16) |
525 (TCPOPT_SACK << 8) |
526 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
527 TCPOLEN_SACK_PERBLOCK)));
528
529 for (this_sack = 0; this_sack < opts->num_sack_blocks;
530 ++this_sack) {
531 *ptr++ = htonl(sp[this_sack].start_seq);
532 *ptr++ = htonl(sp[this_sack].end_seq);
533 }
534
535 tp->rx_opt.dsack = 0;
536 }
537
538 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
539 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
540 u8 *p = (u8 *)ptr;
541 u32 len; /* Fast Open option length */
542
543 if (foc->exp) {
544 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
545 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
546 TCPOPT_FASTOPEN_MAGIC);
547 p += TCPOLEN_EXP_FASTOPEN_BASE;
548 } else {
549 len = TCPOLEN_FASTOPEN_BASE + foc->len;
550 *p++ = TCPOPT_FASTOPEN;
551 *p++ = len;
552 }
553
554 memcpy(p, foc->val, foc->len);
555 if ((len & 3) == 2) {
556 p[foc->len] = TCPOPT_NOP;
557 p[foc->len + 1] = TCPOPT_NOP;
558 }
559 ptr += (len + 3) >> 2;
560 }
561
562 smc_options_write(ptr, &options);
563
564 mptcp_options_write(ptr, opts);
565}
566
567static void smc_set_option(const struct tcp_sock *tp,
568 struct tcp_out_options *opts,
569 unsigned int *remaining)
570{
571#if IS_ENABLED(CONFIG_SMC)
572 if (static_branch_unlikely(&tcp_have_smc)) {
573 if (tp->syn_smc) {
574 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
575 opts->options |= OPTION_SMC;
576 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
577 }
578 }
579 }
580#endif
581}
582
583static void smc_set_option_cond(const struct tcp_sock *tp,
584 const struct inet_request_sock *ireq,
585 struct tcp_out_options *opts,
586 unsigned int *remaining)
587{
588#if IS_ENABLED(CONFIG_SMC)
589 if (static_branch_unlikely(&tcp_have_smc)) {
590 if (tp->syn_smc && ireq->smc_ok) {
591 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) {
592 opts->options |= OPTION_SMC;
593 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED;
594 }
595 }
596 }
597#endif
598}
599
600static void mptcp_set_option_cond(const struct request_sock *req,
601 struct tcp_out_options *opts,
602 unsigned int *remaining)
603{
604 if (rsk_is_mptcp(req)) {
605 unsigned int size;
606
607 if (mptcp_synack_options(req, &size, &opts->mptcp)) {
608 if (*remaining >= size) {
609 opts->options |= OPTION_MPTCP;
610 *remaining -= size;
611 }
612 }
613 }
614}
615
616/* Compute TCP options for SYN packets. This is not the final
617 * network wire format yet.
618 */
619static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
620 struct tcp_out_options *opts,
621 struct tcp_md5sig_key **md5)
622{
623 struct tcp_sock *tp = tcp_sk(sk);
624 unsigned int remaining = MAX_TCP_OPTION_SPACE;
625 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
626
627 *md5 = NULL;
628#ifdef CONFIG_TCP_MD5SIG
629 if (static_branch_unlikely(&tcp_md5_needed) &&
630 rcu_access_pointer(tp->md5sig_info)) {
631 *md5 = tp->af_specific->md5_lookup(sk, sk);
632 if (*md5) {
633 opts->options |= OPTION_MD5;
634 remaining -= TCPOLEN_MD5SIG_ALIGNED;
635 }
636 }
637#endif
638
639 /* We always get an MSS option. The option bytes which will be seen in
640 * normal data packets should timestamps be used, must be in the MSS
641 * advertised. But we subtract them from tp->mss_cache so that
642 * calculations in tcp_sendmsg are simpler etc. So account for this
643 * fact here if necessary. If we don't do this correctly, as a
644 * receiver we won't recognize data packets as being full sized when we
645 * should, and thus we won't abide by the delayed ACK rules correctly.
646 * SACKs don't matter, we never delay an ACK when we have any of those
647 * going out. */
648 opts->mss = tcp_advertise_mss(sk);
649 remaining -= TCPOLEN_MSS_ALIGNED;
650
651 if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) {
652 opts->options |= OPTION_TS;
653 opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
654 opts->tsecr = tp->rx_opt.ts_recent;
655 remaining -= TCPOLEN_TSTAMP_ALIGNED;
656 }
657 if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) {
658 opts->ws = tp->rx_opt.rcv_wscale;
659 opts->options |= OPTION_WSCALE;
660 remaining -= TCPOLEN_WSCALE_ALIGNED;
661 }
662 if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) {
663 opts->options |= OPTION_SACK_ADVERTISE;
664 if (unlikely(!(OPTION_TS & opts->options)))
665 remaining -= TCPOLEN_SACKPERM_ALIGNED;
666 }
667
668 if (fastopen && fastopen->cookie.len >= 0) {
669 u32 need = fastopen->cookie.len;
670
671 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
672 TCPOLEN_FASTOPEN_BASE;
673 need = (need + 3) & ~3U; /* Align to 32 bits */
674 if (remaining >= need) {
675 opts->options |= OPTION_FAST_OPEN_COOKIE;
676 opts->fastopen_cookie = &fastopen->cookie;
677 remaining -= need;
678 tp->syn_fastopen = 1;
679 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
680 }
681 }
682
683 smc_set_option(tp, opts, &remaining);
684
685 if (sk_is_mptcp(sk)) {
686 unsigned int size;
687
688 if (mptcp_syn_options(sk, skb, &size, &opts->mptcp)) {
689 opts->options |= OPTION_MPTCP;
690 remaining -= size;
691 }
692 }
693
694 return MAX_TCP_OPTION_SPACE - remaining;
695}
696
697/* Set up TCP options for SYN-ACKs. */
698static unsigned int tcp_synack_options(const struct sock *sk,
699 struct request_sock *req,
700 unsigned int mss, struct sk_buff *skb,
701 struct tcp_out_options *opts,
702 const struct tcp_md5sig_key *md5,
703 struct tcp_fastopen_cookie *foc,
704 enum tcp_synack_type synack_type)
705{
706 struct inet_request_sock *ireq = inet_rsk(req);
707 unsigned int remaining = MAX_TCP_OPTION_SPACE;
708
709#ifdef CONFIG_TCP_MD5SIG
710 if (md5) {
711 opts->options |= OPTION_MD5;
712 remaining -= TCPOLEN_MD5SIG_ALIGNED;
713
714 /* We can't fit any SACK blocks in a packet with MD5 + TS
715 * options. There was discussion about disabling SACK
716 * rather than TS in order to fit in better with old,
717 * buggy kernels, but that was deemed to be unnecessary.
718 */
719 if (synack_type != TCP_SYNACK_COOKIE)
720 ireq->tstamp_ok &= !ireq->sack_ok;
721 }
722#endif
723
724 /* We always send an MSS option. */
725 opts->mss = mss;
726 remaining -= TCPOLEN_MSS_ALIGNED;
727
728 if (likely(ireq->wscale_ok)) {
729 opts->ws = ireq->rcv_wscale;
730 opts->options |= OPTION_WSCALE;
731 remaining -= TCPOLEN_WSCALE_ALIGNED;
732 }
733 if (likely(ireq->tstamp_ok)) {
734 opts->options |= OPTION_TS;
735 opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
736 opts->tsecr = req->ts_recent;
737 remaining -= TCPOLEN_TSTAMP_ALIGNED;
738 }
739 if (likely(ireq->sack_ok)) {
740 opts->options |= OPTION_SACK_ADVERTISE;
741 if (unlikely(!ireq->tstamp_ok))
742 remaining -= TCPOLEN_SACKPERM_ALIGNED;
743 }
744 if (foc != NULL && foc->len >= 0) {
745 u32 need = foc->len;
746
747 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
748 TCPOLEN_FASTOPEN_BASE;
749 need = (need + 3) & ~3U; /* Align to 32 bits */
750 if (remaining >= need) {
751 opts->options |= OPTION_FAST_OPEN_COOKIE;
752 opts->fastopen_cookie = foc;
753 remaining -= need;
754 }
755 }
756
757 mptcp_set_option_cond(req, opts, &remaining);
758
759 smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining);
760
761 return MAX_TCP_OPTION_SPACE - remaining;
762}
763
764/* Compute TCP options for ESTABLISHED sockets. This is not the
765 * final wire format yet.
766 */
767static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
768 struct tcp_out_options *opts,
769 struct tcp_md5sig_key **md5)
770{
771 struct tcp_sock *tp = tcp_sk(sk);
772 unsigned int size = 0;
773 unsigned int eff_sacks;
774
775 opts->options = 0;
776
777 *md5 = NULL;
778#ifdef CONFIG_TCP_MD5SIG
779 if (static_branch_unlikely(&tcp_md5_needed) &&
780 rcu_access_pointer(tp->md5sig_info)) {
781 *md5 = tp->af_specific->md5_lookup(sk, sk);
782 if (*md5) {
783 opts->options |= OPTION_MD5;
784 size += TCPOLEN_MD5SIG_ALIGNED;
785 }
786 }
787#endif
788
789 if (likely(tp->rx_opt.tstamp_ok)) {
790 opts->options |= OPTION_TS;
791 opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
792 opts->tsecr = tp->rx_opt.ts_recent;
793 size += TCPOLEN_TSTAMP_ALIGNED;
794 }
795
796 /* MPTCP options have precedence over SACK for the limited TCP
797 * option space because a MPTCP connection would be forced to
798 * fall back to regular TCP if a required multipath option is
799 * missing. SACK still gets a chance to use whatever space is
800 * left.
801 */
802 if (sk_is_mptcp(sk)) {
803 unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
804 unsigned int opt_size = 0;
805
806 if (mptcp_established_options(sk, skb, &opt_size, remaining,
807 &opts->mptcp)) {
808 opts->options |= OPTION_MPTCP;
809 size += opt_size;
810 }
811 }
812
813 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
814 if (unlikely(eff_sacks)) {
815 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
816 if (unlikely(remaining < TCPOLEN_SACK_BASE_ALIGNED +
817 TCPOLEN_SACK_PERBLOCK))
818 return size;
819
820 opts->num_sack_blocks =
821 min_t(unsigned int, eff_sacks,
822 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
823 TCPOLEN_SACK_PERBLOCK);
824
825 size += TCPOLEN_SACK_BASE_ALIGNED +
826 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
827 }
828
829 return size;
830}
831
832
833/* TCP SMALL QUEUES (TSQ)
834 *
835 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
836 * to reduce RTT and bufferbloat.
837 * We do this using a special skb destructor (tcp_wfree).
838 *
839 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
840 * needs to be reallocated in a driver.
841 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
842 *
843 * Since transmit from skb destructor is forbidden, we use a tasklet
844 * to process all sockets that eventually need to send more skbs.
845 * We use one tasklet per cpu, with its own queue of sockets.
846 */
847struct tsq_tasklet {
848 struct tasklet_struct tasklet;
849 struct list_head head; /* queue of tcp sockets */
850};
851static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
852
853static void tcp_tsq_write(struct sock *sk)
854{
855 if ((1 << sk->sk_state) &
856 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
857 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) {
858 struct tcp_sock *tp = tcp_sk(sk);
859
860 if (tp->lost_out > tp->retrans_out &&
861 tp->snd_cwnd > tcp_packets_in_flight(tp)) {
862 tcp_mstamp_refresh(tp);
863 tcp_xmit_retransmit_queue(sk);
864 }
865
866 tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle,
867 0, GFP_ATOMIC);
868 }
869}
870
871static void tcp_tsq_handler(struct sock *sk)
872{
873 bh_lock_sock(sk);
874 if (!sock_owned_by_user(sk))
875 tcp_tsq_write(sk);
876 else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
877 sock_hold(sk);
878 bh_unlock_sock(sk);
879}
880/*
881 * One tasklet per cpu tries to send more skbs.
882 * We run in tasklet context but need to disable irqs when
883 * transferring tsq->head because tcp_wfree() might
884 * interrupt us (non NAPI drivers)
885 */
886static void tcp_tasklet_func(unsigned long data)
887{
888 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
889 LIST_HEAD(list);
890 unsigned long flags;
891 struct list_head *q, *n;
892 struct tcp_sock *tp;
893 struct sock *sk;
894
895 local_irq_save(flags);
896 list_splice_init(&tsq->head, &list);
897 local_irq_restore(flags);
898
899 list_for_each_safe(q, n, &list) {
900 tp = list_entry(q, struct tcp_sock, tsq_node);
901 list_del(&tp->tsq_node);
902
903 sk = (struct sock *)tp;
904 smp_mb__before_atomic();
905 clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
906
907 tcp_tsq_handler(sk);
908 sk_free(sk);
909 }
910}
911
912#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
913 TCPF_WRITE_TIMER_DEFERRED | \
914 TCPF_DELACK_TIMER_DEFERRED | \
915 TCPF_MTU_REDUCED_DEFERRED)
916/**
917 * tcp_release_cb - tcp release_sock() callback
918 * @sk: socket
919 *
920 * called from release_sock() to perform protocol dependent
921 * actions before socket release.
922 */
923void tcp_release_cb(struct sock *sk)
924{
925 unsigned long flags, nflags;
926
927 /* perform an atomic operation only if at least one flag is set */
928 do {
929 flags = sk->sk_tsq_flags;
930 if (!(flags & TCP_DEFERRED_ALL))
931 return;
932 nflags = flags & ~TCP_DEFERRED_ALL;
933 } while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags);
934
935 if (flags & TCPF_TSQ_DEFERRED) {
936 tcp_tsq_write(sk);
937 __sock_put(sk);
938 }
939 /* Here begins the tricky part :
940 * We are called from release_sock() with :
941 * 1) BH disabled
942 * 2) sk_lock.slock spinlock held
943 * 3) socket owned by us (sk->sk_lock.owned == 1)
944 *
945 * But following code is meant to be called from BH handlers,
946 * so we should keep BH disabled, but early release socket ownership
947 */
948 sock_release_ownership(sk);
949
950 if (flags & TCPF_WRITE_TIMER_DEFERRED) {
951 tcp_write_timer_handler(sk);
952 __sock_put(sk);
953 }
954 if (flags & TCPF_DELACK_TIMER_DEFERRED) {
955 tcp_delack_timer_handler(sk);
956 __sock_put(sk);
957 }
958 if (flags & TCPF_MTU_REDUCED_DEFERRED) {
959 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
960 __sock_put(sk);
961 }
962}
963EXPORT_SYMBOL(tcp_release_cb);
964
965void __init tcp_tasklet_init(void)
966{
967 int i;
968
969 for_each_possible_cpu(i) {
970 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
971
972 INIT_LIST_HEAD(&tsq->head);
973 tasklet_init(&tsq->tasklet,
974 tcp_tasklet_func,
975 (unsigned long)tsq);
976 }
977}
978
979/*
980 * Write buffer destructor automatically called from kfree_skb.
981 * We can't xmit new skbs from this context, as we might already
982 * hold qdisc lock.
983 */
984void tcp_wfree(struct sk_buff *skb)
985{
986 struct sock *sk = skb->sk;
987 struct tcp_sock *tp = tcp_sk(sk);
988 unsigned long flags, nval, oval;
989
990 /* Keep one reference on sk_wmem_alloc.
991 * Will be released by sk_free() from here or tcp_tasklet_func()
992 */
993 WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc));
994
995 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
996 * Wait until our queues (qdisc + devices) are drained.
997 * This gives :
998 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
999 * - chance for incoming ACK (processed by another cpu maybe)
1000 * to migrate this flow (skb->ooo_okay will be eventually set)
1001 */
1002 if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
1003 goto out;
1004
1005 for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
1006 struct tsq_tasklet *tsq;
1007 bool empty;
1008
1009 if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
1010 goto out;
1011
1012 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
1013 nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
1014 if (nval != oval)
1015 continue;
1016
1017 /* queue this socket to tasklet queue */
1018 local_irq_save(flags);
1019 tsq = this_cpu_ptr(&tsq_tasklet);
1020 empty = list_empty(&tsq->head);
1021 list_add(&tp->tsq_node, &tsq->head);
1022 if (empty)
1023 tasklet_schedule(&tsq->tasklet);
1024 local_irq_restore(flags);
1025 return;
1026 }
1027out:
1028 sk_free(sk);
1029}
1030
1031/* Note: Called under soft irq.
1032 * We can call TCP stack right away, unless socket is owned by user.
1033 */
1034enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer)
1035{
1036 struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer);
1037 struct sock *sk = (struct sock *)tp;
1038
1039 tcp_tsq_handler(sk);
1040 sock_put(sk);
1041
1042 return HRTIMER_NORESTART;
1043}
1044
1045static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb,
1046 u64 prior_wstamp)
1047{
1048 struct tcp_sock *tp = tcp_sk(sk);
1049
1050 if (sk->sk_pacing_status != SK_PACING_NONE) {
1051 unsigned long rate = sk->sk_pacing_rate;
1052
1053 /* Original sch_fq does not pace first 10 MSS
1054 * Note that tp->data_segs_out overflows after 2^32 packets,
1055 * this is a minor annoyance.
1056 */
1057 if (rate != ~0UL && rate && tp->data_segs_out >= 10) {
1058 u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate);
1059 u64 credit = tp->tcp_wstamp_ns - prior_wstamp;
1060
1061 /* take into account OS jitter */
1062 len_ns -= min_t(u64, len_ns / 2, credit);
1063 tp->tcp_wstamp_ns += len_ns;
1064 }
1065 }
1066 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
1067}
1068
1069INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1070INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
1071INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb));
1072
1073/* This routine actually transmits TCP packets queued in by
1074 * tcp_do_sendmsg(). This is used by both the initial
1075 * transmission and possible later retransmissions.
1076 * All SKB's seen here are completely headerless. It is our
1077 * job to build the TCP header, and pass the packet down to
1078 * IP so it can do the same plus pass the packet off to the
1079 * device.
1080 *
1081 * We are working here with either a clone of the original
1082 * SKB, or a fresh unique copy made by the retransmit engine.
1083 */
1084static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
1085 int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
1086{
1087 const struct inet_connection_sock *icsk = inet_csk(sk);
1088 struct inet_sock *inet;
1089 struct tcp_sock *tp;
1090 struct tcp_skb_cb *tcb;
1091 struct tcp_out_options opts;
1092 unsigned int tcp_options_size, tcp_header_size;
1093 struct sk_buff *oskb = NULL;
1094 struct tcp_md5sig_key *md5;
1095 struct tcphdr *th;
1096 u64 prior_wstamp;
1097 int err;
1098
1099 BUG_ON(!skb || !tcp_skb_pcount(skb));
1100 tp = tcp_sk(sk);
1101 prior_wstamp = tp->tcp_wstamp_ns;
1102 tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
1103 skb->skb_mstamp_ns = tp->tcp_wstamp_ns;
1104 if (clone_it) {
1105 TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
1106 - tp->snd_una;
1107 oskb = skb;
1108
1109 tcp_skb_tsorted_save(oskb) {
1110 if (unlikely(skb_cloned(oskb)))
1111 skb = pskb_copy(oskb, gfp_mask);
1112 else
1113 skb = skb_clone(oskb, gfp_mask);
1114 } tcp_skb_tsorted_restore(oskb);
1115
1116 if (unlikely(!skb))
1117 return -ENOBUFS;
1118 /* retransmit skbs might have a non zero value in skb->dev
1119 * because skb->dev is aliased with skb->rbnode.rb_left
1120 */
1121 skb->dev = NULL;
1122 }
1123
1124 inet = inet_sk(sk);
1125 tcb = TCP_SKB_CB(skb);
1126 memset(&opts, 0, sizeof(opts));
1127
1128 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
1129 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
1130 } else {
1131 tcp_options_size = tcp_established_options(sk, skb, &opts,
1132 &md5);
1133 /* Force a PSH flag on all (GSO) packets to expedite GRO flush
1134 * at receiver : This slightly improve GRO performance.
1135 * Note that we do not force the PSH flag for non GSO packets,
1136 * because they might be sent under high congestion events,
1137 * and in this case it is better to delay the delivery of 1-MSS
1138 * packets and thus the corresponding ACK packet that would
1139 * release the following packet.
1140 */
1141 if (tcp_skb_pcount(skb) > 1)
1142 tcb->tcp_flags |= TCPHDR_PSH;
1143 }
1144 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
1145
1146 /* if no packet is in qdisc/device queue, then allow XPS to select
1147 * another queue. We can be called from tcp_tsq_handler()
1148 * which holds one reference to sk.
1149 *
1150 * TODO: Ideally, in-flight pure ACK packets should not matter here.
1151 * One way to get this would be to set skb->truesize = 2 on them.
1152 */
1153 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
1154
1155 /* If we had to use memory reserve to allocate this skb,
1156 * this might cause drops if packet is looped back :
1157 * Other socket might not have SOCK_MEMALLOC.
1158 * Packets not looped back do not care about pfmemalloc.
1159 */
1160 skb->pfmemalloc = 0;
1161
1162 skb_push(skb, tcp_header_size);
1163 skb_reset_transport_header(skb);
1164
1165 skb_orphan(skb);
1166 skb->sk = sk;
1167 skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
1168 skb_set_hash_from_sk(skb, sk);
1169 refcount_add(skb->truesize, &sk->sk_wmem_alloc);
1170
1171 skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);
1172
1173 /* Build TCP header and checksum it. */
1174 th = (struct tcphdr *)skb->data;
1175 th->source = inet->inet_sport;
1176 th->dest = inet->inet_dport;
1177 th->seq = htonl(tcb->seq);
1178 th->ack_seq = htonl(rcv_nxt);
1179 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
1180 tcb->tcp_flags);
1181
1182 th->check = 0;
1183 th->urg_ptr = 0;
1184
1185 /* The urg_mode check is necessary during a below snd_una win probe */
1186 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
1187 if (before(tp->snd_up, tcb->seq + 0x10000)) {
1188 th->urg_ptr = htons(tp->snd_up - tcb->seq);
1189 th->urg = 1;
1190 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
1191 th->urg_ptr = htons(0xFFFF);
1192 th->urg = 1;
1193 }
1194 }
1195
1196 tcp_options_write((__be32 *)(th + 1), tp, &opts);
1197 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
1198 if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) {
1199 th->window = htons(tcp_select_window(sk));
1200 tcp_ecn_send(sk, skb, th, tcp_header_size);
1201 } else {
1202 /* RFC1323: The window in SYN & SYN/ACK segments
1203 * is never scaled.
1204 */
1205 th->window = htons(min(tp->rcv_wnd, 65535U));
1206 }
1207#ifdef CONFIG_TCP_MD5SIG
1208 /* Calculate the MD5 hash, as we have all we need now */
1209 if (md5) {
1210 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
1211 tp->af_specific->calc_md5_hash(opts.hash_location,
1212 md5, sk, skb);
1213 }
1214#endif
1215
1216 INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check,
1217 tcp_v6_send_check, tcp_v4_send_check,
1218 sk, skb);
1219
1220 if (likely(tcb->tcp_flags & TCPHDR_ACK))
1221 tcp_event_ack_sent(sk, tcp_skb_pcount(skb), rcv_nxt);
1222
1223 if (skb->len != tcp_header_size) {
1224 tcp_event_data_sent(tp, sk);
1225 tp->data_segs_out += tcp_skb_pcount(skb);
1226 tp->bytes_sent += skb->len - tcp_header_size;
1227 }
1228
1229 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1230 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1231 tcp_skb_pcount(skb));
1232
1233 tp->segs_out += tcp_skb_pcount(skb);
1234 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1235 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1236 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1237
1238 /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */
1239
1240 /* Cleanup our debris for IP stacks */
1241 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1242 sizeof(struct inet6_skb_parm)));
1243
1244 tcp_add_tx_delay(skb, tp);
1245
1246 err = INDIRECT_CALL_INET(icsk->icsk_af_ops->queue_xmit,
1247 inet6_csk_xmit, ip_queue_xmit,
1248 sk, skb, &inet->cork.fl);
1249
1250 if (unlikely(err > 0)) {
1251 tcp_enter_cwr(sk);
1252 err = net_xmit_eval(err);
1253 }
1254 if (!err && oskb) {
1255 tcp_update_skb_after_send(sk, oskb, prior_wstamp);
1256 tcp_rate_skb_sent(sk, oskb);
1257 }
1258 return err;
1259}
1260
1261static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
1262 gfp_t gfp_mask)
1263{
1264 return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask,
1265 tcp_sk(sk)->rcv_nxt);
1266}
1267
1268/* This routine just queues the buffer for sending.
1269 *
1270 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1271 * otherwise socket can stall.
1272 */
1273static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1274{
1275 struct tcp_sock *tp = tcp_sk(sk);
1276
1277 /* Advance write_seq and place onto the write_queue. */
1278 WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq);
1279 __skb_header_release(skb);
1280 tcp_add_write_queue_tail(sk, skb);
1281 sk_wmem_queued_add(sk, skb->truesize);
1282 sk_mem_charge(sk, skb->truesize);
1283}
1284
1285/* Initialize TSO segments for a packet. */
1286static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1287{
1288 if (skb->len <= mss_now) {
1289 /* Avoid the costly divide in the normal
1290 * non-TSO case.
1291 */
1292 tcp_skb_pcount_set(skb, 1);
1293 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1294 } else {
1295 tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1296 TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1297 }
1298}
1299
1300/* Pcount in the middle of the write queue got changed, we need to do various
1301 * tweaks to fix counters
1302 */
1303static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1304{
1305 struct tcp_sock *tp = tcp_sk(sk);
1306
1307 tp->packets_out -= decr;
1308
1309 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1310 tp->sacked_out -= decr;
1311 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1312 tp->retrans_out -= decr;
1313 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1314 tp->lost_out -= decr;
1315
1316 /* Reno case is special. Sigh... */
1317 if (tcp_is_reno(tp) && decr > 0)
1318 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1319
1320 if (tp->lost_skb_hint &&
1321 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1322 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
1323 tp->lost_cnt_hint -= decr;
1324
1325 tcp_verify_left_out(tp);
1326}
1327
1328static bool tcp_has_tx_tstamp(const struct sk_buff *skb)
1329{
1330 return TCP_SKB_CB(skb)->txstamp_ack ||
1331 (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP);
1332}
1333
1334static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1335{
1336 struct skb_shared_info *shinfo = skb_shinfo(skb);
1337
1338 if (unlikely(tcp_has_tx_tstamp(skb)) &&
1339 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1340 struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1341 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1342
1343 shinfo->tx_flags &= ~tsflags;
1344 shinfo2->tx_flags |= tsflags;
1345 swap(shinfo->tskey, shinfo2->tskey);
1346 TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack;
1347 TCP_SKB_CB(skb)->txstamp_ack = 0;
1348 }
1349}
1350
1351static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
1352{
1353 TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor;
1354 TCP_SKB_CB(skb)->eor = 0;
1355}
1356
1357/* Insert buff after skb on the write or rtx queue of sk. */
1358static void tcp_insert_write_queue_after(struct sk_buff *skb,
1359 struct sk_buff *buff,
1360 struct sock *sk,
1361 enum tcp_queue tcp_queue)
1362{
1363 if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
1364 __skb_queue_after(&sk->sk_write_queue, skb, buff);
1365 else
1366 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
1367}
1368
1369/* Function to create two new TCP segments. Shrinks the given segment
1370 * to the specified size and appends a new segment with the rest of the
1371 * packet to the list. This won't be called frequently, I hope.
1372 * Remember, these are still headerless SKBs at this point.
1373 */
1374int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
1375 struct sk_buff *skb, u32 len,
1376 unsigned int mss_now, gfp_t gfp)
1377{
1378 struct tcp_sock *tp = tcp_sk(sk);
1379 struct sk_buff *buff;
1380 int nsize, old_factor;
1381 long limit;
1382 int nlen;
1383 u8 flags;
1384
1385 if (WARN_ON(len > skb->len))
1386 return -EINVAL;
1387
1388 nsize = skb_headlen(skb) - len;
1389 if (nsize < 0)
1390 nsize = 0;
1391
1392 /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb.
1393 * We need some allowance to not penalize applications setting small
1394 * SO_SNDBUF values.
1395 * Also allow first and last skb in retransmit queue to be split.
1396 */
1397 limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_MAX_SIZE);
1398 if (unlikely((sk->sk_wmem_queued >> 1) > limit &&
1399 tcp_queue != TCP_FRAG_IN_WRITE_QUEUE &&
1400 skb != tcp_rtx_queue_head(sk) &&
1401 skb != tcp_rtx_queue_tail(sk))) {
1402 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG);
1403 return -ENOMEM;
1404 }
1405
1406 if (skb_unclone(skb, gfp))
1407 return -ENOMEM;
1408
1409 /* Get a new skb... force flag on. */
1410 buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1411 if (!buff)
1412 return -ENOMEM; /* We'll just try again later. */
1413 skb_copy_decrypted(buff, skb);
1414
1415 sk_wmem_queued_add(sk, buff->truesize);
1416 sk_mem_charge(sk, buff->truesize);
1417 nlen = skb->len - len - nsize;
1418 buff->truesize += nlen;
1419 skb->truesize -= nlen;
1420
1421 /* Correct the sequence numbers. */
1422 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1423 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1424 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1425
1426 /* PSH and FIN should only be set in the second packet. */
1427 flags = TCP_SKB_CB(skb)->tcp_flags;
1428 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1429 TCP_SKB_CB(buff)->tcp_flags = flags;
1430 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1431 tcp_skb_fragment_eor(skb, buff);
1432
1433 skb_split(skb, buff, len);
1434
1435 buff->ip_summed = CHECKSUM_PARTIAL;
1436
1437 buff->tstamp = skb->tstamp;
1438 tcp_fragment_tstamp(skb, buff);
1439
1440 old_factor = tcp_skb_pcount(skb);
1441
1442 /* Fix up tso_factor for both original and new SKB. */
1443 tcp_set_skb_tso_segs(skb, mss_now);
1444 tcp_set_skb_tso_segs(buff, mss_now);
1445
1446 /* Update delivered info for the new segment */
1447 TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx;
1448
1449 /* If this packet has been sent out already, we must
1450 * adjust the various packet counters.
1451 */
1452 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1453 int diff = old_factor - tcp_skb_pcount(skb) -
1454 tcp_skb_pcount(buff);
1455
1456 if (diff)
1457 tcp_adjust_pcount(sk, skb, diff);
1458 }
1459
1460 /* Link BUFF into the send queue. */
1461 __skb_header_release(buff);
1462 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
1463 if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE)
1464 list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
1465
1466 return 0;
1467}
1468
1469/* This is similar to __pskb_pull_tail(). The difference is that pulled
1470 * data is not copied, but immediately discarded.
1471 */
1472static int __pskb_trim_head(struct sk_buff *skb, int len)
1473{
1474 struct skb_shared_info *shinfo;
1475 int i, k, eat;
1476
1477 eat = min_t(int, len, skb_headlen(skb));
1478 if (eat) {
1479 __skb_pull(skb, eat);
1480 len -= eat;
1481 if (!len)
1482 return 0;
1483 }
1484 eat = len;
1485 k = 0;
1486 shinfo = skb_shinfo(skb);
1487 for (i = 0; i < shinfo->nr_frags; i++) {
1488 int size = skb_frag_size(&shinfo->frags[i]);
1489
1490 if (size <= eat) {
1491 skb_frag_unref(skb, i);
1492 eat -= size;
1493 } else {
1494 shinfo->frags[k] = shinfo->frags[i];
1495 if (eat) {
1496 skb_frag_off_add(&shinfo->frags[k], eat);
1497 skb_frag_size_sub(&shinfo->frags[k], eat);
1498 eat = 0;
1499 }
1500 k++;
1501 }
1502 }
1503 shinfo->nr_frags = k;
1504
1505 skb->data_len -= len;
1506 skb->len = skb->data_len;
1507 return len;
1508}
1509
1510/* Remove acked data from a packet in the transmit queue. */
1511int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1512{
1513 u32 delta_truesize;
1514
1515 if (skb_unclone(skb, GFP_ATOMIC))
1516 return -ENOMEM;
1517
1518 delta_truesize = __pskb_trim_head(skb, len);
1519
1520 TCP_SKB_CB(skb)->seq += len;
1521 skb->ip_summed = CHECKSUM_PARTIAL;
1522
1523 if (delta_truesize) {
1524 skb->truesize -= delta_truesize;
1525 sk_wmem_queued_add(sk, -delta_truesize);
1526 sk_mem_uncharge(sk, delta_truesize);
1527 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1528 }
1529
1530 /* Any change of skb->len requires recalculation of tso factor. */
1531 if (tcp_skb_pcount(skb) > 1)
1532 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1533
1534 return 0;
1535}
1536
1537/* Calculate MSS not accounting any TCP options. */
1538static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1539{
1540 const struct tcp_sock *tp = tcp_sk(sk);
1541 const struct inet_connection_sock *icsk = inet_csk(sk);
1542 int mss_now;
1543
1544 /* Calculate base mss without TCP options:
1545 It is MMS_S - sizeof(tcphdr) of rfc1122
1546 */
1547 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1548
1549 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1550 if (icsk->icsk_af_ops->net_frag_header_len) {
1551 const struct dst_entry *dst = __sk_dst_get(sk);
1552
1553 if (dst && dst_allfrag(dst))
1554 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1555 }
1556
1557 /* Clamp it (mss_clamp does not include tcp options) */
1558 if (mss_now > tp->rx_opt.mss_clamp)
1559 mss_now = tp->rx_opt.mss_clamp;
1560
1561 /* Now subtract optional transport overhead */
1562 mss_now -= icsk->icsk_ext_hdr_len;
1563
1564 /* Then reserve room for full set of TCP options and 8 bytes of data */
1565 mss_now = max(mss_now, sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss);
1566 return mss_now;
1567}
1568
1569/* Calculate MSS. Not accounting for SACKs here. */
1570int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1571{
1572 /* Subtract TCP options size, not including SACKs */
1573 return __tcp_mtu_to_mss(sk, pmtu) -
1574 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1575}
1576
1577/* Inverse of above */
1578int tcp_mss_to_mtu(struct sock *sk, int mss)
1579{
1580 const struct tcp_sock *tp = tcp_sk(sk);
1581 const struct inet_connection_sock *icsk = inet_csk(sk);
1582 int mtu;
1583
1584 mtu = mss +
1585 tp->tcp_header_len +
1586 icsk->icsk_ext_hdr_len +
1587 icsk->icsk_af_ops->net_header_len;
1588
1589 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1590 if (icsk->icsk_af_ops->net_frag_header_len) {
1591 const struct dst_entry *dst = __sk_dst_get(sk);
1592
1593 if (dst && dst_allfrag(dst))
1594 mtu += icsk->icsk_af_ops->net_frag_header_len;
1595 }
1596 return mtu;
1597}
1598EXPORT_SYMBOL(tcp_mss_to_mtu);
1599
1600/* MTU probing init per socket */
1601void tcp_mtup_init(struct sock *sk)
1602{
1603 struct tcp_sock *tp = tcp_sk(sk);
1604 struct inet_connection_sock *icsk = inet_csk(sk);
1605 struct net *net = sock_net(sk);
1606
1607 icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
1608 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1609 icsk->icsk_af_ops->net_header_len;
1610 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
1611 icsk->icsk_mtup.probe_size = 0;
1612 if (icsk->icsk_mtup.enabled)
1613 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
1614}
1615EXPORT_SYMBOL(tcp_mtup_init);
1616
1617/* This function synchronize snd mss to current pmtu/exthdr set.
1618
1619 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1620 for TCP options, but includes only bare TCP header.
1621
1622 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1623 It is minimum of user_mss and mss received with SYN.
1624 It also does not include TCP options.
1625
1626 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1627
1628 tp->mss_cache is current effective sending mss, including
1629 all tcp options except for SACKs. It is evaluated,
1630 taking into account current pmtu, but never exceeds
1631 tp->rx_opt.mss_clamp.
1632
1633 NOTE1. rfc1122 clearly states that advertised MSS
1634 DOES NOT include either tcp or ip options.
1635
1636 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1637 are READ ONLY outside this function. --ANK (980731)
1638 */
1639unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1640{
1641 struct tcp_sock *tp = tcp_sk(sk);
1642 struct inet_connection_sock *icsk = inet_csk(sk);
1643 int mss_now;
1644
1645 if (icsk->icsk_mtup.search_high > pmtu)
1646 icsk->icsk_mtup.search_high = pmtu;
1647
1648 mss_now = tcp_mtu_to_mss(sk, pmtu);
1649 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1650
1651 /* And store cached results */
1652 icsk->icsk_pmtu_cookie = pmtu;
1653 if (icsk->icsk_mtup.enabled)
1654 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1655 tp->mss_cache = mss_now;
1656
1657 return mss_now;
1658}
1659EXPORT_SYMBOL(tcp_sync_mss);
1660
1661/* Compute the current effective MSS, taking SACKs and IP options,
1662 * and even PMTU discovery events into account.
1663 */
1664unsigned int tcp_current_mss(struct sock *sk)
1665{
1666 const struct tcp_sock *tp = tcp_sk(sk);
1667 const struct dst_entry *dst = __sk_dst_get(sk);
1668 u32 mss_now;
1669 unsigned int header_len;
1670 struct tcp_out_options opts;
1671 struct tcp_md5sig_key *md5;
1672
1673 mss_now = tp->mss_cache;
1674
1675 if (dst) {
1676 u32 mtu = dst_mtu(dst);
1677 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1678 mss_now = tcp_sync_mss(sk, mtu);
1679 }
1680
1681 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1682 sizeof(struct tcphdr);
1683 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1684 * some common options. If this is an odd packet (because we have SACK
1685 * blocks etc) then our calculated header_len will be different, and
1686 * we have to adjust mss_now correspondingly */
1687 if (header_len != tp->tcp_header_len) {
1688 int delta = (int) header_len - tp->tcp_header_len;
1689 mss_now -= delta;
1690 }
1691
1692 return mss_now;
1693}
1694
1695/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1696 * As additional protections, we do not touch cwnd in retransmission phases,
1697 * and if application hit its sndbuf limit recently.
1698 */
1699static void tcp_cwnd_application_limited(struct sock *sk)
1700{
1701 struct tcp_sock *tp = tcp_sk(sk);
1702
1703 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
1704 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
1705 /* Limited by application or receiver window. */
1706 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
1707 u32 win_used = max(tp->snd_cwnd_used, init_win);
1708 if (win_used < tp->snd_cwnd) {
1709 tp->snd_ssthresh = tcp_current_ssthresh(sk);
1710 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
1711 }
1712 tp->snd_cwnd_used = 0;
1713 }
1714 tp->snd_cwnd_stamp = tcp_jiffies32;
1715}
1716
1717static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1718{
1719 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1720 struct tcp_sock *tp = tcp_sk(sk);
1721
1722 /* Track the maximum number of outstanding packets in each
1723 * window, and remember whether we were cwnd-limited then.
1724 */
1725 if (!before(tp->snd_una, tp->max_packets_seq) ||
1726 tp->packets_out > tp->max_packets_out) {
1727 tp->max_packets_out = tp->packets_out;
1728 tp->max_packets_seq = tp->snd_nxt;
1729 tp->is_cwnd_limited = is_cwnd_limited;
1730 }
1731
1732 if (tcp_is_cwnd_limited(sk)) {
1733 /* Network is feed fully. */
1734 tp->snd_cwnd_used = 0;
1735 tp->snd_cwnd_stamp = tcp_jiffies32;
1736 } else {
1737 /* Network starves. */
1738 if (tp->packets_out > tp->snd_cwnd_used)
1739 tp->snd_cwnd_used = tp->packets_out;
1740
1741 if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle &&
1742 (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
1743 !ca_ops->cong_control)
1744 tcp_cwnd_application_limited(sk);
1745
1746 /* The following conditions together indicate the starvation
1747 * is caused by insufficient sender buffer:
1748 * 1) just sent some data (see tcp_write_xmit)
1749 * 2) not cwnd limited (this else condition)
1750 * 3) no more data to send (tcp_write_queue_empty())
1751 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1752 */
1753 if (tcp_write_queue_empty(sk) && sk->sk_socket &&
1754 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
1755 (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
1756 tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
1757 }
1758}
1759
1760/* Minshall's variant of the Nagle send check. */
1761static bool tcp_minshall_check(const struct tcp_sock *tp)
1762{
1763 return after(tp->snd_sml, tp->snd_una) &&
1764 !after(tp->snd_sml, tp->snd_nxt);
1765}
1766
1767/* Update snd_sml if this skb is under mss
1768 * Note that a TSO packet might end with a sub-mss segment
1769 * The test is really :
1770 * if ((skb->len % mss) != 0)
1771 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1772 * But we can avoid doing the divide again given we already have
1773 * skb_pcount = skb->len / mss_now
1774 */
1775static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1776 const struct sk_buff *skb)
1777{
1778 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1779 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1780}
1781
1782/* Return false, if packet can be sent now without violation Nagle's rules:
1783 * 1. It is full sized. (provided by caller in %partial bool)
1784 * 2. Or it contains FIN. (already checked by caller)
1785 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1786 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1787 * With Minshall's modification: all sent small packets are ACKed.
1788 */
1789static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1790 int nonagle)
1791{
1792 return partial &&
1793 ((nonagle & TCP_NAGLE_CORK) ||
1794 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1795}
1796
1797/* Return how many segs we'd like on a TSO packet,
1798 * to send one TSO packet per ms
1799 */
1800static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
1801 int min_tso_segs)
1802{
1803 u32 bytes, segs;
1804
1805 bytes = min_t(unsigned long,
1806 sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift),
1807 sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);
1808
1809 /* Goal is to send at least one packet per ms,
1810 * not one big TSO packet every 100 ms.
1811 * This preserves ACK clocking and is consistent
1812 * with tcp_tso_should_defer() heuristic.
1813 */
1814 segs = max_t(u32, bytes / mss_now, min_tso_segs);
1815
1816 return segs;
1817}
1818
1819/* Return the number of segments we want in the skb we are transmitting.
1820 * See if congestion control module wants to decide; otherwise, autosize.
1821 */
1822static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
1823{
1824 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1825 u32 min_tso, tso_segs;
1826
1827 min_tso = ca_ops->min_tso_segs ?
1828 ca_ops->min_tso_segs(sk) :
1829 sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
1830
1831 tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
1832 return min_t(u32, tso_segs, sk->sk_gso_max_segs);
1833}
1834
1835/* Returns the portion of skb which can be sent right away */
1836static unsigned int tcp_mss_split_point(const struct sock *sk,
1837 const struct sk_buff *skb,
1838 unsigned int mss_now,
1839 unsigned int max_segs,
1840 int nonagle)
1841{
1842 const struct tcp_sock *tp = tcp_sk(sk);
1843 u32 partial, needed, window, max_len;
1844
1845 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1846 max_len = mss_now * max_segs;
1847
1848 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1849 return max_len;
1850
1851 needed = min(skb->len, window);
1852
1853 if (max_len <= needed)
1854 return max_len;
1855
1856 partial = needed % mss_now;
1857 /* If last segment is not a full MSS, check if Nagle rules allow us
1858 * to include this last segment in this skb.
1859 * Otherwise, we'll split the skb at last MSS boundary
1860 */
1861 if (tcp_nagle_check(partial != 0, tp, nonagle))
1862 return needed - partial;
1863
1864 return needed;
1865}
1866
1867/* Can at least one segment of SKB be sent right now, according to the
1868 * congestion window rules? If so, return how many segments are allowed.
1869 */
1870static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1871 const struct sk_buff *skb)
1872{
1873 u32 in_flight, cwnd, halfcwnd;
1874
1875 /* Don't be strict about the congestion window for the final FIN. */
1876 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1877 tcp_skb_pcount(skb) == 1)
1878 return 1;
1879
1880 in_flight = tcp_packets_in_flight(tp);
1881 cwnd = tp->snd_cwnd;
1882 if (in_flight >= cwnd)
1883 return 0;
1884
1885 /* For better scheduling, ensure we have at least
1886 * 2 GSO packets in flight.
1887 */
1888 halfcwnd = max(cwnd >> 1, 1U);
1889 return min(halfcwnd, cwnd - in_flight);
1890}
1891
1892/* Initialize TSO state of a skb.
1893 * This must be invoked the first time we consider transmitting
1894 * SKB onto the wire.
1895 */
1896static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1897{
1898 int tso_segs = tcp_skb_pcount(skb);
1899
1900 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1901 tcp_set_skb_tso_segs(skb, mss_now);
1902 tso_segs = tcp_skb_pcount(skb);
1903 }
1904 return tso_segs;
1905}
1906
1907
1908/* Return true if the Nagle test allows this packet to be
1909 * sent now.
1910 */
1911static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1912 unsigned int cur_mss, int nonagle)
1913{
1914 /* Nagle rule does not apply to frames, which sit in the middle of the
1915 * write_queue (they have no chances to get new data).
1916 *
1917 * This is implemented in the callers, where they modify the 'nonagle'
1918 * argument based upon the location of SKB in the send queue.
1919 */
1920 if (nonagle & TCP_NAGLE_PUSH)
1921 return true;
1922
1923 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1924 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1925 return true;
1926
1927 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
1928 return true;
1929
1930 return false;
1931}
1932
1933/* Does at least the first segment of SKB fit into the send window? */
1934static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1935 const struct sk_buff *skb,
1936 unsigned int cur_mss)
1937{
1938 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1939
1940 if (skb->len > cur_mss)
1941 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1942
1943 return !after(end_seq, tcp_wnd_end(tp));
1944}
1945
1946/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1947 * which is put after SKB on the list. It is very much like
1948 * tcp_fragment() except that it may make several kinds of assumptions
1949 * in order to speed up the splitting operation. In particular, we
1950 * know that all the data is in scatter-gather pages, and that the
1951 * packet has never been sent out before (and thus is not cloned).
1952 */
1953static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1954 unsigned int mss_now, gfp_t gfp)
1955{
1956 int nlen = skb->len - len;
1957 struct sk_buff *buff;
1958 u8 flags;
1959
1960 /* All of a TSO frame must be composed of paged data. */
1961 if (skb->len != skb->data_len)
1962 return tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
1963 skb, len, mss_now, gfp);
1964
1965 buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1966 if (unlikely(!buff))
1967 return -ENOMEM;
1968 skb_copy_decrypted(buff, skb);
1969
1970 sk_wmem_queued_add(sk, buff->truesize);
1971 sk_mem_charge(sk, buff->truesize);
1972 buff->truesize += nlen;
1973 skb->truesize -= nlen;
1974
1975 /* Correct the sequence numbers. */
1976 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1977 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1978 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1979
1980 /* PSH and FIN should only be set in the second packet. */
1981 flags = TCP_SKB_CB(skb)->tcp_flags;
1982 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1983 TCP_SKB_CB(buff)->tcp_flags = flags;
1984
1985 /* This packet was never sent out yet, so no SACK bits. */
1986 TCP_SKB_CB(buff)->sacked = 0;
1987
1988 tcp_skb_fragment_eor(skb, buff);
1989
1990 buff->ip_summed = CHECKSUM_PARTIAL;
1991 skb_split(skb, buff, len);
1992 tcp_fragment_tstamp(skb, buff);
1993
1994 /* Fix up tso_factor for both original and new SKB. */
1995 tcp_set_skb_tso_segs(skb, mss_now);
1996 tcp_set_skb_tso_segs(buff, mss_now);
1997
1998 /* Link BUFF into the send queue. */
1999 __skb_header_release(buff);
2000 tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE);
2001
2002 return 0;
2003}
2004
2005/* Try to defer sending, if possible, in order to minimize the amount
2006 * of TSO splitting we do. View it as a kind of TSO Nagle test.
2007 *
2008 * This algorithm is from John Heffner.
2009 */
2010static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
2011 bool *is_cwnd_limited,
2012 bool *is_rwnd_limited,
2013 u32 max_segs)
2014{
2015 const struct inet_connection_sock *icsk = inet_csk(sk);
2016 u32 send_win, cong_win, limit, in_flight;
2017 struct tcp_sock *tp = tcp_sk(sk);
2018 struct sk_buff *head;
2019 int win_divisor;
2020 s64 delta;
2021
2022 if (icsk->icsk_ca_state >= TCP_CA_Recovery)
2023 goto send_now;
2024
2025 /* Avoid bursty behavior by allowing defer
2026 * only if the last write was recent (1 ms).
2027 * Note that tp->tcp_wstamp_ns can be in the future if we have
2028 * packets waiting in a qdisc or device for EDT delivery.
2029 */
2030 delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC;
2031 if (delta > 0)
2032 goto send_now;
2033
2034 in_flight = tcp_packets_in_flight(tp);
2035
2036 BUG_ON(tcp_skb_pcount(skb) <= 1);
2037 BUG_ON(tp->snd_cwnd <= in_flight);
2038
2039 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2040
2041 /* From in_flight test above, we know that cwnd > in_flight. */
2042 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
2043
2044 limit = min(send_win, cong_win);
2045
2046 /* If a full-sized TSO skb can be sent, do it. */
2047 if (limit >= max_segs * tp->mss_cache)
2048 goto send_now;
2049
2050 /* Middle in queue won't get any more data, full sendable already? */
2051 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
2052 goto send_now;
2053
2054 win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor);
2055 if (win_divisor) {
2056 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
2057
2058 /* If at least some fraction of a window is available,
2059 * just use it.
2060 */
2061 chunk /= win_divisor;
2062 if (limit >= chunk)
2063 goto send_now;
2064 } else {
2065 /* Different approach, try not to defer past a single
2066 * ACK. Receiver should ACK every other full sized
2067 * frame, so if we have space for more than 3 frames
2068 * then send now.
2069 */
2070 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
2071 goto send_now;
2072 }
2073
2074 /* TODO : use tsorted_sent_queue ? */
2075 head = tcp_rtx_queue_head(sk);
2076 if (!head)
2077 goto send_now;
2078 delta = tp->tcp_clock_cache - head->tstamp;
2079 /* If next ACK is likely to come too late (half srtt), do not defer */
2080 if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0)
2081 goto send_now;
2082
2083 /* Ok, it looks like it is advisable to defer.
2084 * Three cases are tracked :
2085 * 1) We are cwnd-limited
2086 * 2) We are rwnd-limited
2087 * 3) We are application limited.
2088 */
2089 if (cong_win < send_win) {
2090 if (cong_win <= skb->len) {
2091 *is_cwnd_limited = true;
2092 return true;
2093 }
2094 } else {
2095 if (send_win <= skb->len) {
2096 *is_rwnd_limited = true;
2097 return true;
2098 }
2099 }
2100
2101 /* If this packet won't get more data, do not wait. */
2102 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) ||
2103 TCP_SKB_CB(skb)->eor)
2104 goto send_now;
2105
2106 return true;
2107
2108send_now:
2109 return false;
2110}
2111
2112static inline void tcp_mtu_check_reprobe(struct sock *sk)
2113{
2114 struct inet_connection_sock *icsk = inet_csk(sk);
2115 struct tcp_sock *tp = tcp_sk(sk);
2116 struct net *net = sock_net(sk);
2117 u32 interval;
2118 s32 delta;
2119
2120 interval = net->ipv4.sysctl_tcp_probe_interval;
2121 delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp;
2122 if (unlikely(delta >= interval * HZ)) {
2123 int mss = tcp_current_mss(sk);
2124
2125 /* Update current search range */
2126 icsk->icsk_mtup.probe_size = 0;
2127 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
2128 sizeof(struct tcphdr) +
2129 icsk->icsk_af_ops->net_header_len;
2130 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
2131
2132 /* Update probe time stamp */
2133 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
2134 }
2135}
2136
2137static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len)
2138{
2139 struct sk_buff *skb, *next;
2140
2141 skb = tcp_send_head(sk);
2142 tcp_for_write_queue_from_safe(skb, next, sk) {
2143 if (len <= skb->len)
2144 break;
2145
2146 if (unlikely(TCP_SKB_CB(skb)->eor) || tcp_has_tx_tstamp(skb))
2147 return false;
2148
2149 len -= skb->len;
2150 }
2151
2152 return true;
2153}
2154
2155/* Create a new MTU probe if we are ready.
2156 * MTU probe is regularly attempting to increase the path MTU by
2157 * deliberately sending larger packets. This discovers routing
2158 * changes resulting in larger path MTUs.
2159 *
2160 * Returns 0 if we should wait to probe (no cwnd available),
2161 * 1 if a probe was sent,
2162 * -1 otherwise
2163 */
2164static int tcp_mtu_probe(struct sock *sk)
2165{
2166 struct inet_connection_sock *icsk = inet_csk(sk);
2167 struct tcp_sock *tp = tcp_sk(sk);
2168 struct sk_buff *skb, *nskb, *next;
2169 struct net *net = sock_net(sk);
2170 int probe_size;
2171 int size_needed;
2172 int copy, len;
2173 int mss_now;
2174 int interval;
2175
2176 /* Not currently probing/verifying,
2177 * not in recovery,
2178 * have enough cwnd, and
2179 * not SACKing (the variable headers throw things off)
2180 */
2181 if (likely(!icsk->icsk_mtup.enabled ||
2182 icsk->icsk_mtup.probe_size ||
2183 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
2184 tp->snd_cwnd < 11 ||
2185 tp->rx_opt.num_sacks || tp->rx_opt.dsack))
2186 return -1;
2187
2188 /* Use binary search for probe_size between tcp_mss_base,
2189 * and current mss_clamp. if (search_high - search_low)
2190 * smaller than a threshold, backoff from probing.
2191 */
2192 mss_now = tcp_current_mss(sk);
2193 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
2194 icsk->icsk_mtup.search_low) >> 1);
2195 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
2196 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
2197 /* When misfortune happens, we are reprobing actively,
2198 * and then reprobe timer has expired. We stick with current
2199 * probing process by not resetting search range to its orignal.
2200 */
2201 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
2202 interval < net->ipv4.sysctl_tcp_probe_threshold) {
2203 /* Check whether enough time has elaplased for
2204 * another round of probing.
2205 */
2206 tcp_mtu_check_reprobe(sk);
2207 return -1;
2208 }
2209
2210 /* Have enough data in the send queue to probe? */
2211 if (tp->write_seq - tp->snd_nxt < size_needed)
2212 return -1;
2213
2214 if (tp->snd_wnd < size_needed)
2215 return -1;
2216 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
2217 return 0;
2218
2219 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2220 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
2221 if (!tcp_packets_in_flight(tp))
2222 return -1;
2223 else
2224 return 0;
2225 }
2226
2227 if (!tcp_can_coalesce_send_queue_head(sk, probe_size))
2228 return -1;
2229
2230 /* We're allowed to probe. Build it now. */
2231 nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
2232 if (!nskb)
2233 return -1;
2234 sk_wmem_queued_add(sk, nskb->truesize);
2235 sk_mem_charge(sk, nskb->truesize);
2236
2237 skb = tcp_send_head(sk);
2238 skb_copy_decrypted(nskb, skb);
2239
2240 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
2241 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
2242 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
2243 TCP_SKB_CB(nskb)->sacked = 0;
2244 nskb->csum = 0;
2245 nskb->ip_summed = CHECKSUM_PARTIAL;
2246
2247 tcp_insert_write_queue_before(nskb, skb, sk);
2248 tcp_highest_sack_replace(sk, skb, nskb);
2249
2250 len = 0;
2251 tcp_for_write_queue_from_safe(skb, next, sk) {
2252 copy = min_t(int, skb->len, probe_size - len);
2253 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
2254
2255 if (skb->len <= copy) {
2256 /* We've eaten all the data from this skb.
2257 * Throw it away. */
2258 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
2259 /* If this is the last SKB we copy and eor is set
2260 * we need to propagate it to the new skb.
2261 */
2262 TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
2263 tcp_skb_collapse_tstamp(nskb, skb);
2264 tcp_unlink_write_queue(skb, sk);
2265 sk_wmem_free_skb(sk, skb);
2266 } else {
2267 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
2268 ~(TCPHDR_FIN|TCPHDR_PSH);
2269 if (!skb_shinfo(skb)->nr_frags) {
2270 skb_pull(skb, copy);
2271 } else {
2272 __pskb_trim_head(skb, copy);
2273 tcp_set_skb_tso_segs(skb, mss_now);
2274 }
2275 TCP_SKB_CB(skb)->seq += copy;
2276 }
2277
2278 len += copy;
2279
2280 if (len >= probe_size)
2281 break;
2282 }
2283 tcp_init_tso_segs(nskb, nskb->len);
2284
2285 /* We're ready to send. If this fails, the probe will
2286 * be resegmented into mss-sized pieces by tcp_write_xmit().
2287 */
2288 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
2289 /* Decrement cwnd here because we are sending
2290 * effectively two packets. */
2291 tp->snd_cwnd--;
2292 tcp_event_new_data_sent(sk, nskb);
2293
2294 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
2295 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
2296 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
2297
2298 return 1;
2299 }
2300
2301 return -1;
2302}
2303
2304static bool tcp_pacing_check(struct sock *sk)
2305{
2306 struct tcp_sock *tp = tcp_sk(sk);
2307
2308 if (!tcp_needs_internal_pacing(sk))
2309 return false;
2310
2311 if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache)
2312 return false;
2313
2314 if (!hrtimer_is_queued(&tp->pacing_timer)) {
2315 hrtimer_start(&tp->pacing_timer,
2316 ns_to_ktime(tp->tcp_wstamp_ns),
2317 HRTIMER_MODE_ABS_PINNED_SOFT);
2318 sock_hold(sk);
2319 }
2320 return true;
2321}
2322
2323/* TCP Small Queues :
2324 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2325 * (These limits are doubled for retransmits)
2326 * This allows for :
2327 * - better RTT estimation and ACK scheduling
2328 * - faster recovery
2329 * - high rates
2330 * Alas, some drivers / subsystems require a fair amount
2331 * of queued bytes to ensure line rate.
2332 * One example is wifi aggregation (802.11 AMPDU)
2333 */
2334static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
2335 unsigned int factor)
2336{
2337 unsigned long limit;
2338
2339 limit = max_t(unsigned long,
2340 2 * skb->truesize,
2341 sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift));
2342 if (sk->sk_pacing_status == SK_PACING_NONE)
2343 limit = min_t(unsigned long, limit,
2344 sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
2345 limit <<= factor;
2346
2347 if (static_branch_unlikely(&tcp_tx_delay_enabled) &&
2348 tcp_sk(sk)->tcp_tx_delay) {
2349 u64 extra_bytes = (u64)sk->sk_pacing_rate * tcp_sk(sk)->tcp_tx_delay;
2350
2351 /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we
2352 * approximate our needs assuming an ~100% skb->truesize overhead.
2353 * USEC_PER_SEC is approximated by 2^20.
2354 * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift.
2355 */
2356 extra_bytes >>= (20 - 1);
2357 limit += extra_bytes;
2358 }
2359 if (refcount_read(&sk->sk_wmem_alloc) > limit) {
2360 /* Always send skb if rtx queue is empty.
2361 * No need to wait for TX completion to call us back,
2362 * after softirq/tasklet schedule.
2363 * This helps when TX completions are delayed too much.
2364 */
2365 if (tcp_rtx_queue_empty(sk))
2366 return false;
2367
2368 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
2369 /* It is possible TX completion already happened
2370 * before we set TSQ_THROTTLED, so we must
2371 * test again the condition.
2372 */
2373 smp_mb__after_atomic();
2374 if (refcount_read(&sk->sk_wmem_alloc) > limit)
2375 return true;
2376 }
2377 return false;
2378}
2379
2380static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
2381{
2382 const u32 now = tcp_jiffies32;
2383 enum tcp_chrono old = tp->chrono_type;
2384
2385 if (old > TCP_CHRONO_UNSPEC)
2386 tp->chrono_stat[old - 1] += now - tp->chrono_start;
2387 tp->chrono_start = now;
2388 tp->chrono_type = new;
2389}
2390
2391void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
2392{
2393 struct tcp_sock *tp = tcp_sk(sk);
2394
2395 /* If there are multiple conditions worthy of tracking in a
2396 * chronograph then the highest priority enum takes precedence
2397 * over the other conditions. So that if something "more interesting"
2398 * starts happening, stop the previous chrono and start a new one.
2399 */
2400 if (type > tp->chrono_type)
2401 tcp_chrono_set(tp, type);
2402}
2403
2404void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
2405{
2406 struct tcp_sock *tp = tcp_sk(sk);
2407
2408
2409 /* There are multiple conditions worthy of tracking in a
2410 * chronograph, so that the highest priority enum takes
2411 * precedence over the other conditions (see tcp_chrono_start).
2412 * If a condition stops, we only stop chrono tracking if
2413 * it's the "most interesting" or current chrono we are
2414 * tracking and starts busy chrono if we have pending data.
2415 */
2416 if (tcp_rtx_and_write_queues_empty(sk))
2417 tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
2418 else if (type == tp->chrono_type)
2419 tcp_chrono_set(tp, TCP_CHRONO_BUSY);
2420}
2421
2422/* This routine writes packets to the network. It advances the
2423 * send_head. This happens as incoming acks open up the remote
2424 * window for us.
2425 *
2426 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2427 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2428 * account rare use of URG, this is not a big flaw.
2429 *
2430 * Send at most one packet when push_one > 0. Temporarily ignore
2431 * cwnd limit to force at most one packet out when push_one == 2.
2432
2433 * Returns true, if no segments are in flight and we have queued segments,
2434 * but cannot send anything now because of SWS or another problem.
2435 */
2436static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2437 int push_one, gfp_t gfp)
2438{
2439 struct tcp_sock *tp = tcp_sk(sk);
2440 struct sk_buff *skb;
2441 unsigned int tso_segs, sent_pkts;
2442 int cwnd_quota;
2443 int result;
2444 bool is_cwnd_limited = false, is_rwnd_limited = false;
2445 u32 max_segs;
2446
2447 sent_pkts = 0;
2448
2449 tcp_mstamp_refresh(tp);
2450 if (!push_one) {
2451 /* Do MTU probing. */
2452 result = tcp_mtu_probe(sk);
2453 if (!result) {
2454 return false;
2455 } else if (result > 0) {
2456 sent_pkts = 1;
2457 }
2458 }
2459
2460 max_segs = tcp_tso_segs(sk, mss_now);
2461 while ((skb = tcp_send_head(sk))) {
2462 unsigned int limit;
2463
2464 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2465 /* "skb_mstamp_ns" is used as a start point for the retransmit timer */
2466 skb->skb_mstamp_ns = tp->tcp_wstamp_ns = tp->tcp_clock_cache;
2467 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
2468 tcp_init_tso_segs(skb, mss_now);
2469 goto repair; /* Skip network transmission */
2470 }
2471
2472 if (tcp_pacing_check(sk))
2473 break;
2474
2475 tso_segs = tcp_init_tso_segs(skb, mss_now);
2476 BUG_ON(!tso_segs);
2477
2478 cwnd_quota = tcp_cwnd_test(tp, skb);
2479 if (!cwnd_quota) {
2480 if (push_one == 2)
2481 /* Force out a loss probe pkt. */
2482 cwnd_quota = 1;
2483 else
2484 break;
2485 }
2486
2487 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
2488 is_rwnd_limited = true;
2489 break;
2490 }
2491
2492 if (tso_segs == 1) {
2493 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2494 (tcp_skb_is_last(sk, skb) ?
2495 nonagle : TCP_NAGLE_PUSH))))
2496 break;
2497 } else {
2498 if (!push_one &&
2499 tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2500 &is_rwnd_limited, max_segs))
2501 break;
2502 }
2503
2504 limit = mss_now;
2505 if (tso_segs > 1 && !tcp_urg_mode(tp))
2506 limit = tcp_mss_split_point(sk, skb, mss_now,
2507 min_t(unsigned int,
2508 cwnd_quota,
2509 max_segs),
2510 nonagle);
2511
2512 if (skb->len > limit &&
2513 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
2514 break;
2515
2516 if (tcp_small_queue_check(sk, skb, 0))
2517 break;
2518
2519 /* Argh, we hit an empty skb(), presumably a thread
2520 * is sleeping in sendmsg()/sk_stream_wait_memory().
2521 * We do not want to send a pure-ack packet and have
2522 * a strange looking rtx queue with empty packet(s).
2523 */
2524 if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq)
2525 break;
2526
2527 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2528 break;
2529
2530repair:
2531 /* Advance the send_head. This one is sent out.
2532 * This call will increment packets_out.
2533 */
2534 tcp_event_new_data_sent(sk, skb);
2535
2536 tcp_minshall_update(tp, mss_now, skb);
2537 sent_pkts += tcp_skb_pcount(skb);
2538
2539 if (push_one)
2540 break;
2541 }
2542
2543 if (is_rwnd_limited)
2544 tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
2545 else
2546 tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
2547
2548 if (likely(sent_pkts)) {
2549 if (tcp_in_cwnd_reduction(sk))
2550 tp->prr_out += sent_pkts;
2551
2552 /* Send one loss probe per tail loss episode. */
2553 if (push_one != 2)
2554 tcp_schedule_loss_probe(sk, false);
2555 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2556 tcp_cwnd_validate(sk, is_cwnd_limited);
2557 return false;
2558 }
2559 return !tp->packets_out && !tcp_write_queue_empty(sk);
2560}
2561
2562bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
2563{
2564 struct inet_connection_sock *icsk = inet_csk(sk);
2565 struct tcp_sock *tp = tcp_sk(sk);
2566 u32 timeout, rto_delta_us;
2567 int early_retrans;
2568
2569 /* Don't do any loss probe on a Fast Open connection before 3WHS
2570 * finishes.
2571 */
2572 if (rcu_access_pointer(tp->fastopen_rsk))
2573 return false;
2574
2575 early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
2576 /* Schedule a loss probe in 2*RTT for SACK capable connections
2577 * not in loss recovery, that are either limited by cwnd or application.
2578 */
2579 if ((early_retrans != 3 && early_retrans != 4) ||
2580 !tp->packets_out || !tcp_is_sack(tp) ||
2581 (icsk->icsk_ca_state != TCP_CA_Open &&
2582 icsk->icsk_ca_state != TCP_CA_CWR))
2583 return false;
2584
2585 /* Probe timeout is 2*rtt. Add minimum RTO to account
2586 * for delayed ack when there's one outstanding packet. If no RTT
2587 * sample is available then probe after TCP_TIMEOUT_INIT.
2588 */
2589 if (tp->srtt_us) {
2590 timeout = usecs_to_jiffies(tp->srtt_us >> 2);
2591 if (tp->packets_out == 1)
2592 timeout += TCP_RTO_MIN;
2593 else
2594 timeout += TCP_TIMEOUT_MIN;
2595 } else {
2596 timeout = TCP_TIMEOUT_INIT;
2597 }
2598
2599 /* If the RTO formula yields an earlier time, then use that time. */
2600 rto_delta_us = advancing_rto ?
2601 jiffies_to_usecs(inet_csk(sk)->icsk_rto) :
2602 tcp_rto_delta_us(sk); /* How far in future is RTO? */
2603 if (rto_delta_us > 0)
2604 timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us));
2605
2606 tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, TCP_RTO_MAX);
2607 return true;
2608}
2609
2610/* Thanks to skb fast clones, we can detect if a prior transmit of
2611 * a packet is still in a qdisc or driver queue.
2612 * In this case, there is very little point doing a retransmit !
2613 */
2614static bool skb_still_in_host_queue(const struct sock *sk,
2615 const struct sk_buff *skb)
2616{
2617 if (unlikely(skb_fclone_busy(sk, skb))) {
2618 NET_INC_STATS(sock_net(sk),
2619 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2620 return true;
2621 }
2622 return false;
2623}
2624
2625/* When probe timeout (PTO) fires, try send a new segment if possible, else
2626 * retransmit the last segment.
2627 */
2628void tcp_send_loss_probe(struct sock *sk)
2629{
2630 struct tcp_sock *tp = tcp_sk(sk);
2631 struct sk_buff *skb;
2632 int pcount;
2633 int mss = tcp_current_mss(sk);
2634
2635 /* At most one outstanding TLP */
2636 if (tp->tlp_high_seq)
2637 goto rearm_timer;
2638
2639 tp->tlp_retrans = 0;
2640 skb = tcp_send_head(sk);
2641 if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
2642 pcount = tp->packets_out;
2643 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2644 if (tp->packets_out > pcount)
2645 goto probe_sent;
2646 goto rearm_timer;
2647 }
2648 skb = skb_rb_last(&sk->tcp_rtx_queue);
2649 if (unlikely(!skb)) {
2650 WARN_ONCE(tp->packets_out,
2651 "invalid inflight: %u state %u cwnd %u mss %d\n",
2652 tp->packets_out, sk->sk_state, tp->snd_cwnd, mss);
2653 inet_csk(sk)->icsk_pending = 0;
2654 return;
2655 }
2656
2657 if (skb_still_in_host_queue(sk, skb))
2658 goto rearm_timer;
2659
2660 pcount = tcp_skb_pcount(skb);
2661 if (WARN_ON(!pcount))
2662 goto rearm_timer;
2663
2664 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2665 if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
2666 (pcount - 1) * mss, mss,
2667 GFP_ATOMIC)))
2668 goto rearm_timer;
2669 skb = skb_rb_next(skb);
2670 }
2671
2672 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2673 goto rearm_timer;
2674
2675 if (__tcp_retransmit_skb(sk, skb, 1))
2676 goto rearm_timer;
2677
2678 tp->tlp_retrans = 1;
2679
2680probe_sent:
2681 /* Record snd_nxt for loss detection. */
2682 tp->tlp_high_seq = tp->snd_nxt;
2683
2684 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2685 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2686 inet_csk(sk)->icsk_pending = 0;
2687rearm_timer:
2688 tcp_rearm_rto(sk);
2689}
2690
2691/* Push out any pending frames which were held back due to
2692 * TCP_CORK or attempt at coalescing tiny packets.
2693 * The socket must be locked by the caller.
2694 */
2695void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2696 int nonagle)
2697{
2698 /* If we are closed, the bytes will have to remain here.
2699 * In time closedown will finish, we empty the write queue and
2700 * all will be happy.
2701 */
2702 if (unlikely(sk->sk_state == TCP_CLOSE))
2703 return;
2704
2705 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2706 sk_gfp_mask(sk, GFP_ATOMIC)))
2707 tcp_check_probe_timer(sk);
2708}
2709
2710/* Send _single_ skb sitting at the send head. This function requires
2711 * true push pending frames to setup probe timer etc.
2712 */
2713void tcp_push_one(struct sock *sk, unsigned int mss_now)
2714{
2715 struct sk_buff *skb = tcp_send_head(sk);
2716
2717 BUG_ON(!skb || skb->len < mss_now);
2718
2719 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2720}
2721
2722/* This function returns the amount that we can raise the
2723 * usable window based on the following constraints
2724 *
2725 * 1. The window can never be shrunk once it is offered (RFC 793)
2726 * 2. We limit memory per socket
2727 *
2728 * RFC 1122:
2729 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2730 * RECV.NEXT + RCV.WIN fixed until:
2731 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2732 *
2733 * i.e. don't raise the right edge of the window until you can raise
2734 * it at least MSS bytes.
2735 *
2736 * Unfortunately, the recommended algorithm breaks header prediction,
2737 * since header prediction assumes th->window stays fixed.
2738 *
2739 * Strictly speaking, keeping th->window fixed violates the receiver
2740 * side SWS prevention criteria. The problem is that under this rule
2741 * a stream of single byte packets will cause the right side of the
2742 * window to always advance by a single byte.
2743 *
2744 * Of course, if the sender implements sender side SWS prevention
2745 * then this will not be a problem.
2746 *
2747 * BSD seems to make the following compromise:
2748 *
2749 * If the free space is less than the 1/4 of the maximum
2750 * space available and the free space is less than 1/2 mss,
2751 * then set the window to 0.
2752 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2753 * Otherwise, just prevent the window from shrinking
2754 * and from being larger than the largest representable value.
2755 *
2756 * This prevents incremental opening of the window in the regime
2757 * where TCP is limited by the speed of the reader side taking
2758 * data out of the TCP receive queue. It does nothing about
2759 * those cases where the window is constrained on the sender side
2760 * because the pipeline is full.
2761 *
2762 * BSD also seems to "accidentally" limit itself to windows that are a
2763 * multiple of MSS, at least until the free space gets quite small.
2764 * This would appear to be a side effect of the mbuf implementation.
2765 * Combining these two algorithms results in the observed behavior
2766 * of having a fixed window size at almost all times.
2767 *
2768 * Below we obtain similar behavior by forcing the offered window to
2769 * a multiple of the mss when it is feasible to do so.
2770 *
2771 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2772 * Regular options like TIMESTAMP are taken into account.
2773 */
2774u32 __tcp_select_window(struct sock *sk)
2775{
2776 struct inet_connection_sock *icsk = inet_csk(sk);
2777 struct tcp_sock *tp = tcp_sk(sk);
2778 /* MSS for the peer's data. Previous versions used mss_clamp
2779 * here. I don't know if the value based on our guesses
2780 * of peer's MSS is better for the performance. It's more correct
2781 * but may be worse for the performance because of rcv_mss
2782 * fluctuations. --SAW 1998/11/1
2783 */
2784 int mss = icsk->icsk_ack.rcv_mss;
2785 int free_space = tcp_space(sk);
2786 int allowed_space = tcp_full_space(sk);
2787 int full_space, window;
2788
2789 if (sk_is_mptcp(sk))
2790 mptcp_space(sk, &free_space, &allowed_space);
2791
2792 full_space = min_t(int, tp->window_clamp, allowed_space);
2793
2794 if (unlikely(mss > full_space)) {
2795 mss = full_space;
2796 if (mss <= 0)
2797 return 0;
2798 }
2799 if (free_space < (full_space >> 1)) {
2800 icsk->icsk_ack.quick = 0;
2801
2802 if (tcp_under_memory_pressure(sk))
2803 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2804 4U * tp->advmss);
2805
2806 /* free_space might become our new window, make sure we don't
2807 * increase it due to wscale.
2808 */
2809 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2810
2811 /* if free space is less than mss estimate, or is below 1/16th
2812 * of the maximum allowed, try to move to zero-window, else
2813 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2814 * new incoming data is dropped due to memory limits.
2815 * With large window, mss test triggers way too late in order
2816 * to announce zero window in time before rmem limit kicks in.
2817 */
2818 if (free_space < (allowed_space >> 4) || free_space < mss)
2819 return 0;
2820 }
2821
2822 if (free_space > tp->rcv_ssthresh)
2823 free_space = tp->rcv_ssthresh;
2824
2825 /* Don't do rounding if we are using window scaling, since the
2826 * scaled window will not line up with the MSS boundary anyway.
2827 */
2828 if (tp->rx_opt.rcv_wscale) {
2829 window = free_space;
2830
2831 /* Advertise enough space so that it won't get scaled away.
2832 * Import case: prevent zero window announcement if
2833 * 1<<rcv_wscale > mss.
2834 */
2835 window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale));
2836 } else {
2837 window = tp->rcv_wnd;
2838 /* Get the largest window that is a nice multiple of mss.
2839 * Window clamp already applied above.
2840 * If our current window offering is within 1 mss of the
2841 * free space we just keep it. This prevents the divide
2842 * and multiply from happening most of the time.
2843 * We also don't do any window rounding when the free space
2844 * is too small.
2845 */
2846 if (window <= free_space - mss || window > free_space)
2847 window = rounddown(free_space, mss);
2848 else if (mss == full_space &&
2849 free_space > window + (full_space >> 1))
2850 window = free_space;
2851 }
2852
2853 return window;
2854}
2855
2856void tcp_skb_collapse_tstamp(struct sk_buff *skb,
2857 const struct sk_buff *next_skb)
2858{
2859 if (unlikely(tcp_has_tx_tstamp(next_skb))) {
2860 const struct skb_shared_info *next_shinfo =
2861 skb_shinfo(next_skb);
2862 struct skb_shared_info *shinfo = skb_shinfo(skb);
2863
2864 shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2865 shinfo->tskey = next_shinfo->tskey;
2866 TCP_SKB_CB(skb)->txstamp_ack |=
2867 TCP_SKB_CB(next_skb)->txstamp_ack;
2868 }
2869}
2870
2871/* Collapses two adjacent SKB's during retransmission. */
2872static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
2873{
2874 struct tcp_sock *tp = tcp_sk(sk);
2875 struct sk_buff *next_skb = skb_rb_next(skb);
2876 int next_skb_size;
2877
2878 next_skb_size = next_skb->len;
2879
2880 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2881
2882 if (next_skb_size) {
2883 if (next_skb_size <= skb_availroom(skb))
2884 skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
2885 next_skb_size);
2886 else if (!tcp_skb_shift(skb, next_skb, 1, next_skb_size))
2887 return false;
2888 }
2889 tcp_highest_sack_replace(sk, next_skb, skb);
2890
2891 /* Update sequence range on original skb. */
2892 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2893
2894 /* Merge over control information. This moves PSH/FIN etc. over */
2895 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2896
2897 /* All done, get rid of second SKB and account for it so
2898 * packet counting does not break.
2899 */
2900 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2901 TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor;
2902
2903 /* changed transmit queue under us so clear hints */
2904 tcp_clear_retrans_hints_partial(tp);
2905 if (next_skb == tp->retransmit_skb_hint)
2906 tp->retransmit_skb_hint = skb;
2907
2908 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2909
2910 tcp_skb_collapse_tstamp(skb, next_skb);
2911
2912 tcp_rtx_queue_unlink_and_free(next_skb, sk);
2913 return true;
2914}
2915
2916/* Check if coalescing SKBs is legal. */
2917static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2918{
2919 if (tcp_skb_pcount(skb) > 1)
2920 return false;
2921 if (skb_cloned(skb))
2922 return false;
2923 /* Some heuristics for collapsing over SACK'd could be invented */
2924 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2925 return false;
2926
2927 return true;
2928}
2929
2930/* Collapse packets in the retransmit queue to make to create
2931 * less packets on the wire. This is only done on retransmission.
2932 */
2933static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2934 int space)
2935{
2936 struct tcp_sock *tp = tcp_sk(sk);
2937 struct sk_buff *skb = to, *tmp;
2938 bool first = true;
2939
2940 if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
2941 return;
2942 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2943 return;
2944
2945 skb_rbtree_walk_from_safe(skb, tmp) {
2946 if (!tcp_can_collapse(sk, skb))
2947 break;
2948
2949 if (!tcp_skb_can_collapse(to, skb))
2950 break;
2951
2952 space -= skb->len;
2953
2954 if (first) {
2955 first = false;
2956 continue;
2957 }
2958
2959 if (space < 0)
2960 break;
2961
2962 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2963 break;
2964
2965 if (!tcp_collapse_retrans(sk, to))
2966 break;
2967 }
2968}
2969
2970/* This retransmits one SKB. Policy decisions and retransmit queue
2971 * state updates are done by the caller. Returns non-zero if an
2972 * error occurred which prevented the send.
2973 */
2974int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
2975{
2976 struct inet_connection_sock *icsk = inet_csk(sk);
2977 struct tcp_sock *tp = tcp_sk(sk);
2978 unsigned int cur_mss;
2979 int diff, len, err;
2980
2981
2982 /* Inconclusive MTU probe */
2983 if (icsk->icsk_mtup.probe_size)
2984 icsk->icsk_mtup.probe_size = 0;
2985
2986 /* Do not sent more than we queued. 1/4 is reserved for possible
2987 * copying overhead: fragmentation, tunneling, mangling etc.
2988 */
2989 if (refcount_read(&sk->sk_wmem_alloc) >
2990 min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
2991 sk->sk_sndbuf))
2992 return -EAGAIN;
2993
2994 if (skb_still_in_host_queue(sk, skb))
2995 return -EBUSY;
2996
2997 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2998 if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) {
2999 WARN_ON_ONCE(1);
3000 return -EINVAL;
3001 }
3002 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
3003 return -ENOMEM;
3004 }
3005
3006 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3007 return -EHOSTUNREACH; /* Routing failure or similar. */
3008
3009 cur_mss = tcp_current_mss(sk);
3010
3011 /* If receiver has shrunk his window, and skb is out of
3012 * new window, do not retransmit it. The exception is the
3013 * case, when window is shrunk to zero. In this case
3014 * our retransmit serves as a zero window probe.
3015 */
3016 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
3017 TCP_SKB_CB(skb)->seq != tp->snd_una)
3018 return -EAGAIN;
3019
3020 len = cur_mss * segs;
3021 if (skb->len > len) {
3022 if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
3023 cur_mss, GFP_ATOMIC))
3024 return -ENOMEM; /* We'll try again later. */
3025 } else {
3026 if (skb_unclone(skb, GFP_ATOMIC))
3027 return -ENOMEM;
3028
3029 diff = tcp_skb_pcount(skb);
3030 tcp_set_skb_tso_segs(skb, cur_mss);
3031 diff -= tcp_skb_pcount(skb);
3032 if (diff)
3033 tcp_adjust_pcount(sk, skb, diff);
3034 if (skb->len < cur_mss)
3035 tcp_retrans_try_collapse(sk, skb, cur_mss);
3036 }
3037
3038 /* RFC3168, section 6.1.1.1. ECN fallback */
3039 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
3040 tcp_ecn_clear_syn(sk, skb);
3041
3042 /* Update global and local TCP statistics. */
3043 segs = tcp_skb_pcount(skb);
3044 TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
3045 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
3046 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3047 tp->total_retrans += segs;
3048 tp->bytes_retrans += skb->len;
3049
3050 /* make sure skb->data is aligned on arches that require it
3051 * and check if ack-trimming & collapsing extended the headroom
3052 * beyond what csum_start can cover.
3053 */
3054 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
3055 skb_headroom(skb) >= 0xFFFF)) {
3056 struct sk_buff *nskb;
3057
3058 tcp_skb_tsorted_save(skb) {
3059 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
3060 if (nskb) {
3061 nskb->dev = NULL;
3062 err = tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC);
3063 } else {
3064 err = -ENOBUFS;
3065 }
3066 } tcp_skb_tsorted_restore(skb);
3067
3068 if (!err) {
3069 tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns);
3070 tcp_rate_skb_sent(sk, skb);
3071 }
3072 } else {
3073 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3074 }
3075
3076 /* To avoid taking spuriously low RTT samples based on a timestamp
3077 * for a transmit that never happened, always mark EVER_RETRANS
3078 */
3079 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
3080
3081 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
3082 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
3083 TCP_SKB_CB(skb)->seq, segs, err);
3084
3085 if (likely(!err)) {
3086 trace_tcp_retransmit_skb(sk, skb);
3087 } else if (err != -EBUSY) {
3088 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
3089 }
3090 return err;
3091}
3092
3093int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
3094{
3095 struct tcp_sock *tp = tcp_sk(sk);
3096 int err = __tcp_retransmit_skb(sk, skb, segs);
3097
3098 if (err == 0) {
3099#if FASTRETRANS_DEBUG > 0
3100 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
3101 net_dbg_ratelimited("retrans_out leaked\n");
3102 }
3103#endif
3104 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
3105 tp->retrans_out += tcp_skb_pcount(skb);
3106 }
3107
3108 /* Save stamp of the first (attempted) retransmit. */
3109 if (!tp->retrans_stamp)
3110 tp->retrans_stamp = tcp_skb_timestamp(skb);
3111
3112 if (tp->undo_retrans < 0)
3113 tp->undo_retrans = 0;
3114 tp->undo_retrans += tcp_skb_pcount(skb);
3115 return err;
3116}
3117
3118/* This gets called after a retransmit timeout, and the initially
3119 * retransmitted data is acknowledged. It tries to continue
3120 * resending the rest of the retransmit queue, until either
3121 * we've sent it all or the congestion window limit is reached.
3122 */
3123void tcp_xmit_retransmit_queue(struct sock *sk)
3124{
3125 const struct inet_connection_sock *icsk = inet_csk(sk);
3126 struct sk_buff *skb, *rtx_head, *hole = NULL;
3127 struct tcp_sock *tp = tcp_sk(sk);
3128 bool rearm_timer = false;
3129 u32 max_segs;
3130 int mib_idx;
3131
3132 if (!tp->packets_out)
3133 return;
3134
3135 rtx_head = tcp_rtx_queue_head(sk);
3136 skb = tp->retransmit_skb_hint ?: rtx_head;
3137 max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
3138 skb_rbtree_walk_from(skb) {
3139 __u8 sacked;
3140 int segs;
3141
3142 if (tcp_pacing_check(sk))
3143 break;
3144
3145 /* we could do better than to assign each time */
3146 if (!hole)
3147 tp->retransmit_skb_hint = skb;
3148
3149 segs = tp->snd_cwnd - tcp_packets_in_flight(tp);
3150 if (segs <= 0)
3151 break;
3152 sacked = TCP_SKB_CB(skb)->sacked;
3153 /* In case tcp_shift_skb_data() have aggregated large skbs,
3154 * we need to make sure not sending too bigs TSO packets
3155 */
3156 segs = min_t(int, segs, max_segs);
3157
3158 if (tp->retrans_out >= tp->lost_out) {
3159 break;
3160 } else if (!(sacked & TCPCB_LOST)) {
3161 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
3162 hole = skb;
3163 continue;
3164
3165 } else {
3166 if (icsk->icsk_ca_state != TCP_CA_Loss)
3167 mib_idx = LINUX_MIB_TCPFASTRETRANS;
3168 else
3169 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
3170 }
3171
3172 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
3173 continue;
3174
3175 if (tcp_small_queue_check(sk, skb, 1))
3176 break;
3177
3178 if (tcp_retransmit_skb(sk, skb, segs))
3179 break;
3180
3181 NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb));
3182
3183 if (tcp_in_cwnd_reduction(sk))
3184 tp->prr_out += tcp_skb_pcount(skb);
3185
3186 if (skb == rtx_head &&
3187 icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
3188 rearm_timer = true;
3189
3190 }
3191 if (rearm_timer)
3192 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3193 inet_csk(sk)->icsk_rto,
3194 TCP_RTO_MAX);
3195}
3196
3197/* We allow to exceed memory limits for FIN packets to expedite
3198 * connection tear down and (memory) recovery.
3199 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3200 * or even be forced to close flow without any FIN.
3201 * In general, we want to allow one skb per socket to avoid hangs
3202 * with edge trigger epoll()
3203 */
3204void sk_forced_mem_schedule(struct sock *sk, int size)
3205{
3206 int amt;
3207
3208 if (size <= sk->sk_forward_alloc)
3209 return;
3210 amt = sk_mem_pages(size);
3211 sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
3212 sk_memory_allocated_add(sk, amt);
3213
3214 if (mem_cgroup_sockets_enabled && sk->sk_memcg)
3215 mem_cgroup_charge_skmem(sk->sk_memcg, amt);
3216}
3217
3218/* Send a FIN. The caller locks the socket for us.
3219 * We should try to send a FIN packet really hard, but eventually give up.
3220 */
3221void tcp_send_fin(struct sock *sk)
3222{
3223 struct sk_buff *skb, *tskb, *tail = tcp_write_queue_tail(sk);
3224 struct tcp_sock *tp = tcp_sk(sk);
3225
3226 /* Optimization, tack on the FIN if we have one skb in write queue and
3227 * this skb was not yet sent, or we are under memory pressure.
3228 * Note: in the latter case, FIN packet will be sent after a timeout,
3229 * as TCP stack thinks it has already been transmitted.
3230 */
3231 tskb = tail;
3232 if (!tskb && tcp_under_memory_pressure(sk))
3233 tskb = skb_rb_last(&sk->tcp_rtx_queue);
3234
3235 if (tskb) {
3236 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
3237 TCP_SKB_CB(tskb)->end_seq++;
3238 tp->write_seq++;
3239 if (!tail) {
3240 /* This means tskb was already sent.
3241 * Pretend we included the FIN on previous transmit.
3242 * We need to set tp->snd_nxt to the value it would have
3243 * if FIN had been sent. This is because retransmit path
3244 * does not change tp->snd_nxt.
3245 */
3246 WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1);
3247 return;
3248 }
3249 } else {
3250 skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
3251 if (unlikely(!skb))
3252 return;
3253
3254 INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
3255 skb_reserve(skb, MAX_TCP_HEADER);
3256 sk_forced_mem_schedule(sk, skb->truesize);
3257 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3258 tcp_init_nondata_skb(skb, tp->write_seq,
3259 TCPHDR_ACK | TCPHDR_FIN);
3260 tcp_queue_skb(sk, skb);
3261 }
3262 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
3263}
3264
3265/* We get here when a process closes a file descriptor (either due to
3266 * an explicit close() or as a byproduct of exit()'ing) and there
3267 * was unread data in the receive queue. This behavior is recommended
3268 * by RFC 2525, section 2.17. -DaveM
3269 */
3270void tcp_send_active_reset(struct sock *sk, gfp_t priority)
3271{
3272 struct sk_buff *skb;
3273
3274 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
3275
3276 /* NOTE: No TCP options attached and we never retransmit this. */
3277 skb = alloc_skb(MAX_TCP_HEADER, priority);
3278 if (!skb) {
3279 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3280 return;
3281 }
3282
3283 /* Reserve space for headers and prepare control bits. */
3284 skb_reserve(skb, MAX_TCP_HEADER);
3285 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
3286 TCPHDR_ACK | TCPHDR_RST);
3287 tcp_mstamp_refresh(tcp_sk(sk));
3288 /* Send it off. */
3289 if (tcp_transmit_skb(sk, skb, 0, priority))
3290 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
3291
3292 /* skb of trace_tcp_send_reset() keeps the skb that caused RST,
3293 * skb here is different to the troublesome skb, so use NULL
3294 */
3295 trace_tcp_send_reset(sk, NULL);
3296}
3297
3298/* Send a crossed SYN-ACK during socket establishment.
3299 * WARNING: This routine must only be called when we have already sent
3300 * a SYN packet that crossed the incoming SYN that caused this routine
3301 * to get called. If this assumption fails then the initial rcv_wnd
3302 * and rcv_wscale values will not be correct.
3303 */
3304int tcp_send_synack(struct sock *sk)
3305{
3306 struct sk_buff *skb;
3307
3308 skb = tcp_rtx_queue_head(sk);
3309 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
3310 pr_err("%s: wrong queue state\n", __func__);
3311 return -EFAULT;
3312 }
3313 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
3314 if (skb_cloned(skb)) {
3315 struct sk_buff *nskb;
3316
3317 tcp_skb_tsorted_save(skb) {
3318 nskb = skb_copy(skb, GFP_ATOMIC);
3319 } tcp_skb_tsorted_restore(skb);
3320 if (!nskb)
3321 return -ENOMEM;
3322 INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
3323 tcp_highest_sack_replace(sk, skb, nskb);
3324 tcp_rtx_queue_unlink_and_free(skb, sk);
3325 __skb_header_release(nskb);
3326 tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
3327 sk_wmem_queued_add(sk, nskb->truesize);
3328 sk_mem_charge(sk, nskb->truesize);
3329 skb = nskb;
3330 }
3331
3332 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
3333 tcp_ecn_send_synack(sk, skb);
3334 }
3335 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3336}
3337
3338/**
3339 * tcp_make_synack - Prepare a SYN-ACK.
3340 * sk: listener socket
3341 * dst: dst entry attached to the SYNACK
3342 * req: request_sock pointer
3343 * foc: cookie for tcp fast open
3344 * synack_type: Type of synback to prepare
3345 *
3346 * Allocate one skb and build a SYNACK packet.
3347 * @dst is consumed : Caller should not use it again.
3348 */
3349struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
3350 struct request_sock *req,
3351 struct tcp_fastopen_cookie *foc,
3352 enum tcp_synack_type synack_type)
3353{
3354 struct inet_request_sock *ireq = inet_rsk(req);
3355 const struct tcp_sock *tp = tcp_sk(sk);
3356 struct tcp_md5sig_key *md5 = NULL;
3357 struct tcp_out_options opts;
3358 struct sk_buff *skb;
3359 int tcp_header_size;
3360 struct tcphdr *th;
3361 int mss;
3362 u64 now;
3363
3364 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
3365 if (unlikely(!skb)) {
3366 dst_release(dst);
3367 return NULL;
3368 }
3369 /* Reserve space for headers. */
3370 skb_reserve(skb, MAX_TCP_HEADER);
3371
3372 switch (synack_type) {
3373 case TCP_SYNACK_NORMAL:
3374 skb_set_owner_w(skb, req_to_sk(req));
3375 break;
3376 case TCP_SYNACK_COOKIE:
3377 /* Under synflood, we do not attach skb to a socket,
3378 * to avoid false sharing.
3379 */
3380 break;
3381 case TCP_SYNACK_FASTOPEN:
3382 /* sk is a const pointer, because we want to express multiple
3383 * cpu might call us concurrently.
3384 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3385 */
3386 skb_set_owner_w(skb, (struct sock *)sk);
3387 break;
3388 }
3389 skb_dst_set(skb, dst);
3390
3391 mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3392
3393 memset(&opts, 0, sizeof(opts));
3394 now = tcp_clock_ns();
3395#ifdef CONFIG_SYN_COOKIES
3396 if (unlikely(synack_type == TCP_SYNACK_COOKIE && ireq->tstamp_ok))
3397 skb->skb_mstamp_ns = cookie_init_timestamp(req, now);
3398 else
3399#endif
3400 {
3401 skb->skb_mstamp_ns = now;
3402 if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */
3403 tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);
3404 }
3405
3406#ifdef CONFIG_TCP_MD5SIG
3407 rcu_read_lock();
3408 md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
3409#endif
3410 skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3411 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
3412 foc, synack_type) + sizeof(*th);
3413
3414 skb_push(skb, tcp_header_size);
3415 skb_reset_transport_header(skb);
3416
3417 th = (struct tcphdr *)skb->data;
3418 memset(th, 0, sizeof(struct tcphdr));
3419 th->syn = 1;
3420 th->ack = 1;
3421 tcp_ecn_make_synack(req, th);
3422 th->source = htons(ireq->ir_num);
3423 th->dest = ireq->ir_rmt_port;
3424 skb->mark = ireq->ir_mark;
3425 skb->ip_summed = CHECKSUM_PARTIAL;
3426 th->seq = htonl(tcp_rsk(req)->snt_isn);
3427 /* XXX data is queued and acked as is. No buffer/window check */
3428 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
3429
3430 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3431 th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3432 tcp_options_write((__be32 *)(th + 1), NULL, &opts);
3433 th->doff = (tcp_header_size >> 2);
3434 __TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
3435
3436#ifdef CONFIG_TCP_MD5SIG
3437 /* Okay, we have all we need - do the md5 hash if needed */
3438 if (md5)
3439 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3440 md5, req_to_sk(req), skb);
3441 rcu_read_unlock();
3442#endif
3443
3444 skb->skb_mstamp_ns = now;
3445 tcp_add_tx_delay(skb, tp);
3446
3447 return skb;
3448}
3449EXPORT_SYMBOL(tcp_make_synack);
3450
3451static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
3452{
3453 struct inet_connection_sock *icsk = inet_csk(sk);
3454 const struct tcp_congestion_ops *ca;
3455 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
3456
3457 if (ca_key == TCP_CA_UNSPEC)
3458 return;
3459
3460 rcu_read_lock();
3461 ca = tcp_ca_find_key(ca_key);
3462 if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
3463 bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
3464 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
3465 icsk->icsk_ca_ops = ca;
3466 }
3467 rcu_read_unlock();
3468}
3469
3470/* Do all connect socket setups that can be done AF independent. */
3471static void tcp_connect_init(struct sock *sk)
3472{
3473 const struct dst_entry *dst = __sk_dst_get(sk);
3474 struct tcp_sock *tp = tcp_sk(sk);
3475 __u8 rcv_wscale;
3476 u32 rcv_wnd;
3477
3478 /* We'll fix this up when we get a response from the other end.
3479 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3480 */
3481 tp->tcp_header_len = sizeof(struct tcphdr);
3482 if (sock_net(sk)->ipv4.sysctl_tcp_timestamps)
3483 tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
3484
3485#ifdef CONFIG_TCP_MD5SIG
3486 if (tp->af_specific->md5_lookup(sk, sk))
3487 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
3488#endif
3489
3490 /* If user gave his TCP_MAXSEG, record it to clamp */
3491 if (tp->rx_opt.user_mss)
3492 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3493 tp->max_window = 0;
3494 tcp_mtup_init(sk);
3495 tcp_sync_mss(sk, dst_mtu(dst));
3496
3497 tcp_ca_dst_init(sk, dst);
3498
3499 if (!tp->window_clamp)
3500 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3501 tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
3502
3503 tcp_initialize_rcv_mss(sk);
3504
3505 /* limit the window selection if the user enforce a smaller rx buffer */
3506 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
3507 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
3508 tp->window_clamp = tcp_full_space(sk);
3509
3510 rcv_wnd = tcp_rwnd_init_bpf(sk);
3511 if (rcv_wnd == 0)
3512 rcv_wnd = dst_metric(dst, RTAX_INITRWND);
3513
3514 tcp_select_initial_window(sk, tcp_full_space(sk),
3515 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
3516 &tp->rcv_wnd,
3517 &tp->window_clamp,
3518 sock_net(sk)->ipv4.sysctl_tcp_window_scaling,
3519 &rcv_wscale,
3520 rcv_wnd);
3521
3522 tp->rx_opt.rcv_wscale = rcv_wscale;
3523 tp->rcv_ssthresh = tp->rcv_wnd;
3524
3525 sk->sk_err = 0;
3526 sock_reset_flag(sk, SOCK_DONE);
3527 tp->snd_wnd = 0;
3528 tcp_init_wl(tp, 0);
3529 tcp_write_queue_purge(sk);
3530 tp->snd_una = tp->write_seq;
3531 tp->snd_sml = tp->write_seq;
3532 tp->snd_up = tp->write_seq;
3533 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3534
3535 if (likely(!tp->repair))
3536 tp->rcv_nxt = 0;
3537 else
3538 tp->rcv_tstamp = tcp_jiffies32;
3539 tp->rcv_wup = tp->rcv_nxt;
3540 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
3541
3542 inet_csk(sk)->icsk_rto = tcp_timeout_init(sk);
3543 inet_csk(sk)->icsk_retransmits = 0;
3544 tcp_clear_retrans(tp);
3545}
3546
3547static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
3548{
3549 struct tcp_sock *tp = tcp_sk(sk);
3550 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
3551
3552 tcb->end_seq += skb->len;
3553 __skb_header_release(skb);
3554 sk_wmem_queued_add(sk, skb->truesize);
3555 sk_mem_charge(sk, skb->truesize);
3556 WRITE_ONCE(tp->write_seq, tcb->end_seq);
3557 tp->packets_out += tcp_skb_pcount(skb);
3558}
3559
3560/* Build and send a SYN with data and (cached) Fast Open cookie. However,
3561 * queue a data-only packet after the regular SYN, such that regular SYNs
3562 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3563 * only the SYN sequence, the data are retransmitted in the first ACK.
3564 * If cookie is not cached or other error occurs, falls back to send a
3565 * regular SYN with Fast Open cookie request option.
3566 */
3567static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
3568{
3569 struct tcp_sock *tp = tcp_sk(sk);
3570 struct tcp_fastopen_request *fo = tp->fastopen_req;
3571 int space, err = 0;
3572 struct sk_buff *syn_data;
3573
3574 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
3575 if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie))
3576 goto fallback;
3577
3578 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3579 * user-MSS. Reserve maximum option space for middleboxes that add
3580 * private TCP options. The cost is reduced data space in SYN :(
3581 */
3582 tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
3583
3584 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3585 MAX_TCP_OPTION_SPACE;
3586
3587 space = min_t(size_t, space, fo->size);
3588
3589 /* limit to order-0 allocations */
3590 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
3591
3592 syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3593 if (!syn_data)
3594 goto fallback;
3595 syn_data->ip_summed = CHECKSUM_PARTIAL;
3596 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3597 if (space) {
3598 int copied = copy_from_iter(skb_put(syn_data, space), space,
3599 &fo->data->msg_iter);
3600 if (unlikely(!copied)) {
3601 tcp_skb_tsorted_anchor_cleanup(syn_data);
3602 kfree_skb(syn_data);
3603 goto fallback;
3604 }
3605 if (copied != space) {
3606 skb_trim(syn_data, copied);
3607 space = copied;
3608 }
3609 skb_zcopy_set(syn_data, fo->uarg, NULL);
3610 }
3611 /* No more data pending in inet_wait_for_connect() */
3612 if (space == fo->size)
3613 fo->data = NULL;
3614 fo->copied = space;
3615
3616 tcp_connect_queue_skb(sk, syn_data);
3617 if (syn_data->len)
3618 tcp_chrono_start(sk, TCP_CHRONO_BUSY);
3619
3620 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3621
3622 syn->skb_mstamp_ns = syn_data->skb_mstamp_ns;
3623
3624 /* Now full SYN+DATA was cloned and sent (or not),
3625 * remove the SYN from the original skb (syn_data)
3626 * we keep in write queue in case of a retransmit, as we
3627 * also have the SYN packet (with no data) in the same queue.
3628 */
3629 TCP_SKB_CB(syn_data)->seq++;
3630 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
3631 if (!err) {
3632 tp->syn_data = (fo->copied > 0);
3633 tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
3634 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3635 goto done;
3636 }
3637
3638 /* data was not sent, put it in write_queue */
3639 __skb_queue_tail(&sk->sk_write_queue, syn_data);
3640 tp->packets_out -= tcp_skb_pcount(syn_data);
3641
3642fallback:
3643 /* Send a regular SYN with Fast Open cookie request option */
3644 if (fo->cookie.len > 0)
3645 fo->cookie.len = 0;
3646 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3647 if (err)
3648 tp->syn_fastopen = 0;
3649done:
3650 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3651 return err;
3652}
3653
3654/* Build a SYN and send it off. */
3655int tcp_connect(struct sock *sk)
3656{
3657 struct tcp_sock *tp = tcp_sk(sk);
3658 struct sk_buff *buff;
3659 int err;
3660
3661 tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
3662
3663 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
3664 return -EHOSTUNREACH; /* Routing failure or similar. */
3665
3666 tcp_connect_init(sk);
3667
3668 if (unlikely(tp->repair)) {
3669 tcp_finish_connect(sk, NULL);
3670 return 0;
3671 }
3672
3673 buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3674 if (unlikely(!buff))
3675 return -ENOBUFS;
3676
3677 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3678 tcp_mstamp_refresh(tp);
3679 tp->retrans_stamp = tcp_time_stamp(tp);
3680 tcp_connect_queue_skb(sk, buff);
3681 tcp_ecn_send_syn(sk, buff);
3682 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
3683
3684 /* Send off SYN; include data in Fast Open. */
3685 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3686 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3687 if (err == -ECONNREFUSED)
3688 return err;
3689
3690 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3691 * in order to make this packet get counted in tcpOutSegs.
3692 */
3693 WRITE_ONCE(tp->snd_nxt, tp->write_seq);
3694 tp->pushed_seq = tp->write_seq;
3695 buff = tcp_send_head(sk);
3696 if (unlikely(buff)) {
3697 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq);
3698 tp->pushed_seq = TCP_SKB_CB(buff)->seq;
3699 }
3700 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3701
3702 /* Timer for repeating the SYN until an answer. */
3703 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3704 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3705 return 0;
3706}
3707EXPORT_SYMBOL(tcp_connect);
3708
3709/* Send out a delayed ack, the caller does the policy checking
3710 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3711 * for details.
3712 */
3713void tcp_send_delayed_ack(struct sock *sk)
3714{
3715 struct inet_connection_sock *icsk = inet_csk(sk);
3716 int ato = icsk->icsk_ack.ato;
3717 unsigned long timeout;
3718
3719 if (ato > TCP_DELACK_MIN) {
3720 const struct tcp_sock *tp = tcp_sk(sk);
3721 int max_ato = HZ / 2;
3722
3723 if (inet_csk_in_pingpong_mode(sk) ||
3724 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3725 max_ato = TCP_DELACK_MAX;
3726
3727 /* Slow path, intersegment interval is "high". */
3728
3729 /* If some rtt estimate is known, use it to bound delayed ack.
3730 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3731 * directly.
3732 */
3733 if (tp->srtt_us) {
3734 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3735 TCP_DELACK_MIN);
3736
3737 if (rtt < max_ato)
3738 max_ato = rtt;
3739 }
3740
3741 ato = min(ato, max_ato);
3742 }
3743
3744 /* Stay within the limit we were given */
3745 timeout = jiffies + ato;
3746
3747 /* Use new timeout only if there wasn't a older one earlier. */
3748 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3749 /* If delack timer was blocked or is about to expire,
3750 * send ACK now.
3751 */
3752 if (icsk->icsk_ack.blocked ||
3753 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3754 tcp_send_ack(sk);
3755 return;
3756 }
3757
3758 if (!time_before(timeout, icsk->icsk_ack.timeout))
3759 timeout = icsk->icsk_ack.timeout;
3760 }
3761 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3762 icsk->icsk_ack.timeout = timeout;
3763 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3764}
3765
3766/* This routine sends an ack and also updates the window. */
3767void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
3768{
3769 struct sk_buff *buff;
3770
3771 /* If we have been reset, we may not send again. */
3772 if (sk->sk_state == TCP_CLOSE)
3773 return;
3774
3775 /* We are not putting this on the write queue, so
3776 * tcp_transmit_skb() will set the ownership to this
3777 * sock.
3778 */
3779 buff = alloc_skb(MAX_TCP_HEADER,
3780 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3781 if (unlikely(!buff)) {
3782 inet_csk_schedule_ack(sk);
3783 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
3784 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
3785 TCP_DELACK_MAX, TCP_RTO_MAX);
3786 return;
3787 }
3788
3789 /* Reserve space for headers and prepare control bits. */
3790 skb_reserve(buff, MAX_TCP_HEADER);
3791 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3792
3793 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
3794 * too much.
3795 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
3796 */
3797 skb_set_tcp_pure_ack(buff);
3798
3799 /* Send it off, this clears delayed acks for us. */
3800 __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt);
3801}
3802EXPORT_SYMBOL_GPL(__tcp_send_ack);
3803
3804void tcp_send_ack(struct sock *sk)
3805{
3806 __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
3807}
3808
3809/* This routine sends a packet with an out of date sequence
3810 * number. It assumes the other end will try to ack it.
3811 *
3812 * Question: what should we make while urgent mode?
3813 * 4.4BSD forces sending single byte of data. We cannot send
3814 * out of window data, because we have SND.NXT==SND.MAX...
3815 *
3816 * Current solution: to send TWO zero-length segments in urgent mode:
3817 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3818 * out-of-date with SND.UNA-1 to probe window.
3819 */
3820static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
3821{
3822 struct tcp_sock *tp = tcp_sk(sk);
3823 struct sk_buff *skb;
3824
3825 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3826 skb = alloc_skb(MAX_TCP_HEADER,
3827 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3828 if (!skb)
3829 return -1;
3830
3831 /* Reserve space for headers and set control bits. */
3832 skb_reserve(skb, MAX_TCP_HEADER);
3833 /* Use a previous sequence. This should cause the other
3834 * end to send an ack. Don't queue or clone SKB, just
3835 * send it.
3836 */
3837 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3838 NET_INC_STATS(sock_net(sk), mib);
3839 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
3840}
3841
3842/* Called from setsockopt( ... TCP_REPAIR ) */
3843void tcp_send_window_probe(struct sock *sk)
3844{
3845 if (sk->sk_state == TCP_ESTABLISHED) {
3846 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3847 tcp_mstamp_refresh(tcp_sk(sk));
3848 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
3849 }
3850}
3851
3852/* Initiate keepalive or window probe from timer. */
3853int tcp_write_wakeup(struct sock *sk, int mib)
3854{
3855 struct tcp_sock *tp = tcp_sk(sk);
3856 struct sk_buff *skb;
3857
3858 if (sk->sk_state == TCP_CLOSE)
3859 return -1;
3860
3861 skb = tcp_send_head(sk);
3862 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3863 int err;
3864 unsigned int mss = tcp_current_mss(sk);
3865 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3866
3867 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
3868 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
3869
3870 /* We are probing the opening of a window
3871 * but the window size is != 0
3872 * must have been a result SWS avoidance ( sender )
3873 */
3874 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
3875 skb->len > mss) {
3876 seg_size = min(seg_size, mss);
3877 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3878 if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
3879 skb, seg_size, mss, GFP_ATOMIC))
3880 return -1;
3881 } else if (!tcp_skb_pcount(skb))
3882 tcp_set_skb_tso_segs(skb, mss);
3883
3884 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3885 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3886 if (!err)
3887 tcp_event_new_data_sent(sk, skb);
3888 return err;
3889 } else {
3890 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3891 tcp_xmit_probe_skb(sk, 1, mib);
3892 return tcp_xmit_probe_skb(sk, 0, mib);
3893 }
3894}
3895
3896/* A window probe timeout has occurred. If window is not closed send
3897 * a partial packet else a zero probe.
3898 */
3899void tcp_send_probe0(struct sock *sk)
3900{
3901 struct inet_connection_sock *icsk = inet_csk(sk);
3902 struct tcp_sock *tp = tcp_sk(sk);
3903 struct net *net = sock_net(sk);
3904 unsigned long timeout;
3905 int err;
3906
3907 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
3908
3909 if (tp->packets_out || tcp_write_queue_empty(sk)) {
3910 /* Cancel probe timer, if it is not required. */
3911 icsk->icsk_probes_out = 0;
3912 icsk->icsk_backoff = 0;
3913 return;
3914 }
3915
3916 icsk->icsk_probes_out++;
3917 if (err <= 0) {
3918 if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3919 icsk->icsk_backoff++;
3920 timeout = tcp_probe0_when(sk, TCP_RTO_MAX);
3921 } else {
3922 /* If packet was not sent due to local congestion,
3923 * Let senders fight for local resources conservatively.
3924 */
3925 timeout = TCP_RESOURCE_PROBE_INTERVAL;
3926 }
3927 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX);
3928}
3929
3930int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3931{
3932 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
3933 struct flowi fl;
3934 int res;
3935
3936 tcp_rsk(req)->txhash = net_tx_rndhash();
3937 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL);
3938 if (!res) {
3939 __TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
3940 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3941 if (unlikely(tcp_passive_fastopen(sk)))
3942 tcp_sk(sk)->total_retrans++;
3943 trace_tcp_retransmit_synack(sk, req);
3944 }
3945 return res;
3946}
3947EXPORT_SYMBOL(tcp_rtx_synack);
1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Authors: Ross Biro
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
19 */
20
21/*
22 * Changes: Pedro Roque : Retransmit queue handled by TCP.
23 * : Fragmentation on mtu decrease
24 * : Segment collapse on retransmit
25 * : AF independence
26 *
27 * Linus Torvalds : send_delayed_ack
28 * David S. Miller : Charge memory using the right skb
29 * during syn/ack processing.
30 * David S. Miller : Output engine completely rewritten.
31 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
32 * Cacophonix Gaul : draft-minshall-nagle-01
33 * J Hadi Salim : ECN support
34 *
35 */
36
37#define pr_fmt(fmt) "TCP: " fmt
38
39#include <net/tcp.h>
40
41#include <linux/compiler.h>
42#include <linux/gfp.h>
43#include <linux/module.h>
44
45/* People can turn this off for buggy TCP's found in printers etc. */
46int sysctl_tcp_retrans_collapse __read_mostly = 1;
47
48/* People can turn this on to work with those rare, broken TCPs that
49 * interpret the window field as a signed quantity.
50 */
51int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
52
53/* Default TSQ limit of two TSO segments */
54int sysctl_tcp_limit_output_bytes __read_mostly = 131072;
55
56/* This limits the percentage of the congestion window which we
57 * will allow a single TSO frame to consume. Building TSO frames
58 * which are too large can cause TCP streams to be bursty.
59 */
60int sysctl_tcp_tso_win_divisor __read_mostly = 3;
61
62int sysctl_tcp_mtu_probing __read_mostly = 0;
63int sysctl_tcp_base_mss __read_mostly = TCP_BASE_MSS;
64
65/* By default, RFC2861 behavior. */
66int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
67
68unsigned int sysctl_tcp_notsent_lowat __read_mostly = UINT_MAX;
69EXPORT_SYMBOL(sysctl_tcp_notsent_lowat);
70
71static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
72 int push_one, gfp_t gfp);
73
74/* Account for new data that has been sent to the network. */
75static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
76{
77 struct inet_connection_sock *icsk = inet_csk(sk);
78 struct tcp_sock *tp = tcp_sk(sk);
79 unsigned int prior_packets = tp->packets_out;
80
81 tcp_advance_send_head(sk, skb);
82 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
83
84 tp->packets_out += tcp_skb_pcount(skb);
85 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
86 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
87 tcp_rearm_rto(sk);
88 }
89
90 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
91 tcp_skb_pcount(skb));
92}
93
94/* SND.NXT, if window was not shrunk.
95 * If window has been shrunk, what should we make? It is not clear at all.
96 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
97 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
98 * invalid. OK, let's make this for now:
99 */
100static inline __u32 tcp_acceptable_seq(const struct sock *sk)
101{
102 const struct tcp_sock *tp = tcp_sk(sk);
103
104 if (!before(tcp_wnd_end(tp), tp->snd_nxt))
105 return tp->snd_nxt;
106 else
107 return tcp_wnd_end(tp);
108}
109
110/* Calculate mss to advertise in SYN segment.
111 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
112 *
113 * 1. It is independent of path mtu.
114 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
115 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
116 * attached devices, because some buggy hosts are confused by
117 * large MSS.
118 * 4. We do not make 3, we advertise MSS, calculated from first
119 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
120 * This may be overridden via information stored in routing table.
121 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
122 * probably even Jumbo".
123 */
124static __u16 tcp_advertise_mss(struct sock *sk)
125{
126 struct tcp_sock *tp = tcp_sk(sk);
127 const struct dst_entry *dst = __sk_dst_get(sk);
128 int mss = tp->advmss;
129
130 if (dst) {
131 unsigned int metric = dst_metric_advmss(dst);
132
133 if (metric < mss) {
134 mss = metric;
135 tp->advmss = mss;
136 }
137 }
138
139 return (__u16)mss;
140}
141
142/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
143 * This is the first part of cwnd validation mechanism. */
144static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst)
145{
146 struct tcp_sock *tp = tcp_sk(sk);
147 s32 delta = tcp_time_stamp - tp->lsndtime;
148 u32 restart_cwnd = tcp_init_cwnd(tp, dst);
149 u32 cwnd = tp->snd_cwnd;
150
151 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
152
153 tp->snd_ssthresh = tcp_current_ssthresh(sk);
154 restart_cwnd = min(restart_cwnd, cwnd);
155
156 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
157 cwnd >>= 1;
158 tp->snd_cwnd = max(cwnd, restart_cwnd);
159 tp->snd_cwnd_stamp = tcp_time_stamp;
160 tp->snd_cwnd_used = 0;
161}
162
163/* Congestion state accounting after a packet has been sent. */
164static void tcp_event_data_sent(struct tcp_sock *tp,
165 struct sock *sk)
166{
167 struct inet_connection_sock *icsk = inet_csk(sk);
168 const u32 now = tcp_time_stamp;
169 const struct dst_entry *dst = __sk_dst_get(sk);
170
171 if (sysctl_tcp_slow_start_after_idle &&
172 (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
173 tcp_cwnd_restart(sk, __sk_dst_get(sk));
174
175 tp->lsndtime = now;
176
177 /* If it is a reply for ato after last received
178 * packet, enter pingpong mode.
179 */
180 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato &&
181 (!dst || !dst_metric(dst, RTAX_QUICKACK)))
182 icsk->icsk_ack.pingpong = 1;
183}
184
185/* Account for an ACK we sent. */
186static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
187{
188 tcp_dec_quickack_mode(sk, pkts);
189 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
190}
191
192
193u32 tcp_default_init_rwnd(u32 mss)
194{
195 /* Initial receive window should be twice of TCP_INIT_CWND to
196 * enable proper sending of new unsent data during fast recovery
197 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
198 * limit when mss is larger than 1460.
199 */
200 u32 init_rwnd = TCP_INIT_CWND * 2;
201
202 if (mss > 1460)
203 init_rwnd = max((1460 * init_rwnd) / mss, 2U);
204 return init_rwnd;
205}
206
207/* Determine a window scaling and initial window to offer.
208 * Based on the assumption that the given amount of space
209 * will be offered. Store the results in the tp structure.
210 * NOTE: for smooth operation initial space offering should
211 * be a multiple of mss if possible. We assume here that mss >= 1.
212 * This MUST be enforced by all callers.
213 */
214void tcp_select_initial_window(int __space, __u32 mss,
215 __u32 *rcv_wnd, __u32 *window_clamp,
216 int wscale_ok, __u8 *rcv_wscale,
217 __u32 init_rcv_wnd)
218{
219 unsigned int space = (__space < 0 ? 0 : __space);
220
221 /* If no clamp set the clamp to the max possible scaled window */
222 if (*window_clamp == 0)
223 (*window_clamp) = (65535 << 14);
224 space = min(*window_clamp, space);
225
226 /* Quantize space offering to a multiple of mss if possible. */
227 if (space > mss)
228 space = (space / mss) * mss;
229
230 /* NOTE: offering an initial window larger than 32767
231 * will break some buggy TCP stacks. If the admin tells us
232 * it is likely we could be speaking with such a buggy stack
233 * we will truncate our initial window offering to 32K-1
234 * unless the remote has sent us a window scaling option,
235 * which we interpret as a sign the remote TCP is not
236 * misinterpreting the window field as a signed quantity.
237 */
238 if (sysctl_tcp_workaround_signed_windows)
239 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
240 else
241 (*rcv_wnd) = space;
242
243 (*rcv_wscale) = 0;
244 if (wscale_ok) {
245 /* Set window scaling on max possible window
246 * See RFC1323 for an explanation of the limit to 14
247 */
248 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
249 space = min_t(u32, space, *window_clamp);
250 while (space > 65535 && (*rcv_wscale) < 14) {
251 space >>= 1;
252 (*rcv_wscale)++;
253 }
254 }
255
256 if (mss > (1 << *rcv_wscale)) {
257 if (!init_rcv_wnd) /* Use default unless specified otherwise */
258 init_rcv_wnd = tcp_default_init_rwnd(mss);
259 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
260 }
261
262 /* Set the clamp no higher than max representable value */
263 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
264}
265EXPORT_SYMBOL(tcp_select_initial_window);
266
267/* Chose a new window to advertise, update state in tcp_sock for the
268 * socket, and return result with RFC1323 scaling applied. The return
269 * value can be stuffed directly into th->window for an outgoing
270 * frame.
271 */
272static u16 tcp_select_window(struct sock *sk)
273{
274 struct tcp_sock *tp = tcp_sk(sk);
275 u32 old_win = tp->rcv_wnd;
276 u32 cur_win = tcp_receive_window(tp);
277 u32 new_win = __tcp_select_window(sk);
278
279 /* Never shrink the offered window */
280 if (new_win < cur_win) {
281 /* Danger Will Robinson!
282 * Don't update rcv_wup/rcv_wnd here or else
283 * we will not be able to advertise a zero
284 * window in time. --DaveM
285 *
286 * Relax Will Robinson.
287 */
288 if (new_win == 0)
289 NET_INC_STATS(sock_net(sk),
290 LINUX_MIB_TCPWANTZEROWINDOWADV);
291 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
292 }
293 tp->rcv_wnd = new_win;
294 tp->rcv_wup = tp->rcv_nxt;
295
296 /* Make sure we do not exceed the maximum possible
297 * scaled window.
298 */
299 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
300 new_win = min(new_win, MAX_TCP_WINDOW);
301 else
302 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
303
304 /* RFC1323 scaling applied */
305 new_win >>= tp->rx_opt.rcv_wscale;
306
307 /* If we advertise zero window, disable fast path. */
308 if (new_win == 0) {
309 tp->pred_flags = 0;
310 if (old_win)
311 NET_INC_STATS(sock_net(sk),
312 LINUX_MIB_TCPTOZEROWINDOWADV);
313 } else if (old_win == 0) {
314 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
315 }
316
317 return new_win;
318}
319
320/* Packet ECN state for a SYN-ACK */
321static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb)
322{
323 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
324 if (!(tp->ecn_flags & TCP_ECN_OK))
325 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
326}
327
328/* Packet ECN state for a SYN. */
329static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
330{
331 struct tcp_sock *tp = tcp_sk(sk);
332
333 tp->ecn_flags = 0;
334 if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1) {
335 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
336 tp->ecn_flags = TCP_ECN_OK;
337 }
338}
339
340static __inline__ void
341TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th)
342{
343 if (inet_rsk(req)->ecn_ok)
344 th->ece = 1;
345}
346
347/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
348 * be sent.
349 */
350static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
351 int tcp_header_len)
352{
353 struct tcp_sock *tp = tcp_sk(sk);
354
355 if (tp->ecn_flags & TCP_ECN_OK) {
356 /* Not-retransmitted data segment: set ECT and inject CWR. */
357 if (skb->len != tcp_header_len &&
358 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
359 INET_ECN_xmit(sk);
360 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
361 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
362 tcp_hdr(skb)->cwr = 1;
363 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
364 }
365 } else {
366 /* ACK or retransmitted segment: clear ECT|CE */
367 INET_ECN_dontxmit(sk);
368 }
369 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
370 tcp_hdr(skb)->ece = 1;
371 }
372}
373
374/* Constructs common control bits of non-data skb. If SYN/FIN is present,
375 * auto increment end seqno.
376 */
377static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
378{
379 struct skb_shared_info *shinfo = skb_shinfo(skb);
380
381 skb->ip_summed = CHECKSUM_PARTIAL;
382 skb->csum = 0;
383
384 TCP_SKB_CB(skb)->tcp_flags = flags;
385 TCP_SKB_CB(skb)->sacked = 0;
386
387 shinfo->gso_segs = 1;
388 shinfo->gso_size = 0;
389 shinfo->gso_type = 0;
390
391 TCP_SKB_CB(skb)->seq = seq;
392 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
393 seq++;
394 TCP_SKB_CB(skb)->end_seq = seq;
395}
396
397static inline bool tcp_urg_mode(const struct tcp_sock *tp)
398{
399 return tp->snd_una != tp->snd_up;
400}
401
402#define OPTION_SACK_ADVERTISE (1 << 0)
403#define OPTION_TS (1 << 1)
404#define OPTION_MD5 (1 << 2)
405#define OPTION_WSCALE (1 << 3)
406#define OPTION_FAST_OPEN_COOKIE (1 << 8)
407
408struct tcp_out_options {
409 u16 options; /* bit field of OPTION_* */
410 u16 mss; /* 0 to disable */
411 u8 ws; /* window scale, 0 to disable */
412 u8 num_sack_blocks; /* number of SACK blocks to include */
413 u8 hash_size; /* bytes in hash_location */
414 __u8 *hash_location; /* temporary pointer, overloaded */
415 __u32 tsval, tsecr; /* need to include OPTION_TS */
416 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
417};
418
419/* Write previously computed TCP options to the packet.
420 *
421 * Beware: Something in the Internet is very sensitive to the ordering of
422 * TCP options, we learned this through the hard way, so be careful here.
423 * Luckily we can at least blame others for their non-compliance but from
424 * inter-operability perspective it seems that we're somewhat stuck with
425 * the ordering which we have been using if we want to keep working with
426 * those broken things (not that it currently hurts anybody as there isn't
427 * particular reason why the ordering would need to be changed).
428 *
429 * At least SACK_PERM as the first option is known to lead to a disaster
430 * (but it may well be that other scenarios fail similarly).
431 */
432static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
433 struct tcp_out_options *opts)
434{
435 u16 options = opts->options; /* mungable copy */
436
437 if (unlikely(OPTION_MD5 & options)) {
438 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
439 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
440 /* overload cookie hash location */
441 opts->hash_location = (__u8 *)ptr;
442 ptr += 4;
443 }
444
445 if (unlikely(opts->mss)) {
446 *ptr++ = htonl((TCPOPT_MSS << 24) |
447 (TCPOLEN_MSS << 16) |
448 opts->mss);
449 }
450
451 if (likely(OPTION_TS & options)) {
452 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
453 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
454 (TCPOLEN_SACK_PERM << 16) |
455 (TCPOPT_TIMESTAMP << 8) |
456 TCPOLEN_TIMESTAMP);
457 options &= ~OPTION_SACK_ADVERTISE;
458 } else {
459 *ptr++ = htonl((TCPOPT_NOP << 24) |
460 (TCPOPT_NOP << 16) |
461 (TCPOPT_TIMESTAMP << 8) |
462 TCPOLEN_TIMESTAMP);
463 }
464 *ptr++ = htonl(opts->tsval);
465 *ptr++ = htonl(opts->tsecr);
466 }
467
468 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
469 *ptr++ = htonl((TCPOPT_NOP << 24) |
470 (TCPOPT_NOP << 16) |
471 (TCPOPT_SACK_PERM << 8) |
472 TCPOLEN_SACK_PERM);
473 }
474
475 if (unlikely(OPTION_WSCALE & options)) {
476 *ptr++ = htonl((TCPOPT_NOP << 24) |
477 (TCPOPT_WINDOW << 16) |
478 (TCPOLEN_WINDOW << 8) |
479 opts->ws);
480 }
481
482 if (unlikely(opts->num_sack_blocks)) {
483 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
484 tp->duplicate_sack : tp->selective_acks;
485 int this_sack;
486
487 *ptr++ = htonl((TCPOPT_NOP << 24) |
488 (TCPOPT_NOP << 16) |
489 (TCPOPT_SACK << 8) |
490 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
491 TCPOLEN_SACK_PERBLOCK)));
492
493 for (this_sack = 0; this_sack < opts->num_sack_blocks;
494 ++this_sack) {
495 *ptr++ = htonl(sp[this_sack].start_seq);
496 *ptr++ = htonl(sp[this_sack].end_seq);
497 }
498
499 tp->rx_opt.dsack = 0;
500 }
501
502 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
503 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
504
505 *ptr++ = htonl((TCPOPT_EXP << 24) |
506 ((TCPOLEN_EXP_FASTOPEN_BASE + foc->len) << 16) |
507 TCPOPT_FASTOPEN_MAGIC);
508
509 memcpy(ptr, foc->val, foc->len);
510 if ((foc->len & 3) == 2) {
511 u8 *align = ((u8 *)ptr) + foc->len;
512 align[0] = align[1] = TCPOPT_NOP;
513 }
514 ptr += (foc->len + 3) >> 2;
515 }
516}
517
518/* Compute TCP options for SYN packets. This is not the final
519 * network wire format yet.
520 */
521static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
522 struct tcp_out_options *opts,
523 struct tcp_md5sig_key **md5)
524{
525 struct tcp_sock *tp = tcp_sk(sk);
526 unsigned int remaining = MAX_TCP_OPTION_SPACE;
527 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
528
529#ifdef CONFIG_TCP_MD5SIG
530 *md5 = tp->af_specific->md5_lookup(sk, sk);
531 if (*md5) {
532 opts->options |= OPTION_MD5;
533 remaining -= TCPOLEN_MD5SIG_ALIGNED;
534 }
535#else
536 *md5 = NULL;
537#endif
538
539 /* We always get an MSS option. The option bytes which will be seen in
540 * normal data packets should timestamps be used, must be in the MSS
541 * advertised. But we subtract them from tp->mss_cache so that
542 * calculations in tcp_sendmsg are simpler etc. So account for this
543 * fact here if necessary. If we don't do this correctly, as a
544 * receiver we won't recognize data packets as being full sized when we
545 * should, and thus we won't abide by the delayed ACK rules correctly.
546 * SACKs don't matter, we never delay an ACK when we have any of those
547 * going out. */
548 opts->mss = tcp_advertise_mss(sk);
549 remaining -= TCPOLEN_MSS_ALIGNED;
550
551 if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
552 opts->options |= OPTION_TS;
553 opts->tsval = TCP_SKB_CB(skb)->when + tp->tsoffset;
554 opts->tsecr = tp->rx_opt.ts_recent;
555 remaining -= TCPOLEN_TSTAMP_ALIGNED;
556 }
557 if (likely(sysctl_tcp_window_scaling)) {
558 opts->ws = tp->rx_opt.rcv_wscale;
559 opts->options |= OPTION_WSCALE;
560 remaining -= TCPOLEN_WSCALE_ALIGNED;
561 }
562 if (likely(sysctl_tcp_sack)) {
563 opts->options |= OPTION_SACK_ADVERTISE;
564 if (unlikely(!(OPTION_TS & opts->options)))
565 remaining -= TCPOLEN_SACKPERM_ALIGNED;
566 }
567
568 if (fastopen && fastopen->cookie.len >= 0) {
569 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + fastopen->cookie.len;
570 need = (need + 3) & ~3U; /* Align to 32 bits */
571 if (remaining >= need) {
572 opts->options |= OPTION_FAST_OPEN_COOKIE;
573 opts->fastopen_cookie = &fastopen->cookie;
574 remaining -= need;
575 tp->syn_fastopen = 1;
576 }
577 }
578
579 return MAX_TCP_OPTION_SPACE - remaining;
580}
581
582/* Set up TCP options for SYN-ACKs. */
583static unsigned int tcp_synack_options(struct sock *sk,
584 struct request_sock *req,
585 unsigned int mss, struct sk_buff *skb,
586 struct tcp_out_options *opts,
587 struct tcp_md5sig_key **md5,
588 struct tcp_fastopen_cookie *foc)
589{
590 struct inet_request_sock *ireq = inet_rsk(req);
591 unsigned int remaining = MAX_TCP_OPTION_SPACE;
592
593#ifdef CONFIG_TCP_MD5SIG
594 *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
595 if (*md5) {
596 opts->options |= OPTION_MD5;
597 remaining -= TCPOLEN_MD5SIG_ALIGNED;
598
599 /* We can't fit any SACK blocks in a packet with MD5 + TS
600 * options. There was discussion about disabling SACK
601 * rather than TS in order to fit in better with old,
602 * buggy kernels, but that was deemed to be unnecessary.
603 */
604 ireq->tstamp_ok &= !ireq->sack_ok;
605 }
606#else
607 *md5 = NULL;
608#endif
609
610 /* We always send an MSS option. */
611 opts->mss = mss;
612 remaining -= TCPOLEN_MSS_ALIGNED;
613
614 if (likely(ireq->wscale_ok)) {
615 opts->ws = ireq->rcv_wscale;
616 opts->options |= OPTION_WSCALE;
617 remaining -= TCPOLEN_WSCALE_ALIGNED;
618 }
619 if (likely(ireq->tstamp_ok)) {
620 opts->options |= OPTION_TS;
621 opts->tsval = TCP_SKB_CB(skb)->when;
622 opts->tsecr = req->ts_recent;
623 remaining -= TCPOLEN_TSTAMP_ALIGNED;
624 }
625 if (likely(ireq->sack_ok)) {
626 opts->options |= OPTION_SACK_ADVERTISE;
627 if (unlikely(!ireq->tstamp_ok))
628 remaining -= TCPOLEN_SACKPERM_ALIGNED;
629 }
630 if (foc != NULL) {
631 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
632 need = (need + 3) & ~3U; /* Align to 32 bits */
633 if (remaining >= need) {
634 opts->options |= OPTION_FAST_OPEN_COOKIE;
635 opts->fastopen_cookie = foc;
636 remaining -= need;
637 }
638 }
639
640 return MAX_TCP_OPTION_SPACE - remaining;
641}
642
643/* Compute TCP options for ESTABLISHED sockets. This is not the
644 * final wire format yet.
645 */
646static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
647 struct tcp_out_options *opts,
648 struct tcp_md5sig_key **md5)
649{
650 struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
651 struct tcp_sock *tp = tcp_sk(sk);
652 unsigned int size = 0;
653 unsigned int eff_sacks;
654
655 opts->options = 0;
656
657#ifdef CONFIG_TCP_MD5SIG
658 *md5 = tp->af_specific->md5_lookup(sk, sk);
659 if (unlikely(*md5)) {
660 opts->options |= OPTION_MD5;
661 size += TCPOLEN_MD5SIG_ALIGNED;
662 }
663#else
664 *md5 = NULL;
665#endif
666
667 if (likely(tp->rx_opt.tstamp_ok)) {
668 opts->options |= OPTION_TS;
669 opts->tsval = tcb ? tcb->when + tp->tsoffset : 0;
670 opts->tsecr = tp->rx_opt.ts_recent;
671 size += TCPOLEN_TSTAMP_ALIGNED;
672 }
673
674 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
675 if (unlikely(eff_sacks)) {
676 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
677 opts->num_sack_blocks =
678 min_t(unsigned int, eff_sacks,
679 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
680 TCPOLEN_SACK_PERBLOCK);
681 size += TCPOLEN_SACK_BASE_ALIGNED +
682 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
683 }
684
685 return size;
686}
687
688
689/* TCP SMALL QUEUES (TSQ)
690 *
691 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
692 * to reduce RTT and bufferbloat.
693 * We do this using a special skb destructor (tcp_wfree).
694 *
695 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
696 * needs to be reallocated in a driver.
697 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
698 *
699 * Since transmit from skb destructor is forbidden, we use a tasklet
700 * to process all sockets that eventually need to send more skbs.
701 * We use one tasklet per cpu, with its own queue of sockets.
702 */
703struct tsq_tasklet {
704 struct tasklet_struct tasklet;
705 struct list_head head; /* queue of tcp sockets */
706};
707static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
708
709static void tcp_tsq_handler(struct sock *sk)
710{
711 if ((1 << sk->sk_state) &
712 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
713 TCPF_CLOSE_WAIT | TCPF_LAST_ACK))
714 tcp_write_xmit(sk, tcp_current_mss(sk), tcp_sk(sk)->nonagle,
715 0, GFP_ATOMIC);
716}
717/*
718 * One tasklet per cpu tries to send more skbs.
719 * We run in tasklet context but need to disable irqs when
720 * transferring tsq->head because tcp_wfree() might
721 * interrupt us (non NAPI drivers)
722 */
723static void tcp_tasklet_func(unsigned long data)
724{
725 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
726 LIST_HEAD(list);
727 unsigned long flags;
728 struct list_head *q, *n;
729 struct tcp_sock *tp;
730 struct sock *sk;
731
732 local_irq_save(flags);
733 list_splice_init(&tsq->head, &list);
734 local_irq_restore(flags);
735
736 list_for_each_safe(q, n, &list) {
737 tp = list_entry(q, struct tcp_sock, tsq_node);
738 list_del(&tp->tsq_node);
739
740 sk = (struct sock *)tp;
741 bh_lock_sock(sk);
742
743 if (!sock_owned_by_user(sk)) {
744 tcp_tsq_handler(sk);
745 } else {
746 /* defer the work to tcp_release_cb() */
747 set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
748 }
749 bh_unlock_sock(sk);
750
751 clear_bit(TSQ_QUEUED, &tp->tsq_flags);
752 sk_free(sk);
753 }
754}
755
756#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
757 (1UL << TCP_WRITE_TIMER_DEFERRED) | \
758 (1UL << TCP_DELACK_TIMER_DEFERRED) | \
759 (1UL << TCP_MTU_REDUCED_DEFERRED))
760/**
761 * tcp_release_cb - tcp release_sock() callback
762 * @sk: socket
763 *
764 * called from release_sock() to perform protocol dependent
765 * actions before socket release.
766 */
767void tcp_release_cb(struct sock *sk)
768{
769 struct tcp_sock *tp = tcp_sk(sk);
770 unsigned long flags, nflags;
771
772 /* perform an atomic operation only if at least one flag is set */
773 do {
774 flags = tp->tsq_flags;
775 if (!(flags & TCP_DEFERRED_ALL))
776 return;
777 nflags = flags & ~TCP_DEFERRED_ALL;
778 } while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);
779
780 if (flags & (1UL << TCP_TSQ_DEFERRED))
781 tcp_tsq_handler(sk);
782
783 /* Here begins the tricky part :
784 * We are called from release_sock() with :
785 * 1) BH disabled
786 * 2) sk_lock.slock spinlock held
787 * 3) socket owned by us (sk->sk_lock.owned == 1)
788 *
789 * But following code is meant to be called from BH handlers,
790 * so we should keep BH disabled, but early release socket ownership
791 */
792 sock_release_ownership(sk);
793
794 if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
795 tcp_write_timer_handler(sk);
796 __sock_put(sk);
797 }
798 if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) {
799 tcp_delack_timer_handler(sk);
800 __sock_put(sk);
801 }
802 if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) {
803 sk->sk_prot->mtu_reduced(sk);
804 __sock_put(sk);
805 }
806}
807EXPORT_SYMBOL(tcp_release_cb);
808
809void __init tcp_tasklet_init(void)
810{
811 int i;
812
813 for_each_possible_cpu(i) {
814 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
815
816 INIT_LIST_HEAD(&tsq->head);
817 tasklet_init(&tsq->tasklet,
818 tcp_tasklet_func,
819 (unsigned long)tsq);
820 }
821}
822
823/*
824 * Write buffer destructor automatically called from kfree_skb.
825 * We can't xmit new skbs from this context, as we might already
826 * hold qdisc lock.
827 */
828void tcp_wfree(struct sk_buff *skb)
829{
830 struct sock *sk = skb->sk;
831 struct tcp_sock *tp = tcp_sk(sk);
832
833 if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) &&
834 !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) {
835 unsigned long flags;
836 struct tsq_tasklet *tsq;
837
838 /* Keep a ref on socket.
839 * This last ref will be released in tcp_tasklet_func()
840 */
841 atomic_sub(skb->truesize - 1, &sk->sk_wmem_alloc);
842
843 /* queue this socket to tasklet queue */
844 local_irq_save(flags);
845 tsq = &__get_cpu_var(tsq_tasklet);
846 list_add(&tp->tsq_node, &tsq->head);
847 tasklet_schedule(&tsq->tasklet);
848 local_irq_restore(flags);
849 } else {
850 sock_wfree(skb);
851 }
852}
853
854/* This routine actually transmits TCP packets queued in by
855 * tcp_do_sendmsg(). This is used by both the initial
856 * transmission and possible later retransmissions.
857 * All SKB's seen here are completely headerless. It is our
858 * job to build the TCP header, and pass the packet down to
859 * IP so it can do the same plus pass the packet off to the
860 * device.
861 *
862 * We are working here with either a clone of the original
863 * SKB, or a fresh unique copy made by the retransmit engine.
864 */
865static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
866 gfp_t gfp_mask)
867{
868 const struct inet_connection_sock *icsk = inet_csk(sk);
869 struct inet_sock *inet;
870 struct tcp_sock *tp;
871 struct tcp_skb_cb *tcb;
872 struct tcp_out_options opts;
873 unsigned int tcp_options_size, tcp_header_size;
874 struct tcp_md5sig_key *md5;
875 struct tcphdr *th;
876 int err;
877
878 BUG_ON(!skb || !tcp_skb_pcount(skb));
879
880 if (clone_it) {
881 const struct sk_buff *fclone = skb + 1;
882
883 skb_mstamp_get(&skb->skb_mstamp);
884
885 if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
886 fclone->fclone == SKB_FCLONE_CLONE))
887 NET_INC_STATS(sock_net(sk),
888 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
889
890 if (unlikely(skb_cloned(skb)))
891 skb = pskb_copy(skb, gfp_mask);
892 else
893 skb = skb_clone(skb, gfp_mask);
894 if (unlikely(!skb))
895 return -ENOBUFS;
896 /* Our usage of tstamp should remain private */
897 skb->tstamp.tv64 = 0;
898 }
899
900 inet = inet_sk(sk);
901 tp = tcp_sk(sk);
902 tcb = TCP_SKB_CB(skb);
903 memset(&opts, 0, sizeof(opts));
904
905 if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
906 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
907 else
908 tcp_options_size = tcp_established_options(sk, skb, &opts,
909 &md5);
910 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
911
912 if (tcp_packets_in_flight(tp) == 0)
913 tcp_ca_event(sk, CA_EVENT_TX_START);
914
915 /* if no packet is in qdisc/device queue, then allow XPS to select
916 * another queue.
917 */
918 skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;
919
920 skb_push(skb, tcp_header_size);
921 skb_reset_transport_header(skb);
922
923 skb_orphan(skb);
924 skb->sk = sk;
925 skb->destructor = tcp_wfree;
926 atomic_add(skb->truesize, &sk->sk_wmem_alloc);
927
928 /* Build TCP header and checksum it. */
929 th = tcp_hdr(skb);
930 th->source = inet->inet_sport;
931 th->dest = inet->inet_dport;
932 th->seq = htonl(tcb->seq);
933 th->ack_seq = htonl(tp->rcv_nxt);
934 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
935 tcb->tcp_flags);
936
937 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
938 /* RFC1323: The window in SYN & SYN/ACK segments
939 * is never scaled.
940 */
941 th->window = htons(min(tp->rcv_wnd, 65535U));
942 } else {
943 th->window = htons(tcp_select_window(sk));
944 }
945 th->check = 0;
946 th->urg_ptr = 0;
947
948 /* The urg_mode check is necessary during a below snd_una win probe */
949 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
950 if (before(tp->snd_up, tcb->seq + 0x10000)) {
951 th->urg_ptr = htons(tp->snd_up - tcb->seq);
952 th->urg = 1;
953 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
954 th->urg_ptr = htons(0xFFFF);
955 th->urg = 1;
956 }
957 }
958
959 tcp_options_write((__be32 *)(th + 1), tp, &opts);
960 if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
961 TCP_ECN_send(sk, skb, tcp_header_size);
962
963#ifdef CONFIG_TCP_MD5SIG
964 /* Calculate the MD5 hash, as we have all we need now */
965 if (md5) {
966 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
967 tp->af_specific->calc_md5_hash(opts.hash_location,
968 md5, sk, NULL, skb);
969 }
970#endif
971
972 icsk->icsk_af_ops->send_check(sk, skb);
973
974 if (likely(tcb->tcp_flags & TCPHDR_ACK))
975 tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
976
977 if (skb->len != tcp_header_size)
978 tcp_event_data_sent(tp, sk);
979
980 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
981 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
982 tcp_skb_pcount(skb));
983
984 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
985 if (likely(err <= 0))
986 return err;
987
988 tcp_enter_cwr(sk, 1);
989
990 return net_xmit_eval(err);
991}
992
993/* This routine just queues the buffer for sending.
994 *
995 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
996 * otherwise socket can stall.
997 */
998static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
999{
1000 struct tcp_sock *tp = tcp_sk(sk);
1001
1002 /* Advance write_seq and place onto the write_queue. */
1003 tp->write_seq = TCP_SKB_CB(skb)->end_seq;
1004 skb_header_release(skb);
1005 tcp_add_write_queue_tail(sk, skb);
1006 sk->sk_wmem_queued += skb->truesize;
1007 sk_mem_charge(sk, skb->truesize);
1008}
1009
1010/* Initialize TSO segments for a packet. */
1011static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
1012 unsigned int mss_now)
1013{
1014 struct skb_shared_info *shinfo = skb_shinfo(skb);
1015
1016 /* Make sure we own this skb before messing gso_size/gso_segs */
1017 WARN_ON_ONCE(skb_cloned(skb));
1018
1019 if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1020 /* Avoid the costly divide in the normal
1021 * non-TSO case.
1022 */
1023 shinfo->gso_segs = 1;
1024 shinfo->gso_size = 0;
1025 shinfo->gso_type = 0;
1026 } else {
1027 shinfo->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
1028 shinfo->gso_size = mss_now;
1029 shinfo->gso_type = sk->sk_gso_type;
1030 }
1031}
1032
1033/* When a modification to fackets out becomes necessary, we need to check
1034 * skb is counted to fackets_out or not.
1035 */
1036static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
1037 int decr)
1038{
1039 struct tcp_sock *tp = tcp_sk(sk);
1040
1041 if (!tp->sacked_out || tcp_is_reno(tp))
1042 return;
1043
1044 if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
1045 tp->fackets_out -= decr;
1046}
1047
1048/* Pcount in the middle of the write queue got changed, we need to do various
1049 * tweaks to fix counters
1050 */
1051static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1052{
1053 struct tcp_sock *tp = tcp_sk(sk);
1054
1055 tp->packets_out -= decr;
1056
1057 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1058 tp->sacked_out -= decr;
1059 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1060 tp->retrans_out -= decr;
1061 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1062 tp->lost_out -= decr;
1063
1064 /* Reno case is special. Sigh... */
1065 if (tcp_is_reno(tp) && decr > 0)
1066 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1067
1068 tcp_adjust_fackets_out(sk, skb, decr);
1069
1070 if (tp->lost_skb_hint &&
1071 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1072 (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1073 tp->lost_cnt_hint -= decr;
1074
1075 tcp_verify_left_out(tp);
1076}
1077
1078/* Function to create two new TCP segments. Shrinks the given segment
1079 * to the specified size and appends a new segment with the rest of the
1080 * packet to the list. This won't be called frequently, I hope.
1081 * Remember, these are still headerless SKBs at this point.
1082 */
1083int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1084 unsigned int mss_now)
1085{
1086 struct tcp_sock *tp = tcp_sk(sk);
1087 struct sk_buff *buff;
1088 int nsize, old_factor;
1089 int nlen;
1090 u8 flags;
1091
1092 if (WARN_ON(len > skb->len))
1093 return -EINVAL;
1094
1095 nsize = skb_headlen(skb) - len;
1096 if (nsize < 0)
1097 nsize = 0;
1098
1099 if (skb_unclone(skb, GFP_ATOMIC))
1100 return -ENOMEM;
1101
1102 /* Get a new skb... force flag on. */
1103 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
1104 if (buff == NULL)
1105 return -ENOMEM; /* We'll just try again later. */
1106
1107 sk->sk_wmem_queued += buff->truesize;
1108 sk_mem_charge(sk, buff->truesize);
1109 nlen = skb->len - len - nsize;
1110 buff->truesize += nlen;
1111 skb->truesize -= nlen;
1112
1113 /* Correct the sequence numbers. */
1114 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1115 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1116 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1117
1118 /* PSH and FIN should only be set in the second packet. */
1119 flags = TCP_SKB_CB(skb)->tcp_flags;
1120 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1121 TCP_SKB_CB(buff)->tcp_flags = flags;
1122 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1123
1124 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
1125 /* Copy and checksum data tail into the new buffer. */
1126 buff->csum = csum_partial_copy_nocheck(skb->data + len,
1127 skb_put(buff, nsize),
1128 nsize, 0);
1129
1130 skb_trim(skb, len);
1131
1132 skb->csum = csum_block_sub(skb->csum, buff->csum, len);
1133 } else {
1134 skb->ip_summed = CHECKSUM_PARTIAL;
1135 skb_split(skb, buff, len);
1136 }
1137
1138 buff->ip_summed = skb->ip_summed;
1139
1140 /* Looks stupid, but our code really uses when of
1141 * skbs, which it never sent before. --ANK
1142 */
1143 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
1144 buff->tstamp = skb->tstamp;
1145
1146 old_factor = tcp_skb_pcount(skb);
1147
1148 /* Fix up tso_factor for both original and new SKB. */
1149 tcp_set_skb_tso_segs(sk, skb, mss_now);
1150 tcp_set_skb_tso_segs(sk, buff, mss_now);
1151
1152 /* If this packet has been sent out already, we must
1153 * adjust the various packet counters.
1154 */
1155 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1156 int diff = old_factor - tcp_skb_pcount(skb) -
1157 tcp_skb_pcount(buff);
1158
1159 if (diff)
1160 tcp_adjust_pcount(sk, skb, diff);
1161 }
1162
1163 /* Link BUFF into the send queue. */
1164 skb_header_release(buff);
1165 tcp_insert_write_queue_after(skb, buff, sk);
1166
1167 return 0;
1168}
1169
1170/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1171 * eventually). The difference is that pulled data not copied, but
1172 * immediately discarded.
1173 */
1174static void __pskb_trim_head(struct sk_buff *skb, int len)
1175{
1176 struct skb_shared_info *shinfo;
1177 int i, k, eat;
1178
1179 eat = min_t(int, len, skb_headlen(skb));
1180 if (eat) {
1181 __skb_pull(skb, eat);
1182 len -= eat;
1183 if (!len)
1184 return;
1185 }
1186 eat = len;
1187 k = 0;
1188 shinfo = skb_shinfo(skb);
1189 for (i = 0; i < shinfo->nr_frags; i++) {
1190 int size = skb_frag_size(&shinfo->frags[i]);
1191
1192 if (size <= eat) {
1193 skb_frag_unref(skb, i);
1194 eat -= size;
1195 } else {
1196 shinfo->frags[k] = shinfo->frags[i];
1197 if (eat) {
1198 shinfo->frags[k].page_offset += eat;
1199 skb_frag_size_sub(&shinfo->frags[k], eat);
1200 eat = 0;
1201 }
1202 k++;
1203 }
1204 }
1205 shinfo->nr_frags = k;
1206
1207 skb_reset_tail_pointer(skb);
1208 skb->data_len -= len;
1209 skb->len = skb->data_len;
1210}
1211
1212/* Remove acked data from a packet in the transmit queue. */
1213int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1214{
1215 if (skb_unclone(skb, GFP_ATOMIC))
1216 return -ENOMEM;
1217
1218 __pskb_trim_head(skb, len);
1219
1220 TCP_SKB_CB(skb)->seq += len;
1221 skb->ip_summed = CHECKSUM_PARTIAL;
1222
1223 skb->truesize -= len;
1224 sk->sk_wmem_queued -= len;
1225 sk_mem_uncharge(sk, len);
1226 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1227
1228 /* Any change of skb->len requires recalculation of tso factor. */
1229 if (tcp_skb_pcount(skb) > 1)
1230 tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb));
1231
1232 return 0;
1233}
1234
1235/* Calculate MSS not accounting any TCP options. */
1236static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1237{
1238 const struct tcp_sock *tp = tcp_sk(sk);
1239 const struct inet_connection_sock *icsk = inet_csk(sk);
1240 int mss_now;
1241
1242 /* Calculate base mss without TCP options:
1243 It is MMS_S - sizeof(tcphdr) of rfc1122
1244 */
1245 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1246
1247 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1248 if (icsk->icsk_af_ops->net_frag_header_len) {
1249 const struct dst_entry *dst = __sk_dst_get(sk);
1250
1251 if (dst && dst_allfrag(dst))
1252 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1253 }
1254
1255 /* Clamp it (mss_clamp does not include tcp options) */
1256 if (mss_now > tp->rx_opt.mss_clamp)
1257 mss_now = tp->rx_opt.mss_clamp;
1258
1259 /* Now subtract optional transport overhead */
1260 mss_now -= icsk->icsk_ext_hdr_len;
1261
1262 /* Then reserve room for full set of TCP options and 8 bytes of data */
1263 if (mss_now < 48)
1264 mss_now = 48;
1265 return mss_now;
1266}
1267
1268/* Calculate MSS. Not accounting for SACKs here. */
1269int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1270{
1271 /* Subtract TCP options size, not including SACKs */
1272 return __tcp_mtu_to_mss(sk, pmtu) -
1273 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1274}
1275
1276/* Inverse of above */
1277int tcp_mss_to_mtu(struct sock *sk, int mss)
1278{
1279 const struct tcp_sock *tp = tcp_sk(sk);
1280 const struct inet_connection_sock *icsk = inet_csk(sk);
1281 int mtu;
1282
1283 mtu = mss +
1284 tp->tcp_header_len +
1285 icsk->icsk_ext_hdr_len +
1286 icsk->icsk_af_ops->net_header_len;
1287
1288 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1289 if (icsk->icsk_af_ops->net_frag_header_len) {
1290 const struct dst_entry *dst = __sk_dst_get(sk);
1291
1292 if (dst && dst_allfrag(dst))
1293 mtu += icsk->icsk_af_ops->net_frag_header_len;
1294 }
1295 return mtu;
1296}
1297
1298/* MTU probing init per socket */
1299void tcp_mtup_init(struct sock *sk)
1300{
1301 struct tcp_sock *tp = tcp_sk(sk);
1302 struct inet_connection_sock *icsk = inet_csk(sk);
1303
1304 icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1;
1305 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1306 icsk->icsk_af_ops->net_header_len;
1307 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
1308 icsk->icsk_mtup.probe_size = 0;
1309}
1310EXPORT_SYMBOL(tcp_mtup_init);
1311
1312/* This function synchronize snd mss to current pmtu/exthdr set.
1313
1314 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1315 for TCP options, but includes only bare TCP header.
1316
1317 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1318 It is minimum of user_mss and mss received with SYN.
1319 It also does not include TCP options.
1320
1321 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1322
1323 tp->mss_cache is current effective sending mss, including
1324 all tcp options except for SACKs. It is evaluated,
1325 taking into account current pmtu, but never exceeds
1326 tp->rx_opt.mss_clamp.
1327
1328 NOTE1. rfc1122 clearly states that advertised MSS
1329 DOES NOT include either tcp or ip options.
1330
1331 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1332 are READ ONLY outside this function. --ANK (980731)
1333 */
1334unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1335{
1336 struct tcp_sock *tp = tcp_sk(sk);
1337 struct inet_connection_sock *icsk = inet_csk(sk);
1338 int mss_now;
1339
1340 if (icsk->icsk_mtup.search_high > pmtu)
1341 icsk->icsk_mtup.search_high = pmtu;
1342
1343 mss_now = tcp_mtu_to_mss(sk, pmtu);
1344 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1345
1346 /* And store cached results */
1347 icsk->icsk_pmtu_cookie = pmtu;
1348 if (icsk->icsk_mtup.enabled)
1349 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1350 tp->mss_cache = mss_now;
1351
1352 return mss_now;
1353}
1354EXPORT_SYMBOL(tcp_sync_mss);
1355
1356/* Compute the current effective MSS, taking SACKs and IP options,
1357 * and even PMTU discovery events into account.
1358 */
1359unsigned int tcp_current_mss(struct sock *sk)
1360{
1361 const struct tcp_sock *tp = tcp_sk(sk);
1362 const struct dst_entry *dst = __sk_dst_get(sk);
1363 u32 mss_now;
1364 unsigned int header_len;
1365 struct tcp_out_options opts;
1366 struct tcp_md5sig_key *md5;
1367
1368 mss_now = tp->mss_cache;
1369
1370 if (dst) {
1371 u32 mtu = dst_mtu(dst);
1372 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1373 mss_now = tcp_sync_mss(sk, mtu);
1374 }
1375
1376 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1377 sizeof(struct tcphdr);
1378 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1379 * some common options. If this is an odd packet (because we have SACK
1380 * blocks etc) then our calculated header_len will be different, and
1381 * we have to adjust mss_now correspondingly */
1382 if (header_len != tp->tcp_header_len) {
1383 int delta = (int) header_len - tp->tcp_header_len;
1384 mss_now -= delta;
1385 }
1386
1387 return mss_now;
1388}
1389
1390/* Congestion window validation. (RFC2861) */
1391static void tcp_cwnd_validate(struct sock *sk)
1392{
1393 struct tcp_sock *tp = tcp_sk(sk);
1394
1395 if (tp->packets_out >= tp->snd_cwnd) {
1396 /* Network is feed fully. */
1397 tp->snd_cwnd_used = 0;
1398 tp->snd_cwnd_stamp = tcp_time_stamp;
1399 } else {
1400 /* Network starves. */
1401 if (tp->packets_out > tp->snd_cwnd_used)
1402 tp->snd_cwnd_used = tp->packets_out;
1403
1404 if (sysctl_tcp_slow_start_after_idle &&
1405 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1406 tcp_cwnd_application_limited(sk);
1407 }
1408}
1409
1410/* Minshall's variant of the Nagle send check. */
1411static bool tcp_minshall_check(const struct tcp_sock *tp)
1412{
1413 return after(tp->snd_sml, tp->snd_una) &&
1414 !after(tp->snd_sml, tp->snd_nxt);
1415}
1416
1417/* Update snd_sml if this skb is under mss
1418 * Note that a TSO packet might end with a sub-mss segment
1419 * The test is really :
1420 * if ((skb->len % mss) != 0)
1421 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1422 * But we can avoid doing the divide again given we already have
1423 * skb_pcount = skb->len / mss_now
1424 */
1425static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1426 const struct sk_buff *skb)
1427{
1428 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1429 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1430}
1431
1432/* Return false, if packet can be sent now without violation Nagle's rules:
1433 * 1. It is full sized. (provided by caller in %partial bool)
1434 * 2. Or it contains FIN. (already checked by caller)
1435 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1436 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1437 * With Minshall's modification: all sent small packets are ACKed.
1438 */
1439static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1440 int nonagle)
1441{
1442 return partial &&
1443 ((nonagle & TCP_NAGLE_CORK) ||
1444 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1445}
1446/* Returns the portion of skb which can be sent right away */
1447static unsigned int tcp_mss_split_point(const struct sock *sk,
1448 const struct sk_buff *skb,
1449 unsigned int mss_now,
1450 unsigned int max_segs,
1451 int nonagle)
1452{
1453 const struct tcp_sock *tp = tcp_sk(sk);
1454 u32 partial, needed, window, max_len;
1455
1456 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1457 max_len = mss_now * max_segs;
1458
1459 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1460 return max_len;
1461
1462 needed = min(skb->len, window);
1463
1464 if (max_len <= needed)
1465 return max_len;
1466
1467 partial = needed % mss_now;
1468 /* If last segment is not a full MSS, check if Nagle rules allow us
1469 * to include this last segment in this skb.
1470 * Otherwise, we'll split the skb at last MSS boundary
1471 */
1472 if (tcp_nagle_check(partial != 0, tp, nonagle))
1473 return needed - partial;
1474
1475 return needed;
1476}
1477
1478/* Can at least one segment of SKB be sent right now, according to the
1479 * congestion window rules? If so, return how many segments are allowed.
1480 */
1481static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1482 const struct sk_buff *skb)
1483{
1484 u32 in_flight, cwnd;
1485
1486 /* Don't be strict about the congestion window for the final FIN. */
1487 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1488 tcp_skb_pcount(skb) == 1)
1489 return 1;
1490
1491 in_flight = tcp_packets_in_flight(tp);
1492 cwnd = tp->snd_cwnd;
1493 if (in_flight < cwnd)
1494 return (cwnd - in_flight);
1495
1496 return 0;
1497}
1498
1499/* Initialize TSO state of a skb.
1500 * This must be invoked the first time we consider transmitting
1501 * SKB onto the wire.
1502 */
1503static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb,
1504 unsigned int mss_now)
1505{
1506 int tso_segs = tcp_skb_pcount(skb);
1507
1508 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1509 tcp_set_skb_tso_segs(sk, skb, mss_now);
1510 tso_segs = tcp_skb_pcount(skb);
1511 }
1512 return tso_segs;
1513}
1514
1515
1516/* Return true if the Nagle test allows this packet to be
1517 * sent now.
1518 */
1519static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1520 unsigned int cur_mss, int nonagle)
1521{
1522 /* Nagle rule does not apply to frames, which sit in the middle of the
1523 * write_queue (they have no chances to get new data).
1524 *
1525 * This is implemented in the callers, where they modify the 'nonagle'
1526 * argument based upon the location of SKB in the send queue.
1527 */
1528 if (nonagle & TCP_NAGLE_PUSH)
1529 return true;
1530
1531 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1532 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1533 return true;
1534
1535 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
1536 return true;
1537
1538 return false;
1539}
1540
1541/* Does at least the first segment of SKB fit into the send window? */
1542static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1543 const struct sk_buff *skb,
1544 unsigned int cur_mss)
1545{
1546 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1547
1548 if (skb->len > cur_mss)
1549 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1550
1551 return !after(end_seq, tcp_wnd_end(tp));
1552}
1553
1554/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1555 * should be put on the wire right now. If so, it returns the number of
1556 * packets allowed by the congestion window.
1557 */
1558static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1559 unsigned int cur_mss, int nonagle)
1560{
1561 const struct tcp_sock *tp = tcp_sk(sk);
1562 unsigned int cwnd_quota;
1563
1564 tcp_init_tso_segs(sk, skb, cur_mss);
1565
1566 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
1567 return 0;
1568
1569 cwnd_quota = tcp_cwnd_test(tp, skb);
1570 if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1571 cwnd_quota = 0;
1572
1573 return cwnd_quota;
1574}
1575
1576/* Test if sending is allowed right now. */
1577bool tcp_may_send_now(struct sock *sk)
1578{
1579 const struct tcp_sock *tp = tcp_sk(sk);
1580 struct sk_buff *skb = tcp_send_head(sk);
1581
1582 return skb &&
1583 tcp_snd_test(sk, skb, tcp_current_mss(sk),
1584 (tcp_skb_is_last(sk, skb) ?
1585 tp->nonagle : TCP_NAGLE_PUSH));
1586}
1587
1588/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1589 * which is put after SKB on the list. It is very much like
1590 * tcp_fragment() except that it may make several kinds of assumptions
1591 * in order to speed up the splitting operation. In particular, we
1592 * know that all the data is in scatter-gather pages, and that the
1593 * packet has never been sent out before (and thus is not cloned).
1594 */
1595static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1596 unsigned int mss_now, gfp_t gfp)
1597{
1598 struct sk_buff *buff;
1599 int nlen = skb->len - len;
1600 u8 flags;
1601
1602 /* All of a TSO frame must be composed of paged data. */
1603 if (skb->len != skb->data_len)
1604 return tcp_fragment(sk, skb, len, mss_now);
1605
1606 buff = sk_stream_alloc_skb(sk, 0, gfp);
1607 if (unlikely(buff == NULL))
1608 return -ENOMEM;
1609
1610 sk->sk_wmem_queued += buff->truesize;
1611 sk_mem_charge(sk, buff->truesize);
1612 buff->truesize += nlen;
1613 skb->truesize -= nlen;
1614
1615 /* Correct the sequence numbers. */
1616 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1617 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1618 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1619
1620 /* PSH and FIN should only be set in the second packet. */
1621 flags = TCP_SKB_CB(skb)->tcp_flags;
1622 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1623 TCP_SKB_CB(buff)->tcp_flags = flags;
1624
1625 /* This packet was never sent out yet, so no SACK bits. */
1626 TCP_SKB_CB(buff)->sacked = 0;
1627
1628 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1629 skb_split(skb, buff, len);
1630
1631 /* Fix up tso_factor for both original and new SKB. */
1632 tcp_set_skb_tso_segs(sk, skb, mss_now);
1633 tcp_set_skb_tso_segs(sk, buff, mss_now);
1634
1635 /* Link BUFF into the send queue. */
1636 skb_header_release(buff);
1637 tcp_insert_write_queue_after(skb, buff, sk);
1638
1639 return 0;
1640}
1641
1642/* Try to defer sending, if possible, in order to minimize the amount
1643 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1644 *
1645 * This algorithm is from John Heffner.
1646 */
1647static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1648{
1649 struct tcp_sock *tp = tcp_sk(sk);
1650 const struct inet_connection_sock *icsk = inet_csk(sk);
1651 u32 send_win, cong_win, limit, in_flight;
1652 int win_divisor;
1653
1654 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1655 goto send_now;
1656
1657 if (icsk->icsk_ca_state != TCP_CA_Open)
1658 goto send_now;
1659
1660 /* Defer for less than two clock ticks. */
1661 if (tp->tso_deferred &&
1662 (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1)
1663 goto send_now;
1664
1665 in_flight = tcp_packets_in_flight(tp);
1666
1667 BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1668
1669 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1670
1671 /* From in_flight test above, we know that cwnd > in_flight. */
1672 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1673
1674 limit = min(send_win, cong_win);
1675
1676 /* If a full-sized TSO skb can be sent, do it. */
1677 if (limit >= min_t(unsigned int, sk->sk_gso_max_size,
1678 tp->xmit_size_goal_segs * tp->mss_cache))
1679 goto send_now;
1680
1681 /* Middle in queue won't get any more data, full sendable already? */
1682 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
1683 goto send_now;
1684
1685 win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
1686 if (win_divisor) {
1687 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1688
1689 /* If at least some fraction of a window is available,
1690 * just use it.
1691 */
1692 chunk /= win_divisor;
1693 if (limit >= chunk)
1694 goto send_now;
1695 } else {
1696 /* Different approach, try not to defer past a single
1697 * ACK. Receiver should ACK every other full sized
1698 * frame, so if we have space for more than 3 frames
1699 * then send now.
1700 */
1701 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
1702 goto send_now;
1703 }
1704
1705 /* Ok, it looks like it is advisable to defer.
1706 * Do not rearm the timer if already set to not break TCP ACK clocking.
1707 */
1708 if (!tp->tso_deferred)
1709 tp->tso_deferred = 1 | (jiffies << 1);
1710
1711 return true;
1712
1713send_now:
1714 tp->tso_deferred = 0;
1715 return false;
1716}
1717
1718/* Create a new MTU probe if we are ready.
1719 * MTU probe is regularly attempting to increase the path MTU by
1720 * deliberately sending larger packets. This discovers routing
1721 * changes resulting in larger path MTUs.
1722 *
1723 * Returns 0 if we should wait to probe (no cwnd available),
1724 * 1 if a probe was sent,
1725 * -1 otherwise
1726 */
1727static int tcp_mtu_probe(struct sock *sk)
1728{
1729 struct tcp_sock *tp = tcp_sk(sk);
1730 struct inet_connection_sock *icsk = inet_csk(sk);
1731 struct sk_buff *skb, *nskb, *next;
1732 int len;
1733 int probe_size;
1734 int size_needed;
1735 int copy;
1736 int mss_now;
1737
1738 /* Not currently probing/verifying,
1739 * not in recovery,
1740 * have enough cwnd, and
1741 * not SACKing (the variable headers throw things off) */
1742 if (!icsk->icsk_mtup.enabled ||
1743 icsk->icsk_mtup.probe_size ||
1744 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
1745 tp->snd_cwnd < 11 ||
1746 tp->rx_opt.num_sacks || tp->rx_opt.dsack)
1747 return -1;
1748
1749 /* Very simple search strategy: just double the MSS. */
1750 mss_now = tcp_current_mss(sk);
1751 probe_size = 2 * tp->mss_cache;
1752 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1753 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
1754 /* TODO: set timer for probe_converge_event */
1755 return -1;
1756 }
1757
1758 /* Have enough data in the send queue to probe? */
1759 if (tp->write_seq - tp->snd_nxt < size_needed)
1760 return -1;
1761
1762 if (tp->snd_wnd < size_needed)
1763 return -1;
1764 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1765 return 0;
1766
1767 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1768 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
1769 if (!tcp_packets_in_flight(tp))
1770 return -1;
1771 else
1772 return 0;
1773 }
1774
1775 /* We're allowed to probe. Build it now. */
1776 if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL)
1777 return -1;
1778 sk->sk_wmem_queued += nskb->truesize;
1779 sk_mem_charge(sk, nskb->truesize);
1780
1781 skb = tcp_send_head(sk);
1782
1783 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
1784 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
1785 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
1786 TCP_SKB_CB(nskb)->sacked = 0;
1787 nskb->csum = 0;
1788 nskb->ip_summed = skb->ip_summed;
1789
1790 tcp_insert_write_queue_before(nskb, skb, sk);
1791
1792 len = 0;
1793 tcp_for_write_queue_from_safe(skb, next, sk) {
1794 copy = min_t(int, skb->len, probe_size - len);
1795 if (nskb->ip_summed)
1796 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
1797 else
1798 nskb->csum = skb_copy_and_csum_bits(skb, 0,
1799 skb_put(nskb, copy),
1800 copy, nskb->csum);
1801
1802 if (skb->len <= copy) {
1803 /* We've eaten all the data from this skb.
1804 * Throw it away. */
1805 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1806 tcp_unlink_write_queue(skb, sk);
1807 sk_wmem_free_skb(sk, skb);
1808 } else {
1809 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
1810 ~(TCPHDR_FIN|TCPHDR_PSH);
1811 if (!skb_shinfo(skb)->nr_frags) {
1812 skb_pull(skb, copy);
1813 if (skb->ip_summed != CHECKSUM_PARTIAL)
1814 skb->csum = csum_partial(skb->data,
1815 skb->len, 0);
1816 } else {
1817 __pskb_trim_head(skb, copy);
1818 tcp_set_skb_tso_segs(sk, skb, mss_now);
1819 }
1820 TCP_SKB_CB(skb)->seq += copy;
1821 }
1822
1823 len += copy;
1824
1825 if (len >= probe_size)
1826 break;
1827 }
1828 tcp_init_tso_segs(sk, nskb, nskb->len);
1829
1830 /* We're ready to send. If this fails, the probe will
1831 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1832 TCP_SKB_CB(nskb)->when = tcp_time_stamp;
1833 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
1834 /* Decrement cwnd here because we are sending
1835 * effectively two packets. */
1836 tp->snd_cwnd--;
1837 tcp_event_new_data_sent(sk, nskb);
1838
1839 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1840 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
1841 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
1842
1843 return 1;
1844 }
1845
1846 return -1;
1847}
1848
1849/* This routine writes packets to the network. It advances the
1850 * send_head. This happens as incoming acks open up the remote
1851 * window for us.
1852 *
1853 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1854 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1855 * account rare use of URG, this is not a big flaw.
1856 *
1857 * Send at most one packet when push_one > 0. Temporarily ignore
1858 * cwnd limit to force at most one packet out when push_one == 2.
1859
1860 * Returns true, if no segments are in flight and we have queued segments,
1861 * but cannot send anything now because of SWS or another problem.
1862 */
1863static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
1864 int push_one, gfp_t gfp)
1865{
1866 struct tcp_sock *tp = tcp_sk(sk);
1867 struct sk_buff *skb;
1868 unsigned int tso_segs, sent_pkts;
1869 int cwnd_quota;
1870 int result;
1871
1872 sent_pkts = 0;
1873
1874 if (!push_one) {
1875 /* Do MTU probing. */
1876 result = tcp_mtu_probe(sk);
1877 if (!result) {
1878 return false;
1879 } else if (result > 0) {
1880 sent_pkts = 1;
1881 }
1882 }
1883
1884 while ((skb = tcp_send_head(sk))) {
1885 unsigned int limit;
1886
1887 tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1888 BUG_ON(!tso_segs);
1889
1890 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE)
1891 goto repair; /* Skip network transmission */
1892
1893 cwnd_quota = tcp_cwnd_test(tp, skb);
1894 if (!cwnd_quota) {
1895 if (push_one == 2)
1896 /* Force out a loss probe pkt. */
1897 cwnd_quota = 1;
1898 else
1899 break;
1900 }
1901
1902 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
1903 break;
1904
1905 if (tso_segs == 1) {
1906 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
1907 (tcp_skb_is_last(sk, skb) ?
1908 nonagle : TCP_NAGLE_PUSH))))
1909 break;
1910 } else {
1911 if (!push_one && tcp_tso_should_defer(sk, skb))
1912 break;
1913 }
1914
1915 /* TCP Small Queues :
1916 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
1917 * This allows for :
1918 * - better RTT estimation and ACK scheduling
1919 * - faster recovery
1920 * - high rates
1921 * Alas, some drivers / subsystems require a fair amount
1922 * of queued bytes to ensure line rate.
1923 * One example is wifi aggregation (802.11 AMPDU)
1924 */
1925 limit = max_t(unsigned int, sysctl_tcp_limit_output_bytes,
1926 sk->sk_pacing_rate >> 10);
1927
1928 if (atomic_read(&sk->sk_wmem_alloc) > limit) {
1929 set_bit(TSQ_THROTTLED, &tp->tsq_flags);
1930 /* It is possible TX completion already happened
1931 * before we set TSQ_THROTTLED, so we must
1932 * test again the condition.
1933 * We abuse smp_mb__after_clear_bit() because
1934 * there is no smp_mb__after_set_bit() yet
1935 */
1936 smp_mb__after_clear_bit();
1937 if (atomic_read(&sk->sk_wmem_alloc) > limit)
1938 break;
1939 }
1940
1941 limit = mss_now;
1942 if (tso_segs > 1 && !tcp_urg_mode(tp))
1943 limit = tcp_mss_split_point(sk, skb, mss_now,
1944 min_t(unsigned int,
1945 cwnd_quota,
1946 sk->sk_gso_max_segs),
1947 nonagle);
1948
1949 if (skb->len > limit &&
1950 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
1951 break;
1952
1953 TCP_SKB_CB(skb)->when = tcp_time_stamp;
1954
1955 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
1956 break;
1957
1958repair:
1959 /* Advance the send_head. This one is sent out.
1960 * This call will increment packets_out.
1961 */
1962 tcp_event_new_data_sent(sk, skb);
1963
1964 tcp_minshall_update(tp, mss_now, skb);
1965 sent_pkts += tcp_skb_pcount(skb);
1966
1967 if (push_one)
1968 break;
1969 }
1970
1971 if (likely(sent_pkts)) {
1972 if (tcp_in_cwnd_reduction(sk))
1973 tp->prr_out += sent_pkts;
1974
1975 /* Send one loss probe per tail loss episode. */
1976 if (push_one != 2)
1977 tcp_schedule_loss_probe(sk);
1978 tcp_cwnd_validate(sk);
1979 return false;
1980 }
1981 return (push_one == 2) || (!tp->packets_out && tcp_send_head(sk));
1982}
1983
1984bool tcp_schedule_loss_probe(struct sock *sk)
1985{
1986 struct inet_connection_sock *icsk = inet_csk(sk);
1987 struct tcp_sock *tp = tcp_sk(sk);
1988 u32 timeout, tlp_time_stamp, rto_time_stamp;
1989 u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
1990
1991 if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
1992 return false;
1993 /* No consecutive loss probes. */
1994 if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
1995 tcp_rearm_rto(sk);
1996 return false;
1997 }
1998 /* Don't do any loss probe on a Fast Open connection before 3WHS
1999 * finishes.
2000 */
2001 if (sk->sk_state == TCP_SYN_RECV)
2002 return false;
2003
2004 /* TLP is only scheduled when next timer event is RTO. */
2005 if (icsk->icsk_pending != ICSK_TIME_RETRANS)
2006 return false;
2007
2008 /* Schedule a loss probe in 2*RTT for SACK capable connections
2009 * in Open state, that are either limited by cwnd or application.
2010 */
2011 if (sysctl_tcp_early_retrans < 3 || !tp->srtt_us || !tp->packets_out ||
2012 !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
2013 return false;
2014
2015 if ((tp->snd_cwnd > tcp_packets_in_flight(tp)) &&
2016 tcp_send_head(sk))
2017 return false;
2018
2019 /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2020 * for delayed ack when there's one outstanding packet.
2021 */
2022 timeout = rtt << 1;
2023 if (tp->packets_out == 1)
2024 timeout = max_t(u32, timeout,
2025 (rtt + (rtt >> 1) + TCP_DELACK_MAX));
2026 timeout = max_t(u32, timeout, msecs_to_jiffies(10));
2027
2028 /* If RTO is shorter, just schedule TLP in its place. */
2029 tlp_time_stamp = tcp_time_stamp + timeout;
2030 rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout;
2031 if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) {
2032 s32 delta = rto_time_stamp - tcp_time_stamp;
2033 if (delta > 0)
2034 timeout = delta;
2035 }
2036
2037 inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
2038 TCP_RTO_MAX);
2039 return true;
2040}
2041
2042/* When probe timeout (PTO) fires, send a new segment if one exists, else
2043 * retransmit the last segment.
2044 */
2045void tcp_send_loss_probe(struct sock *sk)
2046{
2047 struct tcp_sock *tp = tcp_sk(sk);
2048 struct sk_buff *skb;
2049 int pcount;
2050 int mss = tcp_current_mss(sk);
2051 int err = -1;
2052
2053 if (tcp_send_head(sk) != NULL) {
2054 err = tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2055 goto rearm_timer;
2056 }
2057
2058 /* At most one outstanding TLP retransmission. */
2059 if (tp->tlp_high_seq)
2060 goto rearm_timer;
2061
2062 /* Retransmit last segment. */
2063 skb = tcp_write_queue_tail(sk);
2064 if (WARN_ON(!skb))
2065 goto rearm_timer;
2066
2067 pcount = tcp_skb_pcount(skb);
2068 if (WARN_ON(!pcount))
2069 goto rearm_timer;
2070
2071 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2072 if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss)))
2073 goto rearm_timer;
2074 skb = tcp_write_queue_tail(sk);
2075 }
2076
2077 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2078 goto rearm_timer;
2079
2080 /* Probe with zero data doesn't trigger fast recovery. */
2081 if (skb->len > 0)
2082 err = __tcp_retransmit_skb(sk, skb);
2083
2084 /* Record snd_nxt for loss detection. */
2085 if (likely(!err))
2086 tp->tlp_high_seq = tp->snd_nxt;
2087
2088rearm_timer:
2089 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2090 inet_csk(sk)->icsk_rto,
2091 TCP_RTO_MAX);
2092
2093 if (likely(!err))
2094 NET_INC_STATS_BH(sock_net(sk),
2095 LINUX_MIB_TCPLOSSPROBES);
2096}
2097
2098/* Push out any pending frames which were held back due to
2099 * TCP_CORK or attempt at coalescing tiny packets.
2100 * The socket must be locked by the caller.
2101 */
2102void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2103 int nonagle)
2104{
2105 /* If we are closed, the bytes will have to remain here.
2106 * In time closedown will finish, we empty the write queue and
2107 * all will be happy.
2108 */
2109 if (unlikely(sk->sk_state == TCP_CLOSE))
2110 return;
2111
2112 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2113 sk_gfp_atomic(sk, GFP_ATOMIC)))
2114 tcp_check_probe_timer(sk);
2115}
2116
2117/* Send _single_ skb sitting at the send head. This function requires
2118 * true push pending frames to setup probe timer etc.
2119 */
2120void tcp_push_one(struct sock *sk, unsigned int mss_now)
2121{
2122 struct sk_buff *skb = tcp_send_head(sk);
2123
2124 BUG_ON(!skb || skb->len < mss_now);
2125
2126 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2127}
2128
2129/* This function returns the amount that we can raise the
2130 * usable window based on the following constraints
2131 *
2132 * 1. The window can never be shrunk once it is offered (RFC 793)
2133 * 2. We limit memory per socket
2134 *
2135 * RFC 1122:
2136 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2137 * RECV.NEXT + RCV.WIN fixed until:
2138 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2139 *
2140 * i.e. don't raise the right edge of the window until you can raise
2141 * it at least MSS bytes.
2142 *
2143 * Unfortunately, the recommended algorithm breaks header prediction,
2144 * since header prediction assumes th->window stays fixed.
2145 *
2146 * Strictly speaking, keeping th->window fixed violates the receiver
2147 * side SWS prevention criteria. The problem is that under this rule
2148 * a stream of single byte packets will cause the right side of the
2149 * window to always advance by a single byte.
2150 *
2151 * Of course, if the sender implements sender side SWS prevention
2152 * then this will not be a problem.
2153 *
2154 * BSD seems to make the following compromise:
2155 *
2156 * If the free space is less than the 1/4 of the maximum
2157 * space available and the free space is less than 1/2 mss,
2158 * then set the window to 0.
2159 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2160 * Otherwise, just prevent the window from shrinking
2161 * and from being larger than the largest representable value.
2162 *
2163 * This prevents incremental opening of the window in the regime
2164 * where TCP is limited by the speed of the reader side taking
2165 * data out of the TCP receive queue. It does nothing about
2166 * those cases where the window is constrained on the sender side
2167 * because the pipeline is full.
2168 *
2169 * BSD also seems to "accidentally" limit itself to windows that are a
2170 * multiple of MSS, at least until the free space gets quite small.
2171 * This would appear to be a side effect of the mbuf implementation.
2172 * Combining these two algorithms results in the observed behavior
2173 * of having a fixed window size at almost all times.
2174 *
2175 * Below we obtain similar behavior by forcing the offered window to
2176 * a multiple of the mss when it is feasible to do so.
2177 *
2178 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2179 * Regular options like TIMESTAMP are taken into account.
2180 */
2181u32 __tcp_select_window(struct sock *sk)
2182{
2183 struct inet_connection_sock *icsk = inet_csk(sk);
2184 struct tcp_sock *tp = tcp_sk(sk);
2185 /* MSS for the peer's data. Previous versions used mss_clamp
2186 * here. I don't know if the value based on our guesses
2187 * of peer's MSS is better for the performance. It's more correct
2188 * but may be worse for the performance because of rcv_mss
2189 * fluctuations. --SAW 1998/11/1
2190 */
2191 int mss = icsk->icsk_ack.rcv_mss;
2192 int free_space = tcp_space(sk);
2193 int allowed_space = tcp_full_space(sk);
2194 int full_space = min_t(int, tp->window_clamp, allowed_space);
2195 int window;
2196
2197 if (mss > full_space)
2198 mss = full_space;
2199
2200 if (free_space < (full_space >> 1)) {
2201 icsk->icsk_ack.quick = 0;
2202
2203 if (sk_under_memory_pressure(sk))
2204 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2205 4U * tp->advmss);
2206
2207 /* free_space might become our new window, make sure we don't
2208 * increase it due to wscale.
2209 */
2210 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2211
2212 /* if free space is less than mss estimate, or is below 1/16th
2213 * of the maximum allowed, try to move to zero-window, else
2214 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2215 * new incoming data is dropped due to memory limits.
2216 * With large window, mss test triggers way too late in order
2217 * to announce zero window in time before rmem limit kicks in.
2218 */
2219 if (free_space < (allowed_space >> 4) || free_space < mss)
2220 return 0;
2221 }
2222
2223 if (free_space > tp->rcv_ssthresh)
2224 free_space = tp->rcv_ssthresh;
2225
2226 /* Don't do rounding if we are using window scaling, since the
2227 * scaled window will not line up with the MSS boundary anyway.
2228 */
2229 window = tp->rcv_wnd;
2230 if (tp->rx_opt.rcv_wscale) {
2231 window = free_space;
2232
2233 /* Advertise enough space so that it won't get scaled away.
2234 * Import case: prevent zero window announcement if
2235 * 1<<rcv_wscale > mss.
2236 */
2237 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
2238 window = (((window >> tp->rx_opt.rcv_wscale) + 1)
2239 << tp->rx_opt.rcv_wscale);
2240 } else {
2241 /* Get the largest window that is a nice multiple of mss.
2242 * Window clamp already applied above.
2243 * If our current window offering is within 1 mss of the
2244 * free space we just keep it. This prevents the divide
2245 * and multiply from happening most of the time.
2246 * We also don't do any window rounding when the free space
2247 * is too small.
2248 */
2249 if (window <= free_space - mss || window > free_space)
2250 window = (free_space / mss) * mss;
2251 else if (mss == full_space &&
2252 free_space > window + (full_space >> 1))
2253 window = free_space;
2254 }
2255
2256 return window;
2257}
2258
2259/* Collapses two adjacent SKB's during retransmission. */
2260static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
2261{
2262 struct tcp_sock *tp = tcp_sk(sk);
2263 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2264 int skb_size, next_skb_size;
2265
2266 skb_size = skb->len;
2267 next_skb_size = next_skb->len;
2268
2269 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2270
2271 tcp_highest_sack_combine(sk, next_skb, skb);
2272
2273 tcp_unlink_write_queue(next_skb, sk);
2274
2275 skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
2276 next_skb_size);
2277
2278 if (next_skb->ip_summed == CHECKSUM_PARTIAL)
2279 skb->ip_summed = CHECKSUM_PARTIAL;
2280
2281 if (skb->ip_summed != CHECKSUM_PARTIAL)
2282 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
2283
2284 /* Update sequence range on original skb. */
2285 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2286
2287 /* Merge over control information. This moves PSH/FIN etc. over */
2288 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2289
2290 /* All done, get rid of second SKB and account for it so
2291 * packet counting does not break.
2292 */
2293 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2294
2295 /* changed transmit queue under us so clear hints */
2296 tcp_clear_retrans_hints_partial(tp);
2297 if (next_skb == tp->retransmit_skb_hint)
2298 tp->retransmit_skb_hint = skb;
2299
2300 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2301
2302 sk_wmem_free_skb(sk, next_skb);
2303}
2304
2305/* Check if coalescing SKBs is legal. */
2306static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2307{
2308 if (tcp_skb_pcount(skb) > 1)
2309 return false;
2310 /* TODO: SACK collapsing could be used to remove this condition */
2311 if (skb_shinfo(skb)->nr_frags != 0)
2312 return false;
2313 if (skb_cloned(skb))
2314 return false;
2315 if (skb == tcp_send_head(sk))
2316 return false;
2317 /* Some heurestics for collapsing over SACK'd could be invented */
2318 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2319 return false;
2320
2321 return true;
2322}
2323
2324/* Collapse packets in the retransmit queue to make to create
2325 * less packets on the wire. This is only done on retransmission.
2326 */
2327static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2328 int space)
2329{
2330 struct tcp_sock *tp = tcp_sk(sk);
2331 struct sk_buff *skb = to, *tmp;
2332 bool first = true;
2333
2334 if (!sysctl_tcp_retrans_collapse)
2335 return;
2336 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2337 return;
2338
2339 tcp_for_write_queue_from_safe(skb, tmp, sk) {
2340 if (!tcp_can_collapse(sk, skb))
2341 break;
2342
2343 space -= skb->len;
2344
2345 if (first) {
2346 first = false;
2347 continue;
2348 }
2349
2350 if (space < 0)
2351 break;
2352 /* Punt if not enough space exists in the first SKB for
2353 * the data in the second
2354 */
2355 if (skb->len > skb_availroom(to))
2356 break;
2357
2358 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2359 break;
2360
2361 tcp_collapse_retrans(sk, to);
2362 }
2363}
2364
2365/* This retransmits one SKB. Policy decisions and retransmit queue
2366 * state updates are done by the caller. Returns non-zero if an
2367 * error occurred which prevented the send.
2368 */
2369int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2370{
2371 struct tcp_sock *tp = tcp_sk(sk);
2372 struct inet_connection_sock *icsk = inet_csk(sk);
2373 unsigned int cur_mss;
2374 int err;
2375
2376 /* Inconslusive MTU probe */
2377 if (icsk->icsk_mtup.probe_size) {
2378 icsk->icsk_mtup.probe_size = 0;
2379 }
2380
2381 /* Do not sent more than we queued. 1/4 is reserved for possible
2382 * copying overhead: fragmentation, tunneling, mangling etc.
2383 */
2384 if (atomic_read(&sk->sk_wmem_alloc) >
2385 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
2386 return -EAGAIN;
2387
2388 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2389 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
2390 BUG();
2391 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
2392 return -ENOMEM;
2393 }
2394
2395 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
2396 return -EHOSTUNREACH; /* Routing failure or similar. */
2397
2398 cur_mss = tcp_current_mss(sk);
2399
2400 /* If receiver has shrunk his window, and skb is out of
2401 * new window, do not retransmit it. The exception is the
2402 * case, when window is shrunk to zero. In this case
2403 * our retransmit serves as a zero window probe.
2404 */
2405 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
2406 TCP_SKB_CB(skb)->seq != tp->snd_una)
2407 return -EAGAIN;
2408
2409 if (skb->len > cur_mss) {
2410 if (tcp_fragment(sk, skb, cur_mss, cur_mss))
2411 return -ENOMEM; /* We'll try again later. */
2412 } else {
2413 int oldpcount = tcp_skb_pcount(skb);
2414
2415 if (unlikely(oldpcount > 1)) {
2416 if (skb_unclone(skb, GFP_ATOMIC))
2417 return -ENOMEM;
2418 tcp_init_tso_segs(sk, skb, cur_mss);
2419 tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
2420 }
2421 }
2422
2423 tcp_retrans_try_collapse(sk, skb, cur_mss);
2424
2425 /* Make a copy, if the first transmission SKB clone we made
2426 * is still in somebody's hands, else make a clone.
2427 */
2428 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2429
2430 /* make sure skb->data is aligned on arches that require it
2431 * and check if ack-trimming & collapsing extended the headroom
2432 * beyond what csum_start can cover.
2433 */
2434 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
2435 skb_headroom(skb) >= 0xFFFF)) {
2436 struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
2437 GFP_ATOMIC);
2438 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
2439 -ENOBUFS;
2440 } else {
2441 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2442 }
2443
2444 if (likely(!err)) {
2445 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2446 /* Update global TCP statistics. */
2447 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
2448 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2449 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2450 tp->total_retrans++;
2451 }
2452 return err;
2453}
2454
2455int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2456{
2457 struct tcp_sock *tp = tcp_sk(sk);
2458 int err = __tcp_retransmit_skb(sk, skb);
2459
2460 if (err == 0) {
2461#if FASTRETRANS_DEBUG > 0
2462 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2463 net_dbg_ratelimited("retrans_out leaked\n");
2464 }
2465#endif
2466 if (!tp->retrans_out)
2467 tp->lost_retrans_low = tp->snd_nxt;
2468 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
2469 tp->retrans_out += tcp_skb_pcount(skb);
2470
2471 /* Save stamp of the first retransmit. */
2472 if (!tp->retrans_stamp)
2473 tp->retrans_stamp = TCP_SKB_CB(skb)->when;
2474
2475 tp->undo_retrans += tcp_skb_pcount(skb);
2476
2477 /* snd_nxt is stored to detect loss of retransmitted segment,
2478 * see tcp_input.c tcp_sacktag_write_queue().
2479 */
2480 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
2481 } else {
2482 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2483 }
2484 return err;
2485}
2486
2487/* Check if we forward retransmits are possible in the current
2488 * window/congestion state.
2489 */
2490static bool tcp_can_forward_retransmit(struct sock *sk)
2491{
2492 const struct inet_connection_sock *icsk = inet_csk(sk);
2493 const struct tcp_sock *tp = tcp_sk(sk);
2494
2495 /* Forward retransmissions are possible only during Recovery. */
2496 if (icsk->icsk_ca_state != TCP_CA_Recovery)
2497 return false;
2498
2499 /* No forward retransmissions in Reno are possible. */
2500 if (tcp_is_reno(tp))
2501 return false;
2502
2503 /* Yeah, we have to make difficult choice between forward transmission
2504 * and retransmission... Both ways have their merits...
2505 *
2506 * For now we do not retransmit anything, while we have some new
2507 * segments to send. In the other cases, follow rule 3 for
2508 * NextSeg() specified in RFC3517.
2509 */
2510
2511 if (tcp_may_send_now(sk))
2512 return false;
2513
2514 return true;
2515}
2516
2517/* This gets called after a retransmit timeout, and the initially
2518 * retransmitted data is acknowledged. It tries to continue
2519 * resending the rest of the retransmit queue, until either
2520 * we've sent it all or the congestion window limit is reached.
2521 * If doing SACK, the first ACK which comes back for a timeout
2522 * based retransmit packet might feed us FACK information again.
2523 * If so, we use it to avoid unnecessarily retransmissions.
2524 */
2525void tcp_xmit_retransmit_queue(struct sock *sk)
2526{
2527 const struct inet_connection_sock *icsk = inet_csk(sk);
2528 struct tcp_sock *tp = tcp_sk(sk);
2529 struct sk_buff *skb;
2530 struct sk_buff *hole = NULL;
2531 u32 last_lost;
2532 int mib_idx;
2533 int fwd_rexmitting = 0;
2534
2535 if (!tp->packets_out)
2536 return;
2537
2538 if (!tp->lost_out)
2539 tp->retransmit_high = tp->snd_una;
2540
2541 if (tp->retransmit_skb_hint) {
2542 skb = tp->retransmit_skb_hint;
2543 last_lost = TCP_SKB_CB(skb)->end_seq;
2544 if (after(last_lost, tp->retransmit_high))
2545 last_lost = tp->retransmit_high;
2546 } else {
2547 skb = tcp_write_queue_head(sk);
2548 last_lost = tp->snd_una;
2549 }
2550
2551 tcp_for_write_queue_from(skb, sk) {
2552 __u8 sacked = TCP_SKB_CB(skb)->sacked;
2553
2554 if (skb == tcp_send_head(sk))
2555 break;
2556 /* we could do better than to assign each time */
2557 if (hole == NULL)
2558 tp->retransmit_skb_hint = skb;
2559
2560 /* Assume this retransmit will generate
2561 * only one packet for congestion window
2562 * calculation purposes. This works because
2563 * tcp_retransmit_skb() will chop up the
2564 * packet to be MSS sized and all the
2565 * packet counting works out.
2566 */
2567 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
2568 return;
2569
2570 if (fwd_rexmitting) {
2571begin_fwd:
2572 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
2573 break;
2574 mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2575
2576 } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2577 tp->retransmit_high = last_lost;
2578 if (!tcp_can_forward_retransmit(sk))
2579 break;
2580 /* Backtrack if necessary to non-L'ed skb */
2581 if (hole != NULL) {
2582 skb = hole;
2583 hole = NULL;
2584 }
2585 fwd_rexmitting = 1;
2586 goto begin_fwd;
2587
2588 } else if (!(sacked & TCPCB_LOST)) {
2589 if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2590 hole = skb;
2591 continue;
2592
2593 } else {
2594 last_lost = TCP_SKB_CB(skb)->end_seq;
2595 if (icsk->icsk_ca_state != TCP_CA_Loss)
2596 mib_idx = LINUX_MIB_TCPFASTRETRANS;
2597 else
2598 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
2599 }
2600
2601 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
2602 continue;
2603
2604 if (tcp_retransmit_skb(sk, skb))
2605 return;
2606
2607 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2608
2609 if (tcp_in_cwnd_reduction(sk))
2610 tp->prr_out += tcp_skb_pcount(skb);
2611
2612 if (skb == tcp_write_queue_head(sk))
2613 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2614 inet_csk(sk)->icsk_rto,
2615 TCP_RTO_MAX);
2616 }
2617}
2618
2619/* Send a fin. The caller locks the socket for us. This cannot be
2620 * allowed to fail queueing a FIN frame under any circumstances.
2621 */
2622void tcp_send_fin(struct sock *sk)
2623{
2624 struct tcp_sock *tp = tcp_sk(sk);
2625 struct sk_buff *skb = tcp_write_queue_tail(sk);
2626 int mss_now;
2627
2628 /* Optimization, tack on the FIN if we have a queue of
2629 * unsent frames. But be careful about outgoing SACKS
2630 * and IP options.
2631 */
2632 mss_now = tcp_current_mss(sk);
2633
2634 if (tcp_send_head(sk) != NULL) {
2635 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_FIN;
2636 TCP_SKB_CB(skb)->end_seq++;
2637 tp->write_seq++;
2638 } else {
2639 /* Socket is locked, keep trying until memory is available. */
2640 for (;;) {
2641 skb = alloc_skb_fclone(MAX_TCP_HEADER,
2642 sk->sk_allocation);
2643 if (skb)
2644 break;
2645 yield();
2646 }
2647
2648 /* Reserve space for headers and prepare control bits. */
2649 skb_reserve(skb, MAX_TCP_HEADER);
2650 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2651 tcp_init_nondata_skb(skb, tp->write_seq,
2652 TCPHDR_ACK | TCPHDR_FIN);
2653 tcp_queue_skb(sk, skb);
2654 }
2655 __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
2656}
2657
2658/* We get here when a process closes a file descriptor (either due to
2659 * an explicit close() or as a byproduct of exit()'ing) and there
2660 * was unread data in the receive queue. This behavior is recommended
2661 * by RFC 2525, section 2.17. -DaveM
2662 */
2663void tcp_send_active_reset(struct sock *sk, gfp_t priority)
2664{
2665 struct sk_buff *skb;
2666
2667 /* NOTE: No TCP options attached and we never retransmit this. */
2668 skb = alloc_skb(MAX_TCP_HEADER, priority);
2669 if (!skb) {
2670 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2671 return;
2672 }
2673
2674 /* Reserve space for headers and prepare control bits. */
2675 skb_reserve(skb, MAX_TCP_HEADER);
2676 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
2677 TCPHDR_ACK | TCPHDR_RST);
2678 /* Send it off. */
2679 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2680 if (tcp_transmit_skb(sk, skb, 0, priority))
2681 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2682
2683 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
2684}
2685
2686/* Send a crossed SYN-ACK during socket establishment.
2687 * WARNING: This routine must only be called when we have already sent
2688 * a SYN packet that crossed the incoming SYN that caused this routine
2689 * to get called. If this assumption fails then the initial rcv_wnd
2690 * and rcv_wscale values will not be correct.
2691 */
2692int tcp_send_synack(struct sock *sk)
2693{
2694 struct sk_buff *skb;
2695
2696 skb = tcp_write_queue_head(sk);
2697 if (skb == NULL || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
2698 pr_debug("%s: wrong queue state\n", __func__);
2699 return -EFAULT;
2700 }
2701 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
2702 if (skb_cloned(skb)) {
2703 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
2704 if (nskb == NULL)
2705 return -ENOMEM;
2706 tcp_unlink_write_queue(skb, sk);
2707 skb_header_release(nskb);
2708 __tcp_add_write_queue_head(sk, nskb);
2709 sk_wmem_free_skb(sk, skb);
2710 sk->sk_wmem_queued += nskb->truesize;
2711 sk_mem_charge(sk, nskb->truesize);
2712 skb = nskb;
2713 }
2714
2715 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
2716 TCP_ECN_send_synack(tcp_sk(sk), skb);
2717 }
2718 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2719 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2720}
2721
2722/**
2723 * tcp_make_synack - Prepare a SYN-ACK.
2724 * sk: listener socket
2725 * dst: dst entry attached to the SYNACK
2726 * req: request_sock pointer
2727 *
2728 * Allocate one skb and build a SYNACK packet.
2729 * @dst is consumed : Caller should not use it again.
2730 */
2731struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2732 struct request_sock *req,
2733 struct tcp_fastopen_cookie *foc)
2734{
2735 struct tcp_out_options opts;
2736 struct inet_request_sock *ireq = inet_rsk(req);
2737 struct tcp_sock *tp = tcp_sk(sk);
2738 struct tcphdr *th;
2739 struct sk_buff *skb;
2740 struct tcp_md5sig_key *md5;
2741 int tcp_header_size;
2742 int mss;
2743
2744 skb = sock_wmalloc(sk, MAX_TCP_HEADER, 1, GFP_ATOMIC);
2745 if (unlikely(!skb)) {
2746 dst_release(dst);
2747 return NULL;
2748 }
2749 /* Reserve space for headers. */
2750 skb_reserve(skb, MAX_TCP_HEADER);
2751
2752 skb_dst_set(skb, dst);
2753 security_skb_owned_by(skb, sk);
2754
2755 mss = dst_metric_advmss(dst);
2756 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
2757 mss = tp->rx_opt.user_mss;
2758
2759 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
2760 __u8 rcv_wscale;
2761 /* Set this up on the first call only */
2762 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
2763
2764 /* limit the window selection if the user enforce a smaller rx buffer */
2765 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
2766 (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
2767 req->window_clamp = tcp_full_space(sk);
2768
2769 /* tcp_full_space because it is guaranteed to be the first packet */
2770 tcp_select_initial_window(tcp_full_space(sk),
2771 mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
2772 &req->rcv_wnd,
2773 &req->window_clamp,
2774 ireq->wscale_ok,
2775 &rcv_wscale,
2776 dst_metric(dst, RTAX_INITRWND));
2777 ireq->rcv_wscale = rcv_wscale;
2778 }
2779
2780 memset(&opts, 0, sizeof(opts));
2781#ifdef CONFIG_SYN_COOKIES
2782 if (unlikely(req->cookie_ts))
2783 TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
2784 else
2785#endif
2786 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2787 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5,
2788 foc) + sizeof(*th);
2789
2790 skb_push(skb, tcp_header_size);
2791 skb_reset_transport_header(skb);
2792
2793 th = tcp_hdr(skb);
2794 memset(th, 0, sizeof(struct tcphdr));
2795 th->syn = 1;
2796 th->ack = 1;
2797 TCP_ECN_make_synack(req, th);
2798 th->source = htons(ireq->ir_num);
2799 th->dest = ireq->ir_rmt_port;
2800 /* Setting of flags are superfluous here for callers (and ECE is
2801 * not even correctly set)
2802 */
2803 tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
2804 TCPHDR_SYN | TCPHDR_ACK);
2805
2806 th->seq = htonl(TCP_SKB_CB(skb)->seq);
2807 /* XXX data is queued and acked as is. No buffer/window check */
2808 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
2809
2810 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2811 th->window = htons(min(req->rcv_wnd, 65535U));
2812 tcp_options_write((__be32 *)(th + 1), tp, &opts);
2813 th->doff = (tcp_header_size >> 2);
2814 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_OUTSEGS);
2815
2816#ifdef CONFIG_TCP_MD5SIG
2817 /* Okay, we have all we need - do the md5 hash if needed */
2818 if (md5) {
2819 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
2820 md5, NULL, req, skb);
2821 }
2822#endif
2823
2824 return skb;
2825}
2826EXPORT_SYMBOL(tcp_make_synack);
2827
2828/* Do all connect socket setups that can be done AF independent. */
2829static void tcp_connect_init(struct sock *sk)
2830{
2831 const struct dst_entry *dst = __sk_dst_get(sk);
2832 struct tcp_sock *tp = tcp_sk(sk);
2833 __u8 rcv_wscale;
2834
2835 /* We'll fix this up when we get a response from the other end.
2836 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2837 */
2838 tp->tcp_header_len = sizeof(struct tcphdr) +
2839 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
2840
2841#ifdef CONFIG_TCP_MD5SIG
2842 if (tp->af_specific->md5_lookup(sk, sk) != NULL)
2843 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
2844#endif
2845
2846 /* If user gave his TCP_MAXSEG, record it to clamp */
2847 if (tp->rx_opt.user_mss)
2848 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
2849 tp->max_window = 0;
2850 tcp_mtup_init(sk);
2851 tcp_sync_mss(sk, dst_mtu(dst));
2852
2853 if (!tp->window_clamp)
2854 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
2855 tp->advmss = dst_metric_advmss(dst);
2856 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
2857 tp->advmss = tp->rx_opt.user_mss;
2858
2859 tcp_initialize_rcv_mss(sk);
2860
2861 /* limit the window selection if the user enforce a smaller rx buffer */
2862 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
2863 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
2864 tp->window_clamp = tcp_full_space(sk);
2865
2866 tcp_select_initial_window(tcp_full_space(sk),
2867 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
2868 &tp->rcv_wnd,
2869 &tp->window_clamp,
2870 sysctl_tcp_window_scaling,
2871 &rcv_wscale,
2872 dst_metric(dst, RTAX_INITRWND));
2873
2874 tp->rx_opt.rcv_wscale = rcv_wscale;
2875 tp->rcv_ssthresh = tp->rcv_wnd;
2876
2877 sk->sk_err = 0;
2878 sock_reset_flag(sk, SOCK_DONE);
2879 tp->snd_wnd = 0;
2880 tcp_init_wl(tp, 0);
2881 tp->snd_una = tp->write_seq;
2882 tp->snd_sml = tp->write_seq;
2883 tp->snd_up = tp->write_seq;
2884 tp->snd_nxt = tp->write_seq;
2885
2886 if (likely(!tp->repair))
2887 tp->rcv_nxt = 0;
2888 else
2889 tp->rcv_tstamp = tcp_time_stamp;
2890 tp->rcv_wup = tp->rcv_nxt;
2891 tp->copied_seq = tp->rcv_nxt;
2892
2893 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
2894 inet_csk(sk)->icsk_retransmits = 0;
2895 tcp_clear_retrans(tp);
2896}
2897
2898static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
2899{
2900 struct tcp_sock *tp = tcp_sk(sk);
2901 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
2902
2903 tcb->end_seq += skb->len;
2904 skb_header_release(skb);
2905 __tcp_add_write_queue_tail(sk, skb);
2906 sk->sk_wmem_queued += skb->truesize;
2907 sk_mem_charge(sk, skb->truesize);
2908 tp->write_seq = tcb->end_seq;
2909 tp->packets_out += tcp_skb_pcount(skb);
2910}
2911
2912/* Build and send a SYN with data and (cached) Fast Open cookie. However,
2913 * queue a data-only packet after the regular SYN, such that regular SYNs
2914 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
2915 * only the SYN sequence, the data are retransmitted in the first ACK.
2916 * If cookie is not cached or other error occurs, falls back to send a
2917 * regular SYN with Fast Open cookie request option.
2918 */
2919static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
2920{
2921 struct tcp_sock *tp = tcp_sk(sk);
2922 struct tcp_fastopen_request *fo = tp->fastopen_req;
2923 int syn_loss = 0, space, i, err = 0, iovlen = fo->data->msg_iovlen;
2924 struct sk_buff *syn_data = NULL, *data;
2925 unsigned long last_syn_loss = 0;
2926
2927 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
2928 tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
2929 &syn_loss, &last_syn_loss);
2930 /* Recurring FO SYN losses: revert to regular handshake temporarily */
2931 if (syn_loss > 1 &&
2932 time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
2933 fo->cookie.len = -1;
2934 goto fallback;
2935 }
2936
2937 if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
2938 fo->cookie.len = -1;
2939 else if (fo->cookie.len <= 0)
2940 goto fallback;
2941
2942 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
2943 * user-MSS. Reserve maximum option space for middleboxes that add
2944 * private TCP options. The cost is reduced data space in SYN :(
2945 */
2946 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
2947 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
2948 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
2949 MAX_TCP_OPTION_SPACE;
2950
2951 space = min_t(size_t, space, fo->size);
2952
2953 /* limit to order-0 allocations */
2954 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
2955
2956 syn_data = skb_copy_expand(syn, MAX_TCP_HEADER, space,
2957 sk->sk_allocation);
2958 if (syn_data == NULL)
2959 goto fallback;
2960
2961 for (i = 0; i < iovlen && syn_data->len < space; ++i) {
2962 struct iovec *iov = &fo->data->msg_iov[i];
2963 unsigned char __user *from = iov->iov_base;
2964 int len = iov->iov_len;
2965
2966 if (syn_data->len + len > space)
2967 len = space - syn_data->len;
2968 else if (i + 1 == iovlen)
2969 /* No more data pending in inet_wait_for_connect() */
2970 fo->data = NULL;
2971
2972 if (skb_add_data(syn_data, from, len))
2973 goto fallback;
2974 }
2975
2976 /* Queue a data-only packet after the regular SYN for retransmission */
2977 data = pskb_copy(syn_data, sk->sk_allocation);
2978 if (data == NULL)
2979 goto fallback;
2980 TCP_SKB_CB(data)->seq++;
2981 TCP_SKB_CB(data)->tcp_flags &= ~TCPHDR_SYN;
2982 TCP_SKB_CB(data)->tcp_flags = (TCPHDR_ACK|TCPHDR_PSH);
2983 tcp_connect_queue_skb(sk, data);
2984 fo->copied = data->len;
2985
2986 /* syn_data is about to be sent, we need to take current time stamps
2987 * for the packets that are in write queue : SYN packet and DATA
2988 */
2989 skb_mstamp_get(&syn->skb_mstamp);
2990 data->skb_mstamp = syn->skb_mstamp;
2991
2992 if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {
2993 tp->syn_data = (fo->copied > 0);
2994 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
2995 goto done;
2996 }
2997 syn_data = NULL;
2998
2999fallback:
3000 /* Send a regular SYN with Fast Open cookie request option */
3001 if (fo->cookie.len > 0)
3002 fo->cookie.len = 0;
3003 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3004 if (err)
3005 tp->syn_fastopen = 0;
3006 kfree_skb(syn_data);
3007done:
3008 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3009 return err;
3010}
3011
3012/* Build a SYN and send it off. */
3013int tcp_connect(struct sock *sk)
3014{
3015 struct tcp_sock *tp = tcp_sk(sk);
3016 struct sk_buff *buff;
3017 int err;
3018
3019 tcp_connect_init(sk);
3020
3021 if (unlikely(tp->repair)) {
3022 tcp_finish_connect(sk, NULL);
3023 return 0;
3024 }
3025
3026 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
3027 if (unlikely(buff == NULL))
3028 return -ENOBUFS;
3029
3030 /* Reserve space for headers. */
3031 skb_reserve(buff, MAX_TCP_HEADER);
3032
3033 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3034 tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp;
3035 tcp_connect_queue_skb(sk, buff);
3036 TCP_ECN_send_syn(sk, buff);
3037
3038 /* Send off SYN; include data in Fast Open. */
3039 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3040 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3041 if (err == -ECONNREFUSED)
3042 return err;
3043
3044 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3045 * in order to make this packet get counted in tcpOutSegs.
3046 */
3047 tp->snd_nxt = tp->write_seq;
3048 tp->pushed_seq = tp->write_seq;
3049 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3050
3051 /* Timer for repeating the SYN until an answer. */
3052 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3053 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3054 return 0;
3055}
3056EXPORT_SYMBOL(tcp_connect);
3057
3058/* Send out a delayed ack, the caller does the policy checking
3059 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3060 * for details.
3061 */
3062void tcp_send_delayed_ack(struct sock *sk)
3063{
3064 struct inet_connection_sock *icsk = inet_csk(sk);
3065 int ato = icsk->icsk_ack.ato;
3066 unsigned long timeout;
3067
3068 if (ato > TCP_DELACK_MIN) {
3069 const struct tcp_sock *tp = tcp_sk(sk);
3070 int max_ato = HZ / 2;
3071
3072 if (icsk->icsk_ack.pingpong ||
3073 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3074 max_ato = TCP_DELACK_MAX;
3075
3076 /* Slow path, intersegment interval is "high". */
3077
3078 /* If some rtt estimate is known, use it to bound delayed ack.
3079 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3080 * directly.
3081 */
3082 if (tp->srtt_us) {
3083 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3084 TCP_DELACK_MIN);
3085
3086 if (rtt < max_ato)
3087 max_ato = rtt;
3088 }
3089
3090 ato = min(ato, max_ato);
3091 }
3092
3093 /* Stay within the limit we were given */
3094 timeout = jiffies + ato;
3095
3096 /* Use new timeout only if there wasn't a older one earlier. */
3097 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3098 /* If delack timer was blocked or is about to expire,
3099 * send ACK now.
3100 */
3101 if (icsk->icsk_ack.blocked ||
3102 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3103 tcp_send_ack(sk);
3104 return;
3105 }
3106
3107 if (!time_before(timeout, icsk->icsk_ack.timeout))
3108 timeout = icsk->icsk_ack.timeout;
3109 }
3110 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3111 icsk->icsk_ack.timeout = timeout;
3112 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3113}
3114
3115/* This routine sends an ack and also updates the window. */
3116void tcp_send_ack(struct sock *sk)
3117{
3118 struct sk_buff *buff;
3119
3120 /* If we have been reset, we may not send again. */
3121 if (sk->sk_state == TCP_CLOSE)
3122 return;
3123
3124 /* We are not putting this on the write queue, so
3125 * tcp_transmit_skb() will set the ownership to this
3126 * sock.
3127 */
3128 buff = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3129 if (buff == NULL) {
3130 inet_csk_schedule_ack(sk);
3131 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
3132 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
3133 TCP_DELACK_MAX, TCP_RTO_MAX);
3134 return;
3135 }
3136
3137 /* Reserve space for headers and prepare control bits. */
3138 skb_reserve(buff, MAX_TCP_HEADER);
3139 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3140
3141 /* Send it off, this clears delayed acks for us. */
3142 TCP_SKB_CB(buff)->when = tcp_time_stamp;
3143 tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC));
3144}
3145
3146/* This routine sends a packet with an out of date sequence
3147 * number. It assumes the other end will try to ack it.
3148 *
3149 * Question: what should we make while urgent mode?
3150 * 4.4BSD forces sending single byte of data. We cannot send
3151 * out of window data, because we have SND.NXT==SND.MAX...
3152 *
3153 * Current solution: to send TWO zero-length segments in urgent mode:
3154 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3155 * out-of-date with SND.UNA-1 to probe window.
3156 */
3157static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
3158{
3159 struct tcp_sock *tp = tcp_sk(sk);
3160 struct sk_buff *skb;
3161
3162 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3163 skb = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3164 if (skb == NULL)
3165 return -1;
3166
3167 /* Reserve space for headers and set control bits. */
3168 skb_reserve(skb, MAX_TCP_HEADER);
3169 /* Use a previous sequence. This should cause the other
3170 * end to send an ack. Don't queue or clone SKB, just
3171 * send it.
3172 */
3173 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3174 TCP_SKB_CB(skb)->when = tcp_time_stamp;
3175 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
3176}
3177
3178void tcp_send_window_probe(struct sock *sk)
3179{
3180 if (sk->sk_state == TCP_ESTABLISHED) {
3181 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3182 tcp_xmit_probe_skb(sk, 0);
3183 }
3184}
3185
3186/* Initiate keepalive or window probe from timer. */
3187int tcp_write_wakeup(struct sock *sk)
3188{
3189 struct tcp_sock *tp = tcp_sk(sk);
3190 struct sk_buff *skb;
3191
3192 if (sk->sk_state == TCP_CLOSE)
3193 return -1;
3194
3195 if ((skb = tcp_send_head(sk)) != NULL &&
3196 before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3197 int err;
3198 unsigned int mss = tcp_current_mss(sk);
3199 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3200
3201 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
3202 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
3203
3204 /* We are probing the opening of a window
3205 * but the window size is != 0
3206 * must have been a result SWS avoidance ( sender )
3207 */
3208 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
3209 skb->len > mss) {
3210 seg_size = min(seg_size, mss);
3211 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3212 if (tcp_fragment(sk, skb, seg_size, mss))
3213 return -1;
3214 } else if (!tcp_skb_pcount(skb))
3215 tcp_set_skb_tso_segs(sk, skb, mss);
3216
3217 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3218 TCP_SKB_CB(skb)->when = tcp_time_stamp;
3219 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3220 if (!err)
3221 tcp_event_new_data_sent(sk, skb);
3222 return err;
3223 } else {
3224 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3225 tcp_xmit_probe_skb(sk, 1);
3226 return tcp_xmit_probe_skb(sk, 0);
3227 }
3228}
3229
3230/* A window probe timeout has occurred. If window is not closed send
3231 * a partial packet else a zero probe.
3232 */
3233void tcp_send_probe0(struct sock *sk)
3234{
3235 struct inet_connection_sock *icsk = inet_csk(sk);
3236 struct tcp_sock *tp = tcp_sk(sk);
3237 int err;
3238
3239 err = tcp_write_wakeup(sk);
3240
3241 if (tp->packets_out || !tcp_send_head(sk)) {
3242 /* Cancel probe timer, if it is not required. */
3243 icsk->icsk_probes_out = 0;
3244 icsk->icsk_backoff = 0;
3245 return;
3246 }
3247
3248 if (err <= 0) {
3249 if (icsk->icsk_backoff < sysctl_tcp_retries2)
3250 icsk->icsk_backoff++;
3251 icsk->icsk_probes_out++;
3252 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3253 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
3254 TCP_RTO_MAX);
3255 } else {
3256 /* If packet was not sent due to local congestion,
3257 * do not backoff and do not remember icsk_probes_out.
3258 * Let local senders to fight for local resources.
3259 *
3260 * Use accumulated backoff yet.
3261 */
3262 if (!icsk->icsk_probes_out)
3263 icsk->icsk_probes_out = 1;
3264 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3265 min(icsk->icsk_rto << icsk->icsk_backoff,
3266 TCP_RESOURCE_PROBE_INTERVAL),
3267 TCP_RTO_MAX);
3268 }
3269}