Loading...
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#include <linux/module.h>
22#include <linux/gfp.h>
23#include <net/tcp.h>
24
25int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES;
26int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES;
27int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME;
28int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES;
29int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
30int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
31int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
32int sysctl_tcp_orphan_retries __read_mostly;
33int sysctl_tcp_thin_linear_timeouts __read_mostly;
34
35static void tcp_write_err(struct sock *sk)
36{
37 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
38 sk->sk_error_report(sk);
39
40 tcp_done(sk);
41 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
42}
43
44/* Do not allow orphaned sockets to eat all our resources.
45 * This is direct violation of TCP specs, but it is required
46 * to prevent DoS attacks. It is called when a retransmission timeout
47 * or zero probe timeout occurs on orphaned socket.
48 *
49 * Criteria is still not confirmed experimentally and may change.
50 * We kill the socket, if:
51 * 1. If number of orphaned sockets exceeds an administratively configured
52 * limit.
53 * 2. If we have strong memory pressure.
54 */
55static int tcp_out_of_resources(struct sock *sk, int do_reset)
56{
57 struct tcp_sock *tp = tcp_sk(sk);
58 int shift = 0;
59
60 /* If peer does not open window for long time, or did not transmit
61 * anything for long time, penalize it. */
62 if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
63 shift++;
64
65 /* If some dubious ICMP arrived, penalize even more. */
66 if (sk->sk_err_soft)
67 shift++;
68
69 if (tcp_check_oom(sk, shift)) {
70 /* Catch exceptional cases, when connection requires reset.
71 * 1. Last segment was sent recently. */
72 if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
73 /* 2. Window is closed. */
74 (!tp->snd_wnd && !tp->packets_out))
75 do_reset = 1;
76 if (do_reset)
77 tcp_send_active_reset(sk, GFP_ATOMIC);
78 tcp_done(sk);
79 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
80 return 1;
81 }
82 return 0;
83}
84
85/* Calculate maximal number or retries on an orphaned socket. */
86static int tcp_orphan_retries(struct sock *sk, int alive)
87{
88 int retries = sysctl_tcp_orphan_retries; /* May be zero. */
89
90 /* We know from an ICMP that something is wrong. */
91 if (sk->sk_err_soft && !alive)
92 retries = 0;
93
94 /* However, if socket sent something recently, select some safe
95 * number of retries. 8 corresponds to >100 seconds with minimal
96 * RTO of 200msec. */
97 if (retries == 0 && alive)
98 retries = 8;
99 return retries;
100}
101
102static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
103{
104 /* Black hole detection */
105 if (sysctl_tcp_mtu_probing) {
106 if (!icsk->icsk_mtup.enabled) {
107 icsk->icsk_mtup.enabled = 1;
108 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
109 } else {
110 struct tcp_sock *tp = tcp_sk(sk);
111 int mss;
112
113 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
114 mss = min(sysctl_tcp_base_mss, mss);
115 mss = max(mss, 68 - tp->tcp_header_len);
116 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
117 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
118 }
119 }
120}
121
122/* This function calculates a "timeout" which is equivalent to the timeout of a
123 * TCP connection after "boundary" unsuccessful, exponentially backed-off
124 * retransmissions with an initial RTO of TCP_RTO_MIN or TCP_TIMEOUT_INIT if
125 * syn_set flag is set.
126 */
127static bool retransmits_timed_out(struct sock *sk,
128 unsigned int boundary,
129 unsigned int timeout,
130 bool syn_set)
131{
132 unsigned int linear_backoff_thresh, start_ts;
133 unsigned int rto_base = syn_set ? TCP_TIMEOUT_INIT : TCP_RTO_MIN;
134
135 if (!inet_csk(sk)->icsk_retransmits)
136 return false;
137
138 if (unlikely(!tcp_sk(sk)->retrans_stamp))
139 start_ts = TCP_SKB_CB(tcp_write_queue_head(sk))->when;
140 else
141 start_ts = tcp_sk(sk)->retrans_stamp;
142
143 if (likely(timeout == 0)) {
144 linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base);
145
146 if (boundary <= linear_backoff_thresh)
147 timeout = ((2 << boundary) - 1) * rto_base;
148 else
149 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +
150 (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
151 }
152 return (tcp_time_stamp - start_ts) >= timeout;
153}
154
155/* A write timeout has occurred. Process the after effects. */
156static int tcp_write_timeout(struct sock *sk)
157{
158 struct inet_connection_sock *icsk = inet_csk(sk);
159 struct tcp_sock *tp = tcp_sk(sk);
160 int retry_until;
161 bool do_reset, syn_set = false;
162
163 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
164 if (icsk->icsk_retransmits) {
165 dst_negative_advice(sk);
166 if (tp->syn_fastopen || tp->syn_data)
167 tcp_fastopen_cache_set(sk, 0, NULL, true);
168 if (tp->syn_data)
169 NET_INC_STATS_BH(sock_net(sk),
170 LINUX_MIB_TCPFASTOPENACTIVEFAIL);
171 }
172 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
173 syn_set = true;
174 } else {
175 if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0, 0)) {
176 /* Black hole detection */
177 tcp_mtu_probing(icsk, sk);
178
179 dst_negative_advice(sk);
180 }
181
182 retry_until = sysctl_tcp_retries2;
183 if (sock_flag(sk, SOCK_DEAD)) {
184 const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
185
186 retry_until = tcp_orphan_retries(sk, alive);
187 do_reset = alive ||
188 !retransmits_timed_out(sk, retry_until, 0, 0);
189
190 if (tcp_out_of_resources(sk, do_reset))
191 return 1;
192 }
193 }
194
195 if (retransmits_timed_out(sk, retry_until,
196 syn_set ? 0 : icsk->icsk_user_timeout, syn_set)) {
197 /* Has it gone just too far? */
198 tcp_write_err(sk);
199 return 1;
200 }
201 return 0;
202}
203
204void tcp_delack_timer_handler(struct sock *sk)
205{
206 struct tcp_sock *tp = tcp_sk(sk);
207 struct inet_connection_sock *icsk = inet_csk(sk);
208
209 sk_mem_reclaim_partial(sk);
210
211 if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
212 goto out;
213
214 if (time_after(icsk->icsk_ack.timeout, jiffies)) {
215 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
216 goto out;
217 }
218 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
219
220 if (!skb_queue_empty(&tp->ucopy.prequeue)) {
221 struct sk_buff *skb;
222
223 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
224
225 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
226 sk_backlog_rcv(sk, skb);
227
228 tp->ucopy.memory = 0;
229 }
230
231 if (inet_csk_ack_scheduled(sk)) {
232 if (!icsk->icsk_ack.pingpong) {
233 /* Delayed ACK missed: inflate ATO. */
234 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
235 } else {
236 /* Delayed ACK missed: leave pingpong mode and
237 * deflate ATO.
238 */
239 icsk->icsk_ack.pingpong = 0;
240 icsk->icsk_ack.ato = TCP_ATO_MIN;
241 }
242 tcp_send_ack(sk);
243 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
244 }
245
246out:
247 if (sk_under_memory_pressure(sk))
248 sk_mem_reclaim(sk);
249}
250
251static void tcp_delack_timer(unsigned long data)
252{
253 struct sock *sk = (struct sock *)data;
254
255 bh_lock_sock(sk);
256 if (!sock_owned_by_user(sk)) {
257 tcp_delack_timer_handler(sk);
258 } else {
259 inet_csk(sk)->icsk_ack.blocked = 1;
260 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
261 /* deleguate our work to tcp_release_cb() */
262 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
263 sock_hold(sk);
264 }
265 bh_unlock_sock(sk);
266 sock_put(sk);
267}
268
269static void tcp_probe_timer(struct sock *sk)
270{
271 struct inet_connection_sock *icsk = inet_csk(sk);
272 struct tcp_sock *tp = tcp_sk(sk);
273 int max_probes;
274
275 if (tp->packets_out || !tcp_send_head(sk)) {
276 icsk->icsk_probes_out = 0;
277 return;
278 }
279
280 /* *WARNING* RFC 1122 forbids this
281 *
282 * It doesn't AFAIK, because we kill the retransmit timer -AK
283 *
284 * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
285 * this behaviour in Solaris down as a bug fix. [AC]
286 *
287 * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
288 * even if they advertise zero window. Hence, connection is killed only
289 * if we received no ACKs for normal connection timeout. It is not killed
290 * only because window stays zero for some time, window may be zero
291 * until armageddon and even later. We are in full accordance
292 * with RFCs, only probe timer combines both retransmission timeout
293 * and probe timeout in one bottle. --ANK
294 */
295 max_probes = sysctl_tcp_retries2;
296
297 if (sock_flag(sk, SOCK_DEAD)) {
298 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
299
300 max_probes = tcp_orphan_retries(sk, alive);
301
302 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
303 return;
304 }
305
306 if (icsk->icsk_probes_out > max_probes) {
307 tcp_write_err(sk);
308 } else {
309 /* Only send another probe if we didn't close things up. */
310 tcp_send_probe0(sk);
311 }
312}
313
314/*
315 * Timer for Fast Open socket to retransmit SYNACK. Note that the
316 * sk here is the child socket, not the parent (listener) socket.
317 */
318static void tcp_fastopen_synack_timer(struct sock *sk)
319{
320 struct inet_connection_sock *icsk = inet_csk(sk);
321 int max_retries = icsk->icsk_syn_retries ? :
322 sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
323 struct request_sock *req;
324
325 req = tcp_sk(sk)->fastopen_rsk;
326 req->rsk_ops->syn_ack_timeout(sk, req);
327
328 if (req->num_timeout >= max_retries) {
329 tcp_write_err(sk);
330 return;
331 }
332 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
333 * returned from rtx_syn_ack() to make it more persistent like
334 * regular retransmit because if the child socket has been accepted
335 * it's not good to give up too easily.
336 */
337 inet_rtx_syn_ack(sk, req);
338 req->num_timeout++;
339 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
340 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
341}
342
343/*
344 * The TCP retransmit timer.
345 */
346
347void tcp_retransmit_timer(struct sock *sk)
348{
349 struct tcp_sock *tp = tcp_sk(sk);
350 struct inet_connection_sock *icsk = inet_csk(sk);
351
352 if (tp->fastopen_rsk) {
353 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
354 sk->sk_state != TCP_FIN_WAIT1);
355 tcp_fastopen_synack_timer(sk);
356 /* Before we receive ACK to our SYN-ACK don't retransmit
357 * anything else (e.g., data or FIN segments).
358 */
359 return;
360 }
361 if (!tp->packets_out)
362 goto out;
363
364 WARN_ON(tcp_write_queue_empty(sk));
365
366 tp->tlp_high_seq = 0;
367
368 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
369 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
370 /* Receiver dastardly shrinks window. Our retransmits
371 * become zero probes, but we should not timeout this
372 * connection. If the socket is an orphan, time it out,
373 * we cannot allow such beasts to hang infinitely.
374 */
375 struct inet_sock *inet = inet_sk(sk);
376 if (sk->sk_family == AF_INET) {
377 LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"),
378 &inet->inet_daddr,
379 ntohs(inet->inet_dport), inet->inet_num,
380 tp->snd_una, tp->snd_nxt);
381 }
382#if IS_ENABLED(CONFIG_IPV6)
383 else if (sk->sk_family == AF_INET6) {
384 LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"),
385 &sk->sk_v6_daddr,
386 ntohs(inet->inet_dport), inet->inet_num,
387 tp->snd_una, tp->snd_nxt);
388 }
389#endif
390 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
391 tcp_write_err(sk);
392 goto out;
393 }
394 tcp_enter_loss(sk, 0);
395 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
396 __sk_dst_reset(sk);
397 goto out_reset_timer;
398 }
399
400 if (tcp_write_timeout(sk))
401 goto out;
402
403 if (icsk->icsk_retransmits == 0) {
404 int mib_idx;
405
406 if (icsk->icsk_ca_state == TCP_CA_Recovery) {
407 if (tcp_is_sack(tp))
408 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
409 else
410 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
411 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
412 mib_idx = LINUX_MIB_TCPLOSSFAILURES;
413 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
414 tp->sacked_out) {
415 if (tcp_is_sack(tp))
416 mib_idx = LINUX_MIB_TCPSACKFAILURES;
417 else
418 mib_idx = LINUX_MIB_TCPRENOFAILURES;
419 } else {
420 mib_idx = LINUX_MIB_TCPTIMEOUTS;
421 }
422 NET_INC_STATS_BH(sock_net(sk), mib_idx);
423 }
424
425 tcp_enter_loss(sk, 0);
426
427 if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
428 /* Retransmission failed because of local congestion,
429 * do not backoff.
430 */
431 if (!icsk->icsk_retransmits)
432 icsk->icsk_retransmits = 1;
433 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
434 min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
435 TCP_RTO_MAX);
436 goto out;
437 }
438
439 /* Increase the timeout each time we retransmit. Note that
440 * we do not increase the rtt estimate. rto is initialized
441 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
442 * that doubling rto each time is the least we can get away with.
443 * In KA9Q, Karn uses this for the first few times, and then
444 * goes to quadratic. netBSD doubles, but only goes up to *64,
445 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
446 * defined in the protocol as the maximum possible RTT. I guess
447 * we'll have to use something other than TCP to talk to the
448 * University of Mars.
449 *
450 * PAWS allows us longer timeouts and large windows, so once
451 * implemented ftp to mars will work nicely. We will have to fix
452 * the 120 second clamps though!
453 */
454 icsk->icsk_backoff++;
455 icsk->icsk_retransmits++;
456
457out_reset_timer:
458 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
459 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
460 * might be increased if the stream oscillates between thin and thick,
461 * thus the old value might already be too high compared to the value
462 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
463 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
464 * exponential backoff behaviour to avoid continue hammering
465 * linear-timeout retransmissions into a black hole
466 */
467 if (sk->sk_state == TCP_ESTABLISHED &&
468 (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) &&
469 tcp_stream_is_thin(tp) &&
470 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
471 icsk->icsk_backoff = 0;
472 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
473 } else {
474 /* Use normal (exponential) backoff */
475 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
476 }
477 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
478 if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1, 0, 0))
479 __sk_dst_reset(sk);
480
481out:;
482}
483
484void tcp_write_timer_handler(struct sock *sk)
485{
486 struct inet_connection_sock *icsk = inet_csk(sk);
487 int event;
488
489 if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
490 goto out;
491
492 if (time_after(icsk->icsk_timeout, jiffies)) {
493 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
494 goto out;
495 }
496
497 event = icsk->icsk_pending;
498
499 switch (event) {
500 case ICSK_TIME_EARLY_RETRANS:
501 tcp_resume_early_retransmit(sk);
502 break;
503 case ICSK_TIME_LOSS_PROBE:
504 tcp_send_loss_probe(sk);
505 break;
506 case ICSK_TIME_RETRANS:
507 icsk->icsk_pending = 0;
508 tcp_retransmit_timer(sk);
509 break;
510 case ICSK_TIME_PROBE0:
511 icsk->icsk_pending = 0;
512 tcp_probe_timer(sk);
513 break;
514 }
515
516out:
517 sk_mem_reclaim(sk);
518}
519
520static void tcp_write_timer(unsigned long data)
521{
522 struct sock *sk = (struct sock *)data;
523
524 bh_lock_sock(sk);
525 if (!sock_owned_by_user(sk)) {
526 tcp_write_timer_handler(sk);
527 } else {
528 /* deleguate our work to tcp_release_cb() */
529 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
530 sock_hold(sk);
531 }
532 bh_unlock_sock(sk);
533 sock_put(sk);
534}
535
536/*
537 * Timer for listening sockets
538 */
539
540static void tcp_synack_timer(struct sock *sk)
541{
542 inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
543 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
544}
545
546void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
547{
548 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
549}
550EXPORT_SYMBOL(tcp_syn_ack_timeout);
551
552void tcp_set_keepalive(struct sock *sk, int val)
553{
554 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
555 return;
556
557 if (val && !sock_flag(sk, SOCK_KEEPOPEN))
558 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
559 else if (!val)
560 inet_csk_delete_keepalive_timer(sk);
561}
562
563
564static void tcp_keepalive_timer (unsigned long data)
565{
566 struct sock *sk = (struct sock *) data;
567 struct inet_connection_sock *icsk = inet_csk(sk);
568 struct tcp_sock *tp = tcp_sk(sk);
569 u32 elapsed;
570
571 /* Only process if socket is not in use. */
572 bh_lock_sock(sk);
573 if (sock_owned_by_user(sk)) {
574 /* Try again later. */
575 inet_csk_reset_keepalive_timer (sk, HZ/20);
576 goto out;
577 }
578
579 if (sk->sk_state == TCP_LISTEN) {
580 tcp_synack_timer(sk);
581 goto out;
582 }
583
584 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
585 if (tp->linger2 >= 0) {
586 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
587
588 if (tmo > 0) {
589 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
590 goto out;
591 }
592 }
593 tcp_send_active_reset(sk, GFP_ATOMIC);
594 goto death;
595 }
596
597 if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
598 goto out;
599
600 elapsed = keepalive_time_when(tp);
601
602 /* It is alive without keepalive 8) */
603 if (tp->packets_out || tcp_send_head(sk))
604 goto resched;
605
606 elapsed = keepalive_time_elapsed(tp);
607
608 if (elapsed >= keepalive_time_when(tp)) {
609 /* If the TCP_USER_TIMEOUT option is enabled, use that
610 * to determine when to timeout instead.
611 */
612 if ((icsk->icsk_user_timeout != 0 &&
613 elapsed >= icsk->icsk_user_timeout &&
614 icsk->icsk_probes_out > 0) ||
615 (icsk->icsk_user_timeout == 0 &&
616 icsk->icsk_probes_out >= keepalive_probes(tp))) {
617 tcp_send_active_reset(sk, GFP_ATOMIC);
618 tcp_write_err(sk);
619 goto out;
620 }
621 if (tcp_write_wakeup(sk) <= 0) {
622 icsk->icsk_probes_out++;
623 elapsed = keepalive_intvl_when(tp);
624 } else {
625 /* If keepalive was lost due to local congestion,
626 * try harder.
627 */
628 elapsed = TCP_RESOURCE_PROBE_INTERVAL;
629 }
630 } else {
631 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
632 elapsed = keepalive_time_when(tp) - elapsed;
633 }
634
635 sk_mem_reclaim(sk);
636
637resched:
638 inet_csk_reset_keepalive_timer (sk, elapsed);
639 goto out;
640
641death:
642 tcp_done(sk);
643
644out:
645 bh_unlock_sock(sk);
646 sock_put(sk);
647}
648
649void tcp_init_xmit_timers(struct sock *sk)
650{
651 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
652 &tcp_keepalive_timer);
653}
654EXPORT_SYMBOL(tcp_init_xmit_timers);
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#include <linux/module.h>
22#include <linux/gfp.h>
23#include <net/tcp.h>
24
25int sysctl_tcp_thin_linear_timeouts __read_mostly;
26
27/**
28 * tcp_write_err() - close socket and save error info
29 * @sk: The socket the error has appeared on.
30 *
31 * Returns: Nothing (void)
32 */
33
34static void tcp_write_err(struct sock *sk)
35{
36 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
37 sk->sk_error_report(sk);
38
39 tcp_done(sk);
40 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
41}
42
43/**
44 * tcp_out_of_resources() - Close socket if out of resources
45 * @sk: pointer to current socket
46 * @do_reset: send a last packet with reset flag
47 *
48 * Do not allow orphaned sockets to eat all our resources.
49 * This is direct violation of TCP specs, but it is required
50 * to prevent DoS attacks. It is called when a retransmission timeout
51 * or zero probe timeout occurs on orphaned socket.
52 *
53 * Criteria is still not confirmed experimentally and may change.
54 * We kill the socket, if:
55 * 1. If number of orphaned sockets exceeds an administratively configured
56 * limit.
57 * 2. If we have strong memory pressure.
58 */
59static int tcp_out_of_resources(struct sock *sk, bool do_reset)
60{
61 struct tcp_sock *tp = tcp_sk(sk);
62 int shift = 0;
63
64 /* If peer does not open window for long time, or did not transmit
65 * anything for long time, penalize it. */
66 if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
67 shift++;
68
69 /* If some dubious ICMP arrived, penalize even more. */
70 if (sk->sk_err_soft)
71 shift++;
72
73 if (tcp_check_oom(sk, shift)) {
74 /* Catch exceptional cases, when connection requires reset.
75 * 1. Last segment was sent recently. */
76 if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
77 /* 2. Window is closed. */
78 (!tp->snd_wnd && !tp->packets_out))
79 do_reset = true;
80 if (do_reset)
81 tcp_send_active_reset(sk, GFP_ATOMIC);
82 tcp_done(sk);
83 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
84 return 1;
85 }
86 return 0;
87}
88
89/**
90 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket
91 * @sk: Pointer to the current socket.
92 * @alive: bool, socket alive state
93 */
94static int tcp_orphan_retries(struct sock *sk, bool alive)
95{
96 int retries = sock_net(sk)->ipv4.sysctl_tcp_orphan_retries; /* May be zero. */
97
98 /* We know from an ICMP that something is wrong. */
99 if (sk->sk_err_soft && !alive)
100 retries = 0;
101
102 /* However, if socket sent something recently, select some safe
103 * number of retries. 8 corresponds to >100 seconds with minimal
104 * RTO of 200msec. */
105 if (retries == 0 && alive)
106 retries = 8;
107 return retries;
108}
109
110static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
111{
112 struct net *net = sock_net(sk);
113
114 /* Black hole detection */
115 if (net->ipv4.sysctl_tcp_mtu_probing) {
116 if (!icsk->icsk_mtup.enabled) {
117 icsk->icsk_mtup.enabled = 1;
118 icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
119 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
120 } else {
121 struct net *net = sock_net(sk);
122 struct tcp_sock *tp = tcp_sk(sk);
123 int mss;
124
125 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
126 mss = min(net->ipv4.sysctl_tcp_base_mss, mss);
127 mss = max(mss, 68 - tp->tcp_header_len);
128 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
129 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
130 }
131 }
132}
133
134
135/**
136 * retransmits_timed_out() - returns true if this connection has timed out
137 * @sk: The current socket
138 * @boundary: max number of retransmissions
139 * @timeout: A custom timeout value.
140 * If set to 0 the default timeout is calculated and used.
141 * Using TCP_RTO_MIN and the number of unsuccessful retransmits.
142 * @syn_set: true if the SYN Bit was set.
143 *
144 * The default "timeout" value this function can calculate and use
145 * is equivalent to the timeout of a TCP Connection
146 * after "boundary" unsuccessful, exponentially backed-off
147 * retransmissions with an initial RTO of TCP_RTO_MIN or TCP_TIMEOUT_INIT if
148 * syn_set flag is set.
149 *
150 */
151static bool retransmits_timed_out(struct sock *sk,
152 unsigned int boundary,
153 unsigned int timeout,
154 bool syn_set)
155{
156 unsigned int linear_backoff_thresh, start_ts;
157 unsigned int rto_base = syn_set ? TCP_TIMEOUT_INIT : TCP_RTO_MIN;
158
159 if (!inet_csk(sk)->icsk_retransmits)
160 return false;
161
162 start_ts = tcp_sk(sk)->retrans_stamp;
163 if (unlikely(!start_ts))
164 start_ts = tcp_skb_timestamp(tcp_write_queue_head(sk));
165
166 if (likely(timeout == 0)) {
167 linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base);
168
169 if (boundary <= linear_backoff_thresh)
170 timeout = ((2 << boundary) - 1) * rto_base;
171 else
172 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +
173 (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
174 }
175 return (tcp_time_stamp - start_ts) >= timeout;
176}
177
178/* A write timeout has occurred. Process the after effects. */
179static int tcp_write_timeout(struct sock *sk)
180{
181 struct inet_connection_sock *icsk = inet_csk(sk);
182 struct tcp_sock *tp = tcp_sk(sk);
183 struct net *net = sock_net(sk);
184 int retry_until;
185 bool do_reset, syn_set = false;
186
187 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
188 if (icsk->icsk_retransmits) {
189 dst_negative_advice(sk);
190 if (tp->syn_fastopen || tp->syn_data)
191 tcp_fastopen_cache_set(sk, 0, NULL, true, 0);
192 if (tp->syn_data && icsk->icsk_retransmits == 1)
193 NET_INC_STATS(sock_net(sk),
194 LINUX_MIB_TCPFASTOPENACTIVEFAIL);
195 } else if (!tp->syn_data && !tp->syn_fastopen) {
196 sk_rethink_txhash(sk);
197 }
198 retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries;
199 syn_set = true;
200 } else {
201 if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0, 0)) {
202 /* Some middle-boxes may black-hole Fast Open _after_
203 * the handshake. Therefore we conservatively disable
204 * Fast Open on this path on recurring timeouts with
205 * few or zero bytes acked after Fast Open.
206 */
207 if (tp->syn_data_acked &&
208 tp->bytes_acked <= tp->rx_opt.mss_clamp) {
209 tcp_fastopen_cache_set(sk, 0, NULL, true, 0);
210 if (icsk->icsk_retransmits == net->ipv4.sysctl_tcp_retries1)
211 NET_INC_STATS(sock_net(sk),
212 LINUX_MIB_TCPFASTOPENACTIVEFAIL);
213 }
214 /* Black hole detection */
215 tcp_mtu_probing(icsk, sk);
216
217 dst_negative_advice(sk);
218 } else {
219 sk_rethink_txhash(sk);
220 }
221
222 retry_until = net->ipv4.sysctl_tcp_retries2;
223 if (sock_flag(sk, SOCK_DEAD)) {
224 const bool alive = icsk->icsk_rto < TCP_RTO_MAX;
225
226 retry_until = tcp_orphan_retries(sk, alive);
227 do_reset = alive ||
228 !retransmits_timed_out(sk, retry_until, 0, 0);
229
230 if (tcp_out_of_resources(sk, do_reset))
231 return 1;
232 }
233 }
234
235 if (retransmits_timed_out(sk, retry_until,
236 syn_set ? 0 : icsk->icsk_user_timeout, syn_set)) {
237 /* Has it gone just too far? */
238 tcp_write_err(sk);
239 return 1;
240 }
241 return 0;
242}
243
244/* Called with BH disabled */
245void tcp_delack_timer_handler(struct sock *sk)
246{
247 struct tcp_sock *tp = tcp_sk(sk);
248 struct inet_connection_sock *icsk = inet_csk(sk);
249
250 sk_mem_reclaim_partial(sk);
251
252 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
253 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
254 goto out;
255
256 if (time_after(icsk->icsk_ack.timeout, jiffies)) {
257 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
258 goto out;
259 }
260 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
261
262 if (!skb_queue_empty(&tp->ucopy.prequeue)) {
263 struct sk_buff *skb;
264
265 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
266
267 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
268 sk_backlog_rcv(sk, skb);
269
270 tp->ucopy.memory = 0;
271 }
272
273 if (inet_csk_ack_scheduled(sk)) {
274 if (!icsk->icsk_ack.pingpong) {
275 /* Delayed ACK missed: inflate ATO. */
276 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
277 } else {
278 /* Delayed ACK missed: leave pingpong mode and
279 * deflate ATO.
280 */
281 icsk->icsk_ack.pingpong = 0;
282 icsk->icsk_ack.ato = TCP_ATO_MIN;
283 }
284 tcp_send_ack(sk);
285 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
286 }
287
288out:
289 if (tcp_under_memory_pressure(sk))
290 sk_mem_reclaim(sk);
291}
292
293
294/**
295 * tcp_delack_timer() - The TCP delayed ACK timeout handler
296 * @data: Pointer to the current socket. (gets casted to struct sock *)
297 *
298 * This function gets (indirectly) called when the kernel timer for a TCP packet
299 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work.
300 *
301 * Returns: Nothing (void)
302 */
303static void tcp_delack_timer(unsigned long data)
304{
305 struct sock *sk = (struct sock *)data;
306
307 bh_lock_sock(sk);
308 if (!sock_owned_by_user(sk)) {
309 tcp_delack_timer_handler(sk);
310 } else {
311 inet_csk(sk)->icsk_ack.blocked = 1;
312 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
313 /* deleguate our work to tcp_release_cb() */
314 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags))
315 sock_hold(sk);
316 }
317 bh_unlock_sock(sk);
318 sock_put(sk);
319}
320
321static void tcp_probe_timer(struct sock *sk)
322{
323 struct inet_connection_sock *icsk = inet_csk(sk);
324 struct tcp_sock *tp = tcp_sk(sk);
325 int max_probes;
326 u32 start_ts;
327
328 if (tp->packets_out || !tcp_send_head(sk)) {
329 icsk->icsk_probes_out = 0;
330 return;
331 }
332
333 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as
334 * long as the receiver continues to respond probes. We support this by
335 * default and reset icsk_probes_out with incoming ACKs. But if the
336 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we
337 * kill the socket when the retry count and the time exceeds the
338 * corresponding system limit. We also implement similar policy when
339 * we use RTO to probe window in tcp_retransmit_timer().
340 */
341 start_ts = tcp_skb_timestamp(tcp_send_head(sk));
342 if (!start_ts)
343 skb_mstamp_get(&tcp_send_head(sk)->skb_mstamp);
344 else if (icsk->icsk_user_timeout &&
345 (s32)(tcp_time_stamp - start_ts) > icsk->icsk_user_timeout)
346 goto abort;
347
348 max_probes = sock_net(sk)->ipv4.sysctl_tcp_retries2;
349 if (sock_flag(sk, SOCK_DEAD)) {
350 const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
351
352 max_probes = tcp_orphan_retries(sk, alive);
353 if (!alive && icsk->icsk_backoff >= max_probes)
354 goto abort;
355 if (tcp_out_of_resources(sk, true))
356 return;
357 }
358
359 if (icsk->icsk_probes_out > max_probes) {
360abort: tcp_write_err(sk);
361 } else {
362 /* Only send another probe if we didn't close things up. */
363 tcp_send_probe0(sk);
364 }
365}
366
367/*
368 * Timer for Fast Open socket to retransmit SYNACK. Note that the
369 * sk here is the child socket, not the parent (listener) socket.
370 */
371static void tcp_fastopen_synack_timer(struct sock *sk)
372{
373 struct inet_connection_sock *icsk = inet_csk(sk);
374 int max_retries = icsk->icsk_syn_retries ? :
375 sock_net(sk)->ipv4.sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
376 struct request_sock *req;
377
378 req = tcp_sk(sk)->fastopen_rsk;
379 req->rsk_ops->syn_ack_timeout(req);
380
381 if (req->num_timeout >= max_retries) {
382 tcp_write_err(sk);
383 return;
384 }
385 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
386 * returned from rtx_syn_ack() to make it more persistent like
387 * regular retransmit because if the child socket has been accepted
388 * it's not good to give up too easily.
389 */
390 inet_rtx_syn_ack(sk, req);
391 req->num_timeout++;
392 icsk->icsk_retransmits++;
393 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
394 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
395}
396
397
398/**
399 * tcp_retransmit_timer() - The TCP retransmit timeout handler
400 * @sk: Pointer to the current socket.
401 *
402 * This function gets called when the kernel timer for a TCP packet
403 * of this socket expires.
404 *
405 * It handles retransmission, timer adjustment and other necesarry measures.
406 *
407 * Returns: Nothing (void)
408 */
409void tcp_retransmit_timer(struct sock *sk)
410{
411 struct tcp_sock *tp = tcp_sk(sk);
412 struct net *net = sock_net(sk);
413 struct inet_connection_sock *icsk = inet_csk(sk);
414
415 if (tp->fastopen_rsk) {
416 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
417 sk->sk_state != TCP_FIN_WAIT1);
418 tcp_fastopen_synack_timer(sk);
419 /* Before we receive ACK to our SYN-ACK don't retransmit
420 * anything else (e.g., data or FIN segments).
421 */
422 return;
423 }
424 if (!tp->packets_out)
425 goto out;
426
427 WARN_ON(tcp_write_queue_empty(sk));
428
429 tp->tlp_high_seq = 0;
430
431 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
432 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
433 /* Receiver dastardly shrinks window. Our retransmits
434 * become zero probes, but we should not timeout this
435 * connection. If the socket is an orphan, time it out,
436 * we cannot allow such beasts to hang infinitely.
437 */
438 struct inet_sock *inet = inet_sk(sk);
439 if (sk->sk_family == AF_INET) {
440 net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
441 &inet->inet_daddr,
442 ntohs(inet->inet_dport),
443 inet->inet_num,
444 tp->snd_una, tp->snd_nxt);
445 }
446#if IS_ENABLED(CONFIG_IPV6)
447 else if (sk->sk_family == AF_INET6) {
448 net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
449 &sk->sk_v6_daddr,
450 ntohs(inet->inet_dport),
451 inet->inet_num,
452 tp->snd_una, tp->snd_nxt);
453 }
454#endif
455 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
456 tcp_write_err(sk);
457 goto out;
458 }
459 tcp_enter_loss(sk);
460 tcp_retransmit_skb(sk, tcp_write_queue_head(sk), 1);
461 __sk_dst_reset(sk);
462 goto out_reset_timer;
463 }
464
465 if (tcp_write_timeout(sk))
466 goto out;
467
468 if (icsk->icsk_retransmits == 0) {
469 int mib_idx;
470
471 if (icsk->icsk_ca_state == TCP_CA_Recovery) {
472 if (tcp_is_sack(tp))
473 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
474 else
475 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
476 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
477 mib_idx = LINUX_MIB_TCPLOSSFAILURES;
478 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
479 tp->sacked_out) {
480 if (tcp_is_sack(tp))
481 mib_idx = LINUX_MIB_TCPSACKFAILURES;
482 else
483 mib_idx = LINUX_MIB_TCPRENOFAILURES;
484 } else {
485 mib_idx = LINUX_MIB_TCPTIMEOUTS;
486 }
487 __NET_INC_STATS(sock_net(sk), mib_idx);
488 }
489
490 tcp_enter_loss(sk);
491
492 if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk), 1) > 0) {
493 /* Retransmission failed because of local congestion,
494 * do not backoff.
495 */
496 if (!icsk->icsk_retransmits)
497 icsk->icsk_retransmits = 1;
498 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
499 min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
500 TCP_RTO_MAX);
501 goto out;
502 }
503
504 /* Increase the timeout each time we retransmit. Note that
505 * we do not increase the rtt estimate. rto is initialized
506 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
507 * that doubling rto each time is the least we can get away with.
508 * In KA9Q, Karn uses this for the first few times, and then
509 * goes to quadratic. netBSD doubles, but only goes up to *64,
510 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
511 * defined in the protocol as the maximum possible RTT. I guess
512 * we'll have to use something other than TCP to talk to the
513 * University of Mars.
514 *
515 * PAWS allows us longer timeouts and large windows, so once
516 * implemented ftp to mars will work nicely. We will have to fix
517 * the 120 second clamps though!
518 */
519 icsk->icsk_backoff++;
520 icsk->icsk_retransmits++;
521
522out_reset_timer:
523 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
524 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
525 * might be increased if the stream oscillates between thin and thick,
526 * thus the old value might already be too high compared to the value
527 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
528 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
529 * exponential backoff behaviour to avoid continue hammering
530 * linear-timeout retransmissions into a black hole
531 */
532 if (sk->sk_state == TCP_ESTABLISHED &&
533 (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) &&
534 tcp_stream_is_thin(tp) &&
535 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
536 icsk->icsk_backoff = 0;
537 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
538 } else {
539 /* Use normal (exponential) backoff */
540 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
541 }
542 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
543 if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1 + 1, 0, 0))
544 __sk_dst_reset(sk);
545
546out:;
547}
548
549/* Called with bottom-half processing disabled.
550 Called by tcp_write_timer() */
551void tcp_write_timer_handler(struct sock *sk)
552{
553 struct inet_connection_sock *icsk = inet_csk(sk);
554 int event;
555
556 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
557 !icsk->icsk_pending)
558 goto out;
559
560 if (time_after(icsk->icsk_timeout, jiffies)) {
561 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
562 goto out;
563 }
564
565 event = icsk->icsk_pending;
566
567 switch (event) {
568 case ICSK_TIME_EARLY_RETRANS:
569 tcp_resume_early_retransmit(sk);
570 break;
571 case ICSK_TIME_LOSS_PROBE:
572 tcp_send_loss_probe(sk);
573 break;
574 case ICSK_TIME_RETRANS:
575 icsk->icsk_pending = 0;
576 tcp_retransmit_timer(sk);
577 break;
578 case ICSK_TIME_PROBE0:
579 icsk->icsk_pending = 0;
580 tcp_probe_timer(sk);
581 break;
582 }
583
584out:
585 sk_mem_reclaim(sk);
586}
587
588static void tcp_write_timer(unsigned long data)
589{
590 struct sock *sk = (struct sock *)data;
591
592 bh_lock_sock(sk);
593 if (!sock_owned_by_user(sk)) {
594 tcp_write_timer_handler(sk);
595 } else {
596 /* delegate our work to tcp_release_cb() */
597 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags))
598 sock_hold(sk);
599 }
600 bh_unlock_sock(sk);
601 sock_put(sk);
602}
603
604void tcp_syn_ack_timeout(const struct request_sock *req)
605{
606 struct net *net = read_pnet(&inet_rsk(req)->ireq_net);
607
608 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS);
609}
610EXPORT_SYMBOL(tcp_syn_ack_timeout);
611
612void tcp_set_keepalive(struct sock *sk, int val)
613{
614 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
615 return;
616
617 if (val && !sock_flag(sk, SOCK_KEEPOPEN))
618 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
619 else if (!val)
620 inet_csk_delete_keepalive_timer(sk);
621}
622
623
624static void tcp_keepalive_timer (unsigned long data)
625{
626 struct sock *sk = (struct sock *) data;
627 struct inet_connection_sock *icsk = inet_csk(sk);
628 struct tcp_sock *tp = tcp_sk(sk);
629 u32 elapsed;
630
631 /* Only process if socket is not in use. */
632 bh_lock_sock(sk);
633 if (sock_owned_by_user(sk)) {
634 /* Try again later. */
635 inet_csk_reset_keepalive_timer (sk, HZ/20);
636 goto out;
637 }
638
639 if (sk->sk_state == TCP_LISTEN) {
640 pr_err("Hmm... keepalive on a LISTEN ???\n");
641 goto out;
642 }
643
644 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
645 if (tp->linger2 >= 0) {
646 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
647
648 if (tmo > 0) {
649 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
650 goto out;
651 }
652 }
653 tcp_send_active_reset(sk, GFP_ATOMIC);
654 goto death;
655 }
656
657 if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
658 goto out;
659
660 elapsed = keepalive_time_when(tp);
661
662 /* It is alive without keepalive 8) */
663 if (tp->packets_out || tcp_send_head(sk))
664 goto resched;
665
666 elapsed = keepalive_time_elapsed(tp);
667
668 if (elapsed >= keepalive_time_when(tp)) {
669 /* If the TCP_USER_TIMEOUT option is enabled, use that
670 * to determine when to timeout instead.
671 */
672 if ((icsk->icsk_user_timeout != 0 &&
673 elapsed >= icsk->icsk_user_timeout &&
674 icsk->icsk_probes_out > 0) ||
675 (icsk->icsk_user_timeout == 0 &&
676 icsk->icsk_probes_out >= keepalive_probes(tp))) {
677 tcp_send_active_reset(sk, GFP_ATOMIC);
678 tcp_write_err(sk);
679 goto out;
680 }
681 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) {
682 icsk->icsk_probes_out++;
683 elapsed = keepalive_intvl_when(tp);
684 } else {
685 /* If keepalive was lost due to local congestion,
686 * try harder.
687 */
688 elapsed = TCP_RESOURCE_PROBE_INTERVAL;
689 }
690 } else {
691 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
692 elapsed = keepalive_time_when(tp) - elapsed;
693 }
694
695 sk_mem_reclaim(sk);
696
697resched:
698 inet_csk_reset_keepalive_timer (sk, elapsed);
699 goto out;
700
701death:
702 tcp_done(sk);
703
704out:
705 bh_unlock_sock(sk);
706 sock_put(sk);
707}
708
709void tcp_init_xmit_timers(struct sock *sk)
710{
711 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
712 &tcp_keepalive_timer);
713}