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
25static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk)
26{
27 struct inet_connection_sock *icsk = inet_csk(sk);
28 u32 elapsed, start_ts;
29 s32 remaining;
30
31 start_ts = tcp_sk(sk)->retrans_stamp;
32 if (!icsk->icsk_user_timeout)
33 return icsk->icsk_rto;
34 elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts;
35 remaining = icsk->icsk_user_timeout - elapsed;
36 if (remaining <= 0)
37 return 1; /* user timeout has passed; fire ASAP */
38
39 return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining));
40}
41
42/**
43 * tcp_write_err() - close socket and save error info
44 * @sk: The socket the error has appeared on.
45 *
46 * Returns: Nothing (void)
47 */
48
49static void tcp_write_err(struct sock *sk)
50{
51 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
52 sk->sk_error_report(sk);
53
54 tcp_write_queue_purge(sk);
55 tcp_done(sk);
56 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
57}
58
59/**
60 * tcp_out_of_resources() - Close socket if out of resources
61 * @sk: pointer to current socket
62 * @do_reset: send a last packet with reset flag
63 *
64 * Do not allow orphaned sockets to eat all our resources.
65 * This is direct violation of TCP specs, but it is required
66 * to prevent DoS attacks. It is called when a retransmission timeout
67 * or zero probe timeout occurs on orphaned socket.
68 *
69 * Also close if our net namespace is exiting; in that case there is no
70 * hope of ever communicating again since all netns interfaces are already
71 * down (or about to be down), and we need to release our dst references,
72 * which have been moved to the netns loopback interface, so the namespace
73 * can finish exiting. This condition is only possible if we are a kernel
74 * socket, as those do not hold references to the namespace.
75 *
76 * Criteria is still not confirmed experimentally and may change.
77 * We kill the socket, if:
78 * 1. If number of orphaned sockets exceeds an administratively configured
79 * limit.
80 * 2. If we have strong memory pressure.
81 * 3. If our net namespace is exiting.
82 */
83static int tcp_out_of_resources(struct sock *sk, bool do_reset)
84{
85 struct tcp_sock *tp = tcp_sk(sk);
86 int shift = 0;
87
88 /* If peer does not open window for long time, or did not transmit
89 * anything for long time, penalize it. */
90 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
91 shift++;
92
93 /* If some dubious ICMP arrived, penalize even more. */
94 if (sk->sk_err_soft)
95 shift++;
96
97 if (tcp_check_oom(sk, shift)) {
98 /* Catch exceptional cases, when connection requires reset.
99 * 1. Last segment was sent recently. */
100 if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
101 /* 2. Window is closed. */
102 (!tp->snd_wnd && !tp->packets_out))
103 do_reset = true;
104 if (do_reset)
105 tcp_send_active_reset(sk, GFP_ATOMIC);
106 tcp_done(sk);
107 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
108 return 1;
109 }
110
111 if (!check_net(sock_net(sk))) {
112 /* Not possible to send reset; just close */
113 tcp_done(sk);
114 return 1;
115 }
116
117 return 0;
118}
119
120/**
121 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket
122 * @sk: Pointer to the current socket.
123 * @alive: bool, socket alive state
124 */
125static int tcp_orphan_retries(struct sock *sk, bool alive)
126{
127 int retries = sock_net(sk)->ipv4.sysctl_tcp_orphan_retries; /* May be zero. */
128
129 /* We know from an ICMP that something is wrong. */
130 if (sk->sk_err_soft && !alive)
131 retries = 0;
132
133 /* However, if socket sent something recently, select some safe
134 * number of retries. 8 corresponds to >100 seconds with minimal
135 * RTO of 200msec. */
136 if (retries == 0 && alive)
137 retries = 8;
138 return retries;
139}
140
141static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
142{
143 const struct net *net = sock_net(sk);
144 int mss;
145
146 /* Black hole detection */
147 if (!net->ipv4.sysctl_tcp_mtu_probing)
148 return;
149
150 if (!icsk->icsk_mtup.enabled) {
151 icsk->icsk_mtup.enabled = 1;
152 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
153 } else {
154 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
155 mss = min(net->ipv4.sysctl_tcp_base_mss, mss);
156 mss = max(mss, 68 - tcp_sk(sk)->tcp_header_len);
157 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
158 }
159 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
160}
161
162static unsigned int tcp_model_timeout(struct sock *sk,
163 unsigned int boundary,
164 unsigned int rto_base)
165{
166 unsigned int linear_backoff_thresh, timeout;
167
168 linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base);
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 return jiffies_to_msecs(timeout);
175}
176/**
177 * retransmits_timed_out() - returns true if this connection has timed out
178 * @sk: The current socket
179 * @boundary: max number of retransmissions
180 * @timeout: A custom timeout value.
181 * If set to 0 the default timeout is calculated and used.
182 * Using TCP_RTO_MIN and the number of unsuccessful retransmits.
183 *
184 * The default "timeout" value this function can calculate and use
185 * is equivalent to the timeout of a TCP Connection
186 * after "boundary" unsuccessful, exponentially backed-off
187 * retransmissions with an initial RTO of TCP_RTO_MIN.
188 */
189static bool retransmits_timed_out(struct sock *sk,
190 unsigned int boundary,
191 unsigned int timeout)
192{
193 unsigned int start_ts;
194
195 if (!inet_csk(sk)->icsk_retransmits)
196 return false;
197
198 start_ts = tcp_sk(sk)->retrans_stamp;
199 if (likely(timeout == 0))
200 timeout = tcp_model_timeout(sk, boundary, TCP_RTO_MIN);
201
202 return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0;
203}
204
205/* A write timeout has occurred. Process the after effects. */
206static int tcp_write_timeout(struct sock *sk)
207{
208 struct inet_connection_sock *icsk = inet_csk(sk);
209 struct tcp_sock *tp = tcp_sk(sk);
210 struct net *net = sock_net(sk);
211 bool expired, do_reset;
212 int retry_until;
213
214 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
215 if (icsk->icsk_retransmits) {
216 dst_negative_advice(sk);
217 } else {
218 sk_rethink_txhash(sk);
219 }
220 retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries;
221 expired = icsk->icsk_retransmits >= retry_until;
222 } else {
223 if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) {
224 /* Black hole detection */
225 tcp_mtu_probing(icsk, sk);
226
227 dst_negative_advice(sk);
228 } else {
229 sk_rethink_txhash(sk);
230 }
231
232 retry_until = net->ipv4.sysctl_tcp_retries2;
233 if (sock_flag(sk, SOCK_DEAD)) {
234 const bool alive = icsk->icsk_rto < TCP_RTO_MAX;
235
236 retry_until = tcp_orphan_retries(sk, alive);
237 do_reset = alive ||
238 !retransmits_timed_out(sk, retry_until, 0);
239
240 if (tcp_out_of_resources(sk, do_reset))
241 return 1;
242 }
243 expired = retransmits_timed_out(sk, retry_until,
244 icsk->icsk_user_timeout);
245 }
246 tcp_fastopen_active_detect_blackhole(sk, expired);
247
248 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG))
249 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB,
250 icsk->icsk_retransmits,
251 icsk->icsk_rto, (int)expired);
252
253 if (expired) {
254 /* Has it gone just too far? */
255 tcp_write_err(sk);
256 return 1;
257 }
258
259 return 0;
260}
261
262/* Called with BH disabled */
263void tcp_delack_timer_handler(struct sock *sk)
264{
265 struct inet_connection_sock *icsk = inet_csk(sk);
266
267 sk_mem_reclaim_partial(sk);
268
269 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
270 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
271 goto out;
272
273 if (time_after(icsk->icsk_ack.timeout, jiffies)) {
274 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
275 goto out;
276 }
277 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
278
279 if (inet_csk_ack_scheduled(sk)) {
280 if (!inet_csk_in_pingpong_mode(sk)) {
281 /* Delayed ACK missed: inflate ATO. */
282 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
283 } else {
284 /* Delayed ACK missed: leave pingpong mode and
285 * deflate ATO.
286 */
287 inet_csk_exit_pingpong_mode(sk);
288 icsk->icsk_ack.ato = TCP_ATO_MIN;
289 }
290 tcp_mstamp_refresh(tcp_sk(sk));
291 tcp_send_ack(sk);
292 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
293 }
294
295out:
296 if (tcp_under_memory_pressure(sk))
297 sk_mem_reclaim(sk);
298}
299
300
301/**
302 * tcp_delack_timer() - The TCP delayed ACK timeout handler
303 * @data: Pointer to the current socket. (gets casted to struct sock *)
304 *
305 * This function gets (indirectly) called when the kernel timer for a TCP packet
306 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work.
307 *
308 * Returns: Nothing (void)
309 */
310static void tcp_delack_timer(struct timer_list *t)
311{
312 struct inet_connection_sock *icsk =
313 from_timer(icsk, t, icsk_delack_timer);
314 struct sock *sk = &icsk->icsk_inet.sk;
315
316 bh_lock_sock(sk);
317 if (!sock_owned_by_user(sk)) {
318 tcp_delack_timer_handler(sk);
319 } else {
320 icsk->icsk_ack.blocked = 1;
321 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
322 /* deleguate our work to tcp_release_cb() */
323 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags))
324 sock_hold(sk);
325 }
326 bh_unlock_sock(sk);
327 sock_put(sk);
328}
329
330static void tcp_probe_timer(struct sock *sk)
331{
332 struct inet_connection_sock *icsk = inet_csk(sk);
333 struct sk_buff *skb = tcp_send_head(sk);
334 struct tcp_sock *tp = tcp_sk(sk);
335 int max_probes;
336
337 if (tp->packets_out || !skb) {
338 icsk->icsk_probes_out = 0;
339 return;
340 }
341
342 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as
343 * long as the receiver continues to respond probes. We support this by
344 * default and reset icsk_probes_out with incoming ACKs. But if the
345 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we
346 * kill the socket when the retry count and the time exceeds the
347 * corresponding system limit. We also implement similar policy when
348 * we use RTO to probe window in tcp_retransmit_timer().
349 */
350 if (icsk->icsk_user_timeout) {
351 u32 elapsed = tcp_model_timeout(sk, icsk->icsk_probes_out,
352 tcp_probe0_base(sk));
353
354 if (elapsed >= icsk->icsk_user_timeout)
355 goto abort;
356 }
357
358 max_probes = sock_net(sk)->ipv4.sysctl_tcp_retries2;
359 if (sock_flag(sk, SOCK_DEAD)) {
360 const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
361
362 max_probes = tcp_orphan_retries(sk, alive);
363 if (!alive && icsk->icsk_backoff >= max_probes)
364 goto abort;
365 if (tcp_out_of_resources(sk, true))
366 return;
367 }
368
369 if (icsk->icsk_probes_out >= max_probes) {
370abort: tcp_write_err(sk);
371 } else {
372 /* Only send another probe if we didn't close things up. */
373 tcp_send_probe0(sk);
374 }
375}
376
377/*
378 * Timer for Fast Open socket to retransmit SYNACK. Note that the
379 * sk here is the child socket, not the parent (listener) socket.
380 */
381static void tcp_fastopen_synack_timer(struct sock *sk)
382{
383 struct inet_connection_sock *icsk = inet_csk(sk);
384 int max_retries = icsk->icsk_syn_retries ? :
385 sock_net(sk)->ipv4.sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
386 struct tcp_sock *tp = tcp_sk(sk);
387 struct request_sock *req;
388
389 req = tcp_sk(sk)->fastopen_rsk;
390 req->rsk_ops->syn_ack_timeout(req);
391
392 if (req->num_timeout >= max_retries) {
393 tcp_write_err(sk);
394 return;
395 }
396 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
397 * returned from rtx_syn_ack() to make it more persistent like
398 * regular retransmit because if the child socket has been accepted
399 * it's not good to give up too easily.
400 */
401 inet_rtx_syn_ack(sk, req);
402 req->num_timeout++;
403 icsk->icsk_retransmits++;
404 if (!tp->retrans_stamp)
405 tp->retrans_stamp = tcp_time_stamp(tp);
406 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
407 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
408}
409
410
411/**
412 * tcp_retransmit_timer() - The TCP retransmit timeout handler
413 * @sk: Pointer to the current socket.
414 *
415 * This function gets called when the kernel timer for a TCP packet
416 * of this socket expires.
417 *
418 * It handles retransmission, timer adjustment and other necesarry measures.
419 *
420 * Returns: Nothing (void)
421 */
422void tcp_retransmit_timer(struct sock *sk)
423{
424 struct tcp_sock *tp = tcp_sk(sk);
425 struct net *net = sock_net(sk);
426 struct inet_connection_sock *icsk = inet_csk(sk);
427
428 if (tp->fastopen_rsk) {
429 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
430 sk->sk_state != TCP_FIN_WAIT1);
431 tcp_fastopen_synack_timer(sk);
432 /* Before we receive ACK to our SYN-ACK don't retransmit
433 * anything else (e.g., data or FIN segments).
434 */
435 return;
436 }
437 if (!tp->packets_out || WARN_ON_ONCE(tcp_rtx_queue_empty(sk)))
438 return;
439
440 tp->tlp_high_seq = 0;
441
442 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
443 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
444 /* Receiver dastardly shrinks window. Our retransmits
445 * become zero probes, but we should not timeout this
446 * connection. If the socket is an orphan, time it out,
447 * we cannot allow such beasts to hang infinitely.
448 */
449 struct inet_sock *inet = inet_sk(sk);
450 if (sk->sk_family == AF_INET) {
451 net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
452 &inet->inet_daddr,
453 ntohs(inet->inet_dport),
454 inet->inet_num,
455 tp->snd_una, tp->snd_nxt);
456 }
457#if IS_ENABLED(CONFIG_IPV6)
458 else if (sk->sk_family == AF_INET6) {
459 net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
460 &sk->sk_v6_daddr,
461 ntohs(inet->inet_dport),
462 inet->inet_num,
463 tp->snd_una, tp->snd_nxt);
464 }
465#endif
466 if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) {
467 tcp_write_err(sk);
468 goto out;
469 }
470 tcp_enter_loss(sk);
471 tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1);
472 __sk_dst_reset(sk);
473 goto out_reset_timer;
474 }
475
476 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
477 if (tcp_write_timeout(sk))
478 goto out;
479
480 if (icsk->icsk_retransmits == 0) {
481 int mib_idx = 0;
482
483 if (icsk->icsk_ca_state == TCP_CA_Recovery) {
484 if (tcp_is_sack(tp))
485 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
486 else
487 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
488 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
489 mib_idx = LINUX_MIB_TCPLOSSFAILURES;
490 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
491 tp->sacked_out) {
492 if (tcp_is_sack(tp))
493 mib_idx = LINUX_MIB_TCPSACKFAILURES;
494 else
495 mib_idx = LINUX_MIB_TCPRENOFAILURES;
496 }
497 if (mib_idx)
498 __NET_INC_STATS(sock_net(sk), mib_idx);
499 }
500
501 tcp_enter_loss(sk);
502
503 icsk->icsk_retransmits++;
504 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) {
505 /* Retransmission failed because of local congestion,
506 * Let senders fight for local resources conservatively.
507 */
508 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
509 TCP_RESOURCE_PROBE_INTERVAL,
510 TCP_RTO_MAX);
511 goto out;
512 }
513
514 /* Increase the timeout each time we retransmit. Note that
515 * we do not increase the rtt estimate. rto is initialized
516 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
517 * that doubling rto each time is the least we can get away with.
518 * In KA9Q, Karn uses this for the first few times, and then
519 * goes to quadratic. netBSD doubles, but only goes up to *64,
520 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
521 * defined in the protocol as the maximum possible RTT. I guess
522 * we'll have to use something other than TCP to talk to the
523 * University of Mars.
524 *
525 * PAWS allows us longer timeouts and large windows, so once
526 * implemented ftp to mars will work nicely. We will have to fix
527 * the 120 second clamps though!
528 */
529 icsk->icsk_backoff++;
530
531out_reset_timer:
532 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
533 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
534 * might be increased if the stream oscillates between thin and thick,
535 * thus the old value might already be too high compared to the value
536 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
537 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
538 * exponential backoff behaviour to avoid continue hammering
539 * linear-timeout retransmissions into a black hole
540 */
541 if (sk->sk_state == TCP_ESTABLISHED &&
542 (tp->thin_lto || net->ipv4.sysctl_tcp_thin_linear_timeouts) &&
543 tcp_stream_is_thin(tp) &&
544 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
545 icsk->icsk_backoff = 0;
546 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
547 } else {
548 /* Use normal (exponential) backoff */
549 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
550 }
551 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
552 tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX);
553 if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1 + 1, 0))
554 __sk_dst_reset(sk);
555
556out:;
557}
558
559/* Called with bottom-half processing disabled.
560 Called by tcp_write_timer() */
561void tcp_write_timer_handler(struct sock *sk)
562{
563 struct inet_connection_sock *icsk = inet_csk(sk);
564 int event;
565
566 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
567 !icsk->icsk_pending)
568 goto out;
569
570 if (time_after(icsk->icsk_timeout, jiffies)) {
571 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
572 goto out;
573 }
574
575 tcp_mstamp_refresh(tcp_sk(sk));
576 event = icsk->icsk_pending;
577
578 switch (event) {
579 case ICSK_TIME_REO_TIMEOUT:
580 tcp_rack_reo_timeout(sk);
581 break;
582 case ICSK_TIME_LOSS_PROBE:
583 tcp_send_loss_probe(sk);
584 break;
585 case ICSK_TIME_RETRANS:
586 icsk->icsk_pending = 0;
587 tcp_retransmit_timer(sk);
588 break;
589 case ICSK_TIME_PROBE0:
590 icsk->icsk_pending = 0;
591 tcp_probe_timer(sk);
592 break;
593 }
594
595out:
596 sk_mem_reclaim(sk);
597}
598
599static void tcp_write_timer(struct timer_list *t)
600{
601 struct inet_connection_sock *icsk =
602 from_timer(icsk, t, icsk_retransmit_timer);
603 struct sock *sk = &icsk->icsk_inet.sk;
604
605 bh_lock_sock(sk);
606 if (!sock_owned_by_user(sk)) {
607 tcp_write_timer_handler(sk);
608 } else {
609 /* delegate our work to tcp_release_cb() */
610 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags))
611 sock_hold(sk);
612 }
613 bh_unlock_sock(sk);
614 sock_put(sk);
615}
616
617void tcp_syn_ack_timeout(const struct request_sock *req)
618{
619 struct net *net = read_pnet(&inet_rsk(req)->ireq_net);
620
621 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS);
622}
623EXPORT_SYMBOL(tcp_syn_ack_timeout);
624
625void tcp_set_keepalive(struct sock *sk, int val)
626{
627 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
628 return;
629
630 if (val && !sock_flag(sk, SOCK_KEEPOPEN))
631 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
632 else if (!val)
633 inet_csk_delete_keepalive_timer(sk);
634}
635EXPORT_SYMBOL_GPL(tcp_set_keepalive);
636
637
638static void tcp_keepalive_timer (struct timer_list *t)
639{
640 struct sock *sk = from_timer(sk, t, sk_timer);
641 struct inet_connection_sock *icsk = inet_csk(sk);
642 struct tcp_sock *tp = tcp_sk(sk);
643 u32 elapsed;
644
645 /* Only process if socket is not in use. */
646 bh_lock_sock(sk);
647 if (sock_owned_by_user(sk)) {
648 /* Try again later. */
649 inet_csk_reset_keepalive_timer (sk, HZ/20);
650 goto out;
651 }
652
653 if (sk->sk_state == TCP_LISTEN) {
654 pr_err("Hmm... keepalive on a LISTEN ???\n");
655 goto out;
656 }
657
658 tcp_mstamp_refresh(tp);
659 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
660 if (tp->linger2 >= 0) {
661 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
662
663 if (tmo > 0) {
664 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
665 goto out;
666 }
667 }
668 tcp_send_active_reset(sk, GFP_ATOMIC);
669 goto death;
670 }
671
672 if (!sock_flag(sk, SOCK_KEEPOPEN) ||
673 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT)))
674 goto out;
675
676 elapsed = keepalive_time_when(tp);
677
678 /* It is alive without keepalive 8) */
679 if (tp->packets_out || !tcp_write_queue_empty(sk))
680 goto resched;
681
682 elapsed = keepalive_time_elapsed(tp);
683
684 if (elapsed >= keepalive_time_when(tp)) {
685 /* If the TCP_USER_TIMEOUT option is enabled, use that
686 * to determine when to timeout instead.
687 */
688 if ((icsk->icsk_user_timeout != 0 &&
689 elapsed >= msecs_to_jiffies(icsk->icsk_user_timeout) &&
690 icsk->icsk_probes_out > 0) ||
691 (icsk->icsk_user_timeout == 0 &&
692 icsk->icsk_probes_out >= keepalive_probes(tp))) {
693 tcp_send_active_reset(sk, GFP_ATOMIC);
694 tcp_write_err(sk);
695 goto out;
696 }
697 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) {
698 icsk->icsk_probes_out++;
699 elapsed = keepalive_intvl_when(tp);
700 } else {
701 /* If keepalive was lost due to local congestion,
702 * try harder.
703 */
704 elapsed = TCP_RESOURCE_PROBE_INTERVAL;
705 }
706 } else {
707 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
708 elapsed = keepalive_time_when(tp) - elapsed;
709 }
710
711 sk_mem_reclaim(sk);
712
713resched:
714 inet_csk_reset_keepalive_timer (sk, elapsed);
715 goto out;
716
717death:
718 tcp_done(sk);
719
720out:
721 bh_unlock_sock(sk);
722 sock_put(sk);
723}
724
725static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer)
726{
727 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer);
728 struct sock *sk = (struct sock *)tp;
729
730 bh_lock_sock(sk);
731 if (!sock_owned_by_user(sk)) {
732 if (tp->compressed_ack > TCP_FASTRETRANS_THRESH)
733 tcp_send_ack(sk);
734 } else {
735 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
736 &sk->sk_tsq_flags))
737 sock_hold(sk);
738 }
739 bh_unlock_sock(sk);
740
741 sock_put(sk);
742
743 return HRTIMER_NORESTART;
744}
745
746void tcp_init_xmit_timers(struct sock *sk)
747{
748 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
749 &tcp_keepalive_timer);
750 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC,
751 HRTIMER_MODE_ABS_PINNED_SOFT);
752 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick;
753
754 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC,
755 HRTIMER_MODE_REL_PINNED_SOFT);
756 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick;
757}
758