1 // SPDX-License-Identifier: GPL-2.0-only
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.
7 * Implementation of the Transmission Control Protocol(TCP).
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>
22 #include <linux/module.h>
23 #include <linux/gfp.h>
26 static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk)
28 struct inet_connection_sock *icsk = inet_csk(sk);
29 u32 elapsed, start_ts;
32 start_ts = tcp_sk(sk)->retrans_stamp;
33 if (!icsk->icsk_user_timeout)
34 return icsk->icsk_rto;
35 elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts;
36 remaining = icsk->icsk_user_timeout - elapsed;
38 return 1; /* user timeout has passed; fire ASAP */
40 return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining));
43 u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when)
45 struct inet_connection_sock *icsk = inet_csk(sk);
49 if (!icsk->icsk_user_timeout || !icsk->icsk_probes_tstamp)
52 elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp;
53 if (unlikely(elapsed < 0))
55 remaining = msecs_to_jiffies(icsk->icsk_user_timeout) - elapsed;
56 remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN);
58 return min_t(u32, remaining, when);
62 * tcp_write_err() - close socket and save error info
63 * @sk: The socket the error has appeared on.
65 * Returns: Nothing (void)
68 static void tcp_write_err(struct sock *sk)
70 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
73 tcp_write_queue_purge(sk);
75 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
79 * tcp_out_of_resources() - Close socket if out of resources
80 * @sk: pointer to current socket
81 * @do_reset: send a last packet with reset flag
83 * Do not allow orphaned sockets to eat all our resources.
84 * This is direct violation of TCP specs, but it is required
85 * to prevent DoS attacks. It is called when a retransmission timeout
86 * or zero probe timeout occurs on orphaned socket.
88 * Also close if our net namespace is exiting; in that case there is no
89 * hope of ever communicating again since all netns interfaces are already
90 * down (or about to be down), and we need to release our dst references,
91 * which have been moved to the netns loopback interface, so the namespace
92 * can finish exiting. This condition is only possible if we are a kernel
93 * socket, as those do not hold references to the namespace.
95 * Criteria is still not confirmed experimentally and may change.
96 * We kill the socket, if:
97 * 1. If number of orphaned sockets exceeds an administratively configured
99 * 2. If we have strong memory pressure.
100 * 3. If our net namespace is exiting.
102 static int tcp_out_of_resources(struct sock *sk, bool do_reset)
104 struct tcp_sock *tp = tcp_sk(sk);
107 /* If peer does not open window for long time, or did not transmit
108 * anything for long time, penalize it. */
109 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
112 /* If some dubious ICMP arrived, penalize even more. */
116 if (tcp_check_oom(sk, shift)) {
117 /* Catch exceptional cases, when connection requires reset.
118 * 1. Last segment was sent recently. */
119 if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
120 /* 2. Window is closed. */
121 (!tp->snd_wnd && !tp->packets_out))
124 tcp_send_active_reset(sk, GFP_ATOMIC);
126 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
130 if (!check_net(sock_net(sk))) {
131 /* Not possible to send reset; just close */
140 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket
141 * @sk: Pointer to the current socket.
142 * @alive: bool, socket alive state
144 static int tcp_orphan_retries(struct sock *sk, bool alive)
146 int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */
148 /* We know from an ICMP that something is wrong. */
149 if (sk->sk_err_soft && !alive)
152 /* However, if socket sent something recently, select some safe
153 * number of retries. 8 corresponds to >100 seconds with minimal
155 if (retries == 0 && alive)
160 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
162 const struct net *net = sock_net(sk);
165 /* Black hole detection */
166 if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing))
169 if (!icsk->icsk_mtup.enabled) {
170 icsk->icsk_mtup.enabled = 1;
171 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32;
173 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
174 mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss);
175 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_mtu_probe_floor));
176 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss));
177 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
179 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
182 static unsigned int tcp_model_timeout(struct sock *sk,
183 unsigned int boundary,
184 unsigned int rto_base)
186 unsigned int linear_backoff_thresh, timeout;
188 linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base);
189 if (boundary <= linear_backoff_thresh)
190 timeout = ((2 << boundary) - 1) * rto_base;
192 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +
193 (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
194 return jiffies_to_msecs(timeout);
197 * retransmits_timed_out() - returns true if this connection has timed out
198 * @sk: The current socket
199 * @boundary: max number of retransmissions
200 * @timeout: A custom timeout value.
201 * If set to 0 the default timeout is calculated and used.
202 * Using TCP_RTO_MIN and the number of unsuccessful retransmits.
204 * The default "timeout" value this function can calculate and use
205 * is equivalent to the timeout of a TCP Connection
206 * after "boundary" unsuccessful, exponentially backed-off
207 * retransmissions with an initial RTO of TCP_RTO_MIN.
209 static bool retransmits_timed_out(struct sock *sk,
210 unsigned int boundary,
211 unsigned int timeout)
213 unsigned int start_ts;
215 if (!inet_csk(sk)->icsk_retransmits)
218 start_ts = tcp_sk(sk)->retrans_stamp;
219 if (likely(timeout == 0)) {
220 unsigned int rto_base = TCP_RTO_MIN;
222 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
223 rto_base = tcp_timeout_init(sk);
224 timeout = tcp_model_timeout(sk, boundary, rto_base);
227 return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0;
230 /* A write timeout has occurred. Process the after effects. */
231 static int tcp_write_timeout(struct sock *sk)
233 struct inet_connection_sock *icsk = inet_csk(sk);
234 struct tcp_sock *tp = tcp_sk(sk);
235 struct net *net = sock_net(sk);
236 bool expired = false, do_reset;
239 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
240 if (icsk->icsk_retransmits)
241 __dst_negative_advice(sk);
242 retry_until = icsk->icsk_syn_retries ? :
243 READ_ONCE(net->ipv4.sysctl_tcp_syn_retries);
244 expired = icsk->icsk_retransmits >= retry_until;
246 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) {
247 /* Black hole detection */
248 tcp_mtu_probing(icsk, sk);
250 __dst_negative_advice(sk);
253 retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2);
254 if (sock_flag(sk, SOCK_DEAD)) {
255 const bool alive = icsk->icsk_rto < TCP_RTO_MAX;
257 retry_until = tcp_orphan_retries(sk, alive);
259 !retransmits_timed_out(sk, retry_until, 0);
261 if (tcp_out_of_resources(sk, do_reset))
266 expired = retransmits_timed_out(sk, retry_until,
267 icsk->icsk_user_timeout);
268 tcp_fastopen_active_detect_blackhole(sk, expired);
270 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG))
271 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB,
272 icsk->icsk_retransmits,
273 icsk->icsk_rto, (int)expired);
276 /* Has it gone just too far? */
281 if (sk_rethink_txhash(sk)) {
282 tp->timeout_rehash++;
283 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH);
289 /* Called with BH disabled */
290 void tcp_delack_timer_handler(struct sock *sk)
292 struct inet_connection_sock *icsk = inet_csk(sk);
294 sk_mem_reclaim_partial(sk);
296 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
297 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
300 if (time_after(icsk->icsk_ack.timeout, jiffies)) {
301 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
304 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
306 if (inet_csk_ack_scheduled(sk)) {
307 if (!inet_csk_in_pingpong_mode(sk)) {
308 /* Delayed ACK missed: inflate ATO. */
309 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
311 /* Delayed ACK missed: leave pingpong mode and
314 inet_csk_exit_pingpong_mode(sk);
315 icsk->icsk_ack.ato = TCP_ATO_MIN;
317 tcp_mstamp_refresh(tcp_sk(sk));
319 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
323 if (tcp_under_memory_pressure(sk))
329 * tcp_delack_timer() - The TCP delayed ACK timeout handler
330 * @t: Pointer to the timer. (gets casted to struct sock *)
332 * This function gets (indirectly) called when the kernel timer for a TCP packet
333 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work.
335 * Returns: Nothing (void)
337 static void tcp_delack_timer(struct timer_list *t)
339 struct inet_connection_sock *icsk =
340 from_timer(icsk, t, icsk_delack_timer);
341 struct sock *sk = &icsk->icsk_inet.sk;
344 if (!sock_owned_by_user(sk)) {
345 tcp_delack_timer_handler(sk);
347 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
348 /* deleguate our work to tcp_release_cb() */
349 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags))
356 static void tcp_probe_timer(struct sock *sk)
358 struct inet_connection_sock *icsk = inet_csk(sk);
359 struct sk_buff *skb = tcp_send_head(sk);
360 struct tcp_sock *tp = tcp_sk(sk);
363 if (tp->packets_out || !skb) {
364 icsk->icsk_probes_out = 0;
365 icsk->icsk_probes_tstamp = 0;
369 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as
370 * long as the receiver continues to respond probes. We support this by
371 * default and reset icsk_probes_out with incoming ACKs. But if the
372 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we
373 * kill the socket when the retry count and the time exceeds the
374 * corresponding system limit. We also implement similar policy when
375 * we use RTO to probe window in tcp_retransmit_timer().
377 if (!icsk->icsk_probes_tstamp)
378 icsk->icsk_probes_tstamp = tcp_jiffies32;
379 else if (icsk->icsk_user_timeout &&
380 (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >=
381 msecs_to_jiffies(icsk->icsk_user_timeout))
384 max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2);
385 if (sock_flag(sk, SOCK_DEAD)) {
386 const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
388 max_probes = tcp_orphan_retries(sk, alive);
389 if (!alive && icsk->icsk_backoff >= max_probes)
391 if (tcp_out_of_resources(sk, true))
395 if (icsk->icsk_probes_out >= max_probes) {
396 abort: tcp_write_err(sk);
398 /* Only send another probe if we didn't close things up. */
404 * Timer for Fast Open socket to retransmit SYNACK. Note that the
405 * sk here is the child socket, not the parent (listener) socket.
407 static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req)
409 struct inet_connection_sock *icsk = inet_csk(sk);
410 struct tcp_sock *tp = tcp_sk(sk);
413 req->rsk_ops->syn_ack_timeout(req);
415 /* add one more retry for fastopen */
416 max_retries = icsk->icsk_syn_retries ? :
417 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1;
419 if (req->num_timeout >= max_retries) {
423 /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */
424 if (icsk->icsk_retransmits == 1)
426 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
427 * returned from rtx_syn_ack() to make it more persistent like
428 * regular retransmit because if the child socket has been accepted
429 * it's not good to give up too easily.
431 inet_rtx_syn_ack(sk, req);
433 icsk->icsk_retransmits++;
434 if (!tp->retrans_stamp)
435 tp->retrans_stamp = tcp_time_stamp(tp);
436 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
437 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
442 * tcp_retransmit_timer() - The TCP retransmit timeout handler
443 * @sk: Pointer to the current socket.
445 * This function gets called when the kernel timer for a TCP packet
446 * of this socket expires.
448 * It handles retransmission, timer adjustment and other necessary measures.
450 * Returns: Nothing (void)
452 void tcp_retransmit_timer(struct sock *sk)
454 struct tcp_sock *tp = tcp_sk(sk);
455 struct net *net = sock_net(sk);
456 struct inet_connection_sock *icsk = inet_csk(sk);
457 struct request_sock *req;
460 req = rcu_dereference_protected(tp->fastopen_rsk,
461 lockdep_sock_is_held(sk));
463 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
464 sk->sk_state != TCP_FIN_WAIT1);
465 tcp_fastopen_synack_timer(sk, req);
466 /* Before we receive ACK to our SYN-ACK don't retransmit
467 * anything else (e.g., data or FIN segments).
472 if (!tp->packets_out)
475 skb = tcp_rtx_queue_head(sk);
476 if (WARN_ON_ONCE(!skb))
479 tp->tlp_high_seq = 0;
481 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
482 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
483 /* Receiver dastardly shrinks window. Our retransmits
484 * become zero probes, but we should not timeout this
485 * connection. If the socket is an orphan, time it out,
486 * we cannot allow such beasts to hang infinitely.
488 struct inet_sock *inet = inet_sk(sk);
489 if (sk->sk_family == AF_INET) {
490 net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
492 ntohs(inet->inet_dport),
494 tp->snd_una, tp->snd_nxt);
496 #if IS_ENABLED(CONFIG_IPV6)
497 else if (sk->sk_family == AF_INET6) {
498 net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
500 ntohs(inet->inet_dport),
502 tp->snd_una, tp->snd_nxt);
505 if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) {
510 tcp_retransmit_skb(sk, skb, 1);
512 goto out_reset_timer;
515 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
516 if (tcp_write_timeout(sk))
519 if (icsk->icsk_retransmits == 0) {
522 if (icsk->icsk_ca_state == TCP_CA_Recovery) {
524 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
526 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
527 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
528 mib_idx = LINUX_MIB_TCPLOSSFAILURES;
529 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
532 mib_idx = LINUX_MIB_TCPSACKFAILURES;
534 mib_idx = LINUX_MIB_TCPRENOFAILURES;
537 __NET_INC_STATS(sock_net(sk), mib_idx);
542 icsk->icsk_retransmits++;
543 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) {
544 /* Retransmission failed because of local congestion,
545 * Let senders fight for local resources conservatively.
547 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
548 TCP_RESOURCE_PROBE_INTERVAL,
553 /* Increase the timeout each time we retransmit. Note that
554 * we do not increase the rtt estimate. rto is initialized
555 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
556 * that doubling rto each time is the least we can get away with.
557 * In KA9Q, Karn uses this for the first few times, and then
558 * goes to quadratic. netBSD doubles, but only goes up to *64,
559 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
560 * defined in the protocol as the maximum possible RTT. I guess
561 * we'll have to use something other than TCP to talk to the
562 * University of Mars.
564 * PAWS allows us longer timeouts and large windows, so once
565 * implemented ftp to mars will work nicely. We will have to fix
566 * the 120 second clamps though!
568 icsk->icsk_backoff++;
571 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
572 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
573 * might be increased if the stream oscillates between thin and thick,
574 * thus the old value might already be too high compared to the value
575 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
576 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
577 * exponential backoff behaviour to avoid continue hammering
578 * linear-timeout retransmissions into a black hole
580 if (sk->sk_state == TCP_ESTABLISHED &&
581 (tp->thin_lto || net->ipv4.sysctl_tcp_thin_linear_timeouts) &&
582 tcp_stream_is_thin(tp) &&
583 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
584 icsk->icsk_backoff = 0;
585 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
587 /* Use normal (exponential) backoff */
588 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
590 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
591 tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX);
592 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0))
598 /* Called with bottom-half processing disabled.
599 Called by tcp_write_timer() */
600 void tcp_write_timer_handler(struct sock *sk)
602 struct inet_connection_sock *icsk = inet_csk(sk);
605 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
609 if (time_after(icsk->icsk_timeout, jiffies)) {
610 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
614 tcp_mstamp_refresh(tcp_sk(sk));
615 event = icsk->icsk_pending;
618 case ICSK_TIME_REO_TIMEOUT:
619 tcp_rack_reo_timeout(sk);
621 case ICSK_TIME_LOSS_PROBE:
622 tcp_send_loss_probe(sk);
624 case ICSK_TIME_RETRANS:
625 icsk->icsk_pending = 0;
626 tcp_retransmit_timer(sk);
628 case ICSK_TIME_PROBE0:
629 icsk->icsk_pending = 0;
638 static void tcp_write_timer(struct timer_list *t)
640 struct inet_connection_sock *icsk =
641 from_timer(icsk, t, icsk_retransmit_timer);
642 struct sock *sk = &icsk->icsk_inet.sk;
645 if (!sock_owned_by_user(sk)) {
646 tcp_write_timer_handler(sk);
648 /* delegate our work to tcp_release_cb() */
649 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags))
656 void tcp_syn_ack_timeout(const struct request_sock *req)
658 struct net *net = read_pnet(&inet_rsk(req)->ireq_net);
660 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS);
662 EXPORT_SYMBOL(tcp_syn_ack_timeout);
664 void tcp_set_keepalive(struct sock *sk, int val)
666 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
669 if (val && !sock_flag(sk, SOCK_KEEPOPEN))
670 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
672 inet_csk_delete_keepalive_timer(sk);
674 EXPORT_SYMBOL_GPL(tcp_set_keepalive);
677 static void tcp_keepalive_timer (struct timer_list *t)
679 struct sock *sk = from_timer(sk, t, sk_timer);
680 struct inet_connection_sock *icsk = inet_csk(sk);
681 struct tcp_sock *tp = tcp_sk(sk);
684 /* Only process if socket is not in use. */
686 if (sock_owned_by_user(sk)) {
687 /* Try again later. */
688 inet_csk_reset_keepalive_timer (sk, HZ/20);
692 if (sk->sk_state == TCP_LISTEN) {
693 pr_err("Hmm... keepalive on a LISTEN ???\n");
697 tcp_mstamp_refresh(tp);
698 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
699 if (tp->linger2 >= 0) {
700 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
703 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
707 tcp_send_active_reset(sk, GFP_ATOMIC);
711 if (!sock_flag(sk, SOCK_KEEPOPEN) ||
712 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT)))
715 elapsed = keepalive_time_when(tp);
717 /* It is alive without keepalive 8) */
718 if (tp->packets_out || !tcp_write_queue_empty(sk))
721 elapsed = keepalive_time_elapsed(tp);
723 if (elapsed >= keepalive_time_when(tp)) {
724 /* If the TCP_USER_TIMEOUT option is enabled, use that
725 * to determine when to timeout instead.
727 if ((icsk->icsk_user_timeout != 0 &&
728 elapsed >= msecs_to_jiffies(icsk->icsk_user_timeout) &&
729 icsk->icsk_probes_out > 0) ||
730 (icsk->icsk_user_timeout == 0 &&
731 icsk->icsk_probes_out >= keepalive_probes(tp))) {
732 tcp_send_active_reset(sk, GFP_ATOMIC);
736 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) {
737 icsk->icsk_probes_out++;
738 elapsed = keepalive_intvl_when(tp);
740 /* If keepalive was lost due to local congestion,
743 elapsed = TCP_RESOURCE_PROBE_INTERVAL;
746 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
747 elapsed = keepalive_time_when(tp) - elapsed;
753 inet_csk_reset_keepalive_timer (sk, elapsed);
764 static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer)
766 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer);
767 struct sock *sk = (struct sock *)tp;
770 if (!sock_owned_by_user(sk)) {
771 if (tp->compressed_ack) {
772 /* Since we have to send one ack finally,
773 * subtract one from tp->compressed_ack to keep
774 * LINUX_MIB_TCPACKCOMPRESSED accurate.
776 tp->compressed_ack--;
780 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
788 return HRTIMER_NORESTART;
791 void tcp_init_xmit_timers(struct sock *sk)
793 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
794 &tcp_keepalive_timer);
795 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC,
796 HRTIMER_MODE_ABS_PINNED_SOFT);
797 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick;
799 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC,
800 HRTIMER_MODE_REL_PINNED_SOFT);
801 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick;