tcp: fix possible socket refcount problem
[linux-3.10.git] / net / ipv4 / tcp_timer.c
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
25 int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES;
26 int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES;
27 int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME;
28 int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES;
29 int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
30 int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
31 int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
32 int sysctl_tcp_orphan_retries __read_mostly;
33 int sysctl_tcp_thin_linear_timeouts __read_mostly;
34
35 static 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  */
55 static 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. */
86 static 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
102 static 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  */
127 static 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. */
156 static int tcp_write_timeout(struct sock *sk)
157 {
158         struct inet_connection_sock *icsk = inet_csk(sk);
159         int retry_until;
160         bool do_reset, syn_set = false;
161
162         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
163                 if (icsk->icsk_retransmits)
164                         dst_negative_advice(sk);
165                 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
166                 syn_set = true;
167         } else {
168                 if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0, 0)) {
169                         /* Black hole detection */
170                         tcp_mtu_probing(icsk, sk);
171
172                         dst_negative_advice(sk);
173                 }
174
175                 retry_until = sysctl_tcp_retries2;
176                 if (sock_flag(sk, SOCK_DEAD)) {
177                         const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
178
179                         retry_until = tcp_orphan_retries(sk, alive);
180                         do_reset = alive ||
181                                 !retransmits_timed_out(sk, retry_until, 0, 0);
182
183                         if (tcp_out_of_resources(sk, do_reset))
184                                 return 1;
185                 }
186         }
187
188         if (retransmits_timed_out(sk, retry_until,
189                                   syn_set ? 0 : icsk->icsk_user_timeout, syn_set)) {
190                 /* Has it gone just too far? */
191                 tcp_write_err(sk);
192                 return 1;
193         }
194         return 0;
195 }
196
197 void tcp_delack_timer_handler(struct sock *sk)
198 {
199         struct tcp_sock *tp = tcp_sk(sk);
200         struct inet_connection_sock *icsk = inet_csk(sk);
201
202         sk_mem_reclaim_partial(sk);
203
204         if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
205                 goto out;
206
207         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
208                 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
209                 goto out;
210         }
211         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
212
213         if (!skb_queue_empty(&tp->ucopy.prequeue)) {
214                 struct sk_buff *skb;
215
216                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
217
218                 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
219                         sk_backlog_rcv(sk, skb);
220
221                 tp->ucopy.memory = 0;
222         }
223
224         if (inet_csk_ack_scheduled(sk)) {
225                 if (!icsk->icsk_ack.pingpong) {
226                         /* Delayed ACK missed: inflate ATO. */
227                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
228                 } else {
229                         /* Delayed ACK missed: leave pingpong mode and
230                          * deflate ATO.
231                          */
232                         icsk->icsk_ack.pingpong = 0;
233                         icsk->icsk_ack.ato      = TCP_ATO_MIN;
234                 }
235                 tcp_send_ack(sk);
236                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
237         }
238
239 out:
240         if (sk_under_memory_pressure(sk))
241                 sk_mem_reclaim(sk);
242 }
243
244 static void tcp_delack_timer(unsigned long data)
245 {
246         struct sock *sk = (struct sock *)data;
247
248         bh_lock_sock(sk);
249         if (!sock_owned_by_user(sk)) {
250                 tcp_delack_timer_handler(sk);
251         } else {
252                 inet_csk(sk)->icsk_ack.blocked = 1;
253                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
254                 /* deleguate our work to tcp_release_cb() */
255                 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
256                         sock_hold(sk);
257         }
258         bh_unlock_sock(sk);
259         sock_put(sk);
260 }
261
262 static void tcp_probe_timer(struct sock *sk)
263 {
264         struct inet_connection_sock *icsk = inet_csk(sk);
265         struct tcp_sock *tp = tcp_sk(sk);
266         int max_probes;
267
268         if (tp->packets_out || !tcp_send_head(sk)) {
269                 icsk->icsk_probes_out = 0;
270                 return;
271         }
272
273         /* *WARNING* RFC 1122 forbids this
274          *
275          * It doesn't AFAIK, because we kill the retransmit timer -AK
276          *
277          * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
278          * this behaviour in Solaris down as a bug fix. [AC]
279          *
280          * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
281          * even if they advertise zero window. Hence, connection is killed only
282          * if we received no ACKs for normal connection timeout. It is not killed
283          * only because window stays zero for some time, window may be zero
284          * until armageddon and even later. We are in full accordance
285          * with RFCs, only probe timer combines both retransmission timeout
286          * and probe timeout in one bottle.                             --ANK
287          */
288         max_probes = sysctl_tcp_retries2;
289
290         if (sock_flag(sk, SOCK_DEAD)) {
291                 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
292
293                 max_probes = tcp_orphan_retries(sk, alive);
294
295                 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
296                         return;
297         }
298
299         if (icsk->icsk_probes_out > max_probes) {
300                 tcp_write_err(sk);
301         } else {
302                 /* Only send another probe if we didn't close things up. */
303                 tcp_send_probe0(sk);
304         }
305 }
306
307 /*
308  *      The TCP retransmit timer.
309  */
310
311 void tcp_retransmit_timer(struct sock *sk)
312 {
313         struct tcp_sock *tp = tcp_sk(sk);
314         struct inet_connection_sock *icsk = inet_csk(sk);
315
316         if (tp->early_retrans_delayed) {
317                 tcp_resume_early_retransmit(sk);
318                 return;
319         }
320
321         if (!tp->packets_out)
322                 goto out;
323
324         WARN_ON(tcp_write_queue_empty(sk));
325
326         if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
327             !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
328                 /* Receiver dastardly shrinks window. Our retransmits
329                  * become zero probes, but we should not timeout this
330                  * connection. If the socket is an orphan, time it out,
331                  * we cannot allow such beasts to hang infinitely.
332                  */
333                 struct inet_sock *inet = inet_sk(sk);
334                 if (sk->sk_family == AF_INET) {
335                         LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"),
336                                        &inet->inet_daddr,
337                                        ntohs(inet->inet_dport), inet->inet_num,
338                                        tp->snd_una, tp->snd_nxt);
339                 }
340 #if IS_ENABLED(CONFIG_IPV6)
341                 else if (sk->sk_family == AF_INET6) {
342                         struct ipv6_pinfo *np = inet6_sk(sk);
343                         LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"),
344                                        &np->daddr,
345                                        ntohs(inet->inet_dport), inet->inet_num,
346                                        tp->snd_una, tp->snd_nxt);
347                 }
348 #endif
349                 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
350                         tcp_write_err(sk);
351                         goto out;
352                 }
353                 tcp_enter_loss(sk, 0);
354                 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
355                 __sk_dst_reset(sk);
356                 goto out_reset_timer;
357         }
358
359         if (tcp_write_timeout(sk))
360                 goto out;
361
362         if (icsk->icsk_retransmits == 0) {
363                 int mib_idx;
364
365                 if (icsk->icsk_ca_state == TCP_CA_Recovery) {
366                         if (tcp_is_sack(tp))
367                                 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
368                         else
369                                 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
370                 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
371                         mib_idx = LINUX_MIB_TCPLOSSFAILURES;
372                 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
373                            tp->sacked_out) {
374                         if (tcp_is_sack(tp))
375                                 mib_idx = LINUX_MIB_TCPSACKFAILURES;
376                         else
377                                 mib_idx = LINUX_MIB_TCPRENOFAILURES;
378                 } else {
379                         mib_idx = LINUX_MIB_TCPTIMEOUTS;
380                 }
381                 NET_INC_STATS_BH(sock_net(sk), mib_idx);
382         }
383
384         if (tcp_use_frto(sk)) {
385                 tcp_enter_frto(sk);
386         } else {
387                 tcp_enter_loss(sk, 0);
388         }
389
390         if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
391                 /* Retransmission failed because of local congestion,
392                  * do not backoff.
393                  */
394                 if (!icsk->icsk_retransmits)
395                         icsk->icsk_retransmits = 1;
396                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
397                                           min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
398                                           TCP_RTO_MAX);
399                 goto out;
400         }
401
402         /* Increase the timeout each time we retransmit.  Note that
403          * we do not increase the rtt estimate.  rto is initialized
404          * from rtt, but increases here.  Jacobson (SIGCOMM 88) suggests
405          * that doubling rto each time is the least we can get away with.
406          * In KA9Q, Karn uses this for the first few times, and then
407          * goes to quadratic.  netBSD doubles, but only goes up to *64,
408          * and clamps at 1 to 64 sec afterwards.  Note that 120 sec is
409          * defined in the protocol as the maximum possible RTT.  I guess
410          * we'll have to use something other than TCP to talk to the
411          * University of Mars.
412          *
413          * PAWS allows us longer timeouts and large windows, so once
414          * implemented ftp to mars will work nicely. We will have to fix
415          * the 120 second clamps though!
416          */
417         icsk->icsk_backoff++;
418         icsk->icsk_retransmits++;
419
420 out_reset_timer:
421         /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
422          * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
423          * might be increased if the stream oscillates between thin and thick,
424          * thus the old value might already be too high compared to the value
425          * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
426          * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
427          * exponential backoff behaviour to avoid continue hammering
428          * linear-timeout retransmissions into a black hole
429          */
430         if (sk->sk_state == TCP_ESTABLISHED &&
431             (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) &&
432             tcp_stream_is_thin(tp) &&
433             icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
434                 icsk->icsk_backoff = 0;
435                 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
436         } else {
437                 /* Use normal (exponential) backoff */
438                 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
439         }
440         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
441         if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1, 0, 0))
442                 __sk_dst_reset(sk);
443
444 out:;
445 }
446
447 void tcp_write_timer_handler(struct sock *sk)
448 {
449         struct inet_connection_sock *icsk = inet_csk(sk);
450         int event;
451
452         if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
453                 goto out;
454
455         if (time_after(icsk->icsk_timeout, jiffies)) {
456                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
457                 goto out;
458         }
459
460         event = icsk->icsk_pending;
461         icsk->icsk_pending = 0;
462
463         switch (event) {
464         case ICSK_TIME_RETRANS:
465                 tcp_retransmit_timer(sk);
466                 break;
467         case ICSK_TIME_PROBE0:
468                 tcp_probe_timer(sk);
469                 break;
470         }
471
472 out:
473         sk_mem_reclaim(sk);
474 }
475
476 static void tcp_write_timer(unsigned long data)
477 {
478         struct sock *sk = (struct sock *)data;
479
480         bh_lock_sock(sk);
481         if (!sock_owned_by_user(sk)) {
482                 tcp_write_timer_handler(sk);
483         } else {
484                 /* deleguate our work to tcp_release_cb() */
485                 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
486                         sock_hold(sk);
487         }
488         bh_unlock_sock(sk);
489         sock_put(sk);
490 }
491
492 /*
493  *      Timer for listening sockets
494  */
495
496 static void tcp_synack_timer(struct sock *sk)
497 {
498         inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
499                                    TCP_TIMEOUT_INIT, TCP_RTO_MAX);
500 }
501
502 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
503 {
504         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
505 }
506 EXPORT_SYMBOL(tcp_syn_ack_timeout);
507
508 void tcp_set_keepalive(struct sock *sk, int val)
509 {
510         if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
511                 return;
512
513         if (val && !sock_flag(sk, SOCK_KEEPOPEN))
514                 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
515         else if (!val)
516                 inet_csk_delete_keepalive_timer(sk);
517 }
518
519
520 static void tcp_keepalive_timer (unsigned long data)
521 {
522         struct sock *sk = (struct sock *) data;
523         struct inet_connection_sock *icsk = inet_csk(sk);
524         struct tcp_sock *tp = tcp_sk(sk);
525         u32 elapsed;
526
527         /* Only process if socket is not in use. */
528         bh_lock_sock(sk);
529         if (sock_owned_by_user(sk)) {
530                 /* Try again later. */
531                 inet_csk_reset_keepalive_timer (sk, HZ/20);
532                 goto out;
533         }
534
535         if (sk->sk_state == TCP_LISTEN) {
536                 tcp_synack_timer(sk);
537                 goto out;
538         }
539
540         if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
541                 if (tp->linger2 >= 0) {
542                         const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
543
544                         if (tmo > 0) {
545                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
546                                 goto out;
547                         }
548                 }
549                 tcp_send_active_reset(sk, GFP_ATOMIC);
550                 goto death;
551         }
552
553         if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
554                 goto out;
555
556         elapsed = keepalive_time_when(tp);
557
558         /* It is alive without keepalive 8) */
559         if (tp->packets_out || tcp_send_head(sk))
560                 goto resched;
561
562         elapsed = keepalive_time_elapsed(tp);
563
564         if (elapsed >= keepalive_time_when(tp)) {
565                 /* If the TCP_USER_TIMEOUT option is enabled, use that
566                  * to determine when to timeout instead.
567                  */
568                 if ((icsk->icsk_user_timeout != 0 &&
569                     elapsed >= icsk->icsk_user_timeout &&
570                     icsk->icsk_probes_out > 0) ||
571                     (icsk->icsk_user_timeout == 0 &&
572                     icsk->icsk_probes_out >= keepalive_probes(tp))) {
573                         tcp_send_active_reset(sk, GFP_ATOMIC);
574                         tcp_write_err(sk);
575                         goto out;
576                 }
577                 if (tcp_write_wakeup(sk) <= 0) {
578                         icsk->icsk_probes_out++;
579                         elapsed = keepalive_intvl_when(tp);
580                 } else {
581                         /* If keepalive was lost due to local congestion,
582                          * try harder.
583                          */
584                         elapsed = TCP_RESOURCE_PROBE_INTERVAL;
585                 }
586         } else {
587                 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
588                 elapsed = keepalive_time_when(tp) - elapsed;
589         }
590
591         sk_mem_reclaim(sk);
592
593 resched:
594         inet_csk_reset_keepalive_timer (sk, elapsed);
595         goto out;
596
597 death:
598         tcp_done(sk);
599
600 out:
601         bh_unlock_sock(sk);
602         sock_put(sk);
603 }
604
605 void tcp_init_xmit_timers(struct sock *sk)
606 {
607         inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
608                                   &tcp_keepalive_timer);
609 }
610 EXPORT_SYMBOL(tcp_init_xmit_timers);