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TOMOYO Linux Cross Reference
Linux/net/ipv4/tcp_timer.c

Version: ~ [ linux-5.6-rc1 ] ~ [ linux-5.5.2 ] ~ [ linux-5.4.17 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.102 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.170 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.213 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.213 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.81 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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  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         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                 }
169                 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
170                 syn_set = true;
171         } else {
172                 if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0, 0)) {
173                         /* Black hole detection */
174                         tcp_mtu_probing(icsk, sk);
175 
176                         dst_negative_advice(sk);
177                 }
178 
179                 retry_until = sysctl_tcp_retries2;
180                 if (sock_flag(sk, SOCK_DEAD)) {
181                         const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
182 
183                         retry_until = tcp_orphan_retries(sk, alive);
184                         do_reset = alive ||
185                                 !retransmits_timed_out(sk, retry_until, 0, 0);
186 
187                         if (tcp_out_of_resources(sk, do_reset))
188                                 return 1;
189                 }
190         }
191 
192         if (retransmits_timed_out(sk, retry_until,
193                                   syn_set ? 0 : icsk->icsk_user_timeout, syn_set)) {
194                 /* Has it gone just too far? */
195                 tcp_write_err(sk);
196                 return 1;
197         }
198         return 0;
199 }
200 
201 void tcp_delack_timer_handler(struct sock *sk)
202 {
203         struct tcp_sock *tp = tcp_sk(sk);
204         struct inet_connection_sock *icsk = inet_csk(sk);
205 
206         sk_mem_reclaim_partial(sk);
207 
208         if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
209                 goto out;
210 
211         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
212                 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
213                 goto out;
214         }
215         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
216 
217         if (!skb_queue_empty(&tp->ucopy.prequeue)) {
218                 struct sk_buff *skb;
219 
220                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
221 
222                 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
223                         sk_backlog_rcv(sk, skb);
224 
225                 tp->ucopy.memory = 0;
226         }
227 
228         if (inet_csk_ack_scheduled(sk)) {
229                 if (!icsk->icsk_ack.pingpong) {
230                         /* Delayed ACK missed: inflate ATO. */
231                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
232                 } else {
233                         /* Delayed ACK missed: leave pingpong mode and
234                          * deflate ATO.
235                          */
236                         icsk->icsk_ack.pingpong = 0;
237                         icsk->icsk_ack.ato      = TCP_ATO_MIN;
238                 }
239                 tcp_send_ack(sk);
240                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
241         }
242 
243 out:
244         if (sk_under_memory_pressure(sk))
245                 sk_mem_reclaim(sk);
246 }
247 
248 static void tcp_delack_timer(unsigned long data)
249 {
250         struct sock *sk = (struct sock *)data;
251 
252         bh_lock_sock(sk);
253         if (!sock_owned_by_user(sk)) {
254                 tcp_delack_timer_handler(sk);
255         } else {
256                 inet_csk(sk)->icsk_ack.blocked = 1;
257                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
258                 /* deleguate our work to tcp_release_cb() */
259                 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
260                         sock_hold(sk);
261         }
262         bh_unlock_sock(sk);
263         sock_put(sk);
264 }
265 
266 static void tcp_probe_timer(struct sock *sk)
267 {
268         struct inet_connection_sock *icsk = inet_csk(sk);
269         struct tcp_sock *tp = tcp_sk(sk);
270         int max_probes;
271 
272         if (tp->packets_out || !tcp_send_head(sk)) {
273                 icsk->icsk_probes_out = 0;
274                 return;
275         }
276 
277         /* *WARNING* RFC 1122 forbids this
278          *
279          * It doesn't AFAIK, because we kill the retransmit timer -AK
280          *
281          * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
282          * this behaviour in Solaris down as a bug fix. [AC]
283          *
284          * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
285          * even if they advertise zero window. Hence, connection is killed only
286          * if we received no ACKs for normal connection timeout. It is not killed
287          * only because window stays zero for some time, window may be zero
288          * until armageddon and even later. We are in full accordance
289          * with RFCs, only probe timer combines both retransmission timeout
290          * and probe timeout in one bottle.                             --ANK
291          */
292         max_probes = sysctl_tcp_retries2;
293 
294         if (sock_flag(sk, SOCK_DEAD)) {
295                 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
296 
297                 max_probes = tcp_orphan_retries(sk, alive);
298 
299                 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
300                         return;
301         }
302 
303         if (icsk->icsk_probes_out > max_probes) {
304                 tcp_write_err(sk);
305         } else {
306                 /* Only send another probe if we didn't close things up. */
307                 tcp_send_probe0(sk);
308         }
309 }
310 
311 /*
312  *      Timer for Fast Open socket to retransmit SYNACK. Note that the
313  *      sk here is the child socket, not the parent (listener) socket.
314  */
315 static void tcp_fastopen_synack_timer(struct sock *sk)
316 {
317         struct inet_connection_sock *icsk = inet_csk(sk);
318         int max_retries = icsk->icsk_syn_retries ? :
319             sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
320         struct request_sock *req;
321 
322         req = tcp_sk(sk)->fastopen_rsk;
323         req->rsk_ops->syn_ack_timeout(sk, req);
324 
325         if (req->num_timeout >= max_retries) {
326                 tcp_write_err(sk);
327                 return;
328         }
329         /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
330          * returned from rtx_syn_ack() to make it more persistent like
331          * regular retransmit because if the child socket has been accepted
332          * it's not good to give up too easily.
333          */
334         inet_rtx_syn_ack(sk, req);
335         req->num_timeout++;
336         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
337                           TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
338 }
339 
340 /*
341  *      The TCP retransmit timer.
342  */
343 
344 void tcp_retransmit_timer(struct sock *sk)
345 {
346         struct tcp_sock *tp = tcp_sk(sk);
347         struct inet_connection_sock *icsk = inet_csk(sk);
348 
349         if (tp->fastopen_rsk) {
350                 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
351                              sk->sk_state != TCP_FIN_WAIT1);
352                 tcp_fastopen_synack_timer(sk);
353                 /* Before we receive ACK to our SYN-ACK don't retransmit
354                  * anything else (e.g., data or FIN segments).
355                  */
356                 return;
357         }
358         if (!tp->packets_out)
359                 goto out;
360 
361         WARN_ON(tcp_write_queue_empty(sk));
362 
363         tp->tlp_high_seq = 0;
364 
365         if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
366             !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
367                 /* Receiver dastardly shrinks window. Our retransmits
368                  * become zero probes, but we should not timeout this
369                  * connection. If the socket is an orphan, time it out,
370                  * we cannot allow such beasts to hang infinitely.
371                  */
372                 struct inet_sock *inet = inet_sk(sk);
373                 if (sk->sk_family == AF_INET) {
374                         LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"),
375                                        &inet->inet_daddr,
376                                        ntohs(inet->inet_dport), inet->inet_num,
377                                        tp->snd_una, tp->snd_nxt);
378                 }
379 #if IS_ENABLED(CONFIG_IPV6)
380                 else if (sk->sk_family == AF_INET6) {
381                         LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"),
382                                        &sk->sk_v6_daddr,
383                                        ntohs(inet->inet_dport), inet->inet_num,
384                                        tp->snd_una, tp->snd_nxt);
385                 }
386 #endif
387                 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
388                         tcp_write_err(sk);
389                         goto out;
390                 }
391                 tcp_enter_loss(sk, 0);
392                 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
393                 __sk_dst_reset(sk);
394                 goto out_reset_timer;
395         }
396 
397         if (tcp_write_timeout(sk))
398                 goto out;
399 
400         if (icsk->icsk_retransmits == 0) {
401                 int mib_idx;
402 
403                 if (icsk->icsk_ca_state == TCP_CA_Recovery) {
404                         if (tcp_is_sack(tp))
405                                 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
406                         else
407                                 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
408                 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
409                         mib_idx = LINUX_MIB_TCPLOSSFAILURES;
410                 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
411                            tp->sacked_out) {
412                         if (tcp_is_sack(tp))
413                                 mib_idx = LINUX_MIB_TCPSACKFAILURES;
414                         else
415                                 mib_idx = LINUX_MIB_TCPRENOFAILURES;
416                 } else {
417                         mib_idx = LINUX_MIB_TCPTIMEOUTS;
418                 }
419                 NET_INC_STATS_BH(sock_net(sk), mib_idx);
420         }
421 
422         tcp_enter_loss(sk, 0);
423 
424         if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
425                 /* Retransmission failed because of local congestion,
426                  * do not backoff.
427                  */
428                 if (!icsk->icsk_retransmits)
429                         icsk->icsk_retransmits = 1;
430                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
431                                           min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
432                                           TCP_RTO_MAX);
433                 goto out;
434         }
435 
436         /* Increase the timeout each time we retransmit.  Note that
437          * we do not increase the rtt estimate.  rto is initialized
438          * from rtt, but increases here.  Jacobson (SIGCOMM 88) suggests
439          * that doubling rto each time is the least we can get away with.
440          * In KA9Q, Karn uses this for the first few times, and then
441          * goes to quadratic.  netBSD doubles, but only goes up to *64,
442          * and clamps at 1 to 64 sec afterwards.  Note that 120 sec is
443          * defined in the protocol as the maximum possible RTT.  I guess
444          * we'll have to use something other than TCP to talk to the
445          * University of Mars.
446          *
447          * PAWS allows us longer timeouts and large windows, so once
448          * implemented ftp to mars will work nicely. We will have to fix
449          * the 120 second clamps though!
450          */
451         icsk->icsk_backoff++;
452         icsk->icsk_retransmits++;
453 
454 out_reset_timer:
455         /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
456          * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
457          * might be increased if the stream oscillates between thin and thick,
458          * thus the old value might already be too high compared to the value
459          * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
460          * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
461          * exponential backoff behaviour to avoid continue hammering
462          * linear-timeout retransmissions into a black hole
463          */
464         if (sk->sk_state == TCP_ESTABLISHED &&
465             (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) &&
466             tcp_stream_is_thin(tp) &&
467             icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
468                 icsk->icsk_backoff = 0;
469                 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
470         } else {
471                 /* Use normal (exponential) backoff */
472                 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
473         }
474         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
475         if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1, 0, 0))
476                 __sk_dst_reset(sk);
477 
478 out:;
479 }
480 
481 void tcp_write_timer_handler(struct sock *sk)
482 {
483         struct inet_connection_sock *icsk = inet_csk(sk);
484         int event;
485 
486         if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
487                 goto out;
488 
489         if (time_after(icsk->icsk_timeout, jiffies)) {
490                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
491                 goto out;
492         }
493 
494         event = icsk->icsk_pending;
495 
496         switch (event) {
497         case ICSK_TIME_EARLY_RETRANS:
498                 tcp_resume_early_retransmit(sk);
499                 break;
500         case ICSK_TIME_LOSS_PROBE:
501                 tcp_send_loss_probe(sk);
502                 break;
503         case ICSK_TIME_RETRANS:
504                 icsk->icsk_pending = 0;
505                 tcp_retransmit_timer(sk);
506                 break;
507         case ICSK_TIME_PROBE0:
508                 icsk->icsk_pending = 0;
509                 tcp_probe_timer(sk);
510                 break;
511         }
512 
513 out:
514         sk_mem_reclaim(sk);
515 }
516 
517 static void tcp_write_timer(unsigned long data)
518 {
519         struct sock *sk = (struct sock *)data;
520 
521         bh_lock_sock(sk);
522         if (!sock_owned_by_user(sk)) {
523                 tcp_write_timer_handler(sk);
524         } else {
525                 /* deleguate our work to tcp_release_cb() */
526                 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
527                         sock_hold(sk);
528         }
529         bh_unlock_sock(sk);
530         sock_put(sk);
531 }
532 
533 /*
534  *      Timer for listening sockets
535  */
536 
537 static void tcp_synack_timer(struct sock *sk)
538 {
539         inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
540                                    TCP_TIMEOUT_INIT, TCP_RTO_MAX);
541 }
542 
543 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
544 {
545         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
546 }
547 EXPORT_SYMBOL(tcp_syn_ack_timeout);
548 
549 void tcp_set_keepalive(struct sock *sk, int val)
550 {
551         if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
552                 return;
553 
554         if (val && !sock_flag(sk, SOCK_KEEPOPEN))
555                 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
556         else if (!val)
557                 inet_csk_delete_keepalive_timer(sk);
558 }
559 
560 
561 static void tcp_keepalive_timer (unsigned long data)
562 {
563         struct sock *sk = (struct sock *) data;
564         struct inet_connection_sock *icsk = inet_csk(sk);
565         struct tcp_sock *tp = tcp_sk(sk);
566         u32 elapsed;
567 
568         /* Only process if socket is not in use. */
569         bh_lock_sock(sk);
570         if (sock_owned_by_user(sk)) {
571                 /* Try again later. */
572                 inet_csk_reset_keepalive_timer (sk, HZ/20);
573                 goto out;
574         }
575 
576         if (sk->sk_state == TCP_LISTEN) {
577                 tcp_synack_timer(sk);
578                 goto out;
579         }
580 
581         if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
582                 if (tp->linger2 >= 0) {
583                         const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
584 
585                         if (tmo > 0) {
586                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
587                                 goto out;
588                         }
589                 }
590                 tcp_send_active_reset(sk, GFP_ATOMIC);
591                 goto death;
592         }
593 
594         if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
595                 goto out;
596 
597         elapsed = keepalive_time_when(tp);
598 
599         /* It is alive without keepalive 8) */
600         if (tp->packets_out || tcp_send_head(sk))
601                 goto resched;
602 
603         elapsed = keepalive_time_elapsed(tp);
604 
605         if (elapsed >= keepalive_time_when(tp)) {
606                 /* If the TCP_USER_TIMEOUT option is enabled, use that
607                  * to determine when to timeout instead.
608                  */
609                 if ((icsk->icsk_user_timeout != 0 &&
610                     elapsed >= icsk->icsk_user_timeout &&
611                     icsk->icsk_probes_out > 0) ||
612                     (icsk->icsk_user_timeout == 0 &&
613                     icsk->icsk_probes_out >= keepalive_probes(tp))) {
614                         tcp_send_active_reset(sk, GFP_ATOMIC);
615                         tcp_write_err(sk);
616                         goto out;
617                 }
618                 if (tcp_write_wakeup(sk) <= 0) {
619                         icsk->icsk_probes_out++;
620                         elapsed = keepalive_intvl_when(tp);
621                 } else {
622                         /* If keepalive was lost due to local congestion,
623                          * try harder.
624                          */
625                         elapsed = TCP_RESOURCE_PROBE_INTERVAL;
626                 }
627         } else {
628                 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
629                 elapsed = keepalive_time_when(tp) - elapsed;
630         }
631 
632         sk_mem_reclaim(sk);
633 
634 resched:
635         inet_csk_reset_keepalive_timer (sk, elapsed);
636         goto out;
637 
638 death:
639         tcp_done(sk);
640 
641 out:
642         bh_unlock_sock(sk);
643         sock_put(sk);
644 }
645 
646 void tcp_init_xmit_timers(struct sock *sk)
647 {
648         inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
649                                   &tcp_keepalive_timer);
650 }
651 EXPORT_SYMBOL(tcp_init_xmit_timers);
652 

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