~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

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

Version: ~ [ linux-5.2 ] ~ [ linux-5.1.16 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.57 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.132 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.184 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.184 ] ~ [ 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-3.16.69 ] ~ [ 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-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  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, bool 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 = true;
 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         start_ts = tcp_sk(sk)->retrans_stamp;
139         if (unlikely(!start_ts))
140                 start_ts = tcp_skb_timestamp(tcp_write_queue_head(sk));
141 
142         if (likely(timeout == 0)) {
143                 linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base);
144 
145                 if (boundary <= linear_backoff_thresh)
146                         timeout = ((2 << boundary) - 1) * rto_base;
147                 else
148                         timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +
149                                 (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
150         }
151         return (tcp_time_stamp - start_ts) >= timeout;
152 }
153 
154 /* A write timeout has occurred. Process the after effects. */
155 static int tcp_write_timeout(struct sock *sk)
156 {
157         struct inet_connection_sock *icsk = inet_csk(sk);
158         struct tcp_sock *tp = tcp_sk(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                         if (tp->syn_fastopen || tp->syn_data)
166                                 tcp_fastopen_cache_set(sk, 0, NULL, true);
167                         if (tp->syn_data)
168                                 NET_INC_STATS_BH(sock_net(sk),
169                                                  LINUX_MIB_TCPFASTOPENACTIVEFAIL);
170                 }
171                 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
172                 syn_set = true;
173         } else {
174                 if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0, 0)) {
175                         /* Black hole detection */
176                         tcp_mtu_probing(icsk, sk);
177 
178                         dst_negative_advice(sk);
179                 }
180 
181                 retry_until = sysctl_tcp_retries2;
182                 if (sock_flag(sk, SOCK_DEAD)) {
183                         const int alive = icsk->icsk_rto < TCP_RTO_MAX;
184 
185                         retry_until = tcp_orphan_retries(sk, alive);
186                         do_reset = alive ||
187                                 !retransmits_timed_out(sk, retry_until, 0, 0);
188 
189                         if (tcp_out_of_resources(sk, do_reset))
190                                 return 1;
191                 }
192         }
193 
194         if (retransmits_timed_out(sk, retry_until,
195                                   syn_set ? 0 : icsk->icsk_user_timeout, syn_set)) {
196                 /* Has it gone just too far? */
197                 tcp_write_err(sk);
198                 return 1;
199         }
200         return 0;
201 }
202 
203 void tcp_delack_timer_handler(struct sock *sk)
204 {
205         struct tcp_sock *tp = tcp_sk(sk);
206         struct inet_connection_sock *icsk = inet_csk(sk);
207 
208         sk_mem_reclaim_partial(sk);
209 
210         if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
211                 goto out;
212 
213         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
214                 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
215                 goto out;
216         }
217         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
218 
219         if (!skb_queue_empty(&tp->ucopy.prequeue)) {
220                 struct sk_buff *skb;
221 
222                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
223 
224                 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
225                         sk_backlog_rcv(sk, skb);
226 
227                 tp->ucopy.memory = 0;
228         }
229 
230         if (inet_csk_ack_scheduled(sk)) {
231                 if (!icsk->icsk_ack.pingpong) {
232                         /* Delayed ACK missed: inflate ATO. */
233                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
234                 } else {
235                         /* Delayed ACK missed: leave pingpong mode and
236                          * deflate ATO.
237                          */
238                         icsk->icsk_ack.pingpong = 0;
239                         icsk->icsk_ack.ato      = TCP_ATO_MIN;
240                 }
241                 tcp_send_ack(sk);
242                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
243         }
244 
245 out:
246         if (sk_under_memory_pressure(sk))
247                 sk_mem_reclaim(sk);
248 }
249 
250 static void tcp_delack_timer(unsigned long data)
251 {
252         struct sock *sk = (struct sock *)data;
253 
254         bh_lock_sock(sk);
255         if (!sock_owned_by_user(sk)) {
256                 tcp_delack_timer_handler(sk);
257         } else {
258                 inet_csk(sk)->icsk_ack.blocked = 1;
259                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
260                 /* deleguate our work to tcp_release_cb() */
261                 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
262                         sock_hold(sk);
263         }
264         bh_unlock_sock(sk);
265         sock_put(sk);
266 }
267 
268 static void tcp_probe_timer(struct sock *sk)
269 {
270         struct inet_connection_sock *icsk = inet_csk(sk);
271         struct tcp_sock *tp = tcp_sk(sk);
272         int max_probes;
273         u32 start_ts;
274 
275         if (tp->packets_out || !tcp_send_head(sk)) {
276                 icsk->icsk_probes_out = 0;
277                 return;
278         }
279 
280         /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as
281          * long as the receiver continues to respond probes. We support this by
282          * default and reset icsk_probes_out with incoming ACKs. But if the
283          * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we
284          * kill the socket when the retry count and the time exceeds the
285          * corresponding system limit. We also implement similar policy when
286          * we use RTO to probe window in tcp_retransmit_timer().
287          */
288         start_ts = tcp_skb_timestamp(tcp_send_head(sk));
289         if (!start_ts)
290                 skb_mstamp_get(&tcp_send_head(sk)->skb_mstamp);
291         else if (icsk->icsk_user_timeout &&
292                  (s32)(tcp_time_stamp - start_ts) > icsk->icsk_user_timeout)
293                 goto abort;
294 
295         max_probes = sysctl_tcp_retries2;
296         if (sock_flag(sk, SOCK_DEAD)) {
297                 const int alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX;
298 
299                 max_probes = tcp_orphan_retries(sk, alive);
300                 if (!alive && icsk->icsk_backoff >= max_probes)
301                         goto abort;
302                 if (tcp_out_of_resources(sk, true))
303                         return;
304         }
305 
306         if (icsk->icsk_probes_out > max_probes) {
307 abort:          tcp_write_err(sk);
308         } else {
309                 /* Only send another probe if we didn't close things up. */
310                 tcp_send_probe0(sk);
311         }
312 }
313 
314 /*
315  *      Timer for Fast Open socket to retransmit SYNACK. Note that the
316  *      sk here is the child socket, not the parent (listener) socket.
317  */
318 static void tcp_fastopen_synack_timer(struct sock *sk)
319 {
320         struct inet_connection_sock *icsk = inet_csk(sk);
321         int max_retries = icsk->icsk_syn_retries ? :
322             sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
323         struct request_sock *req;
324 
325         req = tcp_sk(sk)->fastopen_rsk;
326         req->rsk_ops->syn_ack_timeout(sk, req);
327 
328         if (req->num_timeout >= max_retries) {
329                 tcp_write_err(sk);
330                 return;
331         }
332         /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
333          * returned from rtx_syn_ack() to make it more persistent like
334          * regular retransmit because if the child socket has been accepted
335          * it's not good to give up too easily.
336          */
337         inet_rtx_syn_ack(sk, req);
338         req->num_timeout++;
339         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
340                           TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
341 }
342 
343 /*
344  *      The TCP retransmit timer.
345  */
346 
347 void tcp_retransmit_timer(struct sock *sk)
348 {
349         struct tcp_sock *tp = tcp_sk(sk);
350         struct inet_connection_sock *icsk = inet_csk(sk);
351 
352         if (tp->fastopen_rsk) {
353                 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
354                              sk->sk_state != TCP_FIN_WAIT1);
355                 tcp_fastopen_synack_timer(sk);
356                 /* Before we receive ACK to our SYN-ACK don't retransmit
357                  * anything else (e.g., data or FIN segments).
358                  */
359                 return;
360         }
361         if (!tp->packets_out)
362                 goto out;
363 
364         WARN_ON(tcp_write_queue_empty(sk));
365 
366         tp->tlp_high_seq = 0;
367 
368         if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
369             !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
370                 /* Receiver dastardly shrinks window. Our retransmits
371                  * become zero probes, but we should not timeout this
372                  * connection. If the socket is an orphan, time it out,
373                  * we cannot allow such beasts to hang infinitely.
374                  */
375                 struct inet_sock *inet = inet_sk(sk);
376                 if (sk->sk_family == AF_INET) {
377                         net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
378                                             &inet->inet_daddr,
379                                             ntohs(inet->inet_dport),
380                                             inet->inet_num,
381                                             tp->snd_una, tp->snd_nxt);
382                 }
383 #if IS_ENABLED(CONFIG_IPV6)
384                 else if (sk->sk_family == AF_INET6) {
385                         net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
386                                             &sk->sk_v6_daddr,
387                                             ntohs(inet->inet_dport),
388                                             inet->inet_num,
389                                             tp->snd_una, tp->snd_nxt);
390                 }
391 #endif
392                 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
393                         tcp_write_err(sk);
394                         goto out;
395                 }
396                 tcp_enter_loss(sk);
397                 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
398                 __sk_dst_reset(sk);
399                 goto out_reset_timer;
400         }
401 
402         if (tcp_write_timeout(sk))
403                 goto out;
404 
405         if (icsk->icsk_retransmits == 0) {
406                 int mib_idx;
407 
408                 if (icsk->icsk_ca_state == TCP_CA_Recovery) {
409                         if (tcp_is_sack(tp))
410                                 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
411                         else
412                                 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
413                 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
414                         mib_idx = LINUX_MIB_TCPLOSSFAILURES;
415                 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) ||
416                            tp->sacked_out) {
417                         if (tcp_is_sack(tp))
418                                 mib_idx = LINUX_MIB_TCPSACKFAILURES;
419                         else
420                                 mib_idx = LINUX_MIB_TCPRENOFAILURES;
421                 } else {
422                         mib_idx = LINUX_MIB_TCPTIMEOUTS;
423                 }
424                 NET_INC_STATS_BH(sock_net(sk), mib_idx);
425         }
426 
427         tcp_enter_loss(sk);
428 
429         if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
430                 /* Retransmission failed because of local congestion,
431                  * do not backoff.
432                  */
433                 if (!icsk->icsk_retransmits)
434                         icsk->icsk_retransmits = 1;
435                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
436                                           min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
437                                           TCP_RTO_MAX);
438                 goto out;
439         }
440 
441         /* Increase the timeout each time we retransmit.  Note that
442          * we do not increase the rtt estimate.  rto is initialized
443          * from rtt, but increases here.  Jacobson (SIGCOMM 88) suggests
444          * that doubling rto each time is the least we can get away with.
445          * In KA9Q, Karn uses this for the first few times, and then
446          * goes to quadratic.  netBSD doubles, but only goes up to *64,
447          * and clamps at 1 to 64 sec afterwards.  Note that 120 sec is
448          * defined in the protocol as the maximum possible RTT.  I guess
449          * we'll have to use something other than TCP to talk to the
450          * University of Mars.
451          *
452          * PAWS allows us longer timeouts and large windows, so once
453          * implemented ftp to mars will work nicely. We will have to fix
454          * the 120 second clamps though!
455          */
456         icsk->icsk_backoff++;
457         icsk->icsk_retransmits++;
458 
459 out_reset_timer:
460         /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
461          * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
462          * might be increased if the stream oscillates between thin and thick,
463          * thus the old value might already be too high compared to the value
464          * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
465          * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating
466          * exponential backoff behaviour to avoid continue hammering
467          * linear-timeout retransmissions into a black hole
468          */
469         if (sk->sk_state == TCP_ESTABLISHED &&
470             (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) &&
471             tcp_stream_is_thin(tp) &&
472             icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
473                 icsk->icsk_backoff = 0;
474                 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
475         } else {
476                 /* Use normal (exponential) backoff */
477                 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
478         }
479         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
480         if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1, 0, 0))
481                 __sk_dst_reset(sk);
482 
483 out:;
484 }
485 
486 void tcp_write_timer_handler(struct sock *sk)
487 {
488         struct inet_connection_sock *icsk = inet_csk(sk);
489         int event;
490 
491         if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
492                 goto out;
493 
494         if (time_after(icsk->icsk_timeout, jiffies)) {
495                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
496                 goto out;
497         }
498 
499         event = icsk->icsk_pending;
500 
501         switch (event) {
502         case ICSK_TIME_EARLY_RETRANS:
503                 tcp_resume_early_retransmit(sk);
504                 break;
505         case ICSK_TIME_LOSS_PROBE:
506                 tcp_send_loss_probe(sk);
507                 break;
508         case ICSK_TIME_RETRANS:
509                 icsk->icsk_pending = 0;
510                 tcp_retransmit_timer(sk);
511                 break;
512         case ICSK_TIME_PROBE0:
513                 icsk->icsk_pending = 0;
514                 tcp_probe_timer(sk);
515                 break;
516         }
517 
518 out:
519         sk_mem_reclaim(sk);
520 }
521 
522 static void tcp_write_timer(unsigned long data)
523 {
524         struct sock *sk = (struct sock *)data;
525 
526         bh_lock_sock(sk);
527         if (!sock_owned_by_user(sk)) {
528                 tcp_write_timer_handler(sk);
529         } else {
530                 /* deleguate our work to tcp_release_cb() */
531                 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
532                         sock_hold(sk);
533         }
534         bh_unlock_sock(sk);
535         sock_put(sk);
536 }
537 
538 /*
539  *      Timer for listening sockets
540  */
541 
542 static void tcp_synack_timer(struct sock *sk)
543 {
544         inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
545                                    TCP_TIMEOUT_INIT, TCP_RTO_MAX);
546 }
547 
548 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
549 {
550         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
551 }
552 EXPORT_SYMBOL(tcp_syn_ack_timeout);
553 
554 void tcp_set_keepalive(struct sock *sk, int val)
555 {
556         if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
557                 return;
558 
559         if (val && !sock_flag(sk, SOCK_KEEPOPEN))
560                 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
561         else if (!val)
562                 inet_csk_delete_keepalive_timer(sk);
563 }
564 
565 
566 static void tcp_keepalive_timer (unsigned long data)
567 {
568         struct sock *sk = (struct sock *) data;
569         struct inet_connection_sock *icsk = inet_csk(sk);
570         struct tcp_sock *tp = tcp_sk(sk);
571         u32 elapsed;
572 
573         /* Only process if socket is not in use. */
574         bh_lock_sock(sk);
575         if (sock_owned_by_user(sk)) {
576                 /* Try again later. */
577                 inet_csk_reset_keepalive_timer (sk, HZ/20);
578                 goto out;
579         }
580 
581         if (sk->sk_state == TCP_LISTEN) {
582                 tcp_synack_timer(sk);
583                 goto out;
584         }
585 
586         if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
587                 if (tp->linger2 >= 0) {
588                         const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
589 
590                         if (tmo > 0) {
591                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
592                                 goto out;
593                         }
594                 }
595                 tcp_send_active_reset(sk, GFP_ATOMIC);
596                 goto death;
597         }
598 
599         if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
600                 goto out;
601 
602         elapsed = keepalive_time_when(tp);
603 
604         /* It is alive without keepalive 8) */
605         if (tp->packets_out || tcp_send_head(sk))
606                 goto resched;
607 
608         elapsed = keepalive_time_elapsed(tp);
609 
610         if (elapsed >= keepalive_time_when(tp)) {
611                 /* If the TCP_USER_TIMEOUT option is enabled, use that
612                  * to determine when to timeout instead.
613                  */
614                 if ((icsk->icsk_user_timeout != 0 &&
615                     elapsed >= icsk->icsk_user_timeout &&
616                     icsk->icsk_probes_out > 0) ||
617                     (icsk->icsk_user_timeout == 0 &&
618                     icsk->icsk_probes_out >= keepalive_probes(tp))) {
619                         tcp_send_active_reset(sk, GFP_ATOMIC);
620                         tcp_write_err(sk);
621                         goto out;
622                 }
623                 if (tcp_write_wakeup(sk) <= 0) {
624                         icsk->icsk_probes_out++;
625                         elapsed = keepalive_intvl_when(tp);
626                 } else {
627                         /* If keepalive was lost due to local congestion,
628                          * try harder.
629                          */
630                         elapsed = TCP_RESOURCE_PROBE_INTERVAL;
631                 }
632         } else {
633                 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
634                 elapsed = keepalive_time_when(tp) - elapsed;
635         }
636 
637         sk_mem_reclaim(sk);
638 
639 resched:
640         inet_csk_reset_keepalive_timer (sk, elapsed);
641         goto out;
642 
643 death:
644         tcp_done(sk);
645 
646 out:
647         bh_unlock_sock(sk);
648         sock_put(sk);
649 }
650 
651 void tcp_init_xmit_timers(struct sock *sk)
652 {
653         inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
654                                   &tcp_keepalive_timer);
655 }
656 EXPORT_SYMBOL(tcp_init_xmit_timers);
657 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp