igmp: Use next_net_device_rcu()
[linux-2.6.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 <net/tcp.h>
23
24 int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES;
25 int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES;
26 int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME;
27 int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES;
28 int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
29 int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
30 int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
31 int sysctl_tcp_orphan_retries __read_mostly;
32
33 static void tcp_write_timer(unsigned long);
34 static void tcp_delack_timer(unsigned long);
35 static void tcp_keepalive_timer (unsigned long data);
36
37 void tcp_init_xmit_timers(struct sock *sk)
38 {
39         inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
40                                   &tcp_keepalive_timer);
41 }
42
43 EXPORT_SYMBOL(tcp_init_xmit_timers);
44
45 static void tcp_write_err(struct sock *sk)
46 {
47         sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
48         sk->sk_error_report(sk);
49
50         tcp_done(sk);
51         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
52 }
53
54 /* Do not allow orphaned sockets to eat all our resources.
55  * This is direct violation of TCP specs, but it is required
56  * to prevent DoS attacks. It is called when a retransmission timeout
57  * or zero probe timeout occurs on orphaned socket.
58  *
59  * Criteria is still not confirmed experimentally and may change.
60  * We kill the socket, if:
61  * 1. If number of orphaned sockets exceeds an administratively configured
62  *    limit.
63  * 2. If we have strong memory pressure.
64  */
65 static int tcp_out_of_resources(struct sock *sk, int do_reset)
66 {
67         struct tcp_sock *tp = tcp_sk(sk);
68         int orphans = percpu_counter_read_positive(&tcp_orphan_count);
69
70         /* If peer does not open window for long time, or did not transmit
71          * anything for long time, penalize it. */
72         if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
73                 orphans <<= 1;
74
75         /* If some dubious ICMP arrived, penalize even more. */
76         if (sk->sk_err_soft)
77                 orphans <<= 1;
78
79         if (tcp_too_many_orphans(sk, orphans)) {
80                 if (net_ratelimit())
81                         printk(KERN_INFO "Out of socket memory\n");
82
83                 /* Catch exceptional cases, when connection requires reset.
84                  *      1. Last segment was sent recently. */
85                 if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
86                     /*  2. Window is closed. */
87                     (!tp->snd_wnd && !tp->packets_out))
88                         do_reset = 1;
89                 if (do_reset)
90                         tcp_send_active_reset(sk, GFP_ATOMIC);
91                 tcp_done(sk);
92                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
93                 return 1;
94         }
95         return 0;
96 }
97
98 /* Calculate maximal number or retries on an orphaned socket. */
99 static int tcp_orphan_retries(struct sock *sk, int alive)
100 {
101         int retries = sysctl_tcp_orphan_retries; /* May be zero. */
102
103         /* We know from an ICMP that something is wrong. */
104         if (sk->sk_err_soft && !alive)
105                 retries = 0;
106
107         /* However, if socket sent something recently, select some safe
108          * number of retries. 8 corresponds to >100 seconds with minimal
109          * RTO of 200msec. */
110         if (retries == 0 && alive)
111                 retries = 8;
112         return retries;
113 }
114
115 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
116 {
117         /* Black hole detection */
118         if (sysctl_tcp_mtu_probing) {
119                 if (!icsk->icsk_mtup.enabled) {
120                         icsk->icsk_mtup.enabled = 1;
121                         tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
122                 } else {
123                         struct tcp_sock *tp = tcp_sk(sk);
124                         int mss;
125
126                         mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
127                         mss = min(sysctl_tcp_base_mss, mss);
128                         mss = max(mss, 68 - tp->tcp_header_len);
129                         icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
130                         tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
131                 }
132         }
133 }
134
135 /* A write timeout has occurred. Process the after effects. */
136 static int tcp_write_timeout(struct sock *sk)
137 {
138         struct inet_connection_sock *icsk = inet_csk(sk);
139         int retry_until;
140         bool do_reset;
141
142         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
143                 if (icsk->icsk_retransmits)
144                         dst_negative_advice(&sk->sk_dst_cache, sk);
145                 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
146         } else {
147                 if (retransmits_timed_out(sk, sysctl_tcp_retries1)) {
148                         /* Black hole detection */
149                         tcp_mtu_probing(icsk, sk);
150
151                         dst_negative_advice(&sk->sk_dst_cache, sk);
152                 }
153
154                 retry_until = sysctl_tcp_retries2;
155                 if (sock_flag(sk, SOCK_DEAD)) {
156                         const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
157
158                         retry_until = tcp_orphan_retries(sk, alive);
159                         do_reset = alive ||
160                                    !retransmits_timed_out(sk, retry_until);
161
162                         if (tcp_out_of_resources(sk, do_reset))
163                                 return 1;
164                 }
165         }
166
167         if (retransmits_timed_out(sk, retry_until)) {
168                 /* Has it gone just too far? */
169                 tcp_write_err(sk);
170                 return 1;
171         }
172         return 0;
173 }
174
175 static void tcp_delack_timer(unsigned long data)
176 {
177         struct sock *sk = (struct sock *)data;
178         struct tcp_sock *tp = tcp_sk(sk);
179         struct inet_connection_sock *icsk = inet_csk(sk);
180
181         bh_lock_sock(sk);
182         if (sock_owned_by_user(sk)) {
183                 /* Try again later. */
184                 icsk->icsk_ack.blocked = 1;
185                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
186                 sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN);
187                 goto out_unlock;
188         }
189
190         sk_mem_reclaim_partial(sk);
191
192         if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
193                 goto out;
194
195         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
196                 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
197                 goto out;
198         }
199         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
200
201         if (!skb_queue_empty(&tp->ucopy.prequeue)) {
202                 struct sk_buff *skb;
203
204                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
205
206                 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
207                         sk_backlog_rcv(sk, skb);
208
209                 tp->ucopy.memory = 0;
210         }
211
212         if (inet_csk_ack_scheduled(sk)) {
213                 if (!icsk->icsk_ack.pingpong) {
214                         /* Delayed ACK missed: inflate ATO. */
215                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
216                 } else {
217                         /* Delayed ACK missed: leave pingpong mode and
218                          * deflate ATO.
219                          */
220                         icsk->icsk_ack.pingpong = 0;
221                         icsk->icsk_ack.ato      = TCP_ATO_MIN;
222                 }
223                 tcp_send_ack(sk);
224                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
225         }
226         TCP_CHECK_TIMER(sk);
227
228 out:
229         if (tcp_memory_pressure)
230                 sk_mem_reclaim(sk);
231 out_unlock:
232         bh_unlock_sock(sk);
233         sock_put(sk);
234 }
235
236 static void tcp_probe_timer(struct sock *sk)
237 {
238         struct inet_connection_sock *icsk = inet_csk(sk);
239         struct tcp_sock *tp = tcp_sk(sk);
240         int max_probes;
241
242         if (tp->packets_out || !tcp_send_head(sk)) {
243                 icsk->icsk_probes_out = 0;
244                 return;
245         }
246
247         /* *WARNING* RFC 1122 forbids this
248          *
249          * It doesn't AFAIK, because we kill the retransmit timer -AK
250          *
251          * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
252          * this behaviour in Solaris down as a bug fix. [AC]
253          *
254          * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
255          * even if they advertise zero window. Hence, connection is killed only
256          * if we received no ACKs for normal connection timeout. It is not killed
257          * only because window stays zero for some time, window may be zero
258          * until armageddon and even later. We are in full accordance
259          * with RFCs, only probe timer combines both retransmission timeout
260          * and probe timeout in one bottle.                             --ANK
261          */
262         max_probes = sysctl_tcp_retries2;
263
264         if (sock_flag(sk, SOCK_DEAD)) {
265                 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
266
267                 max_probes = tcp_orphan_retries(sk, alive);
268
269                 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
270                         return;
271         }
272
273         if (icsk->icsk_probes_out > max_probes) {
274                 tcp_write_err(sk);
275         } else {
276                 /* Only send another probe if we didn't close things up. */
277                 tcp_send_probe0(sk);
278         }
279 }
280
281 /*
282  *      The TCP retransmit timer.
283  */
284
285 void tcp_retransmit_timer(struct sock *sk)
286 {
287         struct tcp_sock *tp = tcp_sk(sk);
288         struct inet_connection_sock *icsk = inet_csk(sk);
289
290         if (!tp->packets_out)
291                 goto out;
292
293         WARN_ON(tcp_write_queue_empty(sk));
294
295         if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
296             !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
297                 /* Receiver dastardly shrinks window. Our retransmits
298                  * become zero probes, but we should not timeout this
299                  * connection. If the socket is an orphan, time it out,
300                  * we cannot allow such beasts to hang infinitely.
301                  */
302 #ifdef TCP_DEBUG
303                 struct inet_sock *inet = inet_sk(sk);
304                 if (sk->sk_family == AF_INET) {
305                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
306                                &inet->inet_daddr, ntohs(inet->inet_dport),
307                                inet->inet_num, tp->snd_una, tp->snd_nxt);
308                 }
309 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
310                 else if (sk->sk_family == AF_INET6) {
311                         struct ipv6_pinfo *np = inet6_sk(sk);
312                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
313                                &np->daddr, ntohs(inet->inet_dport),
314                                inet->inet_num, tp->snd_una, tp->snd_nxt);
315                 }
316 #endif
317 #endif
318                 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
319                         tcp_write_err(sk);
320                         goto out;
321                 }
322                 tcp_enter_loss(sk, 0);
323                 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
324                 __sk_dst_reset(sk);
325                 goto out_reset_timer;
326         }
327
328         if (tcp_write_timeout(sk))
329                 goto out;
330
331         if (icsk->icsk_retransmits == 0) {
332                 int mib_idx;
333
334                 if (icsk->icsk_ca_state == TCP_CA_Disorder) {
335                         if (tcp_is_sack(tp))
336                                 mib_idx = LINUX_MIB_TCPSACKFAILURES;
337                         else
338                                 mib_idx = LINUX_MIB_TCPRENOFAILURES;
339                 } else if (icsk->icsk_ca_state == TCP_CA_Recovery) {
340                         if (tcp_is_sack(tp))
341                                 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
342                         else
343                                 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
344                 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
345                         mib_idx = LINUX_MIB_TCPLOSSFAILURES;
346                 } else {
347                         mib_idx = LINUX_MIB_TCPTIMEOUTS;
348                 }
349                 NET_INC_STATS_BH(sock_net(sk), mib_idx);
350         }
351
352         if (tcp_use_frto(sk)) {
353                 tcp_enter_frto(sk);
354         } else {
355                 tcp_enter_loss(sk, 0);
356         }
357
358         if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
359                 /* Retransmission failed because of local congestion,
360                  * do not backoff.
361                  */
362                 if (!icsk->icsk_retransmits)
363                         icsk->icsk_retransmits = 1;
364                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
365                                           min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
366                                           TCP_RTO_MAX);
367                 goto out;
368         }
369
370         /* Increase the timeout each time we retransmit.  Note that
371          * we do not increase the rtt estimate.  rto is initialized
372          * from rtt, but increases here.  Jacobson (SIGCOMM 88) suggests
373          * that doubling rto each time is the least we can get away with.
374          * In KA9Q, Karn uses this for the first few times, and then
375          * goes to quadratic.  netBSD doubles, but only goes up to *64,
376          * and clamps at 1 to 64 sec afterwards.  Note that 120 sec is
377          * defined in the protocol as the maximum possible RTT.  I guess
378          * we'll have to use something other than TCP to talk to the
379          * University of Mars.
380          *
381          * PAWS allows us longer timeouts and large windows, so once
382          * implemented ftp to mars will work nicely. We will have to fix
383          * the 120 second clamps though!
384          */
385         icsk->icsk_backoff++;
386         icsk->icsk_retransmits++;
387
388 out_reset_timer:
389         icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
390         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
391         if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1))
392                 __sk_dst_reset(sk);
393
394 out:;
395 }
396
397 static void tcp_write_timer(unsigned long data)
398 {
399         struct sock *sk = (struct sock *)data;
400         struct inet_connection_sock *icsk = inet_csk(sk);
401         int event;
402
403         bh_lock_sock(sk);
404         if (sock_owned_by_user(sk)) {
405                 /* Try again later */
406                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + (HZ / 20));
407                 goto out_unlock;
408         }
409
410         if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
411                 goto out;
412
413         if (time_after(icsk->icsk_timeout, jiffies)) {
414                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
415                 goto out;
416         }
417
418         event = icsk->icsk_pending;
419         icsk->icsk_pending = 0;
420
421         switch (event) {
422         case ICSK_TIME_RETRANS:
423                 tcp_retransmit_timer(sk);
424                 break;
425         case ICSK_TIME_PROBE0:
426                 tcp_probe_timer(sk);
427                 break;
428         }
429         TCP_CHECK_TIMER(sk);
430
431 out:
432         sk_mem_reclaim(sk);
433 out_unlock:
434         bh_unlock_sock(sk);
435         sock_put(sk);
436 }
437
438 /*
439  *      Timer for listening sockets
440  */
441
442 static void tcp_synack_timer(struct sock *sk)
443 {
444         inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
445                                    TCP_TIMEOUT_INIT, TCP_RTO_MAX);
446 }
447
448 void tcp_set_keepalive(struct sock *sk, int val)
449 {
450         if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
451                 return;
452
453         if (val && !sock_flag(sk, SOCK_KEEPOPEN))
454                 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
455         else if (!val)
456                 inet_csk_delete_keepalive_timer(sk);
457 }
458
459
460 static void tcp_keepalive_timer (unsigned long data)
461 {
462         struct sock *sk = (struct sock *) data;
463         struct inet_connection_sock *icsk = inet_csk(sk);
464         struct tcp_sock *tp = tcp_sk(sk);
465         __u32 elapsed;
466
467         /* Only process if socket is not in use. */
468         bh_lock_sock(sk);
469         if (sock_owned_by_user(sk)) {
470                 /* Try again later. */
471                 inet_csk_reset_keepalive_timer (sk, HZ/20);
472                 goto out;
473         }
474
475         if (sk->sk_state == TCP_LISTEN) {
476                 tcp_synack_timer(sk);
477                 goto out;
478         }
479
480         if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
481                 if (tp->linger2 >= 0) {
482                         const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
483
484                         if (tmo > 0) {
485                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
486                                 goto out;
487                         }
488                 }
489                 tcp_send_active_reset(sk, GFP_ATOMIC);
490                 goto death;
491         }
492
493         if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
494                 goto out;
495
496         elapsed = keepalive_time_when(tp);
497
498         /* It is alive without keepalive 8) */
499         if (tp->packets_out || tcp_send_head(sk))
500                 goto resched;
501
502         elapsed = tcp_time_stamp - tp->rcv_tstamp;
503
504         if (elapsed >= keepalive_time_when(tp)) {
505                 if (icsk->icsk_probes_out >= keepalive_probes(tp)) {
506                         tcp_send_active_reset(sk, GFP_ATOMIC);
507                         tcp_write_err(sk);
508                         goto out;
509                 }
510                 if (tcp_write_wakeup(sk) <= 0) {
511                         icsk->icsk_probes_out++;
512                         elapsed = keepalive_intvl_when(tp);
513                 } else {
514                         /* If keepalive was lost due to local congestion,
515                          * try harder.
516                          */
517                         elapsed = TCP_RESOURCE_PROBE_INTERVAL;
518                 }
519         } else {
520                 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
521                 elapsed = keepalive_time_when(tp) - elapsed;
522         }
523
524         TCP_CHECK_TIMER(sk);
525         sk_mem_reclaim(sk);
526
527 resched:
528         inet_csk_reset_keepalive_timer (sk, elapsed);
529         goto out;
530
531 death:
532         tcp_done(sk);
533
534 out:
535         bh_unlock_sock(sk);
536         sock_put(sk);
537 }