net: remove CVS keywords
[linux-2.6] / 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(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 = atomic_read(&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(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
141         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
142                 if (icsk->icsk_retransmits)
143                         dst_negative_advice(&sk->sk_dst_cache);
144                 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
145         } else {
146                 if (icsk->icsk_retransmits >= sysctl_tcp_retries1) {
147                         /* Black hole detection */
148                         tcp_mtu_probing(icsk, sk);
149
150                         dst_negative_advice(&sk->sk_dst_cache);
151                 }
152
153                 retry_until = sysctl_tcp_retries2;
154                 if (sock_flag(sk, SOCK_DEAD)) {
155                         const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
156
157                         retry_until = tcp_orphan_retries(sk, alive);
158
159                         if (tcp_out_of_resources(sk, alive || icsk->icsk_retransmits < retry_until))
160                                 return 1;
161                 }
162         }
163
164         if (icsk->icsk_retransmits >= retry_until) {
165                 /* Has it gone just too far? */
166                 tcp_write_err(sk);
167                 return 1;
168         }
169         return 0;
170 }
171
172 static void tcp_delack_timer(unsigned long data)
173 {
174         struct sock *sk = (struct sock*)data;
175         struct tcp_sock *tp = tcp_sk(sk);
176         struct inet_connection_sock *icsk = inet_csk(sk);
177
178         bh_lock_sock(sk);
179         if (sock_owned_by_user(sk)) {
180                 /* Try again later. */
181                 icsk->icsk_ack.blocked = 1;
182                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED);
183                 sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN);
184                 goto out_unlock;
185         }
186
187         sk_mem_reclaim_partial(sk);
188
189         if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
190                 goto out;
191
192         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
193                 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
194                 goto out;
195         }
196         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
197
198         if (!skb_queue_empty(&tp->ucopy.prequeue)) {
199                 struct sk_buff *skb;
200
201                 NET_INC_STATS_BH(LINUX_MIB_TCPSCHEDULERFAILED);
202
203                 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
204                         sk->sk_backlog_rcv(sk, skb);
205
206                 tp->ucopy.memory = 0;
207         }
208
209         if (inet_csk_ack_scheduled(sk)) {
210                 if (!icsk->icsk_ack.pingpong) {
211                         /* Delayed ACK missed: inflate ATO. */
212                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
213                 } else {
214                         /* Delayed ACK missed: leave pingpong mode and
215                          * deflate ATO.
216                          */
217                         icsk->icsk_ack.pingpong = 0;
218                         icsk->icsk_ack.ato      = TCP_ATO_MIN;
219                 }
220                 tcp_send_ack(sk);
221                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKS);
222         }
223         TCP_CHECK_TIMER(sk);
224
225 out:
226         if (tcp_memory_pressure)
227                 sk_mem_reclaim(sk);
228 out_unlock:
229         bh_unlock_sock(sk);
230         sock_put(sk);
231 }
232
233 static void tcp_probe_timer(struct sock *sk)
234 {
235         struct inet_connection_sock *icsk = inet_csk(sk);
236         struct tcp_sock *tp = tcp_sk(sk);
237         int max_probes;
238
239         if (tp->packets_out || !tcp_send_head(sk)) {
240                 icsk->icsk_probes_out = 0;
241                 return;
242         }
243
244         /* *WARNING* RFC 1122 forbids this
245          *
246          * It doesn't AFAIK, because we kill the retransmit timer -AK
247          *
248          * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
249          * this behaviour in Solaris down as a bug fix. [AC]
250          *
251          * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
252          * even if they advertise zero window. Hence, connection is killed only
253          * if we received no ACKs for normal connection timeout. It is not killed
254          * only because window stays zero for some time, window may be zero
255          * until armageddon and even later. We are in full accordance
256          * with RFCs, only probe timer combines both retransmission timeout
257          * and probe timeout in one bottle.                             --ANK
258          */
259         max_probes = sysctl_tcp_retries2;
260
261         if (sock_flag(sk, SOCK_DEAD)) {
262                 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
263
264                 max_probes = tcp_orphan_retries(sk, alive);
265
266                 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
267                         return;
268         }
269
270         if (icsk->icsk_probes_out > max_probes) {
271                 tcp_write_err(sk);
272         } else {
273                 /* Only send another probe if we didn't close things up. */
274                 tcp_send_probe0(sk);
275         }
276 }
277
278 /*
279  *      The TCP retransmit timer.
280  */
281
282 static void tcp_retransmit_timer(struct sock *sk)
283 {
284         struct tcp_sock *tp = tcp_sk(sk);
285         struct inet_connection_sock *icsk = inet_csk(sk);
286
287         if (!tp->packets_out)
288                 goto out;
289
290         BUG_TRAP(!tcp_write_queue_empty(sk));
291
292         if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
293             !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
294                 /* Receiver dastardly shrinks window. Our retransmits
295                  * become zero probes, but we should not timeout this
296                  * connection. If the socket is an orphan, time it out,
297                  * we cannot allow such beasts to hang infinitely.
298                  */
299 #ifdef TCP_DEBUG
300                 struct inet_sock *inet = inet_sk(sk);
301                 if (sk->sk_family == AF_INET) {
302                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: Treason uncloaked! Peer " NIPQUAD_FMT ":%u/%u shrinks window %u:%u. Repaired.\n",
303                                NIPQUAD(inet->daddr), ntohs(inet->dport),
304                                inet->num, tp->snd_una, tp->snd_nxt);
305                 }
306 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
307                 else if (sk->sk_family == AF_INET6) {
308                         struct ipv6_pinfo *np = inet6_sk(sk);
309                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: Treason uncloaked! Peer " NIP6_FMT ":%u/%u shrinks window %u:%u. Repaired.\n",
310                                NIP6(np->daddr), ntohs(inet->dport),
311                                inet->num, tp->snd_una, tp->snd_nxt);
312                 }
313 #endif
314 #endif
315                 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
316                         tcp_write_err(sk);
317                         goto out;
318                 }
319                 tcp_enter_loss(sk, 0);
320                 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
321                 __sk_dst_reset(sk);
322                 goto out_reset_timer;
323         }
324
325         if (tcp_write_timeout(sk))
326                 goto out;
327
328         if (icsk->icsk_retransmits == 0) {
329                 if (icsk->icsk_ca_state == TCP_CA_Disorder ||
330                     icsk->icsk_ca_state == TCP_CA_Recovery) {
331                         if (tcp_is_sack(tp)) {
332                                 if (icsk->icsk_ca_state == TCP_CA_Recovery)
333                                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERYFAIL);
334                                 else
335                                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKFAILURES);
336                         } else {
337                                 if (icsk->icsk_ca_state == TCP_CA_Recovery)
338                                         NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERYFAIL);
339                                 else
340                                         NET_INC_STATS_BH(LINUX_MIB_TCPRENOFAILURES);
341                         }
342                 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
343                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSSFAILURES);
344                 } else {
345                         NET_INC_STATS_BH(LINUX_MIB_TCPTIMEOUTS);
346                 }
347         }
348
349         if (tcp_use_frto(sk)) {
350                 tcp_enter_frto(sk);
351         } else {
352                 tcp_enter_loss(sk, 0);
353         }
354
355         if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
356                 /* Retransmission failed because of local congestion,
357                  * do not backoff.
358                  */
359                 if (!icsk->icsk_retransmits)
360                         icsk->icsk_retransmits = 1;
361                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
362                                           min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
363                                           TCP_RTO_MAX);
364                 goto out;
365         }
366
367         /* Increase the timeout each time we retransmit.  Note that
368          * we do not increase the rtt estimate.  rto is initialized
369          * from rtt, but increases here.  Jacobson (SIGCOMM 88) suggests
370          * that doubling rto each time is the least we can get away with.
371          * In KA9Q, Karn uses this for the first few times, and then
372          * goes to quadratic.  netBSD doubles, but only goes up to *64,
373          * and clamps at 1 to 64 sec afterwards.  Note that 120 sec is
374          * defined in the protocol as the maximum possible RTT.  I guess
375          * we'll have to use something other than TCP to talk to the
376          * University of Mars.
377          *
378          * PAWS allows us longer timeouts and large windows, so once
379          * implemented ftp to mars will work nicely. We will have to fix
380          * the 120 second clamps though!
381          */
382         icsk->icsk_backoff++;
383         icsk->icsk_retransmits++;
384
385 out_reset_timer:
386         icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
387         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
388         if (icsk->icsk_retransmits > sysctl_tcp_retries1)
389                 __sk_dst_reset(sk);
390
391 out:;
392 }
393
394 static void tcp_write_timer(unsigned long data)
395 {
396         struct sock *sk = (struct sock*)data;
397         struct inet_connection_sock *icsk = inet_csk(sk);
398         int event;
399
400         bh_lock_sock(sk);
401         if (sock_owned_by_user(sk)) {
402                 /* Try again later */
403                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + (HZ / 20));
404                 goto out_unlock;
405         }
406
407         if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
408                 goto out;
409
410         if (time_after(icsk->icsk_timeout, jiffies)) {
411                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
412                 goto out;
413         }
414
415         event = icsk->icsk_pending;
416         icsk->icsk_pending = 0;
417
418         switch (event) {
419         case ICSK_TIME_RETRANS:
420                 tcp_retransmit_timer(sk);
421                 break;
422         case ICSK_TIME_PROBE0:
423                 tcp_probe_timer(sk);
424                 break;
425         }
426         TCP_CHECK_TIMER(sk);
427
428 out:
429         sk_mem_reclaim(sk);
430 out_unlock:
431         bh_unlock_sock(sk);
432         sock_put(sk);
433 }
434
435 /*
436  *      Timer for listening sockets
437  */
438
439 static void tcp_synack_timer(struct sock *sk)
440 {
441         inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
442                                    TCP_TIMEOUT_INIT, TCP_RTO_MAX);
443 }
444
445 void tcp_set_keepalive(struct sock *sk, int val)
446 {
447         if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
448                 return;
449
450         if (val && !sock_flag(sk, SOCK_KEEPOPEN))
451                 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
452         else if (!val)
453                 inet_csk_delete_keepalive_timer(sk);
454 }
455
456
457 static void tcp_keepalive_timer (unsigned long data)
458 {
459         struct sock *sk = (struct sock *) data;
460         struct inet_connection_sock *icsk = inet_csk(sk);
461         struct tcp_sock *tp = tcp_sk(sk);
462         __u32 elapsed;
463
464         /* Only process if socket is not in use. */
465         bh_lock_sock(sk);
466         if (sock_owned_by_user(sk)) {
467                 /* Try again later. */
468                 inet_csk_reset_keepalive_timer (sk, HZ/20);
469                 goto out;
470         }
471
472         if (sk->sk_state == TCP_LISTEN) {
473                 tcp_synack_timer(sk);
474                 goto out;
475         }
476
477         if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
478                 if (tp->linger2 >= 0) {
479                         const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
480
481                         if (tmo > 0) {
482                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
483                                 goto out;
484                         }
485                 }
486                 tcp_send_active_reset(sk, GFP_ATOMIC);
487                 goto death;
488         }
489
490         if (tp->defer_tcp_accept.request && sk->sk_state == TCP_ESTABLISHED) {
491                 tcp_send_active_reset(sk, GFP_ATOMIC);
492                 goto death;
493         }
494
495         if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
496                 goto out;
497
498         elapsed = keepalive_time_when(tp);
499
500         /* It is alive without keepalive 8) */
501         if (tp->packets_out || tcp_send_head(sk))
502                 goto resched;
503
504         elapsed = tcp_time_stamp - tp->rcv_tstamp;
505
506         if (elapsed >= keepalive_time_when(tp)) {
507                 if ((!tp->keepalive_probes && icsk->icsk_probes_out >= sysctl_tcp_keepalive_probes) ||
508                      (tp->keepalive_probes && icsk->icsk_probes_out >= tp->keepalive_probes)) {
509                         tcp_send_active_reset(sk, GFP_ATOMIC);
510                         tcp_write_err(sk);
511                         goto out;
512                 }
513                 if (tcp_write_wakeup(sk) <= 0) {
514                         icsk->icsk_probes_out++;
515                         elapsed = keepalive_intvl_when(tp);
516                 } else {
517                         /* If keepalive was lost due to local congestion,
518                          * try harder.
519                          */
520                         elapsed = TCP_RESOURCE_PROBE_INTERVAL;
521                 }
522         } else {
523                 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
524                 elapsed = keepalive_time_when(tp) - elapsed;
525         }
526
527         TCP_CHECK_TIMER(sk);
528         sk_mem_reclaim(sk);
529
530 resched:
531         inet_csk_reset_keepalive_timer (sk, elapsed);
532         goto out;
533
534 death:
535         tcp_done(sk);
536
537 out:
538         bh_unlock_sock(sk);
539         sock_put(sk);
540 }