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 * Version: $Id: tcp_timer.c,v 1.88 2002/02/01 22:01:04 davem Exp $
9 *
10 * Authors: Ross Biro
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Mark Evans, <evansmp@uhura.aston.ac.uk>
13 * Corey Minyard <wf-rch!minyard@relay.EU.net>
14 * Florian La Roche, <flla@stud.uni-sb.de>
15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16 * Linus Torvalds, <torvalds@cs.helsinki.fi>
17 * Alan Cox, <gw4pts@gw4pts.ampr.org>
18 * Matthew Dillon, <dillon@apollo.west.oic.com>
19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20 * Jorge Cwik, <jorge@laser.satlink.net>
21 */
22
23 #include <linux/module.h>
24 #include <net/tcp.h>
25
26 int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES;
27 int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES;
28 int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME;
29 int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES;
30 int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
31 int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
32 int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
33 int sysctl_tcp_orphan_retries __read_mostly;
34
35 static void tcp_write_timer(unsigned long);
36 static void tcp_delack_timer(unsigned long);
37 static void tcp_keepalive_timer (unsigned long data);
38
39 void tcp_init_xmit_timers(struct sock *sk)
40 {
41 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
42 &tcp_keepalive_timer);
43 }
44
45 EXPORT_SYMBOL(tcp_init_xmit_timers);
46
47 static void tcp_write_err(struct sock *sk)
48 {
49 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
50 sk->sk_error_report(sk);
51
52 tcp_done(sk);
53 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONTIMEOUT);
54 }
55
56 /* Do not allow orphaned sockets to eat all our resources.
57 * This is direct violation of TCP specs, but it is required
58 * to prevent DoS attacks. It is called when a retransmission timeout
59 * or zero probe timeout occurs on orphaned socket.
60 *
61 * Criteria is still not confirmed experimentally and may change.
62 * We kill the socket, if:
63 * 1. If number of orphaned sockets exceeds an administratively configured
64 * limit.
65 * 2. If we have strong memory pressure.
66 */
67 static int tcp_out_of_resources(struct sock *sk, int do_reset)
68 {
69 struct tcp_sock *tp = tcp_sk(sk);
70 int orphans = atomic_read(&tcp_orphan_count);
71
72 /* If peer does not open window for long time, or did not transmit
73 * anything for long time, penalize it. */
74 if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
75 orphans <<= 1;
76
77 /* If some dubious ICMP arrived, penalize even more. */
78 if (sk->sk_err_soft)
79 orphans <<= 1;
80
81 if (tcp_too_many_orphans(sk, orphans)) {
82 if (net_ratelimit())
83 printk(KERN_INFO "Out of socket memory\n");
84
85 /* Catch exceptional cases, when connection requires reset.
86 * 1. Last segment was sent recently. */
87 if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
88 /* 2. Window is closed. */
89 (!tp->snd_wnd && !tp->packets_out))
90 do_reset = 1;
91 if (do_reset)
92 tcp_send_active_reset(sk, GFP_ATOMIC);
93 tcp_done(sk);
94 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONMEMORY);
95 return 1;
96 }
97 return 0;
98 }
99
100 /* Calculate maximal number or retries on an orphaned socket. */
101 static int tcp_orphan_retries(struct sock *sk, int alive)
102 {
103 int retries = sysctl_tcp_orphan_retries; /* May be zero. */
104
105 /* We know from an ICMP that something is wrong. */
106 if (sk->sk_err_soft && !alive)
107 retries = 0;
108
109 /* However, if socket sent something recently, select some safe
110 * number of retries. 8 corresponds to >100 seconds with minimal
111 * RTO of 200msec. */
112 if (retries == 0 && alive)
113 retries = 8;
114 return retries;
115 }
116
117 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
118 {
119 /* Black hole detection */
120 if (sysctl_tcp_mtu_probing) {
121 if (!icsk->icsk_mtup.enabled) {
122 icsk->icsk_mtup.enabled = 1;
123 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
124 } else {
125 struct tcp_sock *tp = tcp_sk(sk);
126 int mss;
127
128 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
129 mss = min(sysctl_tcp_base_mss, mss);
130 mss = max(mss, 68 - tp->tcp_header_len);
131 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
132 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
133 }
134 }
135 }
136
137 /* A write timeout has occurred. Process the after effects. */
138 static int tcp_write_timeout(struct sock *sk)
139 {
140 struct inet_connection_sock *icsk = inet_csk(sk);
141 int retry_until;
142
143 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
144 if (icsk->icsk_retransmits)
145 dst_negative_advice(&sk->sk_dst_cache);
146 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
147 } else {
148 if (icsk->icsk_retransmits >= sysctl_tcp_retries1) {
149 /* Black hole detection */
150 tcp_mtu_probing(icsk, sk);
151
152 dst_negative_advice(&sk->sk_dst_cache);
153 }
154
155 retry_until = sysctl_tcp_retries2;
156 if (sock_flag(sk, SOCK_DEAD)) {
157 const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
158
159 retry_until = tcp_orphan_retries(sk, alive);
160
161 if (tcp_out_of_resources(sk, alive || icsk->icsk_retransmits < retry_until))
162 return 1;
163 }
164 }
165
166 if (icsk->icsk_retransmits >= retry_until) {
167 /* Has it gone just too far? */
168 tcp_write_err(sk);
169 return 1;
170 }
171 return 0;
172 }
173
174 static void tcp_delack_timer(unsigned long data)
175 {
176 struct sock *sk = (struct sock*)data;
177 struct tcp_sock *tp = tcp_sk(sk);
178 struct inet_connection_sock *icsk = inet_csk(sk);
179
180 bh_lock_sock(sk);
181 if (sock_owned_by_user(sk)) {
182 /* Try again later. */
183 icsk->icsk_ack.blocked = 1;
184 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED);
185 sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN);
186 goto out_unlock;
187 }
188
189 sk_mem_reclaim_partial(sk);
190
191 if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
192 goto out;
193
194 if (time_after(icsk->icsk_ack.timeout, jiffies)) {
195 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
196 goto out;
197 }
198 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
199
200 if (!skb_queue_empty(&tp->ucopy.prequeue)) {
201 struct sk_buff *skb;
202
203 NET_INC_STATS_BH(LINUX_MIB_TCPSCHEDULERFAILED);
204
205 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
206 sk->sk_backlog_rcv(sk, skb);
207
208 tp->ucopy.memory = 0;
209 }
210
211 if (inet_csk_ack_scheduled(sk)) {
212 if (!icsk->icsk_ack.pingpong) {
213 /* Delayed ACK missed: inflate ATO. */
214 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
215 } else {
216 /* Delayed ACK missed: leave pingpong mode and
217 * deflate ATO.
218 */
219 icsk->icsk_ack.pingpong = 0;
220 icsk->icsk_ack.ato = TCP_ATO_MIN;
221 }
222 tcp_send_ack(sk);
223 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKS);
224 }
225 TCP_CHECK_TIMER(sk);
226
227 out:
228 if (tcp_memory_pressure)
229 sk_mem_reclaim(sk);
230 out_unlock:
231 bh_unlock_sock(sk);
232 sock_put(sk);
233 }
234
235 static void tcp_probe_timer(struct sock *sk)
236 {
237 struct inet_connection_sock *icsk = inet_csk(sk);
238 struct tcp_sock *tp = tcp_sk(sk);
239 int max_probes;
240
241 if (tp->packets_out || !tcp_send_head(sk)) {
242 icsk->icsk_probes_out = 0;
243 return;
244 }
245
246 /* *WARNING* RFC 1122 forbids this
247 *
248 * It doesn't AFAIK, because we kill the retransmit timer -AK
249 *
250 * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
251 * this behaviour in Solaris down as a bug fix. [AC]
252 *
253 * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
254 * even if they advertise zero window. Hence, connection is killed only
255 * if we received no ACKs for normal connection timeout. It is not killed
256 * only because window stays zero for some time, window may be zero
257 * until armageddon and even later. We are in full accordance
258 * with RFCs, only probe timer combines both retransmission timeout
259 * and probe timeout in one bottle. --ANK
260 */
261 max_probes = sysctl_tcp_retries2;
262
263 if (sock_flag(sk, SOCK_DEAD)) {
264 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
265
266 max_probes = tcp_orphan_retries(sk, alive);
267
268 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
269 return;
270 }
271
272 if (icsk->icsk_probes_out > max_probes) {
273 tcp_write_err(sk);
274 } else {
275 /* Only send another probe if we didn't close things up. */
276 tcp_send_probe0(sk);
277 }
278 }
279
280 /*
281 * The TCP retransmit timer.
282 */
283
284 static void tcp_retransmit_timer(struct sock *sk)
285 {
286 struct tcp_sock *tp = tcp_sk(sk);
287 struct inet_connection_sock *icsk = inet_csk(sk);
288
289 if (!tp->packets_out)
290 goto out;
291
292 BUG_TRAP(!tcp_write_queue_empty(sk));
293
294 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
295 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
296 /* Receiver dastardly shrinks window. Our retransmits
297 * become zero probes, but we should not timeout this
298 * connection. If the socket is an orphan, time it out,
299 * we cannot allow such beasts to hang infinitely.
300 */
301 #ifdef TCP_DEBUG
302 if (1) {
303 struct inet_sock *inet = inet_sk(sk);
304 LIMIT_NETDEBUG(KERN_DEBUG "TCP: Treason uncloaked! Peer %u.%u.%u.%u:%u/%u shrinks window %u:%u. Repaired.\n",
305 NIPQUAD(inet->daddr), ntohs(inet->dport),
306 inet->num, tp->snd_una, tp->snd_nxt);
307 }
308 #endif
309 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
310 tcp_write_err(sk);
311 goto out;
312 }
313 tcp_enter_loss(sk, 0);
314 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
315 __sk_dst_reset(sk);
316 goto out_reset_timer;
317 }
318
319 if (tcp_write_timeout(sk))
320 goto out;
321
322 if (icsk->icsk_retransmits == 0) {
323 if (icsk->icsk_ca_state == TCP_CA_Disorder ||
324 icsk->icsk_ca_state == TCP_CA_Recovery) {
325 if (tcp_is_sack(tp)) {
326 if (icsk->icsk_ca_state == TCP_CA_Recovery)
327 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERYFAIL);
328 else
329 NET_INC_STATS_BH(LINUX_MIB_TCPSACKFAILURES);
330 } else {
331 if (icsk->icsk_ca_state == TCP_CA_Recovery)
332 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERYFAIL);
333 else
334 NET_INC_STATS_BH(LINUX_MIB_TCPRENOFAILURES);
335 }
336 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
337 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSFAILURES);
338 } else {
339 NET_INC_STATS_BH(LINUX_MIB_TCPTIMEOUTS);
340 }
341 }
342
343 if (tcp_use_frto(sk)) {
344 tcp_enter_frto(sk);
345 } else {
346 tcp_enter_loss(sk, 0);
347 }
348
349 if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
350 /* Retransmission failed because of local congestion,
351 * do not backoff.
352 */
353 if (!icsk->icsk_retransmits)
354 icsk->icsk_retransmits = 1;
355 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
356 min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
357 TCP_RTO_MAX);
358 goto out;
359 }
360
361 /* Increase the timeout each time we retransmit. Note that
362 * we do not increase the rtt estimate. rto is initialized
363 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
364 * that doubling rto each time is the least we can get away with.
365 * In KA9Q, Karn uses this for the first few times, and then
366 * goes to quadratic. netBSD doubles, but only goes up to *64,
367 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
368 * defined in the protocol as the maximum possible RTT. I guess
369 * we'll have to use something other than TCP to talk to the
370 * University of Mars.
371 *
372 * PAWS allows us longer timeouts and large windows, so once
373 * implemented ftp to mars will work nicely. We will have to fix
374 * the 120 second clamps though!
375 */
376 icsk->icsk_backoff++;
377 icsk->icsk_retransmits++;
378
379 out_reset_timer:
380 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
381 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
382 if (icsk->icsk_retransmits > sysctl_tcp_retries1)
383 __sk_dst_reset(sk);
384
385 out:;
386 }
387
388 static void tcp_write_timer(unsigned long data)
389 {
390 struct sock *sk = (struct sock*)data;
391 struct inet_connection_sock *icsk = inet_csk(sk);
392 int event;
393
394 bh_lock_sock(sk);
395 if (sock_owned_by_user(sk)) {
396 /* Try again later */
397 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + (HZ / 20));
398 goto out_unlock;
399 }
400
401 if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
402 goto out;
403
404 if (time_after(icsk->icsk_timeout, jiffies)) {
405 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
406 goto out;
407 }
408
409 event = icsk->icsk_pending;
410 icsk->icsk_pending = 0;
411
412 switch (event) {
413 case ICSK_TIME_RETRANS:
414 tcp_retransmit_timer(sk);
415 break;
416 case ICSK_TIME_PROBE0:
417 tcp_probe_timer(sk);
418 break;
419 }
420 TCP_CHECK_TIMER(sk);
421
422 out:
423 sk_mem_reclaim(sk);
424 out_unlock:
425 bh_unlock_sock(sk);
426 sock_put(sk);
427 }
428
429 /*
430 * Timer for listening sockets
431 */
432
433 static void tcp_synack_timer(struct sock *sk)
434 {
435 inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
436 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
437 }
438
439 void tcp_set_keepalive(struct sock *sk, int val)
440 {
441 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
442 return;
443
444 if (val && !sock_flag(sk, SOCK_KEEPOPEN))
445 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
446 else if (!val)
447 inet_csk_delete_keepalive_timer(sk);
448 }
449
450
451 static void tcp_keepalive_timer (unsigned long data)
452 {
453 struct sock *sk = (struct sock *) data;
454 struct inet_connection_sock *icsk = inet_csk(sk);
455 struct tcp_sock *tp = tcp_sk(sk);
456 __u32 elapsed;
457
458 /* Only process if socket is not in use. */
459 bh_lock_sock(sk);
460 if (sock_owned_by_user(sk)) {
461 /* Try again later. */
462 inet_csk_reset_keepalive_timer (sk, HZ/20);
463 goto out;
464 }
465
466 if (sk->sk_state == TCP_LISTEN) {
467 tcp_synack_timer(sk);
468 goto out;
469 }
470
471 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
472 if (tp->linger2 >= 0) {
473 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
474
475 if (tmo > 0) {
476 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
477 goto out;
478 }
479 }
480 tcp_send_active_reset(sk, GFP_ATOMIC);
481 goto death;
482 }
483
484 if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
485 goto out;
486
487 elapsed = keepalive_time_when(tp);
488
489 /* It is alive without keepalive 8) */
490 if (tp->packets_out || tcp_send_head(sk))
491 goto resched;
492
493 elapsed = tcp_time_stamp - tp->rcv_tstamp;
494
495 if (elapsed >= keepalive_time_when(tp)) {
496 if ((!tp->keepalive_probes && icsk->icsk_probes_out >= sysctl_tcp_keepalive_probes) ||
497 (tp->keepalive_probes && icsk->icsk_probes_out >= tp->keepalive_probes)) {
498 tcp_send_active_reset(sk, GFP_ATOMIC);
499 tcp_write_err(sk);
500 goto out;
501 }
502 if (tcp_write_wakeup(sk) <= 0) {
503 icsk->icsk_probes_out++;
504 elapsed = keepalive_intvl_when(tp);
505 } else {
506 /* If keepalive was lost due to local congestion,
507 * try harder.
508 */
509 elapsed = TCP_RESOURCE_PROBE_INTERVAL;
510 }
511 } else {
512 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
513 elapsed = keepalive_time_when(tp) - elapsed;
514 }
515
516 TCP_CHECK_TIMER(sk);
517 sk_mem_reclaim(sk);
518
519 resched:
520 inet_csk_reset_keepalive_timer (sk, elapsed);
521 goto out;
522
523 death:
524 tcp_done(sk);
525
526 out:
527 bh_unlock_sock(sk);
528 sock_put(sk);
529 }
530
|
This page was automatically generated by the
LXR engine.
|