tcp_timer.c revision 1.63 1 /* $NetBSD: tcp_timer.c,v 1.63 2003/07/20 16:35:09 he Exp $ */
2
3 /*
4 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the project nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 /*-
33 * Copyright (c) 1997, 1998, 2001 The NetBSD Foundation, Inc.
34 * All rights reserved.
35 *
36 * This code is derived from software contributed to The NetBSD Foundation
37 * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation
38 * Facility, NASA Ames Research Center.
39 *
40 * Redistribution and use in source and binary forms, with or without
41 * modification, are permitted provided that the following conditions
42 * are met:
43 * 1. Redistributions of source code must retain the above copyright
44 * notice, this list of conditions and the following disclaimer.
45 * 2. Redistributions in binary form must reproduce the above copyright
46 * notice, this list of conditions and the following disclaimer in the
47 * documentation and/or other materials provided with the distribution.
48 * 3. All advertising materials mentioning features or use of this software
49 * must display the following acknowledgement:
50 * This product includes software developed by the NetBSD
51 * Foundation, Inc. and its contributors.
52 * 4. Neither the name of The NetBSD Foundation nor the names of its
53 * contributors may be used to endorse or promote products derived
54 * from this software without specific prior written permission.
55 *
56 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
57 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
58 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
59 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
60 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
61 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
62 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
63 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
64 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
65 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
66 * POSSIBILITY OF SUCH DAMAGE.
67 */
68
69 /*
70 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
71 * The Regents of the University of California. All rights reserved.
72 *
73 * Redistribution and use in source and binary forms, with or without
74 * modification, are permitted provided that the following conditions
75 * are met:
76 * 1. Redistributions of source code must retain the above copyright
77 * notice, this list of conditions and the following disclaimer.
78 * 2. Redistributions in binary form must reproduce the above copyright
79 * notice, this list of conditions and the following disclaimer in the
80 * documentation and/or other materials provided with the distribution.
81 * 3. All advertising materials mentioning features or use of this software
82 * must display the following acknowledgement:
83 * This product includes software developed by the University of
84 * California, Berkeley and its contributors.
85 * 4. Neither the name of the University nor the names of its contributors
86 * may be used to endorse or promote products derived from this software
87 * without specific prior written permission.
88 *
89 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
90 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
91 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
92 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
93 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
94 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
95 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
96 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
97 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
98 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
99 * SUCH DAMAGE.
100 *
101 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
102 */
103
104 #include <sys/cdefs.h>
105 __KERNEL_RCSID(0, "$NetBSD: tcp_timer.c,v 1.63 2003/07/20 16:35:09 he Exp $");
106
107 #include "opt_inet.h"
108 #include "opt_tcp_debug.h"
109
110 #include <sys/param.h>
111 #include <sys/systm.h>
112 #include <sys/malloc.h>
113 #include <sys/mbuf.h>
114 #include <sys/socket.h>
115 #include <sys/socketvar.h>
116 #include <sys/protosw.h>
117 #include <sys/errno.h>
118 #include <sys/kernel.h>
119
120 #include <net/if.h>
121 #include <net/route.h>
122
123 #include <netinet/in.h>
124 #include <netinet/in_systm.h>
125 #include <netinet/ip.h>
126 #include <netinet/in_pcb.h>
127 #include <netinet/ip_var.h>
128
129 #ifdef INET6
130 #ifndef INET
131 #include <netinet/in.h>
132 #endif
133 #include <netinet/ip6.h>
134 #include <netinet6/in6_pcb.h>
135 #endif
136
137 #include <netinet/tcp.h>
138 #include <netinet/tcp_fsm.h>
139 #include <netinet/tcp_seq.h>
140 #include <netinet/tcp_timer.h>
141 #include <netinet/tcp_var.h>
142 #include <netinet/tcpip.h>
143 #ifdef TCP_DEBUG
144 #include <netinet/tcp_debug.h>
145 #endif
146
147 /*
148 * Various tunable timer parameters. These are initialized in tcp_init(),
149 * unless they are patched.
150 */
151 int tcp_keepidle = 0;
152 int tcp_keepintvl = 0;
153 int tcp_keepcnt = 0; /* max idle probes */
154 int tcp_maxpersistidle = 0; /* max idle time in persist */
155 int tcp_maxidle; /* computed in tcp_slowtimo() */
156
157 /*
158 * Time to delay the ACK. This is initialized in tcp_init(), unless
159 * its patched.
160 */
161 int tcp_delack_ticks = 0;
162
163 void tcp_timer_rexmt(void *);
164 void tcp_timer_persist(void *);
165 void tcp_timer_keep(void *);
166 void tcp_timer_2msl(void *);
167
168 const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS] = {
169 tcp_timer_rexmt,
170 tcp_timer_persist,
171 tcp_timer_keep,
172 tcp_timer_2msl,
173 };
174
175 /*
176 * Timer state initialization, called from tcp_init().
177 */
178 void
179 tcp_timer_init(void)
180 {
181
182 if (tcp_keepidle == 0)
183 tcp_keepidle = TCPTV_KEEP_IDLE;
184
185 if (tcp_keepintvl == 0)
186 tcp_keepintvl = TCPTV_KEEPINTVL;
187
188 if (tcp_keepcnt == 0)
189 tcp_keepcnt = TCPTV_KEEPCNT;
190
191 if (tcp_maxpersistidle == 0)
192 tcp_maxpersistidle = TCPTV_KEEP_IDLE;
193
194 if (tcp_delack_ticks == 0)
195 tcp_delack_ticks = TCP_DELACK_TICKS;
196 }
197
198 /*
199 * Return how many timers are currently being invoked.
200 */
201 int
202 tcp_timers_invoking(struct tcpcb *tp)
203 {
204 int i;
205 int count = 0;
206
207 for (i = 0; i < TCPT_NTIMERS; i++)
208 if (callout_invoking(&tp->t_timer[i]))
209 count++;
210 if (callout_invoking(&tp->t_delack_ch))
211 count++;
212
213 return count;
214 }
215
216 /*
217 * Callout to process delayed ACKs for a TCPCB.
218 */
219 void
220 tcp_delack(void *arg)
221 {
222 struct tcpcb *tp = arg;
223 int s;
224
225 /*
226 * If tcp_output() wasn't able to transmit the ACK
227 * for whatever reason, it will restart the delayed
228 * ACK callout.
229 */
230
231 s = splsoftnet();
232 callout_ack(&tp->t_delack_ch);
233 if (tcp_isdead(tp)) {
234 splx(s);
235 return;
236 }
237
238 tp->t_flags |= TF_ACKNOW;
239 (void) tcp_output(tp);
240 splx(s);
241 }
242
243 /*
244 * Tcp protocol timeout routine called every 500 ms.
245 * Updates the timers in all active tcb's and
246 * causes finite state machine actions if timers expire.
247 */
248 void
249 tcp_slowtimo()
250 {
251 int s;
252
253 s = splsoftnet();
254 tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
255 tcp_iss_seq += TCP_ISSINCR; /* increment iss */
256 tcp_now++; /* for timestamps */
257 splx(s);
258 }
259
260 /*
261 * Cancel all timers for TCP tp.
262 */
263 void
264 tcp_canceltimers(tp)
265 struct tcpcb *tp;
266 {
267 int i;
268
269 for (i = 0; i < TCPT_NTIMERS; i++)
270 TCP_TIMER_DISARM(tp, i);
271 }
272
273 const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
274 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
275
276 const int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
277
278 /*
279 * TCP timer processing.
280 */
281
282 void
283 tcp_timer_rexmt(void *arg)
284 {
285 struct tcpcb *tp = arg;
286 uint32_t rto;
287 int s;
288 #ifdef TCP_DEBUG
289 struct socket *so;
290 short ostate;
291 #endif
292
293 s = splsoftnet();
294 callout_ack(&tp->t_timer[TCPT_KEEP]);
295 if (tcp_isdead(tp)) {
296 splx(s);
297 return;
298 }
299
300 #ifdef TCP_DEBUG
301 #ifdef INET
302 if (tp->t_inpcb)
303 so = tp->t_inpcb->inp_socket;
304 #endif
305 #ifdef INET6
306 if (tp->t_in6pcb)
307 so = tp->t_in6pcb->in6p_socket;
308 #endif
309 ostate = tp->t_state;
310 #endif /* TCP_DEBUG */
311
312 /*
313 * Retransmission timer went off. Message has not
314 * been acked within retransmit interval. Back off
315 * to a longer retransmit interval and retransmit one segment.
316 */
317
318 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
319 tp->t_rxtshift = TCP_MAXRXTSHIFT;
320 tcpstat.tcps_timeoutdrop++;
321 tp = tcp_drop(tp, tp->t_softerror ?
322 tp->t_softerror : ETIMEDOUT);
323 goto out;
324 }
325 tcpstat.tcps_rexmttimeo++;
326 rto = TCP_REXMTVAL(tp);
327 if (rto < tp->t_rttmin)
328 rto = tp->t_rttmin;
329 TCPT_RANGESET(tp->t_rxtcur, rto * tcp_backoff[tp->t_rxtshift],
330 tp->t_rttmin, TCPTV_REXMTMAX);
331 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
332
333 /*
334 * If we are losing and we are trying path MTU discovery,
335 * try turning it off. This will avoid black holes in
336 * the network which suppress or fail to send "packet
337 * too big" ICMP messages. We should ideally do
338 * lots more sophisticated searching to find the right
339 * value here...
340 */
341 if (tp->t_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) {
342 tcpstat.tcps_pmtublackhole++;
343
344 #ifdef INET
345 /* try turning PMTUD off */
346 if (tp->t_inpcb)
347 tp->t_mtudisc = 0;
348 #endif
349 #ifdef INET6
350 /* try using IPv6 minimum MTU */
351 if (tp->t_in6pcb)
352 tp->t_mtudisc = 0;
353 #endif
354
355 /* XXX: more sophisticated Black hole recovery code? */
356 }
357
358 /*
359 * If losing, let the lower level know and try for
360 * a better route. Also, if we backed off this far,
361 * our srtt estimate is probably bogus. Clobber it
362 * so we'll take the next rtt measurement as our srtt;
363 * move the current srtt into rttvar to keep the current
364 * retransmit times until then.
365 */
366 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
367 #ifdef INET
368 if (tp->t_inpcb)
369 in_losing(tp->t_inpcb);
370 #endif
371 #ifdef INET6
372 if (tp->t_in6pcb)
373 in6_losing(tp->t_in6pcb);
374 #endif
375 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
376 tp->t_srtt = 0;
377 }
378 tp->snd_nxt = tp->snd_una;
379 /*
380 * If timing a segment in this window, stop the timer.
381 */
382 tp->t_rtttime = 0;
383 /*
384 * Remember if we are retransmitting a SYN, because if
385 * we do, set the initial congestion window must be set
386 * to 1 segment.
387 */
388 if (tp->t_state == TCPS_SYN_SENT)
389 tp->t_flags |= TF_SYN_REXMT;
390 /*
391 * Close the congestion window down to one segment
392 * (we'll open it by one segment for each ack we get).
393 * Since we probably have a window's worth of unacked
394 * data accumulated, this "slow start" keeps us from
395 * dumping all that data as back-to-back packets (which
396 * might overwhelm an intermediate gateway).
397 *
398 * There are two phases to the opening: Initially we
399 * open by one mss on each ack. This makes the window
400 * size increase exponentially with time. If the
401 * window is larger than the path can handle, this
402 * exponential growth results in dropped packet(s)
403 * almost immediately. To get more time between
404 * drops but still "push" the network to take advantage
405 * of improving conditions, we switch from exponential
406 * to linear window opening at some threshhold size.
407 * For a threshhold, we use half the current window
408 * size, truncated to a multiple of the mss.
409 *
410 * (the minimum cwnd that will give us exponential
411 * growth is 2 mss. We don't allow the threshhold
412 * to go below this.)
413 */
414 {
415 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz;
416 if (win < 2)
417 win = 2;
418 /* Loss Window MUST be one segment. */
419 tp->snd_cwnd = tp->t_segsz;
420 tp->snd_ssthresh = win * tp->t_segsz;
421 tp->t_dupacks = 0;
422 }
423 (void) tcp_output(tp);
424
425 out:
426 #ifdef TCP_DEBUG
427 if (tp && so->so_options & SO_DEBUG)
428 tcp_trace(TA_USER, ostate, tp, NULL,
429 PRU_SLOWTIMO | (TCPT_REXMT << 8));
430 #endif
431 splx(s);
432 }
433
434 void
435 tcp_timer_persist(void *arg)
436 {
437 struct tcpcb *tp = arg;
438 uint32_t rto;
439 int s;
440 #ifdef TCP_DEBUG
441 struct socket *so;
442 short ostate;
443 #endif
444
445 s = splsoftnet();
446 callout_ack(&tp->t_timer[TCPT_PERSIST]);
447 if (tcp_isdead(tp)) {
448 splx(s);
449 return;
450 }
451
452 #ifdef TCP_DEBUG
453 #ifdef INET
454 if (tp->t_inpcb)
455 so = tp->t_inpcb->inp_socket;
456 #endif
457 #ifdef INET6
458 if (tp->t_in6pcb)
459 so = tp->t_in6pcb->in6p_socket;
460 #endif
461
462 ostate = tp->t_state;
463 #endif /* TCP_DEBUG */
464
465 /*
466 * Persistance timer into zero window.
467 * Force a byte to be output, if possible.
468 */
469
470 /*
471 * Hack: if the peer is dead/unreachable, we do not
472 * time out if the window is closed. After a full
473 * backoff, drop the connection if the idle time
474 * (no responses to probes) reaches the maximum
475 * backoff that we would use if retransmitting.
476 */
477 rto = TCP_REXMTVAL(tp);
478 if (rto < tp->t_rttmin)
479 rto = tp->t_rttmin;
480 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
481 ((tcp_now - tp->t_rcvtime) >= tcp_maxpersistidle ||
482 (tcp_now - tp->t_rcvtime) >= rto * tcp_totbackoff)) {
483 tcpstat.tcps_persistdrops++;
484 tp = tcp_drop(tp, ETIMEDOUT);
485 goto out;
486 }
487 tcpstat.tcps_persisttimeo++;
488 tcp_setpersist(tp);
489 tp->t_force = 1;
490 (void) tcp_output(tp);
491 tp->t_force = 0;
492
493 out:
494 #ifdef TCP_DEBUG
495 if (tp && so->so_options & SO_DEBUG)
496 tcp_trace(TA_USER, ostate, tp, NULL,
497 PRU_SLOWTIMO | (TCPT_PERSIST << 8));
498 #endif
499 splx(s);
500 }
501
502 void
503 tcp_timer_keep(void *arg)
504 {
505 struct tcpcb *tp = arg;
506 struct socket *so = NULL; /* Quell compiler warning */
507 int s;
508 #ifdef TCP_DEBUG
509 short ostate;
510 #endif
511
512 s = splsoftnet();
513 callout_ack(&tp->t_timer[TCPT_KEEP]);
514 if (tcp_isdead(tp)) {
515 splx(s);
516 return;
517 }
518
519 #ifdef TCP_DEBUG
520 ostate = tp->t_state;
521 #endif /* TCP_DEBUG */
522
523 /*
524 * Keep-alive timer went off; send something
525 * or drop connection if idle for too long.
526 */
527
528 tcpstat.tcps_keeptimeo++;
529 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0)
530 goto dropit;
531 #ifdef INET
532 if (tp->t_inpcb)
533 so = tp->t_inpcb->inp_socket;
534 #endif
535 #ifdef INET6
536 if (tp->t_in6pcb)
537 so = tp->t_in6pcb->in6p_socket;
538 #endif
539 if (so->so_options & SO_KEEPALIVE &&
540 tp->t_state <= TCPS_CLOSE_WAIT) {
541 if ((tcp_maxidle > 0) &&
542 ((tcp_now - tp->t_rcvtime) >=
543 tcp_keepidle + tcp_maxidle))
544 goto dropit;
545 /*
546 * Send a packet designed to force a response
547 * if the peer is up and reachable:
548 * either an ACK if the connection is still alive,
549 * or an RST if the peer has closed the connection
550 * due to timeout or reboot.
551 * Using sequence number tp->snd_una-1
552 * causes the transmitted zero-length segment
553 * to lie outside the receive window;
554 * by the protocol spec, this requires the
555 * correspondent TCP to respond.
556 */
557 tcpstat.tcps_keepprobe++;
558 if (tcp_compat_42) {
559 /*
560 * The keepalive packet must have nonzero
561 * length to get a 4.2 host to respond.
562 */
563 (void)tcp_respond(tp, tp->t_template,
564 (struct mbuf *)NULL, NULL, tp->rcv_nxt - 1,
565 tp->snd_una - 1, 0);
566 } else {
567 (void)tcp_respond(tp, tp->t_template,
568 (struct mbuf *)NULL, NULL, tp->rcv_nxt,
569 tp->snd_una - 1, 0);
570 }
571 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepintvl);
572 } else
573 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle);
574
575 #ifdef TCP_DEBUG
576 if (tp && so->so_options & SO_DEBUG)
577 tcp_trace(TA_USER, ostate, tp, NULL,
578 PRU_SLOWTIMO | (TCPT_KEEP << 8));
579 #endif
580 splx(s);
581 return;
582
583 dropit:
584 tcpstat.tcps_keepdrops++;
585 (void) tcp_drop(tp, ETIMEDOUT);
586 splx(s);
587 }
588
589 void
590 tcp_timer_2msl(void *arg)
591 {
592 struct tcpcb *tp = arg;
593 int s;
594 #ifdef TCP_DEBUG
595 struct socket *so;
596 short ostate;
597 #endif
598
599 s = splsoftnet();
600 callout_ack(&tp->t_timer[TCPT_2MSL]);
601 if (tcp_isdead(tp)) {
602 splx(s);
603 return;
604 }
605
606 #ifdef TCP_DEBUG
607 #ifdef INET
608 if (tp->t_inpcb)
609 so = tp->t_inpcb->inp_socket;
610 #endif
611 #ifdef INET6
612 if (tp->t_in6pcb)
613 so = tp->t_in6pcb->in6p_socket;
614 #endif
615
616 ostate = tp->t_state;
617 #endif /* TCP_DEBUG */
618
619 /*
620 * 2 MSL timeout in shutdown went off. If we're closed but
621 * still waiting for peer to close and connection has been idle
622 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
623 * control block. Otherwise, check again in a bit.
624 */
625 if (tp->t_state != TCPS_TIME_WAIT &&
626 ((tcp_maxidle == 0) || ((tcp_now - tp->t_rcvtime) <= tcp_maxidle)))
627 TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl);
628 else
629 tp = tcp_close(tp);
630
631 #ifdef TCP_DEBUG
632 if (tp && so->so_options & SO_DEBUG)
633 tcp_trace(TA_USER, ostate, tp, NULL,
634 PRU_SLOWTIMO | (TCPT_2MSL << 8));
635 #endif
636 splx(s);
637 }
638