2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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12 * notice, this list of conditions and the following disclaimer.
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15 * documentation and/or other materials provided with the distribution.
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17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
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39 * modification, are permitted provided that the following conditions
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63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
66 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
67 * $FreeBSD: src/sys/netinet/tcp_timer.c,v 1.34.2.14 2003/02/03 02:33:41 hsu Exp $
68 * $DragonFly: src/sys/netinet/tcp_timer.c,v 1.17 2008/03/30 20:39:01 dillon Exp $
71 #include "opt_compat.h"
72 #include "opt_inet6.h"
73 #include "opt_tcpdebug.h"
75 #include <sys/param.h>
76 #include <sys/systm.h>
77 #include <sys/kernel.h>
79 #include <sys/sysctl.h>
80 #include <sys/socket.h>
81 #include <sys/socketvar.h>
82 #include <sys/protosw.h>
83 #include <sys/thread.h>
84 #include <sys/globaldata.h>
85 #include <sys/thread2.h>
86 #include <sys/msgport2.h>
88 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
90 #include <net/route.h>
91 #include <net/netmsg2.h>
93 #include <netinet/in.h>
94 #include <netinet/in_systm.h>
95 #include <netinet/in_pcb.h>
97 #include <netinet6/in6_pcb.h>
99 #include <netinet/ip_var.h>
100 #include <netinet/tcp.h>
101 #include <netinet/tcp_fsm.h>
102 #include <netinet/tcp_seq.h>
103 #include <netinet/tcp_timer.h>
104 #include <netinet/tcp_timer2.h>
105 #include <netinet/tcp_var.h>
106 #include <netinet/tcpip.h>
108 #include <netinet/tcp_debug.h>
111 #define TCP_TIMER_REXMT 0x01
112 #define TCP_TIMER_PERSIST 0x02
113 #define TCP_TIMER_KEEP 0x04
114 #define TCP_TIMER_2MSL 0x08
115 #define TCP_TIMER_DELACK 0x10
117 static struct tcpcb *tcp_timer_rexmt_handler(struct tcpcb *);
118 static struct tcpcb *tcp_timer_persist_handler(struct tcpcb *);
119 static struct tcpcb *tcp_timer_keep_handler(struct tcpcb *);
120 static struct tcpcb *tcp_timer_2msl_handler(struct tcpcb *);
121 static struct tcpcb *tcp_timer_delack_handler(struct tcpcb *);
123 static const struct tcp_timer {
125 struct tcpcb *(*tt_handler)(struct tcpcb *);
126 } tcp_timer_handlers[] = {
127 { TCP_TIMER_DELACK, tcp_timer_delack_handler },
128 { TCP_TIMER_REXMT, tcp_timer_rexmt_handler },
129 { TCP_TIMER_PERSIST, tcp_timer_persist_handler },
130 { TCP_TIMER_KEEP, tcp_timer_keep_handler },
131 { TCP_TIMER_2MSL, tcp_timer_2msl_handler },
136 sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS)
140 tt = *(int *)oidp->oid_arg1;
141 s = (int)((int64_t)tt * 1000 / hz);
143 error = sysctl_handle_int(oidp, &s, 0, req);
144 if (error || !req->newptr)
147 tt = (int)((int64_t)s * hz / 1000);
151 *(int *)oidp->oid_arg1 = tt;
156 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
157 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "Time to establish TCP connection");
160 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
161 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "Time before TCP keepalive probes begin");
164 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
165 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "Time between TCP keepalive probes");
168 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
169 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
170 "Time before a delayed ACK is sent");
173 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
174 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
177 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
178 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout");
181 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
182 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
183 "Retransmission Timer Slop");
185 static int always_keepalive = 1;
186 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
187 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
189 /* max idle probes */
190 static int tcp_keepcnt = TCPTV_KEEPCNT;
191 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW,
192 &tcp_keepcnt, 0, "Maximum number of keepalive probes to be sent");
194 /* max idle time in persist */
195 int tcp_maxpersistidle;
200 * Tcp protocol timeout routine called every 500 ms.
201 * Updates timestamps used for TCP
202 * causes finite state machine actions if timers expire.
208 tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
213 * Cancel all timers for TCP tp.
216 tcp_canceltimers(struct tcpcb *tp)
218 tcp_callout_stop(tp, tp->tt_2msl);
219 tcp_callout_stop(tp, tp->tt_persist);
220 tcp_callout_stop(tp, tp->tt_keep);
221 tcp_callout_stop(tp, tp->tt_rexmt);
225 * Caller should be in critical section
228 tcp_send_timermsg(struct tcpcb *tp, uint32_t task)
230 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
232 KKASSERT(tmsg != NULL && tmsg->tt_cpuid == mycpuid &&
233 tmsg->tt_tcb != NULL);
235 tmsg->tt_tasks |= task;
236 if (tmsg->tt_msg.lmsg.ms_flags & MSGF_DONE)
237 lwkt_sendmsg(tmsg->tt_msgport, &tmsg->tt_msg.lmsg);
240 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
241 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
243 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
244 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
246 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
248 /* Caller should be in critical section */
249 static struct tcpcb *
250 tcp_timer_delack_handler(struct tcpcb *tp)
252 tp->t_flags |= TF_ACKNOW;
253 tcpstat.tcps_delack++;
259 * TCP timer processing.
262 tcp_timer_delack(void *xtp)
264 struct tcpcb *tp = xtp;
265 struct callout *co = &tp->tt_delack->tc_callout;
268 if (callout_pending(co) || !callout_active(co)) {
272 callout_deactivate(co);
273 tcp_send_timermsg(tp, TCP_TIMER_DELACK);
277 /* Caller should be in critical section */
278 static struct tcpcb *
279 tcp_timer_2msl_handler(struct tcpcb *tp)
286 ostate = tp->t_state;
289 * 2 MSL timeout in shutdown went off. If we're closed but
290 * still waiting for peer to close and connection has been idle
291 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
292 * control block. Otherwise, check again in a bit.
294 if (tp->t_state != TCPS_TIME_WAIT &&
295 (ticks - tp->t_rcvtime) <= tcp_maxidle) {
296 tcp_callout_reset(tp, tp->tt_2msl, tcp_keepintvl,
303 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
304 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
310 tcp_timer_2msl(void *xtp)
312 struct tcpcb *tp = xtp;
313 struct callout *co = &tp->tt_2msl->tc_callout;
316 if (callout_pending(co) || !callout_active(co)) {
320 callout_deactivate(co);
321 tcp_send_timermsg(tp, TCP_TIMER_2MSL);
325 /* Caller should be in critical section */
326 static struct tcpcb *
327 tcp_timer_keep_handler(struct tcpcb *tp)
329 struct tcptemp *t_template;
333 int keepidle = tcp_getkeepidle(tp);
336 ostate = tp->t_state;
339 * Keep-alive timer went off; send something
340 * or drop connection if idle for too long.
342 tcpstat.tcps_keeptimeo++;
343 if (tp->t_state < TCPS_ESTABLISHED)
345 if ((always_keepalive || (tp->t_flags & TF_KEEPALIVE) ||
346 (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE)) &&
347 tp->t_state <= TCPS_CLOSING) {
348 if ((ticks - tp->t_rcvtime) >= keepidle + tcp_maxidle)
351 * Send a packet designed to force a response
352 * if the peer is up and reachable:
353 * either an ACK if the connection is still alive,
354 * or an RST if the peer has closed the connection
355 * due to timeout or reboot.
356 * Using sequence number tp->snd_una-1
357 * causes the transmitted zero-length segment
358 * to lie outside the receive window;
359 * by the protocol spec, this requires the
360 * correspondent TCP to respond.
362 tcpstat.tcps_keepprobe++;
363 t_template = tcp_maketemplate(tp);
365 tcp_respond(tp, t_template->tt_ipgen,
366 &t_template->tt_t, NULL,
367 tp->rcv_nxt, tp->snd_una - 1, 0);
368 tcp_freetemplate(t_template);
370 tcp_callout_reset(tp, tp->tt_keep, tcp_keepintvl,
373 tcp_callout_reset(tp, tp->tt_keep, keepidle,
378 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
379 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
384 tcpstat.tcps_keepdrops++;
385 tp = tcp_drop(tp, ETIMEDOUT);
388 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
389 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
395 tcp_timer_keep(void *xtp)
397 struct tcpcb *tp = xtp;
398 struct callout *co = &tp->tt_keep->tc_callout;
401 if (callout_pending(co) || !callout_active(co)) {
405 callout_deactivate(co);
406 tcp_send_timermsg(tp, TCP_TIMER_KEEP);
410 /* Caller should be in critical section */
411 static struct tcpcb *
412 tcp_timer_persist_handler(struct tcpcb *tp)
419 ostate = tp->t_state;
422 * Persistance timer into zero window.
423 * Force a byte to be output, if possible.
425 tcpstat.tcps_persisttimeo++;
427 * Hack: if the peer is dead/unreachable, we do not
428 * time out if the window is closed. After a full
429 * backoff, drop the connection if the idle time
430 * (no responses to probes) reaches the maximum
431 * backoff that we would use if retransmitting.
433 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
434 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle ||
435 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
436 tcpstat.tcps_persistdrop++;
437 tp = tcp_drop(tp, ETIMEDOUT);
441 tp->t_flags |= TF_FORCE;
443 tp->t_flags &= ~TF_FORCE;
447 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
448 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
454 tcp_timer_persist(void *xtp)
456 struct tcpcb *tp = xtp;
457 struct callout *co = &tp->tt_persist->tc_callout;
460 if (callout_pending(co) || !callout_active(co)){
464 callout_deactivate(co);
465 tcp_send_timermsg(tp, TCP_TIMER_PERSIST);
470 tcp_save_congestion_state(struct tcpcb *tp)
472 tp->snd_cwnd_prev = tp->snd_cwnd;
473 tp->snd_wacked_prev = tp->snd_wacked;
474 tp->snd_ssthresh_prev = tp->snd_ssthresh;
475 tp->snd_recover_prev = tp->snd_recover;
476 if (IN_FASTRECOVERY(tp))
477 tp->t_flags |= TF_WASFRECOVERY;
479 tp->t_flags &= ~TF_WASFRECOVERY;
480 if (tp->t_flags & TF_RCVD_TSTMP) {
481 tp->t_rexmtTS = ticks;
482 tp->t_flags |= TF_FIRSTACCACK;
485 tcp_sack_save_scoreboard(&tp->scb);
490 tcp_revert_congestion_state(struct tcpcb *tp)
492 tp->snd_cwnd = tp->snd_cwnd_prev;
493 tp->snd_wacked = tp->snd_wacked_prev;
494 tp->snd_ssthresh = tp->snd_ssthresh_prev;
495 tp->snd_recover = tp->snd_recover_prev;
496 if (tp->t_flags & TF_WASFRECOVERY)
497 ENTER_FASTRECOVERY(tp);
498 if (tp->t_flags & TF_FASTREXMT) {
499 ++tcpstat.tcps_sndfastrexmitbad;
500 if (tp->t_flags & TF_EARLYREXMT)
501 ++tcpstat.tcps_sndearlyrexmitbad;
503 ++tcpstat.tcps_sndrtobad;
506 tp->snd_nxt = tp->snd_max;
508 tcp_sack_revert_scoreboard(&tp->scb, tp->snd_una);
512 /* Caller should be in critical section */
513 static struct tcpcb *
514 tcp_timer_rexmt_handler(struct tcpcb *tp)
522 ostate = tp->t_state;
525 * Retransmission timer went off. Message has not
526 * been acked within retransmit interval. Back off
527 * to a longer retransmit interval and retransmit one segment.
529 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
530 tp->t_rxtshift = TCP_MAXRXTSHIFT;
531 tcpstat.tcps_timeoutdrop++;
532 tp = tcp_drop(tp, tp->t_softerror ?
533 tp->t_softerror : ETIMEDOUT);
536 if (tp->t_rxtshift == 1) {
538 * first retransmit; record ssthresh and cwnd so they can
539 * be recovered if this turns out to be a "bad" retransmit.
540 * A retransmit is considered "bad" if an ACK for this
541 * segment is received within RTT/2 interval; the assumption
542 * here is that the ACK was already in flight. See
543 * "On Estimating End-to-End Network Path Properties" by
544 * Allman and Paxson for more details.
546 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
547 tcp_save_congestion_state(tp);
548 tp->t_flags &= ~(TF_FASTREXMT | TF_EARLYREXMT);
550 /* Throw away SACK blocks on a RTO, as specified by RFC2018. */
551 tcp_sack_cleanup(&tp->scb);
552 tcpstat.tcps_rexmttimeo++;
553 if (tp->t_state == TCPS_SYN_SENT)
554 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift];
556 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
557 TCPT_RANGESET(tp->t_rxtcur, rexmt,
558 tp->t_rttmin, TCPTV_REXMTMAX);
560 * Disable rfc1323 if we havn't got any response to
561 * our third SYN to work-around some broken terminal servers
562 * (most of which have hopefully been retired) that have bad VJ
563 * header compression code which trashes TCP segments containing
564 * unknown-to-them TCP options.
566 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3))
567 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP);
569 * If losing, let the lower level know and try for
570 * a better route. Also, if we backed off this far,
571 * our srtt estimate is probably bogus. Clobber it
572 * so we'll take the next rtt measurement as our srtt;
573 * move the current srtt into rttvar to keep the current
574 * retransmit times until then.
576 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
578 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
579 in6_losing(tp->t_inpcb);
582 in_losing(tp->t_inpcb);
583 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
586 tp->snd_nxt = tp->snd_una;
587 tp->rexmt_high = tp->snd_una;
588 tp->snd_recover = tp->snd_max;
590 * Force a segment to be sent.
592 tp->t_flags |= TF_ACKNOW;
594 * If timing a segment in this window, stop the timer.
598 * Close the congestion window down to one segment
599 * (we'll open it by one segment for each ack we get).
600 * Since we probably have a window's worth of unacked
601 * data accumulated, this "slow start" keeps us from
602 * dumping all that data as back-to-back packets (which
603 * might overwhelm an intermediate gateway).
605 * There are two phases to the opening: Initially we
606 * open by one mss on each ack. This makes the window
607 * size increase exponentially with time. If the
608 * window is larger than the path can handle, this
609 * exponential growth results in dropped packet(s)
610 * almost immediately. To get more time between
611 * drops but still "push" the network to take advantage
612 * of improving conditions, we switch from exponential
613 * to linear window opening at some threshhold size.
614 * For a threshhold, we use half the current window
615 * size, truncated to a multiple of the mss.
617 * (the minimum cwnd that will give us exponential
618 * growth is 2 mss. We don't allow the threshhold
622 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
626 tp->snd_cwnd = tp->t_maxseg;
628 tp->snd_ssthresh = win * tp->t_maxseg;
631 EXIT_FASTRECOVERY(tp);
636 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
637 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
643 tcp_timer_rexmt(void *xtp)
645 struct tcpcb *tp = xtp;
646 struct callout *co = &tp->tt_rexmt->tc_callout;
649 if (callout_pending(co) || !callout_active(co)) {
653 callout_deactivate(co);
654 tcp_send_timermsg(tp, TCP_TIMER_REXMT);
659 tcp_timer_handler(netmsg_t msg)
661 struct netmsg_tcp_timer *tmsg = (struct netmsg_tcp_timer *)msg;
662 const struct tcp_timer *tt;
667 KKASSERT(tmsg->tt_cpuid == mycpuid && tmsg->tt_tcb != NULL);
670 /* Save pending tasks and reset the tasks in message */
671 tmsg->tt_running_tasks = tmsg->tt_tasks;
672 tmsg->tt_prev_tasks = tmsg->tt_tasks;
676 lwkt_replymsg(&tmsg->tt_msg.lmsg, 0);
678 if (tmsg->tt_running_tasks == 0) {
680 * All of the timers are cancelled when the message
681 * is pending; bail out.
687 for (tt = tcp_timer_handlers; tt->tt_handler != NULL; ++tt) {
688 if ((tmsg->tt_running_tasks & tt->tt_task) == 0)
691 tmsg->tt_running_tasks &= ~tt->tt_task;
692 tp = tt->tt_handler(tp);
696 if (tmsg->tt_running_tasks == 0) /* nothing left to do */
704 tcp_create_timermsg(struct tcpcb *tp, struct lwkt_port *msgport)
706 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
708 netmsg_init(&tmsg->tt_msg, NULL, &netisr_adone_rport,
709 MSGF_DROPABLE | MSGF_PRIORITY, tcp_timer_handler);
710 tmsg->tt_cpuid = mycpuid;
711 tmsg->tt_msgport = msgport;
717 tcp_destroy_timermsg(struct tcpcb *tp)
719 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
721 if (tmsg == NULL || /* listen socket */
722 tmsg->tt_tcb == NULL) /* only tcp_attach() is called */
725 KKASSERT(tmsg->tt_cpuid == mycpuid);
727 if ((tmsg->tt_msg.lmsg.ms_flags & MSGF_DONE) == 0) {
729 * This message is still pending to be processed;
732 lwkt_dropmsg(&tmsg->tt_msg.lmsg);
738 tcp_callout_init(struct tcp_callout *tc, uint32_t task)
740 callout_init(&tc->tc_callout);
745 tcp_inittimers(struct tcpcb *tp)
747 tcp_callout_init(tp->tt_rexmt, TCP_TIMER_REXMT);
748 tcp_callout_init(tp->tt_persist, TCP_TIMER_PERSIST);
749 tcp_callout_init(tp->tt_keep, TCP_TIMER_KEEP);
750 tcp_callout_init(tp->tt_2msl, TCP_TIMER_2MSL);
751 tcp_callout_init(tp->tt_delack, TCP_TIMER_DELACK);