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 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 static int tcp_do_eifel_response = 1;
195 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel_response, CTLFLAG_RW,
196 &tcp_do_eifel_response, 0, "Eifel response algorithm (RFC 4015)");
198 int tcp_eifel_rtoinc = 2;
199 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, eifel_rtoinc, CTLTYPE_INT|CTLFLAG_RW,
200 &tcp_eifel_rtoinc, 0, sysctl_msec_to_ticks, "I",
201 "Eifel response RTO increment");
203 /* max idle time in persist */
204 int tcp_maxpersistidle;
207 * Cancel all timers for TCP tp.
210 tcp_canceltimers(struct tcpcb *tp)
212 tcp_callout_stop(tp, tp->tt_2msl);
213 tcp_callout_stop(tp, tp->tt_persist);
214 tcp_callout_stop(tp, tp->tt_keep);
215 tcp_callout_stop(tp, tp->tt_rexmt);
219 * Caller should be in critical section
222 tcp_send_timermsg(struct tcpcb *tp, uint32_t task)
224 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
226 KKASSERT(tmsg != NULL && tmsg->tt_cpuid == mycpuid &&
227 tmsg->tt_tcb != NULL);
229 tmsg->tt_tasks |= task;
230 if (tmsg->tt_msg.lmsg.ms_flags & MSGF_DONE)
231 lwkt_sendmsg(tmsg->tt_msgport, &tmsg->tt_msg.lmsg);
234 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
235 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
237 int tcp_syn_backoff_low[TCP_MAXRXTSHIFT + 1] =
238 { 1, 1, 2, 4, 8, 8, 16, 16, 32, 64, 64, 64, 64 };
240 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
241 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
243 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
245 /* Caller should be in critical section */
246 static struct tcpcb *
247 tcp_timer_delack_handler(struct tcpcb *tp)
249 tp->t_flags |= TF_ACKNOW;
250 tcpstat.tcps_delack++;
256 * TCP timer processing.
259 tcp_timer_delack(void *xtp)
261 struct tcpcb *tp = xtp;
262 struct callout *co = &tp->tt_delack->tc_callout;
265 if (callout_pending(co) || !callout_active(co)) {
269 callout_deactivate(co);
270 tcp_send_timermsg(tp, TCP_TIMER_DELACK);
274 /* Caller should be in critical section */
275 static struct tcpcb *
276 tcp_timer_2msl_handler(struct tcpcb *tp)
283 ostate = tp->t_state;
286 * 2 MSL timeout in shutdown went off. If we're closed but
287 * still waiting for peer to close and connection has been idle
288 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
289 * control block. Otherwise, check again in a bit.
291 if (tp->t_state != TCPS_TIME_WAIT &&
292 (ticks - tp->t_rcvtime) <= tp->t_maxidle) {
293 tcp_callout_reset(tp, tp->tt_2msl, tp->t_keepintvl,
300 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
301 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
307 tcp_timer_2msl(void *xtp)
309 struct tcpcb *tp = xtp;
310 struct callout *co = &tp->tt_2msl->tc_callout;
313 if (callout_pending(co) || !callout_active(co)) {
317 callout_deactivate(co);
318 tcp_send_timermsg(tp, TCP_TIMER_2MSL);
322 /* Caller should be in critical section */
323 static struct tcpcb *
324 tcp_timer_keep_handler(struct tcpcb *tp)
326 struct tcptemp *t_template;
328 int ostate = tp->t_state;
332 * Keep-alive timer went off; send something
333 * or drop connection if idle for too long.
335 tcpstat.tcps_keeptimeo++;
336 if (tp->t_state < TCPS_ESTABLISHED)
338 if ((always_keepalive || (tp->t_flags & TF_KEEPALIVE) ||
339 (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE)) &&
340 tp->t_state <= TCPS_CLOSING) {
341 if ((ticks - tp->t_rcvtime) >= tp->t_keepidle + tp->t_maxidle)
344 * Send a packet designed to force a response
345 * if the peer is up and reachable:
346 * either an ACK if the connection is still alive,
347 * or an RST if the peer has closed the connection
348 * due to timeout or reboot.
349 * Using sequence number tp->snd_una-1
350 * causes the transmitted zero-length segment
351 * to lie outside the receive window;
352 * by the protocol spec, this requires the
353 * correspondent TCP to respond.
355 tcpstat.tcps_keepprobe++;
356 t_template = tcp_maketemplate(tp);
358 tcp_respond(tp, t_template->tt_ipgen,
359 &t_template->tt_t, NULL,
360 tp->rcv_nxt, tp->snd_una - 1, 0);
361 tcp_freetemplate(t_template);
363 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepintvl,
366 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle,
371 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
372 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
377 tcpstat.tcps_keepdrops++;
378 tp = tcp_drop(tp, ETIMEDOUT);
381 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
382 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
388 tcp_timer_keep(void *xtp)
390 struct tcpcb *tp = xtp;
391 struct callout *co = &tp->tt_keep->tc_callout;
394 if (callout_pending(co) || !callout_active(co)) {
398 callout_deactivate(co);
399 tcp_send_timermsg(tp, TCP_TIMER_KEEP);
403 /* Caller should be in critical section */
404 static struct tcpcb *
405 tcp_timer_persist_handler(struct tcpcb *tp)
412 ostate = tp->t_state;
415 * Persistance timer into zero window.
416 * Force a byte to be output, if possible.
418 tcpstat.tcps_persisttimeo++;
420 * Hack: if the peer is dead/unreachable, we do not
421 * time out if the window is closed. After a full
422 * backoff, drop the connection if the idle time
423 * (no responses to probes) reaches the maximum
424 * backoff that we would use if retransmitting.
426 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
427 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle ||
428 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
429 tcpstat.tcps_persistdrop++;
430 tp = tcp_drop(tp, ETIMEDOUT);
434 tp->t_flags |= TF_FORCE;
436 tp->t_flags &= ~TF_FORCE;
440 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
441 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
447 tcp_timer_persist(void *xtp)
449 struct tcpcb *tp = xtp;
450 struct callout *co = &tp->tt_persist->tc_callout;
453 if (callout_pending(co) || !callout_active(co)){
457 callout_deactivate(co);
458 tcp_send_timermsg(tp, TCP_TIMER_PERSIST);
463 tcp_save_congestion_state(struct tcpcb *tp)
466 * Record connection's current states so that they could be
467 * recovered, if this turns out to be a spurious retransmit.
469 tp->snd_cwnd_prev = tp->snd_cwnd;
470 tp->snd_wacked_prev = tp->snd_wacked;
471 tp->snd_ssthresh_prev = tp->snd_ssthresh;
472 tp->snd_recover_prev = tp->snd_recover;
475 * State for Eifel response after spurious timeout retransmit
476 * is detected. We save the current value of snd_max even if
477 * we are called from fast retransmit code, so if RTO needs
478 * rebase, it will be rebased using the RTT of segment that
479 * is not sent during possible congestion.
481 tp->snd_max_prev = tp->snd_max;
483 if (IN_FASTRECOVERY(tp))
484 tp->rxt_flags |= TRXT_F_WASFRECOVERY;
486 tp->rxt_flags &= ~TRXT_F_WASFRECOVERY;
487 if (tp->t_flags & TF_RCVD_TSTMP) {
488 /* States for Eifel detection */
489 tp->t_rexmtTS = ticks;
490 tp->rxt_flags |= TRXT_F_FIRSTACCACK;
493 tcp_sack_save_scoreboard(&tp->scb);
498 tcp_revert_congestion_state(struct tcpcb *tp)
500 tp->snd_cwnd = tp->snd_cwnd_prev;
501 tp->snd_wacked = tp->snd_wacked_prev;
502 tp->snd_ssthresh = tp->snd_ssthresh_prev;
503 tp->snd_recover = tp->snd_recover_prev;
504 if (tp->rxt_flags & TRXT_F_WASFRECOVERY)
505 ENTER_FASTRECOVERY(tp);
506 if (tp->rxt_flags & TRXT_F_FASTREXMT) {
507 ++tcpstat.tcps_sndfastrexmitbad;
508 if (tp->rxt_flags & TRXT_F_EARLYREXMT)
509 ++tcpstat.tcps_sndearlyrexmitbad;
511 ++tcpstat.tcps_sndrtobad;
512 tp->snd_last = ticks;
513 if (tcp_do_eifel_response)
514 tp->rxt_flags |= TRXT_F_REBASERTO;
518 tp->snd_nxt = tp->snd_max;
520 tcp_sack_revert_scoreboard(&tp->scb, tp->snd_una);
524 /* Caller should be in critical section */
525 static struct tcpcb *
526 tcp_timer_rexmt_handler(struct tcpcb *tp)
534 ostate = tp->t_state;
537 * Retransmission timer went off. Message has not
538 * been acked within retransmit interval. Back off
539 * to a longer retransmit interval and retransmit one segment.
541 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
542 tp->t_rxtshift = TCP_MAXRXTSHIFT;
543 tcpstat.tcps_timeoutdrop++;
544 tp = tcp_drop(tp, tp->t_softerror ?
545 tp->t_softerror : ETIMEDOUT);
548 if (tp->t_rxtshift == 1) {
554 * State for "RTT based spurious timeout retransmit detection"
556 * RTT based spurious timeout retransmit detection:
557 * A retransmit is considered spurious if an ACK for this
558 * segment is received within RTT/2 interval; the assumption
559 * here is that the ACK was already in flight. See
560 * "On Estimating End-to-End Network Path Properties" by
561 * Allman and Paxson for more details.
563 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
566 * States for Eifel response after spurious timeout retransmit
569 tp->t_rxtcur_prev = tp->t_rxtcur;
570 tp->t_srtt_prev = tp->t_srtt +
571 (tcp_eifel_rtoinc << TCP_RTT_SHIFT);
572 tp->t_rttvar_prev = tp->t_rttvar;
574 tcp_save_congestion_state(tp);
575 tp->rxt_flags &= ~(TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT |
578 if (tp->t_state == TCPS_SYN_SENT || tp->t_state == TCPS_SYN_RECEIVED) {
580 * Record the time that we spent in SYN or SYN|ACK
583 * Needed by RFC3390 and RFC6298.
585 tp->t_rxtsyn += tp->t_rxtcur;
587 /* Throw away SACK blocks on a RTO, as specified by RFC2018. */
588 tcp_sack_discard(tp);
589 tcpstat.tcps_rexmttimeo++;
590 if (tp->t_state == TCPS_SYN_SENT) {
591 if (tcp_low_rtobase) {
592 rexmt = TCP_REXMTVAL(tp) *
593 tcp_syn_backoff_low[tp->t_rxtshift];
595 rexmt = TCP_REXMTVAL(tp) *
596 tcp_syn_backoff[tp->t_rxtshift];
599 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
601 TCPT_RANGESET(tp->t_rxtcur, rexmt,
602 tp->t_rttmin, TCPTV_REXMTMAX);
604 * If losing, let the lower level know and try for
605 * a better route. Also, if we backed off this far,
606 * our srtt estimate is probably bogus. Clobber it
607 * so we'll take the next rtt measurement as our srtt;
608 * move the current srtt into rttvar to keep the current
609 * retransmit times until then.
611 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
613 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
614 in6_losing(tp->t_inpcb);
617 in_losing(tp->t_inpcb);
618 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
621 tp->snd_nxt = tp->snd_una;
622 tp->snd_recover = tp->snd_max;
624 * Force a segment to be sent.
626 tp->t_flags |= TF_ACKNOW;
628 * If timing a segment in this window, stop the timer.
632 * Close the congestion window down to one segment
633 * (we'll open it by one segment for each ack we get).
634 * Since we probably have a window's worth of unacked
635 * data accumulated, this "slow start" keeps us from
636 * dumping all that data as back-to-back packets (which
637 * might overwhelm an intermediate gateway).
639 * There are two phases to the opening: Initially we
640 * open by one mss on each ack. This makes the window
641 * size increase exponentially with time. If the
642 * window is larger than the path can handle, this
643 * exponential growth results in dropped packet(s)
644 * almost immediately. To get more time between
645 * drops but still "push" the network to take advantage
646 * of improving conditions, we switch from exponential
647 * to linear window opening at some threshhold size.
648 * For a threshhold, we use half the current window
649 * size, truncated to a multiple of the mss.
651 * (the minimum cwnd that will give us exponential
652 * growth is 2 mss. We don't allow the threshhold
656 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
660 tp->snd_cwnd = tp->t_maxseg;
662 tp->snd_ssthresh = win * tp->t_maxseg;
665 EXIT_FASTRECOVERY(tp);
670 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
671 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
677 tcp_timer_rexmt(void *xtp)
679 struct tcpcb *tp = xtp;
680 struct callout *co = &tp->tt_rexmt->tc_callout;
683 if (callout_pending(co) || !callout_active(co)) {
687 callout_deactivate(co);
688 tcp_send_timermsg(tp, TCP_TIMER_REXMT);
693 tcp_timer_handler(netmsg_t msg)
695 struct netmsg_tcp_timer *tmsg = (struct netmsg_tcp_timer *)msg;
696 const struct tcp_timer *tt;
701 KKASSERT(tmsg->tt_cpuid == mycpuid && tmsg->tt_tcb != NULL);
704 /* Save pending tasks and reset the tasks in message */
705 tmsg->tt_running_tasks = tmsg->tt_tasks;
706 tmsg->tt_prev_tasks = tmsg->tt_tasks;
710 lwkt_replymsg(&tmsg->tt_msg.lmsg, 0);
712 if (tmsg->tt_running_tasks == 0) {
714 * All of the timers are cancelled when the message
715 * is pending; bail out.
721 for (tt = tcp_timer_handlers; tt->tt_handler != NULL; ++tt) {
722 if ((tmsg->tt_running_tasks & tt->tt_task) == 0)
725 tmsg->tt_running_tasks &= ~tt->tt_task;
726 tp = tt->tt_handler(tp);
730 if (tmsg->tt_running_tasks == 0) /* nothing left to do */
738 tcp_create_timermsg(struct tcpcb *tp, struct lwkt_port *msgport)
740 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
742 netmsg_init(&tmsg->tt_msg, NULL, &netisr_adone_rport,
743 MSGF_DROPABLE | MSGF_PRIORITY, tcp_timer_handler);
744 tmsg->tt_cpuid = mycpuid;
745 tmsg->tt_msgport = msgport;
751 tcp_destroy_timermsg(struct tcpcb *tp)
753 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
755 if (tmsg == NULL || /* listen socket */
756 tmsg->tt_tcb == NULL) /* only tcp_attach() is called */
759 KKASSERT(tmsg->tt_cpuid == mycpuid);
762 * This message is still pending to be processed;
763 * drop it. Optimized.
766 if ((tmsg->tt_msg.lmsg.ms_flags & MSGF_DONE) == 0) {
767 lwkt_dropmsg(&tmsg->tt_msg.lmsg);
773 tcp_callout_init(struct tcp_callout *tc, uint32_t task)
775 callout_init_mp(&tc->tc_callout);
780 tcp_inittimers(struct tcpcb *tp)
782 tcp_callout_init(tp->tt_rexmt, TCP_TIMER_REXMT);
783 tcp_callout_init(tp->tt_persist, TCP_TIMER_PERSIST);
784 tcp_callout_init(tp->tt_keep, TCP_TIMER_KEEP);
785 tcp_callout_init(tp->tt_2msl, TCP_TIMER_2MSL);
786 tcp_callout_init(tp->tt_delack, TCP_TIMER_DELACK);