2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
5 * The Regents of the University of California. All rights reserved.
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8 * modification, are permitted provided that the following conditions
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16 * may be used to endorse or promote products derived from this software
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31 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
38 #include "opt_inet6.h"
39 #include "opt_tcpdebug.h"
42 #include <sys/param.h>
43 #include <sys/kernel.h>
46 #include <sys/mutex.h>
47 #include <sys/protosw.h>
49 #include <sys/socket.h>
50 #include <sys/socketvar.h>
51 #include <sys/sysctl.h>
52 #include <sys/systm.h>
55 #include <net/route.h>
56 #include <net/rss_config.h>
58 #include <net/netisr.h>
60 #include <netinet/in.h>
61 #include <netinet/in_kdtrace.h>
62 #include <netinet/in_pcb.h>
63 #include <netinet/in_rss.h>
64 #include <netinet/in_systm.h>
66 #include <netinet6/in6_pcb.h>
68 #include <netinet/ip_var.h>
69 #include <netinet/tcp.h>
70 #include <netinet/tcp_fsm.h>
71 #include <netinet/tcp_log_buf.h>
72 #include <netinet/tcp_timer.h>
73 #include <netinet/tcp_var.h>
74 #include <netinet/tcp_seq.h>
75 #include <netinet/cc/cc.h>
77 #include <netinet6/tcp6_var.h>
79 #include <netinet/tcpip.h>
81 #include <netinet/tcp_debug.h>
85 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
86 &tcp_persmin, 0, sysctl_msec_to_ticks, "I", "minimum persistence interval");
89 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
90 &tcp_persmax, 0, sysctl_msec_to_ticks, "I", "maximum persistence interval");
93 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
94 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
97 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
98 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
101 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
102 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
105 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
106 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
107 "Time before a delayed ACK is sent");
110 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
111 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
113 int tcp_rexmit_initial;
114 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial, CTLTYPE_INT|CTLFLAG_RW,
115 &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
116 "Initial Retransmission Timeout");
119 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
120 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
121 "Minimum Retransmission Timeout");
124 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
125 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
126 "Retransmission Timer Slop");
128 VNET_DEFINE(int, tcp_always_keepalive) = 1;
129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW,
130 &VNET_NAME(tcp_always_keepalive) , 0,
131 "Assume SO_KEEPALIVE on all TCP connections");
133 int tcp_fast_finwait2_recycle = 0;
134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
135 &tcp_fast_finwait2_recycle, 0,
136 "Recycle closed FIN_WAIT_2 connections faster");
138 int tcp_finwait2_timeout;
139 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
140 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
142 int tcp_keepcnt = TCPTV_KEEPCNT;
143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
144 "Number of keepalive probes to send");
146 /* max idle probes */
147 int tcp_maxpersistidle;
149 int tcp_rexmit_drop_options = 0;
150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
151 &tcp_rexmit_drop_options, 0,
152 "Drop TCP options from 3rd and later retransmitted SYN");
154 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
156 CTLFLAG_RW|CTLFLAG_VNET,
157 &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
158 "Path MTU Discovery Black Hole Detection Enabled");
161 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
163 CTLFLAG_RW|CTLFLAG_VNET,
164 &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
165 "Path MTU Discovery Black Hole Detection lowered MSS");
169 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
171 CTLFLAG_RW|CTLFLAG_VNET,
172 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
173 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
177 static int per_cpu_timers = 1;
179 static int per_cpu_timers = 0;
181 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
182 &per_cpu_timers , 0, "run tcp timers on all cpus");
185 * Map the given inp to a CPU id.
187 * This queries RSS if it's compiled in, else it defaults to the current
191 inp_to_cpuid(struct inpcb *inp)
196 if (per_cpu_timers) {
197 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
198 if (cpuid == NETISR_CPUID_NONE)
199 return (curcpu); /* XXX */
204 /* Legacy, pre-RSS behaviour */
205 if (per_cpu_timers) {
207 * We don't have a flowid -> cpuid mapping, so cheat and
208 * just map unknown cpuids to curcpu. Not the best, but
209 * apparently better than defaulting to swi 0.
211 cpuid = inp->inp_flowid % (mp_maxid + 1);
212 if (! CPU_ABSENT(cpuid))
217 /* Default for RSS and non-RSS - cpuid 0 */
224 * Tcp protocol timeout routine called every 500 ms.
225 * Updates timestamps used for TCP
226 * causes finite state machine actions if timers expire.
231 VNET_ITERATOR_DECL(vnet_iter);
233 VNET_LIST_RLOCK_NOSLEEP();
234 VNET_FOREACH(vnet_iter) {
235 CURVNET_SET(vnet_iter);
236 (void) tcp_tw_2msl_scan(0);
239 VNET_LIST_RUNLOCK_NOSLEEP();
242 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
243 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
245 int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
248 * TCP timer processing.
252 tcp_timer_delack(void *xtp)
254 struct epoch_tracker et;
255 struct tcpcb *tp = xtp;
257 CURVNET_SET(tp->t_vnet);
260 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
262 if (callout_pending(&tp->t_timers->tt_delack) ||
263 !callout_active(&tp->t_timers->tt_delack)) {
268 callout_deactivate(&tp->t_timers->tt_delack);
269 if ((inp->inp_flags & INP_DROPPED) != 0) {
274 tp->t_flags |= TF_ACKNOW;
275 TCPSTAT_INC(tcps_delack);
277 (void) tp->t_fb->tfb_tcp_output(tp);
284 tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
286 if (inp && tp != NULL)
291 tcp_timer_2msl(void *xtp)
293 struct tcpcb *tp = xtp;
295 struct epoch_tracker et;
296 CURVNET_SET(tp->t_vnet);
300 ostate = tp->t_state;
303 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
305 tcp_free_sackholes(tp);
306 if (callout_pending(&tp->t_timers->tt_2msl) ||
307 !callout_active(&tp->t_timers->tt_2msl)) {
308 INP_WUNLOCK(tp->t_inpcb);
312 callout_deactivate(&tp->t_timers->tt_2msl);
313 if ((inp->inp_flags & INP_DROPPED) != 0) {
318 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
319 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
321 * 2 MSL timeout in shutdown went off. If we're closed but
322 * still waiting for peer to close and connection has been idle
323 * too long delete connection control block. Otherwise, check
326 * If in TIME_WAIT state just ignore as this timeout is handled in
327 * tcp_tw_2msl_scan().
329 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
330 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
331 * Ignore fact that there were recent incoming segments.
333 if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
338 if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
339 tp->t_inpcb && tp->t_inpcb->inp_socket &&
340 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
341 TCPSTAT_INC(tcps_finwait2_drops);
342 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
343 tcp_inpinfo_lock_del(inp, tp);
349 tcp_inpinfo_lock_del(inp, tp);
352 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
353 callout_reset(&tp->t_timers->tt_2msl,
354 TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
356 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
357 tcp_inpinfo_lock_del(inp, tp);
363 tcp_inpinfo_lock_del(inp, tp);
369 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
370 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
373 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
382 tcp_timer_keep(void *xtp)
384 struct tcpcb *tp = xtp;
385 struct tcptemp *t_template;
387 struct epoch_tracker et;
388 CURVNET_SET(tp->t_vnet);
392 ostate = tp->t_state;
395 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
397 if (callout_pending(&tp->t_timers->tt_keep) ||
398 !callout_active(&tp->t_timers->tt_keep)) {
403 callout_deactivate(&tp->t_timers->tt_keep);
404 if ((inp->inp_flags & INP_DROPPED) != 0) {
409 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
410 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
413 * Because we don't regularly reset the keepalive callout in
414 * the ESTABLISHED state, it may be that we don't actually need
415 * to send a keepalive yet. If that occurs, schedule another
416 * call for the next time the keepalive timer might expire.
418 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
421 idletime = ticks - tp->t_rcvtime;
422 if (idletime < TP_KEEPIDLE(tp)) {
423 callout_reset(&tp->t_timers->tt_keep,
424 TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
432 * Keep-alive timer went off; send something
433 * or drop connection if idle for too long.
435 TCPSTAT_INC(tcps_keeptimeo);
436 if (tp->t_state < TCPS_ESTABLISHED)
438 if ((V_tcp_always_keepalive ||
439 inp->inp_socket->so_options & SO_KEEPALIVE) &&
440 tp->t_state <= TCPS_CLOSING) {
441 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
444 * Send a packet designed to force a response
445 * if the peer is up and reachable:
446 * either an ACK if the connection is still alive,
447 * or an RST if the peer has closed the connection
448 * due to timeout or reboot.
449 * Using sequence number tp->snd_una-1
450 * causes the transmitted zero-length segment
451 * to lie outside the receive window;
452 * by the protocol spec, this requires the
453 * correspondent TCP to respond.
455 TCPSTAT_INC(tcps_keepprobe);
456 t_template = tcpip_maketemplate(inp);
459 tcp_respond(tp, t_template->tt_ipgen,
460 &t_template->tt_t, (struct mbuf *)NULL,
461 tp->rcv_nxt, tp->snd_una - 1, 0);
463 free(t_template, M_TEMP);
465 callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
468 callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
472 if (inp->inp_socket->so_options & SO_DEBUG)
473 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
476 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
482 TCPSTAT_INC(tcps_keepdrops);
483 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
484 tcp_inpinfo_lock_del(inp, tp);
488 tp = tcp_drop(tp, ETIMEDOUT);
491 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
492 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
495 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
497 tcp_inpinfo_lock_del(inp, tp);
503 tcp_timer_persist(void *xtp)
505 struct tcpcb *tp = xtp;
507 struct epoch_tracker et;
508 CURVNET_SET(tp->t_vnet);
512 ostate = tp->t_state;
515 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
517 if (callout_pending(&tp->t_timers->tt_persist) ||
518 !callout_active(&tp->t_timers->tt_persist)) {
523 callout_deactivate(&tp->t_timers->tt_persist);
524 if ((inp->inp_flags & INP_DROPPED) != 0) {
529 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
530 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
532 * Persistence timer into zero window.
533 * Force a byte to be output, if possible.
535 TCPSTAT_INC(tcps_persisttimeo);
537 * Hack: if the peer is dead/unreachable, we do not
538 * time out if the window is closed. After a full
539 * backoff, drop the connection if the idle time
540 * (no responses to probes) reaches the maximum
541 * backoff that we would use if retransmitting.
543 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
544 (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
545 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
546 TCPSTAT_INC(tcps_persistdrop);
547 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
548 tcp_inpinfo_lock_del(inp, tp);
552 tp = tcp_drop(tp, ETIMEDOUT);
554 tcp_inpinfo_lock_del(inp, tp);
558 * If the user has closed the socket then drop a persisting
559 * connection after a much reduced timeout.
561 if (tp->t_state > TCPS_CLOSE_WAIT &&
562 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
563 TCPSTAT_INC(tcps_persistdrop);
564 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
565 tcp_inpinfo_lock_del(inp, tp);
569 tp = tcp_drop(tp, ETIMEDOUT);
571 tcp_inpinfo_lock_del(inp, tp);
575 tp->t_flags |= TF_FORCEDATA;
577 (void) tp->t_fb->tfb_tcp_output(tp);
579 tp->t_flags &= ~TF_FORCEDATA;
582 if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
583 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
585 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
592 tcp_timer_rexmt(void * xtp)
594 struct tcpcb *tp = xtp;
595 CURVNET_SET(tp->t_vnet);
598 struct epoch_tracker et;
602 ostate = tp->t_state;
605 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
607 if (callout_pending(&tp->t_timers->tt_rexmt) ||
608 !callout_active(&tp->t_timers->tt_rexmt)) {
613 callout_deactivate(&tp->t_timers->tt_rexmt);
614 if ((inp->inp_flags & INP_DROPPED) != 0) {
619 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
620 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
621 tcp_free_sackholes(tp);
622 TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false);
623 if (tp->t_fb->tfb_tcp_rexmit_tmr) {
624 /* The stack has a timer action too. */
625 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
628 * Retransmission timer went off. Message has not
629 * been acked within retransmit interval. Back off
630 * to a longer retransmit interval and retransmit one segment.
632 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
633 tp->t_rxtshift = TCP_MAXRXTSHIFT;
634 TCPSTAT_INC(tcps_timeoutdrop);
635 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
636 tcp_inpinfo_lock_del(inp, tp);
640 tp = tcp_drop(tp, ETIMEDOUT);
642 tcp_inpinfo_lock_del(inp, tp);
645 if (tp->t_state == TCPS_SYN_SENT) {
647 * If the SYN was retransmitted, indicate CWND to be
648 * limited to 1 segment in cc_conn_init().
651 } else if (tp->t_rxtshift == 1) {
653 * first retransmit; record ssthresh and cwnd so they can
654 * be recovered if this turns out to be a "bad" retransmit.
655 * A retransmit is considered "bad" if an ACK for this
656 * segment is received within RTT/2 interval; the assumption
657 * here is that the ACK was already in flight. See
658 * "On Estimating End-to-End Network Path Properties" by
659 * Allman and Paxson for more details.
661 tp->snd_cwnd_prev = tp->snd_cwnd;
662 tp->snd_ssthresh_prev = tp->snd_ssthresh;
663 tp->snd_recover_prev = tp->snd_recover;
664 if (IN_FASTRECOVERY(tp->t_flags))
665 tp->t_flags |= TF_WASFRECOVERY;
667 tp->t_flags &= ~TF_WASFRECOVERY;
668 if (IN_CONGRECOVERY(tp->t_flags))
669 tp->t_flags |= TF_WASCRECOVERY;
671 tp->t_flags &= ~TF_WASCRECOVERY;
672 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
673 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
674 /* In the event that we've negotiated timestamps
675 * badrxtwin will be set to the value that we set
676 * the retransmitted packet's to_tsval to by tcp_output
678 tp->t_flags |= TF_PREVVALID;
680 tp->t_flags &= ~TF_PREVVALID;
681 TCPSTAT_INC(tcps_rexmttimeo);
682 if ((tp->t_state == TCPS_SYN_SENT) ||
683 (tp->t_state == TCPS_SYN_RECEIVED))
684 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
686 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
687 TCPT_RANGESET(tp->t_rxtcur, rexmt,
688 tp->t_rttmin, TCPTV_REXMTMAX);
691 * We enter the path for PLMTUD if connection is established or, if
692 * connection is FIN_WAIT_1 status, reason for the last is that if
693 * amount of data we send is very small, we could send it in couple of
694 * packets and process straight to FIN. In that case we won't catch
697 if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
698 || (tp->t_state == TCPS_FIN_WAIT_1))) {
704 * Idea here is that at each stage of mtu probe (usually, 1448
705 * -> 1188 -> 524) should be given 2 chances to recover before
706 * further clamping down. 'tp->t_rxtshift % 2 == 0' should
709 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
710 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
711 (tp->t_rxtshift >= 2 && tp->t_rxtshift < 6 &&
712 tp->t_rxtshift % 2 == 0)) {
714 * Enter Path MTU Black-hole Detection mechanism:
715 * - Disable Path MTU Discovery (IP "DF" bit).
716 * - Reduce MTU to lower value than what we
717 * negotiated with peer.
719 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
720 /* Record that we may have found a black hole. */
721 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
722 /* Keep track of previous MSS. */
723 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
727 * Reduce the MSS to blackhole value or to the default
728 * in an attempt to retransmit.
731 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
733 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
734 /* Use the sysctl tuneable blackhole MSS. */
735 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
736 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
738 /* Use the default MSS. */
739 tp->t_maxseg = V_tcp_v6mssdflt;
741 * Disable Path MTU Discovery when we switch to
744 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
745 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
748 #if defined(INET6) && defined(INET)
752 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) {
753 /* Use the sysctl tuneable blackhole MSS. */
754 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
755 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
757 /* Use the default MSS. */
758 tp->t_maxseg = V_tcp_mssdflt;
760 * Disable Path MTU Discovery when we switch to
763 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
764 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
768 * Reset the slow-start flight size
769 * as it may depend on the new MSS.
771 if (CC_ALGO(tp)->conn_init != NULL)
772 CC_ALGO(tp)->conn_init(tp->ccv);
775 * If further retransmissions are still unsuccessful
776 * with a lowered MTU, maybe this isn't a blackhole and
777 * we restore the previous MSS and blackhole detection
779 * The limit '6' is determined by giving each probe
780 * stage (1448, 1188, 524) 2 chances to recover.
782 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
783 (tp->t_rxtshift >= 6)) {
784 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
785 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
786 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
787 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
789 * Reset the slow-start flight size as it
790 * may depend on the new MSS.
792 if (CC_ALGO(tp)->conn_init != NULL)
793 CC_ALGO(tp)->conn_init(tp->ccv);
799 * Disable RFC1323 and SACK if we haven't got any response to
800 * our third SYN to work-around some broken terminal servers
801 * (most of which have hopefully been retired) that have bad VJ
802 * header compression code which trashes TCP segments containing
803 * unknown-to-them TCP options.
805 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
806 (tp->t_rxtshift == 3))
807 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
809 * If we backed off this far, notify the L3 protocol that we're having
810 * connection problems.
812 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
814 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
815 in6_losing(tp->t_inpcb);
818 in_losing(tp->t_inpcb);
820 tp->snd_nxt = tp->snd_una;
821 tp->snd_recover = tp->snd_max;
823 * Force a segment to be sent.
825 tp->t_flags |= TF_ACKNOW;
827 * If timing a segment in this window, stop the timer.
831 cc_cong_signal(tp, NULL, CC_RTO);
833 (void) tp->t_fb->tfb_tcp_output(tp);
836 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
837 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
840 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
847 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
849 struct callout *t_callout;
850 callout_func_t *f_callout;
851 struct inpcb *inp = tp->t_inpcb;
852 int cpu = inp_to_cpuid(inp);
855 if (tp->t_flags & TF_TOE)
859 if (tp->t_timers->tt_flags & TT_STOPPED)
862 switch (timer_type) {
864 t_callout = &tp->t_timers->tt_delack;
865 f_callout = tcp_timer_delack;
868 t_callout = &tp->t_timers->tt_rexmt;
869 f_callout = tcp_timer_rexmt;
872 t_callout = &tp->t_timers->tt_persist;
873 f_callout = tcp_timer_persist;
876 t_callout = &tp->t_timers->tt_keep;
877 f_callout = tcp_timer_keep;
880 t_callout = &tp->t_timers->tt_2msl;
881 f_callout = tcp_timer_2msl;
884 if (tp->t_fb->tfb_tcp_timer_activate) {
885 tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
888 panic("tp %p bad timer_type %#x", tp, timer_type);
891 callout_stop(t_callout);
893 callout_reset_on(t_callout, delta, f_callout, tp, cpu);
898 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
900 struct callout *t_callout;
902 switch (timer_type) {
904 t_callout = &tp->t_timers->tt_delack;
907 t_callout = &tp->t_timers->tt_rexmt;
910 t_callout = &tp->t_timers->tt_persist;
913 t_callout = &tp->t_timers->tt_keep;
916 t_callout = &tp->t_timers->tt_2msl;
919 if (tp->t_fb->tfb_tcp_timer_active) {
920 return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
922 panic("tp %p bad timer_type %#x", tp, timer_type);
924 return callout_active(t_callout);
928 * Stop the timer from running, and apply a flag
929 * against the timer_flags that will force the
930 * timer never to run. The flag is needed to assure
931 * a race does not leave it running and cause
932 * the timer to possibly restart itself (keep and persist
933 * especially do this).
936 tcp_timer_suspend(struct tcpcb *tp, uint32_t timer_type)
938 struct callout *t_callout;
941 switch (timer_type) {
943 t_flags = TT_DELACK_SUS;
944 t_callout = &tp->t_timers->tt_delack;
947 t_flags = TT_REXMT_SUS;
948 t_callout = &tp->t_timers->tt_rexmt;
951 t_flags = TT_PERSIST_SUS;
952 t_callout = &tp->t_timers->tt_persist;
955 t_flags = TT_KEEP_SUS;
956 t_callout = &tp->t_timers->tt_keep;
959 t_flags = TT_2MSL_SUS;
960 t_callout = &tp->t_timers->tt_2msl;
963 panic("tp:%p bad timer_type 0x%x", tp, timer_type);
965 tp->t_timers->tt_flags |= t_flags;
966 return (callout_stop(t_callout));
970 tcp_timers_unsuspend(struct tcpcb *tp, uint32_t timer_type)
972 switch (timer_type) {
974 if (tp->t_timers->tt_flags & TT_DELACK_SUS) {
975 tp->t_timers->tt_flags &= ~TT_DELACK_SUS;
976 if (tp->t_flags & TF_DELACK) {
977 /* Delayed ack timer should be up activate a timer */
978 tp->t_flags &= ~TF_DELACK;
979 tcp_timer_activate(tp, TT_DELACK,
985 if (tp->t_timers->tt_flags & TT_REXMT_SUS) {
986 tp->t_timers->tt_flags &= ~TT_REXMT_SUS;
987 if (SEQ_GT(tp->snd_max, tp->snd_una) &&
988 (tcp_timer_active((tp), TT_PERSIST) == 0) &&
990 /* We have outstanding data activate a timer */
991 tcp_timer_activate(tp, TT_REXMT,
997 if (tp->t_timers->tt_flags & TT_PERSIST_SUS) {
998 tp->t_timers->tt_flags &= ~TT_PERSIST_SUS;
999 if (tp->snd_wnd == 0) {
1000 /* Activate the persists timer */
1007 if (tp->t_timers->tt_flags & TT_KEEP_SUS) {
1008 tp->t_timers->tt_flags &= ~TT_KEEP_SUS;
1009 tcp_timer_activate(tp, TT_KEEP,
1010 TCPS_HAVEESTABLISHED(tp->t_state) ?
1011 TP_KEEPIDLE(tp) : TP_KEEPINIT(tp));
1015 if (tp->t_timers->tt_flags &= TT_2MSL_SUS) {
1016 tp->t_timers->tt_flags &= ~TT_2MSL_SUS;
1017 if ((tp->t_state == TCPS_FIN_WAIT_2) &&
1018 ((tp->t_inpcb->inp_socket == NULL) ||
1019 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE))) {
1020 /* Star the 2MSL timer */
1021 tcp_timer_activate(tp, TT_2MSL,
1022 (tcp_fast_finwait2_recycle) ?
1023 tcp_finwait2_timeout : TP_MAXIDLE(tp));
1028 panic("tp:%p bad timer_type 0x%x", tp, timer_type);
1033 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
1035 struct callout *t_callout;
1037 tp->t_timers->tt_flags |= TT_STOPPED;
1038 switch (timer_type) {
1040 t_callout = &tp->t_timers->tt_delack;
1043 t_callout = &tp->t_timers->tt_rexmt;
1046 t_callout = &tp->t_timers->tt_persist;
1049 t_callout = &tp->t_timers->tt_keep;
1052 t_callout = &tp->t_timers->tt_2msl;
1055 if (tp->t_fb->tfb_tcp_timer_stop) {
1057 * XXXrrs we need to look at this with the
1058 * stop case below (flags).
1060 tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
1063 panic("tp %p bad timer_type %#x", tp, timer_type);
1066 if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
1068 * Can't stop the callout, defer tcpcb actual deletion
1069 * to the last one. We do this using the async drain
1070 * function and incrementing the count in
1072 tp->t_timers->tt_draincnt++;