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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19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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");
114 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
115 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
116 "Minimum Retransmission Timeout");
119 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
120 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
121 "Retransmission Timer Slop");
123 int tcp_always_keepalive = 1;
124 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
125 &tcp_always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
127 int tcp_fast_finwait2_recycle = 0;
128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
129 &tcp_fast_finwait2_recycle, 0,
130 "Recycle closed FIN_WAIT_2 connections faster");
132 int tcp_finwait2_timeout;
133 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
134 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
136 int tcp_keepcnt = TCPTV_KEEPCNT;
137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
138 "Number of keepalive probes to send");
140 /* max idle probes */
141 int tcp_maxpersistidle;
143 int tcp_rexmit_drop_options = 0;
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
145 &tcp_rexmit_drop_options, 0,
146 "Drop TCP options from 3rd and later retransmitted SYN");
148 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
149 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
150 CTLFLAG_RW|CTLFLAG_VNET,
151 &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
152 "Path MTU Discovery Black Hole Detection Enabled");
155 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
157 CTLFLAG_RW|CTLFLAG_VNET,
158 &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
159 "Path MTU Discovery Black Hole Detection lowered MSS");
163 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
165 CTLFLAG_RW|CTLFLAG_VNET,
166 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
167 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
171 static int per_cpu_timers = 1;
173 static int per_cpu_timers = 0;
175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
176 &per_cpu_timers , 0, "run tcp timers on all cpus");
179 * Map the given inp to a CPU id.
181 * This queries RSS if it's compiled in, else it defaults to the current
185 inp_to_cpuid(struct inpcb *inp)
190 if (per_cpu_timers) {
191 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
192 if (cpuid == NETISR_CPUID_NONE)
193 return (curcpu); /* XXX */
198 /* Legacy, pre-RSS behaviour */
199 if (per_cpu_timers) {
201 * We don't have a flowid -> cpuid mapping, so cheat and
202 * just map unknown cpuids to curcpu. Not the best, but
203 * apparently better than defaulting to swi 0.
205 cpuid = inp->inp_flowid % (mp_maxid + 1);
206 if (! CPU_ABSENT(cpuid))
211 /* Default for RSS and non-RSS - cpuid 0 */
218 * Tcp protocol timeout routine called every 500 ms.
219 * Updates timestamps used for TCP
220 * causes finite state machine actions if timers expire.
225 VNET_ITERATOR_DECL(vnet_iter);
227 VNET_LIST_RLOCK_NOSLEEP();
228 VNET_FOREACH(vnet_iter) {
229 CURVNET_SET(vnet_iter);
230 (void) tcp_tw_2msl_scan(0);
233 VNET_LIST_RUNLOCK_NOSLEEP();
236 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
237 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
239 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
240 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
242 int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
245 * TCP timer processing.
249 tcp_timer_delack(void *xtp)
251 struct tcpcb *tp = xtp;
253 CURVNET_SET(tp->t_vnet);
256 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
258 if (callout_pending(&tp->t_timers->tt_delack) ||
259 !callout_active(&tp->t_timers->tt_delack)) {
264 callout_deactivate(&tp->t_timers->tt_delack);
265 if ((inp->inp_flags & INP_DROPPED) != 0) {
270 tp->t_flags |= TF_ACKNOW;
271 TCPSTAT_INC(tcps_delack);
272 (void) tp->t_fb->tfb_tcp_output(tp);
278 tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
280 if (inp && tp != NULL)
285 tcp_timer_2msl(void *xtp)
287 struct tcpcb *tp = xtp;
289 struct epoch_tracker et;
290 CURVNET_SET(tp->t_vnet);
294 ostate = tp->t_state;
297 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
299 tcp_free_sackholes(tp);
300 if (callout_pending(&tp->t_timers->tt_2msl) ||
301 !callout_active(&tp->t_timers->tt_2msl)) {
302 INP_WUNLOCK(tp->t_inpcb);
306 callout_deactivate(&tp->t_timers->tt_2msl);
307 if ((inp->inp_flags & INP_DROPPED) != 0) {
312 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
313 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
315 * 2 MSL timeout in shutdown went off. If we're closed but
316 * still waiting for peer to close and connection has been idle
317 * too long delete connection control block. Otherwise, check
320 * If in TIME_WAIT state just ignore as this timeout is handled in
321 * tcp_tw_2msl_scan().
323 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
324 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
325 * Ignore fact that there were recent incoming segments.
327 if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
332 if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
333 tp->t_inpcb && tp->t_inpcb->inp_socket &&
334 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
335 TCPSTAT_INC(tcps_finwait2_drops);
336 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
337 tcp_inpinfo_lock_del(inp, tp);
340 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
342 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
343 tcp_inpinfo_lock_del(inp, tp);
346 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
347 callout_reset(&tp->t_timers->tt_2msl,
348 TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
350 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
351 tcp_inpinfo_lock_del(inp, tp);
354 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
356 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
357 tcp_inpinfo_lock_del(inp, tp);
363 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
364 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
367 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
376 tcp_timer_keep(void *xtp)
378 struct tcpcb *tp = xtp;
379 struct tcptemp *t_template;
381 struct epoch_tracker et;
382 CURVNET_SET(tp->t_vnet);
386 ostate = tp->t_state;
389 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
391 if (callout_pending(&tp->t_timers->tt_keep) ||
392 !callout_active(&tp->t_timers->tt_keep)) {
397 callout_deactivate(&tp->t_timers->tt_keep);
398 if ((inp->inp_flags & INP_DROPPED) != 0) {
403 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
404 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
407 * Because we don't regularly reset the keepalive callout in
408 * the ESTABLISHED state, it may be that we don't actually need
409 * to send a keepalive yet. If that occurs, schedule another
410 * call for the next time the keepalive timer might expire.
412 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
415 idletime = ticks - tp->t_rcvtime;
416 if (idletime < TP_KEEPIDLE(tp)) {
417 callout_reset(&tp->t_timers->tt_keep,
418 TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
426 * Keep-alive timer went off; send something
427 * or drop connection if idle for too long.
429 TCPSTAT_INC(tcps_keeptimeo);
430 if (tp->t_state < TCPS_ESTABLISHED)
432 if ((tcp_always_keepalive ||
433 inp->inp_socket->so_options & SO_KEEPALIVE) &&
434 tp->t_state <= TCPS_CLOSING) {
435 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
438 * Send a packet designed to force a response
439 * if the peer is up and reachable:
440 * either an ACK if the connection is still alive,
441 * or an RST if the peer has closed the connection
442 * due to timeout or reboot.
443 * Using sequence number tp->snd_una-1
444 * causes the transmitted zero-length segment
445 * to lie outside the receive window;
446 * by the protocol spec, this requires the
447 * correspondent TCP to respond.
449 TCPSTAT_INC(tcps_keepprobe);
450 t_template = tcpip_maketemplate(inp);
452 tcp_respond(tp, t_template->tt_ipgen,
453 &t_template->tt_t, (struct mbuf *)NULL,
454 tp->rcv_nxt, tp->snd_una - 1, 0);
455 free(t_template, M_TEMP);
457 callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
460 callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
464 if (inp->inp_socket->so_options & SO_DEBUG)
465 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
468 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
474 TCPSTAT_INC(tcps_keepdrops);
475 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
476 tcp_inpinfo_lock_del(inp, tp);
479 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
480 tp = tcp_drop(tp, ETIMEDOUT);
483 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
484 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
487 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
488 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
489 tcp_inpinfo_lock_del(inp, tp);
495 tcp_timer_persist(void *xtp)
497 struct tcpcb *tp = xtp;
499 struct epoch_tracker et;
500 CURVNET_SET(tp->t_vnet);
504 ostate = tp->t_state;
507 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
509 if (callout_pending(&tp->t_timers->tt_persist) ||
510 !callout_active(&tp->t_timers->tt_persist)) {
515 callout_deactivate(&tp->t_timers->tt_persist);
516 if ((inp->inp_flags & INP_DROPPED) != 0) {
521 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
522 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
524 * Persistence timer into zero window.
525 * Force a byte to be output, if possible.
527 TCPSTAT_INC(tcps_persisttimeo);
529 * Hack: if the peer is dead/unreachable, we do not
530 * time out if the window is closed. After a full
531 * backoff, drop the connection if the idle time
532 * (no responses to probes) reaches the maximum
533 * backoff that we would use if retransmitting.
535 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
536 (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
537 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
538 TCPSTAT_INC(tcps_persistdrop);
539 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
540 tcp_inpinfo_lock_del(inp, tp);
543 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
544 tp = tcp_drop(tp, ETIMEDOUT);
545 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
546 tcp_inpinfo_lock_del(inp, tp);
550 * If the user has closed the socket then drop a persisting
551 * connection after a much reduced timeout.
553 if (tp->t_state > TCPS_CLOSE_WAIT &&
554 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
555 TCPSTAT_INC(tcps_persistdrop);
556 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
557 tcp_inpinfo_lock_del(inp, tp);
560 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
561 tp = tcp_drop(tp, ETIMEDOUT);
562 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
563 tcp_inpinfo_lock_del(inp, tp);
567 tp->t_flags |= TF_FORCEDATA;
568 (void) tp->t_fb->tfb_tcp_output(tp);
569 tp->t_flags &= ~TF_FORCEDATA;
572 if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
573 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
575 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
582 tcp_timer_rexmt(void * xtp)
584 struct tcpcb *tp = xtp;
585 CURVNET_SET(tp->t_vnet);
588 struct epoch_tracker et;
592 ostate = tp->t_state;
595 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
597 if (callout_pending(&tp->t_timers->tt_rexmt) ||
598 !callout_active(&tp->t_timers->tt_rexmt)) {
603 callout_deactivate(&tp->t_timers->tt_rexmt);
604 if ((inp->inp_flags & INP_DROPPED) != 0) {
609 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
610 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
611 tcp_free_sackholes(tp);
612 TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false);
613 if (tp->t_fb->tfb_tcp_rexmit_tmr) {
614 /* The stack has a timer action too. */
615 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
618 * Retransmission timer went off. Message has not
619 * been acked within retransmit interval. Back off
620 * to a longer retransmit interval and retransmit one segment.
622 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
623 tp->t_rxtshift = TCP_MAXRXTSHIFT;
624 TCPSTAT_INC(tcps_timeoutdrop);
625 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
626 tcp_inpinfo_lock_del(inp, tp);
629 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
630 tp = tcp_drop(tp, ETIMEDOUT);
631 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
632 tcp_inpinfo_lock_del(inp, tp);
635 if (tp->t_state == TCPS_SYN_SENT) {
637 * If the SYN was retransmitted, indicate CWND to be
638 * limited to 1 segment in cc_conn_init().
641 } else if (tp->t_rxtshift == 1) {
643 * first retransmit; record ssthresh and cwnd so they can
644 * be recovered if this turns out to be a "bad" retransmit.
645 * A retransmit is considered "bad" if an ACK for this
646 * segment is received within RTT/2 interval; the assumption
647 * here is that the ACK was already in flight. See
648 * "On Estimating End-to-End Network Path Properties" by
649 * Allman and Paxson for more details.
651 tp->snd_cwnd_prev = tp->snd_cwnd;
652 tp->snd_ssthresh_prev = tp->snd_ssthresh;
653 tp->snd_recover_prev = tp->snd_recover;
654 if (IN_FASTRECOVERY(tp->t_flags))
655 tp->t_flags |= TF_WASFRECOVERY;
657 tp->t_flags &= ~TF_WASFRECOVERY;
658 if (IN_CONGRECOVERY(tp->t_flags))
659 tp->t_flags |= TF_WASCRECOVERY;
661 tp->t_flags &= ~TF_WASCRECOVERY;
662 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
663 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
664 /* In the event that we've negotiated timestamps
665 * badrxtwin will be set to the value that we set
666 * the retransmitted packet's to_tsval to by tcp_output
668 tp->t_flags |= TF_PREVVALID;
670 tp->t_flags &= ~TF_PREVVALID;
671 TCPSTAT_INC(tcps_rexmttimeo);
672 if ((tp->t_state == TCPS_SYN_SENT) ||
673 (tp->t_state == TCPS_SYN_RECEIVED))
674 rexmt = TCPTV_RTOBASE * tcp_syn_backoff[tp->t_rxtshift];
676 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
677 TCPT_RANGESET(tp->t_rxtcur, rexmt,
678 tp->t_rttmin, TCPTV_REXMTMAX);
681 * We enter the path for PLMTUD if connection is established or, if
682 * connection is FIN_WAIT_1 status, reason for the last is that if
683 * amount of data we send is very small, we could send it in couple of
684 * packets and process straight to FIN. In that case we won't catch
687 if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
688 || (tp->t_state == TCPS_FIN_WAIT_1))) {
694 * Idea here is that at each stage of mtu probe (usually, 1448
695 * -> 1188 -> 524) should be given 2 chances to recover before
696 * further clamping down. 'tp->t_rxtshift % 2 == 0' should
699 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
700 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
701 (tp->t_rxtshift >= 2 && tp->t_rxtshift < 6 &&
702 tp->t_rxtshift % 2 == 0)) {
704 * Enter Path MTU Black-hole Detection mechanism:
705 * - Disable Path MTU Discovery (IP "DF" bit).
706 * - Reduce MTU to lower value than what we
707 * negotiated with peer.
709 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
710 /* Record that we may have found a black hole. */
711 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
712 /* Keep track of previous MSS. */
713 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
717 * Reduce the MSS to blackhole value or to the default
718 * in an attempt to retransmit.
721 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
723 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
724 /* Use the sysctl tuneable blackhole MSS. */
725 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
726 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
728 /* Use the default MSS. */
729 tp->t_maxseg = V_tcp_v6mssdflt;
731 * Disable Path MTU Discovery when we switch to
734 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
735 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
738 #if defined(INET6) && defined(INET)
742 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) {
743 /* Use the sysctl tuneable blackhole MSS. */
744 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
745 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
747 /* Use the default MSS. */
748 tp->t_maxseg = V_tcp_mssdflt;
750 * Disable Path MTU Discovery when we switch to
753 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
754 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
758 * Reset the slow-start flight size
759 * as it may depend on the new MSS.
761 if (CC_ALGO(tp)->conn_init != NULL)
762 CC_ALGO(tp)->conn_init(tp->ccv);
765 * If further retransmissions are still unsuccessful
766 * with a lowered MTU, maybe this isn't a blackhole and
767 * we restore the previous MSS and blackhole detection
769 * The limit '6' is determined by giving each probe
770 * stage (1448, 1188, 524) 2 chances to recover.
772 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
773 (tp->t_rxtshift >= 6)) {
774 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
775 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
776 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
777 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
779 * Reset the slow-start flight size as it
780 * may depend on the new MSS.
782 if (CC_ALGO(tp)->conn_init != NULL)
783 CC_ALGO(tp)->conn_init(tp->ccv);
789 * Disable RFC1323 and SACK if we haven't got any response to
790 * our third SYN to work-around some broken terminal servers
791 * (most of which have hopefully been retired) that have bad VJ
792 * header compression code which trashes TCP segments containing
793 * unknown-to-them TCP options.
795 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
796 (tp->t_rxtshift == 3))
797 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
799 * If we backed off this far, notify the L3 protocol that we're having
800 * connection problems.
802 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
804 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
805 in6_losing(tp->t_inpcb);
808 in_losing(tp->t_inpcb);
810 tp->snd_nxt = tp->snd_una;
811 tp->snd_recover = tp->snd_max;
813 * Force a segment to be sent.
815 tp->t_flags |= TF_ACKNOW;
817 * If timing a segment in this window, stop the timer.
821 cc_cong_signal(tp, NULL, CC_RTO);
823 (void) tp->t_fb->tfb_tcp_output(tp);
826 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
827 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
830 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
837 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
839 struct callout *t_callout;
840 timeout_t *f_callout;
841 struct inpcb *inp = tp->t_inpcb;
842 int cpu = inp_to_cpuid(inp);
845 if (tp->t_flags & TF_TOE)
849 if (tp->t_timers->tt_flags & TT_STOPPED)
852 switch (timer_type) {
854 t_callout = &tp->t_timers->tt_delack;
855 f_callout = tcp_timer_delack;
858 t_callout = &tp->t_timers->tt_rexmt;
859 f_callout = tcp_timer_rexmt;
862 t_callout = &tp->t_timers->tt_persist;
863 f_callout = tcp_timer_persist;
866 t_callout = &tp->t_timers->tt_keep;
867 f_callout = tcp_timer_keep;
870 t_callout = &tp->t_timers->tt_2msl;
871 f_callout = tcp_timer_2msl;
874 if (tp->t_fb->tfb_tcp_timer_activate) {
875 tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
878 panic("tp %p bad timer_type %#x", tp, timer_type);
881 callout_stop(t_callout);
883 callout_reset_on(t_callout, delta, f_callout, tp, cpu);
888 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
890 struct callout *t_callout;
892 switch (timer_type) {
894 t_callout = &tp->t_timers->tt_delack;
897 t_callout = &tp->t_timers->tt_rexmt;
900 t_callout = &tp->t_timers->tt_persist;
903 t_callout = &tp->t_timers->tt_keep;
906 t_callout = &tp->t_timers->tt_2msl;
909 if (tp->t_fb->tfb_tcp_timer_active) {
910 return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
912 panic("tp %p bad timer_type %#x", tp, timer_type);
914 return callout_active(t_callout);
918 * Stop the timer from running, and apply a flag
919 * against the timer_flags that will force the
920 * timer never to run. The flag is needed to assure
921 * a race does not leave it running and cause
922 * the timer to possibly restart itself (keep and persist
923 * especially do this).
926 tcp_timer_suspend(struct tcpcb *tp, uint32_t timer_type)
928 struct callout *t_callout;
931 switch (timer_type) {
933 t_flags = TT_DELACK_SUS;
934 t_callout = &tp->t_timers->tt_delack;
937 t_flags = TT_REXMT_SUS;
938 t_callout = &tp->t_timers->tt_rexmt;
941 t_flags = TT_PERSIST_SUS;
942 t_callout = &tp->t_timers->tt_persist;
945 t_flags = TT_KEEP_SUS;
946 t_callout = &tp->t_timers->tt_keep;
949 t_flags = TT_2MSL_SUS;
950 t_callout = &tp->t_timers->tt_2msl;
953 panic("tp:%p bad timer_type 0x%x", tp, timer_type);
955 tp->t_timers->tt_flags |= t_flags;
956 return (callout_stop(t_callout));
960 tcp_timers_unsuspend(struct tcpcb *tp, uint32_t timer_type)
962 switch (timer_type) {
964 if (tp->t_timers->tt_flags & TT_DELACK_SUS) {
965 tp->t_timers->tt_flags &= ~TT_DELACK_SUS;
966 if (tp->t_flags & TF_DELACK) {
967 /* Delayed ack timer should be up activate a timer */
968 tp->t_flags &= ~TF_DELACK;
969 tcp_timer_activate(tp, TT_DELACK,
975 if (tp->t_timers->tt_flags & TT_REXMT_SUS) {
976 tp->t_timers->tt_flags &= ~TT_REXMT_SUS;
977 if (SEQ_GT(tp->snd_max, tp->snd_una) &&
978 (tcp_timer_active((tp), TT_PERSIST) == 0) &&
980 /* We have outstanding data activate a timer */
981 tcp_timer_activate(tp, TT_REXMT,
987 if (tp->t_timers->tt_flags & TT_PERSIST_SUS) {
988 tp->t_timers->tt_flags &= ~TT_PERSIST_SUS;
989 if (tp->snd_wnd == 0) {
990 /* Activate the persists timer */
997 if (tp->t_timers->tt_flags & TT_KEEP_SUS) {
998 tp->t_timers->tt_flags &= ~TT_KEEP_SUS;
999 tcp_timer_activate(tp, TT_KEEP,
1000 TCPS_HAVEESTABLISHED(tp->t_state) ?
1001 TP_KEEPIDLE(tp) : TP_KEEPINIT(tp));
1005 if (tp->t_timers->tt_flags &= TT_2MSL_SUS) {
1006 tp->t_timers->tt_flags &= ~TT_2MSL_SUS;
1007 if ((tp->t_state == TCPS_FIN_WAIT_2) &&
1008 ((tp->t_inpcb->inp_socket == NULL) ||
1009 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE))) {
1010 /* Star the 2MSL timer */
1011 tcp_timer_activate(tp, TT_2MSL,
1012 (tcp_fast_finwait2_recycle) ?
1013 tcp_finwait2_timeout : TP_MAXIDLE(tp));
1018 panic("tp:%p bad timer_type 0x%x", tp, timer_type);
1023 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
1025 struct callout *t_callout;
1027 tp->t_timers->tt_flags |= TT_STOPPED;
1028 switch (timer_type) {
1030 t_callout = &tp->t_timers->tt_delack;
1033 t_callout = &tp->t_timers->tt_rexmt;
1036 t_callout = &tp->t_timers->tt_persist;
1039 t_callout = &tp->t_timers->tt_keep;
1042 t_callout = &tp->t_timers->tt_2msl;
1045 if (tp->t_fb->tfb_tcp_timer_stop) {
1047 * XXXrrs we need to look at this with the
1048 * stop case below (flags).
1050 tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
1053 panic("tp %p bad timer_type %#x", tp, timer_type);
1056 if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
1058 * Can't stop the callout, defer tcpcb actual deletion
1059 * to the last one. We do this using the async drain
1060 * function and incrementing the count in
1062 tp->t_timers->tt_draincnt++;