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.
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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 University 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.
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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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"
41 #include <sys/param.h>
42 #include <sys/kernel.h>
45 #include <sys/mutex.h>
46 #include <sys/protosw.h>
48 #include <sys/socket.h>
49 #include <sys/socketvar.h>
50 #include <sys/sysctl.h>
51 #include <sys/systm.h>
54 #include <net/route.h>
55 #include <net/rss_config.h>
57 #include <net/netisr.h>
59 #include <netinet/in.h>
60 #include <netinet/in_kdtrace.h>
61 #include <netinet/in_pcb.h>
62 #include <netinet/in_rss.h>
63 #include <netinet/in_systm.h>
65 #include <netinet6/in6_pcb.h>
67 #include <netinet/ip_var.h>
68 #include <netinet/tcp.h>
69 #include <netinet/tcp_fsm.h>
70 #include <netinet/tcp_timer.h>
71 #include <netinet/tcp_var.h>
72 #include <netinet/tcp_log_buf.h>
73 #include <netinet/tcp_seq.h>
74 #include <netinet/cc/cc.h>
76 #include <netinet6/tcp6_var.h>
78 #include <netinet/tcpip.h>
81 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin,
82 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
83 &tcp_persmin, 0, sysctl_msec_to_ticks, "I",
84 "minimum persistence interval");
87 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax,
88 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
89 &tcp_persmax, 0, sysctl_msec_to_ticks, "I",
90 "maximum persistence interval");
93 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,
94 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
95 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I",
96 "time to establish connection");
99 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,
100 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
101 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I",
102 "time before keepalive probes begin");
105 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,
106 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
107 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I",
108 "time between keepalive probes");
111 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
112 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
113 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
114 "Time before a delayed ACK is sent");
116 VNET_DEFINE(int, tcp_msl);
117 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl,
118 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_VNET,
119 &VNET_NAME(tcp_msl), 0, sysctl_msec_to_ticks, "I",
120 "Maximum segment lifetime");
122 int tcp_rexmit_initial;
123 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial,
124 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
125 &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
126 "Initial Retransmission Timeout");
129 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min,
130 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
131 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
132 "Minimum Retransmission Timeout");
135 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop,
136 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
137 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
138 "Retransmission Timer Slop");
140 VNET_DEFINE(int, tcp_always_keepalive) = 1;
141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW,
142 &VNET_NAME(tcp_always_keepalive) , 0,
143 "Assume SO_KEEPALIVE on all TCP connections");
145 int tcp_fast_finwait2_recycle = 0;
146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
147 &tcp_fast_finwait2_recycle, 0,
148 "Recycle closed FIN_WAIT_2 connections faster");
150 int tcp_finwait2_timeout;
151 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout,
152 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
153 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I",
154 "FIN-WAIT2 timeout");
156 int tcp_keepcnt = TCPTV_KEEPCNT;
157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
158 "Number of keepalive probes to send");
160 /* max idle probes */
161 int tcp_maxpersistidle;
163 int tcp_rexmit_drop_options = 0;
164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
165 &tcp_rexmit_drop_options, 0,
166 "Drop TCP options from 3rd and later retransmitted SYN");
168 int tcp_maxunacktime = TCPTV_MAXUNACKTIME;
169 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxunacktime,
170 CTLTYPE_INT|CTLFLAG_RW | CTLFLAG_NEEDGIANT,
171 &tcp_maxunacktime, 0, sysctl_msec_to_ticks, "I",
172 "Maximum time (in ms) that a session can linger without making progress");
174 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
176 CTLFLAG_RW|CTLFLAG_VNET,
177 &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
178 "Path MTU Discovery Black Hole Detection Enabled");
181 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
183 CTLFLAG_RW|CTLFLAG_VNET,
184 &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
185 "Path MTU Discovery Black Hole Detection lowered MSS");
189 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
191 CTLFLAG_RW|CTLFLAG_VNET,
192 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
193 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
197 static int per_cpu_timers = 1;
199 static int per_cpu_timers = 0;
201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
202 &per_cpu_timers , 0, "run tcp timers on all cpus");
205 sysctl_net_inet_tcp_retries(SYSCTL_HANDLER_ARGS)
210 error = sysctl_handle_int(oidp, &new, 0, req);
211 if (error == 0 && req->newptr) {
212 if ((new < 1) || (new > TCP_MAXRXTSHIFT))
220 VNET_DEFINE(int, tcp_retries) = TCP_MAXRXTSHIFT;
221 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, retries,
222 CTLTYPE_INT | CTLFLAG_VNET | CTLFLAG_RW,
223 &VNET_NAME(tcp_retries), 0, sysctl_net_inet_tcp_retries, "I",
224 "maximum number of consecutive timer based retransmissions");
227 * Map the given inp to a CPU id.
229 * This queries RSS if it's compiled in, else it defaults to the current
233 inp_to_cpuid(struct inpcb *inp)
237 if (per_cpu_timers) {
239 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
240 if (cpuid == NETISR_CPUID_NONE)
241 return (curcpu); /* XXX */
246 * We don't have a flowid -> cpuid mapping, so cheat and
247 * just map unknown cpuids to curcpu. Not the best, but
248 * apparently better than defaulting to swi 0.
250 cpuid = inp->inp_flowid % (mp_maxid + 1);
251 if (! CPU_ABSENT(cpuid))
259 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
260 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
262 int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
265 * TCP timer processing.
267 * Each connection has 5 timers associated with it, which can be scheduled
268 * simultaneously. They all are serviced by one callout tcp_timer_enter().
269 * This function executes the next timer via tcp_timersw[] vector. Each
270 * timer is supposed to return 'true' unless the connection was destroyed.
271 * In the former case tcp_timer_enter() will schedule callout for next timer.
274 typedef bool tcp_timer_t(struct tcpcb *);
275 static tcp_timer_t tcp_timer_delack;
276 static tcp_timer_t tcp_timer_2msl;
277 static tcp_timer_t tcp_timer_keep;
278 static tcp_timer_t tcp_timer_persist;
279 static tcp_timer_t tcp_timer_rexmt;
281 static tcp_timer_t * const tcp_timersw[TT_N] = {
282 [TT_DELACK] = tcp_timer_delack,
283 [TT_REXMT] = tcp_timer_rexmt,
284 [TT_PERSIST] = tcp_timer_persist,
285 [TT_KEEP] = tcp_timer_keep,
286 [TT_2MSL] = tcp_timer_2msl,
290 * tcp_output_locked() s a timer specific variation of call to tcp_output(),
291 * see tcp_var.h for the rest. It handles drop request from advanced stacks,
292 * but keeps tcpcb locked unless tcp_drop() destroyed it.
293 * Returns true if tcpcb is valid and locked.
296 tcp_output_locked(struct tcpcb *tp)
300 INP_WLOCK_ASSERT(tptoinpcb(tp));
302 if ((rv = tp->t_fb->tfb_tcp_output(tp)) < 0) {
303 KASSERT(tp->t_fb->tfb_flags & TCP_FUNC_OUTPUT_CANDROP,
304 ("TCP stack %s requested tcp_drop(%p)",
305 tp->t_fb->tfb_tcp_block_name, tp));
306 tp = tcp_drop(tp, rv);
313 tcp_timer_delack(struct tcpcb *tp)
315 struct epoch_tracker et;
316 #if defined(INVARIANTS) || defined(VIMAGE)
317 struct inpcb *inp = tptoinpcb(tp);
321 INP_WLOCK_ASSERT(inp);
323 CURVNET_SET(inp->inp_vnet);
324 tp->t_flags |= TF_ACKNOW;
325 TCPSTAT_INC(tcps_delack);
327 rv = tcp_output_locked(tp);
335 tcp_timer_2msl(struct tcpcb *tp)
337 struct inpcb *inp = tptoinpcb(tp);
340 INP_WLOCK_ASSERT(inp);
342 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
343 CURVNET_SET(inp->inp_vnet);
344 tcp_log_end_status(tp, TCP_EI_STATUS_2MSL);
345 tcp_free_sackholes(tp);
347 * 2 MSL timeout in shutdown went off. If we're closed but
348 * still waiting for peer to close and connection has been idle
349 * too long delete connection control block. Otherwise, check
352 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
353 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
354 * Ignore fact that there were recent incoming segments.
356 * XXXGL: check if inp_socket shall always be !NULL here?
358 if (tp->t_state == TCPS_TIME_WAIT) {
360 } else if (tp->t_state == TCPS_FIN_WAIT_2 &&
361 tcp_fast_finwait2_recycle && inp->inp_socket &&
362 (inp->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
363 TCPSTAT_INC(tcps_finwait2_drops);
366 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp))
367 tcp_timer_activate(tp, TT_2MSL, TP_KEEPINTVL(tp));
372 struct epoch_tracker et;
384 tcp_timer_keep(struct tcpcb *tp)
386 struct epoch_tracker et;
387 struct inpcb *inp = tptoinpcb(tp);
388 struct tcptemp *t_template;
390 INP_WLOCK_ASSERT(inp);
392 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
393 CURVNET_SET(inp->inp_vnet);
395 * Because we don't regularly reset the keepalive callout in
396 * the ESTABLISHED state, it may be that we don't actually need
397 * to send a keepalive yet. If that occurs, schedule another
398 * call for the next time the keepalive timer might expire.
400 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
403 idletime = ticks - tp->t_rcvtime;
404 if (idletime < TP_KEEPIDLE(tp)) {
405 tcp_timer_activate(tp, TT_KEEP,
406 TP_KEEPIDLE(tp) - idletime);
413 * Keep-alive timer went off; send something
414 * or drop connection if idle for too long.
416 TCPSTAT_INC(tcps_keeptimeo);
417 if (tp->t_state < TCPS_ESTABLISHED)
419 if ((V_tcp_always_keepalive ||
420 inp->inp_socket->so_options & SO_KEEPALIVE) &&
421 tp->t_state <= TCPS_CLOSING) {
422 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
425 * Send a packet designed to force a response
426 * if the peer is up and reachable:
427 * either an ACK if the connection is still alive,
428 * or an RST if the peer has closed the connection
429 * due to timeout or reboot.
430 * Using sequence number tp->snd_una-1
431 * causes the transmitted zero-length segment
432 * to lie outside the receive window;
433 * by the protocol spec, this requires the
434 * correspondent TCP to respond.
436 TCPSTAT_INC(tcps_keepprobe);
437 t_template = tcpip_maketemplate(inp);
440 tcp_respond(tp, t_template->tt_ipgen,
441 &t_template->tt_t, (struct mbuf *)NULL,
442 tp->rcv_nxt, tp->snd_una - 1, 0);
444 free(t_template, M_TEMP);
446 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINTVL(tp));
448 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
454 TCPSTAT_INC(tcps_keepdrops);
456 tcp_log_end_status(tp, TCP_EI_STATUS_KEEP_MAX);
457 tp = tcp_drop(tp, ETIMEDOUT);
465 * Has this session exceeded the maximum time without seeing a substantive
466 * acknowledgement? If so, return true; otherwise false.
469 tcp_maxunacktime_check(struct tcpcb *tp)
472 /* Are we tracking this timer for this session? */
473 if (TP_MAXUNACKTIME(tp) == 0)
476 /* Do we have a current measurement. */
477 if (tp->t_acktime == 0)
480 /* Are we within the acceptable range? */
481 if (TSTMP_GT(TP_MAXUNACKTIME(tp) + tp->t_acktime, (u_int)ticks))
484 /* We exceeded the timer. */
485 TCPSTAT_INC(tcps_progdrops);
490 tcp_timer_persist(struct tcpcb *tp)
492 struct epoch_tracker et;
493 #if defined(INVARIANTS) || defined(VIMAGE)
494 struct inpcb *inp = tptoinpcb(tp);
498 INP_WLOCK_ASSERT(inp);
500 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
501 CURVNET_SET(inp->inp_vnet);
503 * Persistence timer into zero window.
504 * Force a byte to be output, if possible.
506 TCPSTAT_INC(tcps_persisttimeo);
508 * Hack: if the peer is dead/unreachable, we do not
509 * time out if the window is closed. After a full
510 * backoff, drop the connection if the idle time
511 * (no responses to probes) reaches the maximum
512 * backoff that we would use if retransmitting.
513 * Also, drop the connection if we haven't been making
516 progdrop = tcp_maxunacktime_check(tp);
517 if (progdrop || (tp->t_rxtshift >= V_tcp_retries &&
518 (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
519 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff))) {
521 TCPSTAT_INC(tcps_persistdrop);
522 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX);
526 * If the user has closed the socket then drop a persisting
527 * connection after a much reduced timeout.
529 if (tp->t_state > TCPS_CLOSE_WAIT &&
530 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
531 TCPSTAT_INC(tcps_persistdrop);
532 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX);
536 tp->t_flags |= TF_FORCEDATA;
538 if ((rv = tcp_output_locked(tp)))
539 tp->t_flags &= ~TF_FORCEDATA;
547 tp = tcp_drop(tp, ETIMEDOUT);
555 tcp_timer_rexmt(struct tcpcb *tp)
557 struct epoch_tracker et;
558 struct inpcb *inp = tptoinpcb(tp);
562 INP_WLOCK_ASSERT(inp);
564 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
565 CURVNET_SET(inp->inp_vnet);
566 tcp_free_sackholes(tp);
567 if (tp->t_fb->tfb_tcp_rexmit_tmr) {
568 /* The stack has a timer action too. */
569 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
572 * Retransmission timer went off. Message has not
573 * been acked within retransmit interval. Back off
574 * to a longer retransmit interval and retransmit one segment.
576 * If we've either exceeded the maximum number of retransmissions,
577 * or we've gone long enough without making progress, then drop
580 if (++tp->t_rxtshift > V_tcp_retries || tcp_maxunacktime_check(tp)) {
581 if (tp->t_rxtshift > V_tcp_retries)
582 TCPSTAT_INC(tcps_timeoutdrop);
583 tp->t_rxtshift = V_tcp_retries;
584 tcp_log_end_status(tp, TCP_EI_STATUS_RETRAN);
586 tp = tcp_drop(tp, ETIMEDOUT);
592 if (tp->t_state == TCPS_SYN_SENT) {
594 * If the SYN was retransmitted, indicate CWND to be
595 * limited to 1 segment in cc_conn_init().
598 } else if (tp->t_rxtshift == 1) {
600 * first retransmit; record ssthresh and cwnd so they can
601 * be recovered if this turns out to be a "bad" retransmit.
602 * A retransmit is considered "bad" if an ACK for this
603 * segment is received within RTT/2 interval; the assumption
604 * here is that the ACK was already in flight. See
605 * "On Estimating End-to-End Network Path Properties" by
606 * Allman and Paxson for more details.
608 tp->snd_cwnd_prev = tp->snd_cwnd;
609 tp->snd_ssthresh_prev = tp->snd_ssthresh;
610 tp->snd_recover_prev = tp->snd_recover;
611 if (IN_FASTRECOVERY(tp->t_flags))
612 tp->t_flags |= TF_WASFRECOVERY;
614 tp->t_flags &= ~TF_WASFRECOVERY;
615 if (IN_CONGRECOVERY(tp->t_flags))
616 tp->t_flags |= TF_WASCRECOVERY;
618 tp->t_flags &= ~TF_WASCRECOVERY;
619 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
620 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
621 /* In the event that we've negotiated timestamps
622 * badrxtwin will be set to the value that we set
623 * the retransmitted packet's to_tsval to by tcp_output
625 tp->t_flags |= TF_PREVVALID;
627 tp->t_flags &= ~TF_PREVVALID;
628 TCPSTAT_INC(tcps_rexmttimeo);
629 if ((tp->t_state == TCPS_SYN_SENT) ||
630 (tp->t_state == TCPS_SYN_RECEIVED))
631 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
633 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
634 TCPT_RANGESET(tp->t_rxtcur, rexmt,
635 tp->t_rttmin, TCPTV_REXMTMAX);
638 * We enter the path for PLMTUD if connection is established or, if
639 * connection is FIN_WAIT_1 status, reason for the last is that if
640 * amount of data we send is very small, we could send it in couple of
641 * packets and process straight to FIN. In that case we won't catch
645 isipv6 = (inp->inp_vflag & INP_IPV6) ? true : false;
649 if (((V_tcp_pmtud_blackhole_detect == 1) ||
650 (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
651 (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
652 ((tp->t_state == TCPS_ESTABLISHED) ||
653 (tp->t_state == TCPS_FIN_WAIT_1))) {
654 if (tp->t_rxtshift == 1) {
656 * We enter blackhole detection after the first
657 * unsuccessful timer based retransmission.
658 * Then we reduce up to two times the MSS, each
659 * candidate giving two tries of retransmissions.
660 * But we give a candidate only two tries, if it
661 * actually reduces the MSS.
663 tp->t_blackhole_enter = 2;
664 tp->t_blackhole_exit = tp->t_blackhole_enter;
667 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss)
668 tp->t_blackhole_exit += 2;
669 if (tp->t_maxseg > V_tcp_v6mssdflt &&
670 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt)
671 tp->t_blackhole_exit += 2;
675 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss)
676 tp->t_blackhole_exit += 2;
677 if (tp->t_maxseg > V_tcp_mssdflt &&
678 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt)
679 tp->t_blackhole_exit += 2;
683 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
684 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
685 (tp->t_rxtshift >= tp->t_blackhole_enter &&
686 tp->t_rxtshift < tp->t_blackhole_exit &&
687 (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) {
689 * Enter Path MTU Black-hole Detection mechanism:
690 * - Disable Path MTU Discovery (IP "DF" bit).
691 * - Reduce MTU to lower value than what we
692 * negotiated with peer.
694 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
695 /* Record that we may have found a black hole. */
696 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
697 /* Keep track of previous MSS. */
698 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
702 * Reduce the MSS to blackhole value or to the default
703 * in an attempt to retransmit.
707 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss &&
708 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) {
709 /* Use the sysctl tuneable blackhole MSS. */
710 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
711 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
713 /* Use the default MSS. */
714 tp->t_maxseg = V_tcp_v6mssdflt;
716 * Disable Path MTU Discovery when we switch to
719 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
720 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
723 #if defined(INET6) && defined(INET)
727 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss &&
728 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) {
729 /* Use the sysctl tuneable blackhole MSS. */
730 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
731 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
733 /* Use the default MSS. */
734 tp->t_maxseg = V_tcp_mssdflt;
736 * Disable Path MTU Discovery when we switch to
739 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
740 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
744 * Reset the slow-start flight size
745 * as it may depend on the new MSS.
747 if (CC_ALGO(tp)->conn_init != NULL)
748 CC_ALGO(tp)->conn_init(&tp->t_ccv);
751 * If further retransmissions are still unsuccessful
752 * with a lowered MTU, maybe this isn't a blackhole and
753 * we restore the previous MSS and blackhole detection
756 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
757 (tp->t_rxtshift >= tp->t_blackhole_exit)) {
758 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
759 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
760 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
761 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
763 * Reset the slow-start flight size as it
764 * may depend on the new MSS.
766 if (CC_ALGO(tp)->conn_init != NULL)
767 CC_ALGO(tp)->conn_init(&tp->t_ccv);
773 * Disable RFC1323 and SACK if we haven't got any response to
774 * our third SYN to work-around some broken terminal servers
775 * (most of which have hopefully been retired) that have bad VJ
776 * header compression code which trashes TCP segments containing
777 * unknown-to-them TCP options.
779 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
780 (tp->t_rxtshift == 3))
781 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
783 * If we backed off this far, notify the L3 protocol that we're having
784 * connection problems.
786 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
788 if ((inp->inp_vflag & INP_IPV6) != 0)
794 tp->snd_nxt = tp->snd_una;
795 tp->snd_recover = tp->snd_max;
797 * Force a segment to be sent.
799 tp->t_flags |= TF_ACKNOW;
801 * If timing a segment in this window, stop the timer.
805 cc_cong_signal(tp, NULL, CC_RTO);
807 rv = tcp_output_locked(tp);
815 tcp_bblog_timer(struct tcpcb *tp, tt_which which, tt_what what, uint32_t ticks)
817 struct tcp_log_buffer *lgb;
820 INP_WLOCK_ASSERT(tptoinpcb(tp));
821 if (tcp_bblogging_on(tp))
822 lgb = tcp_log_event(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0,
823 NULL, false, NULL, NULL, 0, NULL);
827 lgb->tlb_flex1 = (what << 8) | which;
828 if (what == TT_STARTING) {
829 /* Convert ticks to ms and store it in tlb_flex2. */
831 lgb->tlb_flex2 = ticks;
833 ms = (((uint64_t)ticks * 1000) + (hz - 1)) / hz;
835 lgb->tlb_flex2 = UINT32_MAX;
837 lgb->tlb_flex2 = (uint32_t)ms;
843 static inline tt_which
844 tcp_timer_next(struct tcpcb *tp, sbintime_t *precision)
847 sbintime_t after, before;
849 for (i = 0, rv = TT_N, after = before = SBT_MAX; i < TT_N; i++) {
850 if (tp->t_timers[i] < after) {
851 after = tp->t_timers[i];
854 before = MIN(before, tp->t_timers[i] + tp->t_precisions[i]);
856 if (precision != NULL)
857 *precision = before - after;
863 tcp_timer_enter(void *xtp)
865 struct tcpcb *tp = xtp;
866 struct inpcb *inp = tptoinpcb(tp);
867 sbintime_t precision;
871 INP_WLOCK_ASSERT(inp);
872 MPASS((curthread->td_pflags & TDP_INTCPCALLOUT) == 0);
874 curthread->td_pflags |= TDP_INTCPCALLOUT;
876 which = tcp_timer_next(tp, NULL);
878 tp->t_timers[which] = SBT_MAX;
879 tp->t_precisions[which] = 0;
881 tcp_bblog_timer(tp, which, TT_PROCESSING, 0);
882 tp_valid = tcp_timersw[which](tp);
884 tcp_bblog_timer(tp, which, TT_PROCESSED, 0);
885 if ((which = tcp_timer_next(tp, &precision)) != TT_N) {
886 callout_reset_sbt_on(&tp->t_callout,
887 tp->t_timers[which], precision, tcp_timer_enter,
888 tp, inp_to_cpuid(inp), C_ABSOLUTE);
893 curthread->td_pflags &= ~TDP_INTCPCALLOUT;
897 * Activate or stop (delta == 0) a TCP timer.
900 tcp_timer_activate(struct tcpcb *tp, tt_which which, u_int delta)
902 struct inpcb *inp = tptoinpcb(tp);
903 sbintime_t precision;
907 if (tp->t_flags & TF_TOE)
911 INP_WLOCK_ASSERT(inp);
915 callout_when(tick_sbt * delta, 0, C_HARDCLOCK,
916 &tp->t_timers[which], &tp->t_precisions[which]);
919 tp->t_timers[which] = SBT_MAX;
921 tcp_bblog_timer(tp, which, what, delta);
923 if ((which = tcp_timer_next(tp, &precision)) != TT_N)
924 callout_reset_sbt_on(&tp->t_callout, tp->t_timers[which],
925 precision, tcp_timer_enter, tp, inp_to_cpuid(inp),
928 callout_stop(&tp->t_callout);
932 tcp_timer_active(struct tcpcb *tp, tt_which which)
935 INP_WLOCK_ASSERT(tptoinpcb(tp));
937 return (tp->t_timers[which] != SBT_MAX);
941 * Stop all timers associated with tcpcb.
943 * Called only on tcpcb destruction. The tcpcb shall already be dropped from
944 * the pcb lookup database and socket is not losing the last reference.
946 * XXXGL: unfortunately our callout(9) is not able to fully stop a locked
947 * callout even when only two threads are involved: the callout itself and the
948 * thread that does callout_stop(). See where softclock_call_cc() swaps the
949 * callwheel lock to callout lock and then checks cc_exec_cancel(). This is
950 * the race window. If it happens, the tcp_timer_enter() won't be executed,
951 * however pcb lock will be locked and released, hence we can't free memory.
952 * Until callout(9) is improved, just keep retrying. In my profiling I've seen
953 * such event happening less than 1 time per hour with 20-30 Gbit/s of traffic.
956 tcp_timer_stop(struct tcpcb *tp)
958 struct inpcb *inp = tptoinpcb(tp);
960 INP_WLOCK_ASSERT(inp);
962 if (curthread->td_pflags & TDP_INTCPCALLOUT) {
963 int stopped __diagused;
965 stopped = callout_stop(&tp->t_callout);
967 } else while(__predict_false(callout_stop(&tp->t_callout) == 0)) {
969 kern_yield(PRI_UNCHANGED);