2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
36 #include "opt_inet6.h"
37 #include "opt_tcpdebug.h"
40 #include <sys/param.h>
41 #include <sys/kernel.h>
44 #include <sys/mutex.h>
45 #include <sys/protosw.h>
47 #include <sys/socket.h>
48 #include <sys/socketvar.h>
49 #include <sys/sysctl.h>
50 #include <sys/systm.h>
53 #include <net/route.h>
54 #include <net/rss_config.h>
56 #include <net/netisr.h>
58 #include <netinet/in.h>
59 #include <netinet/in_kdtrace.h>
60 #include <netinet/in_pcb.h>
61 #include <netinet/in_rss.h>
62 #include <netinet/in_systm.h>
64 #include <netinet6/in6_pcb.h>
66 #include <netinet/ip_var.h>
67 #include <netinet/tcp.h>
68 #include <netinet/tcp_fsm.h>
69 #include <netinet/tcp_timer.h>
70 #include <netinet/tcp_var.h>
71 #include <netinet/cc/cc.h>
73 #include <netinet6/tcp6_var.h>
75 #include <netinet/tcpip.h>
77 #include <netinet/tcp_debug.h>
81 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
82 &tcp_persmin, 0, sysctl_msec_to_ticks, "I", "minimum persistence interval");
85 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
86 &tcp_persmax, 0, sysctl_msec_to_ticks, "I", "maximum persistence interval");
89 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
90 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
93 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
94 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
97 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
98 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
101 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
102 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
103 "Time before a delayed ACK is sent");
106 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
107 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
110 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
111 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
112 "Minimum Retransmission Timeout");
115 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
116 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
117 "Retransmission Timer Slop");
119 static int always_keepalive = 1;
120 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
121 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
123 int tcp_fast_finwait2_recycle = 0;
124 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
125 &tcp_fast_finwait2_recycle, 0,
126 "Recycle closed FIN_WAIT_2 connections faster");
128 int tcp_finwait2_timeout;
129 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
130 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
132 int tcp_keepcnt = TCPTV_KEEPCNT;
133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
134 "Number of keepalive probes to send");
136 /* max idle probes */
137 int tcp_maxpersistidle;
139 static int tcp_rexmit_drop_options = 0;
140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
141 &tcp_rexmit_drop_options, 0,
142 "Drop TCP options from 3rd and later retransmitted SYN");
144 static VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
145 #define V_tcp_pmtud_blackhole_detect VNET(tcp_pmtud_blackhole_detect)
146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
147 CTLFLAG_RW|CTLFLAG_VNET,
148 &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
149 "Path MTU Discovery Black Hole Detection Enabled");
151 static VNET_DEFINE(int, tcp_pmtud_blackhole_activated);
152 #define V_tcp_pmtud_blackhole_activated \
153 VNET(tcp_pmtud_blackhole_activated)
154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_activated,
155 CTLFLAG_RD|CTLFLAG_VNET,
156 &VNET_NAME(tcp_pmtud_blackhole_activated), 0,
157 "Path MTU Discovery Black Hole Detection, Activation Count");
159 static VNET_DEFINE(int, tcp_pmtud_blackhole_activated_min_mss);
160 #define V_tcp_pmtud_blackhole_activated_min_mss \
161 VNET(tcp_pmtud_blackhole_activated_min_mss)
162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_activated_min_mss,
163 CTLFLAG_RD|CTLFLAG_VNET,
164 &VNET_NAME(tcp_pmtud_blackhole_activated_min_mss), 0,
165 "Path MTU Discovery Black Hole Detection, Activation Count at min MSS");
167 static VNET_DEFINE(int, tcp_pmtud_blackhole_failed);
168 #define V_tcp_pmtud_blackhole_failed VNET(tcp_pmtud_blackhole_failed)
169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_failed,
170 CTLFLAG_RD|CTLFLAG_VNET,
171 &VNET_NAME(tcp_pmtud_blackhole_failed), 0,
172 "Path MTU Discovery Black Hole Detection, Failure Count");
175 static VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
176 #define V_tcp_pmtud_blackhole_mss VNET(tcp_pmtud_blackhole_mss)
177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
178 CTLFLAG_RW|CTLFLAG_VNET,
179 &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
180 "Path MTU Discovery Black Hole Detection lowered MSS");
184 static VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
185 #define V_tcp_v6pmtud_blackhole_mss VNET(tcp_v6pmtud_blackhole_mss)
186 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
187 CTLFLAG_RW|CTLFLAG_VNET,
188 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
189 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
193 static int per_cpu_timers = 1;
195 static int per_cpu_timers = 0;
197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
198 &per_cpu_timers , 0, "run tcp timers on all cpus");
201 #define INP_CPU(inp) (per_cpu_timers ? (!CPU_ABSENT(((inp)->inp_flowid % (mp_maxid+1))) ? \
202 ((inp)->inp_flowid % (mp_maxid+1)) : curcpu) : 0)
206 * Map the given inp to a CPU id.
208 * This queries RSS if it's compiled in, else it defaults to the current
212 inp_to_cpuid(struct inpcb *inp)
217 if (per_cpu_timers) {
218 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
219 if (cpuid == NETISR_CPUID_NONE)
220 return (curcpu); /* XXX */
225 /* Legacy, pre-RSS behaviour */
226 if (per_cpu_timers) {
228 * We don't have a flowid -> cpuid mapping, so cheat and
229 * just map unknown cpuids to curcpu. Not the best, but
230 * apparently better than defaulting to swi 0.
232 cpuid = inp->inp_flowid % (mp_maxid + 1);
233 if (! CPU_ABSENT(cpuid))
238 /* Default for RSS and non-RSS - cpuid 0 */
245 * Tcp protocol timeout routine called every 500 ms.
246 * Updates timestamps used for TCP
247 * causes finite state machine actions if timers expire.
252 VNET_ITERATOR_DECL(vnet_iter);
254 VNET_LIST_RLOCK_NOSLEEP();
255 VNET_FOREACH(vnet_iter) {
256 CURVNET_SET(vnet_iter);
257 (void) tcp_tw_2msl_scan(0);
260 VNET_LIST_RUNLOCK_NOSLEEP();
263 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
264 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
266 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
267 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
269 static int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
272 * TCP timer processing.
276 tcp_timer_delack(void *xtp)
278 struct tcpcb *tp = xtp;
280 CURVNET_SET(tp->t_vnet);
283 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
285 if (callout_pending(&tp->t_timers->tt_delack) ||
286 !callout_active(&tp->t_timers->tt_delack)) {
291 callout_deactivate(&tp->t_timers->tt_delack);
292 if ((inp->inp_flags & INP_DROPPED) != 0) {
297 tp->t_flags |= TF_ACKNOW;
298 TCPSTAT_INC(tcps_delack);
299 (void) tp->t_fb->tfb_tcp_output(tp);
305 * When a timer wants to remove a TCB it must
306 * hold the INP_INFO_RLOCK(). The timer function
307 * should only have grabbed the INP_WLOCK() when
308 * it entered. To safely switch to holding both the
309 * INP_INFO_RLOCK() and the INP_WLOCK() we must first
310 * grab a reference on the inp, which will hold the inp
311 * so that it can't be removed. We then unlock the INP_WLOCK(),
312 * and grab the INP_INFO_RLOCK() lock. Once we have the INP_INFO_RLOCK()
313 * we proceed again to get the INP_WLOCK() (this preserves proper
314 * lock order). After acquiring the INP_WLOCK we must check if someone
315 * else deleted the pcb i.e. the inp_flags check.
316 * If so we return 1 otherwise we return 0.
318 * No matter what the tcp_inpinfo_lock_add() function
319 * returns the caller must afterwards call tcp_inpinfo_lock_del()
320 * to drop the locks and reference properly.
324 tcp_inpinfo_lock_add(struct inpcb *inp)
328 INP_INFO_RLOCK(&V_tcbinfo);
330 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
338 tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
340 INP_INFO_RUNLOCK(&V_tcbinfo);
341 if (inp && (tp == NULL)) {
343 * If tcp_close/drop() gets called and tp
344 * returns NULL, then the function dropped
345 * the inp lock, we hold a reference keeping
346 * this around, so we must re-aquire the
347 * INP_WLOCK() in order to proceed with
348 * our dropping the inp reference.
352 if (inp && in_pcbrele_wlocked(inp) == 0)
357 tcp_timer_2msl(void *xtp)
359 struct tcpcb *tp = xtp;
361 CURVNET_SET(tp->t_vnet);
365 ostate = tp->t_state;
368 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
370 tcp_free_sackholes(tp);
371 if (callout_pending(&tp->t_timers->tt_2msl) ||
372 !callout_active(&tp->t_timers->tt_2msl)) {
373 INP_WUNLOCK(tp->t_inpcb);
377 callout_deactivate(&tp->t_timers->tt_2msl);
378 if ((inp->inp_flags & INP_DROPPED) != 0) {
383 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
384 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
386 * 2 MSL timeout in shutdown went off. If we're closed but
387 * still waiting for peer to close and connection has been idle
388 * too long delete connection control block. Otherwise, check
391 * If in TIME_WAIT state just ignore as this timeout is handled in
392 * tcp_tw_2msl_scan().
394 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
395 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
396 * Ignore fact that there were recent incoming segments.
398 if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
403 if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
404 tp->t_inpcb && tp->t_inpcb->inp_socket &&
405 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
406 TCPSTAT_INC(tcps_finwait2_drops);
407 if (tcp_inpinfo_lock_add(inp)) {
408 tcp_inpinfo_lock_del(inp, tp);
412 tcp_inpinfo_lock_del(inp, tp);
415 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
416 callout_reset(&tp->t_timers->tt_2msl,
417 TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
419 if (tcp_inpinfo_lock_add(inp)) {
420 tcp_inpinfo_lock_del(inp, tp);
424 tcp_inpinfo_lock_del(inp, tp);
430 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
431 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
434 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
443 tcp_timer_keep(void *xtp)
445 struct tcpcb *tp = xtp;
446 struct tcptemp *t_template;
448 CURVNET_SET(tp->t_vnet);
452 ostate = tp->t_state;
455 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
457 if (callout_pending(&tp->t_timers->tt_keep) ||
458 !callout_active(&tp->t_timers->tt_keep)) {
463 callout_deactivate(&tp->t_timers->tt_keep);
464 if ((inp->inp_flags & INP_DROPPED) != 0) {
469 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
470 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
473 * Because we don't regularly reset the keepalive callout in
474 * the ESTABLISHED state, it may be that we don't actually need
475 * to send a keepalive yet. If that occurs, schedule another
476 * call for the next time the keepalive timer might expire.
478 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
481 idletime = ticks - tp->t_rcvtime;
482 if (idletime < TP_KEEPIDLE(tp)) {
483 callout_reset(&tp->t_timers->tt_keep,
484 TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
492 * Keep-alive timer went off; send something
493 * or drop connection if idle for too long.
495 TCPSTAT_INC(tcps_keeptimeo);
496 if (tp->t_state < TCPS_ESTABLISHED)
498 if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) &&
499 tp->t_state <= TCPS_CLOSING) {
500 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
503 * Send a packet designed to force a response
504 * if the peer is up and reachable:
505 * either an ACK if the connection is still alive,
506 * or an RST if the peer has closed the connection
507 * due to timeout or reboot.
508 * Using sequence number tp->snd_una-1
509 * causes the transmitted zero-length segment
510 * to lie outside the receive window;
511 * by the protocol spec, this requires the
512 * correspondent TCP to respond.
514 TCPSTAT_INC(tcps_keepprobe);
515 t_template = tcpip_maketemplate(inp);
517 tcp_respond(tp, t_template->tt_ipgen,
518 &t_template->tt_t, (struct mbuf *)NULL,
519 tp->rcv_nxt, tp->snd_una - 1, 0);
520 free(t_template, M_TEMP);
522 callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
525 callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
529 if (inp->inp_socket->so_options & SO_DEBUG)
530 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
533 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
539 TCPSTAT_INC(tcps_keepdrops);
541 if (tcp_inpinfo_lock_add(inp)) {
542 tcp_inpinfo_lock_del(inp, tp);
545 tp = tcp_drop(tp, ETIMEDOUT);
548 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
549 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
552 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
553 tcp_inpinfo_lock_del(inp, tp);
559 tcp_timer_persist(void *xtp)
561 struct tcpcb *tp = xtp;
563 CURVNET_SET(tp->t_vnet);
567 ostate = tp->t_state;
570 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
572 if (callout_pending(&tp->t_timers->tt_persist) ||
573 !callout_active(&tp->t_timers->tt_persist)) {
578 callout_deactivate(&tp->t_timers->tt_persist);
579 if ((inp->inp_flags & INP_DROPPED) != 0) {
584 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
585 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
587 * Persistence timer into zero window.
588 * Force a byte to be output, if possible.
590 TCPSTAT_INC(tcps_persisttimeo);
592 * Hack: if the peer is dead/unreachable, we do not
593 * time out if the window is closed. After a full
594 * backoff, drop the connection if the idle time
595 * (no responses to probes) reaches the maximum
596 * backoff that we would use if retransmitting.
598 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
599 (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
600 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
601 TCPSTAT_INC(tcps_persistdrop);
602 if (tcp_inpinfo_lock_add(inp)) {
603 tcp_inpinfo_lock_del(inp, tp);
606 tp = tcp_drop(tp, ETIMEDOUT);
607 tcp_inpinfo_lock_del(inp, tp);
611 * If the user has closed the socket then drop a persisting
612 * connection after a much reduced timeout.
614 if (tp->t_state > TCPS_CLOSE_WAIT &&
615 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
616 TCPSTAT_INC(tcps_persistdrop);
617 if (tcp_inpinfo_lock_add(inp)) {
618 tcp_inpinfo_lock_del(inp, tp);
621 tp = tcp_drop(tp, ETIMEDOUT);
622 tcp_inpinfo_lock_del(inp, tp);
626 tp->t_flags |= TF_FORCEDATA;
627 (void) tp->t_fb->tfb_tcp_output(tp);
628 tp->t_flags &= ~TF_FORCEDATA;
631 if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
632 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
634 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
641 tcp_timer_rexmt(void * xtp)
643 struct tcpcb *tp = xtp;
644 CURVNET_SET(tp->t_vnet);
650 ostate = tp->t_state;
653 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
655 if (callout_pending(&tp->t_timers->tt_rexmt) ||
656 !callout_active(&tp->t_timers->tt_rexmt)) {
661 callout_deactivate(&tp->t_timers->tt_rexmt);
662 if ((inp->inp_flags & INP_DROPPED) != 0) {
667 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
668 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
669 tcp_free_sackholes(tp);
670 if (tp->t_fb->tfb_tcp_rexmit_tmr) {
671 /* The stack has a timer action too. */
672 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
675 * Retransmission timer went off. Message has not
676 * been acked within retransmit interval. Back off
677 * to a longer retransmit interval and retransmit one segment.
679 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
680 tp->t_rxtshift = TCP_MAXRXTSHIFT;
681 TCPSTAT_INC(tcps_timeoutdrop);
682 if (tcp_inpinfo_lock_add(inp)) {
683 tcp_inpinfo_lock_del(inp, tp);
686 tp = tcp_drop(tp, tp->t_softerror ?
687 tp->t_softerror : ETIMEDOUT);
688 tcp_inpinfo_lock_del(inp, tp);
691 if (tp->t_state == TCPS_SYN_SENT) {
693 * If the SYN was retransmitted, indicate CWND to be
694 * limited to 1 segment in cc_conn_init().
697 } else if (tp->t_rxtshift == 1) {
699 * first retransmit; record ssthresh and cwnd so they can
700 * be recovered if this turns out to be a "bad" retransmit.
701 * A retransmit is considered "bad" if an ACK for this
702 * segment is received within RTT/2 interval; the assumption
703 * here is that the ACK was already in flight. See
704 * "On Estimating End-to-End Network Path Properties" by
705 * Allman and Paxson for more details.
707 tp->snd_cwnd_prev = tp->snd_cwnd;
708 tp->snd_ssthresh_prev = tp->snd_ssthresh;
709 tp->snd_recover_prev = tp->snd_recover;
710 if (IN_FASTRECOVERY(tp->t_flags))
711 tp->t_flags |= TF_WASFRECOVERY;
713 tp->t_flags &= ~TF_WASFRECOVERY;
714 if (IN_CONGRECOVERY(tp->t_flags))
715 tp->t_flags |= TF_WASCRECOVERY;
717 tp->t_flags &= ~TF_WASCRECOVERY;
718 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
719 tp->t_flags |= TF_PREVVALID;
721 tp->t_flags &= ~TF_PREVVALID;
722 TCPSTAT_INC(tcps_rexmttimeo);
723 if ((tp->t_state == TCPS_SYN_SENT) ||
724 (tp->t_state == TCPS_SYN_RECEIVED))
725 rexmt = TCPTV_RTOBASE * tcp_syn_backoff[tp->t_rxtshift];
727 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
728 TCPT_RANGESET(tp->t_rxtcur, rexmt,
729 tp->t_rttmin, TCPTV_REXMTMAX);
732 * We enter the path for PLMTUD if connection is established or, if
733 * connection is FIN_WAIT_1 status, reason for the last is that if
734 * amount of data we send is very small, we could send it in couple of
735 * packets and process straight to FIN. In that case we won't catch
738 if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
739 || (tp->t_state == TCPS_FIN_WAIT_1))) {
745 * Idea here is that at each stage of mtu probe (usually, 1448
746 * -> 1188 -> 524) should be given 2 chances to recover before
747 * further clamping down. 'tp->t_rxtshift % 2 == 0' should
750 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
751 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
752 (tp->t_rxtshift >= 2 && tp->t_rxtshift % 2 == 0)) {
754 * Enter Path MTU Black-hole Detection mechanism:
755 * - Disable Path MTU Discovery (IP "DF" bit).
756 * - Reduce MTU to lower value than what we
757 * negotiated with peer.
759 /* Record that we may have found a black hole. */
760 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
762 /* Keep track of previous MSS. */
763 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
766 * Reduce the MSS to blackhole value or to the default
767 * in an attempt to retransmit.
770 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
772 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
773 /* Use the sysctl tuneable blackhole MSS. */
774 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
775 V_tcp_pmtud_blackhole_activated++;
777 /* Use the default MSS. */
778 tp->t_maxseg = V_tcp_v6mssdflt;
780 * Disable Path MTU Discovery when we switch to
783 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
784 V_tcp_pmtud_blackhole_activated_min_mss++;
787 #if defined(INET6) && defined(INET)
791 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) {
792 /* Use the sysctl tuneable blackhole MSS. */
793 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
794 V_tcp_pmtud_blackhole_activated++;
796 /* Use the default MSS. */
797 tp->t_maxseg = V_tcp_mssdflt;
799 * Disable Path MTU Discovery when we switch to
802 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
803 V_tcp_pmtud_blackhole_activated_min_mss++;
807 * Reset the slow-start flight size
808 * as it may depend on the new MSS.
810 if (CC_ALGO(tp)->conn_init != NULL)
811 CC_ALGO(tp)->conn_init(tp->ccv);
814 * If further retransmissions are still unsuccessful
815 * with a lowered MTU, maybe this isn't a blackhole and
816 * we restore the previous MSS and blackhole detection
818 * The limit '6' is determined by giving each probe
819 * stage (1448, 1188, 524) 2 chances to recover.
821 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
822 (tp->t_rxtshift > 6)) {
823 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
824 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
825 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
826 V_tcp_pmtud_blackhole_failed++;
828 * Reset the slow-start flight size as it
829 * may depend on the new MSS.
831 if (CC_ALGO(tp)->conn_init != NULL)
832 CC_ALGO(tp)->conn_init(tp->ccv);
838 * Disable RFC1323 and SACK if we haven't got any response to
839 * our third SYN to work-around some broken terminal servers
840 * (most of which have hopefully been retired) that have bad VJ
841 * header compression code which trashes TCP segments containing
842 * unknown-to-them TCP options.
844 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
845 (tp->t_rxtshift == 3))
846 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
848 * If we backed off this far, notify the L3 protocol that we're having
849 * connection problems.
851 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
853 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
854 in6_losing(tp->t_inpcb);
857 in_losing(tp->t_inpcb);
859 tp->snd_nxt = tp->snd_una;
860 tp->snd_recover = tp->snd_max;
862 * Force a segment to be sent.
864 tp->t_flags |= TF_ACKNOW;
866 * If timing a segment in this window, stop the timer.
870 cc_cong_signal(tp, NULL, CC_RTO);
872 (void) tp->t_fb->tfb_tcp_output(tp);
875 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
876 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
879 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
886 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
888 struct callout *t_callout;
889 timeout_t *f_callout;
890 struct inpcb *inp = tp->t_inpcb;
891 int cpu = inp_to_cpuid(inp);
894 if (tp->t_flags & TF_TOE)
898 if (tp->t_timers->tt_flags & TT_STOPPED)
901 switch (timer_type) {
903 t_callout = &tp->t_timers->tt_delack;
904 f_callout = tcp_timer_delack;
907 t_callout = &tp->t_timers->tt_rexmt;
908 f_callout = tcp_timer_rexmt;
911 t_callout = &tp->t_timers->tt_persist;
912 f_callout = tcp_timer_persist;
915 t_callout = &tp->t_timers->tt_keep;
916 f_callout = tcp_timer_keep;
919 t_callout = &tp->t_timers->tt_2msl;
920 f_callout = tcp_timer_2msl;
923 if (tp->t_fb->tfb_tcp_timer_activate) {
924 tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
927 panic("tp %p bad timer_type %#x", tp, timer_type);
930 callout_stop(t_callout);
932 callout_reset_on(t_callout, delta, f_callout, tp, cpu);
937 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
939 struct callout *t_callout;
941 switch (timer_type) {
943 t_callout = &tp->t_timers->tt_delack;
946 t_callout = &tp->t_timers->tt_rexmt;
949 t_callout = &tp->t_timers->tt_persist;
952 t_callout = &tp->t_timers->tt_keep;
955 t_callout = &tp->t_timers->tt_2msl;
958 if (tp->t_fb->tfb_tcp_timer_active) {
959 return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
961 panic("tp %p bad timer_type %#x", tp, timer_type);
963 return callout_active(t_callout);
967 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
969 struct callout *t_callout;
971 tp->t_timers->tt_flags |= TT_STOPPED;
972 switch (timer_type) {
974 t_callout = &tp->t_timers->tt_delack;
977 t_callout = &tp->t_timers->tt_rexmt;
980 t_callout = &tp->t_timers->tt_persist;
983 t_callout = &tp->t_timers->tt_keep;
986 t_callout = &tp->t_timers->tt_2msl;
989 if (tp->t_fb->tfb_tcp_timer_stop) {
991 * XXXrrs we need to look at this with the
992 * stop case below (flags).
994 tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
997 panic("tp %p bad timer_type %#x", tp, timer_type);
1000 if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
1002 * Can't stop the callout, defer tcpcb actual deletion
1003 * to the last one. We do this using the async drain
1004 * function and incrementing the count in
1006 tp->t_timers->tt_draincnt++;