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 * 4. 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"
39 #include <sys/param.h>
40 #include <sys/kernel.h>
43 #include <sys/mutex.h>
44 #include <sys/protosw.h>
46 #include <sys/socket.h>
47 #include <sys/socketvar.h>
48 #include <sys/sysctl.h>
49 #include <sys/systm.h>
52 #include <net/route.h>
55 #include <netinet/cc.h>
56 #include <netinet/in.h>
57 #include <netinet/in_pcb.h>
58 #include <netinet/in_systm.h>
60 #include <netinet6/in6_pcb.h>
62 #include <netinet/ip_var.h>
63 #include <netinet/tcp_fsm.h>
64 #include <netinet/tcp_timer.h>
65 #include <netinet/tcp_var.h>
67 #include <netinet6/tcp6_var.h>
69 #include <netinet/tcpip.h>
71 #include <netinet/tcp_debug.h>
75 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
76 &tcp_persmin, 0, sysctl_msec_to_ticks, "I", "minimum persistence interval");
79 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
80 &tcp_persmax, 0, sysctl_msec_to_ticks, "I", "maximum persistence interval");
83 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
84 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
87 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
88 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
91 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
92 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
95 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
96 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
97 "Time before a delayed ACK is sent");
100 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
101 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
104 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
105 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
106 "Minimum Retransmission Timeout");
109 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
110 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
111 "Retransmission Timer Slop");
113 static int always_keepalive = 1;
114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
115 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
117 int tcp_fast_finwait2_recycle = 0;
118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
119 &tcp_fast_finwait2_recycle, 0,
120 "Recycle closed FIN_WAIT_2 connections faster");
122 int tcp_finwait2_timeout;
123 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
124 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
126 int tcp_keepcnt = TCPTV_KEEPCNT;
127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
128 "Number of keepalive probes to send");
130 /* max idle probes */
131 int tcp_maxpersistidle;
133 static int tcp_rexmit_drop_options = 0;
134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
135 &tcp_rexmit_drop_options, 0,
136 "Drop TCP options from 3rd and later retransmitted SYN");
138 static VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
139 #define V_tcp_pmtud_blackhole_detect VNET(tcp_pmtud_blackhole_detect)
140 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
142 &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
143 "Path MTU Discovery Black Hole Detection Enabled");
145 static VNET_DEFINE(int, tcp_pmtud_blackhole_activated);
146 #define V_tcp_pmtud_blackhole_activated \
147 VNET(tcp_pmtud_blackhole_activated)
148 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_activated,
150 &VNET_NAME(tcp_pmtud_blackhole_activated), 0,
151 "Path MTU Discovery Black Hole Detection, Activation Count");
153 static VNET_DEFINE(int, tcp_pmtud_blackhole_activated_min_mss);
154 #define V_tcp_pmtud_blackhole_activated_min_mss \
155 VNET(tcp_pmtud_blackhole_activated_min_mss)
156 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_activated_min_mss,
158 &VNET_NAME(tcp_pmtud_blackhole_activated_min_mss), 0,
159 "Path MTU Discovery Black Hole Detection, Activation Count at min MSS");
161 static VNET_DEFINE(int, tcp_pmtud_blackhole_failed);
162 #define V_tcp_pmtud_blackhole_failed VNET(tcp_pmtud_blackhole_failed)
163 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_failed,
165 &VNET_NAME(tcp_pmtud_blackhole_failed), 0,
166 "Path MTU Discovery Black Hole Detection, Failure Count");
169 static VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
170 #define V_tcp_pmtud_blackhole_mss VNET(tcp_pmtud_blackhole_mss)
171 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
173 &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
174 "Path MTU Discovery Black Hole Detection lowered MSS");
178 static VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
179 #define V_tcp_v6pmtud_blackhole_mss VNET(tcp_v6pmtud_blackhole_mss)
180 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
182 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
183 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
186 static int per_cpu_timers = 0;
187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
188 &per_cpu_timers , 0, "run tcp timers on all cpus");
190 #define INP_CPU(inp) (per_cpu_timers ? (!CPU_ABSENT(((inp)->inp_flowid % (mp_maxid+1))) ? \
191 ((inp)->inp_flowid % (mp_maxid+1)) : curcpu) : 0)
194 * Tcp protocol timeout routine called every 500 ms.
195 * Updates timestamps used for TCP
196 * causes finite state machine actions if timers expire.
201 VNET_ITERATOR_DECL(vnet_iter);
203 VNET_LIST_RLOCK_NOSLEEP();
204 VNET_FOREACH(vnet_iter) {
205 CURVNET_SET(vnet_iter);
206 (void) tcp_tw_2msl_scan(0);
209 VNET_LIST_RUNLOCK_NOSLEEP();
212 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
213 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
215 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
216 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
218 static int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
221 * TCP timer processing.
225 tcp_timer_delack(void *xtp)
227 struct tcpcb *tp = xtp;
229 CURVNET_SET(tp->t_vnet);
232 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
234 if (callout_pending(&tp->t_timers->tt_delack) ||
235 !callout_active(&tp->t_timers->tt_delack)) {
240 callout_deactivate(&tp->t_timers->tt_delack);
241 if ((inp->inp_flags & INP_DROPPED) != 0) {
246 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
247 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
248 KASSERT((tp->t_timers->tt_flags & TT_DELACK) != 0,
249 ("%s: tp %p delack callout should be running", __func__, tp));
251 tp->t_flags |= TF_ACKNOW;
252 TCPSTAT_INC(tcps_delack);
253 (void) tcp_output(tp);
259 tcp_timer_2msl(void *xtp)
261 struct tcpcb *tp = xtp;
263 CURVNET_SET(tp->t_vnet);
267 ostate = tp->t_state;
269 INP_INFO_WLOCK(&V_tcbinfo);
271 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
273 tcp_free_sackholes(tp);
274 if (callout_pending(&tp->t_timers->tt_2msl) ||
275 !callout_active(&tp->t_timers->tt_2msl)) {
276 INP_WUNLOCK(tp->t_inpcb);
277 INP_INFO_WUNLOCK(&V_tcbinfo);
281 callout_deactivate(&tp->t_timers->tt_2msl);
282 if ((inp->inp_flags & INP_DROPPED) != 0) {
284 INP_INFO_WUNLOCK(&V_tcbinfo);
288 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
289 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
290 KASSERT((tp->t_timers->tt_flags & TT_2MSL) != 0,
291 ("%s: tp %p 2msl callout should be running", __func__, tp));
293 * 2 MSL timeout in shutdown went off. If we're closed but
294 * still waiting for peer to close and connection has been idle
295 * too long delete connection control block. Otherwise, check
298 * If in TIME_WAIT state just ignore as this timeout is handled in
299 * tcp_tw_2msl_scan().
301 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
302 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
303 * Ignore fact that there were recent incoming segments.
305 if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
307 INP_INFO_WUNLOCK(&V_tcbinfo);
311 if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
312 tp->t_inpcb && tp->t_inpcb->inp_socket &&
313 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
314 TCPSTAT_INC(tcps_finwait2_drops);
317 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
318 if (!callout_reset(&tp->t_timers->tt_2msl,
319 TP_KEEPINTVL(tp), tcp_timer_2msl, tp)) {
320 tp->t_timers->tt_flags &= ~TT_2MSL_RST;
327 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
328 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
333 INP_INFO_WUNLOCK(&V_tcbinfo);
338 tcp_timer_keep(void *xtp)
340 struct tcpcb *tp = xtp;
341 struct tcptemp *t_template;
343 CURVNET_SET(tp->t_vnet);
347 ostate = tp->t_state;
349 INP_INFO_WLOCK(&V_tcbinfo);
351 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
353 if (callout_pending(&tp->t_timers->tt_keep) ||
354 !callout_active(&tp->t_timers->tt_keep)) {
356 INP_INFO_WUNLOCK(&V_tcbinfo);
360 callout_deactivate(&tp->t_timers->tt_keep);
361 if ((inp->inp_flags & INP_DROPPED) != 0) {
363 INP_INFO_WUNLOCK(&V_tcbinfo);
367 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
368 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
369 KASSERT((tp->t_timers->tt_flags & TT_KEEP) != 0,
370 ("%s: tp %p keep callout should be running", __func__, tp));
372 * Keep-alive timer went off; send something
373 * or drop connection if idle for too long.
375 TCPSTAT_INC(tcps_keeptimeo);
376 if (tp->t_state < TCPS_ESTABLISHED)
378 if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) &&
379 tp->t_state <= TCPS_CLOSING) {
380 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
383 * Send a packet designed to force a response
384 * if the peer is up and reachable:
385 * either an ACK if the connection is still alive,
386 * or an RST if the peer has closed the connection
387 * due to timeout or reboot.
388 * Using sequence number tp->snd_una-1
389 * causes the transmitted zero-length segment
390 * to lie outside the receive window;
391 * by the protocol spec, this requires the
392 * correspondent TCP to respond.
394 TCPSTAT_INC(tcps_keepprobe);
395 t_template = tcpip_maketemplate(inp);
397 tcp_respond(tp, t_template->tt_ipgen,
398 &t_template->tt_t, (struct mbuf *)NULL,
399 tp->rcv_nxt, tp->snd_una - 1, 0);
400 free(t_template, M_TEMP);
402 if (!callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
403 tcp_timer_keep, tp)) {
404 tp->t_timers->tt_flags &= ~TT_KEEP_RST;
406 } else if (!callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
407 tcp_timer_keep, tp)) {
408 tp->t_timers->tt_flags &= ~TT_KEEP_RST;
412 if (inp->inp_socket->so_options & SO_DEBUG)
413 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
417 INP_INFO_WUNLOCK(&V_tcbinfo);
422 TCPSTAT_INC(tcps_keepdrops);
423 tp = tcp_drop(tp, ETIMEDOUT);
426 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
427 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
431 INP_WUNLOCK(tp->t_inpcb);
432 INP_INFO_WUNLOCK(&V_tcbinfo);
437 tcp_timer_persist(void *xtp)
439 struct tcpcb *tp = xtp;
441 CURVNET_SET(tp->t_vnet);
445 ostate = tp->t_state;
447 INP_INFO_WLOCK(&V_tcbinfo);
449 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
451 if (callout_pending(&tp->t_timers->tt_persist) ||
452 !callout_active(&tp->t_timers->tt_persist)) {
454 INP_INFO_WUNLOCK(&V_tcbinfo);
458 callout_deactivate(&tp->t_timers->tt_persist);
459 if ((inp->inp_flags & INP_DROPPED) != 0) {
461 INP_INFO_WUNLOCK(&V_tcbinfo);
465 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
466 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
467 KASSERT((tp->t_timers->tt_flags & TT_PERSIST) != 0,
468 ("%s: tp %p persist callout should be running", __func__, tp));
470 * Persistance timer into zero window.
471 * Force a byte to be output, if possible.
473 TCPSTAT_INC(tcps_persisttimeo);
475 * Hack: if the peer is dead/unreachable, we do not
476 * time out if the window is closed. After a full
477 * backoff, drop the connection if the idle time
478 * (no responses to probes) reaches the maximum
479 * backoff that we would use if retransmitting.
481 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
482 (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
483 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
484 TCPSTAT_INC(tcps_persistdrop);
485 tp = tcp_drop(tp, ETIMEDOUT);
489 * If the user has closed the socket then drop a persisting
490 * connection after a much reduced timeout.
492 if (tp->t_state > TCPS_CLOSE_WAIT &&
493 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
494 TCPSTAT_INC(tcps_persistdrop);
495 tp = tcp_drop(tp, ETIMEDOUT);
499 tp->t_flags |= TF_FORCEDATA;
500 (void) tcp_output(tp);
501 tp->t_flags &= ~TF_FORCEDATA;
505 if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
506 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
510 INP_INFO_WUNLOCK(&V_tcbinfo);
515 tcp_timer_rexmt(void * xtp)
517 struct tcpcb *tp = xtp;
518 CURVNET_SET(tp->t_vnet);
525 ostate = tp->t_state;
528 INP_INFO_RLOCK(&V_tcbinfo);
530 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
532 if (callout_pending(&tp->t_timers->tt_rexmt) ||
533 !callout_active(&tp->t_timers->tt_rexmt)) {
535 INP_INFO_RUNLOCK(&V_tcbinfo);
539 callout_deactivate(&tp->t_timers->tt_rexmt);
540 if ((inp->inp_flags & INP_DROPPED) != 0) {
542 INP_INFO_RUNLOCK(&V_tcbinfo);
546 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
547 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
548 KASSERT((tp->t_timers->tt_flags & TT_REXMT) != 0,
549 ("%s: tp %p rexmt callout should be running", __func__, tp));
550 tcp_free_sackholes(tp);
552 * Retransmission timer went off. Message has not
553 * been acked within retransmit interval. Back off
554 * to a longer retransmit interval and retransmit one segment.
556 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
557 tp->t_rxtshift = TCP_MAXRXTSHIFT;
558 TCPSTAT_INC(tcps_timeoutdrop);
560 INP_INFO_RUNLOCK(&V_tcbinfo);
562 INP_INFO_WLOCK(&V_tcbinfo);
564 if (in_pcbrele_wlocked(inp)) {
565 INP_INFO_WUNLOCK(&V_tcbinfo);
569 if (inp->inp_flags & INP_DROPPED) {
571 INP_INFO_WUNLOCK(&V_tcbinfo);
576 tp = tcp_drop(tp, tp->t_softerror ?
577 tp->t_softerror : ETIMEDOUT);
581 INP_INFO_RUNLOCK(&V_tcbinfo);
583 if (tp->t_state == TCPS_SYN_SENT) {
585 * If the SYN was retransmitted, indicate CWND to be
586 * limited to 1 segment in cc_conn_init().
589 } else if (tp->t_rxtshift == 1) {
591 * first retransmit; record ssthresh and cwnd so they can
592 * be recovered if this turns out to be a "bad" retransmit.
593 * A retransmit is considered "bad" if an ACK for this
594 * segment is received within RTT/2 interval; the assumption
595 * here is that the ACK was already in flight. See
596 * "On Estimating End-to-End Network Path Properties" by
597 * Allman and Paxson for more details.
599 tp->snd_cwnd_prev = tp->snd_cwnd;
600 tp->snd_ssthresh_prev = tp->snd_ssthresh;
601 tp->snd_recover_prev = tp->snd_recover;
602 if (IN_FASTRECOVERY(tp->t_flags))
603 tp->t_flags |= TF_WASFRECOVERY;
605 tp->t_flags &= ~TF_WASFRECOVERY;
606 if (IN_CONGRECOVERY(tp->t_flags))
607 tp->t_flags |= TF_WASCRECOVERY;
609 tp->t_flags &= ~TF_WASCRECOVERY;
610 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
611 tp->t_flags |= TF_PREVVALID;
613 tp->t_flags &= ~TF_PREVVALID;
614 TCPSTAT_INC(tcps_rexmttimeo);
615 if ((tp->t_state == TCPS_SYN_SENT) ||
616 (tp->t_state == TCPS_SYN_RECEIVED))
617 rexmt = TCPTV_RTOBASE * tcp_syn_backoff[tp->t_rxtshift];
619 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
620 TCPT_RANGESET(tp->t_rxtcur, rexmt,
621 tp->t_rttmin, TCPTV_REXMTMAX);
624 * We enter the path for PLMTUD if connection is established or, if
625 * connection is FIN_WAIT_1 status, reason for the last is that if
626 * amount of data we send is very small, we could send it in couple of
627 * packets and process straight to FIN. In that case we won't catch
630 if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
631 || (tp->t_state == TCPS_FIN_WAIT_1))) {
638 * Idea here is that at each stage of mtu probe (usually, 1448
639 * -> 1188 -> 524) should be given 2 chances to recover before
640 * further clamping down. 'tp->t_rxtshift % 2 == 0' should
643 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
644 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
645 (tp->t_rxtshift >= 2 && tp->t_rxtshift % 2 == 0)) {
647 * Enter Path MTU Black-hole Detection mechanism:
648 * - Disable Path MTU Discovery (IP "DF" bit).
649 * - Reduce MTU to lower value than what we
650 * negotiated with peer.
652 /* Record that we may have found a black hole. */
653 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
655 /* Keep track of previous MSS. */
656 optlen = tp->t_maxopd - tp->t_maxseg;
657 tp->t_pmtud_saved_maxopd = tp->t_maxopd;
660 * Reduce the MSS to blackhole value or to the default
661 * in an attempt to retransmit.
664 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
666 tp->t_maxopd > V_tcp_v6pmtud_blackhole_mss) {
667 /* Use the sysctl tuneable blackhole MSS. */
668 tp->t_maxopd = V_tcp_v6pmtud_blackhole_mss;
669 V_tcp_pmtud_blackhole_activated++;
671 /* Use the default MSS. */
672 tp->t_maxopd = V_tcp_v6mssdflt;
674 * Disable Path MTU Discovery when we switch to
677 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
678 V_tcp_pmtud_blackhole_activated_min_mss++;
681 #if defined(INET6) && defined(INET)
685 if (tp->t_maxopd > V_tcp_pmtud_blackhole_mss) {
686 /* Use the sysctl tuneable blackhole MSS. */
687 tp->t_maxopd = V_tcp_pmtud_blackhole_mss;
688 V_tcp_pmtud_blackhole_activated++;
690 /* Use the default MSS. */
691 tp->t_maxopd = V_tcp_mssdflt;
693 * Disable Path MTU Discovery when we switch to
696 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
697 V_tcp_pmtud_blackhole_activated_min_mss++;
700 tp->t_maxseg = tp->t_maxopd - optlen;
702 * Reset the slow-start flight size
703 * as it may depend on the new MSS.
705 if (CC_ALGO(tp)->conn_init != NULL)
706 CC_ALGO(tp)->conn_init(tp->ccv);
709 * If further retransmissions are still unsuccessful
710 * with a lowered MTU, maybe this isn't a blackhole and
711 * we restore the previous MSS and blackhole detection
713 * The limit '6' is determined by giving each probe
714 * stage (1448, 1188, 524) 2 chances to recover.
716 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
717 (tp->t_rxtshift > 6)) {
718 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
719 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
720 optlen = tp->t_maxopd - tp->t_maxseg;
721 tp->t_maxopd = tp->t_pmtud_saved_maxopd;
722 tp->t_maxseg = tp->t_maxopd - optlen;
723 V_tcp_pmtud_blackhole_failed++;
725 * Reset the slow-start flight size as it
726 * may depend on the new MSS.
728 if (CC_ALGO(tp)->conn_init != NULL)
729 CC_ALGO(tp)->conn_init(tp->ccv);
735 * Disable RFC1323 and SACK if we haven't got any response to
736 * our third SYN to work-around some broken terminal servers
737 * (most of which have hopefully been retired) that have bad VJ
738 * header compression code which trashes TCP segments containing
739 * unknown-to-them TCP options.
741 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
742 (tp->t_rxtshift == 3))
743 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
745 * If we backed off this far, our srtt estimate is probably bogus.
746 * Clobber it so we'll take the next rtt measurement as our srtt;
747 * move the current srtt into rttvar to keep the current
748 * retransmit times until then.
750 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
752 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
753 in6_losing(tp->t_inpcb);
755 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
758 tp->snd_nxt = tp->snd_una;
759 tp->snd_recover = tp->snd_max;
761 * Force a segment to be sent.
763 tp->t_flags |= TF_ACKNOW;
765 * If timing a segment in this window, stop the timer.
769 cc_cong_signal(tp, NULL, CC_RTO);
771 (void) tcp_output(tp);
775 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
776 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
782 INP_INFO_WUNLOCK(&V_tcbinfo);
787 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
789 struct callout *t_callout;
790 timeout_t *f_callout;
791 struct inpcb *inp = tp->t_inpcb;
792 int cpu = INP_CPU(inp);
796 if (tp->t_flags & TF_TOE)
800 if (tp->t_timers->tt_flags & TT_STOPPED)
803 switch (timer_type) {
805 t_callout = &tp->t_timers->tt_delack;
806 f_callout = tcp_timer_delack;
807 f_reset = TT_DELACK_RST;
810 t_callout = &tp->t_timers->tt_rexmt;
811 f_callout = tcp_timer_rexmt;
812 f_reset = TT_REXMT_RST;
815 t_callout = &tp->t_timers->tt_persist;
816 f_callout = tcp_timer_persist;
817 f_reset = TT_PERSIST_RST;
820 t_callout = &tp->t_timers->tt_keep;
821 f_callout = tcp_timer_keep;
822 f_reset = TT_KEEP_RST;
825 t_callout = &tp->t_timers->tt_2msl;
826 f_callout = tcp_timer_2msl;
827 f_reset = TT_2MSL_RST;
830 panic("tp %p bad timer_type %#x", tp, timer_type);
833 if ((tp->t_timers->tt_flags & timer_type) &&
834 callout_stop(t_callout) &&
835 (tp->t_timers->tt_flags & f_reset)) {
836 tp->t_timers->tt_flags &= ~(timer_type | f_reset);
839 if ((tp->t_timers->tt_flags & timer_type) == 0) {
840 tp->t_timers->tt_flags |= (timer_type | f_reset);
841 callout_reset_on(t_callout, delta, f_callout, tp, cpu);
843 /* Reset already running callout on the same CPU. */
844 if (!callout_reset(t_callout, delta, f_callout, tp)) {
846 * Callout not cancelled, consider it as not
847 * properly restarted. */
848 tp->t_timers->tt_flags &= ~f_reset;
855 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
857 struct callout *t_callout;
859 switch (timer_type) {
861 t_callout = &tp->t_timers->tt_delack;
864 t_callout = &tp->t_timers->tt_rexmt;
867 t_callout = &tp->t_timers->tt_persist;
870 t_callout = &tp->t_timers->tt_keep;
873 t_callout = &tp->t_timers->tt_2msl;
876 panic("tp %p bad timer_type %#x", tp, timer_type);
878 return callout_active(t_callout);
882 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
884 struct callout *t_callout;
885 timeout_t *f_callout;
888 tp->t_timers->tt_flags |= TT_STOPPED;
890 switch (timer_type) {
892 t_callout = &tp->t_timers->tt_delack;
893 f_callout = tcp_timer_delack_discard;
894 f_reset = TT_DELACK_RST;
897 t_callout = &tp->t_timers->tt_rexmt;
898 f_callout = tcp_timer_rexmt_discard;
899 f_reset = TT_REXMT_RST;
902 t_callout = &tp->t_timers->tt_persist;
903 f_callout = tcp_timer_persist_discard;
904 f_reset = TT_PERSIST_RST;
907 t_callout = &tp->t_timers->tt_keep;
908 f_callout = tcp_timer_keep_discard;
909 f_reset = TT_KEEP_RST;
912 t_callout = &tp->t_timers->tt_2msl;
913 f_callout = tcp_timer_2msl_discard;
914 f_reset = TT_2MSL_RST;
917 panic("tp %p bad timer_type %#x", tp, timer_type);
920 if (tp->t_timers->tt_flags & timer_type) {
921 if (callout_stop(t_callout) &&
922 (tp->t_timers->tt_flags & f_reset)) {
923 tp->t_timers->tt_flags &= ~(timer_type | f_reset);
926 * Can't stop the callout, defer tcpcb actual deletion
927 * to the last tcp timer discard callout.
928 * The TT_STOPPED flag will ensure that no tcp timer
929 * callouts can be restarted on our behalf, and
930 * past this point currently running callouts waiting
931 * on inp lock will return right away after the
932 * classical check for callout reset/stop events:
933 * callout_pending() || !callout_active()
935 callout_reset(t_callout, 1, f_callout, tp);
940 #define ticks_to_msecs(t) (1000*(t) / hz)
943 tcp_timer_to_xtimer(struct tcpcb *tp, struct tcp_timer *timer,
944 struct xtcp_timer *xtimer)
948 bzero(xtimer, sizeof(*xtimer));
951 now = getsbinuptime();
952 if (callout_active(&timer->tt_delack))
953 xtimer->tt_delack = (timer->tt_delack.c_time - now) / SBT_1MS;
954 if (callout_active(&timer->tt_rexmt))
955 xtimer->tt_rexmt = (timer->tt_rexmt.c_time - now) / SBT_1MS;
956 if (callout_active(&timer->tt_persist))
957 xtimer->tt_persist = (timer->tt_persist.c_time - now) / SBT_1MS;
958 if (callout_active(&timer->tt_keep))
959 xtimer->tt_keep = (timer->tt_keep.c_time - now) / SBT_1MS;
960 if (callout_active(&timer->tt_2msl))
961 xtimer->tt_2msl = (timer->tt_2msl.c_time - now) / SBT_1MS;
962 xtimer->t_rcvtime = ticks_to_msecs(ticks - tp->t_rcvtime);