sys/netinet/tcp_timer.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  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.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  *      @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
  32  */
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 #include "opt_inet.h"
  38 #include "opt_inet6.h"
  39 #include "opt_tcpdebug.h"
  40 #include "opt_rss.h"
  41
  42 #include <sys/param.h>
  43 #include <sys/kernel.h>
  44 #include <sys/lock.h>
  45 #include <sys/mbuf.h>
  46 #include <sys/mutex.h>
  47 #include <sys/protosw.h>
  48 #include <sys/smp.h>
  49 #include <sys/socket.h>
  50 #include <sys/socketvar.h>
  51 #include <sys/sysctl.h>
  52 #include <sys/systm.h>
  53
  54 #include <net/if.h>
  55 #include <net/route.h>
  56 #include <net/rss_config.h>
  57 #include <net/vnet.h>
  58 #include <net/netisr.h>
  59
  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>
  65 #ifdef INET6
  66 #include <netinet6/in6_pcb.h>
  67 #endif
  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>
  76 #ifdef INET6
  77 #include <netinet6/tcp6_var.h>
  78 #endif
  79 #include <netinet/tcpip.h>
  80 #ifdef TCPDEBUG
  81 #include <netinet/tcp_debug.h>
  82 #endif
  83
  84 int    tcp_persmin;
  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");
  87
  88 int    tcp_persmax;
  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");
  91
  92 int     tcp_keepinit;
  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");
  95
  96 int     tcp_keepidle;
  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");
  99
 100 int     tcp_keepintvl;
 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");
 103
 104 int     tcp_delacktime;
 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");
 108
 109 int     tcp_msl;
 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");
 112
 113 int     tcp_rexmit_initial;
 114 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial, CTLTYPE_INT|CTLFLAG_RW,
 115     &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
 116     "Initial Retransmission Timeout");
 117
 118 int     tcp_rexmit_min;
 119 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
 120     &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
 121     "Minimum Retransmission Timeout");
 122
 123 int     tcp_rexmit_slop;
 124 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
 125     &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
 126     "Retransmission Timer Slop");
 127
 128 VNET_DEFINE(int, tcp_always_keepalive) = 1;
 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW,
 130     &VNET_NAME(tcp_always_keepalive) , 0,
 131     "Assume SO_KEEPALIVE on all TCP connections");
 132
 133 int    tcp_fast_finwait2_recycle = 0;
 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
 135     &tcp_fast_finwait2_recycle, 0,
 136     "Recycle closed FIN_WAIT_2 connections faster");
 137
 138 int    tcp_finwait2_timeout;
 139 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
 140     &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
 141
 142 int     tcp_keepcnt = TCPTV_KEEPCNT;
 143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
 144     "Number of keepalive probes to send");
 145
 146         /* max idle probes */
 147 int     tcp_maxpersistidle;
 148
 149 int     tcp_rexmit_drop_options = 0;
 150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
 151     &tcp_rexmit_drop_options, 0,
 152     "Drop TCP options from 3rd and later retransmitted SYN");
 153
 154 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
 155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
 156     CTLFLAG_RW|CTLFLAG_VNET,
 157     &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
 158     "Path MTU Discovery Black Hole Detection Enabled");
 159
 160 #ifdef INET
 161 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
 162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
 163     CTLFLAG_RW|CTLFLAG_VNET,
 164     &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
 165     "Path MTU Discovery Black Hole Detection lowered MSS");
 166 #endif
 167
 168 #ifdef INET6
 169 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
 170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
 171     CTLFLAG_RW|CTLFLAG_VNET,
 172     &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
 173     "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
 174 #endif
 175
 176 #ifdef  RSS
 177 static int      per_cpu_timers = 1;
 178 #else
 179 static int      per_cpu_timers = 0;
 180 #endif
 181 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
 182     &per_cpu_timers , 0, "run tcp timers on all cpus");
 183
 184 /*
 185  * Map the given inp to a CPU id.
 186  *
 187  * This queries RSS if it's compiled in, else it defaults to the current
 188  * CPU ID.
 189  */
 190 inline int
 191 inp_to_cpuid(struct inpcb *inp)
 192 {
 193         u_int cpuid;
 194
 195 #ifdef  RSS
 196         if (per_cpu_timers) {
 197                 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
 198                 if (cpuid == NETISR_CPUID_NONE)
 199                         return (curcpu);        /* XXX */
 200                 else
 201                         return (cpuid);
 202         }
 203 #else
 204         /* Legacy, pre-RSS behaviour */
 205         if (per_cpu_timers) {
 206                 /*
 207                  * We don't have a flowid -> cpuid mapping, so cheat and
 208                  * just map unknown cpuids to curcpu.  Not the best, but
 209                  * apparently better than defaulting to swi 0.
 210                  */
 211                 cpuid = inp->inp_flowid % (mp_maxid + 1);
 212                 if (! CPU_ABSENT(cpuid))
 213                         return (cpuid);
 214                 return (curcpu);
 215         }
 216 #endif
 217         /* Default for RSS and non-RSS - cpuid 0 */
 218         else {
 219                 return (0);
 220         }
 221 }
 222
 223 /*
 224  * Tcp protocol timeout routine called every 500 ms.
 225  * Updates timestamps used for TCP
 226  * causes finite state machine actions if timers expire.
 227  */
 228 void
 229 tcp_slowtimo(void)
 230 {
 231         VNET_ITERATOR_DECL(vnet_iter);
 232
 233         VNET_LIST_RLOCK_NOSLEEP();
 234         VNET_FOREACH(vnet_iter) {
 235                 CURVNET_SET(vnet_iter);
 236                 (void) tcp_tw_2msl_scan(0);
 237                 CURVNET_RESTORE();
 238         }
 239         VNET_LIST_RUNLOCK_NOSLEEP();
 240 }
 241
 242 int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
 243     { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
 244
 245 int tcp_totbackoff = 2559;      /* sum of tcp_backoff[] */
 246
 247 /*
 248  * TCP timer processing.
 249  */
 250
 251 void
 252 tcp_timer_delack(void *xtp)
 253 {
 254         struct epoch_tracker et;
 255         struct tcpcb *tp = xtp;
 256         struct inpcb *inp;
 257         CURVNET_SET(tp->t_vnet);
 258
 259         inp = tp->t_inpcb;
 260         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 261         INP_WLOCK(inp);
 262         if (callout_pending(&tp->t_timers->tt_delack) ||
 263             !callout_active(&tp->t_timers->tt_delack)) {
 264                 INP_WUNLOCK(inp);
 265                 CURVNET_RESTORE();
 266                 return;
 267         }
 268         callout_deactivate(&tp->t_timers->tt_delack);
 269         if ((inp->inp_flags & INP_DROPPED) != 0) {
 270                 INP_WUNLOCK(inp);
 271                 CURVNET_RESTORE();
 272                 return;
 273         }
 274         tp->t_flags |= TF_ACKNOW;
 275         TCPSTAT_INC(tcps_delack);
 276         NET_EPOCH_ENTER(et);
 277         (void) tp->t_fb->tfb_tcp_output(tp);
 278         INP_WUNLOCK(inp);
 279         NET_EPOCH_EXIT(et);
 280         CURVNET_RESTORE();
 281 }
 282
 283 void
 284 tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
 285 {
 286         if (inp && tp != NULL)
 287                 INP_WUNLOCK(inp);
 288 }
 289
 290 void
 291 tcp_timer_2msl(void *xtp)
 292 {
 293         struct tcpcb *tp = xtp;
 294         struct inpcb *inp;
 295         struct epoch_tracker et;
 296         CURVNET_SET(tp->t_vnet);
 297 #ifdef TCPDEBUG
 298         int ostate;
 299
 300         ostate = tp->t_state;
 301 #endif
 302         inp = tp->t_inpcb;
 303         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 304         INP_WLOCK(inp);
 305         tcp_free_sackholes(tp);
 306         if (callout_pending(&tp->t_timers->tt_2msl) ||
 307             !callout_active(&tp->t_timers->tt_2msl)) {
 308                 INP_WUNLOCK(tp->t_inpcb);
 309                 CURVNET_RESTORE();
 310                 return;
 311         }
 312         callout_deactivate(&tp->t_timers->tt_2msl);
 313         if ((inp->inp_flags & INP_DROPPED) != 0) {
 314                 INP_WUNLOCK(inp);
 315                 CURVNET_RESTORE();
 316                 return;
 317         }
 318         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
 319                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 320         /*
 321          * 2 MSL timeout in shutdown went off.  If we're closed but
 322          * still waiting for peer to close and connection has been idle
 323          * too long delete connection control block.  Otherwise, check
 324          * again in a bit.
 325          *
 326          * If in TIME_WAIT state just ignore as this timeout is handled in
 327          * tcp_tw_2msl_scan().
 328          *
 329          * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
 330          * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
 331          * Ignore fact that there were recent incoming segments.
 332          */
 333         if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
 334                 INP_WUNLOCK(inp);
 335                 CURVNET_RESTORE();
 336                 return;
 337         }
 338         if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
 339             tp->t_inpcb && tp->t_inpcb->inp_socket &&
 340             (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
 341                 TCPSTAT_INC(tcps_finwait2_drops);
 342                 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
 343                         tcp_inpinfo_lock_del(inp, tp);
 344                         goto out;
 345                 }
 346                 NET_EPOCH_ENTER(et);
 347                 tp = tcp_close(tp);
 348                 NET_EPOCH_EXIT(et);
 349                 tcp_inpinfo_lock_del(inp, tp);
 350                 goto out;
 351         } else {
 352                 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
 353                         callout_reset(&tp->t_timers->tt_2msl,
 354                                       TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
 355                 } else {
 356                         if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
 357                                 tcp_inpinfo_lock_del(inp, tp);
 358                                 goto out;
 359                         }
 360                         NET_EPOCH_ENTER(et);
 361                         tp = tcp_close(tp);
 362                         NET_EPOCH_EXIT(et);
 363                         tcp_inpinfo_lock_del(inp, tp);
 364                         goto out;
 365                 }
 366         }
 367
 368 #ifdef TCPDEBUG
 369         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 370                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 371                           PRU_SLOWTIMO);
 372 #endif
 373         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 374
 375         if (tp != NULL)
 376                 INP_WUNLOCK(inp);
 377 out:
 378         CURVNET_RESTORE();
 379 }
 380
 381 void
 382 tcp_timer_keep(void *xtp)
 383 {
 384         struct tcpcb *tp = xtp;
 385         struct tcptemp *t_template;
 386         struct inpcb *inp;
 387         struct epoch_tracker et;
 388         CURVNET_SET(tp->t_vnet);
 389 #ifdef TCPDEBUG
 390         int ostate;
 391
 392         ostate = tp->t_state;
 393 #endif
 394         inp = tp->t_inpcb;
 395         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 396         INP_WLOCK(inp);
 397         if (callout_pending(&tp->t_timers->tt_keep) ||
 398             !callout_active(&tp->t_timers->tt_keep)) {
 399                 INP_WUNLOCK(inp);
 400                 CURVNET_RESTORE();
 401                 return;
 402         }
 403         callout_deactivate(&tp->t_timers->tt_keep);
 404         if ((inp->inp_flags & INP_DROPPED) != 0) {
 405                 INP_WUNLOCK(inp);
 406                 CURVNET_RESTORE();
 407                 return;
 408         }
 409         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
 410                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 411
 412         /*
 413          * Because we don't regularly reset the keepalive callout in
 414          * the ESTABLISHED state, it may be that we don't actually need
 415          * to send a keepalive yet. If that occurs, schedule another
 416          * call for the next time the keepalive timer might expire.
 417          */
 418         if (TCPS_HAVEESTABLISHED(tp->t_state)) {
 419                 u_int idletime;
 420
 421                 idletime = ticks - tp->t_rcvtime;
 422                 if (idletime < TP_KEEPIDLE(tp)) {
 423                         callout_reset(&tp->t_timers->tt_keep,
 424                             TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
 425                         INP_WUNLOCK(inp);
 426                         CURVNET_RESTORE();
 427                         return;
 428                 }
 429         }
 430
 431         /*
 432          * Keep-alive timer went off; send something
 433          * or drop connection if idle for too long.
 434          */
 435         TCPSTAT_INC(tcps_keeptimeo);
 436         if (tp->t_state < TCPS_ESTABLISHED)
 437                 goto dropit;
 438         if ((V_tcp_always_keepalive ||
 439             inp->inp_socket->so_options & SO_KEEPALIVE) &&
 440             tp->t_state <= TCPS_CLOSING) {
 441                 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
 442                         goto dropit;
 443                 /*
 444                  * Send a packet designed to force a response
 445                  * if the peer is up and reachable:
 446                  * either an ACK if the connection is still alive,
 447                  * or an RST if the peer has closed the connection
 448                  * due to timeout or reboot.
 449                  * Using sequence number tp->snd_una-1
 450                  * causes the transmitted zero-length segment
 451                  * to lie outside the receive window;
 452                  * by the protocol spec, this requires the
 453                  * correspondent TCP to respond.
 454                  */
 455                 TCPSTAT_INC(tcps_keepprobe);
 456                 t_template = tcpip_maketemplate(inp);
 457                 if (t_template) {
 458                         NET_EPOCH_ENTER(et);
 459                         tcp_respond(tp, t_template->tt_ipgen,
 460                                     &t_template->tt_t, (struct mbuf *)NULL,
 461                                     tp->rcv_nxt, tp->snd_una - 1, 0);
 462                         NET_EPOCH_EXIT(et);
 463                         free(t_template, M_TEMP);
 464                 }
 465                 callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
 466                               tcp_timer_keep, tp);
 467         } else
 468                 callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
 469                               tcp_timer_keep, tp);
 470
 471 #ifdef TCPDEBUG
 472         if (inp->inp_socket->so_options & SO_DEBUG)
 473                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 474                           PRU_SLOWTIMO);
 475 #endif
 476         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 477         INP_WUNLOCK(inp);
 478         CURVNET_RESTORE();
 479         return;
 480
 481 dropit:
 482         TCPSTAT_INC(tcps_keepdrops);
 483         if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
 484                 tcp_inpinfo_lock_del(inp, tp);
 485                 goto out;
 486         }
 487         NET_EPOCH_ENTER(et);
 488         tp = tcp_drop(tp, ETIMEDOUT);
 489
 490 #ifdef TCPDEBUG
 491         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 492                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 493                           PRU_SLOWTIMO);
 494 #endif
 495         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 496         NET_EPOCH_EXIT(et);
 497         tcp_inpinfo_lock_del(inp, tp);
 498  out:
 499         CURVNET_RESTORE();
 500 }
 501
 502 void
 503 tcp_timer_persist(void *xtp)
 504 {
 505         struct tcpcb *tp = xtp;
 506         struct inpcb *inp;
 507         struct epoch_tracker et;
 508         CURVNET_SET(tp->t_vnet);
 509 #ifdef TCPDEBUG
 510         int ostate;
 511
 512         ostate = tp->t_state;
 513 #endif
 514         inp = tp->t_inpcb;
 515         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 516         INP_WLOCK(inp);
 517         if (callout_pending(&tp->t_timers->tt_persist) ||
 518             !callout_active(&tp->t_timers->tt_persist)) {
 519                 INP_WUNLOCK(inp);
 520                 CURVNET_RESTORE();
 521                 return;
 522         }
 523         callout_deactivate(&tp->t_timers->tt_persist);
 524         if ((inp->inp_flags & INP_DROPPED) != 0) {
 525                 INP_WUNLOCK(inp);
 526                 CURVNET_RESTORE();
 527                 return;
 528         }
 529         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
 530                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 531         /*
 532          * Persistence timer into zero window.
 533          * Force a byte to be output, if possible.
 534          */
 535         TCPSTAT_INC(tcps_persisttimeo);
 536         /*
 537          * Hack: if the peer is dead/unreachable, we do not
 538          * time out if the window is closed.  After a full
 539          * backoff, drop the connection if the idle time
 540          * (no responses to probes) reaches the maximum
 541          * backoff that we would use if retransmitting.
 542          */
 543         if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
 544             (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
 545              ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
 546                 TCPSTAT_INC(tcps_persistdrop);
 547                 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
 548                         tcp_inpinfo_lock_del(inp, tp);
 549                         goto out;
 550                 }
 551                 NET_EPOCH_ENTER(et);
 552                 tp = tcp_drop(tp, ETIMEDOUT);
 553                 NET_EPOCH_EXIT(et);
 554                 tcp_inpinfo_lock_del(inp, tp);
 555                 goto out;
 556         }
 557         /*
 558          * If the user has closed the socket then drop a persisting
 559          * connection after a much reduced timeout.
 560          */
 561         if (tp->t_state > TCPS_CLOSE_WAIT &&
 562             (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
 563                 TCPSTAT_INC(tcps_persistdrop);
 564                 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
 565                         tcp_inpinfo_lock_del(inp, tp);
 566                         goto out;
 567                 }
 568                 NET_EPOCH_ENTER(et);
 569                 tp = tcp_drop(tp, ETIMEDOUT);
 570                 NET_EPOCH_EXIT(et);
 571                 tcp_inpinfo_lock_del(inp, tp);
 572                 goto out;
 573         }
 574         tcp_setpersist(tp);
 575         tp->t_flags |= TF_FORCEDATA;
 576         NET_EPOCH_ENTER(et);
 577         (void) tp->t_fb->tfb_tcp_output(tp);
 578         NET_EPOCH_EXIT(et);
 579         tp->t_flags &= ~TF_FORCEDATA;
 580
 581 #ifdef TCPDEBUG
 582         if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
 583                 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
 584 #endif
 585         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 586         INP_WUNLOCK(inp);
 587 out:
 588         CURVNET_RESTORE();
 589 }
 590
 591 void
 592 tcp_timer_rexmt(void * xtp)
 593 {
 594         struct tcpcb *tp = xtp;
 595         CURVNET_SET(tp->t_vnet);
 596         int rexmt;
 597         struct inpcb *inp;
 598         struct epoch_tracker et;
 599 #ifdef TCPDEBUG
 600         int ostate;
 601
 602         ostate = tp->t_state;
 603 #endif
 604         inp = tp->t_inpcb;
 605         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 606         INP_WLOCK(inp);
 607         if (callout_pending(&tp->t_timers->tt_rexmt) ||
 608             !callout_active(&tp->t_timers->tt_rexmt)) {
 609                 INP_WUNLOCK(inp);
 610                 CURVNET_RESTORE();
 611                 return;
 612         }
 613         callout_deactivate(&tp->t_timers->tt_rexmt);
 614         if ((inp->inp_flags & INP_DROPPED) != 0) {
 615                 INP_WUNLOCK(inp);
 616                 CURVNET_RESTORE();
 617                 return;
 618         }
 619         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
 620                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 621         tcp_free_sackholes(tp);
 622         TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false);
 623         if (tp->t_fb->tfb_tcp_rexmit_tmr) {
 624                 /* The stack has a timer action too. */
 625                 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
 626         }
 627         /*
 628          * Retransmission timer went off.  Message has not
 629          * been acked within retransmit interval.  Back off
 630          * to a longer retransmit interval and retransmit one segment.
 631          */
 632         if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
 633                 tp->t_rxtshift = TCP_MAXRXTSHIFT;
 634                 TCPSTAT_INC(tcps_timeoutdrop);
 635                 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
 636                         tcp_inpinfo_lock_del(inp, tp);
 637                         goto out;
 638                 }
 639                 NET_EPOCH_ENTER(et);
 640                 tp = tcp_drop(tp, ETIMEDOUT);
 641                 NET_EPOCH_EXIT(et);
 642                 tcp_inpinfo_lock_del(inp, tp);
 643                 goto out;
 644         }
 645         if (tp->t_state == TCPS_SYN_SENT) {
 646                 /*
 647                  * If the SYN was retransmitted, indicate CWND to be
 648                  * limited to 1 segment in cc_conn_init().
 649                  */
 650                 tp->snd_cwnd = 1;
 651         } else if (tp->t_rxtshift == 1) {
 652                 /*
 653                  * first retransmit; record ssthresh and cwnd so they can
 654                  * be recovered if this turns out to be a "bad" retransmit.
 655                  * A retransmit is considered "bad" if an ACK for this
 656                  * segment is received within RTT/2 interval; the assumption
 657                  * here is that the ACK was already in flight.  See
 658                  * "On Estimating End-to-End Network Path Properties" by
 659                  * Allman and Paxson for more details.
 660                  */
 661                 tp->snd_cwnd_prev = tp->snd_cwnd;
 662                 tp->snd_ssthresh_prev = tp->snd_ssthresh;
 663                 tp->snd_recover_prev = tp->snd_recover;
 664                 if (IN_FASTRECOVERY(tp->t_flags))
 665                         tp->t_flags |= TF_WASFRECOVERY;
 666                 else
 667                         tp->t_flags &= ~TF_WASFRECOVERY;
 668                 if (IN_CONGRECOVERY(tp->t_flags))
 669                         tp->t_flags |= TF_WASCRECOVERY;
 670                 else
 671                         tp->t_flags &= ~TF_WASCRECOVERY;
 672                 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
 673                         tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
 674                 /* In the event that we've negotiated timestamps
 675                  * badrxtwin will be set to the value that we set
 676                  * the retransmitted packet's to_tsval to by tcp_output
 677                  */
 678                 tp->t_flags |= TF_PREVVALID;
 679         } else
 680                 tp->t_flags &= ~TF_PREVVALID;
 681         TCPSTAT_INC(tcps_rexmttimeo);
 682         if ((tp->t_state == TCPS_SYN_SENT) ||
 683             (tp->t_state == TCPS_SYN_RECEIVED))
 684                 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
 685         else
 686                 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
 687         TCPT_RANGESET(tp->t_rxtcur, rexmt,
 688                       tp->t_rttmin, TCPTV_REXMTMAX);
 689
 690         /*
 691          * We enter the path for PLMTUD if connection is established or, if
 692          * connection is FIN_WAIT_1 status, reason for the last is that if
 693          * amount of data we send is very small, we could send it in couple of
 694          * packets and process straight to FIN. In that case we won't catch
 695          * ESTABLISHED state.
 696          */
 697         if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
 698             || (tp->t_state == TCPS_FIN_WAIT_1))) {
 699 #ifdef INET6
 700                 int isipv6;
 701 #endif
 702
 703                 /*
 704                  * Idea here is that at each stage of mtu probe (usually, 1448
 705                  * -> 1188 -> 524) should be given 2 chances to recover before
 706                  *  further clamping down. 'tp->t_rxtshift % 2 == 0' should
 707                  *  take care of that.
 708                  */
 709                 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
 710                     (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
 711                     (tp->t_rxtshift >= 2 && tp->t_rxtshift < 6 &&
 712                     tp->t_rxtshift % 2 == 0)) {
 713                         /*
 714                          * Enter Path MTU Black-hole Detection mechanism:
 715                          * - Disable Path MTU Discovery (IP "DF" bit).
 716                          * - Reduce MTU to lower value than what we
 717                          *   negotiated with peer.
 718                          */
 719                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
 720                                 /* Record that we may have found a black hole. */
 721                                 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
 722                                 /* Keep track of previous MSS. */
 723                                 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
 724                         }
 725
 726                         /*
 727                          * Reduce the MSS to blackhole value or to the default
 728                          * in an attempt to retransmit.
 729                          */
 730 #ifdef INET6
 731                         isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
 732                         if (isipv6 &&
 733                             tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
 734                                 /* Use the sysctl tuneable blackhole MSS. */
 735                                 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
 736                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
 737                         } else if (isipv6) {
 738                                 /* Use the default MSS. */
 739                                 tp->t_maxseg = V_tcp_v6mssdflt;
 740                                 /*
 741                                  * Disable Path MTU Discovery when we switch to
 742                                  * minmss.
 743                                  */
 744                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
 745                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
 746                         }
 747 #endif
 748 #if defined(INET6) && defined(INET)
 749                         else
 750 #endif
 751 #ifdef INET
 752                         if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) {
 753                                 /* Use the sysctl tuneable blackhole MSS. */
 754                                 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
 755                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
 756                         } else {
 757                                 /* Use the default MSS. */
 758                                 tp->t_maxseg = V_tcp_mssdflt;
 759                                 /*
 760                                  * Disable Path MTU Discovery when we switch to
 761                                  * minmss.
 762                                  */
 763                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
 764                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
 765                         }
 766 #endif
 767                         /*
 768                          * Reset the slow-start flight size
 769                          * as it may depend on the new MSS.
 770                          */
 771                         if (CC_ALGO(tp)->conn_init != NULL)
 772                                 CC_ALGO(tp)->conn_init(tp->ccv);
 773                 } else {
 774                         /*
 775                          * If further retransmissions are still unsuccessful
 776                          * with a lowered MTU, maybe this isn't a blackhole and
 777                          * we restore the previous MSS and blackhole detection
 778                          * flags.
 779                          * The limit '6' is determined by giving each probe
 780                          * stage (1448, 1188, 524) 2 chances to recover.
 781                          */
 782                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
 783                             (tp->t_rxtshift >= 6)) {
 784                                 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
 785                                 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
 786                                 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
 787                                 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
 788                                 /*
 789                                  * Reset the slow-start flight size as it
 790                                  * may depend on the new MSS.
 791                                  */
 792                                 if (CC_ALGO(tp)->conn_init != NULL)
 793                                         CC_ALGO(tp)->conn_init(tp->ccv);
 794                         }
 795                 }
 796         }
 797
 798         /*
 799          * Disable RFC1323 and SACK if we haven't got any response to
 800          * our third SYN to work-around some broken terminal servers
 801          * (most of which have hopefully been retired) that have bad VJ
 802          * header compression code which trashes TCP segments containing
 803          * unknown-to-them TCP options.
 804          */
 805         if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
 806             (tp->t_rxtshift == 3))
 807                 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
 808         /*
 809          * If we backed off this far, notify the L3 protocol that we're having
 810          * connection problems.
 811          */
 812         if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
 813 #ifdef INET6
 814                 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
 815                         in6_losing(tp->t_inpcb);
 816                 else
 817 #endif
 818                         in_losing(tp->t_inpcb);
 819         }
 820         tp->snd_nxt = tp->snd_una;
 821         tp->snd_recover = tp->snd_max;
 822         /*
 823          * Force a segment to be sent.
 824          */
 825         tp->t_flags |= TF_ACKNOW;
 826         /*
 827          * If timing a segment in this window, stop the timer.
 828          */
 829         tp->t_rtttime = 0;
 830
 831         cc_cong_signal(tp, NULL, CC_RTO);
 832         NET_EPOCH_ENTER(et);
 833         (void) tp->t_fb->tfb_tcp_output(tp);
 834         NET_EPOCH_EXIT(et);
 835 #ifdef TCPDEBUG
 836         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 837                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 838                           PRU_SLOWTIMO);
 839 #endif
 840         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 841         INP_WUNLOCK(inp);
 842 out:
 843         CURVNET_RESTORE();
 844 }
 845
 846 void
 847 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
 848 {
 849         struct callout *t_callout;
 850         callout_func_t *f_callout;
 851         struct inpcb *inp = tp->t_inpcb;
 852         int cpu = inp_to_cpuid(inp);
 853
 854 #ifdef TCP_OFFLOAD
 855         if (tp->t_flags & TF_TOE)
 856                 return;
 857 #endif
 858
 859         if (tp->t_timers->tt_flags & TT_STOPPED)
 860                 return;
 861
 862         switch (timer_type) {
 863                 case TT_DELACK:
 864                         t_callout = &tp->t_timers->tt_delack;
 865                         f_callout = tcp_timer_delack;
 866                         break;
 867                 case TT_REXMT:
 868                         t_callout = &tp->t_timers->tt_rexmt;
 869                         f_callout = tcp_timer_rexmt;
 870                         break;
 871                 case TT_PERSIST:
 872                         t_callout = &tp->t_timers->tt_persist;
 873                         f_callout = tcp_timer_persist;
 874                         break;
 875                 case TT_KEEP:
 876                         t_callout = &tp->t_timers->tt_keep;
 877                         f_callout = tcp_timer_keep;
 878                         break;
 879                 case TT_2MSL:
 880                         t_callout = &tp->t_timers->tt_2msl;
 881                         f_callout = tcp_timer_2msl;
 882                         break;
 883                 default:
 884                         if (tp->t_fb->tfb_tcp_timer_activate) {
 885                                 tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
 886                                 return;
 887                         }
 888                         panic("tp %p bad timer_type %#x", tp, timer_type);
 889                 }
 890         if (delta == 0) {
 891                 callout_stop(t_callout);
 892         } else {
 893                 callout_reset_on(t_callout, delta, f_callout, tp, cpu);
 894         }
 895 }
 896
 897 int
 898 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
 899 {
 900         struct callout *t_callout;
 901
 902         switch (timer_type) {
 903                 case TT_DELACK:
 904                         t_callout = &tp->t_timers->tt_delack;
 905                         break;
 906                 case TT_REXMT:
 907                         t_callout = &tp->t_timers->tt_rexmt;
 908                         break;
 909                 case TT_PERSIST:
 910                         t_callout = &tp->t_timers->tt_persist;
 911                         break;
 912                 case TT_KEEP:
 913                         t_callout = &tp->t_timers->tt_keep;
 914                         break;
 915                 case TT_2MSL:
 916                         t_callout = &tp->t_timers->tt_2msl;
 917                         break;
 918                 default:
 919                         if (tp->t_fb->tfb_tcp_timer_active) {
 920                                 return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
 921                         }
 922                         panic("tp %p bad timer_type %#x", tp, timer_type);
 923                 }
 924         return callout_active(t_callout);
 925 }
 926
 927 /*
 928  * Stop the timer from running, and apply a flag
 929  * against the timer_flags that will force the
 930  * timer never to run. The flag is needed to assure
 931  * a race does not leave it running and cause
 932  * the timer to possibly restart itself (keep and persist
 933  * especially do this).
 934  */
 935 int
 936 tcp_timer_suspend(struct tcpcb *tp, uint32_t timer_type)
 937 {
 938         struct callout *t_callout;
 939         uint32_t t_flags;
 940
 941         switch (timer_type) {
 942                 case TT_DELACK:
 943                         t_flags = TT_DELACK_SUS;
 944                         t_callout = &tp->t_timers->tt_delack;
 945                         break;
 946                 case TT_REXMT:
 947                         t_flags = TT_REXMT_SUS;
 948                         t_callout = &tp->t_timers->tt_rexmt;
 949                         break;
 950                 case TT_PERSIST:
 951                         t_flags = TT_PERSIST_SUS;
 952                         t_callout = &tp->t_timers->tt_persist;
 953                         break;
 954                 case TT_KEEP:
 955                         t_flags = TT_KEEP_SUS;
 956                         t_callout = &tp->t_timers->tt_keep;
 957                         break;
 958                 case TT_2MSL:
 959                         t_flags = TT_2MSL_SUS;
 960                         t_callout = &tp->t_timers->tt_2msl;
 961                         break;
 962                 default:
 963                         panic("tp:%p bad timer_type 0x%x", tp, timer_type);
 964         }
 965         tp->t_timers->tt_flags |= t_flags;
 966         return (callout_stop(t_callout));
 967 }
 968
 969 void
 970 tcp_timers_unsuspend(struct tcpcb *tp, uint32_t timer_type)
 971 {
 972         switch (timer_type) {
 973                 case TT_DELACK:
 974                         if (tp->t_timers->tt_flags & TT_DELACK_SUS) {
 975                                 tp->t_timers->tt_flags &= ~TT_DELACK_SUS;
 976                                 if (tp->t_flags & TF_DELACK) {
 977                                         /* Delayed ack timer should be up activate a timer */
 978                                         tp->t_flags &= ~TF_DELACK;
 979                                         tcp_timer_activate(tp, TT_DELACK,
 980                                             tcp_delacktime);
 981                                 }
 982                         }
 983                         break;
 984                 case TT_REXMT:
 985                         if (tp->t_timers->tt_flags & TT_REXMT_SUS) {
 986                                 tp->t_timers->tt_flags &= ~TT_REXMT_SUS;
 987                                 if (SEQ_GT(tp->snd_max, tp->snd_una) &&
 988                                     (tcp_timer_active((tp), TT_PERSIST) == 0) &&
 989                                     tp->snd_wnd) {
 990                                         /* We have outstanding data activate a timer */
 991                                         tcp_timer_activate(tp, TT_REXMT,
 992                                             tp->t_rxtcur);
 993                                 }
 994                         }
 995                         break;
 996                 case TT_PERSIST:
 997                         if (tp->t_timers->tt_flags & TT_PERSIST_SUS) {
 998                                 tp->t_timers->tt_flags &= ~TT_PERSIST_SUS;
 999                                 if (tp->snd_wnd == 0) {
1000                                         /* Activate the persists timer */
1001                                         tp->t_rxtshift = 0;
1002                                         tcp_setpersist(tp);
1003                                 }
1004                         }
1005                         break;
1006                 case TT_KEEP:
1007                         if (tp->t_timers->tt_flags & TT_KEEP_SUS) {
1008                                 tp->t_timers->tt_flags &= ~TT_KEEP_SUS;
1009                                 tcp_timer_activate(tp, TT_KEEP,
1010                                             TCPS_HAVEESTABLISHED(tp->t_state) ?
1011                                             TP_KEEPIDLE(tp) : TP_KEEPINIT(tp));
1012                         }
1013                         break;
1014                 case TT_2MSL:
1015                         if (tp->t_timers->tt_flags &= TT_2MSL_SUS) {
1016                                 tp->t_timers->tt_flags &= ~TT_2MSL_SUS;
1017                                 if ((tp->t_state == TCPS_FIN_WAIT_2) &&
1018                                     ((tp->t_inpcb->inp_socket == NULL) ||
1019                                      (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE))) {
1020                                         /* Star the 2MSL timer */
1021                                         tcp_timer_activate(tp, TT_2MSL,
1022                                             (tcp_fast_finwait2_recycle) ?
1023                                             tcp_finwait2_timeout : TP_MAXIDLE(tp));
1024                                 }
1025                         }
1026                         break;
1027                 default:
1028                         panic("tp:%p bad timer_type 0x%x", tp, timer_type);
1029         }
1030 }
1031
1032 void
1033 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
1034 {
1035         struct callout *t_callout;
1036
1037         tp->t_timers->tt_flags |= TT_STOPPED;
1038         switch (timer_type) {
1039                 case TT_DELACK:
1040                         t_callout = &tp->t_timers->tt_delack;
1041                         break;
1042                 case TT_REXMT:
1043                         t_callout = &tp->t_timers->tt_rexmt;
1044                         break;
1045                 case TT_PERSIST:
1046                         t_callout = &tp->t_timers->tt_persist;
1047                         break;
1048                 case TT_KEEP:
1049                         t_callout = &tp->t_timers->tt_keep;
1050                         break;
1051                 case TT_2MSL:
1052                         t_callout = &tp->t_timers->tt_2msl;
1053                         break;
1054                 default:
1055                         if (tp->t_fb->tfb_tcp_timer_stop) {
1056                                 /*
1057                                  * XXXrrs we need to look at this with the
1058                                  * stop case below (flags).
1059                                  */
1060                                 tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
1061                                 return;
1062                         }
1063                         panic("tp %p bad timer_type %#x", tp, timer_type);
1064                 }
1065
1066         if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
1067                 /*
1068                  * Can't stop the callout, defer tcpcb actual deletion
1069                  * to the last one. We do this using the async drain
1070                  * function and incrementing the count in
1071                  */
1072                 tp->t_timers->tt_draincnt++;
1073         }
1074 }