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