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