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