sys/netinet/tcp_timer.c

   1 /*-
   2  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
  30  */
  31
  32 #include <sys/cdefs.h>
  33 __FBSDID("$FreeBSD$");
  34
  35 #include "opt_inet6.h"
  36 #include "opt_tcpdebug.h"
  37
  38 #include <sys/param.h>
  39 #include <sys/kernel.h>
  40 #include <sys/lock.h>
  41 #include <sys/mbuf.h>
  42 #include <sys/mutex.h>
  43 #include <sys/protosw.h>
  44 #include <sys/socket.h>
  45 #include <sys/socketvar.h>
  46 #include <sys/sysctl.h>
  47 #include <sys/systm.h>
  48
  49 #include <net/if.h>
  50 #include <net/route.h>
  51 #include <net/vnet.h>
  52
  53 #include <netinet/cc.h>
  54 #include <netinet/in.h>
  55 #include <netinet/in_pcb.h>
  56 #include <netinet/in_systm.h>
  57 #ifdef INET6
  58 #include <netinet6/in6_pcb.h>
  59 #endif
  60 #include <netinet/ip_var.h>
  61 #include <netinet/tcp_fsm.h>
  62 #include <netinet/tcp_timer.h>
  63 #include <netinet/tcp_var.h>
  64 #include <netinet/tcpip.h>
  65 #ifdef TCPDEBUG
  66 #include <netinet/tcp_debug.h>
  67 #endif
  68
  69 int     tcp_keepinit;
  70 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
  71     &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
  72
  73 int     tcp_keepidle;
  74 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
  75     &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
  76
  77 int     tcp_keepintvl;
  78 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
  79     &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
  80
  81 int     tcp_delacktime;
  82 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
  83     &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
  84     "Time before a delayed ACK is sent");
  85
  86 int     tcp_msl;
  87 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
  88     &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
  89
  90 int     tcp_rexmit_min;
  91 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
  92     &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
  93     "Minimum Retransmission Timeout");
  94
  95 int     tcp_rexmit_slop;
  96 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
  97     &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
  98     "Retransmission Timer Slop");
  99
 100 static int      always_keepalive = 1;
 101 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
 102     &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
 103
 104 int    tcp_fast_finwait2_recycle = 0;
 105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
 106     &tcp_fast_finwait2_recycle, 0,
 107     "Recycle closed FIN_WAIT_2 connections faster");
 108
 109 int    tcp_finwait2_timeout;
 110 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
 111     &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
 112
 113
 114 static int      tcp_keepcnt = TCPTV_KEEPCNT;
 115         /* max idle probes */
 116 int     tcp_maxpersistidle;
 117         /* max idle time in persist */
 118 int     tcp_maxidle;
 119
 120 static int      tcp_rexmit_drop_options = 1;
 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
 122     &tcp_rexmit_drop_options, 0,
 123     "Drop TCP options from 3rd and later retransmitted SYN");
 124
 125 /*
 126  * Tcp protocol timeout routine called every 500 ms.
 127  * Updates timestamps used for TCP
 128  * causes finite state machine actions if timers expire.
 129  */
 130 void
 131 tcp_slowtimo(void)
 132 {
 133         VNET_ITERATOR_DECL(vnet_iter);
 134
 135         VNET_LIST_RLOCK_NOSLEEP();
 136         VNET_FOREACH(vnet_iter) {
 137                 CURVNET_SET(vnet_iter);
 138                 tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
 139                 INP_INFO_WLOCK(&V_tcbinfo);
 140                 (void) tcp_tw_2msl_scan(0);
 141                 INP_INFO_WUNLOCK(&V_tcbinfo);
 142                 CURVNET_RESTORE();
 143         }
 144         VNET_LIST_RUNLOCK_NOSLEEP();
 145 }
 146
 147 int     tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
 148     { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
 149
 150 int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
 151     { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
 152
 153 static int tcp_totbackoff = 2559;       /* sum of tcp_backoff[] */
 154
 155 static int tcp_timer_race;
 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, timer_race, CTLFLAG_RD, &tcp_timer_race,
 157     0, "Count of t_inpcb races on tcp_discardcb");
 158
 159 /*
 160  * TCP timer processing.
 161  */
 162
 163 void
 164 tcp_timer_delack(void *xtp)
 165 {
 166         struct tcpcb *tp = xtp;
 167         struct inpcb *inp;
 168         CURVNET_SET(tp->t_vnet);
 169
 170         inp = tp->t_inpcb;
 171         /*
 172          * XXXRW: While this assert is in fact correct, bugs in the tcpcb
 173          * tear-down mean we need it as a work-around for races between
 174          * timers and tcp_discardcb().
 175          *
 176          * KASSERT(inp != NULL, ("tcp_timer_delack: inp == NULL"));
 177          */
 178         if (inp == NULL) {
 179                 tcp_timer_race++;
 180                 CURVNET_RESTORE();
 181                 return;
 182         }
 183         INP_WLOCK(inp);
 184         if (callout_pending(&tp->t_timers->tt_delack) ||
 185             !callout_active(&tp->t_timers->tt_delack)) {
 186                 INP_WUNLOCK(inp);
 187                 CURVNET_RESTORE();
 188                 return;
 189         }
 190         callout_deactivate(&tp->t_timers->tt_delack);
 191         if ((inp->inp_flags & INP_DROPPED) != 0) {
 192                 INP_WUNLOCK(inp);
 193                 CURVNET_RESTORE();
 194                 return;
 195         }
 196
 197         tp->t_flags |= TF_ACKNOW;
 198         TCPSTAT_INC(tcps_delack);
 199         (void) tcp_output(tp);
 200         INP_WUNLOCK(inp);
 201         CURVNET_RESTORE();
 202 }
 203
 204 void
 205 tcp_timer_2msl(void *xtp)
 206 {
 207         struct tcpcb *tp = xtp;
 208         struct inpcb *inp;
 209         CURVNET_SET(tp->t_vnet);
 210 #ifdef TCPDEBUG
 211         int ostate;
 212
 213         ostate = tp->t_state;
 214 #endif
 215         /*
 216          * XXXRW: Does this actually happen?
 217          */
 218         INP_INFO_WLOCK(&V_tcbinfo);
 219         inp = tp->t_inpcb;
 220         /*
 221          * XXXRW: While this assert is in fact correct, bugs in the tcpcb
 222          * tear-down mean we need it as a work-around for races between
 223          * timers and tcp_discardcb().
 224          *
 225          * KASSERT(inp != NULL, ("tcp_timer_2msl: inp == NULL"));
 226          */
 227         if (inp == NULL) {
 228                 tcp_timer_race++;
 229                 INP_INFO_WUNLOCK(&V_tcbinfo);
 230                 CURVNET_RESTORE();
 231                 return;
 232         }
 233         INP_WLOCK(inp);
 234         tcp_free_sackholes(tp);
 235         if (callout_pending(&tp->t_timers->tt_2msl) ||
 236             !callout_active(&tp->t_timers->tt_2msl)) {
 237                 INP_WUNLOCK(tp->t_inpcb);
 238                 INP_INFO_WUNLOCK(&V_tcbinfo);
 239                 CURVNET_RESTORE();
 240                 return;
 241         }
 242         callout_deactivate(&tp->t_timers->tt_2msl);
 243         if ((inp->inp_flags & INP_DROPPED) != 0) {
 244                 INP_WUNLOCK(inp);
 245                 INP_INFO_WUNLOCK(&V_tcbinfo);
 246                 CURVNET_RESTORE();
 247                 return;
 248         }
 249         /*
 250          * 2 MSL timeout in shutdown went off.  If we're closed but
 251          * still waiting for peer to close and connection has been idle
 252          * too long, or if 2MSL time is up from TIME_WAIT, delete connection
 253          * control block.  Otherwise, check again in a bit.
 254          *
 255          * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
 256          * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
 257          * Ignore fact that there were recent incoming segments.
 258          */
 259         if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
 260             tp->t_inpcb && tp->t_inpcb->inp_socket &&
 261             (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
 262                 TCPSTAT_INC(tcps_finwait2_drops);
 263                 tp = tcp_close(tp);
 264         } else {
 265                 if (tp->t_state != TCPS_TIME_WAIT &&
 266                    ticks - tp->t_rcvtime <= tcp_maxidle)
 267                        callout_reset(&tp->t_timers->tt_2msl, tcp_keepintvl,
 268                                      tcp_timer_2msl, tp);
 269                else
 270                        tp = tcp_close(tp);
 271        }
 272
 273 #ifdef TCPDEBUG
 274         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 275                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 276                           PRU_SLOWTIMO);
 277 #endif
 278         if (tp != NULL)
 279                 INP_WUNLOCK(inp);
 280         INP_INFO_WUNLOCK(&V_tcbinfo);
 281         CURVNET_RESTORE();
 282 }
 283
 284 void
 285 tcp_timer_keep(void *xtp)
 286 {
 287         struct tcpcb *tp = xtp;
 288         struct tcptemp *t_template;
 289         struct inpcb *inp;
 290         CURVNET_SET(tp->t_vnet);
 291 #ifdef TCPDEBUG
 292         int ostate;
 293
 294         ostate = tp->t_state;
 295 #endif
 296         INP_INFO_WLOCK(&V_tcbinfo);
 297         inp = tp->t_inpcb;
 298         /*
 299          * XXXRW: While this assert is in fact correct, bugs in the tcpcb
 300          * tear-down mean we need it as a work-around for races between
 301          * timers and tcp_discardcb().
 302          *
 303          * KASSERT(inp != NULL, ("tcp_timer_keep: inp == NULL"));
 304          */
 305         if (inp == NULL) {
 306                 tcp_timer_race++;
 307                 INP_INFO_WUNLOCK(&V_tcbinfo);
 308                 CURVNET_RESTORE();
 309                 return;
 310         }
 311         INP_WLOCK(inp);
 312         if (callout_pending(&tp->t_timers->tt_keep) ||
 313             !callout_active(&tp->t_timers->tt_keep)) {
 314                 INP_WUNLOCK(inp);
 315                 INP_INFO_WUNLOCK(&V_tcbinfo);
 316                 CURVNET_RESTORE();
 317                 return;
 318         }
 319         callout_deactivate(&tp->t_timers->tt_keep);
 320         if ((inp->inp_flags & INP_DROPPED) != 0) {
 321                 INP_WUNLOCK(inp);
 322                 INP_INFO_WUNLOCK(&V_tcbinfo);
 323                 CURVNET_RESTORE();
 324                 return;
 325         }
 326         /*
 327          * Keep-alive timer went off; send something
 328          * or drop connection if idle for too long.
 329          */
 330         TCPSTAT_INC(tcps_keeptimeo);
 331         if (tp->t_state < TCPS_ESTABLISHED)
 332                 goto dropit;
 333         if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) &&
 334             tp->t_state <= TCPS_CLOSING) {
 335                 if (ticks - tp->t_rcvtime >= tcp_keepidle + tcp_maxidle)
 336                         goto dropit;
 337                 /*
 338                  * Send a packet designed to force a response
 339                  * if the peer is up and reachable:
 340                  * either an ACK if the connection is still alive,
 341                  * or an RST if the peer has closed the connection
 342                  * due to timeout or reboot.
 343                  * Using sequence number tp->snd_una-1
 344                  * causes the transmitted zero-length segment
 345                  * to lie outside the receive window;
 346                  * by the protocol spec, this requires the
 347                  * correspondent TCP to respond.
 348                  */
 349                 TCPSTAT_INC(tcps_keepprobe);
 350                 t_template = tcpip_maketemplate(inp);
 351                 if (t_template) {
 352                         tcp_respond(tp, t_template->tt_ipgen,
 353                                     &t_template->tt_t, (struct mbuf *)NULL,
 354                                     tp->rcv_nxt, tp->snd_una - 1, 0);
 355                         free(t_template, M_TEMP);
 356                 }
 357                 callout_reset(&tp->t_timers->tt_keep, tcp_keepintvl, tcp_timer_keep, tp);
 358         } else
 359                 callout_reset(&tp->t_timers->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
 360
 361 #ifdef TCPDEBUG
 362         if (inp->inp_socket->so_options & SO_DEBUG)
 363                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 364                           PRU_SLOWTIMO);
 365 #endif
 366         INP_WUNLOCK(inp);
 367         INP_INFO_WUNLOCK(&V_tcbinfo);
 368         CURVNET_RESTORE();
 369         return;
 370
 371 dropit:
 372         TCPSTAT_INC(tcps_keepdrops);
 373         tp = tcp_drop(tp, ETIMEDOUT);
 374
 375 #ifdef TCPDEBUG
 376         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 377                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 378                           PRU_SLOWTIMO);
 379 #endif
 380         if (tp != NULL)
 381                 INP_WUNLOCK(tp->t_inpcb);
 382         INP_INFO_WUNLOCK(&V_tcbinfo);
 383         CURVNET_RESTORE();
 384 }
 385
 386 void
 387 tcp_timer_persist(void *xtp)
 388 {
 389         struct tcpcb *tp = xtp;
 390         struct inpcb *inp;
 391         CURVNET_SET(tp->t_vnet);
 392 #ifdef TCPDEBUG
 393         int ostate;
 394
 395         ostate = tp->t_state;
 396 #endif
 397         INP_INFO_WLOCK(&V_tcbinfo);
 398         inp = tp->t_inpcb;
 399         /*
 400          * XXXRW: While this assert is in fact correct, bugs in the tcpcb
 401          * tear-down mean we need it as a work-around for races between
 402          * timers and tcp_discardcb().
 403          *
 404          * KASSERT(inp != NULL, ("tcp_timer_persist: inp == NULL"));
 405          */
 406         if (inp == NULL) {
 407                 tcp_timer_race++;
 408                 INP_INFO_WUNLOCK(&V_tcbinfo);
 409                 CURVNET_RESTORE();
 410                 return;
 411         }
 412         INP_WLOCK(inp);
 413         if (callout_pending(&tp->t_timers->tt_persist) ||
 414             !callout_active(&tp->t_timers->tt_persist)) {
 415                 INP_WUNLOCK(inp);
 416                 INP_INFO_WUNLOCK(&V_tcbinfo);
 417                 CURVNET_RESTORE();
 418                 return;
 419         }
 420         callout_deactivate(&tp->t_timers->tt_persist);
 421         if ((inp->inp_flags & INP_DROPPED) != 0) {
 422                 INP_WUNLOCK(inp);
 423                 INP_INFO_WUNLOCK(&V_tcbinfo);
 424                 CURVNET_RESTORE();
 425                 return;
 426         }
 427         /*
 428          * Persistance timer into zero window.
 429          * Force a byte to be output, if possible.
 430          */
 431         TCPSTAT_INC(tcps_persisttimeo);
 432         /*
 433          * Hack: if the peer is dead/unreachable, we do not
 434          * time out if the window is closed.  After a full
 435          * backoff, drop the connection if the idle time
 436          * (no responses to probes) reaches the maximum
 437          * backoff that we would use if retransmitting.
 438          */
 439         if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
 440             (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
 441              ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
 442                 TCPSTAT_INC(tcps_persistdrop);
 443                 tp = tcp_drop(tp, ETIMEDOUT);
 444                 goto out;
 445         }
 446         tcp_setpersist(tp);
 447         tp->t_flags |= TF_FORCEDATA;
 448         (void) tcp_output(tp);
 449         tp->t_flags &= ~TF_FORCEDATA;
 450
 451 out:
 452 #ifdef TCPDEBUG
 453         if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
 454                 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
 455 #endif
 456         if (tp != NULL)
 457                 INP_WUNLOCK(inp);
 458         INP_INFO_WUNLOCK(&V_tcbinfo);
 459         CURVNET_RESTORE();
 460 }
 461
 462 void
 463 tcp_timer_rexmt(void * xtp)
 464 {
 465         struct tcpcb *tp = xtp;
 466         CURVNET_SET(tp->t_vnet);
 467         int rexmt;
 468         int headlocked;
 469         struct inpcb *inp;
 470 #ifdef TCPDEBUG
 471         int ostate;
 472
 473         ostate = tp->t_state;
 474 #endif
 475         INP_INFO_WLOCK(&V_tcbinfo);
 476         headlocked = 1;
 477         inp = tp->t_inpcb;
 478         /*
 479          * XXXRW: While this assert is in fact correct, bugs in the tcpcb
 480          * tear-down mean we need it as a work-around for races between
 481          * timers and tcp_discardcb().
 482          *
 483          * KASSERT(inp != NULL, ("tcp_timer_rexmt: inp == NULL"));
 484          */
 485         if (inp == NULL) {
 486                 tcp_timer_race++;
 487                 INP_INFO_WUNLOCK(&V_tcbinfo);
 488                 CURVNET_RESTORE();
 489                 return;
 490         }
 491         INP_WLOCK(inp);
 492         if (callout_pending(&tp->t_timers->tt_rexmt) ||
 493             !callout_active(&tp->t_timers->tt_rexmt)) {
 494                 INP_WUNLOCK(inp);
 495                 INP_INFO_WUNLOCK(&V_tcbinfo);
 496                 CURVNET_RESTORE();
 497                 return;
 498         }
 499         callout_deactivate(&tp->t_timers->tt_rexmt);
 500         if ((inp->inp_flags & INP_DROPPED) != 0) {
 501                 INP_WUNLOCK(inp);
 502                 INP_INFO_WUNLOCK(&V_tcbinfo);
 503                 CURVNET_RESTORE();
 504                 return;
 505         }
 506         tcp_free_sackholes(tp);
 507         /*
 508          * Retransmission timer went off.  Message has not
 509          * been acked within retransmit interval.  Back off
 510          * to a longer retransmit interval and retransmit one segment.
 511          */
 512         if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
 513                 tp->t_rxtshift = TCP_MAXRXTSHIFT;
 514                 TCPSTAT_INC(tcps_timeoutdrop);
 515                 tp = tcp_drop(tp, tp->t_softerror ?
 516                               tp->t_softerror : ETIMEDOUT);
 517                 goto out;
 518         }
 519         INP_INFO_WUNLOCK(&V_tcbinfo);
 520         headlocked = 0;
 521         if (tp->t_rxtshift == 1) {
 522                 /*
 523                  * first retransmit; record ssthresh and cwnd so they can
 524                  * be recovered if this turns out to be a "bad" retransmit.
 525                  * A retransmit is considered "bad" if an ACK for this
 526                  * segment is received within RTT/2 interval; the assumption
 527                  * here is that the ACK was already in flight.  See
 528                  * "On Estimating End-to-End Network Path Properties" by
 529                  * Allman and Paxson for more details.
 530                  */
 531                 tp->snd_cwnd_prev = tp->snd_cwnd;
 532                 tp->snd_ssthresh_prev = tp->snd_ssthresh;
 533                 tp->snd_recover_prev = tp->snd_recover;
 534                 if (IN_FASTRECOVERY(tp->t_flags))
 535                         tp->t_flags |= TF_WASFRECOVERY;
 536                 else
 537                         tp->t_flags &= ~TF_WASFRECOVERY;
 538                 if (IN_CONGRECOVERY(tp->t_flags))
 539                         tp->t_flags |= TF_WASCRECOVERY;
 540                 else
 541                         tp->t_flags &= ~TF_WASCRECOVERY;
 542                 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
 543                 tp->t_flags |= TF_PREVVALID;
 544         } else
 545                 tp->t_flags &= ~TF_PREVVALID;
 546         TCPSTAT_INC(tcps_rexmttimeo);
 547         if (tp->t_state == TCPS_SYN_SENT)
 548                 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift];
 549         else
 550                 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
 551         TCPT_RANGESET(tp->t_rxtcur, rexmt,
 552                       tp->t_rttmin, TCPTV_REXMTMAX);
 553         /*
 554          * Disable rfc1323 if we haven't got any response to
 555          * our third SYN to work-around some broken terminal servers
 556          * (most of which have hopefully been retired) that have bad VJ
 557          * header compression code which trashes TCP segments containing
 558          * unknown-to-them TCP options.
 559          */
 560         if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
 561             (tp->t_rxtshift == 3))
 562                 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP);
 563         /*
 564          * If we backed off this far, our srtt estimate is probably bogus.
 565          * Clobber it so we'll take the next rtt measurement as our srtt;
 566          * move the current srtt into rttvar to keep the current
 567          * retransmit times until then.
 568          */
 569         if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
 570 #ifdef INET6
 571                 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
 572                         in6_losing(tp->t_inpcb);
 573                 else
 574 #endif
 575                 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
 576                 tp->t_srtt = 0;
 577         }
 578         tp->snd_nxt = tp->snd_una;
 579         tp->snd_recover = tp->snd_max;
 580         /*
 581          * Force a segment to be sent.
 582          */
 583         tp->t_flags |= TF_ACKNOW;
 584         /*
 585          * If timing a segment in this window, stop the timer.
 586          */
 587         tp->t_rtttime = 0;
 588
 589         cc_cong_signal(tp, NULL, CC_RTO);
 590
 591         (void) tcp_output(tp);
 592
 593 out:
 594 #ifdef TCPDEBUG
 595         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 596                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 597                           PRU_SLOWTIMO);
 598 #endif
 599         if (tp != NULL)
 600                 INP_WUNLOCK(inp);
 601         if (headlocked)
 602                 INP_INFO_WUNLOCK(&V_tcbinfo);
 603         CURVNET_RESTORE();
 604 }
 605
 606 void
 607 tcp_timer_activate(struct tcpcb *tp, int timer_type, u_int delta)
 608 {
 609         struct callout *t_callout;
 610         void *f_callout;
 611
 612         switch (timer_type) {
 613                 case TT_DELACK:
 614                         t_callout = &tp->t_timers->tt_delack;
 615                         f_callout = tcp_timer_delack;
 616                         break;
 617                 case TT_REXMT:
 618                         t_callout = &tp->t_timers->tt_rexmt;
 619                         f_callout = tcp_timer_rexmt;
 620                         break;
 621                 case TT_PERSIST:
 622                         t_callout = &tp->t_timers->tt_persist;
 623                         f_callout = tcp_timer_persist;
 624                         break;
 625                 case TT_KEEP:
 626                         t_callout = &tp->t_timers->tt_keep;
 627                         f_callout = tcp_timer_keep;
 628                         break;
 629                 case TT_2MSL:
 630                         t_callout = &tp->t_timers->tt_2msl;
 631                         f_callout = tcp_timer_2msl;
 632                         break;
 633                 default:
 634                         panic("bad timer_type");
 635                 }
 636         if (delta == 0) {
 637                 callout_stop(t_callout);
 638         } else {
 639                 callout_reset(t_callout, delta, f_callout, tp);
 640         }
 641 }
 642
 643 int
 644 tcp_timer_active(struct tcpcb *tp, int timer_type)
 645 {
 646         struct callout *t_callout;
 647
 648         switch (timer_type) {
 649                 case TT_DELACK:
 650                         t_callout = &tp->t_timers->tt_delack;
 651                         break;
 652                 case TT_REXMT:
 653                         t_callout = &tp->t_timers->tt_rexmt;
 654                         break;
 655                 case TT_PERSIST:
 656                         t_callout = &tp->t_timers->tt_persist;
 657                         break;
 658                 case TT_KEEP:
 659                         t_callout = &tp->t_timers->tt_keep;
 660                         break;
 661                 case TT_2MSL:
 662                         t_callout = &tp->t_timers->tt_2msl;
 663                         break;
 664                 default:
 665                         panic("bad timer_type");
 666                 }
 667         return callout_active(t_callout);
 668 }