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 #include "opt_inet.h"
  36 #include "opt_inet6.h"
  37 #include "opt_rss.h"
  38
  39 #include <sys/param.h>
  40 #include <sys/kernel.h>
  41 #include <sys/lock.h>
  42 #include <sys/mbuf.h>
  43 #include <sys/mutex.h>
  44 #include <sys/protosw.h>
  45 #include <sys/smp.h>
  46 #include <sys/socket.h>
  47 #include <sys/socketvar.h>
  48 #include <sys/sysctl.h>
  49 #include <sys/systm.h>
  50
  51 #include <net/if.h>
  52 #include <net/route.h>
  53 #include <net/rss_config.h>
  54 #include <net/vnet.h>
  55 #include <net/netisr.h>
  56
  57 #include <netinet/in.h>
  58 #include <netinet/in_kdtrace.h>
  59 #include <netinet/in_pcb.h>
  60 #include <netinet/in_rss.h>
  61 #include <netinet/in_systm.h>
  62 #ifdef INET6
  63 #include <netinet6/in6_pcb.h>
  64 #endif
  65 #include <netinet/ip_var.h>
  66 #include <netinet/tcp.h>
  67 #include <netinet/tcp_fsm.h>
  68 #include <netinet/tcp_timer.h>
  69 #include <netinet/tcp_var.h>
  70 #include <netinet/tcp_log_buf.h>
  71 #include <netinet/tcp_seq.h>
  72 #include <netinet/cc/cc.h>
  73 #ifdef INET6
  74 #include <netinet6/tcp6_var.h>
  75 #endif
  76 #include <netinet/tcpip.h>
  77
  78 int    tcp_persmin;
  79 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin,
  80     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
  81     &tcp_persmin, 0, sysctl_msec_to_ticks, "I",
  82     "minimum persistence interval");
  83
  84 int    tcp_persmax;
  85 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax,
  86     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
  87     &tcp_persmax, 0, sysctl_msec_to_ticks, "I",
  88     "maximum persistence interval");
  89
  90 int     tcp_keepinit;
  91 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,
  92     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
  93     &tcp_keepinit, 0, sysctl_msec_to_ticks, "I",
  94     "time to establish connection");
  95
  96 int     tcp_keepidle;
  97 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,
  98     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
  99     &tcp_keepidle, 0, sysctl_msec_to_ticks, "I",
 100     "time before keepalive probes begin");
 101
 102 int     tcp_keepintvl;
 103 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,
 104     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
 105     &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I",
 106     "time between keepalive probes");
 107
 108 int     tcp_delacktime;
 109 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
 110     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
 111     &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
 112     "Time before a delayed ACK is sent");
 113
 114 VNET_DEFINE(int, tcp_msl);
 115 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl,
 116     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_VNET,
 117     &VNET_NAME(tcp_msl), 0, sysctl_msec_to_ticks, "I",
 118     "Maximum segment lifetime");
 119
 120 int     tcp_rexmit_initial;
 121 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial,
 122    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
 123     &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
 124     "Initial Retransmission Timeout");
 125
 126 int     tcp_rexmit_min;
 127 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min,
 128     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
 129     &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
 130     "Minimum Retransmission Timeout");
 131
 132 int     tcp_rexmit_slop;
 133 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop,
 134     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
 135     &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
 136     "Retransmission Timer Slop");
 137
 138 VNET_DEFINE(int, tcp_always_keepalive) = 1;
 139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW,
 140     &VNET_NAME(tcp_always_keepalive) , 0,
 141     "Assume SO_KEEPALIVE on all TCP connections");
 142
 143 int    tcp_fast_finwait2_recycle = 0;
 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
 145     &tcp_fast_finwait2_recycle, 0,
 146     "Recycle closed FIN_WAIT_2 connections faster");
 147
 148 int    tcp_finwait2_timeout;
 149 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout,
 150     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
 151     &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I",
 152     "FIN-WAIT2 timeout");
 153
 154 int     tcp_keepcnt = TCPTV_KEEPCNT;
 155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
 156     "Number of keepalive probes to send");
 157
 158         /* max idle probes */
 159 int     tcp_maxpersistidle;
 160
 161 int     tcp_rexmit_drop_options = 0;
 162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
 163     &tcp_rexmit_drop_options, 0,
 164     "Drop TCP options from 3rd and later retransmitted SYN");
 165
 166 int     tcp_maxunacktime = TCPTV_MAXUNACKTIME;
 167 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxunacktime,
 168     CTLTYPE_INT|CTLFLAG_RW | CTLFLAG_NEEDGIANT,
 169     &tcp_maxunacktime, 0, sysctl_msec_to_ticks, "I",
 170     "Maximum time (in ms) that a session can linger without making progress");
 171
 172 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
 174     CTLFLAG_RW|CTLFLAG_VNET,
 175     &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
 176     "Path MTU Discovery Black Hole Detection Enabled");
 177
 178 #ifdef INET
 179 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
 181     CTLFLAG_RW|CTLFLAG_VNET,
 182     &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
 183     "Path MTU Discovery Black Hole Detection lowered MSS");
 184 #endif
 185
 186 #ifdef INET6
 187 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
 188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
 189     CTLFLAG_RW|CTLFLAG_VNET,
 190     &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
 191     "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
 192 #endif
 193
 194 #ifdef  RSS
 195 static int      per_cpu_timers = 1;
 196 #else
 197 static int      per_cpu_timers = 0;
 198 #endif
 199 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
 200     &per_cpu_timers , 0, "run tcp timers on all cpus");
 201
 202 static int
 203 sysctl_net_inet_tcp_retries(SYSCTL_HANDLER_ARGS)
 204 {
 205         int error, new;
 206
 207         new = V_tcp_retries;
 208         error = sysctl_handle_int(oidp, &new, 0, req);
 209         if (error == 0 && req->newptr) {
 210                 if ((new < 1) || (new > TCP_MAXRXTSHIFT))
 211                         error = EINVAL;
 212                 else
 213                         V_tcp_retries = new;
 214         }
 215         return (error);
 216 }
 217
 218 VNET_DEFINE(int, tcp_retries) = TCP_MAXRXTSHIFT;
 219 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, retries,
 220     CTLTYPE_INT | CTLFLAG_VNET | CTLFLAG_RW,
 221     &VNET_NAME(tcp_retries), 0, sysctl_net_inet_tcp_retries, "I",
 222     "maximum number of consecutive timer based retransmissions");
 223
 224 /*
 225  * Map the given inp to a CPU id.
 226  *
 227  * This queries RSS if it's compiled in, else it defaults to the current
 228  * CPU ID.
 229  */
 230 inline int
 231 inp_to_cpuid(struct inpcb *inp)
 232 {
 233         u_int cpuid;
 234
 235         if (per_cpu_timers) {
 236 #ifdef  RSS
 237                 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
 238                 if (cpuid == NETISR_CPUID_NONE)
 239                         return (curcpu);        /* XXX */
 240                 else
 241                         return (cpuid);
 242 #endif
 243                 /*
 244                  * We don't have a flowid -> cpuid mapping, so cheat and
 245                  * just map unknown cpuids to curcpu.  Not the best, but
 246                  * apparently better than defaulting to swi 0.
 247                  */
 248                 cpuid = inp->inp_flowid % (mp_maxid + 1);
 249                 if (! CPU_ABSENT(cpuid))
 250                         return (cpuid);
 251                 return (curcpu);
 252         } else {
 253                 return (0);
 254         }
 255 }
 256
 257 int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
 258     { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
 259
 260 int tcp_totbackoff = 2559;      /* sum of tcp_backoff[] */
 261
 262 /*
 263  * TCP timer processing.
 264  *
 265  * Each connection has 5 timers associated with it, which can be scheduled
 266  * simultaneously.  They all are serviced by one callout tcp_timer_enter().
 267  * This function executes the next timer via tcp_timersw[] vector.  Each
 268  * timer is supposed to return 'true' unless the connection was destroyed.
 269  * In the former case tcp_timer_enter() will schedule callout for next timer.
 270  */
 271
 272 typedef bool tcp_timer_t(struct tcpcb *);
 273 static tcp_timer_t tcp_timer_delack;
 274 static tcp_timer_t tcp_timer_2msl;
 275 static tcp_timer_t tcp_timer_keep;
 276 static tcp_timer_t tcp_timer_persist;
 277 static tcp_timer_t tcp_timer_rexmt;
 278
 279 static tcp_timer_t * const tcp_timersw[TT_N] = {
 280         [TT_DELACK] = tcp_timer_delack,
 281         [TT_REXMT] = tcp_timer_rexmt,
 282         [TT_PERSIST] = tcp_timer_persist,
 283         [TT_KEEP] = tcp_timer_keep,
 284         [TT_2MSL] = tcp_timer_2msl,
 285 };
 286
 287 /*
 288  * tcp_output_locked() s a timer specific variation of call to tcp_output(),
 289  * see tcp_var.h for the rest.  It handles drop request from advanced stacks,
 290  * but keeps tcpcb locked unless tcp_drop() destroyed it.
 291  * Returns true if tcpcb is valid and locked.
 292  */
 293 static inline bool
 294 tcp_output_locked(struct tcpcb *tp)
 295 {
 296         int rv;
 297
 298         INP_WLOCK_ASSERT(tptoinpcb(tp));
 299
 300         if ((rv = tp->t_fb->tfb_tcp_output(tp)) < 0) {
 301                 KASSERT(tp->t_fb->tfb_flags & TCP_FUNC_OUTPUT_CANDROP,
 302                     ("TCP stack %s requested tcp_drop(%p)",
 303                     tp->t_fb->tfb_tcp_block_name, tp));
 304                 tp = tcp_drop(tp, rv);
 305         }
 306
 307         return (tp != NULL);
 308 }
 309
 310 static bool
 311 tcp_timer_delack(struct tcpcb *tp)
 312 {
 313         struct epoch_tracker et;
 314 #if defined(INVARIANTS) || defined(VIMAGE)
 315         struct inpcb *inp = tptoinpcb(tp);
 316 #endif
 317         bool rv;
 318
 319         INP_WLOCK_ASSERT(inp);
 320
 321         CURVNET_SET(inp->inp_vnet);
 322         tp->t_flags |= TF_ACKNOW;
 323         TCPSTAT_INC(tcps_delack);
 324         NET_EPOCH_ENTER(et);
 325         rv = tcp_output_locked(tp);
 326         NET_EPOCH_EXIT(et);
 327         CURVNET_RESTORE();
 328
 329         return (rv);
 330 }
 331
 332 static bool
 333 tcp_timer_2msl(struct tcpcb *tp)
 334 {
 335         struct inpcb *inp = tptoinpcb(tp);
 336         bool close = false;
 337
 338         INP_WLOCK_ASSERT(inp);
 339
 340         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 341         CURVNET_SET(inp->inp_vnet);
 342         tcp_log_end_status(tp, TCP_EI_STATUS_2MSL);
 343         tcp_free_sackholes(tp);
 344         /*
 345          * 2 MSL timeout in shutdown went off.  If we're closed but
 346          * still waiting for peer to close and connection has been idle
 347          * too long delete connection control block.  Otherwise, check
 348          * again in a bit.
 349          *
 350          * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
 351          * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
 352          * Ignore fact that there were recent incoming segments.
 353          *
 354          * XXXGL: check if inp_socket shall always be !NULL here?
 355          */
 356         if (tp->t_state == TCPS_TIME_WAIT) {
 357                 close = true;
 358         } else if (tp->t_state == TCPS_FIN_WAIT_2 &&
 359             tcp_fast_finwait2_recycle && inp->inp_socket &&
 360             (inp->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
 361                 TCPSTAT_INC(tcps_finwait2_drops);
 362                 close = true;
 363         } else {
 364                 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp))
 365                         tcp_timer_activate(tp, TT_2MSL, TP_KEEPINTVL(tp));
 366                 else
 367                         close = true;
 368         }
 369         if (close) {
 370                 struct epoch_tracker et;
 371
 372                 NET_EPOCH_ENTER(et);
 373                 tp = tcp_close(tp);
 374                 NET_EPOCH_EXIT(et);
 375         }
 376         CURVNET_RESTORE();
 377
 378         return (tp != NULL);
 379 }
 380
 381 static bool
 382 tcp_timer_keep(struct tcpcb *tp)
 383 {
 384         struct epoch_tracker et;
 385         struct inpcb *inp = tptoinpcb(tp);
 386         struct tcptemp *t_template;
 387
 388         INP_WLOCK_ASSERT(inp);
 389
 390         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 391         CURVNET_SET(inp->inp_vnet);
 392         /*
 393          * Because we don't regularly reset the keepalive callout in
 394          * the ESTABLISHED state, it may be that we don't actually need
 395          * to send a keepalive yet. If that occurs, schedule another
 396          * call for the next time the keepalive timer might expire.
 397          */
 398         if (TCPS_HAVEESTABLISHED(tp->t_state)) {
 399                 u_int idletime;
 400
 401                 idletime = ticks - tp->t_rcvtime;
 402                 if (idletime < TP_KEEPIDLE(tp)) {
 403                         tcp_timer_activate(tp, TT_KEEP,
 404                             TP_KEEPIDLE(tp) - idletime);
 405                         CURVNET_RESTORE();
 406                         return (true);
 407                 }
 408         }
 409
 410         /*
 411          * Keep-alive timer went off; send something
 412          * or drop connection if idle for too long.
 413          */
 414         TCPSTAT_INC(tcps_keeptimeo);
 415         if (tp->t_state < TCPS_ESTABLISHED)
 416                 goto dropit;
 417         if ((V_tcp_always_keepalive ||
 418             inp->inp_socket->so_options & SO_KEEPALIVE) &&
 419             tp->t_state <= TCPS_CLOSING) {
 420                 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
 421                         goto dropit;
 422                 /*
 423                  * Send a packet designed to force a response
 424                  * if the peer is up and reachable:
 425                  * either an ACK if the connection is still alive,
 426                  * or an RST if the peer has closed the connection
 427                  * due to timeout or reboot.
 428                  * Using sequence number tp->snd_una-1
 429                  * causes the transmitted zero-length segment
 430                  * to lie outside the receive window;
 431                  * by the protocol spec, this requires the
 432                  * correspondent TCP to respond.
 433                  */
 434                 TCPSTAT_INC(tcps_keepprobe);
 435                 t_template = tcpip_maketemplate(inp);
 436                 if (t_template) {
 437                         NET_EPOCH_ENTER(et);
 438                         tcp_respond(tp, t_template->tt_ipgen,
 439                                     &t_template->tt_t, (struct mbuf *)NULL,
 440                                     tp->rcv_nxt, tp->snd_una - 1, 0);
 441                         NET_EPOCH_EXIT(et);
 442                         free(t_template, M_TEMP);
 443                 }
 444                 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINTVL(tp));
 445         } else
 446                 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
 447
 448         CURVNET_RESTORE();
 449         return (true);
 450
 451 dropit:
 452         TCPSTAT_INC(tcps_keepdrops);
 453         NET_EPOCH_ENTER(et);
 454         tcp_log_end_status(tp, TCP_EI_STATUS_KEEP_MAX);
 455         tp = tcp_drop(tp, ETIMEDOUT);
 456         NET_EPOCH_EXIT(et);
 457         CURVNET_RESTORE();
 458
 459         return (tp != NULL);
 460 }
 461
 462 /*
 463  * Has this session exceeded the maximum time without seeing a substantive
 464  * acknowledgement? If so, return true; otherwise false.
 465  */
 466 static bool
 467 tcp_maxunacktime_check(struct tcpcb *tp)
 468 {
 469
 470         /* Are we tracking this timer for this session? */
 471         if (TP_MAXUNACKTIME(tp) == 0)
 472                 return false;
 473
 474         /* Do we have a current measurement. */
 475         if (tp->t_acktime == 0)
 476                 return false;
 477
 478         /* Are we within the acceptable range? */
 479         if (TSTMP_GT(TP_MAXUNACKTIME(tp) + tp->t_acktime, (u_int)ticks))
 480                 return false;
 481
 482         /* We exceeded the timer. */
 483         TCPSTAT_INC(tcps_progdrops);
 484         return true;
 485 }
 486
 487 static bool
 488 tcp_timer_persist(struct tcpcb *tp)
 489 {
 490         struct epoch_tracker et;
 491 #if defined(INVARIANTS) || defined(VIMAGE)
 492         struct inpcb *inp = tptoinpcb(tp);
 493 #endif
 494         bool progdrop, rv;
 495
 496         INP_WLOCK_ASSERT(inp);
 497
 498         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 499         CURVNET_SET(inp->inp_vnet);
 500         /*
 501          * Persistence timer into zero window.
 502          * Force a byte to be output, if possible.
 503          */
 504         TCPSTAT_INC(tcps_persisttimeo);
 505         /*
 506          * Hack: if the peer is dead/unreachable, we do not
 507          * time out if the window is closed.  After a full
 508          * backoff, drop the connection if the idle time
 509          * (no responses to probes) reaches the maximum
 510          * backoff that we would use if retransmitting.
 511          * Also, drop the connection if we haven't been making
 512          * progress.
 513          */
 514         progdrop = tcp_maxunacktime_check(tp);
 515         if (progdrop || (tp->t_rxtshift >= V_tcp_retries &&
 516             (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
 517              ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff))) {
 518                 if (!progdrop)
 519                         TCPSTAT_INC(tcps_persistdrop);
 520                 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX);
 521                 goto dropit;
 522         }
 523         /*
 524          * If the user has closed the socket then drop a persisting
 525          * connection after a much reduced timeout.
 526          */
 527         if (tp->t_state > TCPS_CLOSE_WAIT &&
 528             (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
 529                 TCPSTAT_INC(tcps_persistdrop);
 530                 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX);
 531                 goto dropit;
 532         }
 533         tcp_setpersist(tp);
 534         tp->t_flags |= TF_FORCEDATA;
 535         NET_EPOCH_ENTER(et);
 536         if ((rv = tcp_output_locked(tp)))
 537                 tp->t_flags &= ~TF_FORCEDATA;
 538         NET_EPOCH_EXIT(et);
 539         CURVNET_RESTORE();
 540
 541         return (rv);
 542
 543 dropit:
 544         NET_EPOCH_ENTER(et);
 545         tp = tcp_drop(tp, ETIMEDOUT);
 546         NET_EPOCH_EXIT(et);
 547         CURVNET_RESTORE();
 548
 549         return (tp != NULL);
 550 }
 551
 552 static bool
 553 tcp_timer_rexmt(struct tcpcb *tp)
 554 {
 555         struct epoch_tracker et;
 556         struct inpcb *inp = tptoinpcb(tp);
 557         int rexmt;
 558         bool isipv6, rv;
 559
 560         INP_WLOCK_ASSERT(inp);
 561
 562         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 563         CURVNET_SET(inp->inp_vnet);
 564         tcp_free_sackholes(tp);
 565         if (tp->t_fb->tfb_tcp_rexmit_tmr) {
 566                 /* The stack has a timer action too. */
 567                 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
 568         }
 569         /*
 570          * Retransmission timer went off.  Message has not
 571          * been acked within retransmit interval.  Back off
 572          * to a longer retransmit interval and retransmit one segment.
 573          *
 574          * If we've either exceeded the maximum number of retransmissions,
 575          * or we've gone long enough without making progress, then drop
 576          * the session.
 577          */
 578         if (++tp->t_rxtshift > V_tcp_retries || tcp_maxunacktime_check(tp)) {
 579                 if (tp->t_rxtshift > V_tcp_retries)
 580                         TCPSTAT_INC(tcps_timeoutdrop);
 581                 tp->t_rxtshift = V_tcp_retries;
 582                 tcp_log_end_status(tp, TCP_EI_STATUS_RETRAN);
 583                 NET_EPOCH_ENTER(et);
 584                 tp = tcp_drop(tp, ETIMEDOUT);
 585                 NET_EPOCH_EXIT(et);
 586                 CURVNET_RESTORE();
 587
 588                 return (tp != NULL);
 589         }
 590         if (tp->t_state == TCPS_SYN_SENT) {
 591                 /*
 592                  * If the SYN was retransmitted, indicate CWND to be
 593                  * limited to 1 segment in cc_conn_init().
 594                  */
 595                 tp->snd_cwnd = 1;
 596         } else if (tp->t_rxtshift == 1) {
 597                 /*
 598                  * first retransmit; record ssthresh and cwnd so they can
 599                  * be recovered if this turns out to be a "bad" retransmit.
 600                  * A retransmit is considered "bad" if an ACK for this
 601                  * segment is received within RTT/2 interval; the assumption
 602                  * here is that the ACK was already in flight.  See
 603                  * "On Estimating End-to-End Network Path Properties" by
 604                  * Allman and Paxson for more details.
 605                  */
 606                 tp->snd_cwnd_prev = tp->snd_cwnd;
 607                 tp->snd_ssthresh_prev = tp->snd_ssthresh;
 608                 tp->snd_recover_prev = tp->snd_recover;
 609                 if (IN_FASTRECOVERY(tp->t_flags))
 610                         tp->t_flags |= TF_WASFRECOVERY;
 611                 else
 612                         tp->t_flags &= ~TF_WASFRECOVERY;
 613                 if (IN_CONGRECOVERY(tp->t_flags))
 614                         tp->t_flags |= TF_WASCRECOVERY;
 615                 else
 616                         tp->t_flags &= ~TF_WASCRECOVERY;
 617                 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
 618                         tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
 619                 /* In the event that we've negotiated timestamps
 620                  * badrxtwin will be set to the value that we set
 621                  * the retransmitted packet's to_tsval to by tcp_output
 622                  */
 623                 tp->t_flags |= TF_PREVVALID;
 624         } else
 625                 tp->t_flags &= ~TF_PREVVALID;
 626         TCPSTAT_INC(tcps_rexmttimeo);
 627         if ((tp->t_state == TCPS_SYN_SENT) ||
 628             (tp->t_state == TCPS_SYN_RECEIVED))
 629                 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
 630         else
 631                 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
 632         TCPT_RANGESET(tp->t_rxtcur, rexmt,
 633                       tp->t_rttmin, TCPTV_REXMTMAX);
 634
 635         /*
 636          * We enter the path for PLMTUD if connection is established or, if
 637          * connection is FIN_WAIT_1 status, reason for the last is that if
 638          * amount of data we send is very small, we could send it in couple of
 639          * packets and process straight to FIN. In that case we won't catch
 640          * ESTABLISHED state.
 641          */
 642 #ifdef INET6
 643         isipv6 = (inp->inp_vflag & INP_IPV6) ? true : false;
 644 #else
 645         isipv6 = false;
 646 #endif
 647         if (((V_tcp_pmtud_blackhole_detect == 1) ||
 648             (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
 649             (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
 650             ((tp->t_state == TCPS_ESTABLISHED) ||
 651             (tp->t_state == TCPS_FIN_WAIT_1))) {
 652                 if (tp->t_rxtshift == 1) {
 653                         /*
 654                          * We enter blackhole detection after the first
 655                          * unsuccessful timer based retransmission.
 656                          * Then we reduce up to two times the MSS, each
 657                          * candidate giving two tries of retransmissions.
 658                          * But we give a candidate only two tries, if it
 659                          * actually reduces the MSS.
 660                          */
 661                         tp->t_blackhole_enter = 2;
 662                         tp->t_blackhole_exit = tp->t_blackhole_enter;
 663                         if (isipv6) {
 664 #ifdef INET6
 665                                 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss)
 666                                         tp->t_blackhole_exit += 2;
 667                                 if (tp->t_maxseg > V_tcp_v6mssdflt &&
 668                                     V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt)
 669                                         tp->t_blackhole_exit += 2;
 670 #endif
 671                         } else {
 672 #ifdef INET
 673                                 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss)
 674                                         tp->t_blackhole_exit += 2;
 675                                 if (tp->t_maxseg > V_tcp_mssdflt &&
 676                                     V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt)
 677                                         tp->t_blackhole_exit += 2;
 678 #endif
 679                         }
 680                 }
 681                 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
 682                     (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
 683                     (tp->t_rxtshift >= tp->t_blackhole_enter &&
 684                     tp->t_rxtshift < tp->t_blackhole_exit &&
 685                     (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) {
 686                         /*
 687                          * Enter Path MTU Black-hole Detection mechanism:
 688                          * - Disable Path MTU Discovery (IP "DF" bit).
 689                          * - Reduce MTU to lower value than what we
 690                          *   negotiated with peer.
 691                          */
 692                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
 693                                 /* Record that we may have found a black hole. */
 694                                 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
 695                                 /* Keep track of previous MSS. */
 696                                 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
 697                         }
 698
 699                         /*
 700                          * Reduce the MSS to blackhole value or to the default
 701                          * in an attempt to retransmit.
 702                          */
 703 #ifdef INET6
 704                         if (isipv6 &&
 705                             tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss &&
 706                             V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) {
 707                                 /* Use the sysctl tuneable blackhole MSS. */
 708                                 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
 709                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
 710                         } else if (isipv6) {
 711                                 /* Use the default MSS. */
 712                                 tp->t_maxseg = V_tcp_v6mssdflt;
 713                                 /*
 714                                  * Disable Path MTU Discovery when we switch to
 715                                  * minmss.
 716                                  */
 717                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
 718                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
 719                         }
 720 #endif
 721 #if defined(INET6) && defined(INET)
 722                         else
 723 #endif
 724 #ifdef INET
 725                         if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss &&
 726                             V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) {
 727                                 /* Use the sysctl tuneable blackhole MSS. */
 728                                 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
 729                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
 730                         } else {
 731                                 /* Use the default MSS. */
 732                                 tp->t_maxseg = V_tcp_mssdflt;
 733                                 /*
 734                                  * Disable Path MTU Discovery when we switch to
 735                                  * minmss.
 736                                  */
 737                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
 738                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
 739                         }
 740 #endif
 741                         /*
 742                          * Reset the slow-start flight size
 743                          * as it may depend on the new MSS.
 744                          */
 745                         if (CC_ALGO(tp)->conn_init != NULL)
 746                                 CC_ALGO(tp)->conn_init(&tp->t_ccv);
 747                 } else {
 748                         /*
 749                          * If further retransmissions are still unsuccessful
 750                          * with a lowered MTU, maybe this isn't a blackhole and
 751                          * we restore the previous MSS and blackhole detection
 752                          * flags.
 753                          */
 754                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
 755                             (tp->t_rxtshift >= tp->t_blackhole_exit)) {
 756                                 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
 757                                 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
 758                                 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
 759                                 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
 760                                 /*
 761                                  * Reset the slow-start flight size as it
 762                                  * may depend on the new MSS.
 763                                  */
 764                                 if (CC_ALGO(tp)->conn_init != NULL)
 765                                         CC_ALGO(tp)->conn_init(&tp->t_ccv);
 766                         }
 767                 }
 768         }
 769
 770         /*
 771          * Disable RFC1323 and SACK if we haven't got any response to
 772          * our third SYN to work-around some broken terminal servers
 773          * (most of which have hopefully been retired) that have bad VJ
 774          * header compression code which trashes TCP segments containing
 775          * unknown-to-them TCP options.
 776          */
 777         if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
 778             (tp->t_rxtshift == 3))
 779                 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
 780         /*
 781          * If we backed off this far, notify the L3 protocol that we're having
 782          * connection problems.
 783          */
 784         if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
 785 #ifdef INET6
 786                 if ((inp->inp_vflag & INP_IPV6) != 0)
 787                         in6_losing(inp);
 788                 else
 789 #endif
 790                         in_losing(inp);
 791         }
 792         tp->snd_nxt = tp->snd_una;
 793         tp->snd_recover = tp->snd_max;
 794         /*
 795          * Force a segment to be sent.
 796          */
 797         tp->t_flags |= TF_ACKNOW;
 798         /*
 799          * If timing a segment in this window, stop the timer.
 800          */
 801         tp->t_rtttime = 0;
 802
 803         cc_cong_signal(tp, NULL, CC_RTO);
 804         NET_EPOCH_ENTER(et);
 805         rv = tcp_output_locked(tp);
 806         NET_EPOCH_EXIT(et);
 807         CURVNET_RESTORE();
 808
 809         return (rv);
 810 }
 811
 812 static void
 813 tcp_bblog_timer(struct tcpcb *tp, tt_which which, tt_what what, uint32_t ticks)
 814 {
 815         struct tcp_log_buffer *lgb;
 816         uint64_t ms;
 817
 818         INP_WLOCK_ASSERT(tptoinpcb(tp));
 819         if (tcp_bblogging_on(tp))
 820                 lgb = tcp_log_event(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0,
 821                     NULL, false, NULL, NULL, 0, NULL);
 822         else
 823                 lgb = NULL;
 824         if (lgb != NULL) {
 825                 lgb->tlb_flex1 = (what << 8) | which;
 826                 if (what == TT_STARTING) {
 827                         /* Convert ticks to ms and store it in tlb_flex2. */
 828                         if (hz == 1000)
 829                                 lgb->tlb_flex2 = ticks;
 830                         else {
 831                                 ms = (((uint64_t)ticks * 1000) + (hz - 1)) / hz;
 832                                 if (ms > UINT32_MAX)
 833                                         lgb->tlb_flex2 = UINT32_MAX;
 834                                 else
 835                                         lgb->tlb_flex2 = (uint32_t)ms;
 836                         }
 837                 }
 838         }
 839 }
 840
 841 static inline tt_which
 842 tcp_timer_next(struct tcpcb *tp, sbintime_t *precision)
 843 {
 844         tt_which i, rv;
 845         sbintime_t after, before;
 846
 847         for (i = 0, rv = TT_N, after = before = SBT_MAX; i < TT_N; i++) {
 848                 if (tp->t_timers[i] < after) {
 849                         after = tp->t_timers[i];
 850                         rv = i;
 851                 }
 852                 before = MIN(before, tp->t_timers[i] + tp->t_precisions[i]);
 853         }
 854         if (precision != NULL)
 855                 *precision = before - after;
 856
 857         return (rv);
 858 }
 859
 860 static void
 861 tcp_timer_enter(void *xtp)
 862 {
 863         struct tcpcb *tp = xtp;
 864         struct inpcb *inp = tptoinpcb(tp);
 865         sbintime_t precision;
 866         tt_which which;
 867         bool tp_valid;
 868
 869         INP_WLOCK_ASSERT(inp);
 870         MPASS((curthread->td_pflags & TDP_INTCPCALLOUT) == 0);
 871
 872         curthread->td_pflags |= TDP_INTCPCALLOUT;
 873
 874         which = tcp_timer_next(tp, NULL);
 875         MPASS(which < TT_N);
 876         tp->t_timers[which] = SBT_MAX;
 877         tp->t_precisions[which] = 0;
 878
 879         tcp_bblog_timer(tp, which, TT_PROCESSING, 0);
 880         tp_valid = tcp_timersw[which](tp);
 881         if (tp_valid) {
 882                 tcp_bblog_timer(tp, which, TT_PROCESSED, 0);
 883                 if ((which = tcp_timer_next(tp, &precision)) != TT_N) {
 884                         callout_reset_sbt_on(&tp->t_callout,
 885                             tp->t_timers[which], precision, tcp_timer_enter,
 886                             tp, inp_to_cpuid(inp), C_ABSOLUTE);
 887                 }
 888                 INP_WUNLOCK(inp);
 889         }
 890
 891         curthread->td_pflags &= ~TDP_INTCPCALLOUT;
 892 }
 893
 894 /*
 895  * Activate or stop (delta == 0) a TCP timer.
 896  */
 897 void
 898 tcp_timer_activate(struct tcpcb *tp, tt_which which, u_int delta)
 899 {
 900         struct inpcb *inp = tptoinpcb(tp);
 901         sbintime_t precision;
 902         tt_what what;
 903
 904 #ifdef TCP_OFFLOAD
 905         if (tp->t_flags & TF_TOE)
 906                 return;
 907 #endif
 908
 909         INP_WLOCK_ASSERT(inp);
 910
 911         if (delta > 0) {
 912                 what = TT_STARTING;
 913                 callout_when(tick_sbt * delta, 0, C_HARDCLOCK,
 914                     &tp->t_timers[which], &tp->t_precisions[which]);
 915         } else {
 916                 what = TT_STOPPING;
 917                 tp->t_timers[which] = SBT_MAX;
 918         }
 919         tcp_bblog_timer(tp, which, what, delta);
 920
 921         if ((which = tcp_timer_next(tp, &precision)) != TT_N)
 922                 callout_reset_sbt_on(&tp->t_callout, tp->t_timers[which],
 923                     precision, tcp_timer_enter, tp, inp_to_cpuid(inp),
 924                     C_ABSOLUTE);
 925         else
 926                 callout_stop(&tp->t_callout);
 927 }
 928
 929 bool
 930 tcp_timer_active(struct tcpcb *tp, tt_which which)
 931 {
 932
 933         INP_WLOCK_ASSERT(tptoinpcb(tp));
 934
 935         return (tp->t_timers[which] != SBT_MAX);
 936 }
 937
 938 /*
 939  * Stop all timers associated with tcpcb.
 940  *
 941  * Called only on tcpcb destruction.  The tcpcb shall already be dropped from
 942  * the pcb lookup database and socket is not losing the last reference.
 943  *
 944  * XXXGL: unfortunately our callout(9) is not able to fully stop a locked
 945  * callout even when only two threads are involved: the callout itself and the
 946  * thread that does callout_stop().  See where softclock_call_cc() swaps the
 947  * callwheel lock to callout lock and then checks cc_exec_cancel().  This is
 948  * the race window.  If it happens, the tcp_timer_enter() won't be executed,
 949  * however pcb lock will be locked and released, hence we can't free memory.
 950  * Until callout(9) is improved, just keep retrying.  In my profiling I've seen
 951  * such event happening less than 1 time per hour with 20-30 Gbit/s of traffic.
 952  */
 953 void
 954 tcp_timer_stop(struct tcpcb *tp)
 955 {
 956         struct inpcb *inp = tptoinpcb(tp);
 957
 958         INP_WLOCK_ASSERT(inp);
 959
 960         if (curthread->td_pflags & TDP_INTCPCALLOUT) {
 961                 int stopped __diagused;
 962
 963                 stopped = callout_stop(&tp->t_callout);
 964                 MPASS(stopped == 0);
 965         } else while(__predict_false(callout_stop(&tp->t_callout) == 0)) {
 966                 INP_WUNLOCK(inp);
 967                 kern_yield(PRI_UNCHANGED);
 968                 INP_WLOCK(inp);
 969         }
 970 }