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/cc/cc.h>
  75 #ifdef INET6
  76 #include <netinet6/tcp6_var.h>
  77 #endif
  78 #include <netinet/tcpip.h>
  79 #ifdef TCPDEBUG
  80 #include <netinet/tcp_debug.h>
  81 #endif
  82
  83 int    tcp_persmin;
  84 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
  85     &tcp_persmin, 0, sysctl_msec_to_ticks, "I", "minimum persistence interval");
  86
  87 int    tcp_persmax;
  88 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
  89     &tcp_persmax, 0, sysctl_msec_to_ticks, "I", "maximum persistence interval");
  90
  91 int     tcp_keepinit;
  92 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
  93     &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
  94
  95 int     tcp_keepidle;
  96 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
  97     &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
  98
  99 int     tcp_keepintvl;
 100 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
 101     &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
 102
 103 int     tcp_delacktime;
 104 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
 105     &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
 106     "Time before a delayed ACK is sent");
 107
 108 int     tcp_msl;
 109 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
 110     &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
 111
 112 int     tcp_rexmit_min;
 113 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
 114     &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
 115     "Minimum Retransmission Timeout");
 116
 117 int     tcp_rexmit_slop;
 118 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
 119     &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
 120     "Retransmission Timer Slop");
 121
 122 int     tcp_always_keepalive = 1;
 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
 124     &tcp_always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
 125
 126 int    tcp_fast_finwait2_recycle = 0;
 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
 128     &tcp_fast_finwait2_recycle, 0,
 129     "Recycle closed FIN_WAIT_2 connections faster");
 130
 131 int    tcp_finwait2_timeout;
 132 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
 133     &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
 134
 135 int     tcp_keepcnt = TCPTV_KEEPCNT;
 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
 137     "Number of keepalive probes to send");
 138
 139         /* max idle probes */
 140 int     tcp_maxpersistidle;
 141
 142 static int      tcp_rexmit_drop_options = 0;
 143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
 144     &tcp_rexmit_drop_options, 0,
 145     "Drop TCP options from 3rd and later retransmitted SYN");
 146
 147 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
 149     CTLFLAG_RW|CTLFLAG_VNET,
 150     &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
 151     "Path MTU Discovery Black Hole Detection Enabled");
 152
 153 #ifdef INET
 154 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
 155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
 156     CTLFLAG_RW|CTLFLAG_VNET,
 157     &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
 158     "Path MTU Discovery Black Hole Detection lowered MSS");
 159 #endif
 160
 161 #ifdef INET6
 162 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
 164     CTLFLAG_RW|CTLFLAG_VNET,
 165     &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
 166     "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
 167 #endif
 168
 169 #ifdef  RSS
 170 static int      per_cpu_timers = 1;
 171 #else
 172 static int      per_cpu_timers = 0;
 173 #endif
 174 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
 175     &per_cpu_timers , 0, "run tcp timers on all cpus");
 176
 177 #if 0
 178 #define INP_CPU(inp)    (per_cpu_timers ? (!CPU_ABSENT(((inp)->inp_flowid % (mp_maxid+1))) ? \
 179                 ((inp)->inp_flowid % (mp_maxid+1)) : curcpu) : 0)
 180 #endif
 181
 182 /*
 183  * Map the given inp to a CPU id.
 184  *
 185  * This queries RSS if it's compiled in, else it defaults to the current
 186  * CPU ID.
 187  */
 188 static inline int
 189 inp_to_cpuid(struct inpcb *inp)
 190 {
 191         u_int cpuid;
 192
 193 #ifdef  RSS
 194         if (per_cpu_timers) {
 195                 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
 196                 if (cpuid == NETISR_CPUID_NONE)
 197                         return (curcpu);        /* XXX */
 198                 else
 199                         return (cpuid);
 200         }
 201 #else
 202         /* Legacy, pre-RSS behaviour */
 203         if (per_cpu_timers) {
 204                 /*
 205                  * We don't have a flowid -> cpuid mapping, so cheat and
 206                  * just map unknown cpuids to curcpu.  Not the best, but
 207                  * apparently better than defaulting to swi 0.
 208                  */
 209                 cpuid = inp->inp_flowid % (mp_maxid + 1);
 210                 if (! CPU_ABSENT(cpuid))
 211                         return (cpuid);
 212                 return (curcpu);
 213         }
 214 #endif
 215         /* Default for RSS and non-RSS - cpuid 0 */
 216         else {
 217                 return (0);
 218         }
 219 }
 220
 221 /*
 222  * Tcp protocol timeout routine called every 500 ms.
 223  * Updates timestamps used for TCP
 224  * causes finite state machine actions if timers expire.
 225  */
 226 void
 227 tcp_slowtimo(void)
 228 {
 229         VNET_ITERATOR_DECL(vnet_iter);
 230
 231         VNET_LIST_RLOCK_NOSLEEP();
 232         VNET_FOREACH(vnet_iter) {
 233                 CURVNET_SET(vnet_iter);
 234                 (void) tcp_tw_2msl_scan(0);
 235                 CURVNET_RESTORE();
 236         }
 237         VNET_LIST_RUNLOCK_NOSLEEP();
 238 }
 239
 240 int     tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
 241     { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
 242
 243 int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
 244     { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
 245
 246 static int tcp_totbackoff = 2559;       /* sum of tcp_backoff[] */
 247
 248 /*
 249  * TCP timer processing.
 250  */
 251
 252 void
 253 tcp_timer_delack(void *xtp)
 254 {
 255         struct tcpcb *tp = xtp;
 256         struct inpcb *inp;
 257         CURVNET_SET(tp->t_vnet);
 258
 259         inp = tp->t_inpcb;
 260         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 261         INP_WLOCK(inp);
 262         if (callout_pending(&tp->t_timers->tt_delack) ||
 263             !callout_active(&tp->t_timers->tt_delack)) {
 264                 INP_WUNLOCK(inp);
 265                 CURVNET_RESTORE();
 266                 return;
 267         }
 268         callout_deactivate(&tp->t_timers->tt_delack);
 269         if ((inp->inp_flags & INP_DROPPED) != 0) {
 270                 INP_WUNLOCK(inp);
 271                 CURVNET_RESTORE();
 272                 return;
 273         }
 274         tp->t_flags |= TF_ACKNOW;
 275         TCPSTAT_INC(tcps_delack);
 276         (void) tp->t_fb->tfb_tcp_output(tp);
 277         INP_WUNLOCK(inp);
 278         CURVNET_RESTORE();
 279 }
 280
 281 /*
 282  * When a timer wants to remove a TCB it must
 283  * hold the INP_INFO_RLOCK(). The timer function
 284  * should only have grabbed the INP_WLOCK() when
 285  * it entered. To safely switch to holding both the
 286  * INP_INFO_RLOCK() and the INP_WLOCK() we must first
 287  * grab a reference on the inp, which will hold the inp
 288  * so that it can't be removed. We then unlock the INP_WLOCK(),
 289  * and grab the INP_INFO_RLOCK() lock. Once we have the INP_INFO_RLOCK()
 290  * we proceed again to get the INP_WLOCK() (this preserves proper
 291  * lock order). After acquiring the INP_WLOCK we must check if someone
 292  * else deleted the pcb i.e. the inp_flags check.
 293  * If so we return 1 otherwise we return 0.
 294  *
 295  * No matter what the tcp_inpinfo_lock_add() function
 296  * returns the caller must afterwards call tcp_inpinfo_lock_del()
 297  * to drop the locks and reference properly.
 298  */
 299
 300 int
 301 tcp_inpinfo_lock_add(struct inpcb *inp)
 302 {
 303         in_pcbref(inp);
 304         INP_WUNLOCK(inp);
 305         INP_INFO_RLOCK(&V_tcbinfo);
 306         INP_WLOCK(inp);
 307         if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
 308                 return(1);
 309         }
 310         return(0);
 311
 312 }
 313
 314 void
 315 tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
 316 {
 317         INP_INFO_RUNLOCK(&V_tcbinfo);
 318         if (inp && (tp == NULL)) {
 319                 /*
 320                  * If tcp_close/drop() gets called and tp
 321                  * returns NULL, then the function dropped
 322                  * the inp lock, we hold a reference keeping
 323                  * this around, so we must re-aquire the
 324                  * INP_WLOCK() in order to proceed with
 325                  * our dropping the inp reference.
 326                  */
 327                 INP_WLOCK(inp);
 328         }
 329         if (inp && in_pcbrele_wlocked(inp) == 0)
 330                 INP_WUNLOCK(inp);
 331 }
 332
 333 void
 334 tcp_timer_2msl(void *xtp)
 335 {
 336         struct tcpcb *tp = xtp;
 337         struct inpcb *inp;
 338         CURVNET_SET(tp->t_vnet);
 339 #ifdef TCPDEBUG
 340         int ostate;
 341
 342         ostate = tp->t_state;
 343 #endif
 344         inp = tp->t_inpcb;
 345         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 346         INP_WLOCK(inp);
 347         tcp_free_sackholes(tp);
 348         if (callout_pending(&tp->t_timers->tt_2msl) ||
 349             !callout_active(&tp->t_timers->tt_2msl)) {
 350                 INP_WUNLOCK(tp->t_inpcb);
 351                 CURVNET_RESTORE();
 352                 return;
 353         }
 354         callout_deactivate(&tp->t_timers->tt_2msl);
 355         if ((inp->inp_flags & INP_DROPPED) != 0) {
 356                 INP_WUNLOCK(inp);
 357                 CURVNET_RESTORE();
 358                 return;
 359         }
 360         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
 361                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 362         /*
 363          * 2 MSL timeout in shutdown went off.  If we're closed but
 364          * still waiting for peer to close and connection has been idle
 365          * too long delete connection control block.  Otherwise, check
 366          * again in a bit.
 367          *
 368          * If in TIME_WAIT state just ignore as this timeout is handled in
 369          * tcp_tw_2msl_scan().
 370          *
 371          * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
 372          * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
 373          * Ignore fact that there were recent incoming segments.
 374          */
 375         if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
 376                 INP_WUNLOCK(inp);
 377                 CURVNET_RESTORE();
 378                 return;
 379         }
 380         if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
 381             tp->t_inpcb && tp->t_inpcb->inp_socket &&
 382             (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
 383                 TCPSTAT_INC(tcps_finwait2_drops);
 384                 if (tcp_inpinfo_lock_add(inp)) {
 385                         tcp_inpinfo_lock_del(inp, tp);
 386                         goto out;
 387                 }
 388                 tp = tcp_close(tp);
 389                 tcp_inpinfo_lock_del(inp, tp);
 390                 goto out;
 391         } else {
 392                 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
 393                         callout_reset(&tp->t_timers->tt_2msl,
 394                                       TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
 395                 } else {
 396                         if (tcp_inpinfo_lock_add(inp)) {
 397                                 tcp_inpinfo_lock_del(inp, tp);
 398                                 goto out;
 399                         }
 400                         tp = tcp_close(tp);
 401                         tcp_inpinfo_lock_del(inp, tp);
 402                         goto out;
 403                 }
 404        }
 405
 406 #ifdef TCPDEBUG
 407         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 408                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 409                           PRU_SLOWTIMO);
 410 #endif
 411         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 412
 413         if (tp != NULL)
 414                 INP_WUNLOCK(inp);
 415 out:
 416         CURVNET_RESTORE();
 417 }
 418
 419 void
 420 tcp_timer_keep(void *xtp)
 421 {
 422         struct tcpcb *tp = xtp;
 423         struct tcptemp *t_template;
 424         struct inpcb *inp;
 425         CURVNET_SET(tp->t_vnet);
 426 #ifdef TCPDEBUG
 427         int ostate;
 428
 429         ostate = tp->t_state;
 430 #endif
 431         inp = tp->t_inpcb;
 432         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 433         INP_WLOCK(inp);
 434         if (callout_pending(&tp->t_timers->tt_keep) ||
 435             !callout_active(&tp->t_timers->tt_keep)) {
 436                 INP_WUNLOCK(inp);
 437                 CURVNET_RESTORE();
 438                 return;
 439         }
 440         callout_deactivate(&tp->t_timers->tt_keep);
 441         if ((inp->inp_flags & INP_DROPPED) != 0) {
 442                 INP_WUNLOCK(inp);
 443                 CURVNET_RESTORE();
 444                 return;
 445         }
 446         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
 447                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 448
 449         /*
 450          * Because we don't regularly reset the keepalive callout in
 451          * the ESTABLISHED state, it may be that we don't actually need
 452          * to send a keepalive yet. If that occurs, schedule another
 453          * call for the next time the keepalive timer might expire.
 454          */
 455         if (TCPS_HAVEESTABLISHED(tp->t_state)) {
 456                 u_int idletime;
 457
 458                 idletime = ticks - tp->t_rcvtime;
 459                 if (idletime < TP_KEEPIDLE(tp)) {
 460                         callout_reset(&tp->t_timers->tt_keep,
 461                             TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
 462                         INP_WUNLOCK(inp);
 463                         CURVNET_RESTORE();
 464                         return;
 465                 }
 466         }
 467
 468         /*
 469          * Keep-alive timer went off; send something
 470          * or drop connection if idle for too long.
 471          */
 472         TCPSTAT_INC(tcps_keeptimeo);
 473         if (tp->t_state < TCPS_ESTABLISHED)
 474                 goto dropit;
 475         if ((tcp_always_keepalive ||
 476             inp->inp_socket->so_options & SO_KEEPALIVE) &&
 477             tp->t_state <= TCPS_CLOSING) {
 478                 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
 479                         goto dropit;
 480                 /*
 481                  * Send a packet designed to force a response
 482                  * if the peer is up and reachable:
 483                  * either an ACK if the connection is still alive,
 484                  * or an RST if the peer has closed the connection
 485                  * due to timeout or reboot.
 486                  * Using sequence number tp->snd_una-1
 487                  * causes the transmitted zero-length segment
 488                  * to lie outside the receive window;
 489                  * by the protocol spec, this requires the
 490                  * correspondent TCP to respond.
 491                  */
 492                 TCPSTAT_INC(tcps_keepprobe);
 493                 t_template = tcpip_maketemplate(inp);
 494                 if (t_template) {
 495                         tcp_respond(tp, t_template->tt_ipgen,
 496                                     &t_template->tt_t, (struct mbuf *)NULL,
 497                                     tp->rcv_nxt, tp->snd_una - 1, 0);
 498                         free(t_template, M_TEMP);
 499                 }
 500                 callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
 501                               tcp_timer_keep, tp);
 502         } else
 503                 callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
 504                               tcp_timer_keep, tp);
 505
 506 #ifdef TCPDEBUG
 507         if (inp->inp_socket->so_options & SO_DEBUG)
 508                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 509                           PRU_SLOWTIMO);
 510 #endif
 511         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 512         INP_WUNLOCK(inp);
 513         CURVNET_RESTORE();
 514         return;
 515
 516 dropit:
 517         TCPSTAT_INC(tcps_keepdrops);
 518
 519         if (tcp_inpinfo_lock_add(inp)) {
 520                 tcp_inpinfo_lock_del(inp, tp);
 521                 goto out;
 522         }
 523         tp = tcp_drop(tp, ETIMEDOUT);
 524
 525 #ifdef TCPDEBUG
 526         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 527                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 528                           PRU_SLOWTIMO);
 529 #endif
 530         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 531         tcp_inpinfo_lock_del(inp, tp);
 532 out:
 533         CURVNET_RESTORE();
 534 }
 535
 536 void
 537 tcp_timer_persist(void *xtp)
 538 {
 539         struct tcpcb *tp = xtp;
 540         struct inpcb *inp;
 541         CURVNET_SET(tp->t_vnet);
 542 #ifdef TCPDEBUG
 543         int ostate;
 544
 545         ostate = tp->t_state;
 546 #endif
 547         inp = tp->t_inpcb;
 548         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 549         INP_WLOCK(inp);
 550         if (callout_pending(&tp->t_timers->tt_persist) ||
 551             !callout_active(&tp->t_timers->tt_persist)) {
 552                 INP_WUNLOCK(inp);
 553                 CURVNET_RESTORE();
 554                 return;
 555         }
 556         callout_deactivate(&tp->t_timers->tt_persist);
 557         if ((inp->inp_flags & INP_DROPPED) != 0) {
 558                 INP_WUNLOCK(inp);
 559                 CURVNET_RESTORE();
 560                 return;
 561         }
 562         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
 563                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 564         /*
 565          * Persistence timer into zero window.
 566          * Force a byte to be output, if possible.
 567          */
 568         TCPSTAT_INC(tcps_persisttimeo);
 569         /*
 570          * Hack: if the peer is dead/unreachable, we do not
 571          * time out if the window is closed.  After a full
 572          * backoff, drop the connection if the idle time
 573          * (no responses to probes) reaches the maximum
 574          * backoff that we would use if retransmitting.
 575          */
 576         if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
 577             (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
 578              ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
 579                 TCPSTAT_INC(tcps_persistdrop);
 580                 if (tcp_inpinfo_lock_add(inp)) {
 581                         tcp_inpinfo_lock_del(inp, tp);
 582                         goto out;
 583                 }
 584                 tp = tcp_drop(tp, ETIMEDOUT);
 585                 tcp_inpinfo_lock_del(inp, tp);
 586                 goto out;
 587         }
 588         /*
 589          * If the user has closed the socket then drop a persisting
 590          * connection after a much reduced timeout.
 591          */
 592         if (tp->t_state > TCPS_CLOSE_WAIT &&
 593             (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
 594                 TCPSTAT_INC(tcps_persistdrop);
 595                 if (tcp_inpinfo_lock_add(inp)) {
 596                         tcp_inpinfo_lock_del(inp, tp);
 597                         goto out;
 598                 }
 599                 tp = tcp_drop(tp, ETIMEDOUT);
 600                 tcp_inpinfo_lock_del(inp, tp);
 601                 goto out;
 602         }
 603         tcp_setpersist(tp);
 604         tp->t_flags |= TF_FORCEDATA;
 605         (void) tp->t_fb->tfb_tcp_output(tp);
 606         tp->t_flags &= ~TF_FORCEDATA;
 607
 608 #ifdef TCPDEBUG
 609         if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
 610                 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
 611 #endif
 612         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 613         INP_WUNLOCK(inp);
 614 out:
 615         CURVNET_RESTORE();
 616 }
 617
 618 void
 619 tcp_timer_rexmt(void * xtp)
 620 {
 621         struct tcpcb *tp = xtp;
 622         CURVNET_SET(tp->t_vnet);
 623         int rexmt;
 624         struct inpcb *inp;
 625 #ifdef TCPDEBUG
 626         int ostate;
 627
 628         ostate = tp->t_state;
 629 #endif
 630         inp = tp->t_inpcb;
 631         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
 632         INP_WLOCK(inp);
 633         if (callout_pending(&tp->t_timers->tt_rexmt) ||
 634             !callout_active(&tp->t_timers->tt_rexmt)) {
 635                 INP_WUNLOCK(inp);
 636                 CURVNET_RESTORE();
 637                 return;
 638         }
 639         callout_deactivate(&tp->t_timers->tt_rexmt);
 640         if ((inp->inp_flags & INP_DROPPED) != 0) {
 641                 INP_WUNLOCK(inp);
 642                 CURVNET_RESTORE();
 643                 return;
 644         }
 645         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
 646                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 647         tcp_free_sackholes(tp);
 648         TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false);
 649         if (tp->t_fb->tfb_tcp_rexmit_tmr) {
 650                 /* The stack has a timer action too. */
 651                 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
 652         }
 653         /*
 654          * Retransmission timer went off.  Message has not
 655          * been acked within retransmit interval.  Back off
 656          * to a longer retransmit interval and retransmit one segment.
 657          */
 658         if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
 659                 tp->t_rxtshift = TCP_MAXRXTSHIFT;
 660                 TCPSTAT_INC(tcps_timeoutdrop);
 661                 if (tcp_inpinfo_lock_add(inp)) {
 662                         tcp_inpinfo_lock_del(inp, tp);
 663                         goto out;
 664                 }
 665                 tp = tcp_drop(tp, ETIMEDOUT);
 666                 tcp_inpinfo_lock_del(inp, tp);
 667                 goto out;
 668         }
 669         if (tp->t_state == TCPS_SYN_SENT) {
 670                 /*
 671                  * If the SYN was retransmitted, indicate CWND to be
 672                  * limited to 1 segment in cc_conn_init().
 673                  */
 674                 tp->snd_cwnd = 1;
 675         } else if (tp->t_rxtshift == 1) {
 676                 /*
 677                  * first retransmit; record ssthresh and cwnd so they can
 678                  * be recovered if this turns out to be a "bad" retransmit.
 679                  * A retransmit is considered "bad" if an ACK for this
 680                  * segment is received within RTT/2 interval; the assumption
 681                  * here is that the ACK was already in flight.  See
 682                  * "On Estimating End-to-End Network Path Properties" by
 683                  * Allman and Paxson for more details.
 684                  */
 685                 tp->snd_cwnd_prev = tp->snd_cwnd;
 686                 tp->snd_ssthresh_prev = tp->snd_ssthresh;
 687                 tp->snd_recover_prev = tp->snd_recover;
 688                 if (IN_FASTRECOVERY(tp->t_flags))
 689                         tp->t_flags |= TF_WASFRECOVERY;
 690                 else
 691                         tp->t_flags &= ~TF_WASFRECOVERY;
 692                 if (IN_CONGRECOVERY(tp->t_flags))
 693                         tp->t_flags |= TF_WASCRECOVERY;
 694                 else
 695                         tp->t_flags &= ~TF_WASCRECOVERY;
 696                 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
 697                         tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
 698                 /* In the event that we've negotiated timestamps
 699                  * badrxtwin will be set to the value that we set
 700                  * the retransmitted packet's to_tsval to by tcp_output
 701                  */
 702                 tp->t_flags |= TF_PREVVALID;
 703         } else
 704                 tp->t_flags &= ~TF_PREVVALID;
 705         TCPSTAT_INC(tcps_rexmttimeo);
 706         if ((tp->t_state == TCPS_SYN_SENT) ||
 707             (tp->t_state == TCPS_SYN_RECEIVED))
 708                 rexmt = TCPTV_RTOBASE * tcp_syn_backoff[tp->t_rxtshift];
 709         else
 710                 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
 711         TCPT_RANGESET(tp->t_rxtcur, rexmt,
 712                       tp->t_rttmin, TCPTV_REXMTMAX);
 713
 714         /*
 715          * We enter the path for PLMTUD if connection is established or, if
 716          * connection is FIN_WAIT_1 status, reason for the last is that if
 717          * amount of data we send is very small, we could send it in couple of
 718          * packets and process straight to FIN. In that case we won't catch
 719          * ESTABLISHED state.
 720          */
 721         if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
 722             || (tp->t_state == TCPS_FIN_WAIT_1))) {
 723 #ifdef INET6
 724                 int isipv6;
 725 #endif
 726
 727                 /*
 728                  * Idea here is that at each stage of mtu probe (usually, 1448
 729                  * -> 1188 -> 524) should be given 2 chances to recover before
 730                  *  further clamping down. 'tp->t_rxtshift % 2 == 0' should
 731                  *  take care of that.
 732                  */
 733                 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
 734                     (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
 735                     (tp->t_rxtshift >= 2 && tp->t_rxtshift < 6 &&
 736                     tp->t_rxtshift % 2 == 0)) {
 737                         /*
 738                          * Enter Path MTU Black-hole Detection mechanism:
 739                          * - Disable Path MTU Discovery (IP "DF" bit).
 740                          * - Reduce MTU to lower value than what we
 741                          *   negotiated with peer.
 742                          */
 743                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
 744                                 /* Record that we may have found a black hole. */
 745                                 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
 746                                 /* Keep track of previous MSS. */
 747                                 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
 748                         }
 749
 750                         /*
 751                          * Reduce the MSS to blackhole value or to the default
 752                          * in an attempt to retransmit.
 753                          */
 754 #ifdef INET6
 755                         isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
 756                         if (isipv6 &&
 757                             tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
 758                                 /* Use the sysctl tuneable blackhole MSS. */
 759                                 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
 760                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
 761                         } else if (isipv6) {
 762                                 /* Use the default MSS. */
 763                                 tp->t_maxseg = V_tcp_v6mssdflt;
 764                                 /*
 765                                  * Disable Path MTU Discovery when we switch to
 766                                  * minmss.
 767                                  */
 768                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
 769                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
 770                         }
 771 #endif
 772 #if defined(INET6) && defined(INET)
 773                         else
 774 #endif
 775 #ifdef INET
 776                         if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) {
 777                                 /* Use the sysctl tuneable blackhole MSS. */
 778                                 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
 779                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
 780                         } else {
 781                                 /* Use the default MSS. */
 782                                 tp->t_maxseg = V_tcp_mssdflt;
 783                                 /*
 784                                  * Disable Path MTU Discovery when we switch to
 785                                  * minmss.
 786                                  */
 787                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
 788                                 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
 789                         }
 790 #endif
 791                         /*
 792                          * Reset the slow-start flight size
 793                          * as it may depend on the new MSS.
 794                          */
 795                         if (CC_ALGO(tp)->conn_init != NULL)
 796                                 CC_ALGO(tp)->conn_init(tp->ccv);
 797                 } else {
 798                         /*
 799                          * If further retransmissions are still unsuccessful
 800                          * with a lowered MTU, maybe this isn't a blackhole and
 801                          * we restore the previous MSS and blackhole detection
 802                          * flags.
 803                          * The limit '6' is determined by giving each probe
 804                          * stage (1448, 1188, 524) 2 chances to recover.
 805                          */
 806                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
 807                             (tp->t_rxtshift >= 6)) {
 808                                 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
 809                                 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
 810                                 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
 811                                 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
 812                                 /*
 813                                  * Reset the slow-start flight size as it
 814                                  * may depend on the new MSS.
 815                                  */
 816                                 if (CC_ALGO(tp)->conn_init != NULL)
 817                                         CC_ALGO(tp)->conn_init(tp->ccv);
 818                         }
 819                 }
 820         }
 821
 822         /*
 823          * Disable RFC1323 and SACK if we haven't got any response to
 824          * our third SYN to work-around some broken terminal servers
 825          * (most of which have hopefully been retired) that have bad VJ
 826          * header compression code which trashes TCP segments containing
 827          * unknown-to-them TCP options.
 828          */
 829         if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
 830             (tp->t_rxtshift == 3))
 831                 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
 832         /*
 833          * If we backed off this far, notify the L3 protocol that we're having
 834          * connection problems.
 835          */
 836         if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
 837 #ifdef INET6
 838                 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
 839                         in6_losing(tp->t_inpcb);
 840                 else
 841 #endif
 842                         in_losing(tp->t_inpcb);
 843         }
 844         tp->snd_nxt = tp->snd_una;
 845         tp->snd_recover = tp->snd_max;
 846         /*
 847          * Force a segment to be sent.
 848          */
 849         tp->t_flags |= TF_ACKNOW;
 850         /*
 851          * If timing a segment in this window, stop the timer.
 852          */
 853         tp->t_rtttime = 0;
 854
 855         cc_cong_signal(tp, NULL, CC_RTO);
 856
 857         (void) tp->t_fb->tfb_tcp_output(tp);
 858
 859 #ifdef TCPDEBUG
 860         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 861                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
 862                           PRU_SLOWTIMO);
 863 #endif
 864         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 865         INP_WUNLOCK(inp);
 866 out:
 867         CURVNET_RESTORE();
 868 }
 869
 870 void
 871 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
 872 {
 873         struct callout *t_callout;
 874         timeout_t *f_callout;
 875         struct inpcb *inp = tp->t_inpcb;
 876         int cpu = inp_to_cpuid(inp);
 877
 878 #ifdef TCP_OFFLOAD
 879         if (tp->t_flags & TF_TOE)
 880                 return;
 881 #endif
 882
 883         if (tp->t_timers->tt_flags & TT_STOPPED)
 884                 return;
 885
 886         switch (timer_type) {
 887                 case TT_DELACK:
 888                         t_callout = &tp->t_timers->tt_delack;
 889                         f_callout = tcp_timer_delack;
 890                         break;
 891                 case TT_REXMT:
 892                         t_callout = &tp->t_timers->tt_rexmt;
 893                         f_callout = tcp_timer_rexmt;
 894                         break;
 895                 case TT_PERSIST:
 896                         t_callout = &tp->t_timers->tt_persist;
 897                         f_callout = tcp_timer_persist;
 898                         break;
 899                 case TT_KEEP:
 900                         t_callout = &tp->t_timers->tt_keep;
 901                         f_callout = tcp_timer_keep;
 902                         break;
 903                 case TT_2MSL:
 904                         t_callout = &tp->t_timers->tt_2msl;
 905                         f_callout = tcp_timer_2msl;
 906                         break;
 907                 default:
 908                         if (tp->t_fb->tfb_tcp_timer_activate) {
 909                                 tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
 910                                 return;
 911                         }
 912                         panic("tp %p bad timer_type %#x", tp, timer_type);
 913                 }
 914         if (delta == 0) {
 915                 callout_stop(t_callout);
 916         } else {
 917                 callout_reset_on(t_callout, delta, f_callout, tp, cpu);
 918         }
 919 }
 920
 921 int
 922 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
 923 {
 924         struct callout *t_callout;
 925
 926         switch (timer_type) {
 927                 case TT_DELACK:
 928                         t_callout = &tp->t_timers->tt_delack;
 929                         break;
 930                 case TT_REXMT:
 931                         t_callout = &tp->t_timers->tt_rexmt;
 932                         break;
 933                 case TT_PERSIST:
 934                         t_callout = &tp->t_timers->tt_persist;
 935                         break;
 936                 case TT_KEEP:
 937                         t_callout = &tp->t_timers->tt_keep;
 938                         break;
 939                 case TT_2MSL:
 940                         t_callout = &tp->t_timers->tt_2msl;
 941                         break;
 942                 default:
 943                         if (tp->t_fb->tfb_tcp_timer_active) {
 944                                 return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
 945                         }
 946                         panic("tp %p bad timer_type %#x", tp, timer_type);
 947                 }
 948         return callout_active(t_callout);
 949 }
 950
 951 void
 952 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
 953 {
 954         struct callout *t_callout;
 955
 956         tp->t_timers->tt_flags |= TT_STOPPED;
 957         switch (timer_type) {
 958                 case TT_DELACK:
 959                         t_callout = &tp->t_timers->tt_delack;
 960                         break;
 961                 case TT_REXMT:
 962                         t_callout = &tp->t_timers->tt_rexmt;
 963                         break;
 964                 case TT_PERSIST:
 965                         t_callout = &tp->t_timers->tt_persist;
 966                         break;
 967                 case TT_KEEP:
 968                         t_callout = &tp->t_timers->tt_keep;
 969                         break;
 970                 case TT_2MSL:
 971                         t_callout = &tp->t_timers->tt_2msl;
 972                         break;
 973                 default:
 974                         if (tp->t_fb->tfb_tcp_timer_stop) {
 975                                 /*
 976                                  * XXXrrs we need to look at this with the
 977                                  * stop case below (flags).
 978                                  */
 979                                 tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
 980                                 return;
 981                         }
 982                         panic("tp %p bad timer_type %#x", tp, timer_type);
 983                 }
 984
 985         if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
 986                 /*
 987                  * Can't stop the callout, defer tcpcb actual deletion
 988                  * to the last one. We do this using the async drain
 989                  * function and incrementing the count in
 990                  */
 991                 tp->t_timers->tt_draincnt++;
 992         }
 993 }