The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_timer.c

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    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: releng/10.4/sys/netinet/tcp_timer.c 309108 2016-11-24 14:48:46Z jch $");
   34 
   35 #include "opt_inet.h"
   36 #include "opt_inet6.h"
   37 #include "opt_tcpdebug.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/vnet.h>
   54 
   55 #include <netinet/cc.h>
   56 #include <netinet/in.h>
   57 #include <netinet/in_pcb.h>
   58 #include <netinet/in_systm.h>
   59 #ifdef INET6
   60 #include <netinet6/in6_pcb.h>
   61 #endif
   62 #include <netinet/ip_var.h>
   63 #include <netinet/tcp_fsm.h>
   64 #include <netinet/tcp_timer.h>
   65 #include <netinet/tcp_var.h>
   66 #ifdef INET6
   67 #include <netinet6/tcp6_var.h>
   68 #endif
   69 #include <netinet/tcpip.h>
   70 #ifdef TCPDEBUG
   71 #include <netinet/tcp_debug.h>
   72 #endif
   73 
   74 int    tcp_persmin;
   75 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
   76     &tcp_persmin, 0, sysctl_msec_to_ticks, "I", "minimum persistence interval");
   77 
   78 int    tcp_persmax;
   79 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
   80     &tcp_persmax, 0, sysctl_msec_to_ticks, "I", "maximum persistence interval");
   81 
   82 int     tcp_keepinit;
   83 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
   84     &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
   85 
   86 int     tcp_keepidle;
   87 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
   88     &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
   89 
   90 int     tcp_keepintvl;
   91 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
   92     &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
   93 
   94 int     tcp_delacktime;
   95 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
   96     &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
   97     "Time before a delayed ACK is sent");
   98 
   99 int     tcp_msl;
  100 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
  101     &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
  102 
  103 int     tcp_rexmit_min;
  104 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
  105     &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
  106     "Minimum Retransmission Timeout");
  107 
  108 int     tcp_rexmit_slop;
  109 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
  110     &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
  111     "Retransmission Timer Slop");
  112 
  113 static int      always_keepalive = 1;
  114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
  115     &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
  116 
  117 int    tcp_fast_finwait2_recycle = 0;
  118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW, 
  119     &tcp_fast_finwait2_recycle, 0,
  120     "Recycle closed FIN_WAIT_2 connections faster");
  121 
  122 int    tcp_finwait2_timeout;
  123 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
  124     &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
  125 
  126 int     tcp_keepcnt = TCPTV_KEEPCNT;
  127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
  128     "Number of keepalive probes to send");
  129 
  130         /* max idle probes */
  131 int     tcp_maxpersistidle;
  132 
  133 static int      tcp_rexmit_drop_options = 0;
  134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
  135     &tcp_rexmit_drop_options, 0,
  136     "Drop TCP options from 3rd and later retransmitted SYN");
  137 
  138 static VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
  139 #define V_tcp_pmtud_blackhole_detect    VNET(tcp_pmtud_blackhole_detect)
  140 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
  141     CTLFLAG_RW,
  142     &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
  143     "Path MTU Discovery Black Hole Detection Enabled");
  144 
  145 static VNET_DEFINE(int, tcp_pmtud_blackhole_activated);
  146 #define V_tcp_pmtud_blackhole_activated \
  147     VNET(tcp_pmtud_blackhole_activated)
  148 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_activated,
  149     CTLFLAG_RD,
  150     &VNET_NAME(tcp_pmtud_blackhole_activated), 0,
  151     "Path MTU Discovery Black Hole Detection, Activation Count");
  152 
  153 static VNET_DEFINE(int, tcp_pmtud_blackhole_activated_min_mss);
  154 #define V_tcp_pmtud_blackhole_activated_min_mss \
  155     VNET(tcp_pmtud_blackhole_activated_min_mss)
  156 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_activated_min_mss,
  157     CTLFLAG_RD,
  158     &VNET_NAME(tcp_pmtud_blackhole_activated_min_mss), 0,
  159     "Path MTU Discovery Black Hole Detection, Activation Count at min MSS");
  160 
  161 static VNET_DEFINE(int, tcp_pmtud_blackhole_failed);
  162 #define V_tcp_pmtud_blackhole_failed    VNET(tcp_pmtud_blackhole_failed)
  163 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_failed,
  164     CTLFLAG_RD,
  165     &VNET_NAME(tcp_pmtud_blackhole_failed), 0,
  166     "Path MTU Discovery Black Hole Detection, Failure Count");
  167 
  168 #ifdef INET
  169 static VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
  170 #define V_tcp_pmtud_blackhole_mss       VNET(tcp_pmtud_blackhole_mss)
  171 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
  172     CTLFLAG_RW,
  173     &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
  174     "Path MTU Discovery Black Hole Detection lowered MSS");
  175 #endif
  176 
  177 #ifdef INET6
  178 static VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
  179 #define V_tcp_v6pmtud_blackhole_mss     VNET(tcp_v6pmtud_blackhole_mss)
  180 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
  181     CTLFLAG_RW,
  182     &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
  183     "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
  184 #endif
  185 
  186 static int      per_cpu_timers = 0;
  187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
  188     &per_cpu_timers , 0, "run tcp timers on all cpus");
  189 
  190 #define INP_CPU(inp)    (per_cpu_timers ? (!CPU_ABSENT(((inp)->inp_flowid % (mp_maxid+1))) ? \
  191                 ((inp)->inp_flowid % (mp_maxid+1)) : curcpu) : 0)
  192 
  193 /*
  194  * Tcp protocol timeout routine called every 500 ms.
  195  * Updates timestamps used for TCP
  196  * causes finite state machine actions if timers expire.
  197  */
  198 void
  199 tcp_slowtimo(void)
  200 {
  201         VNET_ITERATOR_DECL(vnet_iter);
  202 
  203         VNET_LIST_RLOCK_NOSLEEP();
  204         VNET_FOREACH(vnet_iter) {
  205                 CURVNET_SET(vnet_iter);
  206                 (void) tcp_tw_2msl_scan(0);
  207                 CURVNET_RESTORE();
  208         }
  209         VNET_LIST_RUNLOCK_NOSLEEP();
  210 }
  211 
  212 int     tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
  213     { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
  214 
  215 int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
  216     { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
  217 
  218 static int tcp_totbackoff = 2559;       /* sum of tcp_backoff[] */
  219 
  220 /*
  221  * TCP timer processing.
  222  */
  223 
  224 void
  225 tcp_timer_delack(void *xtp)
  226 {
  227         struct tcpcb *tp = xtp;
  228         struct inpcb *inp;
  229         CURVNET_SET(tp->t_vnet);
  230 
  231         inp = tp->t_inpcb;
  232         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  233         INP_WLOCK(inp);
  234         if (callout_pending(&tp->t_timers->tt_delack) ||
  235             !callout_active(&tp->t_timers->tt_delack)) {
  236                 INP_WUNLOCK(inp);
  237                 CURVNET_RESTORE();
  238                 return;
  239         }
  240         callout_deactivate(&tp->t_timers->tt_delack);
  241         if ((inp->inp_flags & INP_DROPPED) != 0) {
  242                 INP_WUNLOCK(inp);
  243                 CURVNET_RESTORE();
  244                 return;
  245         }
  246         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  247                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  248         KASSERT((tp->t_timers->tt_flags & TT_DELACK) != 0,
  249                 ("%s: tp %p delack callout should be running", __func__, tp));
  250 
  251         tp->t_flags |= TF_ACKNOW;
  252         TCPSTAT_INC(tcps_delack);
  253         (void) tcp_output(tp);
  254         INP_WUNLOCK(inp);
  255         CURVNET_RESTORE();
  256 }
  257 
  258 void
  259 tcp_timer_2msl(void *xtp)
  260 {
  261         struct tcpcb *tp = xtp;
  262         struct inpcb *inp;
  263         CURVNET_SET(tp->t_vnet);
  264 #ifdef TCPDEBUG
  265         int ostate;
  266 
  267         ostate = tp->t_state;
  268 #endif
  269         INP_INFO_RLOCK(&V_tcbinfo);
  270         inp = tp->t_inpcb;
  271         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  272         INP_WLOCK(inp);
  273         tcp_free_sackholes(tp);
  274         if (callout_pending(&tp->t_timers->tt_2msl) ||
  275             !callout_active(&tp->t_timers->tt_2msl)) {
  276                 INP_WUNLOCK(tp->t_inpcb);
  277                 INP_INFO_RUNLOCK(&V_tcbinfo);
  278                 CURVNET_RESTORE();
  279                 return;
  280         }
  281         callout_deactivate(&tp->t_timers->tt_2msl);
  282         if ((inp->inp_flags & INP_DROPPED) != 0) {
  283                 INP_WUNLOCK(inp);
  284                 INP_INFO_RUNLOCK(&V_tcbinfo);
  285                 CURVNET_RESTORE();
  286                 return;
  287         }
  288         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  289                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  290         KASSERT((tp->t_timers->tt_flags & TT_2MSL) != 0,
  291                 ("%s: tp %p 2msl callout should be running", __func__, tp));
  292         /*
  293          * 2 MSL timeout in shutdown went off.  If we're closed but
  294          * still waiting for peer to close and connection has been idle
  295          * too long delete connection control block.  Otherwise, check
  296          * again in a bit.
  297          *
  298          * If in TIME_WAIT state just ignore as this timeout is handled in
  299          * tcp_tw_2msl_scan().
  300          *
  301          * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed, 
  302          * there's no point in hanging onto FIN_WAIT_2 socket. Just close it. 
  303          * Ignore fact that there were recent incoming segments.
  304          */
  305         if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
  306                 INP_WUNLOCK(inp);
  307                 INP_INFO_RUNLOCK(&V_tcbinfo);
  308                 CURVNET_RESTORE();
  309                 return;
  310         }
  311         if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
  312             tp->t_inpcb && tp->t_inpcb->inp_socket && 
  313             (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
  314                 TCPSTAT_INC(tcps_finwait2_drops);
  315                 tp = tcp_close(tp);             
  316         } else {
  317                 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
  318                         if (!callout_reset(&tp->t_timers->tt_2msl,
  319                            TP_KEEPINTVL(tp), tcp_timer_2msl, tp)) {
  320                                 tp->t_timers->tt_flags &= ~TT_2MSL_RST;
  321                         }
  322                 } else
  323                        tp = tcp_close(tp);
  324        }
  325 
  326 #ifdef TCPDEBUG
  327         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  328                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  329                           PRU_SLOWTIMO);
  330 #endif
  331         if (tp != NULL)
  332                 INP_WUNLOCK(inp);
  333         INP_INFO_RUNLOCK(&V_tcbinfo);
  334         CURVNET_RESTORE();
  335 }
  336 
  337 void
  338 tcp_timer_keep(void *xtp)
  339 {
  340         struct tcpcb *tp = xtp;
  341         struct tcptemp *t_template;
  342         struct inpcb *inp;
  343         CURVNET_SET(tp->t_vnet);
  344 #ifdef TCPDEBUG
  345         int ostate;
  346 
  347         ostate = tp->t_state;
  348 #endif
  349         INP_INFO_RLOCK(&V_tcbinfo);
  350         inp = tp->t_inpcb;
  351         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  352         INP_WLOCK(inp);
  353         if (callout_pending(&tp->t_timers->tt_keep) ||
  354             !callout_active(&tp->t_timers->tt_keep)) {
  355                 INP_WUNLOCK(inp);
  356                 INP_INFO_RUNLOCK(&V_tcbinfo);
  357                 CURVNET_RESTORE();
  358                 return;
  359         }
  360         callout_deactivate(&tp->t_timers->tt_keep);
  361         if ((inp->inp_flags & INP_DROPPED) != 0) {
  362                 INP_WUNLOCK(inp);
  363                 INP_INFO_RUNLOCK(&V_tcbinfo);
  364                 CURVNET_RESTORE();
  365                 return;
  366         }
  367         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  368                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  369         KASSERT((tp->t_timers->tt_flags & TT_KEEP) != 0,
  370                 ("%s: tp %p keep callout should be running", __func__, tp));
  371         /*
  372          * Keep-alive timer went off; send something
  373          * or drop connection if idle for too long.
  374          */
  375         TCPSTAT_INC(tcps_keeptimeo);
  376         if (tp->t_state < TCPS_ESTABLISHED)
  377                 goto dropit;
  378         if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) &&
  379             tp->t_state <= TCPS_CLOSING) {
  380                 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
  381                         goto dropit;
  382                 /*
  383                  * Send a packet designed to force a response
  384                  * if the peer is up and reachable:
  385                  * either an ACK if the connection is still alive,
  386                  * or an RST if the peer has closed the connection
  387                  * due to timeout or reboot.
  388                  * Using sequence number tp->snd_una-1
  389                  * causes the transmitted zero-length segment
  390                  * to lie outside the receive window;
  391                  * by the protocol spec, this requires the
  392                  * correspondent TCP to respond.
  393                  */
  394                 TCPSTAT_INC(tcps_keepprobe);
  395                 t_template = tcpip_maketemplate(inp);
  396                 if (t_template) {
  397                         tcp_respond(tp, t_template->tt_ipgen,
  398                                     &t_template->tt_t, (struct mbuf *)NULL,
  399                                     tp->rcv_nxt, tp->snd_una - 1, 0);
  400                         free(t_template, M_TEMP);
  401                 }
  402                 if (!callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
  403                     tcp_timer_keep, tp)) {
  404                         tp->t_timers->tt_flags &= ~TT_KEEP_RST;
  405                 }
  406         } else if (!callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
  407                     tcp_timer_keep, tp)) {
  408                         tp->t_timers->tt_flags &= ~TT_KEEP_RST;
  409                 }
  410 
  411 #ifdef TCPDEBUG
  412         if (inp->inp_socket->so_options & SO_DEBUG)
  413                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  414                           PRU_SLOWTIMO);
  415 #endif
  416         INP_WUNLOCK(inp);
  417         INP_INFO_RUNLOCK(&V_tcbinfo);
  418         CURVNET_RESTORE();
  419         return;
  420 
  421 dropit:
  422         TCPSTAT_INC(tcps_keepdrops);
  423         tp = tcp_drop(tp, ETIMEDOUT);
  424 
  425 #ifdef TCPDEBUG
  426         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  427                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  428                           PRU_SLOWTIMO);
  429 #endif
  430         if (tp != NULL)
  431                 INP_WUNLOCK(tp->t_inpcb);
  432         INP_INFO_RUNLOCK(&V_tcbinfo);
  433         CURVNET_RESTORE();
  434 }
  435 
  436 void
  437 tcp_timer_persist(void *xtp)
  438 {
  439         struct tcpcb *tp = xtp;
  440         struct inpcb *inp;
  441         CURVNET_SET(tp->t_vnet);
  442 #ifdef TCPDEBUG
  443         int ostate;
  444 
  445         ostate = tp->t_state;
  446 #endif
  447         INP_INFO_RLOCK(&V_tcbinfo);
  448         inp = tp->t_inpcb;
  449         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  450         INP_WLOCK(inp);
  451         if (callout_pending(&tp->t_timers->tt_persist) ||
  452             !callout_active(&tp->t_timers->tt_persist)) {
  453                 INP_WUNLOCK(inp);
  454                 INP_INFO_RUNLOCK(&V_tcbinfo);
  455                 CURVNET_RESTORE();
  456                 return;
  457         }
  458         callout_deactivate(&tp->t_timers->tt_persist);
  459         if ((inp->inp_flags & INP_DROPPED) != 0) {
  460                 INP_WUNLOCK(inp);
  461                 INP_INFO_RUNLOCK(&V_tcbinfo);
  462                 CURVNET_RESTORE();
  463                 return;
  464         }
  465         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  466                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  467         KASSERT((tp->t_timers->tt_flags & TT_PERSIST) != 0,
  468                 ("%s: tp %p persist callout should be running", __func__, tp));
  469         /*
  470          * Persistance timer into zero window.
  471          * Force a byte to be output, if possible.
  472          */
  473         TCPSTAT_INC(tcps_persisttimeo);
  474         /*
  475          * Hack: if the peer is dead/unreachable, we do not
  476          * time out if the window is closed.  After a full
  477          * backoff, drop the connection if the idle time
  478          * (no responses to probes) reaches the maximum
  479          * backoff that we would use if retransmitting.
  480          */
  481         if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
  482             (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
  483              ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
  484                 TCPSTAT_INC(tcps_persistdrop);
  485                 tp = tcp_drop(tp, ETIMEDOUT);
  486                 goto out;
  487         }
  488         /*
  489          * If the user has closed the socket then drop a persisting
  490          * connection after a much reduced timeout.
  491          */
  492         if (tp->t_state > TCPS_CLOSE_WAIT &&
  493             (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
  494                 TCPSTAT_INC(tcps_persistdrop);
  495                 tp = tcp_drop(tp, ETIMEDOUT);
  496                 goto out;
  497         }
  498         tcp_setpersist(tp);
  499         tp->t_flags |= TF_FORCEDATA;
  500         (void) tcp_output(tp);
  501         tp->t_flags &= ~TF_FORCEDATA;
  502 
  503 out:
  504 #ifdef TCPDEBUG
  505         if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
  506                 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
  507 #endif
  508         if (tp != NULL)
  509                 INP_WUNLOCK(inp);
  510         INP_INFO_RUNLOCK(&V_tcbinfo);
  511         CURVNET_RESTORE();
  512 }
  513 
  514 void
  515 tcp_timer_rexmt(void * xtp)
  516 {
  517         struct tcpcb *tp = xtp;
  518         CURVNET_SET(tp->t_vnet);
  519         int rexmt;
  520         int headlocked;
  521         struct inpcb *inp;
  522 #ifdef TCPDEBUG
  523         int ostate;
  524 
  525         ostate = tp->t_state;
  526 #endif
  527 
  528         INP_INFO_RLOCK(&V_tcbinfo);
  529         inp = tp->t_inpcb;
  530         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  531         INP_WLOCK(inp);
  532         if (callout_pending(&tp->t_timers->tt_rexmt) ||
  533             !callout_active(&tp->t_timers->tt_rexmt)) {
  534                 INP_WUNLOCK(inp);
  535                 INP_INFO_RUNLOCK(&V_tcbinfo);
  536                 CURVNET_RESTORE();
  537                 return;
  538         }
  539         callout_deactivate(&tp->t_timers->tt_rexmt);
  540         if ((inp->inp_flags & INP_DROPPED) != 0) {
  541                 INP_WUNLOCK(inp);
  542                 INP_INFO_RUNLOCK(&V_tcbinfo);
  543                 CURVNET_RESTORE();
  544                 return;
  545         }
  546         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  547                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  548         KASSERT((tp->t_timers->tt_flags & TT_REXMT) != 0,
  549                 ("%s: tp %p rexmt callout should be running", __func__, tp));
  550         tcp_free_sackholes(tp);
  551         /*
  552          * Retransmission timer went off.  Message has not
  553          * been acked within retransmit interval.  Back off
  554          * to a longer retransmit interval and retransmit one segment.
  555          */
  556         if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
  557                 tp->t_rxtshift = TCP_MAXRXTSHIFT;
  558                 TCPSTAT_INC(tcps_timeoutdrop);
  559 
  560                 tp = tcp_drop(tp, tp->t_softerror ?
  561                               tp->t_softerror : ETIMEDOUT);
  562                 headlocked = 1;
  563                 goto out;
  564         }
  565         INP_INFO_RUNLOCK(&V_tcbinfo);
  566         headlocked = 0;
  567         if (tp->t_state == TCPS_SYN_SENT) {
  568                 /*
  569                  * If the SYN was retransmitted, indicate CWND to be
  570                  * limited to 1 segment in cc_conn_init().
  571                  */
  572                 tp->snd_cwnd = 1;
  573         } else if (tp->t_rxtshift == 1) {
  574                 /*
  575                  * first retransmit; record ssthresh and cwnd so they can
  576                  * be recovered if this turns out to be a "bad" retransmit.
  577                  * A retransmit is considered "bad" if an ACK for this
  578                  * segment is received within RTT/2 interval; the assumption
  579                  * here is that the ACK was already in flight.  See
  580                  * "On Estimating End-to-End Network Path Properties" by
  581                  * Allman and Paxson for more details.
  582                  */
  583                 tp->snd_cwnd_prev = tp->snd_cwnd;
  584                 tp->snd_ssthresh_prev = tp->snd_ssthresh;
  585                 tp->snd_recover_prev = tp->snd_recover;
  586                 if (IN_FASTRECOVERY(tp->t_flags))
  587                         tp->t_flags |= TF_WASFRECOVERY;
  588                 else
  589                         tp->t_flags &= ~TF_WASFRECOVERY;
  590                 if (IN_CONGRECOVERY(tp->t_flags))
  591                         tp->t_flags |= TF_WASCRECOVERY;
  592                 else
  593                         tp->t_flags &= ~TF_WASCRECOVERY;
  594                 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
  595                 tp->t_flags |= TF_PREVVALID;
  596         } else
  597                 tp->t_flags &= ~TF_PREVVALID;
  598         TCPSTAT_INC(tcps_rexmttimeo);
  599         if ((tp->t_state == TCPS_SYN_SENT) ||
  600             (tp->t_state == TCPS_SYN_RECEIVED))
  601                 rexmt = TCPTV_RTOBASE * tcp_syn_backoff[tp->t_rxtshift];
  602         else
  603                 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
  604         TCPT_RANGESET(tp->t_rxtcur, rexmt,
  605                       tp->t_rttmin, TCPTV_REXMTMAX);
  606 
  607         /*
  608          * We enter the path for PLMTUD if connection is established or, if
  609          * connection is FIN_WAIT_1 status, reason for the last is that if
  610          * amount of data we send is very small, we could send it in couple of
  611          * packets and process straight to FIN. In that case we won't catch
  612          * ESTABLISHED state.
  613          */
  614         if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
  615             || (tp->t_state == TCPS_FIN_WAIT_1))) {
  616                 int optlen;
  617 #ifdef INET6
  618                 int isipv6;
  619 #endif
  620 
  621                 /*
  622                  * Idea here is that at each stage of mtu probe (usually, 1448
  623                  * -> 1188 -> 524) should be given 2 chances to recover before
  624                  *  further clamping down. 'tp->t_rxtshift % 2 == 0' should
  625                  *  take care of that.
  626                  */
  627                 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
  628                     (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
  629                     (tp->t_rxtshift >= 2 && tp->t_rxtshift % 2 == 0)) {
  630                         /*
  631                          * Enter Path MTU Black-hole Detection mechanism:
  632                          * - Disable Path MTU Discovery (IP "DF" bit).
  633                          * - Reduce MTU to lower value than what we
  634                          *   negotiated with peer.
  635                          */
  636                         /* Record that we may have found a black hole. */
  637                         tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
  638 
  639                         /* Keep track of previous MSS. */
  640                         optlen = tp->t_maxopd - tp->t_maxseg;
  641                         tp->t_pmtud_saved_maxopd = tp->t_maxopd;
  642 
  643                         /* 
  644                          * Reduce the MSS to blackhole value or to the default
  645                          * in an attempt to retransmit.
  646                          */
  647 #ifdef INET6
  648                         isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
  649                         if (isipv6 &&
  650                             tp->t_maxopd > V_tcp_v6pmtud_blackhole_mss) {
  651                                 /* Use the sysctl tuneable blackhole MSS. */
  652                                 tp->t_maxopd = V_tcp_v6pmtud_blackhole_mss;
  653                                 V_tcp_pmtud_blackhole_activated++;
  654                         } else if (isipv6) {
  655                                 /* Use the default MSS. */
  656                                 tp->t_maxopd = V_tcp_v6mssdflt;
  657                                 /*
  658                                  * Disable Path MTU Discovery when we switch to
  659                                  * minmss.
  660                                  */
  661                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
  662                                 V_tcp_pmtud_blackhole_activated_min_mss++;
  663                         }
  664 #endif
  665 #if defined(INET6) && defined(INET)
  666                         else
  667 #endif
  668 #ifdef INET
  669                         if (tp->t_maxopd > V_tcp_pmtud_blackhole_mss) {
  670                                 /* Use the sysctl tuneable blackhole MSS. */
  671                                 tp->t_maxopd = V_tcp_pmtud_blackhole_mss;
  672                                 V_tcp_pmtud_blackhole_activated++;
  673                         } else {
  674                                 /* Use the default MSS. */
  675                                 tp->t_maxopd = V_tcp_mssdflt;
  676                                 /*
  677                                  * Disable Path MTU Discovery when we switch to
  678                                  * minmss.
  679                                  */
  680                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
  681                                 V_tcp_pmtud_blackhole_activated_min_mss++;
  682                         }
  683 #endif
  684                         tp->t_maxseg = tp->t_maxopd - optlen;
  685                         /*
  686                          * Reset the slow-start flight size
  687                          * as it may depend on the new MSS.
  688                          */
  689                         if (CC_ALGO(tp)->conn_init != NULL)
  690                                 CC_ALGO(tp)->conn_init(tp->ccv);
  691                 } else {
  692                         /*
  693                          * If further retransmissions are still unsuccessful
  694                          * with a lowered MTU, maybe this isn't a blackhole and
  695                          * we restore the previous MSS and blackhole detection
  696                          * flags.
  697                          * The limit '6' is determined by giving each probe
  698                          * stage (1448, 1188, 524) 2 chances to recover.
  699                          */
  700                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
  701                             (tp->t_rxtshift > 6)) {
  702                                 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
  703                                 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
  704                                 optlen = tp->t_maxopd - tp->t_maxseg;
  705                                 tp->t_maxopd = tp->t_pmtud_saved_maxopd;
  706                                 tp->t_maxseg = tp->t_maxopd - optlen;
  707                                 V_tcp_pmtud_blackhole_failed++;
  708                                 /*
  709                                  * Reset the slow-start flight size as it
  710                                  * may depend on the new MSS.
  711                                  */
  712                                 if (CC_ALGO(tp)->conn_init != NULL)
  713                                         CC_ALGO(tp)->conn_init(tp->ccv);
  714                         }
  715                 }
  716         }
  717 
  718         /*
  719          * Disable RFC1323 and SACK if we haven't got any response to
  720          * our third SYN to work-around some broken terminal servers
  721          * (most of which have hopefully been retired) that have bad VJ
  722          * header compression code which trashes TCP segments containing
  723          * unknown-to-them TCP options.
  724          */
  725         if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
  726             (tp->t_rxtshift == 3))
  727                 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
  728         /*
  729          * If we backed off this far, our srtt estimate is probably bogus.
  730          * Clobber it so we'll take the next rtt measurement as our srtt;
  731          * move the current srtt into rttvar to keep the current
  732          * retransmit times until then.
  733          */
  734         if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
  735 #ifdef INET6
  736                 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
  737                         in6_losing(tp->t_inpcb);
  738 #endif
  739                 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
  740                 tp->t_srtt = 0;
  741         }
  742         tp->snd_nxt = tp->snd_una;
  743         tp->snd_recover = tp->snd_max;
  744         /*
  745          * Force a segment to be sent.
  746          */
  747         tp->t_flags |= TF_ACKNOW;
  748         /*
  749          * If timing a segment in this window, stop the timer.
  750          */
  751         tp->t_rtttime = 0;
  752 
  753         cc_cong_signal(tp, NULL, CC_RTO);
  754 
  755         (void) tcp_output(tp);
  756 
  757 out:
  758 #ifdef TCPDEBUG
  759         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  760                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  761                           PRU_SLOWTIMO);
  762 #endif
  763         if (tp != NULL)
  764                 INP_WUNLOCK(inp);
  765         if (headlocked)
  766                 INP_INFO_RUNLOCK(&V_tcbinfo);
  767         CURVNET_RESTORE();
  768 }
  769 
  770 void
  771 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
  772 {
  773         struct callout *t_callout;
  774         timeout_t *f_callout;
  775         struct inpcb *inp = tp->t_inpcb;
  776         int cpu = INP_CPU(inp);
  777         uint32_t f_reset;
  778 
  779 #ifdef TCP_OFFLOAD
  780         if (tp->t_flags & TF_TOE)
  781                 return;
  782 #endif
  783 
  784         if (tp->t_timers->tt_flags & TT_STOPPED)
  785                 return;
  786 
  787         switch (timer_type) {
  788                 case TT_DELACK:
  789                         t_callout = &tp->t_timers->tt_delack;
  790                         f_callout = tcp_timer_delack;
  791                         f_reset = TT_DELACK_RST;
  792                         break;
  793                 case TT_REXMT:
  794                         t_callout = &tp->t_timers->tt_rexmt;
  795                         f_callout = tcp_timer_rexmt;
  796                         f_reset = TT_REXMT_RST;
  797                         break;
  798                 case TT_PERSIST:
  799                         t_callout = &tp->t_timers->tt_persist;
  800                         f_callout = tcp_timer_persist;
  801                         f_reset = TT_PERSIST_RST;
  802                         break;
  803                 case TT_KEEP:
  804                         t_callout = &tp->t_timers->tt_keep;
  805                         f_callout = tcp_timer_keep;
  806                         f_reset = TT_KEEP_RST;
  807                         break;
  808                 case TT_2MSL:
  809                         t_callout = &tp->t_timers->tt_2msl;
  810                         f_callout = tcp_timer_2msl;
  811                         f_reset = TT_2MSL_RST;
  812                         break;
  813                 default:
  814                         panic("tp %p bad timer_type %#x", tp, timer_type);
  815                 }
  816         if (delta == 0) {
  817                 if ((tp->t_timers->tt_flags & timer_type) &&
  818                     callout_stop(t_callout) &&
  819                     (tp->t_timers->tt_flags & f_reset)) {
  820                         tp->t_timers->tt_flags &= ~(timer_type | f_reset);
  821                 }
  822         } else {
  823                 if ((tp->t_timers->tt_flags & timer_type) == 0) {
  824                         tp->t_timers->tt_flags |= (timer_type | f_reset);
  825                         callout_reset_on(t_callout, delta, f_callout, tp, cpu);
  826                 } else {
  827                         /* Reset already running callout on the same CPU. */
  828                         if (!callout_reset(t_callout, delta, f_callout, tp)) {
  829                                 /*
  830                                  * Callout not cancelled, consider it as not
  831                                  * properly restarted. */
  832                                 tp->t_timers->tt_flags &= ~f_reset;
  833                         }
  834                 }
  835         }
  836 }
  837 
  838 int
  839 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
  840 {
  841         struct callout *t_callout;
  842 
  843         switch (timer_type) {
  844                 case TT_DELACK:
  845                         t_callout = &tp->t_timers->tt_delack;
  846                         break;
  847                 case TT_REXMT:
  848                         t_callout = &tp->t_timers->tt_rexmt;
  849                         break;
  850                 case TT_PERSIST:
  851                         t_callout = &tp->t_timers->tt_persist;
  852                         break;
  853                 case TT_KEEP:
  854                         t_callout = &tp->t_timers->tt_keep;
  855                         break;
  856                 case TT_2MSL:
  857                         t_callout = &tp->t_timers->tt_2msl;
  858                         break;
  859                 default:
  860                         panic("tp %p bad timer_type %#x", tp, timer_type);
  861                 }
  862         return callout_active(t_callout);
  863 }
  864 
  865 void
  866 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
  867 {
  868         struct callout *t_callout;
  869         timeout_t *f_callout;
  870         uint32_t f_reset;
  871 
  872         tp->t_timers->tt_flags |= TT_STOPPED;
  873 
  874         switch (timer_type) {
  875                 case TT_DELACK:
  876                         t_callout = &tp->t_timers->tt_delack;
  877                         f_callout = tcp_timer_delack_discard;
  878                         f_reset = TT_DELACK_RST;
  879                         break;
  880                 case TT_REXMT:
  881                         t_callout = &tp->t_timers->tt_rexmt;
  882                         f_callout = tcp_timer_rexmt_discard;
  883                         f_reset = TT_REXMT_RST;
  884                         break;
  885                 case TT_PERSIST:
  886                         t_callout = &tp->t_timers->tt_persist;
  887                         f_callout = tcp_timer_persist_discard;
  888                         f_reset = TT_PERSIST_RST;
  889                         break;
  890                 case TT_KEEP:
  891                         t_callout = &tp->t_timers->tt_keep;
  892                         f_callout = tcp_timer_keep_discard;
  893                         f_reset = TT_KEEP_RST;
  894                         break;
  895                 case TT_2MSL:
  896                         t_callout = &tp->t_timers->tt_2msl;
  897                         f_callout = tcp_timer_2msl_discard;
  898                         f_reset = TT_2MSL_RST;
  899                         break;
  900                 default:
  901                         panic("tp %p bad timer_type %#x", tp, timer_type);
  902                 }
  903 
  904         if (tp->t_timers->tt_flags & timer_type) {
  905                 if (callout_stop(t_callout) &&
  906                     (tp->t_timers->tt_flags & f_reset)) {
  907                         tp->t_timers->tt_flags &= ~(timer_type | f_reset);
  908                 } else {
  909                         /*
  910                          * Can't stop the callout, defer tcpcb actual deletion
  911                          * to the last tcp timer discard callout.
  912                          * The TT_STOPPED flag will ensure that no tcp timer
  913                          * callouts can be restarted on our behalf, and
  914                          * past this point currently running callouts waiting
  915                          * on inp lock will return right away after the
  916                          * classical check for callout reset/stop events:
  917                          * callout_pending() || !callout_active()
  918                          */
  919                         callout_reset(t_callout, 1, f_callout, tp);
  920                 }
  921         }
  922 }
  923 
  924 #define ticks_to_msecs(t)       (1000*(t) / hz)
  925 
  926 void
  927 tcp_timer_to_xtimer(struct tcpcb *tp, struct tcp_timer *timer,
  928     struct xtcp_timer *xtimer)
  929 {
  930         sbintime_t now;
  931 
  932         bzero(xtimer, sizeof(*xtimer));
  933         if (timer == NULL)
  934                 return;
  935         now = getsbinuptime();
  936         if (callout_active(&timer->tt_delack))
  937                 xtimer->tt_delack = (timer->tt_delack.c_time - now) / SBT_1MS;
  938         if (callout_active(&timer->tt_rexmt))
  939                 xtimer->tt_rexmt = (timer->tt_rexmt.c_time - now) / SBT_1MS;
  940         if (callout_active(&timer->tt_persist))
  941                 xtimer->tt_persist = (timer->tt_persist.c_time - now) / SBT_1MS;
  942         if (callout_active(&timer->tt_keep))
  943                 xtimer->tt_keep = (timer->tt_keep.c_time - now) / SBT_1MS;
  944         if (callout_active(&timer->tt_2msl))
  945                 xtimer->tt_2msl = (timer->tt_2msl.c_time - now) / SBT_1MS;
  946         xtimer->t_rcvtime = ticks_to_msecs(ticks - tp->t_rcvtime);
  947 }

Cache object: 825f4534a46b933701bf84c7523e76ce


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