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/10.3/sys/netinet/tcp_timer.c 295015 2016-01-28 21:30:49Z hiren $");
   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_WLOCK(&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_WUNLOCK(&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_WUNLOCK(&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, or if 2MSL time is up from TIME_WAIT, delete connection
  296          * control block.  Otherwise, check again in a bit.
  297          *
  298          * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed, 
  299          * there's no point in hanging onto FIN_WAIT_2 socket. Just close it. 
  300          * Ignore fact that there were recent incoming segments.
  301          */
  302         if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
  303             tp->t_inpcb && tp->t_inpcb->inp_socket && 
  304             (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
  305                 TCPSTAT_INC(tcps_finwait2_drops);
  306                 tp = tcp_close(tp);             
  307         } else {
  308                 if (tp->t_state != TCPS_TIME_WAIT &&
  309                    ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
  310                         if (!callout_reset(&tp->t_timers->tt_2msl,
  311                            TP_KEEPINTVL(tp), tcp_timer_2msl, tp)) {
  312                                 tp->t_timers->tt_flags &= ~TT_2MSL_RST;
  313                         }
  314                 } else
  315                        tp = tcp_close(tp);
  316        }
  317 
  318 #ifdef TCPDEBUG
  319         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  320                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  321                           PRU_SLOWTIMO);
  322 #endif
  323         if (tp != NULL)
  324                 INP_WUNLOCK(inp);
  325         INP_INFO_WUNLOCK(&V_tcbinfo);
  326         CURVNET_RESTORE();
  327 }
  328 
  329 void
  330 tcp_timer_keep(void *xtp)
  331 {
  332         struct tcpcb *tp = xtp;
  333         struct tcptemp *t_template;
  334         struct inpcb *inp;
  335         CURVNET_SET(tp->t_vnet);
  336 #ifdef TCPDEBUG
  337         int ostate;
  338 
  339         ostate = tp->t_state;
  340 #endif
  341         INP_INFO_WLOCK(&V_tcbinfo);
  342         inp = tp->t_inpcb;
  343         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  344         INP_WLOCK(inp);
  345         if (callout_pending(&tp->t_timers->tt_keep) ||
  346             !callout_active(&tp->t_timers->tt_keep)) {
  347                 INP_WUNLOCK(inp);
  348                 INP_INFO_WUNLOCK(&V_tcbinfo);
  349                 CURVNET_RESTORE();
  350                 return;
  351         }
  352         callout_deactivate(&tp->t_timers->tt_keep);
  353         if ((inp->inp_flags & INP_DROPPED) != 0) {
  354                 INP_WUNLOCK(inp);
  355                 INP_INFO_WUNLOCK(&V_tcbinfo);
  356                 CURVNET_RESTORE();
  357                 return;
  358         }
  359         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  360                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  361         KASSERT((tp->t_timers->tt_flags & TT_KEEP) != 0,
  362                 ("%s: tp %p keep callout should be running", __func__, tp));
  363         /*
  364          * Keep-alive timer went off; send something
  365          * or drop connection if idle for too long.
  366          */
  367         TCPSTAT_INC(tcps_keeptimeo);
  368         if (tp->t_state < TCPS_ESTABLISHED)
  369                 goto dropit;
  370         if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) &&
  371             tp->t_state <= TCPS_CLOSING) {
  372                 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
  373                         goto dropit;
  374                 /*
  375                  * Send a packet designed to force a response
  376                  * if the peer is up and reachable:
  377                  * either an ACK if the connection is still alive,
  378                  * or an RST if the peer has closed the connection
  379                  * due to timeout or reboot.
  380                  * Using sequence number tp->snd_una-1
  381                  * causes the transmitted zero-length segment
  382                  * to lie outside the receive window;
  383                  * by the protocol spec, this requires the
  384                  * correspondent TCP to respond.
  385                  */
  386                 TCPSTAT_INC(tcps_keepprobe);
  387                 t_template = tcpip_maketemplate(inp);
  388                 if (t_template) {
  389                         tcp_respond(tp, t_template->tt_ipgen,
  390                                     &t_template->tt_t, (struct mbuf *)NULL,
  391                                     tp->rcv_nxt, tp->snd_una - 1, 0);
  392                         free(t_template, M_TEMP);
  393                 }
  394                 if (!callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
  395                     tcp_timer_keep, tp)) {
  396                         tp->t_timers->tt_flags &= ~TT_KEEP_RST;
  397                 }
  398         } else if (!callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
  399                     tcp_timer_keep, tp)) {
  400                         tp->t_timers->tt_flags &= ~TT_KEEP_RST;
  401                 }
  402 
  403 #ifdef TCPDEBUG
  404         if (inp->inp_socket->so_options & SO_DEBUG)
  405                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  406                           PRU_SLOWTIMO);
  407 #endif
  408         INP_WUNLOCK(inp);
  409         INP_INFO_WUNLOCK(&V_tcbinfo);
  410         CURVNET_RESTORE();
  411         return;
  412 
  413 dropit:
  414         TCPSTAT_INC(tcps_keepdrops);
  415         tp = tcp_drop(tp, ETIMEDOUT);
  416 
  417 #ifdef TCPDEBUG
  418         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  419                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  420                           PRU_SLOWTIMO);
  421 #endif
  422         if (tp != NULL)
  423                 INP_WUNLOCK(tp->t_inpcb);
  424         INP_INFO_WUNLOCK(&V_tcbinfo);
  425         CURVNET_RESTORE();
  426 }
  427 
  428 void
  429 tcp_timer_persist(void *xtp)
  430 {
  431         struct tcpcb *tp = xtp;
  432         struct inpcb *inp;
  433         CURVNET_SET(tp->t_vnet);
  434 #ifdef TCPDEBUG
  435         int ostate;
  436 
  437         ostate = tp->t_state;
  438 #endif
  439         INP_INFO_WLOCK(&V_tcbinfo);
  440         inp = tp->t_inpcb;
  441         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  442         INP_WLOCK(inp);
  443         if (callout_pending(&tp->t_timers->tt_persist) ||
  444             !callout_active(&tp->t_timers->tt_persist)) {
  445                 INP_WUNLOCK(inp);
  446                 INP_INFO_WUNLOCK(&V_tcbinfo);
  447                 CURVNET_RESTORE();
  448                 return;
  449         }
  450         callout_deactivate(&tp->t_timers->tt_persist);
  451         if ((inp->inp_flags & INP_DROPPED) != 0) {
  452                 INP_WUNLOCK(inp);
  453                 INP_INFO_WUNLOCK(&V_tcbinfo);
  454                 CURVNET_RESTORE();
  455                 return;
  456         }
  457         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  458                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  459         KASSERT((tp->t_timers->tt_flags & TT_PERSIST) != 0,
  460                 ("%s: tp %p persist callout should be running", __func__, tp));
  461         /*
  462          * Persistance timer into zero window.
  463          * Force a byte to be output, if possible.
  464          */
  465         TCPSTAT_INC(tcps_persisttimeo);
  466         /*
  467          * Hack: if the peer is dead/unreachable, we do not
  468          * time out if the window is closed.  After a full
  469          * backoff, drop the connection if the idle time
  470          * (no responses to probes) reaches the maximum
  471          * backoff that we would use if retransmitting.
  472          */
  473         if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
  474             (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
  475              ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
  476                 TCPSTAT_INC(tcps_persistdrop);
  477                 tp = tcp_drop(tp, ETIMEDOUT);
  478                 goto out;
  479         }
  480         /*
  481          * If the user has closed the socket then drop a persisting
  482          * connection after a much reduced timeout.
  483          */
  484         if (tp->t_state > TCPS_CLOSE_WAIT &&
  485             (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
  486                 TCPSTAT_INC(tcps_persistdrop);
  487                 tp = tcp_drop(tp, ETIMEDOUT);
  488                 goto out;
  489         }
  490         tcp_setpersist(tp);
  491         tp->t_flags |= TF_FORCEDATA;
  492         (void) tcp_output(tp);
  493         tp->t_flags &= ~TF_FORCEDATA;
  494 
  495 out:
  496 #ifdef TCPDEBUG
  497         if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
  498                 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
  499 #endif
  500         if (tp != NULL)
  501                 INP_WUNLOCK(inp);
  502         INP_INFO_WUNLOCK(&V_tcbinfo);
  503         CURVNET_RESTORE();
  504 }
  505 
  506 void
  507 tcp_timer_rexmt(void * xtp)
  508 {
  509         struct tcpcb *tp = xtp;
  510         CURVNET_SET(tp->t_vnet);
  511         int rexmt;
  512         int headlocked;
  513         struct inpcb *inp;
  514 #ifdef TCPDEBUG
  515         int ostate;
  516 
  517         ostate = tp->t_state;
  518 #endif
  519 
  520         INP_INFO_RLOCK(&V_tcbinfo);
  521         inp = tp->t_inpcb;
  522         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  523         INP_WLOCK(inp);
  524         if (callout_pending(&tp->t_timers->tt_rexmt) ||
  525             !callout_active(&tp->t_timers->tt_rexmt)) {
  526                 INP_WUNLOCK(inp);
  527                 INP_INFO_RUNLOCK(&V_tcbinfo);
  528                 CURVNET_RESTORE();
  529                 return;
  530         }
  531         callout_deactivate(&tp->t_timers->tt_rexmt);
  532         if ((inp->inp_flags & INP_DROPPED) != 0) {
  533                 INP_WUNLOCK(inp);
  534                 INP_INFO_RUNLOCK(&V_tcbinfo);
  535                 CURVNET_RESTORE();
  536                 return;
  537         }
  538         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  539                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  540         KASSERT((tp->t_timers->tt_flags & TT_REXMT) != 0,
  541                 ("%s: tp %p rexmt callout should be running", __func__, tp));
  542         tcp_free_sackholes(tp);
  543         /*
  544          * Retransmission timer went off.  Message has not
  545          * been acked within retransmit interval.  Back off
  546          * to a longer retransmit interval and retransmit one segment.
  547          */
  548         if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
  549                 tp->t_rxtshift = TCP_MAXRXTSHIFT;
  550                 TCPSTAT_INC(tcps_timeoutdrop);
  551                 in_pcbref(inp);
  552                 INP_INFO_RUNLOCK(&V_tcbinfo);
  553                 INP_WUNLOCK(inp);
  554                 INP_INFO_WLOCK(&V_tcbinfo);
  555                 INP_WLOCK(inp);
  556                 if (in_pcbrele_wlocked(inp)) {
  557                         INP_INFO_WUNLOCK(&V_tcbinfo);
  558                         CURVNET_RESTORE();
  559                         return;
  560                 }
  561                 if (inp->inp_flags & INP_DROPPED) {
  562                         INP_WUNLOCK(inp);
  563                         INP_INFO_WUNLOCK(&V_tcbinfo);
  564                         CURVNET_RESTORE();
  565                         return;
  566                 }
  567 
  568                 tp = tcp_drop(tp, tp->t_softerror ?
  569                               tp->t_softerror : ETIMEDOUT);
  570                 headlocked = 1;
  571                 goto out;
  572         }
  573         INP_INFO_RUNLOCK(&V_tcbinfo);
  574         headlocked = 0;
  575         if (tp->t_state == TCPS_SYN_SENT) {
  576                 /*
  577                  * If the SYN was retransmitted, indicate CWND to be
  578                  * limited to 1 segment in cc_conn_init().
  579                  */
  580                 tp->snd_cwnd = 1;
  581         } else if (tp->t_rxtshift == 1) {
  582                 /*
  583                  * first retransmit; record ssthresh and cwnd so they can
  584                  * be recovered if this turns out to be a "bad" retransmit.
  585                  * A retransmit is considered "bad" if an ACK for this
  586                  * segment is received within RTT/2 interval; the assumption
  587                  * here is that the ACK was already in flight.  See
  588                  * "On Estimating End-to-End Network Path Properties" by
  589                  * Allman and Paxson for more details.
  590                  */
  591                 tp->snd_cwnd_prev = tp->snd_cwnd;
  592                 tp->snd_ssthresh_prev = tp->snd_ssthresh;
  593                 tp->snd_recover_prev = tp->snd_recover;
  594                 if (IN_FASTRECOVERY(tp->t_flags))
  595                         tp->t_flags |= TF_WASFRECOVERY;
  596                 else
  597                         tp->t_flags &= ~TF_WASFRECOVERY;
  598                 if (IN_CONGRECOVERY(tp->t_flags))
  599                         tp->t_flags |= TF_WASCRECOVERY;
  600                 else
  601                         tp->t_flags &= ~TF_WASCRECOVERY;
  602                 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
  603                 tp->t_flags |= TF_PREVVALID;
  604         } else
  605                 tp->t_flags &= ~TF_PREVVALID;
  606         TCPSTAT_INC(tcps_rexmttimeo);
  607         if ((tp->t_state == TCPS_SYN_SENT) ||
  608             (tp->t_state == TCPS_SYN_RECEIVED))
  609                 rexmt = TCPTV_RTOBASE * tcp_syn_backoff[tp->t_rxtshift];
  610         else
  611                 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
  612         TCPT_RANGESET(tp->t_rxtcur, rexmt,
  613                       tp->t_rttmin, TCPTV_REXMTMAX);
  614 
  615         /*
  616          * We enter the path for PLMTUD if connection is established or, if
  617          * connection is FIN_WAIT_1 status, reason for the last is that if
  618          * amount of data we send is very small, we could send it in couple of
  619          * packets and process straight to FIN. In that case we won't catch
  620          * ESTABLISHED state.
  621          */
  622         if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
  623             || (tp->t_state == TCPS_FIN_WAIT_1))) {
  624                 int optlen;
  625 #ifdef INET6
  626                 int isipv6;
  627 #endif
  628 
  629                 /*
  630                  * Idea here is that at each stage of mtu probe (usually, 1448
  631                  * -> 1188 -> 524) should be given 2 chances to recover before
  632                  *  further clamping down. 'tp->t_rxtshift % 2 == 0' should
  633                  *  take care of that.
  634                  */
  635                 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
  636                     (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
  637                     (tp->t_rxtshift >= 2 && tp->t_rxtshift % 2 == 0)) {
  638                         /*
  639                          * Enter Path MTU Black-hole Detection mechanism:
  640                          * - Disable Path MTU Discovery (IP "DF" bit).
  641                          * - Reduce MTU to lower value than what we
  642                          *   negotiated with peer.
  643                          */
  644                         /* Record that we may have found a black hole. */
  645                         tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
  646 
  647                         /* Keep track of previous MSS. */
  648                         optlen = tp->t_maxopd - tp->t_maxseg;
  649                         tp->t_pmtud_saved_maxopd = tp->t_maxopd;
  650 
  651                         /* 
  652                          * Reduce the MSS to blackhole value or to the default
  653                          * in an attempt to retransmit.
  654                          */
  655 #ifdef INET6
  656                         isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
  657                         if (isipv6 &&
  658                             tp->t_maxopd > V_tcp_v6pmtud_blackhole_mss) {
  659                                 /* Use the sysctl tuneable blackhole MSS. */
  660                                 tp->t_maxopd = V_tcp_v6pmtud_blackhole_mss;
  661                                 V_tcp_pmtud_blackhole_activated++;
  662                         } else if (isipv6) {
  663                                 /* Use the default MSS. */
  664                                 tp->t_maxopd = V_tcp_v6mssdflt;
  665                                 /*
  666                                  * Disable Path MTU Discovery when we switch to
  667                                  * minmss.
  668                                  */
  669                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
  670                                 V_tcp_pmtud_blackhole_activated_min_mss++;
  671                         }
  672 #endif
  673 #if defined(INET6) && defined(INET)
  674                         else
  675 #endif
  676 #ifdef INET
  677                         if (tp->t_maxopd > V_tcp_pmtud_blackhole_mss) {
  678                                 /* Use the sysctl tuneable blackhole MSS. */
  679                                 tp->t_maxopd = V_tcp_pmtud_blackhole_mss;
  680                                 V_tcp_pmtud_blackhole_activated++;
  681                         } else {
  682                                 /* Use the default MSS. */
  683                                 tp->t_maxopd = V_tcp_mssdflt;
  684                                 /*
  685                                  * Disable Path MTU Discovery when we switch to
  686                                  * minmss.
  687                                  */
  688                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
  689                                 V_tcp_pmtud_blackhole_activated_min_mss++;
  690                         }
  691 #endif
  692                         tp->t_maxseg = tp->t_maxopd - optlen;
  693                         /*
  694                          * Reset the slow-start flight size
  695                          * as it may depend on the new MSS.
  696                          */
  697                         if (CC_ALGO(tp)->conn_init != NULL)
  698                                 CC_ALGO(tp)->conn_init(tp->ccv);
  699                 } else {
  700                         /*
  701                          * If further retransmissions are still unsuccessful
  702                          * with a lowered MTU, maybe this isn't a blackhole and
  703                          * we restore the previous MSS and blackhole detection
  704                          * flags.
  705                          * The limit '6' is determined by giving each probe
  706                          * stage (1448, 1188, 524) 2 chances to recover.
  707                          */
  708                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
  709                             (tp->t_rxtshift > 6)) {
  710                                 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
  711                                 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
  712                                 optlen = tp->t_maxopd - tp->t_maxseg;
  713                                 tp->t_maxopd = tp->t_pmtud_saved_maxopd;
  714                                 tp->t_maxseg = tp->t_maxopd - optlen;
  715                                 V_tcp_pmtud_blackhole_failed++;
  716                                 /*
  717                                  * Reset the slow-start flight size as it
  718                                  * may depend on the new MSS.
  719                                  */
  720                                 if (CC_ALGO(tp)->conn_init != NULL)
  721                                         CC_ALGO(tp)->conn_init(tp->ccv);
  722                         }
  723                 }
  724         }
  725 
  726         /*
  727          * Disable RFC1323 and SACK if we haven't got any response to
  728          * our third SYN to work-around some broken terminal servers
  729          * (most of which have hopefully been retired) that have bad VJ
  730          * header compression code which trashes TCP segments containing
  731          * unknown-to-them TCP options.
  732          */
  733         if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
  734             (tp->t_rxtshift == 3))
  735                 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
  736         /*
  737          * If we backed off this far, our srtt estimate is probably bogus.
  738          * Clobber it so we'll take the next rtt measurement as our srtt;
  739          * move the current srtt into rttvar to keep the current
  740          * retransmit times until then.
  741          */
  742         if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
  743 #ifdef INET6
  744                 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
  745                         in6_losing(tp->t_inpcb);
  746 #endif
  747                 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
  748                 tp->t_srtt = 0;
  749         }
  750         tp->snd_nxt = tp->snd_una;
  751         tp->snd_recover = tp->snd_max;
  752         /*
  753          * Force a segment to be sent.
  754          */
  755         tp->t_flags |= TF_ACKNOW;
  756         /*
  757          * If timing a segment in this window, stop the timer.
  758          */
  759         tp->t_rtttime = 0;
  760 
  761         cc_cong_signal(tp, NULL, CC_RTO);
  762 
  763         (void) tcp_output(tp);
  764 
  765 out:
  766 #ifdef TCPDEBUG
  767         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  768                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  769                           PRU_SLOWTIMO);
  770 #endif
  771         if (tp != NULL)
  772                 INP_WUNLOCK(inp);
  773         if (headlocked)
  774                 INP_INFO_WUNLOCK(&V_tcbinfo);
  775         CURVNET_RESTORE();
  776 }
  777 
  778 void
  779 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
  780 {
  781         struct callout *t_callout;
  782         timeout_t *f_callout;
  783         struct inpcb *inp = tp->t_inpcb;
  784         int cpu = INP_CPU(inp);
  785         uint32_t f_reset;
  786 
  787 #ifdef TCP_OFFLOAD
  788         if (tp->t_flags & TF_TOE)
  789                 return;
  790 #endif
  791 
  792         if (tp->t_timers->tt_flags & TT_STOPPED)
  793                 return;
  794 
  795         switch (timer_type) {
  796                 case TT_DELACK:
  797                         t_callout = &tp->t_timers->tt_delack;
  798                         f_callout = tcp_timer_delack;
  799                         f_reset = TT_DELACK_RST;
  800                         break;
  801                 case TT_REXMT:
  802                         t_callout = &tp->t_timers->tt_rexmt;
  803                         f_callout = tcp_timer_rexmt;
  804                         f_reset = TT_REXMT_RST;
  805                         break;
  806                 case TT_PERSIST:
  807                         t_callout = &tp->t_timers->tt_persist;
  808                         f_callout = tcp_timer_persist;
  809                         f_reset = TT_PERSIST_RST;
  810                         break;
  811                 case TT_KEEP:
  812                         t_callout = &tp->t_timers->tt_keep;
  813                         f_callout = tcp_timer_keep;
  814                         f_reset = TT_KEEP_RST;
  815                         break;
  816                 case TT_2MSL:
  817                         t_callout = &tp->t_timers->tt_2msl;
  818                         f_callout = tcp_timer_2msl;
  819                         f_reset = TT_2MSL_RST;
  820                         break;
  821                 default:
  822                         panic("tp %p bad timer_type %#x", tp, timer_type);
  823                 }
  824         if (delta == 0) {
  825                 if ((tp->t_timers->tt_flags & timer_type) &&
  826                     callout_stop(t_callout) &&
  827                     (tp->t_timers->tt_flags & f_reset)) {
  828                         tp->t_timers->tt_flags &= ~(timer_type | f_reset);
  829                 }
  830         } else {
  831                 if ((tp->t_timers->tt_flags & timer_type) == 0) {
  832                         tp->t_timers->tt_flags |= (timer_type | f_reset);
  833                         callout_reset_on(t_callout, delta, f_callout, tp, cpu);
  834                 } else {
  835                         /* Reset already running callout on the same CPU. */
  836                         if (!callout_reset(t_callout, delta, f_callout, tp)) {
  837                                 /*
  838                                  * Callout not cancelled, consider it as not
  839                                  * properly restarted. */
  840                                 tp->t_timers->tt_flags &= ~f_reset;
  841                         }
  842                 }
  843         }
  844 }
  845 
  846 int
  847 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
  848 {
  849         struct callout *t_callout;
  850 
  851         switch (timer_type) {
  852                 case TT_DELACK:
  853                         t_callout = &tp->t_timers->tt_delack;
  854                         break;
  855                 case TT_REXMT:
  856                         t_callout = &tp->t_timers->tt_rexmt;
  857                         break;
  858                 case TT_PERSIST:
  859                         t_callout = &tp->t_timers->tt_persist;
  860                         break;
  861                 case TT_KEEP:
  862                         t_callout = &tp->t_timers->tt_keep;
  863                         break;
  864                 case TT_2MSL:
  865                         t_callout = &tp->t_timers->tt_2msl;
  866                         break;
  867                 default:
  868                         panic("tp %p bad timer_type %#x", tp, timer_type);
  869                 }
  870         return callout_active(t_callout);
  871 }
  872 
  873 void
  874 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
  875 {
  876         struct callout *t_callout;
  877         timeout_t *f_callout;
  878         uint32_t f_reset;
  879 
  880         tp->t_timers->tt_flags |= TT_STOPPED;
  881 
  882         switch (timer_type) {
  883                 case TT_DELACK:
  884                         t_callout = &tp->t_timers->tt_delack;
  885                         f_callout = tcp_timer_delack_discard;
  886                         f_reset = TT_DELACK_RST;
  887                         break;
  888                 case TT_REXMT:
  889                         t_callout = &tp->t_timers->tt_rexmt;
  890                         f_callout = tcp_timer_rexmt_discard;
  891                         f_reset = TT_REXMT_RST;
  892                         break;
  893                 case TT_PERSIST:
  894                         t_callout = &tp->t_timers->tt_persist;
  895                         f_callout = tcp_timer_persist_discard;
  896                         f_reset = TT_PERSIST_RST;
  897                         break;
  898                 case TT_KEEP:
  899                         t_callout = &tp->t_timers->tt_keep;
  900                         f_callout = tcp_timer_keep_discard;
  901                         f_reset = TT_KEEP_RST;
  902                         break;
  903                 case TT_2MSL:
  904                         t_callout = &tp->t_timers->tt_2msl;
  905                         f_callout = tcp_timer_2msl_discard;
  906                         f_reset = TT_2MSL_RST;
  907                         break;
  908                 default:
  909                         panic("tp %p bad timer_type %#x", tp, timer_type);
  910                 }
  911 
  912         if (tp->t_timers->tt_flags & timer_type) {
  913                 if (callout_stop(t_callout) &&
  914                     (tp->t_timers->tt_flags & f_reset)) {
  915                         tp->t_timers->tt_flags &= ~(timer_type | f_reset);
  916                 } else {
  917                         /*
  918                          * Can't stop the callout, defer tcpcb actual deletion
  919                          * to the last tcp timer discard callout.
  920                          * The TT_STOPPED flag will ensure that no tcp timer
  921                          * callouts can be restarted on our behalf, and
  922                          * past this point currently running callouts waiting
  923                          * on inp lock will return right away after the
  924                          * classical check for callout reset/stop events:
  925                          * callout_pending() || !callout_active()
  926                          */
  927                         callout_reset(t_callout, 1, f_callout, tp);
  928                 }
  929         }
  930 }
  931 
  932 #define ticks_to_msecs(t)       (1000*(t) / hz)
  933 
  934 void
  935 tcp_timer_to_xtimer(struct tcpcb *tp, struct tcp_timer *timer,
  936     struct xtcp_timer *xtimer)
  937 {
  938         sbintime_t now;
  939 
  940         bzero(xtimer, sizeof(*xtimer));
  941         if (timer == NULL)
  942                 return;
  943         now = getsbinuptime();
  944         if (callout_active(&timer->tt_delack))
  945                 xtimer->tt_delack = (timer->tt_delack.c_time - now) / SBT_1MS;
  946         if (callout_active(&timer->tt_rexmt))
  947                 xtimer->tt_rexmt = (timer->tt_rexmt.c_time - now) / SBT_1MS;
  948         if (callout_active(&timer->tt_persist))
  949                 xtimer->tt_persist = (timer->tt_persist.c_time - now) / SBT_1MS;
  950         if (callout_active(&timer->tt_keep))
  951                 xtimer->tt_keep = (timer->tt_keep.c_time - now) / SBT_1MS;
  952         if (callout_active(&timer->tt_2msl))
  953                 xtimer->tt_2msl = (timer->tt_2msl.c_time - now) / SBT_1MS;
  954         xtimer->t_rcvtime = ticks_to_msecs(ticks - tp->t_rcvtime);
  955 }

Cache object: 5ed4ed8753e94c478eaea4f1d5815ada


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