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/11.2/sys/netinet/tcp_timer.c 332178 2018-04-07 15:16:57Z tuexen $");
   34 
   35 #include "opt_inet.h"
   36 #include "opt_inet6.h"
   37 #include "opt_tcpdebug.h"
   38 #include "opt_rss.h"
   39 
   40 #include <sys/param.h>
   41 #include <sys/kernel.h>
   42 #include <sys/lock.h>
   43 #include <sys/mbuf.h>
   44 #include <sys/mutex.h>
   45 #include <sys/protosw.h>
   46 #include <sys/smp.h>
   47 #include <sys/socket.h>
   48 #include <sys/socketvar.h>
   49 #include <sys/sysctl.h>
   50 #include <sys/systm.h>
   51 
   52 #include <net/if.h>
   53 #include <net/route.h>
   54 #include <net/rss_config.h>
   55 #include <net/vnet.h>
   56 #include <net/netisr.h>
   57 
   58 #include <netinet/in.h>
   59 #include <netinet/in_kdtrace.h>
   60 #include <netinet/in_pcb.h>
   61 #include <netinet/in_rss.h>
   62 #include <netinet/in_systm.h>
   63 #ifdef INET6
   64 #include <netinet6/in6_pcb.h>
   65 #endif
   66 #include <netinet/ip_var.h>
   67 #include <netinet/tcp.h>
   68 #include <netinet/tcp_fsm.h>
   69 #include <netinet/tcp_timer.h>
   70 #include <netinet/tcp_var.h>
   71 #include <netinet/cc/cc.h>
   72 #ifdef INET6
   73 #include <netinet6/tcp6_var.h>
   74 #endif
   75 #include <netinet/tcpip.h>
   76 #ifdef TCPDEBUG
   77 #include <netinet/tcp_debug.h>
   78 #endif
   79 
   80 int    tcp_persmin;
   81 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
   82     &tcp_persmin, 0, sysctl_msec_to_ticks, "I", "minimum persistence interval");
   83 
   84 int    tcp_persmax;
   85 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
   86     &tcp_persmax, 0, sysctl_msec_to_ticks, "I", "maximum persistence interval");
   87 
   88 int     tcp_keepinit;
   89 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
   90     &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
   91 
   92 int     tcp_keepidle;
   93 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
   94     &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
   95 
   96 int     tcp_keepintvl;
   97 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
   98     &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
   99 
  100 int     tcp_delacktime;
  101 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
  102     &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
  103     "Time before a delayed ACK is sent");
  104 
  105 int     tcp_msl;
  106 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
  107     &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
  108 
  109 int     tcp_rexmit_min;
  110 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
  111     &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
  112     "Minimum Retransmission Timeout");
  113 
  114 int     tcp_rexmit_slop;
  115 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
  116     &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
  117     "Retransmission Timer Slop");
  118 
  119 int     tcp_always_keepalive = 1;
  120 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
  121     &tcp_always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
  122 __strong_reference(tcp_always_keepalive, always_keepalive);
  123 
  124 int    tcp_fast_finwait2_recycle = 0;
  125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW, 
  126     &tcp_fast_finwait2_recycle, 0,
  127     "Recycle closed FIN_WAIT_2 connections faster");
  128 
  129 int    tcp_finwait2_timeout;
  130 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
  131     &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
  132 
  133 int     tcp_keepcnt = TCPTV_KEEPCNT;
  134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
  135     "Number of keepalive probes to send");
  136 
  137         /* max idle probes */
  138 int     tcp_maxpersistidle;
  139 
  140 static int      tcp_rexmit_drop_options = 0;
  141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
  142     &tcp_rexmit_drop_options, 0,
  143     "Drop TCP options from 3rd and later retransmitted SYN");
  144 
  145 static VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
  146 #define V_tcp_pmtud_blackhole_detect    VNET(tcp_pmtud_blackhole_detect)
  147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
  148     CTLFLAG_RW|CTLFLAG_VNET,
  149     &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
  150     "Path MTU Discovery Black Hole Detection Enabled");
  151 
  152 static VNET_DEFINE(int, tcp_pmtud_blackhole_activated);
  153 #define V_tcp_pmtud_blackhole_activated \
  154     VNET(tcp_pmtud_blackhole_activated)
  155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_activated,
  156     CTLFLAG_RD|CTLFLAG_VNET,
  157     &VNET_NAME(tcp_pmtud_blackhole_activated), 0,
  158     "Path MTU Discovery Black Hole Detection, Activation Count");
  159 
  160 static VNET_DEFINE(int, tcp_pmtud_blackhole_activated_min_mss);
  161 #define V_tcp_pmtud_blackhole_activated_min_mss \
  162     VNET(tcp_pmtud_blackhole_activated_min_mss)
  163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_activated_min_mss,
  164     CTLFLAG_RD|CTLFLAG_VNET,
  165     &VNET_NAME(tcp_pmtud_blackhole_activated_min_mss), 0,
  166     "Path MTU Discovery Black Hole Detection, Activation Count at min MSS");
  167 
  168 static VNET_DEFINE(int, tcp_pmtud_blackhole_failed);
  169 #define V_tcp_pmtud_blackhole_failed    VNET(tcp_pmtud_blackhole_failed)
  170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_failed,
  171     CTLFLAG_RD|CTLFLAG_VNET,
  172     &VNET_NAME(tcp_pmtud_blackhole_failed), 0,
  173     "Path MTU Discovery Black Hole Detection, Failure Count");
  174 
  175 #ifdef INET
  176 static VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
  177 #define V_tcp_pmtud_blackhole_mss       VNET(tcp_pmtud_blackhole_mss)
  178 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
  179     CTLFLAG_RW|CTLFLAG_VNET,
  180     &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
  181     "Path MTU Discovery Black Hole Detection lowered MSS");
  182 #endif
  183 
  184 #ifdef INET6
  185 static VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
  186 #define V_tcp_v6pmtud_blackhole_mss     VNET(tcp_v6pmtud_blackhole_mss)
  187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
  188     CTLFLAG_RW|CTLFLAG_VNET,
  189     &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
  190     "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
  191 #endif
  192 
  193 #ifdef  RSS
  194 static int      per_cpu_timers = 1;
  195 #else
  196 static int      per_cpu_timers = 0;
  197 #endif
  198 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
  199     &per_cpu_timers , 0, "run tcp timers on all cpus");
  200 
  201 #if 0
  202 #define INP_CPU(inp)    (per_cpu_timers ? (!CPU_ABSENT(((inp)->inp_flowid % (mp_maxid+1))) ? \
  203                 ((inp)->inp_flowid % (mp_maxid+1)) : curcpu) : 0)
  204 #endif
  205 
  206 /*
  207  * Map the given inp to a CPU id.
  208  *
  209  * This queries RSS if it's compiled in, else it defaults to the current
  210  * CPU ID.
  211  */
  212 static inline int
  213 inp_to_cpuid(struct inpcb *inp)
  214 {
  215         u_int cpuid;
  216 
  217 #ifdef  RSS
  218         if (per_cpu_timers) {
  219                 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
  220                 if (cpuid == NETISR_CPUID_NONE)
  221                         return (curcpu);        /* XXX */
  222                 else
  223                         return (cpuid);
  224         }
  225 #else
  226         /* Legacy, pre-RSS behaviour */
  227         if (per_cpu_timers) {
  228                 /*
  229                  * We don't have a flowid -> cpuid mapping, so cheat and
  230                  * just map unknown cpuids to curcpu.  Not the best, but
  231                  * apparently better than defaulting to swi 0.
  232                  */
  233                 cpuid = inp->inp_flowid % (mp_maxid + 1);
  234                 if (! CPU_ABSENT(cpuid))
  235                         return (cpuid);
  236                 return (curcpu);
  237         }
  238 #endif
  239         /* Default for RSS and non-RSS - cpuid 0 */
  240         else {
  241                 return (0);
  242         }
  243 }
  244 
  245 /*
  246  * Tcp protocol timeout routine called every 500 ms.
  247  * Updates timestamps used for TCP
  248  * causes finite state machine actions if timers expire.
  249  */
  250 void
  251 tcp_slowtimo(void)
  252 {
  253         VNET_ITERATOR_DECL(vnet_iter);
  254 
  255         VNET_LIST_RLOCK_NOSLEEP();
  256         VNET_FOREACH(vnet_iter) {
  257                 CURVNET_SET(vnet_iter);
  258                 (void) tcp_tw_2msl_scan(0);
  259                 CURVNET_RESTORE();
  260         }
  261         VNET_LIST_RUNLOCK_NOSLEEP();
  262 }
  263 
  264 int     tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
  265     { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
  266 
  267 int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
  268     { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
  269 
  270 static int tcp_totbackoff = 2559;       /* sum of tcp_backoff[] */
  271 
  272 /*
  273  * TCP timer processing.
  274  */
  275 
  276 void
  277 tcp_timer_delack(void *xtp)
  278 {
  279         struct tcpcb *tp = xtp;
  280         struct inpcb *inp;
  281         CURVNET_SET(tp->t_vnet);
  282 
  283         inp = tp->t_inpcb;
  284         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  285         INP_WLOCK(inp);
  286         if (callout_pending(&tp->t_timers->tt_delack) ||
  287             !callout_active(&tp->t_timers->tt_delack)) {
  288                 INP_WUNLOCK(inp);
  289                 CURVNET_RESTORE();
  290                 return;
  291         }
  292         callout_deactivate(&tp->t_timers->tt_delack);
  293         if ((inp->inp_flags & INP_DROPPED) != 0) {
  294                 INP_WUNLOCK(inp);
  295                 CURVNET_RESTORE();
  296                 return;
  297         }
  298         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  299                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  300         KASSERT((tp->t_timers->tt_flags & TT_DELACK) != 0,
  301                 ("%s: tp %p delack callout should be running", __func__, tp));
  302 
  303         tp->t_flags |= TF_ACKNOW;
  304         TCPSTAT_INC(tcps_delack);
  305         (void) tp->t_fb->tfb_tcp_output(tp);
  306         INP_WUNLOCK(inp);
  307         CURVNET_RESTORE();
  308 }
  309 
  310 void
  311 tcp_timer_2msl(void *xtp)
  312 {
  313         struct tcpcb *tp = xtp;
  314         struct inpcb *inp;
  315         CURVNET_SET(tp->t_vnet);
  316 #ifdef TCPDEBUG
  317         int ostate;
  318 
  319         ostate = tp->t_state;
  320 #endif
  321         INP_INFO_RLOCK(&V_tcbinfo);
  322         inp = tp->t_inpcb;
  323         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  324         INP_WLOCK(inp);
  325         tcp_free_sackholes(tp);
  326         if (callout_pending(&tp->t_timers->tt_2msl) ||
  327             !callout_active(&tp->t_timers->tt_2msl)) {
  328                 INP_WUNLOCK(tp->t_inpcb);
  329                 INP_INFO_RUNLOCK(&V_tcbinfo);
  330                 CURVNET_RESTORE();
  331                 return;
  332         }
  333         callout_deactivate(&tp->t_timers->tt_2msl);
  334         if ((inp->inp_flags & INP_DROPPED) != 0) {
  335                 INP_WUNLOCK(inp);
  336                 INP_INFO_RUNLOCK(&V_tcbinfo);
  337                 CURVNET_RESTORE();
  338                 return;
  339         }
  340         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  341                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  342         KASSERT((tp->t_timers->tt_flags & TT_2MSL) != 0,
  343                 ("%s: tp %p 2msl callout should be running", __func__, tp));
  344         /*
  345          * 2 MSL timeout in shutdown went off.  If we're closed but
  346          * still waiting for peer to close and connection has been idle
  347          * too long delete connection control block.  Otherwise, check
  348          * again in a bit.
  349          *
  350          * If in TIME_WAIT state just ignore as this timeout is handled in
  351          * tcp_tw_2msl_scan().
  352          *
  353          * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed, 
  354          * there's no point in hanging onto FIN_WAIT_2 socket. Just close it. 
  355          * Ignore fact that there were recent incoming segments.
  356          */
  357         if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
  358                 INP_WUNLOCK(inp);
  359                 INP_INFO_RUNLOCK(&V_tcbinfo);
  360                 CURVNET_RESTORE();
  361                 return;
  362         }
  363         if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
  364             tp->t_inpcb && tp->t_inpcb->inp_socket && 
  365             (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
  366                 TCPSTAT_INC(tcps_finwait2_drops);
  367                 tp = tcp_close(tp);             
  368         } else {
  369                 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
  370                         if (!callout_reset(&tp->t_timers->tt_2msl,
  371                            TP_KEEPINTVL(tp), tcp_timer_2msl, tp)) {
  372                                 tp->t_timers->tt_flags &= ~TT_2MSL_RST;
  373                         }
  374                 } else
  375                        tp = tcp_close(tp);
  376        }
  377 
  378 #ifdef TCPDEBUG
  379         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  380                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  381                           PRU_SLOWTIMO);
  382 #endif
  383         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
  384 
  385         if (tp != NULL)
  386                 INP_WUNLOCK(inp);
  387         INP_INFO_RUNLOCK(&V_tcbinfo);
  388         CURVNET_RESTORE();
  389 }
  390 
  391 void
  392 tcp_timer_keep(void *xtp)
  393 {
  394         struct tcpcb *tp = xtp;
  395         struct tcptemp *t_template;
  396         struct inpcb *inp;
  397         CURVNET_SET(tp->t_vnet);
  398 #ifdef TCPDEBUG
  399         int ostate;
  400 
  401         ostate = tp->t_state;
  402 #endif
  403         INP_INFO_RLOCK(&V_tcbinfo);
  404         inp = tp->t_inpcb;
  405         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  406         INP_WLOCK(inp);
  407         if (callout_pending(&tp->t_timers->tt_keep) ||
  408             !callout_active(&tp->t_timers->tt_keep)) {
  409                 INP_WUNLOCK(inp);
  410                 INP_INFO_RUNLOCK(&V_tcbinfo);
  411                 CURVNET_RESTORE();
  412                 return;
  413         }
  414         callout_deactivate(&tp->t_timers->tt_keep);
  415         if ((inp->inp_flags & INP_DROPPED) != 0) {
  416                 INP_WUNLOCK(inp);
  417                 INP_INFO_RUNLOCK(&V_tcbinfo);
  418                 CURVNET_RESTORE();
  419                 return;
  420         }
  421         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  422                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  423         KASSERT((tp->t_timers->tt_flags & TT_KEEP) != 0,
  424                 ("%s: tp %p keep callout should be running", __func__, tp));
  425         /*
  426          * Keep-alive timer went off; send something
  427          * or drop connection if idle for too long.
  428          */
  429         TCPSTAT_INC(tcps_keeptimeo);
  430         if (tp->t_state < TCPS_ESTABLISHED)
  431                 goto dropit;
  432         if ((tcp_always_keepalive ||
  433             inp->inp_socket->so_options & SO_KEEPALIVE) &&
  434             tp->t_state <= TCPS_CLOSING) {
  435                 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
  436                         goto dropit;
  437                 /*
  438                  * Send a packet designed to force a response
  439                  * if the peer is up and reachable:
  440                  * either an ACK if the connection is still alive,
  441                  * or an RST if the peer has closed the connection
  442                  * due to timeout or reboot.
  443                  * Using sequence number tp->snd_una-1
  444                  * causes the transmitted zero-length segment
  445                  * to lie outside the receive window;
  446                  * by the protocol spec, this requires the
  447                  * correspondent TCP to respond.
  448                  */
  449                 TCPSTAT_INC(tcps_keepprobe);
  450                 t_template = tcpip_maketemplate(inp);
  451                 if (t_template) {
  452                         tcp_respond(tp, t_template->tt_ipgen,
  453                                     &t_template->tt_t, (struct mbuf *)NULL,
  454                                     tp->rcv_nxt, tp->snd_una - 1, 0);
  455                         free(t_template, M_TEMP);
  456                 }
  457                 if (!callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
  458                     tcp_timer_keep, tp)) {
  459                         tp->t_timers->tt_flags &= ~TT_KEEP_RST;
  460                 }
  461         } else if (!callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
  462                     tcp_timer_keep, tp)) {
  463                         tp->t_timers->tt_flags &= ~TT_KEEP_RST;
  464                 }
  465 
  466 #ifdef TCPDEBUG
  467         if (inp->inp_socket->so_options & SO_DEBUG)
  468                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  469                           PRU_SLOWTIMO);
  470 #endif
  471         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
  472         INP_WUNLOCK(inp);
  473         INP_INFO_RUNLOCK(&V_tcbinfo);
  474         CURVNET_RESTORE();
  475         return;
  476 
  477 dropit:
  478         TCPSTAT_INC(tcps_keepdrops);
  479         tp = tcp_drop(tp, ETIMEDOUT);
  480 
  481 #ifdef TCPDEBUG
  482         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  483                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  484                           PRU_SLOWTIMO);
  485 #endif
  486         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
  487         if (tp != NULL)
  488                 INP_WUNLOCK(tp->t_inpcb);
  489         INP_INFO_RUNLOCK(&V_tcbinfo);
  490         CURVNET_RESTORE();
  491 }
  492 
  493 void
  494 tcp_timer_persist(void *xtp)
  495 {
  496         struct tcpcb *tp = xtp;
  497         struct inpcb *inp;
  498         CURVNET_SET(tp->t_vnet);
  499 #ifdef TCPDEBUG
  500         int ostate;
  501 
  502         ostate = tp->t_state;
  503 #endif
  504         INP_INFO_RLOCK(&V_tcbinfo);
  505         inp = tp->t_inpcb;
  506         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  507         INP_WLOCK(inp);
  508         if (callout_pending(&tp->t_timers->tt_persist) ||
  509             !callout_active(&tp->t_timers->tt_persist)) {
  510                 INP_WUNLOCK(inp);
  511                 INP_INFO_RUNLOCK(&V_tcbinfo);
  512                 CURVNET_RESTORE();
  513                 return;
  514         }
  515         callout_deactivate(&tp->t_timers->tt_persist);
  516         if ((inp->inp_flags & INP_DROPPED) != 0) {
  517                 INP_WUNLOCK(inp);
  518                 INP_INFO_RUNLOCK(&V_tcbinfo);
  519                 CURVNET_RESTORE();
  520                 return;
  521         }
  522         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  523                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  524         KASSERT((tp->t_timers->tt_flags & TT_PERSIST) != 0,
  525                 ("%s: tp %p persist callout should be running", __func__, tp));
  526         /*
  527          * Persistence timer into zero window.
  528          * Force a byte to be output, if possible.
  529          */
  530         TCPSTAT_INC(tcps_persisttimeo);
  531         /*
  532          * Hack: if the peer is dead/unreachable, we do not
  533          * time out if the window is closed.  After a full
  534          * backoff, drop the connection if the idle time
  535          * (no responses to probes) reaches the maximum
  536          * backoff that we would use if retransmitting.
  537          */
  538         if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
  539             (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
  540              ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
  541                 TCPSTAT_INC(tcps_persistdrop);
  542                 tp = tcp_drop(tp, ETIMEDOUT);
  543                 goto out;
  544         }
  545         /*
  546          * If the user has closed the socket then drop a persisting
  547          * connection after a much reduced timeout.
  548          */
  549         if (tp->t_state > TCPS_CLOSE_WAIT &&
  550             (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
  551                 TCPSTAT_INC(tcps_persistdrop);
  552                 tp = tcp_drop(tp, ETIMEDOUT);
  553                 goto out;
  554         }
  555         tcp_setpersist(tp);
  556         tp->t_flags |= TF_FORCEDATA;
  557         (void) tp->t_fb->tfb_tcp_output(tp);
  558         tp->t_flags &= ~TF_FORCEDATA;
  559 
  560 out:
  561 #ifdef TCPDEBUG
  562         if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
  563                 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
  564 #endif
  565         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
  566         if (tp != NULL)
  567                 INP_WUNLOCK(inp);
  568         INP_INFO_RUNLOCK(&V_tcbinfo);
  569         CURVNET_RESTORE();
  570 }
  571 
  572 void
  573 tcp_timer_rexmt(void * xtp)
  574 {
  575         struct tcpcb *tp = xtp;
  576         CURVNET_SET(tp->t_vnet);
  577         int rexmt;
  578         int headlocked;
  579         struct inpcb *inp;
  580 #ifdef TCPDEBUG
  581         int ostate;
  582 
  583         ostate = tp->t_state;
  584 #endif
  585 
  586         INP_INFO_RLOCK(&V_tcbinfo);
  587         inp = tp->t_inpcb;
  588         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
  589         INP_WLOCK(inp);
  590         if (callout_pending(&tp->t_timers->tt_rexmt) ||
  591             !callout_active(&tp->t_timers->tt_rexmt)) {
  592                 INP_WUNLOCK(inp);
  593                 INP_INFO_RUNLOCK(&V_tcbinfo);
  594                 CURVNET_RESTORE();
  595                 return;
  596         }
  597         callout_deactivate(&tp->t_timers->tt_rexmt);
  598         if ((inp->inp_flags & INP_DROPPED) != 0) {
  599                 INP_WUNLOCK(inp);
  600                 INP_INFO_RUNLOCK(&V_tcbinfo);
  601                 CURVNET_RESTORE();
  602                 return;
  603         }
  604         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
  605                 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
  606         KASSERT((tp->t_timers->tt_flags & TT_REXMT) != 0,
  607                 ("%s: tp %p rexmt callout should be running", __func__, tp));
  608         tcp_free_sackholes(tp);
  609         if (tp->t_fb->tfb_tcp_rexmit_tmr) {
  610                 /* The stack has a timer action too. */
  611                 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
  612         }
  613         /*
  614          * Retransmission timer went off.  Message has not
  615          * been acked within retransmit interval.  Back off
  616          * to a longer retransmit interval and retransmit one segment.
  617          */
  618         if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
  619                 tp->t_rxtshift = TCP_MAXRXTSHIFT;
  620                 TCPSTAT_INC(tcps_timeoutdrop);
  621 
  622                 tp = tcp_drop(tp, tp->t_softerror ?
  623                               tp->t_softerror : ETIMEDOUT);
  624                 headlocked = 1;
  625                 goto out;
  626         }
  627         INP_INFO_RUNLOCK(&V_tcbinfo);
  628         headlocked = 0;
  629         if (tp->t_state == TCPS_SYN_SENT) {
  630                 /*
  631                  * If the SYN was retransmitted, indicate CWND to be
  632                  * limited to 1 segment in cc_conn_init().
  633                  */
  634                 tp->snd_cwnd = 1;
  635         } else if (tp->t_rxtshift == 1) {
  636                 /*
  637                  * first retransmit; record ssthresh and cwnd so they can
  638                  * be recovered if this turns out to be a "bad" retransmit.
  639                  * A retransmit is considered "bad" if an ACK for this
  640                  * segment is received within RTT/2 interval; the assumption
  641                  * here is that the ACK was already in flight.  See
  642                  * "On Estimating End-to-End Network Path Properties" by
  643                  * Allman and Paxson for more details.
  644                  */
  645                 tp->snd_cwnd_prev = tp->snd_cwnd;
  646                 tp->snd_ssthresh_prev = tp->snd_ssthresh;
  647                 tp->snd_recover_prev = tp->snd_recover;
  648                 if (IN_FASTRECOVERY(tp->t_flags))
  649                         tp->t_flags |= TF_WASFRECOVERY;
  650                 else
  651                         tp->t_flags &= ~TF_WASFRECOVERY;
  652                 if (IN_CONGRECOVERY(tp->t_flags))
  653                         tp->t_flags |= TF_WASCRECOVERY;
  654                 else
  655                         tp->t_flags &= ~TF_WASCRECOVERY;
  656                 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
  657                 tp->t_flags |= TF_PREVVALID;
  658         } else
  659                 tp->t_flags &= ~TF_PREVVALID;
  660         TCPSTAT_INC(tcps_rexmttimeo);
  661         if ((tp->t_state == TCPS_SYN_SENT) ||
  662             (tp->t_state == TCPS_SYN_RECEIVED))
  663                 rexmt = TCPTV_RTOBASE * tcp_syn_backoff[tp->t_rxtshift];
  664         else
  665                 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
  666         TCPT_RANGESET(tp->t_rxtcur, rexmt,
  667                       tp->t_rttmin, TCPTV_REXMTMAX);
  668 
  669         /*
  670          * We enter the path for PLMTUD if connection is established or, if
  671          * connection is FIN_WAIT_1 status, reason for the last is that if
  672          * amount of data we send is very small, we could send it in couple of
  673          * packets and process straight to FIN. In that case we won't catch
  674          * ESTABLISHED state.
  675          */
  676         if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
  677             || (tp->t_state == TCPS_FIN_WAIT_1))) {
  678 #ifdef INET6
  679                 int isipv6;
  680 #endif
  681 
  682                 /*
  683                  * Idea here is that at each stage of mtu probe (usually, 1448
  684                  * -> 1188 -> 524) should be given 2 chances to recover before
  685                  *  further clamping down. 'tp->t_rxtshift % 2 == 0' should
  686                  *  take care of that.
  687                  */
  688                 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
  689                     (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
  690                     (tp->t_rxtshift >= 2 && tp->t_rxtshift < 6 &&
  691                     tp->t_rxtshift % 2 == 0)) {
  692                         /*
  693                          * Enter Path MTU Black-hole Detection mechanism:
  694                          * - Disable Path MTU Discovery (IP "DF" bit).
  695                          * - Reduce MTU to lower value than what we
  696                          *   negotiated with peer.
  697                          */
  698                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
  699                                 /* Record that we may have found a black hole. */
  700                                 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
  701                                 /* Keep track of previous MSS. */
  702                                 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
  703                         }
  704 
  705                         /* 
  706                          * Reduce the MSS to blackhole value or to the default
  707                          * in an attempt to retransmit.
  708                          */
  709 #ifdef INET6
  710                         isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
  711                         if (isipv6 &&
  712                             tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
  713                                 /* Use the sysctl tuneable blackhole MSS. */
  714                                 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
  715                                 V_tcp_pmtud_blackhole_activated++;
  716                         } else if (isipv6) {
  717                                 /* Use the default MSS. */
  718                                 tp->t_maxseg = V_tcp_v6mssdflt;
  719                                 /*
  720                                  * Disable Path MTU Discovery when we switch to
  721                                  * minmss.
  722                                  */
  723                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
  724                                 V_tcp_pmtud_blackhole_activated_min_mss++;
  725                         }
  726 #endif
  727 #if defined(INET6) && defined(INET)
  728                         else
  729 #endif
  730 #ifdef INET
  731                         if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) {
  732                                 /* Use the sysctl tuneable blackhole MSS. */
  733                                 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
  734                                 V_tcp_pmtud_blackhole_activated++;
  735                         } else {
  736                                 /* Use the default MSS. */
  737                                 tp->t_maxseg = V_tcp_mssdflt;
  738                                 /*
  739                                  * Disable Path MTU Discovery when we switch to
  740                                  * minmss.
  741                                  */
  742                                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
  743                                 V_tcp_pmtud_blackhole_activated_min_mss++;
  744                         }
  745 #endif
  746                         /*
  747                          * Reset the slow-start flight size
  748                          * as it may depend on the new MSS.
  749                          */
  750                         if (CC_ALGO(tp)->conn_init != NULL)
  751                                 CC_ALGO(tp)->conn_init(tp->ccv);
  752                 } else {
  753                         /*
  754                          * If further retransmissions are still unsuccessful
  755                          * with a lowered MTU, maybe this isn't a blackhole and
  756                          * we restore the previous MSS and blackhole detection
  757                          * flags.
  758                          * The limit '6' is determined by giving each probe
  759                          * stage (1448, 1188, 524) 2 chances to recover.
  760                          */
  761                         if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
  762                             (tp->t_rxtshift >= 6)) {
  763                                 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
  764                                 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
  765                                 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
  766                                 V_tcp_pmtud_blackhole_failed++;
  767                                 /*
  768                                  * Reset the slow-start flight size as it
  769                                  * may depend on the new MSS.
  770                                  */
  771                                 if (CC_ALGO(tp)->conn_init != NULL)
  772                                         CC_ALGO(tp)->conn_init(tp->ccv);
  773                         }
  774                 }
  775         }
  776 
  777         /*
  778          * Disable RFC1323 and SACK if we haven't got any response to
  779          * our third SYN to work-around some broken terminal servers
  780          * (most of which have hopefully been retired) that have bad VJ
  781          * header compression code which trashes TCP segments containing
  782          * unknown-to-them TCP options.
  783          */
  784         if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
  785             (tp->t_rxtshift == 3))
  786                 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
  787         /*
  788          * If we backed off this far, our srtt estimate is probably bogus.
  789          * Clobber it so we'll take the next rtt measurement as our srtt;
  790          * move the current srtt into rttvar to keep the current
  791          * retransmit times until then.
  792          */
  793         if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
  794 #ifdef INET6
  795                 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
  796                         in6_losing(tp->t_inpcb);
  797                 else
  798 #endif
  799                         in_losing(tp->t_inpcb);
  800                 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
  801                 tp->t_srtt = 0;
  802         }
  803         tp->snd_nxt = tp->snd_una;
  804         tp->snd_recover = tp->snd_max;
  805         /*
  806          * Force a segment to be sent.
  807          */
  808         tp->t_flags |= TF_ACKNOW;
  809         /*
  810          * If timing a segment in this window, stop the timer.
  811          */
  812         tp->t_rtttime = 0;
  813 
  814         cc_cong_signal(tp, NULL, CC_RTO);
  815 
  816         (void) tp->t_fb->tfb_tcp_output(tp);
  817 
  818 out:
  819 #ifdef TCPDEBUG
  820         if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
  821                 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
  822                           PRU_SLOWTIMO);
  823 #endif
  824         TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
  825         if (tp != NULL)
  826                 INP_WUNLOCK(inp);
  827         if (headlocked)
  828                 INP_INFO_RUNLOCK(&V_tcbinfo);
  829         CURVNET_RESTORE();
  830 }
  831 
  832 void
  833 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
  834 {
  835         struct callout *t_callout;
  836         timeout_t *f_callout;
  837         struct inpcb *inp = tp->t_inpcb;
  838         int cpu = inp_to_cpuid(inp);
  839         uint32_t f_reset;
  840 
  841 #ifdef TCP_OFFLOAD
  842         if (tp->t_flags & TF_TOE)
  843                 return;
  844 #endif
  845 
  846         if (tp->t_timers->tt_flags & TT_STOPPED)
  847                 return;
  848 
  849         switch (timer_type) {
  850                 case TT_DELACK:
  851                         t_callout = &tp->t_timers->tt_delack;
  852                         f_callout = tcp_timer_delack;
  853                         f_reset = TT_DELACK_RST;
  854                         break;
  855                 case TT_REXMT:
  856                         t_callout = &tp->t_timers->tt_rexmt;
  857                         f_callout = tcp_timer_rexmt;
  858                         f_reset = TT_REXMT_RST;
  859                         break;
  860                 case TT_PERSIST:
  861                         t_callout = &tp->t_timers->tt_persist;
  862                         f_callout = tcp_timer_persist;
  863                         f_reset = TT_PERSIST_RST;
  864                         break;
  865                 case TT_KEEP:
  866                         t_callout = &tp->t_timers->tt_keep;
  867                         f_callout = tcp_timer_keep;
  868                         f_reset = TT_KEEP_RST;
  869                         break;
  870                 case TT_2MSL:
  871                         t_callout = &tp->t_timers->tt_2msl;
  872                         f_callout = tcp_timer_2msl;
  873                         f_reset = TT_2MSL_RST;
  874                         break;
  875                 default:
  876                         if (tp->t_fb->tfb_tcp_timer_activate) {
  877                                 tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
  878                                 return;
  879                         }
  880                         panic("tp %p bad timer_type %#x", tp, timer_type);
  881                 }
  882         if (delta == 0) {
  883                 if ((tp->t_timers->tt_flags & timer_type) &&
  884                     (callout_stop(t_callout) > 0) &&
  885                     (tp->t_timers->tt_flags & f_reset)) {
  886                         tp->t_timers->tt_flags &= ~(timer_type | f_reset);
  887                 }
  888         } else {
  889                 if ((tp->t_timers->tt_flags & timer_type) == 0) {
  890                         tp->t_timers->tt_flags |= (timer_type | f_reset);
  891                         callout_reset_on(t_callout, delta, f_callout, tp, cpu);
  892                 } else {
  893                         /* Reset already running callout on the same CPU. */
  894                         if (!callout_reset(t_callout, delta, f_callout, tp)) {
  895                                 /*
  896                                  * Callout not cancelled, consider it as not
  897                                  * properly restarted. */
  898                                 tp->t_timers->tt_flags &= ~f_reset;
  899                         }
  900                 }
  901         }
  902 }
  903 
  904 int
  905 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
  906 {
  907         struct callout *t_callout;
  908 
  909         switch (timer_type) {
  910                 case TT_DELACK:
  911                         t_callout = &tp->t_timers->tt_delack;
  912                         break;
  913                 case TT_REXMT:
  914                         t_callout = &tp->t_timers->tt_rexmt;
  915                         break;
  916                 case TT_PERSIST:
  917                         t_callout = &tp->t_timers->tt_persist;
  918                         break;
  919                 case TT_KEEP:
  920                         t_callout = &tp->t_timers->tt_keep;
  921                         break;
  922                 case TT_2MSL:
  923                         t_callout = &tp->t_timers->tt_2msl;
  924                         break;
  925                 default:
  926                         if (tp->t_fb->tfb_tcp_timer_active) {
  927                                 return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
  928                         }
  929                         panic("tp %p bad timer_type %#x", tp, timer_type);
  930                 }
  931         return callout_active(t_callout);
  932 }
  933 
  934 void
  935 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
  936 {
  937         struct callout *t_callout;
  938         uint32_t f_reset;
  939 
  940         tp->t_timers->tt_flags |= TT_STOPPED;
  941 
  942         switch (timer_type) {
  943                 case TT_DELACK:
  944                         t_callout = &tp->t_timers->tt_delack;
  945                         f_reset = TT_DELACK_RST;
  946                         break;
  947                 case TT_REXMT:
  948                         t_callout = &tp->t_timers->tt_rexmt;
  949                         f_reset = TT_REXMT_RST;
  950                         break;
  951                 case TT_PERSIST:
  952                         t_callout = &tp->t_timers->tt_persist;
  953                         f_reset = TT_PERSIST_RST;
  954                         break;
  955                 case TT_KEEP:
  956                         t_callout = &tp->t_timers->tt_keep;
  957                         f_reset = TT_KEEP_RST;
  958                         break;
  959                 case TT_2MSL:
  960                         t_callout = &tp->t_timers->tt_2msl;
  961                         f_reset = TT_2MSL_RST;
  962                         break;
  963                 default:
  964                         if (tp->t_fb->tfb_tcp_timer_stop) {
  965                                 /* 
  966                                  * XXXrrs we need to look at this with the
  967                                  * stop case below (flags).
  968                                  */
  969                                 tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
  970                                 return;
  971                         }
  972                         panic("tp %p bad timer_type %#x", tp, timer_type);
  973                 }
  974 
  975         if (tp->t_timers->tt_flags & timer_type) {
  976                 if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
  977                         /*
  978                          * Can't stop the callout, defer tcpcb actual deletion
  979                          * to the last one. We do this using the async drain
  980                          * function and incrementing the count in 
  981                          */
  982                         tp->t_timers->tt_draincnt++;
  983                 }
  984         }
  985 }
  986 
  987 #define ticks_to_msecs(t)       (1000*(t) / hz)
  988 
  989 void
  990 tcp_timer_to_xtimer(struct tcpcb *tp, struct tcp_timer *timer,
  991     struct xtcp_timer *xtimer)
  992 {
  993         sbintime_t now;
  994 
  995         bzero(xtimer, sizeof(*xtimer));
  996         if (timer == NULL)
  997                 return;
  998         now = getsbinuptime();
  999         if (callout_active(&timer->tt_delack))
 1000                 xtimer->tt_delack = (timer->tt_delack.c_time - now) / SBT_1MS;
 1001         if (callout_active(&timer->tt_rexmt))
 1002                 xtimer->tt_rexmt = (timer->tt_rexmt.c_time - now) / SBT_1MS;
 1003         if (callout_active(&timer->tt_persist))
 1004                 xtimer->tt_persist = (timer->tt_persist.c_time - now) / SBT_1MS;
 1005         if (callout_active(&timer->tt_keep))
 1006                 xtimer->tt_keep = (timer->tt_keep.c_time - now) / SBT_1MS;
 1007         if (callout_active(&timer->tt_2msl))
 1008                 xtimer->tt_2msl = (timer->tt_2msl.c_time - now) / SBT_1MS;
 1009         xtimer->t_rcvtime = ticks_to_msecs(ticks - tp->t_rcvtime);
 1010 }

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