tcp_timer.c

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/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_tcpdebug.h"
#include "opt_rss.h"
 
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/mutex.h>
#include <sys/protosw.h>
#include <sys/smp.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
 
#include <net/if.h>
#include <net/route.h>
#include <net/rss_config.h>
#include <net/vnet.h>
#include <net/netisr.h>
 
#include <netinet/in.h>
#include <netinet/in_kdtrace.h>
#include <netinet/in_pcb.h>
#include <netinet/in_rss.h>
#include <netinet/in_systm.h>
#ifdef INET6
#include <netinet6/in6_pcb.h>
#endif
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_log_buf.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcp_seq.h>
#include <netinet/cc/cc.h>
#ifdef INET6
#include <netinet6/tcp6_var.h>
#endif
#include <netinet/tcpip.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif
 
int    tcp_persmin;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_persmin, 0, sysctl_msec_to_ticks, "I",
    "minimum persistence interval");
 
int    tcp_persmax;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_persmax, 0, sysctl_msec_to_ticks, "I",
    "maximum persistence interval");
 
int     tcp_keepinit;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_keepinit, 0, sysctl_msec_to_ticks, "I",
    "time to establish connection");
 
int     tcp_keepidle;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_keepidle, 0, sysctl_msec_to_ticks, "I",
    "time before keepalive probes begin");
 
int     tcp_keepintvl;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I",
    "time between keepalive probes");
 
int     tcp_delacktime;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
    "Time before a delayed ACK is sent");
 
VNET_DEFINE(int, tcp_msl);
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_VNET,
    &VNET_NAME(tcp_msl), 0, sysctl_msec_to_ticks, "I",
    "Maximum segment lifetime");
 
int     tcp_rexmit_initial;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial,
   CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
    "Initial Retransmission Timeout");
 
int     tcp_rexmit_min;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
    "Minimum Retransmission Timeout");
 
int     tcp_rexmit_slop;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
    "Retransmission Timer Slop");
 
VNET_DEFINE(int, tcp_always_keepalive) = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW,
    &VNET_NAME(tcp_always_keepalive) , 0,
    "Assume SO_KEEPALIVE on all TCP connections");
 
int    tcp_fast_finwait2_recycle = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
    &tcp_fast_finwait2_recycle, 0,
    "Recycle closed FIN_WAIT_2 connections faster");
 
int    tcp_finwait2_timeout;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
    &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I",
    "FIN-WAIT2 timeout");
 
int     tcp_keepcnt = TCPTV_KEEPCNT;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
    "Number of keepalive probes to send");
 
        /* max idle probes */
int     tcp_maxpersistidle;
 
int     tcp_rexmit_drop_options = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
    &tcp_rexmit_drop_options, 0,
    "Drop TCP options from 3rd and later retransmitted SYN");
 
VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
    CTLFLAG_RW|CTLFLAG_VNET,
    &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
    "Path MTU Discovery Black Hole Detection Enabled");
 
#ifdef INET
VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
    CTLFLAG_RW|CTLFLAG_VNET,
    &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
    "Path MTU Discovery Black Hole Detection lowered MSS");
#endif
 
#ifdef INET6
VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
    CTLFLAG_RW|CTLFLAG_VNET,
    &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
    "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
#endif
 
#ifdef  RSS
static int      per_cpu_timers = 1;
#else
static int      per_cpu_timers = 0;
#endif
SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
    &per_cpu_timers , 0, "run tcp timers on all cpus");
 
/*
 * Map the given inp to a CPU id.
 *
 * This queries RSS if it's compiled in, else it defaults to the current
 * CPU ID.
 */
inline int
inp_to_cpuid(struct inpcb *inp)
{
        u_int cpuid;
 
        if (per_cpu_timers) {
#ifdef  RSS
                cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
                if (cpuid == NETISR_CPUID_NONE)
                        return (curcpu);        /* XXX */
                else
                        return (cpuid);
#endif
                /*
                 * We don't have a flowid -> cpuid mapping, so cheat and
                 * just map unknown cpuids to curcpu.  Not the best, but
                 * apparently better than defaulting to swi 0.
                 */
                cpuid = inp->inp_flowid % (mp_maxid + 1);
                if (! CPU_ABSENT(cpuid))
                        return (cpuid);
                return (curcpu);
        } else {
                return (0);
        }
}
 
/*
 * Tcp protocol timeout routine called every 500 ms.
 * Updates timestamps used for TCP
 * causes finite state machine actions if timers expire.
 */
void
tcp_slowtimo(void)
{
        VNET_ITERATOR_DECL(vnet_iter);
 
        VNET_LIST_RLOCK_NOSLEEP();
        VNET_FOREACH(vnet_iter) {
                CURVNET_SET(vnet_iter);
                (void) tcp_tw_2msl_scan(0);
                CURVNET_RESTORE();
        }
        VNET_LIST_RUNLOCK_NOSLEEP();
}
 
int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
    { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
 
int tcp_totbackoff = 2559;      /* sum of tcp_backoff[] */
 
/*
 * TCP timer processing.
 */
 
void
tcp_timer_delack(void *xtp)
{
        struct epoch_tracker et;
        struct tcpcb *tp = xtp;
        struct inpcb *inp;
        CURVNET_SET(tp->t_vnet);
 
        inp = tp->t_inpcb;
        KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
        INP_WLOCK(inp);
        if (callout_pending(&tp->t_timers->tt_delack) ||
            !callout_active(&tp->t_timers->tt_delack)) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        callout_deactivate(&tp->t_timers->tt_delack);
        if ((inp->inp_flags & INP_DROPPED) != 0) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        tp->t_flags |= TF_ACKNOW;
        TCPSTAT_INC(tcps_delack);
        NET_EPOCH_ENTER(et);
        (void) tcp_output_unlock(tp);
        NET_EPOCH_EXIT(et);
        CURVNET_RESTORE();
}
 
void
tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
{
        if (inp && tp != NULL)
                INP_WUNLOCK(inp);
}
 
void
tcp_timer_2msl(void *xtp)
{
        struct tcpcb *tp = xtp;
        struct inpcb *inp;
        struct epoch_tracker et;
        CURVNET_SET(tp->t_vnet);
#ifdef TCPDEBUG
        int ostate;
 
        ostate = tp->t_state;
#endif
        inp = tp->t_inpcb;
        KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
        INP_WLOCK(inp);
        tcp_free_sackholes(tp);
        if (callout_pending(&tp->t_timers->tt_2msl) ||
            !callout_active(&tp->t_timers->tt_2msl)) {
                INP_WUNLOCK(tp->t_inpcb);
                CURVNET_RESTORE();
                return;
        }
        callout_deactivate(&tp->t_timers->tt_2msl);
        if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
                ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
        /*
         * 2 MSL timeout in shutdown went off.  If we're closed but
         * still waiting for peer to close and connection has been idle
         * too long delete connection control block.  Otherwise, check
         * again in a bit.
         *
         * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
         * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
         * Ignore fact that there were recent incoming segments.
         */
        if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
            tp->t_inpcb && tp->t_inpcb->inp_socket &&
            (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
                TCPSTAT_INC(tcps_finwait2_drops);
                NET_EPOCH_ENTER(et);
                tp = tcp_close(tp);
                NET_EPOCH_EXIT(et);
                tcp_inpinfo_lock_del(inp, tp);
                goto out;
        } else {
                if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
                        callout_reset(&tp->t_timers->tt_2msl,
                                      TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
                } else {
                        NET_EPOCH_ENTER(et);
                        tp = tcp_close(tp);
                        NET_EPOCH_EXIT(et);
                        tcp_inpinfo_lock_del(inp, tp);
                        goto out;
                }
        }
 
#ifdef TCPDEBUG
        if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
                tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
                          PRU_SLOWTIMO);
#endif
        TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
 
        if (tp != NULL)
                INP_WUNLOCK(inp);
out:
        CURVNET_RESTORE();
}
 
void
tcp_timer_keep(void *xtp)
{
        struct tcpcb *tp = xtp;
        struct tcptemp *t_template;
        struct inpcb *inp;
        struct epoch_tracker et;
        CURVNET_SET(tp->t_vnet);
#ifdef TCPDEBUG
        int ostate;
 
        ostate = tp->t_state;
#endif
        inp = tp->t_inpcb;
        KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
        INP_WLOCK(inp);
        if (callout_pending(&tp->t_timers->tt_keep) ||
            !callout_active(&tp->t_timers->tt_keep)) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        callout_deactivate(&tp->t_timers->tt_keep);
        if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
                ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
 
        /*
         * Because we don't regularly reset the keepalive callout in
         * the ESTABLISHED state, it may be that we don't actually need
         * to send a keepalive yet. If that occurs, schedule another
         * call for the next time the keepalive timer might expire.
         */
        if (TCPS_HAVEESTABLISHED(tp->t_state)) {
                u_int idletime;
 
                idletime = ticks - tp->t_rcvtime;
                if (idletime < TP_KEEPIDLE(tp)) {
                        callout_reset(&tp->t_timers->tt_keep,
                            TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
                        INP_WUNLOCK(inp);
                        CURVNET_RESTORE();
                        return;
                }
        }
 
        /*
         * Keep-alive timer went off; send something
         * or drop connection if idle for too long.
         */
        TCPSTAT_INC(tcps_keeptimeo);
        if (tp->t_state < TCPS_ESTABLISHED)
                goto dropit;
        if ((V_tcp_always_keepalive ||
            inp->inp_socket->so_options & SO_KEEPALIVE) &&
            tp->t_state <= TCPS_CLOSING) {
                if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
                        goto dropit;
                /*
                 * Send a packet designed to force a response
                 * if the peer is up and reachable:
                 * either an ACK if the connection is still alive,
                 * or an RST if the peer has closed the connection
                 * due to timeout or reboot.
                 * Using sequence number tp->snd_una-1
                 * causes the transmitted zero-length segment
                 * to lie outside the receive window;
                 * by the protocol spec, this requires the
                 * correspondent TCP to respond.
                 */
                TCPSTAT_INC(tcps_keepprobe);
                t_template = tcpip_maketemplate(inp);
                if (t_template) {
                        NET_EPOCH_ENTER(et);
                        tcp_respond(tp, t_template->tt_ipgen,
                                    &t_template->tt_t, (struct mbuf *)NULL,
                                    tp->rcv_nxt, tp->snd_una - 1, 0);
                        NET_EPOCH_EXIT(et);
                        free(t_template, M_TEMP);
                }
                callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
                              tcp_timer_keep, tp);
        } else
                callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
                              tcp_timer_keep, tp);
 
#ifdef TCPDEBUG
        if (inp->inp_socket->so_options & SO_DEBUG)
                tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
                          PRU_SLOWTIMO);
#endif
        TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
        INP_WUNLOCK(inp);
        CURVNET_RESTORE();
        return;
 
dropit:
        TCPSTAT_INC(tcps_keepdrops);
        NET_EPOCH_ENTER(et);
        tp = tcp_drop(tp, ETIMEDOUT);
 
#ifdef TCPDEBUG
        if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
                tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
                          PRU_SLOWTIMO);
#endif
        TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
        NET_EPOCH_EXIT(et);
        tcp_inpinfo_lock_del(inp, tp);
        CURVNET_RESTORE();
}
 
void
tcp_timer_persist(void *xtp)
{
        struct tcpcb *tp = xtp;
        struct inpcb *inp;
        struct epoch_tracker et;
        int outrv;
        CURVNET_SET(tp->t_vnet);
#ifdef TCPDEBUG
        int ostate;
 
        ostate = tp->t_state;
#endif
        inp = tp->t_inpcb;
        KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
        INP_WLOCK(inp);
        if (callout_pending(&tp->t_timers->tt_persist) ||
            !callout_active(&tp->t_timers->tt_persist)) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        callout_deactivate(&tp->t_timers->tt_persist);
        if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
                ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
        /*
         * Persistence timer into zero window.
         * Force a byte to be output, if possible.
         */
        TCPSTAT_INC(tcps_persisttimeo);
        /*
         * Hack: if the peer is dead/unreachable, we do not
         * time out if the window is closed.  After a full
         * backoff, drop the connection if the idle time
         * (no responses to probes) reaches the maximum
         * backoff that we would use if retransmitting.
         */
        if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
            (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
             ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
                TCPSTAT_INC(tcps_persistdrop);
                NET_EPOCH_ENTER(et);
                tp = tcp_drop(tp, ETIMEDOUT);
                NET_EPOCH_EXIT(et);
                tcp_inpinfo_lock_del(inp, tp);
                goto out;
        }
        /*
         * If the user has closed the socket then drop a persisting
         * connection after a much reduced timeout.
         */
        if (tp->t_state > TCPS_CLOSE_WAIT &&
            (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
                TCPSTAT_INC(tcps_persistdrop);
                NET_EPOCH_ENTER(et);
                tp = tcp_drop(tp, ETIMEDOUT);
                NET_EPOCH_EXIT(et);
                tcp_inpinfo_lock_del(inp, tp);
                goto out;
        }
        tcp_setpersist(tp);
        tp->t_flags |= TF_FORCEDATA;
        NET_EPOCH_ENTER(et);
        outrv = tcp_output_nodrop(tp);
        tp->t_flags &= ~TF_FORCEDATA;
 
#ifdef TCPDEBUG
        if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
                tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
#endif
        TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
        (void) tcp_unlock_or_drop(tp, outrv);
        NET_EPOCH_EXIT(et);
out:
        CURVNET_RESTORE();
}
 
void
tcp_timer_rexmt(void * xtp)
{
        struct tcpcb *tp = xtp;
        CURVNET_SET(tp->t_vnet);
        int rexmt, outrv;
        struct inpcb *inp;
        struct epoch_tracker et;
        bool isipv6;
#ifdef TCPDEBUG
        int ostate;
 
        ostate = tp->t_state;
#endif
        inp = tp->t_inpcb;
        KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
        INP_WLOCK(inp);
        if (callout_pending(&tp->t_timers->tt_rexmt) ||
            !callout_active(&tp->t_timers->tt_rexmt)) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        callout_deactivate(&tp->t_timers->tt_rexmt);
        if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
                INP_WUNLOCK(inp);
                CURVNET_RESTORE();
                return;
        }
        KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
                ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
        tcp_free_sackholes(tp);
        TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false);
        if (tp->t_fb->tfb_tcp_rexmit_tmr) {
                /* The stack has a timer action too. */
                (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
        }
        /*
         * Retransmission timer went off.  Message has not
         * been acked within retransmit interval.  Back off
         * to a longer retransmit interval and retransmit one segment.
         */
        if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
                tp->t_rxtshift = TCP_MAXRXTSHIFT;
                TCPSTAT_INC(tcps_timeoutdrop);
                NET_EPOCH_ENTER(et);
                tp = tcp_drop(tp, ETIMEDOUT);
                NET_EPOCH_EXIT(et);
                tcp_inpinfo_lock_del(inp, tp);
                goto out;
        }
        if (tp->t_state == TCPS_SYN_SENT) {
                /*
                 * If the SYN was retransmitted, indicate CWND to be
                 * limited to 1 segment in cc_conn_init().
                 */
                tp->snd_cwnd = 1;
        } else if (tp->t_rxtshift == 1) {
                /*
                 * first retransmit; record ssthresh and cwnd so they can
                 * be recovered if this turns out to be a "bad" retransmit.
                 * A retransmit is considered "bad" if an ACK for this
                 * segment is received within RTT/2 interval; the assumption
                 * here is that the ACK was already in flight.  See
                 * "On Estimating End-to-End Network Path Properties" by
                 * Allman and Paxson for more details.
                 */
                tp->snd_cwnd_prev = tp->snd_cwnd;
                tp->snd_ssthresh_prev = tp->snd_ssthresh;
                tp->snd_recover_prev = tp->snd_recover;
                if (IN_FASTRECOVERY(tp->t_flags))
                        tp->t_flags |= TF_WASFRECOVERY;
                else
                        tp->t_flags &= ~TF_WASFRECOVERY;
                if (IN_CONGRECOVERY(tp->t_flags))
                        tp->t_flags |= TF_WASCRECOVERY;
                else
                        tp->t_flags &= ~TF_WASCRECOVERY;
                if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
                        tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
                /* In the event that we've negotiated timestamps
                 * badrxtwin will be set to the value that we set
                 * the retransmitted packet's to_tsval to by tcp_output
                 */
                tp->t_flags |= TF_PREVVALID;
        } else
                tp->t_flags &= ~TF_PREVVALID;
        TCPSTAT_INC(tcps_rexmttimeo);
        if ((tp->t_state == TCPS_SYN_SENT) ||
            (tp->t_state == TCPS_SYN_RECEIVED))
                rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
        else
                rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
        TCPT_RANGESET(tp->t_rxtcur, rexmt,
                      tp->t_rttmin, TCPTV_REXMTMAX);
 
        /*
         * We enter the path for PLMTUD if connection is established or, if
         * connection is FIN_WAIT_1 status, reason for the last is that if
         * amount of data we send is very small, we could send it in couple of
         * packets and process straight to FIN. In that case we won't catch
         * ESTABLISHED state.
         */
#ifdef INET6
        isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? true : false;
#else
        isipv6 = false;
#endif
        if (((V_tcp_pmtud_blackhole_detect == 1) ||
            (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
            (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
            ((tp->t_state == TCPS_ESTABLISHED) ||
            (tp->t_state == TCPS_FIN_WAIT_1))) {
                if (tp->t_rxtshift == 1) {
                        /*
                         * We enter blackhole detection after the first
                         * unsuccessful timer based retransmission.
                         * Then we reduce up to two times the MSS, each
                         * candidate giving two tries of retransmissions.
                         * But we give a candidate only two tries, if it
                         * actually reduces the MSS.
                         */
                        tp->t_blackhole_enter = 2;
                        tp->t_blackhole_exit = tp->t_blackhole_enter;
                        if (isipv6) {
#ifdef INET6
                                if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss)
                                        tp->t_blackhole_exit += 2;
                                if (tp->t_maxseg > V_tcp_v6mssdflt &&
                                    V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt)
                                        tp->t_blackhole_exit += 2;
#endif
                        } else {
#ifdef INET
                                if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss)
                                        tp->t_blackhole_exit += 2;
                                if (tp->t_maxseg > V_tcp_mssdflt &&
                                    V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt)
                                        tp->t_blackhole_exit += 2;
#endif
                        }
                }
                if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
                    (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
                    (tp->t_rxtshift >= tp->t_blackhole_enter &&
                    tp->t_rxtshift < tp->t_blackhole_exit &&
                    (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) {
                        /*
                         * Enter Path MTU Black-hole Detection mechanism:
                         * - Disable Path MTU Discovery (IP "DF" bit).
                         * - Reduce MTU to lower value than what we
                         *   negotiated with peer.
                         */
                        if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
                                /* Record that we may have found a black hole. */
                                tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
                                /* Keep track of previous MSS. */
                                tp->t_pmtud_saved_maxseg = tp->t_maxseg;
                        }
 
                        /*
                         * Reduce the MSS to blackhole value or to the default
                         * in an attempt to retransmit.
                         */
#ifdef INET6
                        if (isipv6 &&
                            tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss &&
                            V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) {
                                /* Use the sysctl tuneable blackhole MSS. */
                                tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
                                TCPSTAT_INC(tcps_pmtud_blackhole_activated);
                        } else if (isipv6) {
                                /* Use the default MSS. */
                                tp->t_maxseg = V_tcp_v6mssdflt;
                                /*
                                 * Disable Path MTU Discovery when we switch to
                                 * minmss.
                                 */
                                tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
                                TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
                        }
#endif
#if defined(INET6) && defined(INET)
                        else
#endif
#ifdef INET
                        if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss &&
                            V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) {
                                /* Use the sysctl tuneable blackhole MSS. */
                                tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
                                TCPSTAT_INC(tcps_pmtud_blackhole_activated);
                        } else {
                                /* Use the default MSS. */
                                tp->t_maxseg = V_tcp_mssdflt;
                                /*
                                 * Disable Path MTU Discovery when we switch to
                                 * minmss.
                                 */
                                tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
                                TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
                        }
#endif
                        /*
                         * Reset the slow-start flight size
                         * as it may depend on the new MSS.
                         */
                        if (CC_ALGO(tp)->conn_init != NULL)
                                CC_ALGO(tp)->conn_init(tp->ccv);
                } else {
                        /*
                         * If further retransmissions are still unsuccessful
                         * with a lowered MTU, maybe this isn't a blackhole and
                         * we restore the previous MSS and blackhole detection
                         * flags.
                         */
                        if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
                            (tp->t_rxtshift >= tp->t_blackhole_exit)) {
                                tp->t_flags2 |= TF2_PLPMTU_PMTUD;
                                tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
                                tp->t_maxseg = tp->t_pmtud_saved_maxseg;
                                TCPSTAT_INC(tcps_pmtud_blackhole_failed);
                                /*
                                 * Reset the slow-start flight size as it
                                 * may depend on the new MSS.
                                 */
                                if (CC_ALGO(tp)->conn_init != NULL)
                                        CC_ALGO(tp)->conn_init(tp->ccv);
                        }
                }
        }
 
        /*
         * Disable RFC1323 and SACK if we haven't got any response to
         * our third SYN to work-around some broken terminal servers
         * (most of which have hopefully been retired) that have bad VJ
         * header compression code which trashes TCP segments containing
         * unknown-to-them TCP options.
         */
        if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
            (tp->t_rxtshift == 3))
                tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
        /*
         * If we backed off this far, notify the L3 protocol that we're having
         * connection problems.
         */
        if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
#ifdef INET6
                if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
                        in6_losing(tp->t_inpcb);
                else
#endif
                        in_losing(tp->t_inpcb);
        }
        tp->snd_nxt = tp->snd_una;
        tp->snd_recover = tp->snd_max;
        /*
         * Force a segment to be sent.
         */
        tp->t_flags |= TF_ACKNOW;
        /*
         * If timing a segment in this window, stop the timer.
         */
        tp->t_rtttime = 0;
 
        cc_cong_signal(tp, NULL, CC_RTO);
        NET_EPOCH_ENTER(et);
        outrv = tcp_output_nodrop(tp);
#ifdef TCPDEBUG
        if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
                tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
                          PRU_SLOWTIMO);
#endif
        TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
        (void) tcp_unlock_or_drop(tp, outrv);
        NET_EPOCH_EXIT(et);
out:
        CURVNET_RESTORE();
}
 
void
tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
{
        struct callout *t_callout;
        callout_func_t *f_callout;
        struct inpcb *inp = tp->t_inpcb;
        int cpu = inp_to_cpuid(inp);
 
#ifdef TCP_OFFLOAD
        if (tp->t_flags & TF_TOE)
                return;
#endif
 
        if (tp->t_timers->tt_flags & TT_STOPPED)
                return;
 
        switch (timer_type) {
                case TT_DELACK:
                        t_callout = &tp->t_timers->tt_delack;
                        f_callout = tcp_timer_delack;
                        break;
                case TT_REXMT:
                        t_callout = &tp->t_timers->tt_rexmt;
                        f_callout = tcp_timer_rexmt;
                        break;
                case TT_PERSIST:
                        t_callout = &tp->t_timers->tt_persist;
                        f_callout = tcp_timer_persist;
                        break;
                case TT_KEEP:
                        t_callout = &tp->t_timers->tt_keep;
                        f_callout = tcp_timer_keep;
                        break;
                case TT_2MSL:
                        t_callout = &tp->t_timers->tt_2msl;
                        f_callout = tcp_timer_2msl;
                        break;
                default:
                        if (tp->t_fb->tfb_tcp_timer_activate) {
                                tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
                                return;
                        }
                        panic("tp %p bad timer_type %#x", tp, timer_type);
                }
        if (delta == 0) {
                callout_stop(t_callout);
        } else {
                callout_reset_on(t_callout, delta, f_callout, tp, cpu);
        }
}
 
int
tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
{
        struct callout *t_callout;
 
        switch (timer_type) {
                case TT_DELACK:
                        t_callout = &tp->t_timers->tt_delack;
                        break;
                case TT_REXMT:
                        t_callout = &tp->t_timers->tt_rexmt;
                        break;
                case TT_PERSIST:
                        t_callout = &tp->t_timers->tt_persist;
                        break;
                case TT_KEEP:
                        t_callout = &tp->t_timers->tt_keep;
                        break;
                case TT_2MSL:
                        t_callout = &tp->t_timers->tt_2msl;
                        break;
                default:
                        if (tp->t_fb->tfb_tcp_timer_active) {
                                return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
                        }
                        panic("tp %p bad timer_type %#x", tp, timer_type);
                }
        return callout_active(t_callout);
}
 
/*
 * Stop the timer from running, and apply a flag
 * against the timer_flags that will force the
 * timer never to run. The flag is needed to assure
 * a race does not leave it running and cause
 * the timer to possibly restart itself (keep and persist
 * especially do this).
 */
int
tcp_timer_suspend(struct tcpcb *tp, uint32_t timer_type)
{
        struct callout *t_callout;
        uint32_t t_flags;
 
        switch (timer_type) {
                case TT_DELACK:
                        t_flags = TT_DELACK_SUS;
                        t_callout = &tp->t_timers->tt_delack;
                        break;
                case TT_REXMT:
                        t_flags = TT_REXMT_SUS;
                        t_callout = &tp->t_timers->tt_rexmt;
                        break;
                case TT_PERSIST:
                        t_flags = TT_PERSIST_SUS;
                        t_callout = &tp->t_timers->tt_persist;
                        break;
                case TT_KEEP:
                        t_flags = TT_KEEP_SUS;
                        t_callout = &tp->t_timers->tt_keep;
                        break;
                case TT_2MSL:
                        t_flags = TT_2MSL_SUS;
                        t_callout = &tp->t_timers->tt_2msl;
                        break;
                default:
                        panic("tp:%p bad timer_type 0x%x", tp, timer_type);
        }
        tp->t_timers->tt_flags |= t_flags;
        return (callout_stop(t_callout));
}
 
void
tcp_timers_unsuspend(struct tcpcb *tp, uint32_t timer_type)
{
        switch (timer_type) {
                case TT_DELACK:
                        if (tp->t_timers->tt_flags & TT_DELACK_SUS) {
                                tp->t_timers->tt_flags &= ~TT_DELACK_SUS;
                                if (tp->t_flags & TF_DELACK) {
                                        /* Delayed ack timer should be up activate a timer */
                                        tp->t_flags &= ~TF_DELACK;
                                        tcp_timer_activate(tp, TT_DELACK,
                                            tcp_delacktime);
                                }
                        }
                        break;
                case TT_REXMT:
                        if (tp->t_timers->tt_flags & TT_REXMT_SUS) {
                                tp->t_timers->tt_flags &= ~TT_REXMT_SUS;
                                if (SEQ_GT(tp->snd_max, tp->snd_una) &&
                                    (tcp_timer_active((tp), TT_PERSIST) == 0) &&
                                    tp->snd_wnd) {
                                        /* We have outstanding data activate a timer */
                                        tcp_timer_activate(tp, TT_REXMT,
                                            tp->t_rxtcur);
                                }
                        }
                        break;
                case TT_PERSIST:
                        if (tp->t_timers->tt_flags & TT_PERSIST_SUS) {
                                tp->t_timers->tt_flags &= ~TT_PERSIST_SUS;
                                if (tp->snd_wnd == 0) {
                                        /* Activate the persists timer */
                                        tp->t_rxtshift = 0;
                                        tcp_setpersist(tp);
                                }
                        }
                        break;
                case TT_KEEP:
                        if (tp->t_timers->tt_flags & TT_KEEP_SUS) {
                                tp->t_timers->tt_flags &= ~TT_KEEP_SUS;
                                tcp_timer_activate(tp, TT_KEEP,
                                            TCPS_HAVEESTABLISHED(tp->t_state) ?
                                            TP_KEEPIDLE(tp) : TP_KEEPINIT(tp));
                        }
                        break;
                case TT_2MSL:
                        if (tp->t_timers->tt_flags &= TT_2MSL_SUS) {
                                tp->t_timers->tt_flags &= ~TT_2MSL_SUS;
                                if ((tp->t_state == TCPS_FIN_WAIT_2) &&
                                    ((tp->t_inpcb->inp_socket == NULL) ||
                                     (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE))) {
                                        /* Star the 2MSL timer */
                                        tcp_timer_activate(tp, TT_2MSL,
                                            (tcp_fast_finwait2_recycle) ?
                                            tcp_finwait2_timeout : TP_MAXIDLE(tp));
                                }
                        }
                        break;
                default:
                        panic("tp:%p bad timer_type 0x%x", tp, timer_type);
        }
}
 
static void
tcp_timer_discard(void *ptp)
{
        struct inpcb *inp;
        struct tcpcb *tp;
        struct epoch_tracker et;
 
        tp = (struct tcpcb *)ptp;
        CURVNET_SET(tp->t_vnet);
        NET_EPOCH_ENTER(et);
        inp = tp->t_inpcb;
        KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL",
                __func__, tp));
        INP_WLOCK(inp);
        KASSERT((tp->t_timers->tt_flags & TT_STOPPED) != 0,
                ("%s: tcpcb has to be stopped here", __func__));
        if (--tp->t_timers->tt_draincnt > 0 ||
            tcp_freecb(tp) == false)
                INP_WUNLOCK(inp);
        NET_EPOCH_EXIT(et);
        CURVNET_RESTORE();
}
 
void
tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
{
        struct callout *t_callout;
 
        tp->t_timers->tt_flags |= TT_STOPPED;
        switch (timer_type) {
                case TT_DELACK:
                        t_callout = &tp->t_timers->tt_delack;
                        break;
                case TT_REXMT:
                        t_callout = &tp->t_timers->tt_rexmt;
                        break;
                case TT_PERSIST:
                        t_callout = &tp->t_timers->tt_persist;
                        break;
                case TT_KEEP:
                        t_callout = &tp->t_timers->tt_keep;
                        break;
                case TT_2MSL:
                        t_callout = &tp->t_timers->tt_2msl;
                        break;
                default:
                        if (tp->t_fb->tfb_tcp_timer_stop) {
                                /*
                                 * XXXrrs we need to look at this with the
                                 * stop case below (flags).
                                 */
                                tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
                                return;
                        }
                        panic("tp %p bad timer_type %#x", tp, timer_type);
                }
 
        if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
                /*
                 * Can't stop the callout, defer tcpcb actual deletion
                 * to the last one. We do this using the async drain
                 * function and incrementing the count in
                 */
                tp->t_timers->tt_draincnt++;
        }
}