2104448fe7
other than repo copied tcp_subr.c into tcp_timewait.c#1.284: tcp_input.c#1.350 tcp_timewait() -> tcp_twcheck() tcp_timer.c#1.92 tcp_timer_2msl_reset() -> tcp_tw_2msl_reset() tcp_timer.c#1.92 tcp_timer_2msl_stop() -> tcp_tw_2msl_stop() tcp_timer.c#1.92 tcp_timer_2msl_tw() -> tcp_tw_2msl_scan() This is a mechanical move with appropriate renames and making them static if used only locally. The tcp_tw_2msl_scan() cleanup function is still run from the tcp_slowtimo() in tcp_timer.c.
687 lines
20 KiB
C
687 lines
20 KiB
C
/*-
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* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
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* $FreeBSD$
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*/
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#include "opt_inet6.h"
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#include "opt_tcpdebug.h"
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/limits.h>
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#include <sys/mbuf.h>
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#include <sys/mutex.h>
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#include <sys/protosw.h>
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#include <sys/socket.h>
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#include <sys/socketvar.h>
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#include <sys/sysctl.h>
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#include <sys/systm.h>
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#include <net/route.h>
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#include <netinet/in.h>
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#include <netinet/in_pcb.h>
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#include <netinet/in_systm.h>
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#ifdef INET6
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#include <netinet6/in6_pcb.h>
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#endif
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#include <netinet/ip_var.h>
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#include <netinet/tcp.h>
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#include <netinet/tcp_fsm.h>
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#include <netinet/tcp_timer.h>
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#include <netinet/tcp_var.h>
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#include <netinet/tcpip.h>
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#ifdef TCPDEBUG
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#include <netinet/tcp_debug.h>
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#endif
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int tcp_keepinit;
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SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
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&tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "");
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int tcp_keepidle;
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SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
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&tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "");
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int tcp_keepintvl;
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SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
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&tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "");
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int tcp_delacktime;
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SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
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&tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
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"Time before a delayed ACK is sent");
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int tcp_msl;
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SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
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&tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
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int tcp_rexmit_min;
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SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
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&tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
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"Minimum Retransmission Timeout");
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int tcp_rexmit_slop;
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SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
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&tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
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"Retransmission Timer Slop");
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static int always_keepalive = 1;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
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&always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
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int tcp_fast_finwait2_recycle = 0;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
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&tcp_fast_finwait2_recycle, 0,
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"Recycle closed FIN_WAIT_2 connections faster");
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int tcp_finwait2_timeout;
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SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
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&tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
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static int tcp_keepcnt = TCPTV_KEEPCNT;
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/* max idle probes */
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int tcp_maxpersistidle;
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/* max idle time in persist */
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int tcp_maxidle;
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static void tcp_timer(void *);
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static int tcp_timer_delack(struct tcpcb *, struct inpcb *);
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static int tcp_timer_2msl(struct tcpcb *, struct inpcb *);
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static int tcp_timer_keep(struct tcpcb *, struct inpcb *);
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static int tcp_timer_persist(struct tcpcb *, struct inpcb *);
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static int tcp_timer_rexmt(struct tcpcb *, struct inpcb *);
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/*
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* Tcp protocol timeout routine called every 500 ms.
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* Updates timestamps used for TCP
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* causes finite state machine actions if timers expire.
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*/
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void
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tcp_slowtimo(void)
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{
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tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
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INP_INFO_WLOCK(&tcbinfo);
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(void) tcp_tw_2msl_scan(0);
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INP_INFO_WUNLOCK(&tcbinfo);
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}
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int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
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{ 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
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int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
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{ 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
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static int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
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static int tcp_timer_race;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, timer_race, CTLFLAG_RD, &tcp_timer_race,
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0, "Count of t_inpcb races on tcp_discardcb");
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void
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tcp_timer_activate(struct tcpcb *tp, int timer_type, u_int delta)
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{
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struct inpcb *inp = tp->t_inpcb;
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struct tcp_timer *tt = tp->t_timers;
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int tick = ticks; /* Stable time base. */
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int next = delta ? tick + delta : 0;
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INP_LOCK_ASSERT(inp);
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CTR6(KTR_NET, "%p %s inp %p active %x delta %i nextc %i",
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tp, __func__, inp, tt->tt_active, delta, tt->tt_nextc);
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/* Set new value for timer. */
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switch(timer_type) {
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case TT_DELACK:
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CTR4(KTR_NET, "%p %s TT_DELACK old %i new %i",
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tp, __func__, tt->tt_delack, next);
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tt->tt_delack = next;
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break;
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case TT_REXMT:
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CTR4(KTR_NET, "%p %s TT_REXMT old %i new %i",
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tp, __func__, tt->tt_rexmt, next);
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tt->tt_rexmt = next;
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break;
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case TT_PERSIST:
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CTR4(KTR_NET, "%p %s TT_PERSIST old %i new %i",
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tp, __func__, tt->tt_persist, next);
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tt->tt_persist = next;
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break;
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case TT_KEEP:
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CTR4(KTR_NET, "%p %s TT_KEEP old %i new %i",
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tp, __func__, tt->tt_keep, next);
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tt->tt_keep = next;
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break;
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case TT_2MSL:
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CTR4(KTR_NET, "%p %s TT_2MSL old %i new %i",
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tp, __func__, tt->tt_2msl, next);
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tt->tt_2msl = next;
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break;
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case 0: /* Dummy for timer rescan. */
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CTR3(KTR_NET, "%p %s timer rescan new %i", tp, __func__, next);
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break;
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}
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/* If some other timer is active and is schedules sooner just return. */
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if (tt->tt_active != timer_type && tt->tt_nextc < next &&
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callout_active(&tt->tt_timer))
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return;
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/* Select next timer to schedule. */
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tt->tt_nextc = INT_MAX;
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tt->tt_active = 0;
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if (tt->tt_delack && tt->tt_delack < tt->tt_nextc) {
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tt->tt_nextc = tt->tt_delack;
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tt->tt_active = TT_DELACK;
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}
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if (tt->tt_rexmt && tt->tt_rexmt < tt->tt_nextc) {
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tt->tt_nextc = tt->tt_rexmt;
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tt->tt_active = TT_REXMT;
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}
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if (tt->tt_persist && tt->tt_persist < tt->tt_nextc) {
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tt->tt_nextc = tt->tt_persist;
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tt->tt_active = TT_PERSIST;
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}
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if (tt->tt_keep && tt->tt_keep < tt->tt_nextc) {
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tt->tt_nextc = tt->tt_keep;
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tt->tt_active = TT_KEEP;
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}
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if (tt->tt_2msl && tt->tt_2msl < tt->tt_nextc) {
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tt->tt_nextc = tt->tt_2msl;
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tt->tt_active = TT_2MSL;
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}
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/* Rearm callout with new timer if we found one. */
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if (tt->tt_active) {
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CTR4(KTR_NET, "%p %s callout_reset active %x nextc in %i",
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tp, __func__, tt->tt_active, tt->tt_nextc - tick);
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callout_reset(&tt->tt_timer,
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tt->tt_nextc - tick, tcp_timer, (void *)inp);
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} else {
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CTR2(KTR_NET, "%p %s callout_stop", tp, __func__);
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callout_stop(&tt->tt_timer);
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tt->tt_nextc = 0;
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}
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return;
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}
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int
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tcp_timer_active(struct tcpcb *tp, int timer_type)
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{
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switch (timer_type) {
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case TT_DELACK:
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CTR3(KTR_NET, "%p %s TT_DELACK %i",
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tp, __func__, tp->t_timers->tt_delack);
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return (tp->t_timers->tt_delack ? 1 : 0);
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break;
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case TT_REXMT:
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CTR3(KTR_NET, "%p %s TT_REXMT %i",
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tp, __func__, tp->t_timers->tt_rexmt);
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return (tp->t_timers->tt_rexmt ? 1 : 0);
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break;
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case TT_PERSIST:
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CTR3(KTR_NET, "%p %s TT_PERSIST %i",
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tp, __func__, tp->t_timers->tt_persist);
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return (tp->t_timers->tt_persist ? 1 : 0);
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break;
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case TT_KEEP:
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CTR3(KTR_NET, "%p %s TT_KEEP %i",
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tp, __func__, tp->t_timers->tt_keep);
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return (tp->t_timers->tt_keep ? 1 : 0);
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break;
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case TT_2MSL:
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CTR3(KTR_NET, "%p %s TT_2MSL %i",
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tp, __func__, tp->t_timers->tt_2msl);
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return (tp->t_timers->tt_2msl ? 1 : 0);
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break;
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}
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return (0);
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}
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static void
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tcp_timer(void *xinp)
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{
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struct inpcb *inp = (struct inpcb *)xinp;
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struct tcpcb *tp = intotcpcb(inp);
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struct tcp_timer *tt;
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int tick = ticks;
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int down, timer;
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/* INP lock was obtained by callout. */
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INP_LOCK_ASSERT(inp);
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/*
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* We've got a couple of race conditions here:
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* - The tcpcb was converted into a compressed TW pcb. All our
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* timers have been stopped while this callout already tried
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* to obtain the inpcb lock. TW pcbs have their own timers
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* and we just return.
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*/
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if (inp->inp_vflag & INP_TIMEWAIT)
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return;
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/*
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* - The tcpcb was discarded. All our timers have been stopped
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* while this callout already tried to obtain the inpcb lock
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* and we just return.
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*/
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if (tp == NULL)
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return;
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tt = tp->t_timers; /* Initialize. */
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CTR6(KTR_NET, "%p %s inp %p active %x tick %i nextc %i",
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tp, __func__, inp, tt->tt_active, tick, tt->tt_nextc);
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/*
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* - We may have been waiting on the lock while the tcpcb has
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* been scheduled for destruction. In this case no active
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* timers remain and we just return.
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*/
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if (tt->tt_active == 0)
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goto done;
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/*
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* - The timer was rescheduled while this callout was already
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* waiting on the lock. This may happen when a packet just
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* came in. Rescan and reschedule the the timer in case we
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* just turned it off.
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*/
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if (tick < tt->tt_nextc)
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goto rescan;
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/*
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* Mark as done. The active bit in struct callout is not
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* automatically cleared. See callout(9) for more info.
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* In tcp_discardcb() we depend on the correctly cleared
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* active bit for faster processing.
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*/
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callout_deactivate(&tt->tt_timer);
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/* Check which timer has fired and remove this timer activation. */
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timer = tt->tt_active;
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tt->tt_active = 0;
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tt->tt_nextc = 0;
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switch (timer) {
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case TT_DELACK:
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CTR2(KTR_NET, "%p %s running TT_DELACK", tp, __func__);
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tt->tt_delack = 0;
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down = tcp_timer_delack(tp, inp); /* down == 0 */
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break;
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case TT_REXMT:
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CTR2(KTR_NET, "%p %s running TT_REXMT", tp, __func__);
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tt->tt_rexmt = 0;
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down = tcp_timer_rexmt(tp, inp);
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break;
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case TT_PERSIST:
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CTR2(KTR_NET, "%p %s running TT_PERSIST", tp, __func__);
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tt->tt_persist = 0;
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down = tcp_timer_persist(tp, inp);
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break;
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case TT_KEEP:
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CTR2(KTR_NET, "%p %s running TT_KEEP", tp, __func__);
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tt->tt_keep = 0;
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down = tcp_timer_keep(tp, inp);
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break;
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case TT_2MSL:
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CTR2(KTR_NET, "%p %s running TT_2MSL", tp, __func__);
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tt->tt_2msl = 0;
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down = tcp_timer_2msl(tp, inp);
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break;
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default:
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CTR2(KTR_NET, "%p %s running nothing", tp, __func__);
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down = 0;
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}
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CTR4(KTR_NET, "%p %s down %i active %x",
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tp, __func__, down, tt->tt_active);
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/* Do we still exist? */
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if (down)
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goto shutdown;
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rescan:
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/* Rescan if no timer was reactivated above. */
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if (tt->tt_active == 0)
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tcp_timer_activate(tp, 0, 0);
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done:
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INP_UNLOCK(inp); /* CALLOUT_RETURNUNLOCKED */
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return;
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shutdown:
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INP_UNLOCK(inp); /* Prevent LOR at expense of race. */
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INP_INFO_WLOCK(&tcbinfo);
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INP_LOCK(inp);
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/* When tp is gone we've lost the race. */
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if (inp->inp_ppcb == NULL) {
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CTR3(KTR_NET, "%p %s inp %p lost shutdown race",
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tp, __func__, inp);
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tcp_timer_race++;
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INP_UNLOCK(inp); /* CALLOUT_RETURNUNLOCKED */
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INP_INFO_WUNLOCK(&tcbinfo);
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return;
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}
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KASSERT(tp == inp->inp_ppcb, ("%s: tp changed", __func__));
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/* Shutdown the connection. */
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switch (down) {
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case 1:
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tp = tcp_close(tp);
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break;
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case 2:
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tp = tcp_drop(tp,
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tp->t_softerror ? tp->t_softerror : ETIMEDOUT);
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break;
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}
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CTR3(KTR_NET, "%p %s inp %p after shutdown", tp, __func__, inp);
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if (tp)
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INP_UNLOCK(inp); /* CALLOUT_RETURNUNLOCKED */
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INP_INFO_WUNLOCK(&tcbinfo);
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return;
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}
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/*
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* TCP timer processing.
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*/
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static int
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tcp_timer_delack(struct tcpcb *tp, struct inpcb *inp)
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{
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tp->t_flags |= TF_ACKNOW;
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tcpstat.tcps_delack++;
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(void) tcp_output(tp);
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return (0);
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}
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static int
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tcp_timer_2msl(struct tcpcb *tp, struct inpcb *inp)
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{
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#ifdef TCPDEBUG
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int ostate;
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ostate = tp->t_state;
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#endif
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/*
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* 2 MSL timeout in shutdown went off. If we're closed but
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* still waiting for peer to close and connection has been idle
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* too long, or if 2MSL time is up from TIME_WAIT, delete connection
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* control block. Otherwise, check again in a bit.
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*
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* If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
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|
* 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->inp_socket &&
|
|
(tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
|
|
tcpstat.tcps_finwait2_drops++;
|
|
return (1); /* tcp_close */
|
|
} else {
|
|
if (tp->t_state != TCPS_TIME_WAIT &&
|
|
(ticks - tp->t_rcvtime) <= tcp_maxidle)
|
|
tcp_timer_activate(tp, TT_2MSL, tcp_keepintvl);
|
|
else
|
|
return (1); /* tcp_close */
|
|
}
|
|
|
|
#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
|
|
return (0);
|
|
}
|
|
|
|
static int
|
|
tcp_timer_keep(struct tcpcb *tp, struct inpcb *inp)
|
|
{
|
|
struct tcptemp *t_template;
|
|
#ifdef TCPDEBUG
|
|
int ostate;
|
|
|
|
ostate = tp->t_state;
|
|
#endif
|
|
/*
|
|
* Keep-alive timer went off; send something
|
|
* or drop connection if idle for too long.
|
|
*/
|
|
tcpstat.tcps_keeptimeo++;
|
|
if (tp->t_state < TCPS_ESTABLISHED)
|
|
goto dropit;
|
|
if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) &&
|
|
tp->t_state <= TCPS_CLOSING) {
|
|
if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle)
|
|
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.tcps_keepprobe++;
|
|
t_template = tcpip_maketemplate(inp);
|
|
if (t_template) {
|
|
tcp_respond(tp, t_template->tt_ipgen,
|
|
&t_template->tt_t, (struct mbuf *)NULL,
|
|
tp->rcv_nxt, tp->snd_una - 1, 0);
|
|
(void) m_free(dtom(t_template));
|
|
}
|
|
tcp_timer_activate(tp, TT_KEEP, tcp_keepintvl);
|
|
} else
|
|
tcp_timer_activate(tp, TT_KEEP, tcp_keepidle);
|
|
|
|
#ifdef TCPDEBUG
|
|
if (inp->inp_socket->so_options & SO_DEBUG)
|
|
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
|
|
PRU_SLOWTIMO);
|
|
#endif
|
|
return (0);
|
|
|
|
dropit:
|
|
tcpstat.tcps_keepdrops++;
|
|
return (2); /* tcp_drop() */
|
|
}
|
|
|
|
static int
|
|
tcp_timer_persist(struct tcpcb *tp, struct inpcb *inp)
|
|
{
|
|
#ifdef TCPDEBUG
|
|
int ostate;
|
|
|
|
ostate = tp->t_state;
|
|
#endif
|
|
/*
|
|
* Persistance timer into zero window.
|
|
* Force a byte to be output, if possible.
|
|
*/
|
|
tcpstat.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.tcps_persistdrop++;
|
|
return (2); /* tcp_drop() */
|
|
}
|
|
tcp_setpersist(tp);
|
|
tp->t_flags |= TF_FORCEDATA;
|
|
(void) tcp_output(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
|
|
return (0);
|
|
}
|
|
|
|
static int
|
|
tcp_timer_rexmt(struct tcpcb *tp, struct inpcb *inp)
|
|
{
|
|
int rexmt;
|
|
#ifdef TCPDEBUG
|
|
int ostate;
|
|
|
|
ostate = tp->t_state;
|
|
#endif
|
|
tcp_free_sackholes(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.tcps_timeoutdrop++;
|
|
return (2); /* tcp_drop() */
|
|
}
|
|
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))
|
|
tp->t_flags |= TF_WASFRECOVERY;
|
|
else
|
|
tp->t_flags &= ~TF_WASFRECOVERY;
|
|
tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
|
|
}
|
|
tcpstat.tcps_rexmttimeo++;
|
|
if (tp->t_state == TCPS_SYN_SENT)
|
|
rexmt = TCP_REXMTVAL(tp) * tcp_syn_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);
|
|
/*
|
|
* Disable rfc1323 if we havn'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 ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3))
|
|
tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP);
|
|
/*
|
|
* If we backed off this far, our srtt estimate is probably bogus.
|
|
* Clobber it so we'll take the next rtt measurement as our srtt;
|
|
* move the current srtt into rttvar to keep the current
|
|
* retransmit times until then.
|
|
*/
|
|
if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
|
|
#ifdef INET6
|
|
if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
|
|
in6_losing(tp->t_inpcb);
|
|
else
|
|
#endif
|
|
tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
|
|
tp->t_srtt = 0;
|
|
}
|
|
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;
|
|
/*
|
|
* Close the congestion window down to one segment
|
|
* (we'll open it by one segment for each ack we get).
|
|
* Since we probably have a window's worth of unacked
|
|
* data accumulated, this "slow start" keeps us from
|
|
* dumping all that data as back-to-back packets (which
|
|
* might overwhelm an intermediate gateway).
|
|
*
|
|
* There are two phases to the opening: Initially we
|
|
* open by one mss on each ack. This makes the window
|
|
* size increase exponentially with time. If the
|
|
* window is larger than the path can handle, this
|
|
* exponential growth results in dropped packet(s)
|
|
* almost immediately. To get more time between
|
|
* drops but still "push" the network to take advantage
|
|
* of improving conditions, we switch from exponential
|
|
* to linear window opening at some threshhold size.
|
|
* For a threshhold, we use half the current window
|
|
* size, truncated to a multiple of the mss.
|
|
*
|
|
* (the minimum cwnd that will give us exponential
|
|
* growth is 2 mss. We don't allow the threshhold
|
|
* to go below this.)
|
|
*/
|
|
{
|
|
u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
|
|
if (win < 2)
|
|
win = 2;
|
|
tp->snd_cwnd = tp->t_maxseg;
|
|
tp->snd_ssthresh = win * tp->t_maxseg;
|
|
tp->t_dupacks = 0;
|
|
}
|
|
EXIT_FASTRECOVERY(tp);
|
|
(void) tcp_output(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
|
|
return (0);
|
|
}
|