457 lines
12 KiB
C
457 lines
12 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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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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_compat.h"
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#include "opt_tcpdebug.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/sysctl.h>
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#include <sys/socket.h>
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#include <sys/socketvar.h>
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#include <sys/protosw.h>
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#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
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#include <net/route.h>
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#include <netinet/in.h>
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#include <netinet/in_systm.h>
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#include <netinet/in_pcb.h>
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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_seq.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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static int
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sysctl_msec_to_ticks SYSCTL_HANDLER_ARGS
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{
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int error, s, tt;
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tt = *(int *)oidp->oid_arg1;
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s = tt * 1000 / hz;
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error = sysctl_handle_int(oidp, &s, 0, req);
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if (error || !req->newptr)
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return (error);
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tt = s * hz / 1000;
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if (tt < 1)
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return (EINVAL);
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*(int *)oidp->oid_arg1 = tt;
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return (0);
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}
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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,
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CTLTYPE_INT|CTLFLAG_RW, &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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static int always_keepalive = 0;
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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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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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/*
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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()
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{
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int s;
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s = splnet();
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tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
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tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
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#ifdef TCP_COMPAT_42
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if ((int)tcp_iss < 0)
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tcp_iss = TCP_ISSINCR; /* XXX */
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#endif
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splx(s);
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}
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/*
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* Cancel all timers for TCP tp.
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*/
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void
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tcp_canceltimers(tp)
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struct tcpcb *tp;
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{
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callout_stop(tp->tt_2msl);
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callout_stop(tp->tt_persist);
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callout_stop(tp->tt_keep);
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callout_stop(tp->tt_rexmt);
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}
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int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
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{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
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static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
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/*
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* TCP timer processing.
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*/
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void
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tcp_timer_delack(xtp)
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void *xtp;
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{
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struct tcpcb *tp = xtp;
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int s;
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s = splnet();
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if (callout_pending(tp->tt_delack)) {
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splx(s);
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return;
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}
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callout_deactivate(tp->tt_delack);
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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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splx(s);
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}
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void
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tcp_timer_2msl(xtp)
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void *xtp;
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{
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struct tcpcb *tp = xtp;
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int s;
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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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s = splnet();
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if (callout_pending(tp->tt_2msl)) {
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splx(s);
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return;
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}
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callout_deactivate(tp->tt_2msl);
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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 (tp->t_state != TCPS_TIME_WAIT &&
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(ticks - tp->t_rcvtime) <= tcp_maxidle)
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callout_reset(tp->tt_2msl, tcp_keepintvl,
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tcp_timer_2msl, tp);
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else
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tp = tcp_close(tp);
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#ifdef TCPDEBUG
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if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
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tcp_trace(TA_USER, ostate, tp, (struct tcpiphdr *)0,
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PRU_SLOWTIMO);
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#endif
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splx(s);
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}
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void
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tcp_timer_keep(xtp)
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void *xtp;
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{
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struct tcpcb *tp = xtp;
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int s;
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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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s = splnet();
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if (callout_pending(tp->tt_keep)) {
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splx(s);
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return;
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}
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callout_deactivate(tp->tt_keep);
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/*
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* Keep-alive timer went off; send something
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* or drop connection if idle for too long.
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*/
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tcpstat.tcps_keeptimeo++;
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if (tp->t_state < TCPS_ESTABLISHED)
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goto dropit;
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if ((always_keepalive ||
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tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) &&
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tp->t_state <= TCPS_CLOSING) {
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if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle)
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goto dropit;
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/*
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* Send a packet designed to force a response
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* if the peer is up and reachable:
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* either an ACK if the connection is still alive,
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* or an RST if the peer has closed the connection
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* due to timeout or reboot.
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* Using sequence number tp->snd_una-1
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* causes the transmitted zero-length segment
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* to lie outside the receive window;
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* by the protocol spec, this requires the
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* correspondent TCP to respond.
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*/
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tcpstat.tcps_keepprobe++;
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#ifdef TCP_COMPAT_42
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/*
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* The keepalive packet must have nonzero length
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* to get a 4.2 host to respond.
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*/
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tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
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tp->rcv_nxt - 1, tp->snd_una - 1, 0);
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#else
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tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
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tp->rcv_nxt, tp->snd_una - 1, 0);
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#endif
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callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp);
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} else
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callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
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#ifdef TCPDEBUG
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if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
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tcp_trace(TA_USER, ostate, tp, (struct tcpiphdr *)0,
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PRU_SLOWTIMO);
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#endif
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splx(s);
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return;
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dropit:
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tcpstat.tcps_keepdrops++;
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tp = tcp_drop(tp, ETIMEDOUT);
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#ifdef TCPDEBUG
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if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
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tcp_trace(TA_USER, ostate, tp, (struct tcpiphdr *)0,
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PRU_SLOWTIMO);
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#endif
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splx(s);
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}
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void
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tcp_timer_persist(xtp)
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void *xtp;
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{
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struct tcpcb *tp = xtp;
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int s;
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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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s = splnet();
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if (callout_pending(tp->tt_persist)) {
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splx(s);
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return;
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}
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callout_deactivate(tp->tt_persist);
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/*
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* Persistance timer into zero window.
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* Force a byte to be output, if possible.
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*/
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tcpstat.tcps_persisttimeo++;
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/*
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* Hack: if the peer is dead/unreachable, we do not
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* time out if the window is closed. After a full
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* backoff, drop the connection if the idle time
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* (no responses to probes) reaches the maximum
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* backoff that we would use if retransmitting.
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*/
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if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
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((ticks - tp->t_rcvtime) >= tcp_maxpersistidle ||
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(ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
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tcpstat.tcps_persistdrop++;
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tp = tcp_drop(tp, ETIMEDOUT);
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goto out;
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}
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tcp_setpersist(tp);
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tp->t_force = 1;
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(void) tcp_output(tp);
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tp->t_force = 0;
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out:
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#ifdef TCPDEBUG
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if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
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tcp_trace(TA_USER, ostate, tp, (struct tcpiphdr *)0,
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PRU_SLOWTIMO);
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#endif
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splx(s);
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}
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void
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tcp_timer_rexmt(xtp)
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void *xtp;
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{
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struct tcpcb *tp = xtp;
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int s;
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int rexmt;
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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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s = splnet();
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if (callout_pending(tp->tt_rexmt)) {
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splx(s);
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return;
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}
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callout_deactivate(tp->tt_rexmt);
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/*
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* Retransmission timer went off. Message has not
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* been acked within retransmit interval. Back off
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* to a longer retransmit interval and retransmit one segment.
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*/
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if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
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tp->t_rxtshift = TCP_MAXRXTSHIFT;
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tcpstat.tcps_timeoutdrop++;
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tp = tcp_drop(tp, tp->t_softerror ?
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tp->t_softerror : ETIMEDOUT);
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goto out;
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}
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if (tp->t_rxtshift == 1) {
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/*
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* first retransmit; record ssthresh and cwnd so they can
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* be recovered if this turns out to be a "bad" retransmit.
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* A retransmit is considered "bad" if an ACK for this
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* segment is received within RTT/2 interval; the assumption
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* here is that the ACK was already in flight. See
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* "On Estimating End-to-End Network Path Properties" by
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* Allman and Paxson for more details.
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*/
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tp->snd_cwnd_prev = tp->snd_cwnd;
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tp->snd_ssthresh_prev = tp->snd_ssthresh;
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tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
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}
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tcpstat.tcps_rexmttimeo++;
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rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
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TCPT_RANGESET(tp->t_rxtcur, rexmt,
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tp->t_rttmin, TCPTV_REXMTMAX);
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/*
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* If losing, let the lower level know and try for
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* a better route. Also, if we backed off this far,
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* our srtt estimate is probably bogus. Clobber it
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* so we'll take the next rtt measurement as our srtt;
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* move the current srtt into rttvar to keep the current
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* retransmit times until then.
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*/
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if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
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in_losing(tp->t_inpcb);
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tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
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tp->t_srtt = 0;
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}
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tp->snd_nxt = tp->snd_una;
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/*
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* Force a segment to be sent.
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*/
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tp->t_flags |= TF_ACKNOW;
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/*
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* If timing a segment in this window, stop the timer.
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*/
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tp->t_rtttime = 0;
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/*
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* Close the congestion window down to one segment
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* (we'll open it by one segment for each ack we get).
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* Since we probably have a window's worth of unacked
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* data accumulated, this "slow start" keeps us from
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* dumping all that data as back-to-back packets (which
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* might overwhelm an intermediate gateway).
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*
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* There are two phases to the opening: Initially we
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* open by one mss on each ack. This makes the window
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* size increase exponentially with time. If the
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* window is larger than the path can handle, this
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* exponential growth results in dropped packet(s)
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* almost immediately. To get more time between
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* drops but still "push" the network to take advantage
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* of improving conditions, we switch from exponential
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* to linear window opening at some threshhold size.
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* For a threshhold, we use half the current window
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* size, truncated to a multiple of the mss.
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*
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* (the minimum cwnd that will give us exponential
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* growth is 2 mss. We don't allow the threshhold
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* to go below this.)
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*/
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{
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u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
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if (win < 2)
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win = 2;
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tp->snd_cwnd = tp->t_maxseg;
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tp->snd_ssthresh = win * tp->t_maxseg;
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tp->t_dupacks = 0;
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}
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(void) tcp_output(tp);
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out:
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#ifdef TCPDEBUG
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if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
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tcp_trace(TA_USER, ostate, tp, (struct tcpiphdr *)0,
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PRU_SLOWTIMO);
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#endif
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splx(s);
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}
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