root / slirp / tcp_timer.c @ 0d62c4cf
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/*
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* Copyright (c) 1982, 1986, 1988, 1990, 1993
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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. 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 8.1 (Berkeley) 6/10/93
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* tcp_timer.c,v 1.2 1994/08/02 07:49:10 davidg Exp
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*/
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#include <slirp.h> |
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#ifdef LOG_ENABLED
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struct tcpstat tcpstat; /* tcp statistics */ |
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#endif
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u_int32_t tcp_now; /* for RFC 1323 timestamps */
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static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer); |
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/*
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* Fast timeout routine for processing delayed acks
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*/
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void
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tcp_fasttimo(void)
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{
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register struct socket *so; |
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register struct tcpcb *tp; |
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DEBUG_CALL("tcp_fasttimo");
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so = tcb.so_next; |
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if (so)
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for (; so != &tcb; so = so->so_next)
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if ((tp = (struct tcpcb *)so->so_tcpcb) && |
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(tp->t_flags & TF_DELACK)) {
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tp->t_flags &= ~TF_DELACK; |
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tp->t_flags |= TF_ACKNOW; |
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STAT(tcpstat.tcps_delack++); |
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(void) tcp_output(tp);
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} |
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} |
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/*
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* Tcp protocol timeout routine called every 500 ms.
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* Updates the timers in all active tcb's and
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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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register struct socket *ip, *ipnxt; |
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register struct tcpcb *tp; |
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register int i; |
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DEBUG_CALL("tcp_slowtimo");
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/*
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* Search through tcb's and update active timers.
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*/
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ip = tcb.so_next; |
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if (ip == 0) |
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return;
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for (; ip != &tcb; ip = ipnxt) {
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ipnxt = ip->so_next; |
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tp = sototcpcb(ip); |
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if (tp == 0) |
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continue;
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for (i = 0; i < TCPT_NTIMERS; i++) { |
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if (tp->t_timer[i] && --tp->t_timer[i] == 0) { |
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tcp_timers(tp,i); |
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if (ipnxt->so_prev != ip)
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goto tpgone;
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} |
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} |
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tp->t_idle++; |
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if (tp->t_rtt)
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tp->t_rtt++; |
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tpgone:
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; |
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} |
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tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
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tcp_now++; /* for timestamps */
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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(struct tcpcb *tp)
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{
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register int i; |
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for (i = 0; i < TCPT_NTIMERS; i++) |
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tp->t_timer[i] = 0;
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} |
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const 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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/*
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* TCP timer processing.
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*/
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static struct tcpcb * |
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tcp_timers(register struct tcpcb *tp, int timer) |
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{
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register int rexmt; |
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DEBUG_CALL("tcp_timers");
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switch (timer) {
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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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case TCPT_2MSL:
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if (tp->t_state != TCPS_TIME_WAIT &&
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tp->t_idle <= TCP_MAXIDLE) |
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tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL; |
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else
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tp = tcp_close(tp); |
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break;
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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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case TCPT_REXMT:
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/*
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* XXXXX If a packet has timed out, then remove all the queued
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* packets for that session.
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*/
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if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
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/*
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* This is a hack to suit our terminal server here at the uni of canberra
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* since they have trouble with zeroes... It usually lets them through
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* unharmed, but under some conditions, it'll eat the zeros. If we
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* keep retransmitting it, it'll keep eating the zeroes, so we keep
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* retransmitting, and eventually the connection dies...
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* (this only happens on incoming data)
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*
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* So, if we were gonna drop the connection from too many retransmits,
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* don't... instead halve the t_maxseg, which might break up the NULLs and
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* let them through
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*
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* *sigh*
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*/
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tp->t_maxseg >>= 1;
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if (tp->t_maxseg < 32) { |
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/*
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* We tried our best, now the connection must die!
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*/
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tp->t_rxtshift = TCP_MAXRXTSHIFT; |
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STAT(tcpstat.tcps_timeoutdrop++); |
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tp = tcp_drop(tp, tp->t_softerror); |
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/* tp->t_softerror : ETIMEDOUT); */ /* XXX */ |
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return (tp); /* XXX */ |
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} |
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/*
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* Set rxtshift to 6, which is still at the maximum
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* backoff time
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*/
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tp->t_rxtshift = 6;
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} |
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STAT(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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(short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */ |
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tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; |
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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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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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* If timing a segment in this window, stop the timer.
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*/
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tp->t_rtt = 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 threshold size.
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* For a threshold, 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 threshold
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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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break;
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/*
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* Persistence timer into zero window.
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* Force a byte to be output, if possible.
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*/
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case TCPT_PERSIST:
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STAT(tcpstat.tcps_persisttimeo++); |
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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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break;
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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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case TCPT_KEEP:
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STAT(tcpstat.tcps_keeptimeo++); |
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if (tp->t_state < TCPS_ESTABLISHED)
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goto dropit;
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if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) {
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if (tp->t_idle >= TCPTV_KEEP_IDLE + 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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STAT(tcpstat.tcps_keepprobe++); |
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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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tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL; |
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} else
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tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE; |
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break;
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dropit:
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STAT(tcpstat.tcps_keepdrops++); |
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tp = tcp_drop(tp, 0);
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break;
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} |
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return (tp);
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} |