295 lines
8.6 KiB
C
295 lines
8.6 KiB
C
/*
|
|
* Copyright (c) 1982, 1986, 1988, 1990, 1993
|
|
* The Regents of the University of California. All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 3. Neither the name of the University nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*
|
|
* @(#)tcp_timer.c 8.1 (Berkeley) 6/10/93
|
|
* tcp_timer.c,v 1.2 1994/08/02 07:49:10 davidg Exp
|
|
*/
|
|
|
|
#include "qemu/osdep.h"
|
|
#include "slirp.h"
|
|
|
|
static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer);
|
|
|
|
/*
|
|
* Fast timeout routine for processing delayed acks
|
|
*/
|
|
void
|
|
tcp_fasttimo(Slirp *slirp)
|
|
{
|
|
register struct socket *so;
|
|
register struct tcpcb *tp;
|
|
|
|
DEBUG_CALL("tcp_fasttimo");
|
|
|
|
so = slirp->tcb.so_next;
|
|
if (so)
|
|
for (; so != &slirp->tcb; so = so->so_next)
|
|
if ((tp = (struct tcpcb *)so->so_tcpcb) &&
|
|
(tp->t_flags & TF_DELACK)) {
|
|
tp->t_flags &= ~TF_DELACK;
|
|
tp->t_flags |= TF_ACKNOW;
|
|
(void) tcp_output(tp);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Tcp protocol timeout routine called every 500 ms.
|
|
* Updates the timers in all active tcb's and
|
|
* causes finite state machine actions if timers expire.
|
|
*/
|
|
void
|
|
tcp_slowtimo(Slirp *slirp)
|
|
{
|
|
register struct socket *ip, *ipnxt;
|
|
register struct tcpcb *tp;
|
|
register int i;
|
|
|
|
DEBUG_CALL("tcp_slowtimo");
|
|
|
|
/*
|
|
* Search through tcb's and update active timers.
|
|
*/
|
|
ip = slirp->tcb.so_next;
|
|
if (ip == NULL) {
|
|
return;
|
|
}
|
|
for (; ip != &slirp->tcb; ip = ipnxt) {
|
|
ipnxt = ip->so_next;
|
|
tp = sototcpcb(ip);
|
|
if (tp == NULL) {
|
|
continue;
|
|
}
|
|
for (i = 0; i < TCPT_NTIMERS; i++) {
|
|
if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
|
|
tcp_timers(tp,i);
|
|
if (ipnxt->so_prev != ip)
|
|
goto tpgone;
|
|
}
|
|
}
|
|
tp->t_idle++;
|
|
if (tp->t_rtt)
|
|
tp->t_rtt++;
|
|
tpgone:
|
|
;
|
|
}
|
|
slirp->tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
|
|
slirp->tcp_now++; /* for timestamps */
|
|
}
|
|
|
|
/*
|
|
* Cancel all timers for TCP tp.
|
|
*/
|
|
void
|
|
tcp_canceltimers(struct tcpcb *tp)
|
|
{
|
|
register int i;
|
|
|
|
for (i = 0; i < TCPT_NTIMERS; i++)
|
|
tp->t_timer[i] = 0;
|
|
}
|
|
|
|
const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
|
|
{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
|
|
|
|
/*
|
|
* TCP timer processing.
|
|
*/
|
|
static struct tcpcb *
|
|
tcp_timers(register struct tcpcb *tp, int timer)
|
|
{
|
|
register int rexmt;
|
|
|
|
DEBUG_CALL("tcp_timers");
|
|
|
|
switch (timer) {
|
|
|
|
/*
|
|
* 2 MSL timeout in shutdown went off. If we're closed but
|
|
* still waiting for peer to close and connection has been idle
|
|
* too long, or if 2MSL time is up from TIME_WAIT, delete connection
|
|
* control block. Otherwise, check again in a bit.
|
|
*/
|
|
case TCPT_2MSL:
|
|
if (tp->t_state != TCPS_TIME_WAIT &&
|
|
tp->t_idle <= TCP_MAXIDLE)
|
|
tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL;
|
|
else
|
|
tp = tcp_close(tp);
|
|
break;
|
|
|
|
/*
|
|
* Retransmission timer went off. Message has not
|
|
* been acked within retransmit interval. Back off
|
|
* to a longer retransmit interval and retransmit one segment.
|
|
*/
|
|
case TCPT_REXMT:
|
|
|
|
/*
|
|
* XXXXX If a packet has timed out, then remove all the queued
|
|
* packets for that session.
|
|
*/
|
|
|
|
if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
|
|
/*
|
|
* This is a hack to suit our terminal server here at the uni of canberra
|
|
* since they have trouble with zeroes... It usually lets them through
|
|
* unharmed, but under some conditions, it'll eat the zeros. If we
|
|
* keep retransmitting it, it'll keep eating the zeroes, so we keep
|
|
* retransmitting, and eventually the connection dies...
|
|
* (this only happens on incoming data)
|
|
*
|
|
* So, if we were gonna drop the connection from too many retransmits,
|
|
* don't... instead halve the t_maxseg, which might break up the NULLs and
|
|
* let them through
|
|
*
|
|
* *sigh*
|
|
*/
|
|
|
|
tp->t_maxseg >>= 1;
|
|
if (tp->t_maxseg < 32) {
|
|
/*
|
|
* We tried our best, now the connection must die!
|
|
*/
|
|
tp->t_rxtshift = TCP_MAXRXTSHIFT;
|
|
tp = tcp_drop(tp, tp->t_softerror);
|
|
/* tp->t_softerror : ETIMEDOUT); */ /* XXX */
|
|
return (tp); /* XXX */
|
|
}
|
|
|
|
/*
|
|
* Set rxtshift to 6, which is still at the maximum
|
|
* backoff time
|
|
*/
|
|
tp->t_rxtshift = 6;
|
|
}
|
|
rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
|
|
TCPT_RANGESET(tp->t_rxtcur, rexmt,
|
|
(short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
|
|
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
|
|
/*
|
|
* If losing, let the lower level know and try for
|
|
* a better route. Also, 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) {
|
|
tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
|
|
tp->t_srtt = 0;
|
|
}
|
|
tp->snd_nxt = tp->snd_una;
|
|
/*
|
|
* If timing a segment in this window, stop the timer.
|
|
*/
|
|
tp->t_rtt = 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 threshold size.
|
|
* For a threshold, 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 threshold
|
|
* 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;
|
|
}
|
|
(void) tcp_output(tp);
|
|
break;
|
|
|
|
/*
|
|
* Persistence timer into zero window.
|
|
* Force a byte to be output, if possible.
|
|
*/
|
|
case TCPT_PERSIST:
|
|
tcp_setpersist(tp);
|
|
tp->t_force = 1;
|
|
(void) tcp_output(tp);
|
|
tp->t_force = 0;
|
|
break;
|
|
|
|
/*
|
|
* Keep-alive timer went off; send something
|
|
* or drop connection if idle for too long.
|
|
*/
|
|
case TCPT_KEEP:
|
|
if (tp->t_state < TCPS_ESTABLISHED)
|
|
goto dropit;
|
|
|
|
if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) {
|
|
if (tp->t_idle >= TCPTV_KEEP_IDLE + 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.
|
|
*/
|
|
tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
|
|
tp->rcv_nxt, tp->snd_una - 1, 0,
|
|
tp->t_socket->so_ffamily);
|
|
tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
|
|
} else
|
|
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
|
|
break;
|
|
|
|
dropit:
|
|
tp = tcp_drop(tp, 0);
|
|
break;
|
|
}
|
|
|
|
return (tp);
|
|
}
|