qemu/slirp/tcp_timer.c
Guillaume Subiron 9dfbf250d2 slirp: Generalizing and neutralizing various TCP functions before adding IPv6 stuff
Basically, this patch adds some switch in various TCP functions to
prepare them for the IPv6 case.

To have something to "switch" in tcp_input() and tcp_respond(), a new
argument is used to give them the sa_family of the addresses they are
working on.

This patch does not include the entailed reindentation, to make proofread
easier. Reindentation is adressed in the following no-op patch.

Signed-off-by: Guillaume Subiron <maethor@subiron.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
2016-03-15 10:35:14 +01:00

295 lines
8.5 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);
}