slirp/tcp_timer.c - qemu - Git at Google

 /*
  * 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);
 }
	/*
	* 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);
	}