File:  [Qemu by Fabrice Bellard] / qemu / slirp / tcp_timer.c
Revision 1.1.1.3 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 16:54:26 2018 UTC (2 years, 1 month ago) by root
Branches: qemu, MAIN
CVS tags: qemu0105, qemu0104, qemu0103, qemu0102, qemu0101, qemu0100, HEAD
qemu 0.10.0

    1: /*
    2:  * Copyright (c) 1982, 1986, 1988, 1990, 1993
    3:  *	The Regents of the University of California.  All rights reserved.
    4:  *
    5:  * Redistribution and use in source and binary forms, with or without
    6:  * modification, are permitted provided that the following conditions
    7:  * are met:
    8:  * 1. Redistributions of source code must retain the above copyright
    9:  *    notice, this list of conditions and the following disclaimer.
   10:  * 2. Redistributions in binary form must reproduce the above copyright
   11:  *    notice, this list of conditions and the following disclaimer in the
   12:  *    documentation and/or other materials provided with the distribution.
   13:  * 3. Neither the name of the University nor the names of its contributors
   14:  *    may be used to endorse or promote products derived from this software
   15:  *    without specific prior written permission.
   16:  *
   17:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27:  * SUCH DAMAGE.
   28:  *
   29:  *	@(#)tcp_timer.c	8.1 (Berkeley) 6/10/93
   30:  * tcp_timer.c,v 1.2 1994/08/02 07:49:10 davidg Exp
   31:  */
   32: 
   33: #include <slirp.h>
   34: 
   35: #ifdef LOG_ENABLED
   36: struct   tcpstat tcpstat;        /* tcp statistics */
   37: #endif
   38: 
   39: u_int32_t        tcp_now;                /* for RFC 1323 timestamps */
   40: 
   41: static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer);
   42: 
   43: /*
   44:  * Fast timeout routine for processing delayed acks
   45:  */
   46: void
   47: tcp_fasttimo()
   48: {
   49: 	register struct socket *so;
   50: 	register struct tcpcb *tp;
   51: 
   52: 	DEBUG_CALL("tcp_fasttimo");
   53: 
   54: 	so = tcb.so_next;
   55: 	if (so)
   56: 	for (; so != &tcb; so = so->so_next)
   57: 		if ((tp = (struct tcpcb *)so->so_tcpcb) &&
   58: 		    (tp->t_flags & TF_DELACK)) {
   59: 			tp->t_flags &= ~TF_DELACK;
   60: 			tp->t_flags |= TF_ACKNOW;
   61: 			STAT(tcpstat.tcps_delack++);
   62: 			(void) tcp_output(tp);
   63: 		}
   64: }
   65: 
   66: /*
   67:  * Tcp protocol timeout routine called every 500 ms.
   68:  * Updates the timers in all active tcb's and
   69:  * causes finite state machine actions if timers expire.
   70:  */
   71: void
   72: tcp_slowtimo()
   73: {
   74: 	register struct socket *ip, *ipnxt;
   75: 	register struct tcpcb *tp;
   76: 	register int i;
   77: 
   78: 	DEBUG_CALL("tcp_slowtimo");
   79: 
   80: 	/*
   81: 	 * Search through tcb's and update active timers.
   82: 	 */
   83: 	ip = tcb.so_next;
   84: 	if (ip == 0)
   85: 	   return;
   86: 	for (; ip != &tcb; ip = ipnxt) {
   87: 		ipnxt = ip->so_next;
   88: 		tp = sototcpcb(ip);
   89: 		if (tp == 0)
   90: 			continue;
   91: 		for (i = 0; i < TCPT_NTIMERS; i++) {
   92: 			if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
   93: 				tcp_timers(tp,i);
   94: 				if (ipnxt->so_prev != ip)
   95: 					goto tpgone;
   96: 			}
   97: 		}
   98: 		tp->t_idle++;
   99: 		if (tp->t_rtt)
  100: 		   tp->t_rtt++;
  101: tpgone:
  102: 		;
  103: 	}
  104: 	tcp_iss += TCP_ISSINCR/PR_SLOWHZ;		/* increment iss */
  105: #ifdef TCP_COMPAT_42
  106: 	if ((int)tcp_iss < 0)
  107: 		tcp_iss = 0;				/* XXX */
  108: #endif
  109: 	tcp_now++;					/* for timestamps */
  110: }
  111: 
  112: /*
  113:  * Cancel all timers for TCP tp.
  114:  */
  115: void
  116: tcp_canceltimers(tp)
  117: 	struct tcpcb *tp;
  118: {
  119: 	register int i;
  120: 
  121: 	for (i = 0; i < TCPT_NTIMERS; i++)
  122: 		tp->t_timer[i] = 0;
  123: }
  124: 
  125: const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
  126:    { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
  127: 
  128: /*
  129:  * TCP timer processing.
  130:  */
  131: static struct tcpcb *
  132: tcp_timers(register struct tcpcb *tp, int timer)
  133: {
  134: 	register int rexmt;
  135: 
  136: 	DEBUG_CALL("tcp_timers");
  137: 
  138: 	switch (timer) {
  139: 
  140: 	/*
  141: 	 * 2 MSL timeout in shutdown went off.  If we're closed but
  142: 	 * still waiting for peer to close and connection has been idle
  143: 	 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
  144: 	 * control block.  Otherwise, check again in a bit.
  145: 	 */
  146: 	case TCPT_2MSL:
  147: 		if (tp->t_state != TCPS_TIME_WAIT &&
  148: 		    tp->t_idle <= TCP_MAXIDLE)
  149: 			tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL;
  150: 		else
  151: 			tp = tcp_close(tp);
  152: 		break;
  153: 
  154: 	/*
  155: 	 * Retransmission timer went off.  Message has not
  156: 	 * been acked within retransmit interval.  Back off
  157: 	 * to a longer retransmit interval and retransmit one segment.
  158: 	 */
  159: 	case TCPT_REXMT:
  160: 
  161: 		/*
  162: 		 * XXXXX If a packet has timed out, then remove all the queued
  163: 		 * packets for that session.
  164: 		 */
  165: 
  166: 		if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
  167: 			/*
  168: 			 * This is a hack to suit our terminal server here at the uni of canberra
  169: 			 * since they have trouble with zeroes... It usually lets them through
  170: 			 * unharmed, but under some conditions, it'll eat the zeros.  If we
  171: 			 * keep retransmitting it, it'll keep eating the zeroes, so we keep
  172: 			 * retransmitting, and eventually the connection dies...
  173: 			 * (this only happens on incoming data)
  174: 			 *
  175: 			 * So, if we were gonna drop the connection from too many retransmits,
  176: 			 * don't... instead halve the t_maxseg, which might break up the NULLs and
  177: 			 * let them through
  178: 			 *
  179: 			 * *sigh*
  180: 			 */
  181: 
  182: 			tp->t_maxseg >>= 1;
  183: 			if (tp->t_maxseg < 32) {
  184: 				/*
  185: 				 * We tried our best, now the connection must die!
  186: 				 */
  187: 				tp->t_rxtshift = TCP_MAXRXTSHIFT;
  188: 				STAT(tcpstat.tcps_timeoutdrop++);
  189: 				tp = tcp_drop(tp, tp->t_softerror);
  190: 				/* tp->t_softerror : ETIMEDOUT); */ /* XXX */
  191: 				return (tp); /* XXX */
  192: 			}
  193: 
  194: 			/*
  195: 			 * Set rxtshift to 6, which is still at the maximum
  196: 			 * backoff time
  197: 			 */
  198: 			tp->t_rxtshift = 6;
  199: 		}
  200: 		STAT(tcpstat.tcps_rexmttimeo++);
  201: 		rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
  202: 		TCPT_RANGESET(tp->t_rxtcur, rexmt,
  203: 		    (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
  204: 		tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
  205: 		/*
  206: 		 * If losing, let the lower level know and try for
  207: 		 * a better route.  Also, if we backed off this far,
  208: 		 * our srtt estimate is probably bogus.  Clobber it
  209: 		 * so we'll take the next rtt measurement as our srtt;
  210: 		 * move the current srtt into rttvar to keep the current
  211: 		 * retransmit times until then.
  212: 		 */
  213: 		if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
  214: /*			in_losing(tp->t_inpcb); */
  215: 			tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
  216: 			tp->t_srtt = 0;
  217: 		}
  218: 		tp->snd_nxt = tp->snd_una;
  219: 		/*
  220: 		 * If timing a segment in this window, stop the timer.
  221: 		 */
  222: 		tp->t_rtt = 0;
  223: 		/*
  224: 		 * Close the congestion window down to one segment
  225: 		 * (we'll open it by one segment for each ack we get).
  226: 		 * Since we probably have a window's worth of unacked
  227: 		 * data accumulated, this "slow start" keeps us from
  228: 		 * dumping all that data as back-to-back packets (which
  229: 		 * might overwhelm an intermediate gateway).
  230: 		 *
  231: 		 * There are two phases to the opening: Initially we
  232: 		 * open by one mss on each ack.  This makes the window
  233: 		 * size increase exponentially with time.  If the
  234: 		 * window is larger than the path can handle, this
  235: 		 * exponential growth results in dropped packet(s)
  236: 		 * almost immediately.  To get more time between
  237: 		 * drops but still "push" the network to take advantage
  238: 		 * of improving conditions, we switch from exponential
  239: 		 * to linear window opening at some threshold size.
  240: 		 * For a threshold, we use half the current window
  241: 		 * size, truncated to a multiple of the mss.
  242: 		 *
  243: 		 * (the minimum cwnd that will give us exponential
  244: 		 * growth is 2 mss.  We don't allow the threshold
  245: 		 * to go below this.)
  246: 		 */
  247: 		{
  248: 		u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
  249: 		if (win < 2)
  250: 			win = 2;
  251: 		tp->snd_cwnd = tp->t_maxseg;
  252: 		tp->snd_ssthresh = win * tp->t_maxseg;
  253: 		tp->t_dupacks = 0;
  254: 		}
  255: 		(void) tcp_output(tp);
  256: 		break;
  257: 
  258: 	/*
  259: 	 * Persistence timer into zero window.
  260: 	 * Force a byte to be output, if possible.
  261: 	 */
  262: 	case TCPT_PERSIST:
  263: 		STAT(tcpstat.tcps_persisttimeo++);
  264: 		tcp_setpersist(tp);
  265: 		tp->t_force = 1;
  266: 		(void) tcp_output(tp);
  267: 		tp->t_force = 0;
  268: 		break;
  269: 
  270: 	/*
  271: 	 * Keep-alive timer went off; send something
  272: 	 * or drop connection if idle for too long.
  273: 	 */
  274: 	case TCPT_KEEP:
  275: 		STAT(tcpstat.tcps_keeptimeo++);
  276: 		if (tp->t_state < TCPS_ESTABLISHED)
  277: 			goto dropit;
  278: 
  279: /*		if (tp->t_socket->so_options & SO_KEEPALIVE && */
  280: 		if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) {
  281: 		    	if (tp->t_idle >= TCPTV_KEEP_IDLE + TCP_MAXIDLE)
  282: 				goto dropit;
  283: 			/*
  284: 			 * Send a packet designed to force a response
  285: 			 * if the peer is up and reachable:
  286: 			 * either an ACK if the connection is still alive,
  287: 			 * or an RST if the peer has closed the connection
  288: 			 * due to timeout or reboot.
  289: 			 * Using sequence number tp->snd_una-1
  290: 			 * causes the transmitted zero-length segment
  291: 			 * to lie outside the receive window;
  292: 			 * by the protocol spec, this requires the
  293: 			 * correspondent TCP to respond.
  294: 			 */
  295: 			STAT(tcpstat.tcps_keepprobe++);
  296: #ifdef TCP_COMPAT_42
  297: 			/*
  298: 			 * The keepalive packet must have nonzero length
  299: 			 * to get a 4.2 host to respond.
  300: 			 */
  301: 			tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
  302: 			    tp->rcv_nxt - 1, tp->snd_una - 1, 0);
  303: #else
  304: 			tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
  305: 			    tp->rcv_nxt, tp->snd_una - 1, 0);
  306: #endif
  307: 			tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
  308: 		} else
  309: 			tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
  310: 		break;
  311: 
  312: 	dropit:
  313: 		STAT(tcpstat.tcps_keepdrops++);
  314: 		tp = tcp_drop(tp, 0); /* ETIMEDOUT); */
  315: 		break;
  316: 	}
  317: 
  318: 	return (tp);
  319: }

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