File:  [Qemu by Fabrice Bellard] / qemu / slirp / tcp_timer.c
Revision 1.1: download - view: text, annotated - select for diffs
Tue Apr 24 16:37:52 2018 UTC (3 years, 1 month ago) by root
CVS tags: MAIN, HEAD
Initial revision

    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. All advertising materials mentioning features or use of this software
   14:  *    must display the following acknowledgement:
   15:  *	This product includes software developed by the University of
   16:  *	California, Berkeley and its contributors.
   17:  * 4. Neither the name of the University nor the names of its contributors
   18:  *    may be used to endorse or promote products derived from this software
   19:  *    without specific prior written permission.
   20:  *
   21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31:  * SUCH DAMAGE.
   32:  *
   33:  *	@(#)tcp_timer.c	8.1 (Berkeley) 6/10/93
   34:  * tcp_timer.c,v 1.2 1994/08/02 07:49:10 davidg Exp
   35:  */
   36: 
   37: #include <slirp.h>
   38: 
   39: int	tcp_keepidle = TCPTV_KEEP_IDLE;
   40: int	tcp_keepintvl = TCPTV_KEEPINTVL;
   41: int	tcp_maxidle;
   42: int	so_options = DO_KEEPALIVE;
   43: 
   44: struct   tcpstat tcpstat;        /* tcp statistics */
   45: u_int32_t        tcp_now;                /* for RFC 1323 timestamps */
   46: 
   47: /*
   48:  * Fast timeout routine for processing delayed acks
   49:  */
   50: void
   51: tcp_fasttimo()
   52: {
   53: 	register struct socket *so;
   54: 	register struct tcpcb *tp;
   55: 
   56: 	DEBUG_CALL("tcp_fasttimo");
   57: 	
   58: 	so = tcb.so_next;
   59: 	if (so)
   60: 	for (; so != &tcb; so = so->so_next)
   61: 		if ((tp = (struct tcpcb *)so->so_tcpcb) &&
   62: 		    (tp->t_flags & TF_DELACK)) {
   63: 			tp->t_flags &= ~TF_DELACK;
   64: 			tp->t_flags |= TF_ACKNOW;
   65: 			tcpstat.tcps_delack++;
   66: 			(void) tcp_output(tp);
   67: 		}
   68: }
   69: 
   70: /*
   71:  * Tcp protocol timeout routine called every 500 ms.
   72:  * Updates the timers in all active tcb's and
   73:  * causes finite state machine actions if timers expire.
   74:  */
   75: void
   76: tcp_slowtimo()
   77: {
   78: 	register struct socket *ip, *ipnxt;
   79: 	register struct tcpcb *tp;
   80: 	register int i;
   81: 
   82: 	DEBUG_CALL("tcp_slowtimo");
   83: 	
   84: 	tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
   85: 	/*
   86: 	 * Search through tcb's and update active timers.
   87: 	 */
   88: 	ip = tcb.so_next;
   89: 	if (ip == 0)
   90: 	   return;
   91: 	for (; ip != &tcb; ip = ipnxt) {
   92: 		ipnxt = ip->so_next;
   93: 		tp = sototcpcb(ip);
   94: 		if (tp == 0)
   95: 			continue;
   96: 		for (i = 0; i < TCPT_NTIMERS; i++) {
   97: 			if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
   98: 				tcp_timers(tp,i);
   99: 				if (ipnxt->so_prev != ip)
  100: 					goto tpgone;
  101: 			}
  102: 		}
  103: 		tp->t_idle++;
  104: 		if (tp->t_rtt)
  105: 		   tp->t_rtt++;
  106: tpgone:
  107: 		;
  108: 	}
  109: 	tcp_iss += TCP_ISSINCR/PR_SLOWHZ;		/* increment iss */
  110: #ifdef TCP_COMPAT_42
  111: 	if ((int)tcp_iss < 0)
  112: 		tcp_iss = 0;				/* XXX */
  113: #endif
  114: 	tcp_now++;					/* for timestamps */
  115: }
  116: 
  117: /*
  118:  * Cancel all timers for TCP tp.
  119:  */
  120: void
  121: tcp_canceltimers(tp)
  122: 	struct tcpcb *tp;
  123: {
  124: 	register int i;
  125: 
  126: 	for (i = 0; i < TCPT_NTIMERS; i++)
  127: 		tp->t_timer[i] = 0;
  128: }
  129: 
  130: int	tcp_backoff[TCP_MAXRXTSHIFT + 1] =
  131:    { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
  132: 
  133: /*
  134:  * TCP timer processing.
  135:  */
  136: struct tcpcb *
  137: tcp_timers(tp, timer)
  138: 	register struct tcpcb *tp;
  139: 	int timer;
  140: {
  141: 	register int rexmt;
  142: 	
  143: 	DEBUG_CALL("tcp_timers");
  144: 	
  145: 	switch (timer) {
  146: 
  147: 	/*
  148: 	 * 2 MSL timeout in shutdown went off.  If we're closed but
  149: 	 * still waiting for peer to close and connection has been idle
  150: 	 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
  151: 	 * control block.  Otherwise, check again in a bit.
  152: 	 */
  153: 	case TCPT_2MSL:
  154: 		if (tp->t_state != TCPS_TIME_WAIT &&
  155: 		    tp->t_idle <= tcp_maxidle)
  156: 			tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
  157: 		else
  158: 			tp = tcp_close(tp);
  159: 		break;
  160: 
  161: 	/*
  162: 	 * Retransmission timer went off.  Message has not
  163: 	 * been acked within retransmit interval.  Back off
  164: 	 * to a longer retransmit interval and retransmit one segment.
  165: 	 */
  166: 	case TCPT_REXMT:
  167: 		
  168: 		/*
  169: 		 * XXXXX If a packet has timed out, then remove all the queued
  170: 		 * packets for that session.
  171: 		 */
  172: 		
  173: 		if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
  174: 			/*
  175: 			 * This is a hack to suit our terminal server here at the uni of canberra
  176: 			 * since they have trouble with zeroes... It usually lets them through
  177: 			 * unharmed, but under some conditions, it'll eat the zeros.  If we
  178: 			 * keep retransmitting it, it'll keep eating the zeroes, so we keep
  179: 			 * retransmitting, and eventually the connection dies...
  180: 			 * (this only happens on incoming data)
  181: 			 * 
  182: 			 * So, if we were gonna drop the connection from too many retransmits,
  183: 			 * don't... instead halve the t_maxseg, which might break up the NULLs and
  184: 			 * let them through
  185: 			 * 
  186: 			 * *sigh*
  187: 			 */
  188: 			
  189: 			tp->t_maxseg >>= 1;
  190: 			if (tp->t_maxseg < 32) {
  191: 				/*
  192: 				 * We tried our best, now the connection must die!
  193: 				 */
  194: 				tp->t_rxtshift = TCP_MAXRXTSHIFT;
  195: 				tcpstat.tcps_timeoutdrop++;
  196: 				tp = tcp_drop(tp, tp->t_softerror);
  197: 				/* tp->t_softerror : ETIMEDOUT); */ /* XXX */
  198: 				return (tp); /* XXX */
  199: 			}
  200: 			
  201: 			/*
  202: 			 * Set rxtshift to 6, which is still at the maximum
  203: 			 * backoff time
  204: 			 */
  205: 			tp->t_rxtshift = 6;
  206: 		}
  207: 		tcpstat.tcps_rexmttimeo++;
  208: 		rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
  209: 		TCPT_RANGESET(tp->t_rxtcur, rexmt,
  210: 		    (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
  211: 		tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
  212: 		/*
  213: 		 * If losing, let the lower level know and try for
  214: 		 * a better route.  Also, if we backed off this far,
  215: 		 * our srtt estimate is probably bogus.  Clobber it
  216: 		 * so we'll take the next rtt measurement as our srtt;
  217: 		 * move the current srtt into rttvar to keep the current
  218: 		 * retransmit times until then.
  219: 		 */
  220: 		if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
  221: /*			in_losing(tp->t_inpcb); */
  222: 			tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
  223: 			tp->t_srtt = 0;
  224: 		}
  225: 		tp->snd_nxt = tp->snd_una;
  226: 		/*
  227: 		 * If timing a segment in this window, stop the timer.
  228: 		 */
  229: 		tp->t_rtt = 0;
  230: 		/*
  231: 		 * Close the congestion window down to one segment
  232: 		 * (we'll open it by one segment for each ack we get).
  233: 		 * Since we probably have a window's worth of unacked
  234: 		 * data accumulated, this "slow start" keeps us from
  235: 		 * dumping all that data as back-to-back packets (which
  236: 		 * might overwhelm an intermediate gateway).
  237: 		 *
  238: 		 * There are two phases to the opening: Initially we
  239: 		 * open by one mss on each ack.  This makes the window
  240: 		 * size increase exponentially with time.  If the
  241: 		 * window is larger than the path can handle, this
  242: 		 * exponential growth results in dropped packet(s)
  243: 		 * almost immediately.  To get more time between 
  244: 		 * drops but still "push" the network to take advantage
  245: 		 * of improving conditions, we switch from exponential
  246: 		 * to linear window opening at some threshold size.
  247: 		 * For a threshold, we use half the current window
  248: 		 * size, truncated to a multiple of the mss.
  249: 		 *
  250: 		 * (the minimum cwnd that will give us exponential
  251: 		 * growth is 2 mss.  We don't allow the threshold
  252: 		 * to go below this.)
  253: 		 */
  254: 		{
  255: 		u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
  256: 		if (win < 2)
  257: 			win = 2;
  258: 		tp->snd_cwnd = tp->t_maxseg;
  259: 		tp->snd_ssthresh = win * tp->t_maxseg;
  260: 		tp->t_dupacks = 0;
  261: 		}
  262: 		(void) tcp_output(tp);
  263: 		break;
  264: 
  265: 	/*
  266: 	 * Persistence timer into zero window.
  267: 	 * Force a byte to be output, if possible.
  268: 	 */
  269: 	case TCPT_PERSIST:
  270: 		tcpstat.tcps_persisttimeo++;
  271: 		tcp_setpersist(tp);
  272: 		tp->t_force = 1;
  273: 		(void) tcp_output(tp);
  274: 		tp->t_force = 0;
  275: 		break;
  276: 
  277: 	/*
  278: 	 * Keep-alive timer went off; send something
  279: 	 * or drop connection if idle for too long.
  280: 	 */
  281: 	case TCPT_KEEP:
  282: 		tcpstat.tcps_keeptimeo++;
  283: 		if (tp->t_state < TCPS_ESTABLISHED)
  284: 			goto dropit;
  285: 
  286: /*		if (tp->t_socket->so_options & SO_KEEPALIVE && */
  287: 		if ((so_options) && tp->t_state <= TCPS_CLOSE_WAIT) {
  288: 		    	if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
  289: 				goto dropit;
  290: 			/*
  291: 			 * Send a packet designed to force a response
  292: 			 * if the peer is up and reachable:
  293: 			 * either an ACK if the connection is still alive,
  294: 			 * or an RST if the peer has closed the connection
  295: 			 * due to timeout or reboot.
  296: 			 * Using sequence number tp->snd_una-1
  297: 			 * causes the transmitted zero-length segment
  298: 			 * to lie outside the receive window;
  299: 			 * by the protocol spec, this requires the
  300: 			 * correspondent TCP to respond.
  301: 			 */
  302: 			tcpstat.tcps_keepprobe++;
  303: #ifdef TCP_COMPAT_42
  304: 			/*
  305: 			 * The keepalive packet must have nonzero length
  306: 			 * to get a 4.2 host to respond.
  307: 			 */
  308: 			tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
  309: 			    tp->rcv_nxt - 1, tp->snd_una - 1, 0);
  310: #else
  311: 			tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
  312: 			    tp->rcv_nxt, tp->snd_una - 1, 0);
  313: #endif
  314: 			tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
  315: 		} else
  316: 			tp->t_timer[TCPT_KEEP] = tcp_keepidle;
  317: 		break;
  318: 
  319: 	dropit:
  320: 		tcpstat.tcps_keepdrops++;
  321: 		tp = tcp_drop(tp, 0); /* ETIMEDOUT); */
  322: 		break;
  323: 	}
  324: 
  325: 	return (tp);
  326: }

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