tcp_timer.pc

无线自组织网络的一个协议仿真软件

/*
 * GloMoSim is COPYRIGHTED software.  Release 2.02 of GloMoSim is available 
 * at no cost to educational users only.
 *
 * Commercial use of this software requires a separate license.  No cost,
 * evaluation licenses are available for such purposes; please contact
 * [e-mail]
 *
 * By obtaining copies of this and any other files that comprise GloMoSim2.02,
 * you, the Licensee, agree to abide by the following conditions and
 * understandings with respect to the copyrighted software:
 *
 * 1.Permission to use, copy, and modify this software and its documentation
 *   for education and non-commercial research purposes only is hereby granted
 *   to Licensee, provided that the copyright notice, the original author's
 *   names and unit identification, and this permission notice appear on all
 *   such copies, and that no charge be made for such copies. Any entity
 *   desiring permission to use this software for any commercial or
 *   non-educational research purposes should contact: 
 *
 *   Professor Rajive Bagrodia 
 *   University of California, Los Angeles 
 *   Department of Computer Science 
 *   Box 951596 
 *   3532 Boelter Hall 
 *   Los Angeles, CA 90095-1596 
 *   [e-mail]
 *
 * 2.NO REPRESENTATIONS ARE MADE ABOUT THE SUITABILITY OF THE SOFTWARE FOR ANY
 *   PURPOSE. IT IS PROVIDED "AS IS" WITHOUT EXPRESS OR IMPLIED WARRANTY.
 *
 * 3.Neither the software developers, the Parallel Computing Lab, UCLA, or any
 *   affiliate of the UC system shall be liable for any damages suffered by
 *   Licensee from the use of this software.
 */

// Use the latest version of Parsec if this line causes a compiler error.
/*
 * $Id: tcp_timer.pc,v 1.2 1999/09/05 05:24:49 jmartin Exp $
 *
 * Ported from FreeBSD 2.2.2.
 * This file contains TCP timer management routines.
 */

/*
 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
 *  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 4. 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 8.2 (Berkeley) 5/24/95
 *  $Id: tcp_timer.pc,v 1.2 1999/09/05 05:24:49 jmartin Exp $
 */

#include <stdio.h>
#include <stdlib.h>
 
#include "main.h"

#include "in_pcb.h"
#include "ip.h"
#include "tcpip.h"
#include "tcp_config.h"
#include "tcp_fsm.h"
#include "tcp_hdr.h"
#include "tcp_proto.h"
#include "tcp_seq.h"
#include "tcp_timer.h"
#include "tcp_var.h"

static struct tcpcb *tcp_timers(GlomoNode *, struct tcpcb *, int,
                                unsigned long, struct tcpstat *);

/*
 * Fast timeout routine for processing delayed acks
 */
void
tcp_fasttimo(node, head, tcp_now, tcp_stat)
    GlomoNode *node;
    struct inpcb *head;
    unsigned long tcp_now;
    struct tcpstat *tcp_stat;
{
    struct inpcb *inp;
    struct tcpcb *tp;

    inp = head->inp_next;
    if (inp) {
        for (; inp != head; inp = inp->inp_next) {
            if ((tp = (struct tcpcb *) inp->inp_ppcb) &&
                (tp->t_flags & TF_DELACK)) {
                tp->t_flags &= ~TF_DELACK;
                tp->t_flags |= TF_ACKNOW;
                if (tcp_stat)
                    tcp_stat->tcps_delack++;
                tcp_output(node, tp, tcp_now, tcp_stat);
            }
        }
    }
}   


/*
 * 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(node, head, tcp_iss, tcp_now, tcp_stat)
    GlomoNode *node; 
    struct inpcb *head;
    tcp_seq *tcp_iss;
    unsigned long *tcp_now;
    struct tcpstat *tcp_stat;
{
    struct inpcb *ip, *ipnxt;
    struct tcpcb *tp;
    int i;

    ip = head->inp_next;
    if (ip == NULL) {
        return;
    }
    /*
     * Search through inpcb's and update active timers.
     */
    for (; ip != head; ip = ipnxt) {
        ipnxt = ip->inp_next;
        tp = intotcpcb(ip);
        if (tp == 0 || tp->t_state == TCPS_LISTEN)
            continue;
        for (i = 0; i < TCPT_NTIMERS; i++) {
            if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
                (void) tcp_timers(node, tp, i,
                                  *tcp_now, tcp_stat);
                if (ipnxt->inp_prev != ip)
                    goto tpgone;
            }
        }
        tp->t_idle++;
        tp->t_duration++;
        if (tp->t_rtt)
            tp->t_rtt++;
tpgone:
        ;
    }
    *tcp_iss += TCP_ISSINCR/PR_SLOWHZ;      /* increment iss for timestamps */
    (*tcp_now) ++; 
}

    
/*
 * Cancel all timers for TCP tp.
 */
void
tcp_canceltimers(tp)
    struct tcpcb *tp;
{
    int i;

    for (i = 0; i < TCPT_NTIMERS; i++)
    {
        tp->t_timer[i] = 0;
    }
}

/*
 * TCP timer processing.
 */
static struct tcpcb *
tcp_timers(node, tp, timer, tcp_now, tcp_stat)
    GlomoNode *node;
    struct tcpcb *tp;
    int timer;
    unsigned long tcp_now;
    struct tcpstat *tcp_stat;
{
    int rexmt;

    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 <= TCPTV_MAXIDLE)
            tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL;
        else
            tp = tcp_close(node, tp, tcp_stat);
        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:
        if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
            tp->t_rxtshift = TCP_MAXRXTSHIFT;
            if (tcp_stat)
                tcp_stat->tcps_timeoutdrop++;
            tp = tcp_drop(node, tp, tcp_now, tcp_stat);
            break;
        }
        if (tcp_stat)
            tcp_stat->tcps_rexmttimeo++;
        rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];

        TCPT_RANGESET(tp->t_rxtcur, rexmt,
                      tp->t_rttmin, TCPTV_REXMTMAX);
        tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
        /*
         * 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;
        /*
         * Force a segment to be sent.
         */
        tp->t_flags |= TF_ACKNOW;
        /*
         * If timing a segment in this window, stop the timer.
         * The retransmitted segment shouldn't be timed. 
         */
        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 threshhold size.
         * For a threshhold, 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 threshhold
         * to go below this.)
         */
        {
            unsigned int win;
            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;
        }
        tcp_output(node, tp, tcp_now, tcp_stat);
        break;

    /*
     * Persistance timer into zero window.
     * Force a byte to be output, if possible.
     */
    case TCPT_PERSIST:
        if (tcp_stat)
            tcp_stat->tcps_persisttimeo++;
        /*
         * Hack: if the peer is dead/unreachable, we do not
         * time out if the window is closed.  After a full
         * backoff, drop the connection if the idle time
         * (no responses to probes) reaches the maximum
         * backoff that we would use if retransmitting.
         */
        if (tp->t_rxtshift == TCP_MAXRXTSHIFT) {
            unsigned long maxidle = TCP_REXMTVAL(tp);
            if (maxidle < tp->t_rttmin)
                maxidle = tp->t_rttmin;
            maxidle *= tcp_totbackoff;
            if (tp->t_idle >= TCPTV_KEEP_IDLE ||
                tp->t_idle >= maxidle) {
                if (tcp_stat)
                    tcp_stat->tcps_persistdrop++;
                tp = tcp_drop(node, tp, tcp_now, tcp_stat);
                break;
            }
        }
        tcp_setpersist(tp);
        tp->t_force = 1;
        tcp_output(node, tp, tcp_now, tcp_stat);
        tp->t_force = 0;
        break;

    /*
     * Keep-alive timer went off; send something
     * or drop connection if idle for too long.
     */
    case TCPT_KEEP:
        if (tcp_stat)
            tcp_stat->tcps_keeptimeo++;
        if (tp->t_state < TCPS_ESTABLISHED)
            goto dropit;
        if (TCP_ALWAYS_KEEPALIVE && tp->t_state <= TCPS_CLOSING) {

            /*
             * If the connection has been idle for more than the sum of
             * TCPTV_KEEP_IDLE (set to 2 hours) and TCPTV_MAXIDLE
             * (set to the total time taken to send all the probes),
             * it's time to drop the connection.
             */  
            if (tp->t_idle >= TCPTV_KEEP_IDLE + TCPTV_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.
             */
            if (tcp_stat)
                tcp_stat->tcps_keepprobe++;
            tcp_respond(node, tp, tp->t_template,
                        0, tp->rcv_nxt, tp->snd_una - 1,
                        0, tcp_stat);
 
            tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
        } else {
            /*
             * If the option TCP_ALWAYS_KEEPALIVE is set to 0
             * or the connection state is greater than TCPS_CLOSING,
             * reset the keepalive timer to TCPTV_KEEP_IDLE.
             */  
            tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
        } 
        break;
    dropit:
        if (tcp_stat) {
            /*
             * Note that this counter counts connection drops due to
             * failure in connection establishment and the keepalive
             * timer timeouts
             */ 
            tcp_stat->tcps_keepdrops++;
        }
        tp = tcp_drop(node, tp, tcp_now, tcp_stat);
        break;
    }
    return (tp);
}