source: rtems/c/src/lib/libnetworking/netinet/tcp_timer.c @ 39e6e65a

/*
 * 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
 *      $Id$
 */

#include "opt_tcpdebug.h"

#ifndef TUBA_INCLUDE
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/errno.h>

#include <machine/cpu.h>        /* before tcp_seq.h, for tcp_random18() */

#include <net/if.h>
#include <net/route.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif

int     tcp_keepinit = TCPTV_KEEP_INIT;
SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,
        CTLFLAG_RW, &tcp_keepinit , 0, "");

int     tcp_keepidle = TCPTV_KEEP_IDLE;
SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,
        CTLFLAG_RW, &tcp_keepidle , 0, "");

static int      tcp_keepintvl = TCPTV_KEEPINTVL;
SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,
        CTLFLAG_RW, &tcp_keepintvl , 0, "");

static int      always_keepalive = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive,
        CTLFLAG_RW, &always_keepalive , 0, "");

static int      tcp_keepcnt = TCPTV_KEEPCNT;
        /* max idle probes */
static int      tcp_maxpersistidle = TCPTV_KEEP_IDLE;
        /* max idle time in persist */
int     tcp_maxidle;
#else /* TUBA_INCLUDE */

static  int tcp_maxpersistidle;
#endif /* TUBA_INCLUDE */

/*
 * Fast timeout routine for processing delayed acks
 */
void
tcp_fasttimo()
{
        register struct inpcb *inp;
        register struct tcpcb *tp;
        int s;

        s = splnet();

        for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) {
                if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
                    (tp->t_flags & TF_DELACK)) {
                        tp->t_flags &= ~TF_DELACK;
                        tp->t_flags |= TF_ACKNOW;
                        tcpstat.tcps_delack++;
                        (void) tcp_output(tp);
                }
        }
        splx(s);
}

/*
 * 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()
{
        register struct inpcb *ip, *ipnxt;
        register struct tcpcb *tp;
        register int i;
        int s;
#ifdef TCPDEBUG
        int ostate;
#endif

        s = splnet();

        tcp_maxidle = tcp_keepcnt * tcp_keepintvl;

        ip = tcb.lh_first;
        if (ip == NULL) {
                splx(s);
                return;
        }
        /*
         * Search through tcb's and update active timers.
         */
        for (; ip != NULL; ip = ipnxt) {
                ipnxt = ip->inp_list.le_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) {
#ifdef TCPDEBUG
                                ostate = tp->t_state;
#endif
                                tp = tcp_timers(tp, i);
                                if (tp == NULL)
                                        goto tpgone;
#ifdef TCPDEBUG
                                if (tp->t_inpcb->inp_socket->so_options
                                    & SO_DEBUG)
                                        tcp_trace(TA_USER, ostate, tp,
                                                  (struct tcpiphdr *)0,
                                                  PRU_SLOWTIMO);
#endif
                        }
                }
                tp->t_idle++;
                tp->t_duration++;
                if (tp->t_rtt)
                        tp->t_rtt++;
tpgone:
                ;
        }
        tcp_iss += TCP_ISSINCR/PR_SLOWHZ;               /* increment iss */
#ifdef TCP_COMPAT_42
        if ((int)tcp_iss < 0)
                tcp_iss = TCP_ISSINCR;                  /* XXX */
#endif
        tcp_now++;                                      /* for timestamps */
        splx(s);
}
#ifndef TUBA_INCLUDE

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

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

int     tcp_backoff[TCP_MAXRXTSHIFT + 1] =
    { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };

static int tcp_totbackoff = 511;        /* sum of tcp_backoff[] */

/*
 * TCP timer processing.
 */
struct tcpcb *
tcp_timers(tp, timer)
        register struct tcpcb *tp;
        int timer;
{
        register 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 <= tcp_maxidle)
                        tp->t_timer[TCPT_2MSL] = tcp_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:
                if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
                        tp->t_rxtshift = TCP_MAXRXTSHIFT;
                        tcpstat.tcps_timeoutdrop++;
                        tp = tcp_drop(tp, tp->t_softerror ?
                            tp->t_softerror : ETIMEDOUT);
                        break;
                }
                tcpstat.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 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) {
                        in_losing(tp->t_inpcb);
                        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.
                 */
                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.)
                 */
                {
                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;

        /*
         * Persistance timer into zero window.
         * Force a byte to be output, if possible.
         */
        case TCPT_PERSIST:
                tcpstat.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) {
                        u_long maxidle = TCP_REXMTVAL(tp);
                        if (maxidle < tp->t_rttmin)
                                maxidle = tp->t_rttmin;
                        maxidle *= tcp_totbackoff;
                        if (tp->t_idle >= tcp_maxpersistidle ||
                            tp->t_idle >= maxidle) {
                                tcpstat.tcps_persistdrop++;
                                tp = tcp_drop(tp, ETIMEDOUT);
                                break;
                        }
                }
                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:
                tcpstat.tcps_keeptimeo++;
                if (tp->t_state < TCPS_ESTABLISHED)
                        goto dropit;
                if ((always_keepalive ||
                    tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) &&
                    tp->t_state <= TCPS_CLOSING) {
                        if (tp->t_idle >= tcp_keepidle + 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.
                         */
                        tcpstat.tcps_keepprobe++;
#ifdef TCP_COMPAT_42
                        /*
                         * The keepalive packet must have nonzero length
                         * to get a 4.2 host to respond.
                         */
                        tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
                            tp->rcv_nxt - 1, tp->snd_una - 1, 0);
#else
                        tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
                            tp->rcv_nxt, tp->snd_una - 1, 0);
#endif
                        tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
                } else
                        tp->t_timer[TCPT_KEEP] = tcp_keepidle;
                break;
        dropit:
                tcpstat.tcps_keepdrops++;
                tp = tcp_drop(tp, ETIMEDOUT);
                break;
        }
        return (tp);
}
#endif /* TUBA_INCLUDE */