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//==========================================================================

//

//      sys/netinet/tcp_timer.c

//

//     

//

//==========================================================================

//####BSDCOPYRIGHTBEGIN####

//

// -------------------------------------------

//

// Portions of this software may have been derived from OpenBSD or other sources,

// and are covered by the appropriate copyright disclaimers included herein.

//

// -------------------------------------------

//

//####BSDCOPYRIGHTEND####

//==========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):    gthomas

// Contributors: gthomas

// Date:         2000-01-10

// Purpose:      

// Description:  

//              

//

//####DESCRIPTIONEND####

//

//==========================================================================

/*      $OpenBSD: tcp_timer.c,v 1.15 1999/11/15 05:50:59 hugh Exp $     */

/*      $NetBSD: tcp_timer.c,v 1.14 1996/02/13 23:44:09 christos Exp $  */

/*

 * 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. 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 8.1 (Berkeley) 6/10/93

 */

#ifndef TUBA_INCLUDE

#include <sys/param.h>

#ifndef __ECOS

#include <sys/systm.h>

#endif

#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 <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>

#ifndef __ECOS

#include <dev/rndvar.h>

#endif

int     tcp_keepidle = TCPTV_KEEP_IDLE;

int     tcp_keepintvl = TCPTV_KEEPINTVL;

int     tcp_maxpersistidle = TCPTV_KEEP_IDLE;   /* max idle time in persist */

int     tcp_maxidle;

#endif /* TUBA_INCLUDE */

/*

 * Fast timeout routine for processing delayed acks

 */

void

tcp_fasttimo()

{

        register struct inpcb *inp;

        register struct tcpcb *tp;

        int s;

        s = splsoftnet();

        inp = tcbtable.inpt_queue.cqh_first;

        if (inp)                                                /* XXX */

        for (; inp != (struct inpcb *)&tcbtable.inpt_queue;

            inp = inp->inp_queue.cqe_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;

        int s;

        register long i;

        s = splsoftnet();

        tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;

        /*

         * Search through tcb's and update active timers.

         */

        ip = tcbtable.inpt_queue.cqh_first;

        if (ip == (struct inpcb *)0) {                           /* XXX */

                splx(s);

                return;

        }

        for (; ip != (struct inpcb *)&tcbtable.inpt_queue; ip = ipnxt) {

                ipnxt = ip->inp_queue.cqe_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_usrreq(tp->t_inpcb->inp_socket,

                                    PRU_SLOWTIMO, (struct mbuf *)0,

                                    (struct mbuf *)i, (struct mbuf *)0);

                                /* XXX NOT MP SAFE */

                                if ((ipnxt == (void *)&tcbtable.inpt_queue &&

                                    tcbtable.inpt_queue.cqh_last != ip) ||

                                    ipnxt->inp_queue.cqe_prev != ip)

                                        goto tpgone;

                        }

                }

                tp->t_idle++;

                if (tp->t_rtt)

                        tp->t_rtt++;

tpgone:

                ;

        }

#ifdef TCP_COMPAT_42

        tcp_iss += TCP_ISSINCR/PR_SLOWHZ;               /* increment iss */

        if ((int)tcp_iss < 0)

                tcp_iss = 0;                             /* XXX */

#else /* TCP_COMPAT_42 */

        tcp_iss += arc4random() % (2 * TCP_ISSINCR / PR_SLOWHZ) + 1; /* increment iss */

#endif /* !TCP_COMPAT_42 */

        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 };

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

/*

 * TCP timer processing.

 */

struct tcpcb *

tcp_timers(tp, timer)

        register struct tcpcb *tp;

        int timer;

{

        short rto;

#ifdef TCP_SACK

        struct sackhole *p, *q;

        /*

         * Free SACK holes for 2MSL and REXMT timers.

         */

        if (timer == TCPT_2MSL || timer == TCPT_REXMT) {

                q = p = tp->snd_holes;

                while (p != 0) {

                        q = p->next;

                        free(p, M_PCB);

                        p = q;

                }

                tp->snd_holes = 0;

#if defined(TCP_SACK) && defined(TCP_FACK)

                tp->snd_fack = tp->snd_una;

                tp->retran_data = 0;

                tp->snd_awnd = 0;

#endif /* TCP_FACK */

        }

#endif /* TCP_SACK */

        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++;

                rto = TCP_REXMTVAL(tp);

                if (rto < tp->t_rttmin)

                        rto = tp->t_rttmin;

                TCPT_RANGESET((long) tp->t_rxtcur,

                    rto * tcp_backoff[tp->t_rxtshift],

                    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;

#if defined(TCP_SACK) || defined(TCP_NEWRENO)

                /*

                 * Note:  We overload snd_last to function also as the

                 * snd_last variable described in RFC 2582

                 */

                tp->snd_last = tp->snd_max;

#endif /* TCP_SACK or TCP_NEWRENO */

                /*

                 * 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_long win = ulmin(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.

                 */

                rto = TCP_REXMTVAL(tp);

                if (rto < tp->t_rttmin)

                        rto = tp->t_rttmin;

                if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&

                    (tp->t_idle >= tcp_maxpersistidle ||

                     tp->t_idle >= rto * tcp_totbackoff)) {

                        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 (TCPS_HAVEESTABLISHED(tp->t_state) == 0)

                        goto dropit;

                if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&

                    tp->t_state <= TCPS_CLOSE_WAIT) {

                        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,

                                mtod(tp->t_template, caddr_t),

                                (struct mbuf *)NULL,

                                tp->rcv_nxt - 1, tp->snd_una - 1, 0);

#else

                        tcp_respond(tp,

                                mtod(tp->t_template, caddr_t),

                                (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 */