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[unix-history] / usr / src / sys / netinet / tcp_timer.c

/*
* Copyright (c) 1982 Regents of the University of California.
* All rights reserved.  The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*
*      @(#)tcp_timer.c 6.7 (Berkeley) %G%
*/

#include "param.h"
#include "systm.h"
#include "mbuf.h"
#include "socket.h"
#include "socketvar.h"
#include "protosw.h"
#include "errno.h"

#include "../net/if.h"
#include "../net/route.h"

#include "in.h"
#include "in_pcb.h"
#include "in_systm.h"
#include "ip.h"
#include "ip_var.h"
#include "tcp.h"
#include "tcp_fsm.h"
#include "tcp_seq.h"
#include "tcp_timer.h"
#include "tcp_var.h"
#include "tcpip.h"

int     tcpnodelack = 0;
/*
* Fast timeout routine for processing delayed acks
*/
tcp_fasttimo()
{
       register struct inpcb *inp;
       register struct tcpcb *tp;
       int s = splnet();

       inp = tcb.inp_next;
       if (inp)
       for (; inp != &tcb; 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;
                       (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.
*/
tcp_slowtimo()
{
       register struct inpcb *ip, *ipnxt;
       register struct tcpcb *tp;
       int s = splnet();
       register int i;

       /*
        * Search through tcb's and update active timers.
        */
       ip = tcb.inp_next;
       if (ip == 0) {
               splx(s);
               return;
       }
       for (; ip != &tcb; ip = ipnxt) {
               ipnxt = ip->inp_next;
               tp = intotcpcb(ip);
               if (tp == 0)
                       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);
                               if (ipnxt->inp_prev != ip)
                                       goto tpgone;
                       }
               }
               tp->t_idle++;
               if (tp->t_rtt)
                       tp->t_rtt++;
tpgone:
               ;
       }
       tcp_iss += TCP_ISSINCR/PR_SLOWHZ;               /* increment iss */
       splx(s);
}

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

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

float   tcp_backoff[TCP_MAXRXTSHIFT] =
   { 1.0, 1.2, 1.4, 1.7, 2.0, 3.0, 5.0, 8.0, 16.0, 32.0 };
int     tcpexprexmtbackoff = 0;
/*
* TCP timer processing.
*/
struct tcpcb *
tcp_timers(tp, timer)
       register struct tcpcb *tp;
       int timer;
{

       switch (timer) {

       /*
        * 2 MSL timeout in shutdown went off.  Delete connection
        * control block.
        */
       case TCPT_2MSL:
               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:
               tp->t_rxtshift++;
               if (tp->t_rxtshift > TCP_MAXRXTSHIFT) {
                       tp = tcp_drop(tp, ETIMEDOUT);
                       break;
               }
               /*
                * If losing, let the lower level know
                * and try for a better route.
                */
               if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 2)
                       in_rtchange(tp->t_inpcb);
               TCPT_RANGESET(tp->t_timer[TCPT_REXMT],
                   (int)tp->t_srtt, TCPTV_MIN, TCPTV_MAX);
               if (tcpexprexmtbackoff) {
                       TCPT_RANGESET(tp->t_timer[TCPT_REXMT],
                           tp->t_timer[TCPT_REXMT] << tp->t_rxtshift,
                           TCPTV_MIN, TCPTV_MAX);
               } else {
                       TCPT_RANGESET(tp->t_timer[TCPT_REXMT],
                           tp->t_timer[TCPT_REXMT] *
                               tcp_backoff[tp->t_rxtshift - 1],
                           TCPTV_MIN, TCPTV_MAX);
               }
               tp->snd_nxt = tp->snd_una;
               /*
                * If timing a segment in this window,
                * and we have already gotten some timing estimate,
                * stop the timer.
                */
               if (tp->t_rtt && tp->t_srtt)
                       tp->t_rtt = 0;
               (void) tcp_output(tp);
               break;

       /*
        * Persistance timer into zero window.
        * Force a byte to be output, if possible.
        */
       case TCPT_PERSIST:
               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:
               if (tp->t_state < TCPS_ESTABLISHED)
                       goto dropit;
               if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) {
                       if (tp->t_idle >= TCPTV_MAXIDLE)
                               goto dropit;
                       /*
                        * Saying tp->rcv_nxt-1 lies about what
                        * we have received, and by the protocol spec
                        * requires the correspondent TCP to respond.
                        * Saying tp->snd_una-1 causes the transmitted
                        * byte to lie outside the receive window; this
                        * is important because we don't necessarily
                        * have a byte in the window to send (consider
                        * a one-way stream!)
                        */
                       tcp_respond(tp,
                           tp->t_template, tp->rcv_nxt-1, tp->snd_una-1, 0);
               } else
                       tp->t_idle = 0;
               tp->t_timer[TCPT_KEEP] = TCPTV_KEEP;
               break;
       dropit:
               tp = tcp_drop(tp, ETIMEDOUT);
               break;
       }
       return (tp);
}