xref: /csrg-svn/sys/netinet/tcp_timer.c (revision 23194)

/*
 * 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) 06/08/85
 */

#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);
}