timer.c

早期freebsd实现

/*
 * Copyright (c) 1985, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This file includes significant work done at Cornell University by
 * Bill Nesheim.  That work included by permission.
 *
 * 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.
 */

#ifndef lint
static char sccsid[] = "@(#)timer.c	8.1 (Berkeley) 6/5/93";
#endif /* not lint */

/*
 * Routing Table Management Daemon
 */
#include "defs.h"

int	timeval = -TIMER_RATE;

/*
 * Timer routine.  Performs routing information supply
 * duties and manages timers on routing table entries.
 */
void
timer()
{
	register struct rthash *rh;
	register struct rt_entry *rt;
	struct rthash *base = hosthash;
	int doinghost = 1, timetobroadcast;

	timeval += TIMER_RATE;
	if (lookforinterfaces && (timeval % CHECK_INTERVAL) == 0)
		ifinit();
	timetobroadcast = supplier && (timeval % SUPPLY_INTERVAL) == 0;
again:
	for (rh = base; rh < &base[ROUTEHASHSIZ]; rh++) {
		rt = rh->rt_forw;
		for (; rt != (struct rt_entry *)rh; rt = rt->rt_forw) {
			/*
			 * We don't advance time on a routing entry for
			 * a passive gateway or that for our only interface. 
			 * The latter is excused because we don't act as
			 * a routing information supplier and hence would
			 * time it out.  This is fair as if it's down
			 * we're cut off from the world anyway and it's
			 * not likely we'll grow any new hardware in
			 * the mean time.
			 */
			if (!(rt->rt_state & RTS_PASSIVE) &&
			    (supplier || !(rt->rt_state & RTS_INTERFACE)))
				rt->rt_timer += TIMER_RATE;
			if (rt->rt_timer >= EXPIRE_TIME)
				rt->rt_metric = HOPCNT_INFINITY;
			if (rt->rt_timer >= GARBAGE_TIME) {
				rt = rt->rt_back;
				/* Perhaps we should send a REQUEST for this route? */
				rtdelete(rt->rt_forw);
				continue;
			}
			if (rt->rt_state & RTS_CHANGED) {
				rt->rt_state &= ~RTS_CHANGED;
				/* don't send extraneous packets */
				if (!supplier || timetobroadcast)
					continue;
				msg->rip_cmd = htons(RIPCMD_RESPONSE);
				msg->rip_nets[0].rip_dst =
					(satons_addr(rt->rt_dst)).x_net;
				msg->rip_nets[0].rip_metric =
				   	htons(min(rt->rt_metric+1, HOPCNT_INFINITY));
				toall(sndmsg);
			}
		}
	}
	if (doinghost) {
		doinghost = 0;
		base = nethash;
		goto again;
	}
	if (timetobroadcast)
		toall(supply);
	alarm(TIMER_RATE);
}

/*
 * On hangup, let everyone know we're going away.
 */
void
hup()
{
	register struct rthash *rh;
	register struct rt_entry *rt;
	struct rthash *base = hosthash;
	int doinghost = 1;

	if (supplier) {
again:
		for (rh = base; rh < &base[ROUTEHASHSIZ]; rh++) {
			rt = rh->rt_forw;
			for (; rt != (struct rt_entry *)rh; rt = rt->rt_forw)
				rt->rt_metric = HOPCNT_INFINITY;
		}
		if (doinghost) {
			doinghost = 0;
			base = nethash;
			goto again;
		}
		toall(supply);
	}
	exit(1);
}