rtget.c

来自「TCP-IP红宝书源代码」· C语言 代码 · 共 39 行

/* rtget.c - rtget */

#include <conf.h>
#include <kernel.h>
#include <network.h>

/*------------------------------------------------------------------------
 *  rtget  -  get the route for a given IP destination
 *------------------------------------------------------------------------
 */
struct route *
rtget(IPaddr dest, Bool local)
{
	struct	route	*prt;
	int		hv;

	if (!Route.ri_valid)
		rtinit();
	wait(Route.ri_mutex);
	hv = rthash(dest);
	for (prt=rttable[hv]; prt; prt=prt->rt_next) {
		if (prt->rt_ttl <= 0)
			continue;		/* route has expired */
		if (netmatch(dest, prt->rt_net, prt->rt_mask, local))
			if (prt->rt_metric < RTM_INF)
				break;
	}
	if (prt == 0)
		prt = Route.ri_default;	/* may be NULL too... */
	if (prt != 0 && prt->rt_metric >= RTM_INF)
		prt = 0;
	if (prt) {
		prt->rt_refcnt++;
		prt->rt_usecnt++;
	}
	signal(Route.ri_mutex);
	return prt;
}