Function ifaof_ifpforaddr

freebsd/net/if.c:2098–2141

* Find an interface address specific to an interface best matching * a given address. */

 * a given address.
 */
struct ifaddr *
ifaof_ifpforaddr(const struct sockaddr *addr, struct ifnet *ifp)
{
	struct ifaddr *ifa;
	const char *cp, *cp2, *cp3;
	char *cplim;
	struct ifaddr *ifa_maybe = NULL;
	u_int af = addr->sa_family;

	if (af >= AF_MAX)
		return (NULL);

	NET_EPOCH_ASSERT();
	CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
		if (ifa->ifa_addr->sa_family != af)
			continue;
		if (ifa_maybe == NULL)
			ifa_maybe = ifa;
		if (ifa->ifa_netmask == 0) {
			if (sa_equal(addr, ifa->ifa_addr) ||
			    (ifa->ifa_dstaddr &&
			    sa_equal(addr, ifa->ifa_dstaddr)))
				goto done;
			continue;
		}
		if (ifp->if_flags & IFF_POINTOPOINT) {
			if (sa_equal(addr, ifa->ifa_dstaddr))
				goto done;
		} else {
			cp = addr->sa_data;
			cp2 = ifa->ifa_addr->sa_data;
			cp3 = ifa->ifa_netmask->sa_data;
			cplim = ifa->ifa_netmask->sa_len + (char *)ifa->ifa_netmask;
			for (; cp3 < cplim; cp3++)
				if ((*cp++ ^ *cp2++) & *cp3)
					break;
			if (cp3 == cplim)
				goto done;
		}
	}
	ifa = ifa_maybe;
done:
	return (ifa);
}

/*
 * See whether new ifa is better than current one: