Function icmp_reflect

freebsd/netinet/ip_icmp.c:756–933

* Reflect the ip packet back to the source */

 * Reflect the ip packet back to the source
 */
static void
icmp_reflect(struct mbuf *m)
{
	struct rm_priotracker in_ifa_tracker;
	struct ip *ip = mtod(m, struct ip *);
	struct ifaddr *ifa;
	struct ifnet *ifp;
	struct in_ifaddr *ia;
	struct in_addr t;
	struct nhop_object *nh;
	struct mbuf *opts = NULL;
	int optlen = (ip->ip_hl << 2) - sizeof(struct ip);

	NET_EPOCH_ASSERT();

	if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
	    IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) ||
	    IN_ZERONET(ntohl(ip->ip_src.s_addr)) ) {
		m_freem(m);	/* Bad return address */
		ICMPSTAT_INC(icps_badaddr);
		goto done;	/* Ip_output() will check for broadcast */
	}

	t = ip->ip_dst;
	ip->ip_dst = ip->ip_src;

	/*
	 * Source selection for ICMP replies:
	 *
	 * If the incoming packet was addressed directly to one of our
	 * own addresses, use dst as the src for the reply.
	 */
	IN_IFADDR_RLOCK(&in_ifa_tracker);
	LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash) {
		if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr) {
			t = IA_SIN(ia)->sin_addr;
			IN_IFADDR_RUNLOCK(&in_ifa_tracker);
			goto match;
		}
	}
	IN_IFADDR_RUNLOCK(&in_ifa_tracker);

	/*
	 * If the incoming packet was addressed to one of our broadcast
	 * addresses, use the first non-broadcast address which corresponds
	 * to the incoming interface.
	 */
	ifp = m->m_pkthdr.rcvif;
	if (ifp != NULL && ifp->if_flags & IFF_BROADCAST) {
		CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
			if (ifa->ifa_addr->sa_family != AF_INET)
				continue;
			ia = ifatoia(ifa);
			if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
			    t.s_addr) {
				t = IA_SIN(ia)->sin_addr;
				goto match;
			}