From a38b1c8c5e4ba2aec774ecf4286d2328efec7b84 Mon Sep 17 00:00:00 2001
From: Randall Stewart <rrs@FreeBSD.org>
Date: Wed, 19 Jan 2011 19:07:16 +0000
Subject: [PATCH] Fix a bug where Multicast packets sent from a udp endpoint
 may end up echoing back to the sender even with OUT joining the multi-cast
 group.

Reviewed by:	gnn, bms, bz?
Obtained from:	deischen (with help from)
---
 sys/netinet/udp_usrreq.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/sys/netinet/udp_usrreq.c b/sys/netinet/udp_usrreq.c
index 3bfe788a2887..c9b4f3fc74e6 100644
--- a/sys/netinet/udp_usrreq.c
+++ b/sys/netinet/udp_usrreq.c
@@ -479,11 +479,13 @@ udp_input(struct mbuf *m, int off)
 			 * and source-specific multicast. [RFC3678]
 			 */
 			imo = inp->inp_moptions;
-			if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) &&
-			    imo != NULL) {
+			if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
 				struct sockaddr_in	 group;
 				int			 blocked;
-
+				if(imo == NULL) {
+					INP_RUNLOCK(inp);
+					continue;
+				}
 				bzero(&group, sizeof(struct sockaddr_in));
 				group.sin_len = sizeof(struct sockaddr_in);
 				group.sin_family = AF_INET;