[IPV4]: multicast API "join" issues

1) Changes IP_ADD_SOURCE_MEMBERSHIP and MCAST_JOIN_SOURCE_GROUP to ignore
   EADDRINUSE errors on a "courtesy join" -- prior membership or not
   is ok for these.

2) Adds "leave group" equivalence of (INCLUDE, empty) filters in the 
   delta-based API. Without this, mixing delta-based API calls that
   end in an (INCLUDE, empty) filter would not allow a subsequent
   regular IP_ADD_MEMBERSHIP. It also frees socket buffer memory that
   isn't needed for both the multicast group record and source filter.
Signed-off-by: NDavid L Stevens <dlstevens@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/igmp.c

@@ -1724,6 +1724,7 @@ int ip_mc_source(int add, int omode, struct sock *sk, struct
 	struct in_device *in_dev = NULL;
 	struct inet_sock *inet = inet_sk(sk);
 	struct ip_sf_socklist *psl;
+	int leavegroup = 0;
 	int i, j, rv;
 
 	if (!MULTICAST(addr))
@@ -1775,6 +1776,12 @@ int ip_mc_source(int add, int omode, struct sock *sk, struct
 		if (rv)		/* source not found */
 			goto done;
 
+		/* special case - (INCLUDE, empty) == LEAVE_GROUP */
+		if (psl->sl_count == 1 && omode == MCAST_INCLUDE) {
+			leavegroup = 1;
+			goto done;
+		}
+
 		/* update the interface filter */
 		ip_mc_del_src(in_dev, &mreqs->imr_multiaddr, omode, 1, 
 			&mreqs->imr_sourceaddr, 1);
@@ -1831,6 +1838,8 @@ int ip_mc_source(int add, int omode, struct sock *sk, struct
 		&mreqs->imr_sourceaddr, 1);
 done:
 	rtnl_shunlock();
+	if (leavegroup)
+		return ip_mc_leave_group(sk, &imr);
 	return err;
 }
 

net/ipv4/ip_sockglue.c

@@ -677,11 +677,11 @@ int ip_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
 				mreq.imr_address.s_addr = mreqs.imr_interface;
 				mreq.imr_ifindex = 0;
 				err = ip_mc_join_group(sk, &mreq);
-				if (err)
+				if (err && err != -EADDRINUSE)
 					break;
 				omode = MCAST_INCLUDE;
 				add = 1;
-			} else /*IP_DROP_SOURCE_MEMBERSHIP */ {
+			} else /* IP_DROP_SOURCE_MEMBERSHIP */ {
 				omode = MCAST_INCLUDE;
 				add = 0;
 			}
@@ -754,7 +754,7 @@ int ip_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
 				mreq.imr_address.s_addr = 0;
 				mreq.imr_ifindex = greqs.gsr_interface;
 				err = ip_mc_join_group(sk, &mreq);
-				if (err)
+				if (err && err != -EADDRINUSE)
 					break;
 				greqs.gsr_interface = mreq.imr_ifindex;
 				omode = MCAST_INCLUDE;