[IPV4]: multicast API "join" issues

        This patch corrects a few problems with the IP_ADD_MEMBERSHIP
socket option:

1) The existing code makes an attempt at reference counting joins when
   using the ip_mreqn/imr_ifindex interface. Joining the same group
   on the same socket is an error, whatever the API. This leads to
   unexpected results when mixing ip_mreqn by index with ip_mreqn by
   address, ip_mreq, or other API's. For example, ip_mreq followed by
   ip_mreqn of the same group will "work" while the same two reversed
   will not.
           Fixed to always return EADDRINUSE on a duplicate join and
   removed the (now unused) reference count in ip_mc_socklist.

2) The group-search list in ip_mc_join_group() is comparing a full 
   ip_mreqn structure and all of it must match for it to find the
   group. This doesn't correctly match a group that was joined with
   ip_mreq or ip_mreqn with an address (with or without an index). It
   also doesn't match groups that are joined by different addresses on
   the same interface. All of these are the same multicast group,
   which is identified by group address and interface index.
           Fixed the check to correctly match groups so we don't get
   duplicate group entries on the ip_mc_socklist.

3) The old code allocates a multicast address before searching for
   duplicates requiring it to free in various error cases. This
   patch moves the allocate until after the search and
   igmp_max_memberships check, so never a need to allocate, then free
   an entry.
Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/igmp.h

@@ -148,7 +148,6 @@ struct ip_sf_socklist
 struct ip_mc_socklist
 {
 	struct ip_mc_socklist	*next;
-	int			count;
 	struct ip_mreqn		multi;
 	unsigned int		sfmode;		/* MCAST_{INCLUDE,EXCLUDE} */
 	struct ip_sf_socklist	*sflist;

net/ipv4/igmp.c

@@ -1615,9 +1615,10 @@ int ip_mc_join_group(struct sock *sk , struct ip_mreqn *imr)
 {
 	int err;
 	u32 addr = imr->imr_multiaddr.s_addr;
-	struct ip_mc_socklist *iml, *i;
+	struct ip_mc_socklist *iml=NULL, *i;
 	struct in_device *in_dev;
 	struct inet_sock *inet = inet_sk(sk);
+	int ifindex;
 	int count = 0;
 
 	if (!MULTICAST(addr))
@@ -1633,37 +1634,30 @@ int ip_mc_join_group(struct sock *sk , struct ip_mreqn *imr)
 		goto done;
 	}
 
-	iml = (struct ip_mc_socklist *)sock_kmalloc(sk, sizeof(*iml), GFP_KERNEL);
-
 	err = -EADDRINUSE;
+	ifindex = imr->imr_ifindex;
 	for (i = inet->mc_list; i; i = i->next) {
-		if (memcmp(&i->multi, imr, sizeof(*imr)) == 0) {
-			/* New style additions are reference counted */
-			if (imr->imr_address.s_addr == 0) {
-				i->count++;
-				err = 0;
-			}
+		if (i->multi.imr_multiaddr.s_addr == addr &&
+		    i->multi.imr_ifindex == ifindex)
 			goto done;
-		}
 		count++;
 	}
 	err = -ENOBUFS;
-	if (iml == NULL || count >= sysctl_igmp_max_memberships)
+	if (count >= sysctl_igmp_max_memberships)
+		goto done;
+	iml = (struct ip_mc_socklist *)sock_kmalloc(sk,sizeof(*iml),GFP_KERNEL);
+	if (iml == NULL)
 		goto done;
+
 	memcpy(&iml->multi, imr, sizeof(*imr));
 	iml->next = inet->mc_list;
-	iml->count = 1;
 	iml->sflist = NULL;
 	iml->sfmode = MCAST_EXCLUDE;
 	inet->mc_list = iml;
 	ip_mc_inc_group(in_dev, addr);
-	iml = NULL;
 	err = 0;
-
 done:
 	rtnl_shunlock();
-	if (iml)
-		sock_kfree_s(sk, iml, sizeof(*iml));
 	return err;
 }
 
@@ -1704,12 +1698,6 @@ int ip_mc_leave_group(struct sock *sk, struct ip_mreqn *imr)
 			in_dev = inetdev_by_index(iml->multi.imr_ifindex);
 			if (in_dev)
 				(void) ip_mc_leave_src(sk, iml, in_dev);
-			if (--iml->count) {
-				rtnl_unlock();
-				if (in_dev)
-					in_dev_put(in_dev);
-				return 0;
-			}
 
 			*imlp = iml->next;
 
@@ -1755,7 +1743,8 @@ int ip_mc_source(int add, int omode, struct sock *sk, struct
 	err = -EADDRNOTAVAIL;
 
 	for (pmc=inet->mc_list; pmc; pmc=pmc->next) {
-		if (memcmp(&pmc->multi, mreqs, 2*sizeof(__u32)) == 0)
+		if (pmc->multi.imr_multiaddr.s_addr == imr.imr_multiaddr.s_addr
+		    && pmc->multi.imr_ifindex == imr.imr_ifindex)
 			break;
 	}
 	if (!pmc)		/* must have a prior join */