igmp: export symbol ip_mc_leave_group

Needed for VXLAN.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 3479b98..736ab70 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1904,6 +1904,7 @@
 	rtnl_unlock();
 	return ret;
 }
+EXPORT_SYMBOL(ip_mc_leave_group);
 
 int ip_mc_source(int add, int omode, struct sock *sk, struct
 	ip_mreq_source *mreqs, int ifindex)