This is a regression introduced by:
	commit 
3fc2de2faba387218bdf9dbc6b13f513ac3b060a
	Author: stephen hemminger <stephen@networkplumber.org>
	Date:   Thu Jul 18 08:40:15 2013 -0700
	    vxlan: fix igmp races
Before this commit, the old code was:
       if (vxlan_group_used(vn, vxlan->default_dst.remote_ip))
               ip_mc_join_group(sk, &mreq);
       else
               ip_mc_leave_group(sk, &mreq);
therefore we shoud check vxlan_group_used(), not its opposite,
for igmp_join.
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
                return -ENOTCONN;
 
        if (IN_MULTICAST(ntohl(vxlan->default_dst.remote_ip)) &&
-           ! vxlan_group_used(vn, vxlan->default_dst.remote_ip)) {
+           vxlan_group_used(vn, vxlan->default_dst.remote_ip)) {
                vxlan_sock_hold(vs);
                dev_hold(dev);
                queue_work(vxlan_wq, &vxlan->igmp_join);