vxlan: Avoid creating fdb entry with NULL destination

Commit afbd8bae
   vxlan: add implicit fdb entry for default destination
creates an implicit fdb entry for default destination. This results
in an invalid fdb entry if default destination is not specified.
For ex:
  ip link add vxlan1 type vxlan id 100
creates the following fdb entry
  00:00:00:00:00:00 dev vxlan1 dst 0.0.0.0 self permanent

This patch fixes this issue by creating an fdb entry only if a
valid default destination is specified.
Signed-off-by: NSridhar Samudrala <sri@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -2490,15 +2490,19 @@ static int vxlan_newlink(struct net *net, struct net_device *dev,
 
 	SET_ETHTOOL_OPS(dev, &vxlan_ethtool_ops);
 
-	/* create an fdb entry for default destination */
-	err = vxlan_fdb_create(vxlan, all_zeros_mac,
-			       &vxlan->default_dst.remote_ip,
-			       NUD_REACHABLE|NUD_PERMANENT,
-			       NLM_F_EXCL|NLM_F_CREATE,
-			       vxlan->dst_port, vxlan->default_dst.remote_vni,
-			       vxlan->default_dst.remote_ifindex, NTF_SELF);
-	if (err)
-		return err;
+	/* create an fdb entry for a valid default destination */
+	if (!vxlan_addr_any(&vxlan->default_dst.remote_ip)) {
+		err = vxlan_fdb_create(vxlan, all_zeros_mac,
+				       &vxlan->default_dst.remote_ip,
+				       NUD_REACHABLE|NUD_PERMANENT,
+				       NLM_F_EXCL|NLM_F_CREATE,
+				       vxlan->dst_port,
+				       vxlan->default_dst.remote_vni,
+				       vxlan->default_dst.remote_ifindex,
+				       NTF_SELF);
+		if (err)
+			return err;
+	}
 
 	err = register_netdevice(dev);
 	if (err) {