vxlan: leave multicast group when vxlan device down

vxlan_group_used only allows device to leave multicast group
when the remote_ip of this vxlan device is difference from
other vxlan devices' remote_ip. this will cause device not
leave multicast group untile the vn_sock of this vxlan deivce
being released.

The check in vxlan_group_used is not quite precise. since even
the remote_ip is same, but these vxlan devices may use different
lower devices, and they may use different vn_socks.

Only when some vxlan devices use the same vn_sock,same lower
device and same remote_ip, the mc_list of the vn_sock should
not be changed.
Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -916,16 +916,31 @@ static bool vxlan_snoop(struct net_device *dev,
 }
 
 /* See if multicast group is already in use by other ID */
-static bool vxlan_group_used(struct vxlan_net *vn, union vxlan_addr *remote_ip)
+static bool vxlan_group_used(struct vxlan_net *vn, struct vxlan_dev *dev)
 {
 	struct vxlan_dev *vxlan;
 
+	/* The vxlan_sock is only used by dev, leaving group has
+	 * no effect on other vxlan devices.
+	 */
+	if (atomic_read(&dev->vn_sock->refcnt) == 1)
+		return false;
+
 	list_for_each_entry(vxlan, &vn->vxlan_list, next) {
-		if (!netif_running(vxlan->dev))
+		if (!netif_running(vxlan->dev) || vxlan == dev)
+			continue;
+
+		if (vxlan->vn_sock != dev->vn_sock)
+			continue;
+
+		if (!vxlan_addr_equal(&vxlan->default_dst.remote_ip,
+				      &dev->default_dst.remote_ip))
+			continue;
+
+		if (vxlan->default_dst.remote_ifindex !=
+		    dev->default_dst.remote_ifindex)
 			continue;
 
-		if (vxlan_addr_equal(&vxlan->default_dst.remote_ip,
-				     remote_ip))
 		return true;
 	}
 
@@ -1981,7 +1996,7 @@ static int vxlan_stop(struct net_device *dev)
 	struct vxlan_sock *vs = vxlan->vn_sock;
 
 	if (vs && vxlan_addr_multicast(&vxlan->default_dst.remote_ip) &&
-	    ! vxlan_group_used(vn, &vxlan->default_dst.remote_ip)) {
+	    !vxlan_group_used(vn, vxlan)) {
 		vxlan_sock_hold(vs);
 		dev_hold(dev);
 		queue_work(vxlan_wq, &vxlan->igmp_leave);