net: add infrastructure to un-offload UDP tunnel port

This adds a new NETDEV_UDP_TUNNEL_DROP_INFO event, similar to
NETDEV_UDP_TUNNEL_PUSH_INFO, to signal to un-offload ports.

This also adds udp_tunnel_drop_rx_port(), which calls
ndo_udp_tunnel_del.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 614642e..3a3cdc1 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2317,6 +2317,7 @@ struct netdev_lag_lower_state_info {
 #define NETDEV_PRECHANGEUPPER	0x001A
 #define NETDEV_CHANGELOWERSTATE	0x001B
 #define NETDEV_UDP_TUNNEL_PUSH_INFO	0x001C
+#define NETDEV_UDP_TUNNEL_DROP_INFO	0x001D
 #define NETDEV_CHANGE_TX_QUEUE_LEN	0x001E
 
 int register_netdevice_notifier(struct notifier_block *nb);