+int netdev_build_header(const struct netdev *, struct ovs_action_push_tnl *data,
+ const struct flow *tnl_flow);
+int netdev_push_header(const struct netdev *netdev,
+ struct dp_packet **buffers, int cnt,
+ const struct ovs_action_push_tnl *data);
+int netdev_pop_header(struct netdev *netdev, struct dp_packet **buffers,
+ int cnt);
+