'Setup an added tunnel port.
This method is assumed to be used by method fdb_add_tun.
We expect to prepare to call add_fdb_flow. It will be mainly adding
a port to a bridge.
If you need, you may do some preparations for a bridge.
:param br: represent the bridge on which setup_tunnel_port should be
applied.
:param remote_ip: an ip for a port to setup.
:param network_type: a type of a network.
:returns: an ofport value. value 0 means the port is unavailable.'

@abc.abstractmethod
def setup_tunnel_port(self, br, remote_ip, network_type):

    pass
