Use raw sockets on Linux.

        If interface is a bridge we connect a tap to it

def _add_linux_ethernet(self, port_info, bridge_name):
        """
        Use raw sockets on Linux.

        If interface is a bridge we connect a tap to it
        """
        interface = port_info["interface"]
        if gns3server.utils.interfaces.is_interface_bridge(interface):

            network_interfaces = [interface["name"] for interface in self._interfaces()]
            i = 0
            while True:
                tap = "gns3tap{}-{}".format(i, port_info["port_number"])
                if tap not in network_interfaces:
                    break
                i += 1

            yield from self._ubridge_send('bridge add_nio_tap "{name}" "{interface}"'.format(name=bridge_name, interface=tap))
            yield from self._ubridge_send('brctl addif "{interface}" "{tap}"'.format(tap=tap, interface=interface))
        else:
            yield from self._ubridge_send('bridge add_nio_linux_raw {name} "{interface}"'.format(name=bridge_name, interface=interface))