Creates a connection in uBridge.

        :param nio: NIO instance or None if it's a dummy interface (if an interface is missing in ubridge you can't see it via ifconfig in the container)
        :param adapter_number: adapter number

def _add_ubridge_connection(self, nio, adapter_number):
        """
        Creates a connection in uBridge.

        :param nio: NIO instance or None if it's a dummy interface (if an interface is missing in ubridge you can't see it via ifconfig in the container)
        :param adapter_number: adapter number
        """

        try:
            adapter = self._ethernet_adapters[adapter_number]
        except IndexError:
            raise DockerError("Adapter {adapter_number} doesn't exist on Docker container '{name}'".format(name=self.name,
                                                                                                           adapter_number=adapter_number))

        for index in range(4096):
            if "tap-gns3-e{}".format(index) not in psutil.net_if_addrs():
                adapter.host_ifc = "tap-gns3-e{}".format(str(index))
                break
        if adapter.host_ifc is None:
            raise DockerError("Adapter {adapter_number} couldn't allocate interface on Docker container '{name}'. Too many Docker interfaces already exists".format(name=self.name,
                                                                                                                                                                    adapter_number=adapter_number))
        bridge_name = 'bridge{}'.format(adapter_number)
        yield from self._ubridge_send('bridge create {}'.format(bridge_name))
        self._bridges.add(bridge_name)
        yield from self._ubridge_send('bridge add_nio_tap bridge{adapter_number} {hostif}'.format(adapter_number=adapter_number,
                                                                                                  hostif=adapter.host_ifc))
        log.debug("Move container %s adapter %s to namespace %s", self.name, adapter.host_ifc, self._namespace)
        try:
            yield from self._ubridge_send('docker move_to_ns {ifc} {ns} eth{adapter}'.format(ifc=adapter.host_ifc,
                                                                                             ns=self._namespace,
                                                                                             adapter=adapter_number))
        except UbridgeError as e:
            raise UbridgeNamespaceError(e)

        if nio:
            yield from self._connect_nio(adapter_number, nio)