'Create the L{_IInputOutputSystem} provider under test and open a tunnel
using it.'

def setUp(self):

    self.system = self.createSystem()
    self.fileno = self.system.open('/dev/net/tun', (os.O_RDWR | os.O_NONBLOCK))
    self.addCleanup(self.system.close, self.fileno)
    mode = self.helper.TUNNEL_TYPE
    config = struct.pack(('%dsH' % (_IFNAMSIZ,)), self._TUNNEL_DEVICE, mode.value)
    self.system.ioctl(self.fileno, _TUNSETIFF, config)
