'Convenience method to tunnel data over this circuit
@param (str, int) destination: the destination of the packet
@param str payload: the packet\'s payload'

def tunnel_data(self, destination, payload):

    self._logger.info('Tunnel    data    (len    %d)    to    end    for    circuit    %s    with    ultimate    destination    %s', len(payload), self.circuit_id, destination)
    num_bytes = self.proxy.send_data([Candidate(self.first_hop, False)], self.circuit_id, destination, ('0.0.0.0', 0), payload)
    self.proxy.increase_bytes_sent(self, num_bytes)
    if (num_bytes == 0):
        self._logger.warning('Should    send    %d    bytes    over    circuit    %s,    zero    bytes    were    sent', len(payload), self.circuit_id)
