def _CreateInterfaceMapSysfs(self):
    """Generate a dictionary mapping MAC address to Ethernet interfaces.

    Returns:
      dict, string MAC addresses mapped to the string network interface name.
    """
    interfaces = {}
    for interface in os.listdir('/sys/class/net'):
      try:
        mac_address = open(
            '/sys/class/net/%s/address' % interface).read().strip()
      except (IOError, OSError) as e:
        message = 'Unable to determine MAC address for %s. %s.'
        self.logger.warning(message, interface, str(e))
      else:
        interfaces[mac_address] = interface
    return interfaces