def get_working_if():
 ifaces = get_working_ifaces()
 if (not ifaces):
  return LOOPBACK_NAME
 return ifaces[0][0]

def get_working_if ( ) : ifaces = get_working_ifaces ( ) if ( not ifaces ) : return LOOPBACK_NAME return ifaces [ 0 ] [ 0 ]
returns the first interface than can be used with bpf .