code: def _do_flood(self, in_port, msg):
          
          datapath = msg.datapath
          ofproto = datapath.ofproto
          parser = datapath.ofproto_parser
  
          actions = [parser.OFPActionOutput(ofproto.OFPP_FLOOD)]
          self._do_packet_out(datapath, msg.data, in_port, actions)
docs: the process when the snooper received a message of the
          outside for processing.