the process when the snooper received IGMP.

def packet_in_handler(self, req_pkt, req_igmp, msg):
        """the process when the snooper received IGMP."""
        dpid = msg.datapath.id
        ofproto = msg.datapath.ofproto
        if ofproto.OFP_VERSION == ofproto_v1_0.OFP_VERSION:
            in_port = msg.in_port
        else:
            in_port = msg.match['in_port']

        log = "SW=%s PORT=%d IGMP received. " % (
            dpid_to_str(dpid), in_port)
        self.logger.debug(str(req_igmp))
        if igmp.IGMP_TYPE_QUERY == req_igmp.msgtype:
            self.logger.info(log + "[QUERY]")
            (req_ipv4, ) = req_pkt.get_protocols(ipv4.ipv4)
            (req_eth, ) = req_pkt.get_protocols(ethernet.ethernet)
            self._do_query(req_igmp, req_ipv4, req_eth, in_port, msg)
        elif (igmp.IGMP_TYPE_REPORT_V1 == req_igmp.msgtype or
              igmp.IGMP_TYPE_REPORT_V2 == req_igmp.msgtype):
            self.logger.info(log + "[REPORT]")
            self._do_report(req_igmp, in_port, msg)
        elif igmp.IGMP_TYPE_LEAVE == req_igmp.msgtype:
            self.logger.info(log + "[LEAVE]")
            self._do_leave(req_igmp, in_port, msg)
        elif igmp.IGMP_TYPE_REPORT_V3 == req_igmp.msgtype:
            self.logger.info(log + "V3 is not supported yet.")
            self._do_flood(in_port, msg)
        else:
            self.logger.info(log + "[unknown type:%d]",
                             req_igmp.msgtype)
            self._do_flood(in_port, msg)