packet-in process when the received packet is LACP.

def _do_lacp(self, req_lacp, src, msg):
        """packet-in process when the received packet is LACP."""
        datapath = msg.datapath
        dpid = datapath.id
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser
        if ofproto.OFP_VERSION == ofproto_v1_0.OFP_VERSION:
            port = msg.in_port
        else:
            port = msg.match['in_port']

        self.logger.info("SW=%s PORT=%d LACP received.",
                         dpid_to_str(dpid), port)
        self.logger.debug(str(req_lacp))

        # when LACP arrived at disabled port, update the status of
        # the slave i/f to enabled, and send a event.
        if not self._get_slave_enabled(dpid, port):
            self.logger.info(
                "SW=%s PORT=%d the slave i/f has just been up.",
                dpid_to_str(dpid), port)
            self._set_slave_enabled(dpid, port, True)
            self.send_event_to_observers(
                EventSlaveStateChanged(datapath, port, True))

        # set the idle_timeout time using the actor state of the
        # received packet.
        if req_lacp.LACP_STATE_SHORT_TIMEOUT == \
           req_lacp.actor_state_timeout:
            idle_timeout = req_lacp.SHORT_TIMEOUT_TIME
        else:
            idle_timeout = req_lacp.LONG_TIMEOUT_TIME

        # when the timeout time has changed, update the timeout time of
        # the slave i/f and re-enter a flow entry for the packet from
        # the slave i/f with idle_timeout.
        if idle_timeout != self._get_slave_timeout(dpid, port):
            self.logger.info(
                "SW=%s PORT=%d the timeout time has changed.",
                dpid_to_str(dpid), port)
            self._set_slave_timeout(dpid, port, idle_timeout)
            func = self._add_flow.get(ofproto.OFP_VERSION)
            assert func
            func(src, port, idle_timeout, datapath)

        # create a response packet.
        res_pkt = self._create_response(datapath, port, req_lacp)

        # packet-out the response packet.
        out_port = ofproto.OFPP_IN_PORT
        actions = [parser.OFPActionOutput(out_port)]
        out = datapath.ofproto_parser.OFPPacketOut(
            datapath=datapath, buffer_id=ofproto.OFP_NO_BUFFER,
            data=res_pkt.data, in_port=port, actions=actions)
        datapath.send_msg(out)