add IGMP snooping application

this application provides the simple example of IGMP snooping.

the module "igmplib" mainly offers 2 functions:
- listening on in the IGMP conversation between multicast routers and hosts
- emulating of the querier function of multicast servers
the former operates a switch as a snooping switch and controls transmission of an unnecessary multicasting packet.
the latter realizes the IGMP conversation in the environment without multicast routers.

the module "simple_switch_igmp" is a variation of "simple_switch".
the switch receives the "EventPacketIn" event instead of the "EventOFPPacketIn" event from the module "igmplib" in order to except IGMP.

Signed-off-by: Yuichi Ito <ito.yuichi0@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

2 files changed, 914 insertions, 0 deletions

diff --git a/ryu/app/simple_switch_igmp.py b/ryu/app/simple_switch_igmp.py
new file mode 100644
index 00000000..b1b014f0
--- /dev/null
+++ b/ryu/app/simple_switch_igmp.py
@@ -0,0 +1,104 @@
+# Copyright (C) 2013 Nippon Telegraph and Telephone Corporation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import struct
+
+from ryu.base import app_manager
+from ryu.controller.handler import MAIN_DISPATCHER
+from ryu.controller.handler import set_ev_cls
+from ryu.ofproto import ofproto_v1_0
+from ryu.lib import addrconv
+from ryu.lib import igmplib
+from ryu.lib.dpid import str_to_dpid
+
+
+class SimpleSwitchIgmp(app_manager.RyuApp):
+    OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]
+    _CONTEXTS = {'igmplib': igmplib.IgmpLib}
+
+    def __init__(self, *args, **kwargs):
+        super(SimpleSwitchIgmp, self).__init__(*args, **kwargs)
+        self.mac_to_port = {}
+        self._snoop = kwargs['igmplib']
+        # if you want a switch to operate as a querier,
+        # set up as follows:
+        self._snoop.set_querier_mode(
+            dpid=str_to_dpid('0000000000000001'), server_port=2)
+        # dpid         the datapath id that will operate as a querier.
+        # server_port  a port number which connect to the multicast
+        #              server.
+        #
+        # NOTE: you can set up only the one querier.
+        # when you called this method several times,
+        # only the last one becomes effective.
+
+    def add_flow(self, datapath, in_port, dst, actions):
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        match = parser.OFPMatch(in_port=in_port,
+                                dl_dst=addrconv.mac.text_to_bin(dst))
+        mod = parser.OFPFlowMod(
+            datapath=datapath, match=match, cookie=0,
+            command=ofproto.OFPFC_ADD, actions=actions)
+        datapath.send_msg(mod)
+
+    @set_ev_cls(igmplib.EventPacketIn, MAIN_DISPATCHER)
+    def _packet_in_handler(self, ev):
+        msg = ev.msg
+        datapath = msg.datapath
+        ofproto = datapath.ofproto
+
+        (dst_, src_, _eth_type) = struct.unpack_from(
+            '!6s6sH', buffer(msg.data), 0)
+        src = addrconv.mac.bin_to_text(src_)
+        dst = addrconv.mac.bin_to_text(dst_)
+
+        dpid = datapath.id
+        self.mac_to_port.setdefault(dpid, {})
+
+        self.logger.info("packet in %s %s %s %s",
+                         dpid, src, dst, msg.in_port)
+
+        # learn a mac address to avoid FLOOD next time.
+        self.mac_to_port[dpid][src] = msg.in_port
+
+        if dst in self.mac_to_port[dpid]:
+            out_port = self.mac_to_port[dpid][dst]
+        else:
+            out_port = ofproto.OFPP_FLOOD
+
+        actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]
+
+        # install a flow to avoid packet_in next time
+        if out_port != ofproto.OFPP_FLOOD:
+            self.add_flow(datapath, msg.in_port, dst, actions)
+
+        out = datapath.ofproto_parser.OFPPacketOut(
+            datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
+            actions=actions)
+        datapath.send_msg(out)
+
+    @set_ev_cls(igmplib.EventMulticastGroupStateChanged,
+                MAIN_DISPATCHER)
+    def _status_changed(self, ev):
+        msg = {
+            igmplib.MG_GROUP_ADDED: 'Multicast Group Added',
+            igmplib.MG_MEMBER_CHANGED: 'Multicast Group Member Changed',
+            igmplib.MG_GROUP_REMOVED: 'Multicast Group Removed',
+        }
+        self.logger.info("%s: [%s] querier:[%s] hosts:%s",
+                         msg.get(ev.reason), ev.address, ev.src,
+                         ev.dsts)
diff --git a/ryu/lib/igmplib.py b/ryu/lib/igmplib.py
new file mode 100644
index 00000000..1171da3b
--- /dev/null
+++ b/ryu/lib/igmplib.py
@@ -0,0 +1,810 @@
+# Copyright (C) 2013 Nippon Telegraph and Telephone Corporation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+import struct
+
+from ryu.base import app_manager
+from ryu.controller import event
+from ryu.controller import ofp_event
+from ryu.controller.handler import DEAD_DISPATCHER
+from ryu.controller.handler import MAIN_DISPATCHER
+from ryu.controller.handler import set_ev_cls
+from ryu.ofproto import ether
+from ryu.ofproto import inet
+from ryu.ofproto import ofproto_v1_0
+from ryu.ofproto import ofproto_v1_2
+from ryu.ofproto import ofproto_v1_3
+from ryu.lib import addrconv
+from ryu.lib import hub
+from ryu.lib.dpid import dpid_to_str
+from ryu.lib.packet import packet
+from ryu.lib.packet import ethernet
+from ryu.lib.packet import ipv4
+from ryu.lib.packet import igmp
+
+
+class EventPacketIn(event.EventBase):
+    """a PacketIn event class using except IGMP."""
+    def __init__(self, msg):
+        """initialization."""
+        super(EventPacketIn, self).__init__()
+        self.msg = msg
+
+
+MG_GROUP_ADDED = 1
+MG_MEMBER_CHANGED = 2
+MG_GROUP_REMOVED = 3
+
+
+class EventMulticastGroupStateChanged(event.EventBase):
+    """a event class that notifies the changes of the statuses of the
+    multicast groups."""
+
+    def __init__(self, reason, address, src, dsts):
+        """
+        ========= =====================================================
+        Attribute Description
+        ========= =====================================================
+        reason    why the event occurs. use one of MG_*.
+        address   a multicast group address.
+        src       a port number in which a querier exists.
+        dsts      a list of port numbers in which the members exist.
+        ========= =====================================================
+        """
+        super(EventMulticastGroupStateChanged, self).__init__()
+        self.reason = reason
+        self.address = address
+        self.src = src
+        self.dsts = dsts
+
+
+class IgmpLib(app_manager.RyuApp):
+    """IGMP snooping library."""
+
+    #-------------------------------------------------------------------
+    # PUBLIC METHODS
+    #-------------------------------------------------------------------
+    def __init__(self):
+        """initialization."""
+        super(IgmpLib, self).__init__()
+        self.name = 'igmplib'
+        self._querier = IgmpQuerier()
+        self._snooper = IgmpSnooper(self.send_event_to_observers)
+
+    def set_querier_mode(self, dpid, server_port):
+        """set a datapath id and server port number to the instance
+        of IgmpQuerier.
+
+        ============ ==================================================
+        Attribute    Description
+        ============ ==================================================
+        dpid         the datapath id that will operate as a querier.
+        server_port  the port number linked to the multicasting server.
+        ============ ==================================================
+        """
+        self._querier.set_querier_mode(dpid, server_port)
+
+    #-------------------------------------------------------------------
+    # PUBLIC METHODS ( EVENT HANDLERS )
+    #-------------------------------------------------------------------
+    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
+    def packet_in_handler(self, evt):
+        """PacketIn event handler. when the received packet was IGMP,
+        proceed it. otherwise, send a event."""
+        msg = evt.msg
+        dpid = msg.datapath.id
+
+        req_pkt = packet.Packet(msg.data)
+        req_igmp = req_pkt.get_protocol(igmp.igmp)
+        if req_igmp:
+            if self._querier.dpid == dpid:
+                self._querier.packet_in_handler(req_igmp, msg)
+            else:
+                self._snooper.packet_in_handler(req_pkt, req_igmp, msg)
+        else:
+            self.send_event_to_observers(EventPacketIn(msg))
+
+    @set_ev_cls(ofp_event.EventOFPStateChange,
+                [MAIN_DISPATCHER, DEAD_DISPATCHER])
+    def state_change_handler(self, evt):
+        """StateChange event handler."""
+        datapath = evt.datapath
+        assert datapath is not None
+        if datapath.id == self._querier.dpid:
+            if evt.state == MAIN_DISPATCHER:
+                self._querier.start_loop(datapath)
+            elif evt.state == DEAD_DISPATCHER:
+                self._querier.stop_loop()
+
+
+class IgmpBase(object):
+    """IGMP abstract class library."""
+
+    #-------------------------------------------------------------------
+    # PUBLIC METHODS
+    #-------------------------------------------------------------------
+    def __init__(self):
+        self._set_flow_func = {
+            ofproto_v1_0.OFP_VERSION: self._set_flow_entry_v1_0,
+            ofproto_v1_2.OFP_VERSION: self._set_flow_entry_v1_2,
+            ofproto_v1_3.OFP_VERSION: self._set_flow_entry_v1_2,
+        }
+        self._del_flow_func = {
+            ofproto_v1_0.OFP_VERSION: self._del_flow_entry_v1_0,
+            ofproto_v1_2.OFP_VERSION: self._del_flow_entry_v1_2,
+            ofproto_v1_3.OFP_VERSION: self._del_flow_entry_v1_2,
+        }
+
+    #-------------------------------------------------------------------
+    # PROTECTED METHODS ( RELATED TO OPEN FLOW PROTOCOL )
+    #-------------------------------------------------------------------
+    def _set_flow_entry_v1_0(self, datapath, actions, in_port, dst,
+                             src=None):
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        match = parser.OFPMatch(
+            dl_type=ether.ETH_TYPE_IP, in_port=in_port,
+            nw_src=self._ipv4_text_to_int(src),
+            nw_dst=self._ipv4_text_to_int(dst))
+        mod = parser.OFPFlowMod(
+            datapath=datapath, match=match, cookie=0,
+            command=ofproto.OFPFC_ADD, actions=actions)
+        datapath.send_msg(mod)
+
+    def _set_flow_entry_v1_2(self, datapath, actions, in_port, dst,
+                             src=None):
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        match = parser.OFPMatch(
+            eth_type=ether.ETH_TYPE_IP, in_port=in_port, ipv4_dst=dst)
+        if src is not None:
+            match.append_field(ofproto.OXM_OF_IPV4_SRC, src)
+        inst = [parser.OFPInstructionActions(
+            ofproto.OFPIT_APPLY_ACTIONS, actions)]
+        mod = parser.OFPFlowMod(
+            datapath=datapath, command=ofproto.OFPFC_ADD,
+            priority=65535, match=match, instructions=inst)
+        datapath.send_msg(mod)
+
+    def _set_flow_entry(self, datapath, actions, in_port, dst, src=None):
+        """set a flow entry."""
+        set_flow = self._set_flow_func.get(datapath.ofproto.OFP_VERSION)
+        assert set_flow
+        set_flow(datapath, actions, in_port, dst, src)
+
+    def _del_flow_entry_v1_0(self, datapath, in_port, dst, src=None):
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        match = parser.OFPMatch(
+            dl_type=ether.ETH_TYPE_IP, in_port=in_port,
+            nw_src=self._ipv4_text_to_int(src),
+            nw_dst=self._ipv4_text_to_int(dst))
+        mod = parser.OFPFlowMod(
+            datapath=datapath, match=match, cookie=0,
+            command=ofproto.OFPFC_DELETE)
+        datapath.send_msg(mod)
+
+    def _del_flow_entry_v1_2(self, datapath, in_port, dst, src=None):
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        match = parser.OFPMatch(
+            eth_type=ether.ETH_TYPE_IP, in_port=in_port, ipv4_dst=dst)
+        if src is not None:
+            match.append_field(ofproto.OXM_OF_IPV4_SRC, src)
+        mod = parser.OFPFlowMod(
+            datapath=datapath, command=ofproto.OFPFC_DELETE,
+            out_port=ofproto.OFPP_ANY, out_group=ofproto.OFPG_ANY,
+            match=match)
+        datapath.send_msg(mod)
+
+    def _del_flow_entry(self, datapath, in_port, dst, src=None):
+        """remove a flow entry."""
+        del_flow = self._del_flow_func.get(datapath.ofproto.OFP_VERSION)
+        assert del_flow
+        del_flow(datapath, in_port, dst, src)
+
+    def _do_packet_out(self, datapath, data, in_port, actions):
+        """send a packet."""
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        out = parser.OFPPacketOut(
+            datapath=datapath, buffer_id=ofproto.OFP_NO_BUFFER,
+            data=data, in_port=in_port, actions=actions)
+        datapath.send_msg(out)
+
+    #-------------------------------------------------------------------
+    # PROTECTED METHODS ( OTHERS )
+    #-------------------------------------------------------------------
+    def _ipv4_text_to_int(self, ip_text):
+        """convert ip v4 string to integer."""
+        if ip_text is None:
+            return None
+        assert isinstance(ip_text, str)
+        return struct.unpack('!I', addrconv.ipv4.text_to_bin(ip_text))[0]
+
+
+class IgmpQuerier(IgmpBase):
+    """IGMP querier emulation class library.
+
+    this querier is a simplified implementation, and is not based on RFC,
+    for example as following points:
+    - ignore some constant values
+    - does not send a specific QUERY in response to LEAVE
+    - and so on
+    """
+
+    #-------------------------------------------------------------------
+    # PUBLIC METHODS
+    #-------------------------------------------------------------------
+    def __init__(self):
+        """initialization."""
+        super(IgmpQuerier, self).__init__()
+        self.name = "IgmpQuerier"
+        self.logger = logging.getLogger(self.name)
+        self.dpid = None
+        self.server_port = None
+
+        self._datapath = None
+        self._querier_thread = None
+
+        # the structure of self._macst
+        #
+        # +-------+------------------+
+        # | group | port: True/False |
+        # |       +------------------+
+        # |       |...               |
+        # +-------+------------------+
+        # | ...                      |
+        # +--------------------------+
+        #
+        # group       multicast address.
+        # port        a port number which connect to the group member.
+        #             the value indicates that whether a flow entry
+        #             was registered.
+        self._mcast = {}
+
+        self._set_logger()
+
+    def set_querier_mode(self, dpid, server_port):
+        """set the datapath to work as a querier. note that you can set
+        up only the one querier. when you called this method several
+        times, only the last one becomes effective."""
+        self.dpid = dpid
+        self.server_port = server_port
+        if self._querier_thread:
+            hub.kill(self._querier_thread)
+            self._querier_thread = None
+
+    def packet_in_handler(self, req_igmp, msg):
+        """the process when the querier received IGMP."""
+        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']
+        if (igmp.IGMP_TYPE_REPORT_V1 == req_igmp.msgtype or
+                igmp.IGMP_TYPE_REPORT_V2 == req_igmp.msgtype):
+            self._do_report(req_igmp, in_port, msg)
+        elif igmp.IGMP_TYPE_LEAVE == req_igmp.msgtype:
+            self._do_leave(req_igmp, in_port, msg)
+
+    def start_loop(self, datapath):
+        """start QUERY thread."""
+        self._datapath = datapath
+        self._querier_thread = hub.spawn(self._send_query)
+        self.logger.info("started a querier.")
+
+    def stop_loop(self):
+        """stop QUERY thread."""
+        hub.kill(self._querier_thread)
+        self._querier_thread = None
+        self._datapath = None
+        self.logger.info("stopped a querier.")
+
+    #-------------------------------------------------------------------
+    # PRIVATE METHODS ( RELATED TO IGMP )
+    #-------------------------------------------------------------------
+    def _send_query(self):
+        """ send a QUERY message periodically."""
+        timeout = 60
+        ofproto = self._datapath.ofproto
+        parser = self._datapath.ofproto_parser
+        if ofproto_v1_0.OFP_VERSION == ofproto.OFP_VERSION:
+            send_port = ofproto.OFPP_NONE
+        else:
+            send_port = ofproto.OFPP_ANY
+
+        # create a general query.
+        res_igmp = igmp.igmp(
+            msgtype=igmp.IGMP_TYPE_QUERY,
+            maxresp=igmp.QUERY_RESPONSE_INTERVAL * 10,
+            csum=0,
+            address='0.0.0.0')
+        res_ipv4 = ipv4.ipv4(
+            total_length=len(ipv4.ipv4()) + len(res_igmp),
+            proto=inet.IPPROTO_IGMP, ttl=1,
+            src='0.0.0.0',
+            dst=igmp.MULTICAST_IP_ALL_HOST)
+        res_ether = ethernet.ethernet(
+            dst=igmp.MULTICAST_MAC_ALL_HOST,
+            src=self._datapath.ports[ofproto.OFPP_LOCAL].hw_addr,
+            ethertype=ether.ETH_TYPE_IP)
+        res_pkt = packet.Packet()
+        res_pkt.add_protocol(res_ether)
+        res_pkt.add_protocol(res_ipv4)
+        res_pkt.add_protocol(res_igmp)
+        res_pkt.serialize()
+
+        actions = [parser.OFPActionOutput(ofproto.OFPP_FLOOD)]
+
+        while True:
+            # reset reply status.
+            for status in self._mcast.values():
+                for port in status.keys():
+                    status[port] = False
+
+            # send a general query to the host that sent this message.
+            self._do_packet_out(
+                self._datapath, res_pkt.data, send_port, actions)
+            hub.sleep(igmp.QUERY_RESPONSE_INTERVAL)
+
+            # QUERY timeout expired.
+            del_groups = []
+            for group, status in self._mcast.items():
+                del_ports = []
+                actions = []
+                for port in status.keys():
+                    if not status[port]:
+                        del_ports.append(port)
+                    else:
+                        actions.append(parser.OFPActionOutput(port))
+                if len(actions) and len(del_ports):
+                    self._set_flow_entry(
+                        self._datapath, actions, self.server_port, group)
+                if not len(actions):
+                    self._del_flow_entry(
+                        self._datapath, self.server_port, group)
+                    del_groups.append(group)
+                if len(del_ports):
+                    for port in del_ports:
+                        self._del_flow_entry(self._datapath, port, group)
+                for port in del_ports:
+                    del status[port]
+            for group in del_groups:
+                del self._mcast[group]
+
+            rest_time = timeout - igmp.QUERY_RESPONSE_INTERVAL
+            hub.sleep(rest_time)
+
+    def _do_report(self, report, in_port, msg):
+        """the process when the querier received a REPORT message."""
+        datapath = msg.datapath
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        if ofproto.OFP_VERSION == ofproto_v1_0.OFP_VERSION:
+            size = 65535
+        else:
+            size = ofproto.OFPCML_MAX
+
+        update = False
+        self._mcast.setdefault(report.address, {})
+        if not in_port in self._mcast[report.address]:
+            update = True
+        self._mcast[report.address][in_port] = True
+
+        if update:
+            actions = []
+            for port in self._mcast[report.address]:
+                actions.append(parser.OFPActionOutput(port))
+            self._set_flow_entry(
+                datapath, actions, self.server_port, report.address)
+            self._set_flow_entry(
+                datapath,
+                [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, size)],
+                in_port, report.address)
+
+    def _do_leave(self, leave, in_port, msg):
+        """the process when the querier received a LEAVE message."""
+        datapath = msg.datapath
+        parser = datapath.ofproto_parser
+
+        self._mcast.setdefault(leave.address, {})
+        if in_port in self._mcast[leave.address]:
+            self._del_flow_entry(
+                datapath, in_port, leave.address)
+            del self._mcast[leave.address][in_port]
+            actions = []
+            for port in self._mcast[leave.address]:
+                actions.append(parser.OFPActionOutput(port))
+            if len(actions):
+                self._set_flow_entry(
+                    datapath, actions, self.server_port, leave.address)
+            else:
+                self._del_flow_entry(
+                    datapath, self.server_port, leave.address)
+
+    #-------------------------------------------------------------------
+    # PRIVATE METHODS ( OTHERS )
+    #-------------------------------------------------------------------
+    def _set_logger(self):
+        """change log format."""
+        self.logger.propagate = False
+        hdl = logging.StreamHandler()
+        fmt_str = '[querier][%(levelname)s] %(message)s'
+        hdl.setFormatter(logging.Formatter(fmt_str))
+        self.logger.addHandler(hdl)
+
+
+class IgmpSnooper(IgmpBase):
+    """IGMP snooping class library."""
+
+    #-------------------------------------------------------------------
+    # PUBLIC METHODS
+    #-------------------------------------------------------------------
+    def __init__(self, send_event):
+        """initialization."""
+        super(IgmpSnooper, self).__init__()
+        self.name = "IgmpSnooper"
+        self.logger = logging.getLogger(self.name)
+        self._send_event = send_event
+
+        # the structure of self._to_querier
+        #
+        # +------+--------------+
+        # | dpid | 'port': port |
+        # |      +--------------+
+        # |      | 'ip': ip     |
+        # |      +--------------+
+        # |      | 'mac': mac   |
+        # +------+--------------+
+        # | ...                 |
+        # +---------------------+
+        #
+        # dpid        datapath id.
+        # port        a port number which connect to the querier.
+        # ip          IP address of the querier.
+        # mac         MAC address of the querier.
+        self._to_querier = {}
+
+        # the structure of self._to_hosts
+        #
+        # +------+-------+---------------------------------+
+        # | dpid | group | 'replied': True/False           |
+        # |      |       +---------------------------------+
+        # |      |       | 'leave': leave                  |
+        # |      |       +-----------+--------+------------+
+        # |      |       | 'ports'   | portno | 'out': out |
+        # |      |       |           |        +------------+
+        # |      |       |           |        | 'in': in   |
+        # |      |       |           +--------+------------+
+        # |      |       |           | ...                 |
+        # |      +-------+-----------+---------------------+
+        # |      | ...                                     |
+        # +------+-----------------------------------------+
+        # | ...                                            |
+        # +------------------------------------------------+
+        #
+        # dpid        datapath id.
+        # group       multicast address.
+        # replied     the value indicates whether a REPORT message was
+        #             replied.
+        # leave       a LEAVE message.
+        # portno      a port number which has joined to the multicast
+        #             group.
+        # out         the value indicates whether a flow entry for the
+        #             packet outputted to the port was registered.
+        # in          the value indicates whether a flow entry for the
+        #             packet inputted from the port was registered.
+        self._to_hosts = {}
+
+        self._set_logger()
+
+    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)
+
+    #-------------------------------------------------------------------
+    # PRIVATE METHODS ( RELATED TO IGMP )
+    #-------------------------------------------------------------------
+    def _do_query(self, query, iph, eth, in_port, msg):
+        """the process when the snooper received a QUERY message."""
+        datapath = msg.datapath
+        dpid = datapath.id
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        # learn the querier.
+        self._to_querier[dpid] = {
+            'port': in_port,
+            'ip': iph.src,
+            'mac': eth.src
+        }
+
+        # set the timeout time.
+        timeout = igmp.QUERY_RESPONSE_INTERVAL
+        if query.maxresp:
+            timeout = query.maxresp / 10
+
+        self._to_hosts.setdefault(dpid, {})
+        if '0.0.0.0' == query.address:
+            # general query. reset all reply status.
+            for group in self._to_hosts[dpid].values():
+                group['replied'] = False
+                group['leave'] = None
+        else:
+            # specific query. reset the reply status of the specific
+            # group.
+            group = self._to_hosts[dpid].get(query.address)
+            if group:
+                group['replied'] = False
+                group['leave'] = None
+
+        actions = [parser.OFPActionOutput(ofproto.OFPP_FLOOD)]
+        self._do_packet_out(
+            datapath, msg.data, in_port, actions)
+
+        # wait for REPORT messages.
+        hub.spawn(self._do_timeout_for_query, timeout, datapath)
+
+    def _do_report(self, report, in_port, msg):
+        """the process when the snooper received a REPORT message."""
+        datapath = msg.datapath
+        dpid = datapath.id
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        if ofproto.OFP_VERSION == ofproto_v1_0.OFP_VERSION:
+            size = 65535
+        else:
+            size = ofproto.OFPCML_MAX
+
+        # check whether the querier port has been specified.
+        outport = None
+        value = self._to_querier.get(dpid)
+        if value:
+            outport = value['port']
+
+        # send a event when the multicast group address is new.
+        self._to_hosts.setdefault(dpid, {})
+        if not self._to_hosts[dpid].get(report.address):
+            self._send_event(
+                EventMulticastGroupStateChanged(
+                    MG_GROUP_ADDED, report.address, outport, []))
+            self._to_hosts[dpid].setdefault(
+                report.address,
+                {'replied': False, 'leave': None, 'ports': {}})
+
+        # set a flow entry from a host to the controller when
+        # a host sent a REPORT message.
+        if not self._to_hosts[dpid][report.address]['ports'].get(
+                in_port):
+            self._to_hosts[dpid][report.address]['ports'][
+                in_port] = {'out': False, 'in': False}
+            self._set_flow_entry(
+                datapath,
+                [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, size)],
+                in_port, report.address)
+
+        if not self._to_hosts[dpid][report.address]['ports'][
+                in_port]['out']:
+            self._to_hosts[dpid][report.address]['ports'][
+                in_port]['out'] = True
+
+        if not outport:
+            self.logger.info("no querier exists.")
+            return
+
+        # set a flow entry from a multicast server to hosts.
+        if not self._to_hosts[dpid][report.address]['ports'][
+                in_port]['in']:
+            actions = []
+            ports = []
+            for port in self._to_hosts[dpid][report.address]['ports']:
+                actions.append(parser.OFPActionOutput(port))
+                ports.append(port)
+            self._send_event(
+                EventMulticastGroupStateChanged(
+                    MG_MEMBER_CHANGED, report.address, outport, ports))
+            self._set_flow_entry(
+                datapath, actions, outport, report.address)
+            self._to_hosts[dpid][report.address]['ports'][
+                in_port]['in'] = True
+
+        # send a REPORT message to the querier if this message arrived
+        # first after a QUERY message was sent.
+        if not self._to_hosts[dpid][report.address]['replied']:
+            actions = [parser.OFPActionOutput(outport, size)]
+            self._do_packet_out(datapath, msg.data, in_port, actions)
+            self._to_hosts[dpid][report.address]['replied'] = True
+
+    def _do_leave(self, leave, in_port, msg):
+        """the process when the snooper received a LEAVE message."""
+        datapath = msg.datapath
+        dpid = datapath.id
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+
+        # check whether the querier port has been specified.
+        if not self._to_querier.get(dpid):
+            self.logger.info("no querier exists.")
+            return
+
+        # save this LEAVE message and reset the condition of the port
+        # that received this message.
+        self._to_hosts.setdefault(dpid, {})
+        self._to_hosts[dpid].setdefault(
+            leave.address,
+            {'replied': False, 'leave': None, 'ports': {}})
+        self._to_hosts[dpid][leave.address]['leave'] = msg
+        self._to_hosts[dpid][leave.address]['ports'][in_port] = {
+            'out': False, 'in': False}
+
+        # create a specific query.
+        timeout = igmp.LAST_MEMBER_QUERY_INTERVAL
+        res_igmp = igmp.igmp(
+            msgtype=igmp.IGMP_TYPE_QUERY,
+            maxresp=timeout * 10,
+            csum=0,
+            address=leave.address)
+        res_ipv4 = ipv4.ipv4(
+            total_length=len(ipv4.ipv4()) + len(res_igmp),
+            proto=inet.IPPROTO_IGMP, ttl=1,
+            src=self._to_querier[dpid]['ip'],
+            dst=igmp.MULTICAST_IP_ALL_HOST)
+        res_ether = ethernet.ethernet(
+            dst=igmp.MULTICAST_MAC_ALL_HOST,
+            src=self._to_querier[dpid]['mac'],
+            ethertype=ether.ETH_TYPE_IP)
+        res_pkt = packet.Packet()
+        res_pkt.add_protocol(res_ether)
+        res_pkt.add_protocol(res_ipv4)
+        res_pkt.add_protocol(res_igmp)
+        res_pkt.serialize()
+
+        # send a specific query to the host that sent this message.
+        actions = [parser.OFPActionOutput(ofproto.OFPP_IN_PORT)]
+        self._do_packet_out(datapath, res_pkt.data, in_port, actions)
+
+        # wait for REPORT messages.
+        hub.spawn(self._do_timeout_for_leave, timeout, datapath,
+                  leave.address, in_port)
+
+    def _do_flood(self, in_port, msg):
+        """the process when the snooper received a message of the
+        outside for processing. """
+        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)
+
+    def _do_timeout_for_query(self, timeout, datapath):
+        """the process when the QUERY from the querier timeout expired."""
+        dpid = datapath.id
+
+        hub.sleep(timeout)
+        outport = self._to_querier[dpid]['port']
+
+        remove_dsts = []
+        for dst in self._to_hosts[dpid]:
+            if not self._to_hosts[dpid][dst]['replied']:
+                # if no REPORT message sent from any members of
+                # the group, remove flow entries about the group and
+                # send a LEAVE message if exists.
+                self._remove_multicast_group(datapath, outport, dst)
+                remove_dsts.append(dst)
+
+        for dst in remove_dsts:
+            del self._to_hosts[dpid][dst]
+
+    def _do_timeout_for_leave(self, timeout, datapath, dst, in_port):
+        """the process when the QUERY from the switch timeout expired."""
+        parser = datapath.ofproto_parser
+        dpid = datapath.id
+
+        hub.sleep(timeout)
+        outport = self._to_querier[dpid]['port']
+
+        if self._to_hosts[dpid][dst]['ports'][in_port]['out']:
+            return
+
+        del self._to_hosts[dpid][dst]['ports'][in_port]
+        self._del_flow_entry(datapath, in_port, dst)
+        actions = []
+        ports = []
+        for port in self._to_hosts[dpid][dst]['ports']:
+            actions.append(parser.OFPActionOutput(port))
+            ports.append(port)
+
+        if len(actions):
+            self._send_event(
+                EventMulticastGroupStateChanged(
+                    MG_MEMBER_CHANGED, dst, outport, ports))
+            self._set_flow_entry(
+                datapath, actions, outport, dst)
+            self._to_hosts[dpid][dst]['leave'] = None
+        else:
+            self._remove_multicast_group(datapath, outport, dst)
+            del self._to_hosts[dpid][dst]
+
+    def _remove_multicast_group(self, datapath, outport, dst):
+        """remove flow entries about the group and send a LEAVE message
+        if exists."""
+        ofproto = datapath.ofproto
+        parser = datapath.ofproto_parser
+        dpid = datapath.id
+
+        self._send_event(
+            EventMulticastGroupStateChanged(
+                MG_GROUP_REMOVED, dst, outport, []))
+        self._del_flow_entry(datapath, outport, dst)
+        for port in self._to_hosts[dpid][dst]['ports']:
+            self._del_flow_entry(datapath, port, dst)
+        leave = self._to_hosts[dpid][dst]['leave']
+        if leave:
+            if ofproto.OFP_VERSION == ofproto_v1_0.OFP_VERSION:
+                in_port = leave.in_port
+            else:
+                in_port = leave.match['in_port']
+            actions = [parser.OFPActionOutput(outport)]
+            self._do_packet_out(
+                datapath, leave.data, in_port, actions)
+
+    #-------------------------------------------------------------------
+    # PRIVATE METHODS ( OTHERS )
+    #-------------------------------------------------------------------
+    def _set_logger(self):
+        """change log format."""
+        self.logger.propagate = False
+        hdl = logging.StreamHandler()
+        fmt_str = '[snoop][%(levelname)s] %(message)s'
+        hdl.setFormatter(logging.Formatter(fmt_str))
+        self.logger.addHandler(hdl)