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>

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)