21CS637-Advanced-Networks

SDN L2 Switch

MAC Learning

# Copyright (C) 2011 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 ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_2
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet


class SimpleSwitch12(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_2.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(SimpleSwitch12, self).__init__(*args, **kwargs)
        self.mac_to_port = {}

    def add_flow(self, datapath, port, dst, actions):
        ofproto = datapath.ofproto

        match = datapath.ofproto_parser.OFPMatch(in_port=port,
                                                 eth_dst=dst)
        inst = [datapath.ofproto_parser.OFPInstructionActions(
                ofproto.OFPIT_APPLY_ACTIONS, actions)]

        mod = datapath.ofproto_parser.OFPFlowMod(
            datapath=datapath, cookie=0, cookie_mask=0, table_id=0,
            command=ofproto.OFPFC_ADD, idle_timeout=0, hard_timeout=0,
            priority=0, buffer_id=ofproto.OFP_NO_BUFFER,
            out_port=ofproto.OFPP_ANY,
            out_group=ofproto.OFPG_ANY,
            flags=0, match=match, instructions=inst)
        datapath.send_msg(mod)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    def _packet_in_handler(self, ev):
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        in_port = msg.match['in_port']

        pkt = packet.Packet(msg.data)
        eth = pkt.get_protocols(ethernet.ethernet)[0]

        dst = eth.dst
        src = eth.src

        dpid = datapath.id
        self.mac_to_port.setdefault(dpid, {})

        self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)

        # learn a mac address to avoid FLOOD next time.
        self.mac_to_port[dpid][src] = 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, in_port, dst, actions)

        data = None
        if msg.buffer_id == ofproto.OFP_NO_BUFFER:
            data = msg.data

        out = datapath.ofproto_parser.OFPPacketOut(
            datapath=datapath, buffer_id=msg.buffer_id, in_port=in_port,
            actions=actions, data=data)
        datapath.send_msg(out)

Demo

Mininet Setup

Starting the Switch

Switch State

Pinging between two nodes (h1 to h2)

Switch Log

Switch State after Ping