SDN5

1.浏览RYU官网学习RYU控制器的安装和RYU开发入门教程，提交对于教程代码的理解：

• 描述官方教程实现了一个什么样的交换机功能？
  实现了一个将接收到的数据包发送到所有端口的交换机功能
• 控制器设定交换机支持什么版本的OpenFlow？
  控制器设定交换机支持OpenFlow 1.0
• 控制器设定了交换机如何处理数据包？
  接收包并广播包

   @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    #当Ryu收到OpenFlow交换机送来的packet_in消息时调用，set_ev_cls的第一个参数也声明了。
    #set_ev_cls的第二个参数MAIN_DISPATCHER意味着当Ryu和交换机握手过程（即hello, features request/reply, Set Config等）完毕，才会调用packet_in_handler。
    def packet_in_handler(self, ev):
        msg = ev.msg
        dp = msg.datapath
        ofp = dp.ofproto
        ofp_parser = dp.ofproto_parser
        actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]
        out = ofp_parser.OFPPacketOut(
            datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port,
            actions=actions)
        dp.send_msg(out)

2.根据官方教程和提供的示例代码（SimpleSwitch.py），将具有自学习功能的交换机代码（SelfLearning.py）补充完整

代码链接

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_0

from ryu.lib.mac import haddr_to_bin
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ether_types


class SimpleSwitch(app_manager.RyuApp):
    # TODO define OpenFlow 1.0 version for the switch
    OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]

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

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

        match = datapath.ofproto_parser.OFPMatch(
            in_port=in_port,
            dl_dst=haddr_to_bin(dst), dl_src=haddr_to_bin(src))

        mod = datapath.ofproto_parser.OFPFlowMod(
            datapath=datapath, match=match, cookie=0,
            command=ofproto.OFPFC_ADD, idle_timeout=0, hard_timeout=0,
            priority=ofproto.OFP_DEFAULT_PRIORITY,
            flags=ofproto.OFPFF_SEND_FLOW_REM, actions=actions)

        # TODO send modified message out
        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

        pkt = packet.Packet(msg.data)
        eth = pkt.get_protocol(ethernet.ethernet)

        if eth.ethertype == ether_types.ETH_TYPE_LLDP:
            # ignore lldp packet
            return
        if eth.ethertype == ether_types.ETH_TYPE_IPV6:
            # ignore ipv6 packet
            return

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

        self.logger.info("packet in DPID:%s MAC_SRC:%s MAC_DST:%s IN_PORT:%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

        # TODO define the action for output
        actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]

        # install a flow to avoid packet_in next time
        if out_port != ofproto.OFPP_FLOOD:
            self.logger.info("add flow s:DPID:%s Match:[ MAC_SRC:%s MAC_DST:%s IN_PORT:%s ], Action:[OUT_PUT:%s] ",
                             dpid, src, dst, msg.in_port, out_port)
            self.add_flow(datapath, msg.in_port, dst, src, actions)

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

        # TODO define the OpenFlow Packet Out
        out = datapath.ofproto_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
                                                   actions=actions, data=data)
        datapath.send_msg(out)

    print("PACKET_OUT...")

3.在mininet创建一个最简拓扑，并连接RYU控制器

使用Python脚本创建拓扑

from mininet.topo import Topo

class MyTopo(Topo):

    def __init__(self):

        # initilaize topology
        Topo.__init__(self)

        # add hosts and switches
        h1 = self.addHost('h1')
        h2 = self.addHost('h2')

        s1 = self.addSwitch('s1')

        # add links
        self.addLink(h1, s1, 1, 1)
        self.addLink(h2, s1, 1, 2)
        
topos = {'mytopo': (lambda: MyTopo())}

4.验证自学习交换机的功能，提交分析过程和验证结果

查看s1流表

连接RYU控制器

h1 ping h2

再次查看流表

Wireshark抓包分析

5.实验体会

本次实验出师不利，安装软件的第一步就出差错，好在助教的耐心帮助下成功解决。由于本身对python不是很了解，改代码期间缩进出了一些差错，浪费了比较多时间，解决之后就比较顺利了，也对ryu控制器有初步了解。