实验6：开源控制器实践——RYU

实验6：开源控制器实践——RYU

一、实验目的

1. 能够独立部署RYU控制器；
2. 能够理解RYU控制器实现软件定义的集线器原理；
3. 能够理解RYU控制器实现软件定义的交换机原理。

二、实验环境

Ubuntu 20.04 Desktop amd64

三、实验要求

（一）基本要求

1. 搭建下图所示SDN拓扑，协议使用Open Flow 1.0，并连接Ryu控制器，通过Ryu的图形界面查看网络拓扑。
2. 使用命令sudo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow10搭建拓扑
   

　　　

• 在对应文件夹下执行ryu-manager gui_topology.py --observe-links启动控制器
• 

   

   

　　　　通过Ryu的图形界面查看网络拓扑

• 

   

   

  
  

   

   

1. 阅读Ryu文档的The First Application一节，运行当中的L2Switch，h1 ping h2或h3，在目标主机使用 tcpdump 验证L2Switch，分析L2Switch和POX的Hub模块有何不同。

　　　　

• 创建L2Switch.py文件,并保存在目录/home/用户名/学号/lab6/中

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

class L2Switch(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(L2Switch, self).__init__(*args, **kwargs)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    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)]

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

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

• 执行命令ryu-manager L2Switch.py

　　

 

 

 

 

 

 二者实现的都是洪泛发送ICMP报文，所以在h2和h3可以看到都有抓到数据包。
不同之处在于：Ryu中，L2Switch下发的流表无法查看；而POX中Hub则可以查看。

 

• 编程修改L2Switch.py，另存为L2xxxxxxxxx.py，使之和POX的Hub模块的变得一致（xxxxxxxxx为学号）

  from ryu.base import app_manager
  from ryu.ofproto import ofproto_v1_3
  from ryu.controller import ofp_event
  from ryu.controller.handler import MAIN_DISPATCHER, CONFIG_DISPATCHER
  from ryu.controller.handler import set_ev_cls
   
   
  class hub(app_manager.RyuApp):
      OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
   
      def __init__(self, *args, **kwargs):
          super(hub, self).__init__(*args, **kwargs)
   
      @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
      def switch_feathers_handler(self, ev):
          datapath = ev.msg.datapath
          ofproto = datapath.ofproto
          ofp_parser = datapath.ofproto_parser
   
          # install flow table-miss flow entry
          match = ofp_parser.OFPMatch()
          actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, ofproto.OFPCML_NO_BUFFER)]
          # 1\OUTPUT PORT, 2\BUFF IN SWITCH?
          self.add_flow(datapath, 0, match, actions)
   
      def add_flow(self, datapath, priority, match, actions):
          # 1\ datapath for the switch, 2\priority for flow entry, 3\match field, 4\action for packet
          ofproto = datapath.ofproto
          ofp_parser = datapath.ofproto_parser
          # install flow
          inst = [ofp_parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS, actions)]
          mod = ofp_parser.OFPFlowMod(datapath=datapath, priority=priority, 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
          ofp_parser = datapath.ofproto_parser
          in_port = msg.match['in_port']  # get in port of the packet
   
          # add a flow entry for the packet
          match = ofp_parser.OFPMatch()
          actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_FLOOD)]
          self.add_flow(datapath, 1, match, actions)
   
          # to output the current packet. for install rules only output later packets
          out = ofp_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=in_port, actions=actions)
          # buffer id: locate the buffered packet
          datapath.send_msg(out)

• 

  实验总结

  .个人心得：
  先启用ryu控制器，而后打开Ryu验证L2Switch，最后再进行拓扑构建，即可使用tcpdump顺利验证实验结论。