2019 SDN上机第5次作业

1.浏览RYU官网学习RYU控制器的安装和RYU开发入门教程，提交你对于教程代码的理解，包括但不限于：

• 描述官方教程实现了一个什么样的交换机功能？
  将接收到的数据包发送到所有端口

• 控制器设定交换机支持什么版本的OpenFlow？
  openflow 1.0

• 控制器设定了交换机如何处理数据包？
  @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)装饰器告诉Ryu何时应调用装饰的函数

  • 第一个参数指示应调用此函数的事件类型
  • 第二个参数指示开关的状态

  packet_in_handler函数

  • ev.msg是表示packet_in数据结构的对象。
  • msg.dp是代表数据路径（开关）的对象。
  • dp.ofproto和dp.ofproto_parser是代表Ryu和交换机协商的OpenFlow协议的对象。
  • OFPActionOutput类与packet_out消息一起使用，以指定要从中发送数据包的交换机端口。该应用程序使用OFPP_FLOOD标志来指示应在所有端口上发送数据包。
  • OFPPacketOut类用于构建packet_out消息。
  • 如果使用OpenFlow消息类对象调用Datapath类的send_msg方法，则Ryu会生成联机数据格式并将其发送到交换机。

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

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
	# add your code here
	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
		# add your code here
		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
		# add your code here
		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
		# add your code here
		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

python脚本：

from mininet.topo import Topo
 
class MyTopo( Topo ):
 
    def __init__( self ):
        Topo.__init__( self )
        s1=self.addSwitch('s1')
        for i in range(1,3):
                hw = self.addSwitch( 's{}'.format( i ) )
                self.addLink(hw,s1)
        
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