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？

收到数据包就用泛洪的方式实现同一局域网内主机的互通

• 控制器设定交换机支持什么版本的OpenFlow？

OpenFlow 1.0，OpenFlow 1.1，OpenFlow 1.2，OpenFlow 1.3

• 控制器设定了交换机如何处理数据包？

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.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ether_types
from ryu.lib.packet import ipv4


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

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

	@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
  
		print ("PACKET_IN:")

		print (eth.ethertype)
		print ("ethernet:")
		print ("eth_src=",eth.src)
		print ("eth_dst=",eth.dst)

		if eth.ethertype == ether_types.ETH_TYPE_IP:
			_ipv4 = pkt.get_protocol(ipv4.ipv4)
			print ("ipv4:")
			print ("ip_src=",_ipv4.src)
			print ("ip_dst=",_ipv4.dst)
           

		dpid = datapath.id

		out_port = ofproto.OFPP_FLOOD
		actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]

		data = None

		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...")
		print

示例代码可以分为3部分来看

+ 初始化（init）
+ 接收数据包并做判定，在这个部分中，我主要关心这几个数据结构
    - msg，这个结构应该是一个完整的数据包的结构
    - datapath，是一个数据路径，在本例中可以看出他包含ofproto
    - ofproto，openflowprotocal，在本例中ofproto的作用是提供泛洪功能（不是很清楚怎么表述），见51行的ofproto.OFPP_FLOOD
    - pkt和eth是函数返回的数据结构，eth包含由链路层协议类型
+ 下发流表，指导数据包的转发
    - outport，出接口
    - actions,执行动作

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

• 创建拓扑的python代码如下所示：

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())}

• 执行代码的命令如下（注意选择OPENFLOW协议）：

sudo mn --custom ./test.py --topo mytopo --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow10

• 运行mininet以后即创建网络拓
  

• 做联通测试，此时没有控制器指挥转发，h1和h2是无法实现双向连通的
  

• 运行RYU控制器，指导交换机执行转发，可以看到控制器在执行h1 ping h2的时候下发流表指导转发
  

• 此时已经可以实现互通
  

• 查看交换机S1的流表，看到相关的条目
  

5.写下你的实验体会

这次的实验其实也比较简单，最难的步骤应该是安装RYU。剩下的部分就是读懂代码，要自己补充的代码其实从示例代码中复制进去就好了。就是最近事情比较多，交的就比较晚了。