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：

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描述官方教程实现了一个什么样的交换机功能？

Add some features to enable the switch to forward the received packets to all ports.

控制器设定交换机支持什么版本的OpenFlow？

支持OpenFlow v1.0

控制器设定了交换机如何处理数据包？

	@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
     //表明当Ryu收到OpenFlow packet_in消息时，将产生事件（调用“packet_in_handler”方法）
    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)]
           //动作列表。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。
        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

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补充后的完整代码：

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]
	# add your code here

	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

		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)

3.创建一个最简拓扑，并连接RYU控制器

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在SimpleSwitch.py目录下运行：

ryu-manager selflearning.py

在本机使用mininet创建最简拓扑：

sudo mn --controller=remote,ip=127.0.0.1,port=6633

4.验证自学习交换机的功能，提交分析过程和验证结果

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此时交换机s1上并无流表：

在Mininet CLI运行h1 ping h2，h1发送广播寻找h2，

再次使用sudo ovs-ofctl dump-flows s1查看流表：

h1 ping h2时，在wireshark抓包分析如下：

5.写下你的实验体会

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安装是个漫长又艰难的过程，面临着虚拟机随时可能崩溃的危险，但按照老师的教程一步一步走下来，最终还是成功安装好了。ryu控制器的框架理解起来也有一定的困难，看了不少教程，稍微有些理解，通过实践，进一步加深理解。ryu比较灵活，可以用来打造属于自己风格的自定义控制器。