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？

泛洪转发:使交换机能够将收到的数据包转发到所有端口

控制器设定交换机支持什么版本的OpenFlow？

支持OpenFlow1.0:OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]

教程代码：

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.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

控制器设定了交换机如何处理数据包？

@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)//当Ryu收到OpenFlow packet_in调用“packet_in_handler”方法

        msg = ev.msg//用ev.msg对象创建一个packet_in数据结构
        datapath = msg.datapath//一个数据路径（开关？）
        eth = pkt.get_protocol(ethernet.ethernet)//以太网链路协议
        dpid = datapath.id
        out_port = ofproto.OFPP_FLOOD//OFPP_FLOOD应该是提供泛洪功能的端口号，把接收到的数据包转发到这个端口，实现泛洪。
        actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]//设置下发动作
        out = datapath.ofproto_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,  actions=actions, data=data)//转发出的数据包
        datapath.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

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

在终端直接使用命令创建拓扑：

此时没有连接ryu控制器，主机都无法连通

下面在另一个终端连接RYU控制器：

4.验证自学习交换机的功能，提交分析过程和验证结果

在连接RYU控制器后，再次测试h1和h2的连通性，可以看到h1和h2已经可以ping通了：

查看交换机的流表，发现多了端口二发往端口一和端口一发往端口二的两条流表，当前拓扑只有两台主机，所以只有两条流表：

5.写下你的实验体会

做了这么多次的SDN实验了，这已经是第五次的作业了，这次内容是不难的，主要的问题应该是都在RYU控制器的安装和Python、pip的配置了。前几天没有完成作业是因为无法运行ryu控制器，再安装完RYU控制器后，准备运行测试文件时，就会因为无法找到usr/bin/pip3文件内main（）函数而报错，无法运行。上网搜了下发现是因为pip版本的问题，最后的解决办法是修改文件读写权限，把正确的pip3.py文件内容写入。