2019 SDN上机第5次作业

浏览RYU官网学习RYU控制器的安装和RYU开发入门教程，提交对于教程代码的理解：

描述官方教程实现了一个什么样的交换机功能？
官方教程实现了一个将接收到的数据包发送到所有端口的交换机功能
控制器设定交换机支持什么版本的OpenFlow？
控制器设定交换机支持OpenFlow 1.0
控制器设定了交换机如何处理数据包？

首先通过以下这个语句设置想要向交换机协商的OpenFlow版本号
```
OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION] 
```
给出官方的代码，这一部分是实现将接收到的数据包发送到所有端口的功能。
```
    @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)]
        out = ofp_parser.OFPPacketOut(
            datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port,
            actions=actions)
        dp.send_msg(out)
```
- packet_in_handler(self, ev) 这个是新方法，表明当Ryu收到OpenFlow packet_in消息时，将产生事件（调用“packet_in_handler”方法）
- set_ev_cls：是个修饰器，它功能就是告诉Ryu啥时候调用它要修饰的那个函数。
- 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。用它来选择要往哪个交换机端口发送。
- 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。
- send_msg() ：它的作用就是让Ryu建立在线数据格式结构并发送给交换机。

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
    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
        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
        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
        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...")

在mininet创建一个最简拓扑，并连接RYU控制器

使用Python脚本创建拓扑

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())}