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？
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。
控制器设定交换机支持什么版本的OpenFlow？
OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]
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)#修饰器，告诉Ryu什么时候调用修饰的函数，用“ MAIN_DISPATCHER”作为第二个参数表示仅在协商完成后才调用此函数。
#当Ryu收到OpenFlow packet_in消息时，将调用此方法
    def packet_in_handler(self, ev):
        msg = ev.msg#packet_in数据结构的对象
        dp = msg.datapath#数据路径的对象
        ofp = dp.ofproto
        ofp_parser = dp.ofproto_parser
        #dp.ofproto和dp.ofproto_parser是代表Ryu和交换机协商的OpenFlow协议的对象。
        actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]
        #指定要从中发送数据包的交换机端口,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)
        #用于构建packet_out消息
        dp.send_msg(out)
        #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
        # 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

py代码

from mininet.topo import Topo
from mininet.net import Mininet
from mininet.node import RemoteController,CPULimitedHost
from mininet.link import TCLink
from mininet.util import dumpNodeConnections
 
class MyTopo( Topo ):
    "Simple topology example."
 
    def __init__( self ):
        "Create custom topo."
 
        Topo.__init__( self )

    switchs = []
        sw = self.addSwitch("s{}".format(1))
        switchs.append(sw)  

        for sw in switchs:
            for i in range(2):
                h = self.addHost("h{}".format(i+1))
                self.addLink(sw, h)
        
topos = { 'mytopo': ( lambda: MyTopo() ) }