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？
- 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？
- OpenFlow 1.0
控制器设定了交换机如何处理数据包？
- 下面我们通过看代码和注释来说明
  
  主要完成将接收到的数据包发送到所有端口的功能。

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

class L2Switch(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(L2Switch, self).__init__(*args, **kwargs)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)//该装饰器告诉Ryu何时应调用装饰的函数。
    #第一个参数指示应调用此函数的事件类型，可以看到是收到packet_消息时调用
   #第二个参数指示开关的状态，MAIN_DISPATCHER表示仅在Ryu和交换机协商完成后才调用这个函数

    def packet_in_handler(self, ev): #新方法'packet_in_handler'已添加到L2Switch类
        msg = ev.msg #表示packet_in数据结构的对象
        dp = msg.datapath #代表数据路径（开关）的对象
        ofp = dp.ofproto
        ofp_parser = dp.ofproto_parser #这两个代表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。
        actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)] #OFPP_FLOOD标志来指示应在所有端口上发送数据包
        out = ofp_parser.OFPPacketOut( #用于构建packet_out消息
            datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port,
            actions=actions)
        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

代码链接

代码补全结果，有些地方代码需要理解挺久的才能懂，主要还是看官方的教程和搜索引擎学习完成。

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]
    #定义使用OpenFlow 1.0协议


    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)
        #发送修改后的信息
    @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)]
        #设置动作，发出的端口

            # install a flow to avoid packet_in next time
        #安装流表项来防止交换机遇到同样流表项不知道怎么处理而发送给控制器
        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

from mininet.topo import Topo

class MyTopo(Topo):

    def __init__(self):

        
        Topo.__init__(self)

        h1 = self.addHost('h1')
        h2 = self.addHost('h2')

        s1 = self.addSwitch('s1')

        self.addLink(h1, s1, 1, 1)
        self.addLink(h2, s1, 1, 2)
        
topos = {'mytopo': (lambda: MyTopo())}