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

(1)描述官方教程实现了一个什么样的交换机功能?

让交换机将接收到的数据包发送到所有端口的功能。

(2)控制器设定交换机支持什么版本的OpenFlow?

OpenFlow v1.0

(3)控制器设定了交换机如何处理数据包?
@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)

如上方代码所示,新方法'packet_in_handler'已添加到L2Switch类。当Ryu收到OpenFlow packet_in消息时,将调用此方法。诀窍是“ set_ev_cls”装饰器。该装饰器告诉Ryu何时应调用装饰的函数。装饰器的第一个参数指示应调用此函数的事件类型;第二个参数指示开关的状态。
在packet_in_handler函数的前半部分:

  • 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;

在packet_in_handler函数的后半部分:

  • 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;
  • 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。

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
    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.在mininet创建一个最简拓扑,并连接RYU控制器

  • 创建只有一个交换机两个主机的简单Topo
sudo mn --controller=remote,ip=127.0.0.1,port=6633

image.png

  • 进入selflearning.py目录下,使用命令连接RYU控制器
ryu-manager selflearning.py

image.png

  • 查看s1流表情况,发现没有流表下发
sudo ovs-ofctl dump-flows s1

4.验证自学习交换机的功能,提交分析过程和验证结果

  • 当使用ping命令连接h1和h2时,收到交换机下发的流表
    image.png

5.写下你的实验体会

按照助教博客的指导来安装ryu,过程还是非常顺利的,就是虚拟机内存紧张,幸好ryu还不算大。通过这次实验,我对ryu的学习有了进一步的理解和认识,发现ryu来控制流表下发还是非常方便的。