• 实验6:开源控制器实践——RYU


    一、实验目的

    1. 能够独立部署RYU控制器
    2. 能够理解RYU控制器实现软件定义的集线器原理
    3. 能够理解RYU控制器实现软件定义的交换机原理

    二、实验环境

    1. 下载虚拟机软件Oracle VisualBox或VMware;
    2. 在虚拟机中安装Ubuntu 20.04 Desktop amd64,并完整安装Mininet;

    三、实验要求

    (一)基本要求

    1. 完成Ryu控制器的安装
      在Ryu安装目录下执行ryu --version查看版本

    2. 搭建下图所示SDN拓扑,协议使用Open Flow 1.0,并连接Ryu控制器。

    3. 拓扑可视化

    4. tcpdump查看
      h1 ping h2

    h1 ping h3

    可以看到均为洪泛转发
    查看控制器流表,如下图:

    看到没有流表,而使用pox的hub模块则会看到流表,如下图:

    所以可以看到二者都是洪泛转发,但是不同之处在于POX是直接向交换机下发流表,而Ryu是在每个 Packet In 事件之后,向交换机下发动作。

    (二)进阶要求

    simple_switch_13.py

    # Copyright (C) 2011 Nippon Telegraph and Telephone Corporation.
    #
    # Licensed under the Apache License, Version 2.0 (the "License");
    # you may not use this file except in compliance with the License.
    # You may obtain a copy of the License at
    #
    #    http://www.apache.org/licenses/LICENSE-2.0
    #
    # Unless required by applicable law or agreed to in writing, software
    # distributed under the License is distributed on an "AS IS" BASIS,
    # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
    # implied.
    # See the License for the specific language governing permissions and
    # limitations under the License.
    
    # 引入包
    from ryu.base import app_manager
    from ryu.controller import ofp_event
    from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
    from ryu.controller.handler import set_ev_cls
    from ryu.ofproto import ofproto_v1_3
    from ryu.lib.packet import packet
    from ryu.lib.packet import ethernet
    from ryu.lib.packet import ether_types
    
    
    class SimpleSwitch13(app_manager.RyuApp):
        # 定义openflow版本
        OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
    
        def __init__(self, *args, **kwargs):
            super(SimpleSwitch13, self).__init__(*args, **kwargs)
            # 定义保存mac地址到端口的一个映射
            self.mac_to_port = {}
    
        # 处理EventOFPSwitchFeatures事件
        @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
        def switch_features_handler(self, ev):
            datapath = ev.msg.datapath
            ofproto = datapath.ofproto
            parser = datapath.ofproto_parser
    
            # install table-miss flow entry
            #
            # We specify NO BUFFER to max_len of the output action due to
            # OVS bug. At this moment, if we specify a lesser number, e.g.,
            # 128, OVS will send Packet-In with invalid buffer_id and
            # truncated packet data. In that case, we cannot output packets
            # correctly.  The bug has been fixed in OVS v2.1.0.
            match = parser.OFPMatch()
            actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                              ofproto.OFPCML_NO_BUFFER)]
            self.add_flow(datapath, 0, match, actions)
    
        # 添加流表函数
        def add_flow(self, datapath, priority, match, actions, buffer_id=None):
            # 获取交换机信息
            ofproto = datapath.ofproto
            parser = datapath.ofproto_parser
    
            # 对action进行包装
            inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                                 actions)]
            # 判断是否有buffer_id,生成mod对象
            if buffer_id:
                mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
                                        priority=priority, match=match,
                                        instructions=inst)
            else:
                mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                        match=match, instructions=inst)
            # 发送mod
            datapath.send_msg(mod)
    
        # 处理 packet in 事件
        @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
        def _packet_in_handler(self, ev):
            # If you hit this you might want to increase
            # the "miss_send_length" of your switch
            if ev.msg.msg_len < ev.msg.total_len:
                self.logger.debug("packet truncated: only %s of %s bytes",
                                  ev.msg.msg_len, ev.msg.total_len)
            # 获取包信息,交换机信息,协议等等
            msg = ev.msg
            datapath = msg.datapath
            ofproto = datapath.ofproto
            parser = datapath.ofproto_parser
            in_port = msg.match['in_port']
    
            pkt = packet.Packet(msg.data)
            eth = pkt.get_protocols(ethernet.ethernet)[0]
    
            # 忽略LLDP类型
            if eth.ethertype == ether_types.ETH_TYPE_LLDP:
                # ignore lldp packet
                return
    
            # 获取源端口,目的端口
            dst = eth.dst
            src = eth.src
    
            dpid = format(datapath.id, "d").zfill(16)
            self.mac_to_port.setdefault(dpid, {})
    
            self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)
    
            # 学习包的源地址,和交换机上的入端口绑定
            # learn a mac address to avoid FLOOD next time.
            self.mac_to_port[dpid][src] = in_port
    
            # 查看是否已经学习过该目的mac地址
            if dst in self.mac_to_port[dpid]:
                out_port = self.mac_to_port[dpid][dst]
            # 否则进行洪泛
            else:
                out_port = ofproto.OFPP_FLOOD
    
            actions = [parser.OFPActionOutput(out_port)]
    
            # 下发流表处理后续包,不再触发 packet in 事件
            # install a flow to avoid packet_in next time
            if out_port != ofproto.OFPP_FLOOD:
                match = parser.OFPMatch(in_port=in_port, eth_dst=dst, eth_src=src)
                # verify if we have a valid buffer_id, if yes avoid to send both
                # flow_mod & packet_out
                if msg.buffer_id != ofproto.OFP_NO_BUFFER:
                    self.add_flow(datapath, 1, match, actions, msg.buffer_id)
                    return
                else:
                    self.add_flow(datapath, 1, match, actions)
            data = None
            if msg.buffer_id == ofproto.OFP_NO_BUFFER:
                data = msg.data
    
            out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
                                      in_port=in_port, actions=actions, data=data)
            # 发送流表
            datapath.send_msg(out)
    

    代码当中的mac_to_port的作用是什么?
    保存mac地址到交换机端口的映射,为交换机自学习功能提供数据结构进行 mac-端口 的存储

    simple_switch和simple_switch_13在dpid的输出上有何不同?
    simple_switch的dpid赋值:dpid = datapath.id

    simple_switch_13的dpid赋值:dpid = format(datapath.id, "d").zfill(16)

    在python console进行测试,可以看到在simple_switch直接获取的id,在simple_switch_13中,会在前端加上0将其填充至16位

    相比simple_switch,simple_switch_13增加的switch_feature_handler实现了什么功能?
    实现交换机以特性应答消息响应特性请求

    simple_switch_13是如何实现流规则下发的?
    在接收到packetin事件后,首先获取包学习,交换机信息,以太网信息,协议信息等。如果以太网类型是LLDP类型,则不予处理。如果不是,则获取源端口目的端口,以及交换机id,先学习源地址对应的交换机的入端口,再查看是否已经学习目的mac地址,如果没有则进行洪泛转发。如果学习过该mac地址,则查看是否有buffer_id,如果有的话,则在添加流动作时加上buffer_id,向交换机发送流表。

    实验总结

    本次实验难度真的可以说是蛮大的,对源码分析和对openflow协议的理解的要求进一步提高,在拓扑可视化方面遇到了一些问题,但还是很好的解决了。体感实验六和实验五有一定相似性。在学习完本次实验后,我已经能够独立部署RYU控制器,并且能够理解RYU控制器实现软件定义的集线器原理,还能够理解RYU控制器实现软件定义的交换机原理。通过本次实验进一步加深了我对代码的理解,对我的学习有很大的帮助。

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  • 原文地址:https://www.cnblogs.com/zhaoruiyan955/p/15399797.html
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