实验6:开源控制器实践——RYU

(一)基本要求
1、搭建下图所示SDN拓扑,协议使用Open Flow 1.0,并连接Ryu控制器,通过Ryu的图形界面查看网络拓扑。
构建topo


2.阅读Ryu文档的The First Application一节,运行当中的L2Switch,h1 ping h2或h3,在目标主机使用 tcpdump 验证L2Switch,分析L2Switch和POX的Hub模块有何不同。

编写L2Switch.py

点击查看代码
 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)
     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)]

         data = None
         if msg.buffer_id == ofp.OFP_NO_BUFFER:
              data = msg.data

         out = ofp_parser.OFPPacketOut(
             datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port,
             actions=actions, data = data)
         dp.send_msg(out)


运行L2Switch.py

h1 ping h2或h3在目标主机使用 tcpdump 验证L2Switch

查看流表

pox下查看拓扑流表

分析:RYU的L2Switch模块和POX的Hub模块都采用洪泛转发,但不同之处在于:
可以在pox的Hub模块运行时查看流表,而无法在ryu的L2Switch模块运行时查看到流表

编程修改L2Switch.py,另存为L2xxxxxxxxx.py,使之和POX的Hub模块的变得一致?(xxxxxxxxx为学号)
L2212002125.py

点击查看代码
from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import CONFIG_DISPATCHER, 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.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)

    def add_flow(self, datapath, priority, match, actions, buffer_id=None):
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                             actions)]
        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)
        datapath.send_msg(mod)

    @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
        in_port = msg.match['in_port']

        actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]

        data = None
        if msg.buffer_id == ofp.OFP_NO_BUFFER:
             data = msg.data

        out = ofp_parser.OFPPacketOut(
            datapath=dp, buffer_id=msg.buffer_id, in_port=in_port,
            actions=actions, data = data)
        dp.send_msg(out)



![](https://img2022.cnblogs.com/blog/2965917/202210/2965917-20221026164235922-2054112274.png)

(二)进阶要求
1阅读Ryu关于simple_switch.py和simple_switch_1x.py的实现,以simple_switch_13.py为例,完成其代码的注释工作,并回答下列问题

点击查看代码
# 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.

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
# 继承ryu.base.app_manager.RyuApp

class SimpleSwitch13(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]  # 版本号为1.3

    def __init__(self, *args, **kwargs):  # 初始化类
        super(SimpleSwitch13, self).__init__(*args, **kwargs)
        self.mac_to_port = {}  # 初始化mac_to_port数组

    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
    def switch_features_handler(self, ev):  # 安装无目标的流表条目
        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)

    def add_flow(self, datapath, priority, match, actions, buffer_id=None):  # 增加流表
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                             actions)]
        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)
        datapath.send_msg(mod)

    @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)
        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]

        if eth.ethertype == ether_types.ETH_TYPE_LLDP:
            # ignore lldp packet
            return
        dst = eth.dst
        src = eth.src  # 用packet library分析收到的数据包

        dpid = format(datapath.id, "d").zfill(16)  # 获得Datapath ID以便于识别OpenFlow交换机
        self.mac_to_port.setdefault(dpid, {})

        self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)

        # learn a mac address to avoid FLOOD next time.
        self.mac_to_port[dpid][src] = in_port  # 记录mac地址以避免下次的消息范洪

        if dst in self.mac_to_port[dpid]:  # 如果目标Mac地址已经被学习了,决定哪个从哪个端口发送数据包。否则范洪
            out_port = self.mac_to_port[dpid][dst]
        else:
            out_port = ofproto.OFPP_FLOOD

        actions = [parser.OFPActionOutput(out_port)]  # 构造action表

        # 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
        # 构造一个pack_out消息然后发送
        out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
                                  in_port=in_port, actions=actions, data=data)
        datapath.send_msg(out)


2)对回答相关问题 a) 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

b) simple_switch和simple_switch_13在dpid的输出上有何不同?
差别在于:simple_switch直接输出dpid,而simple_switch_13则在dpid前端填充0直至满16位

c) 相比simple_switch,simple_switch_13增加的switch_feature_handler实现了什么功能?
实现了交换机以特性应答消息来响应特性请求的功能。

d) 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。若以太网类型是LLDP类型,则不予处理。如果不是,则获取源端口的目的端口和交换机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,则在添加流表信息时加上buffer_id,向交换机发送流表。

e) switch_features_handler和_packet_in_handler两个事件在发送流规则的优先级上有何不同?
switch_features_handler下发流表的优先级比_packet_in_handler的优先级高。

2.编程实现和ODL实验的一样的硬超时功能。

个人总结:
本次实验主要考察部署RYU控制器;RYU控制器实现软件定义的集线器原理;RYU控制器实现软件定义的交换机原理,实验的基础部分难度比较简单主要是要对比分析L2Switch和POX的Hub模块的不同,在连接ryu以后再打开L2Switch.py时构建拓扑,pingall不通时可以sudo killall ovsdb-server,杀死OVS再udo service openvswitch-switch force-reload-kmod重启ovs即可

posted @ 2022-10-27 23:44  212002125王昊  阅读(36)  评论(0编辑  收藏  举报