实验6:开源控制器实践——RYU

一、基础要求

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。

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2.分析L2Switch和POX的Hub模块有何不同。

pox的Hub模块可以在运行时查看流表,而ryu的L2Switch模块无法在运行时查看到流表。不过他们也有相同点:都是依靠洪泛转发。

3.修改过的L2xxxxxxxxx.py代码和能够体现和验证修改的相关截图

代码截图:

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修改后运行结果:

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二、进阶要求

1.完成其代码的注释工作,回答下列问题:

代码注释:

# 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.

# 引入数据包
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)
        self.mac_to_port = {}  # 定义保存mac地址到端口的一个映射

    # 处理SwitchFeatures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()  # match指流表项匹配,OFPMatch()指不匹配任何信息
        actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                          ofproto.OFPCML_NO_BUFFER)]
        self.add_flow(datapath, 0, match, actions)

    # add_flow()增加流表项
    # datapath:指定的 Switch;priority:此规则的优先权;match:此规则的 Match 条件;actions:动作
    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)]
        # 判断是否存在buffer_id,并生成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)
        # 发送出去
        datapath.send_msg(mod)

    # 处理PacketIn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)
        # 解析数据结构
        msg = ev.msg
        datapath = msg.datapath
        # dp. ofproto 和 dp.ofproto_parser 是代表 Ryu 和交换机谈判的 OpenFlow 协议的对象
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser
        # 获取源端口
        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:
            # 忽略LLDP类型的数据包
            return
        dst = eth.dst  # 获取目的端口
        src = eth.src  # 获取源端口

        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
        self.mac_to_port[dpid][src] = in_port

        # 查看是否已经学习过该目的mac地址
        # 如果目的地址存在于mac_to_port中
        if dst in self.mac_to_port[dpid]: 
            out_port = self.mac_to_port[dpid][dst]
        # 如果没有学习过该目的mac地址
        else:
            # OFPP_FLOOD标志表示应在所有端口发送数据包,即洪泛
            out_port = ofproto.OFPP_FLOOD  

        actions = [parser.OFPActionOutput(out_port)]

        # 下发流表避免下次触发 packet in 事件
        if out_port != ofproto.OFPP_FLOOD:
            match = parser.OFPMatch(in_port=in_port, eth_dst=dst, eth_src=src)
            # 验证我们是否有一个有效的buffer_id,如果是避免发送两个
            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

        # 发送Packet_out数据包
        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)

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

b) simple_switch和simple_switch_13在dpid的输出上有何不同?

simple_switch_13会用0在dpid前填充至总长度为16,而simple_switch直接输出dpid。

这可以从以下代码看出。

dpid = format(datapath.id, "d").zfill(16)
       self.mac_to_port.setdefault(dpid, {})
dpid = datapath.id
        self.mac_to_port.setdefault(dpid, {})

c) 相比simple_switch,simple_switch_13增加的switch_feature_handler实现了什么功能?

simple_switch_13交换机可以以特性应答消息来响应特性请求

d) simple_switch_13是如何实现流规则下发的?

  • 在触发packetIn事件后,解析相关数据结构,获取协议信息、获取源端口、包学习,交换机信息,以太网信息等多种信息。
  • 如果以太网类型是LLDP类型,则忽略。
  • 如果不是LLDP类型,则获取目的端口和源端口以及交换机id,
  • 然后进行交换机自学习,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,如果没有就进行洪泛转发。如果学习过,查看是否有buffer_id,如果有则在添加流时加上buffer_id,向交换机发送数据包和流表。

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的优先级更高

2.编程实现和ODL实验的一样的硬超时功能

代码:

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):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(SimpleSwitch13, self).__init__(*args, **kwargs)
        self.mac_to_port = {}

    @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
        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, hard_timeout=0):
        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, hard_timeout=hard_timeout)
        else:
            mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                    match=match, instructions=inst, hard_timeout=hard_timeout)
        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

        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)

        # learn a mac address to avoid FLOOD next time.
        self.mac_to_port[dpid][src] = in_port

        if dst in self.mac_to_port[dpid]:
            out_port = self.mac_to_port[dpid][dst]
        else:
            out_port = ofproto.OFPP_FLOOD

        actions = [parser.OFPActionOutput(out_port)]\

        actions_timeout=[]

        # 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
            hard_timeout=10
            if msg.buffer_id != ofproto.OFP_NO_BUFFER:
                self.add_flow(datapath, 2, match,actions_timeout, msg.buffer_id,hard_timeout=10)
                self.add_flow(datapath, 1, match, actions, msg.buffer_id)
                return
            else:
                self.add_flow(datapath, 2, match, actions_timeout, hard_timeout=10)
                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)
        datapath.send_msg(out)


硬超时效果:

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三、个人总结

  1. 本次实验难度偏难。
  2. 首先是一开始连ryu manager都运行不了,遇到cannot set 'is_timeout' attribute of immutable type 'TimeoutError'的错误。经过不断地网上搜索和调试,摸索出解决方案为先pip install eventlet,此时还是会报错,不过报错会变为AttributeError: module 'collections' has no attribute 'MutableMapping',此时只需要将namedict.py文件中的collections.MutableMapping改成collections.abc.MutableMapping即可解决报错,成功运行ryu控制器。
  3. 然后是查看流表时报错s1.mgmt: version negotiation failed (we support version 0x01, peer supports version 0x04) ovs-ofctl: s1: failed to connect to socket (Broken pipe),最后是在老师的博客中找到了解决的方法。
  4. 本次实验学习了一下ryu控制器,也体会了一下ryu和pox的区别,但对ryu的理解感觉还不是很全面,仍需要加强学习。看英文文档挺痛苦的,不管是之前的ryu还是pox,也算是初步体会到了英语的重要性。机翻总有一些翻译得奇奇怪怪的地方,还是要加强英语文献阅读能力。
posted @ 2022-10-18 15:36  冬昼  阅读(217)  评论(0编辑  收藏  举报