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

Ubuntu 20.04 Desktop amd64

三、实验要求

(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。

建立拓扑,连接上RYU控制器

在浏览器中输入地址http://127.0.0.1:8080查看ryu的图形界面

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。

L2Switch.py代码如下

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)

h1 ping h2

h1 ping h3

L2Switch和POX的Hub模块不同之处:

Hub和L2Switch模块都是洪泛转发,但L2Switch模块下发的流表无法查看,而Hub模块下发的流表可以查看。

3.编程修改L2Switch.py,另存为L2032002445.py,使之和POX的Hub模块的变得一致?

from ryu.base import app_manager
from ryu.ofproto import ofproto_v1_3
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER, CONFIG_DISPATCHER
from ryu.controller.handler import set_ev_cls
 
 
class hub(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
 
    def __init__(self, *args, **kwargs):
        super(hub, self).__init__(*args, **kwargs)
 
    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
    def switch_feathers_handler(self, ev):
        datapath = ev.msg.datapath
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser
 
        # install flow table-miss flow entry
        match = ofp_parser.OFPMatch()
        actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, ofproto.OFPCML_NO_BUFFER)]
        # 1\OUTPUT PORT, 2\BUFF IN SWITCH?
        self.add_flow(datapath, 0, match, actions)
 
    def add_flow(self, datapath, priority, match, actions):
        # 1\ datapath for the switch, 2\priority for flow entry, 3\match field, 4\action for packet
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser
        # install flow
        inst = [ofp_parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS, actions)]
        mod = ofp_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
        datapath = msg.datapath
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser
        in_port = msg.match['in_port']  # get in port of the packet
 
        # add a flow entry for the packet
        match = ofp_parser.OFPMatch()
        actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_FLOOD)]
        self.add_flow(datapath, 1, match, actions)
 
        # to output the current packet. for install rules only output later packets
        out = ofp_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=in_port, actions=actions)
        # buffer id: locate the buffered packet
        datapath.send_msg(out)



运行结果如下:

(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:
    # 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    # ev.msg 是代表packet_in data structure对象
            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
            # dp.ofproto and dp.ofproto_parser are objects that represent the OpenFlow protocol that Ryu and the switch negotiated
            ofproto = datapath.ofproto
            parser = datapath.ofproto_parser
            in_port = msg.match['in_port']  # 获取源端口
    
            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
                # ignore lldp packet
                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
            # 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]:  # 如果目的地址存在于mac_to_port中
                out_port = self.mac_to_port[dpid][dst]
            # 否则,洪泛
            else:
                out_port = ofproto.OFPP_FLOOD  # OFPP_FLOOD标志表示应在所有端口发送数据包,即洪泛
    
            actions = [parser.OFPActionOutput(out_port)]
    
            # 下发流表避免下次触发 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
    
            # 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)
    
    
  2. a) 代码当中的mac_to_port的作用是什么?

    mac_to_port是mac地址映射到转发端口的字典。

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

    simple_switch.py : dpid = datapath.id
    simple_switch_13.py:dpid = format(datapath.id, "d").zfill(16)
    即simple_switch_13将dpid填充0至16位

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

    实现交换机以特性应答消息响应特性请求。

    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。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。

    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。

  3. 编程实现和ODL实验的一样的硬超时功能。
# 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


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

        # 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, 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)


四、实验总结

此次实验还是有一定的难度,但是万变不离其宗,这是在前序实验上的衍生。对RYU要有一定的了解与认识,实验自然就会进展得比较顺利。

在这过程中,我也遇到了一些问题。比如说在进行第一个实验“开启RYU”时,我始终无法有效开启,输入命令后会显示TypeError: cannot set 'is_timeout' attribute of immutable type 'TimeoutError'的语句,后续又报错为AttributeError:'module' has no attribute 'xxx'。在查找资料后,我发现是python版本不兼容的问题,在对一些文件进行修改后,终于解决了该问题。后来又遇到拓扑断开连接等问题,好在通过操作,最终解决了。

通过这一次的实验,我学到了ryu控制器的相关知识,根据实验内容验证了pox中hub模块功能,同时通过阅读源码,了解了 simple_switch_13流规则下发机制,进一步学习到了不同组件下,流表下发的操作。相信我会将这些知识融会贯通,更加精进自我。

posted @ 2022-10-16 17:55  忆然BILL  阅读(37)  评论(0编辑  收藏  举报