实验6:开源控制器实践——RYU

一、实验目的

能够独立部署RYU控制器;
能够理解RYU控制器实现软件定义的集线器原理;
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

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。

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。

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

分析L2Switch和POX的Hub模块有何不同

虽然RYU的L2Switch模块和POX的Hub模块都是洪泛转发。但pox的Hub模块是下发流表到交换机,然后交换机直接根据流表进行洪泛转发,ryu的L2Switch模块运行时不下发对应的转发流表,而是将包发送给控制器,由控制器利用packet-out指定为洪泛转发。

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)

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)

查看流表

(二)进阶要求

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:

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.

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]	 # OpenFlow1.3版本

   def __init__(self, *args, **kwargs):
       super(SimpleSwitch13, self).__init__(*args, **kwargs)
       self.mac_to_port = {}	# 保存(交换机id, mac地址)到转发端口的字典

   # 处理SwitchFeatures事件
   @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
   def switch_features_handler(self, ev):
       datapath = ev.msg.datapath	# 存储交换机的信息
       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,这里OFPMatch()指不匹配任何信息
       actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                         ofproto.OFPCML_NO_BUFFER)]	# actions是动作,表示匹配成功不缓存数据包并发送给控制器
       self.add_flow(datapath, 0, match, actions)	# add_flow是添加流表项的函数,我们可以从add_flow的函数中看到其调用了send_msg(mod),因此本函数的目的即为下发流表。

   # 增加流表项
   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)
       
       
   # 说明控制器在MAIN_DISPATCHER状态并且触发Packet_In事件时调用_packet_in_handler函数
   @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:	# 传输出错,打印debug信息
           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	# 目的端口
       src = eth.src	# 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)

       # learn a mac address to avoid FLOOD next time.
       self.mac_to_port[dpid][src] = in_port		# 交换机自学习,取来往数据包的交换机id、源mac和入端口绑定来构造表。

   # 查看是否已经学习过该目的mac地址
       if dst in self.mac_to_port[dpid]:	# 若在表中找到出端口信息,指示出端口
           out_port = self.mac_to_port[dpid][dst]
       # 否则,洪泛    
       else:
           out_port = ofproto.OFPP_FLOOD

       actions = [parser.OFPActionOutput(out_port)]

       # 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:	# 有buffer_id,带上buffer_id,然后只发送Flow_mod报文,因为交换机已经有缓存数据包,就不需要发送packet_out报文
               self.add_flow(datapath, 1, match, actions, msg.buffer_id)
               return
           else:
               self.add_flow(datapath, 1, match, actions)	# 若没有buffer_id,发送的Flow_Mod报文就无需要带上buffer_id,但是下一步要再发送一个Packet_out报文带上原数据包信息。
       data = None
       if msg.buffer_id == ofproto.OFP_NO_BUFFER:
           data = msg.data

   	# 发送Packet_out数据包 带上交换机发来的数据包的信息
       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)


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。

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

simple_switch直接输出dpid,simple_switch_13会在不满16位的dpid前补0直到满16位

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

switch_features_handler函数是新增缺失流表项到流表中,当封包没有匹配到流表时,就触发packet_in

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、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,如果没有就洪泛转发。如果学习过该mac地址,则查看是否有buffer_id,如果有则在添加流动作时加上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下发流表的优先级高

编程实现和ODL实验的一样的硬超时功能

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)

(三)心得体会

通过本次实验,了解到了ryu控制器的使用,学习了通过自定义python脚本来下发流表实现相应功能,认识到了和pox模块的异同。

posted @ 2022-10-18 23:05  xcua  阅读(13)  评论(0编辑  收藏  举报