实验6：开源控制器实践——RYU
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
![]()
-
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。
![]()
![]()
不同：hub和L2Switch模块都是洪泛转发，但是运行L2Switch模块时无法查看下发的流表项，而hub模块可以
-
修改前查看流表项
![]()
-
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)
- 修改后查看流表项
![]()
（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
# 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): #继承ryu.base.app_manager类
#定义openflow版本
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
def __init__(self, *args, **kwargs):
super(SimpleSwitch13, self).__init__(*args, **kwargs) #继承父类初始化
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)
#当ofp_event.EventOFPSwitchFeatures这样的一个事件来临，且处于CONFIG_DISPATCHER这样一个阶段时，触发这个方法switch_features_handler(self, ev)
#其中ev参数是ofp_event.EventOFPSwitchFeatures的这样一个事件类的对象
#CONFIG_DISPATCHER代表协议版本确认后向交换机发送特性请求消息的阶段
#进入该阶段后，控制器自动发送特性请求消息，交换机接收后进行回复——EventOFPSwitchFeatures
def switch_features_handler(self, ev):
datapath = ev.msg.datapath #packet_in报文的datapath结构
ofproto = datapath.ofproto #OpenFlow协议数据结构的对象
parser = datapath.ofproto_parser #按照OPpenFlow解析的数据结构
# 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是一个列表，存放action list，在其中添加动作
actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
ofproto.OFPCML_NO_BUFFER)]
#1.datapath存储交换机的基本信息，如id，端口信息 2.priority越高，优先级就越高 3.match这里构造的parser.OFPMatch()代表没有匹配任何东西。
#4.actions这里构造的意思是发送给控制器。意思是，当没有匹配任何其它流表时，发送请求给控制器。（因为它的优先级最低是0）
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actions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packet_in事件
#代表交换机发送数据包给控制器引发的类，且一定是在MAIN_DISPATCHER这个阶段才触发
#MAIN_DISPATCHER代表特性消息接收到后到断开连接前的阶段
@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
#如果传输出错，直接丢弃
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，从事件中取出变量
msg = ev.msg #ev.msg是代表packet_in 数据结构对象
datapath = msg.datapath
#datapath.ofproto和datepath.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
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:
# ignore lldp packet
#如果接收到lldp包，就直接丢弃
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)
# learn a mac address to avoid FLOOD next time.
#学习mac地址以阻止下次继续洪泛
self.mac_to_port[dpid][src] = in_port #dpid-交换机id src-数据包源mac地址 in_port-交换机接收到包的端口
#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] #如果目的地址存在mac_to_port中，向交换机下发流表，并向相应的端口转发包
#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，即进行洪泛转发
actions = [parser.OFPActionOutput(out_port)]
# install a flow to avoid packet_in next time
#下发流表以避免下次触发packet_in事件
if out_port != ofproto.OFPP_FLOOD:
match = parser.OFPMatch(in_port=in_port, eth_dst=dst, eth_src=src)
# verify if we have a valid buffer_id, if yes avoid to send both
# flow_mod & packet_out
#验证是否拥有一个有效的buffer_id，如果是则避免同时发送flow_mod和packet_out
#如果msg.buffer_id不为None，即交换机把数据包存储在缓冲区，控制器下发parser.OFPPacketOut命令时，只需要指定buffer_id，并下发流表
#如果没有存储在缓冲区，控制器下发命令时，不仅要更改交换机流表项，又要把数据包的信息传给交换机让其转发
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)
- 回答下列问题：
a) 代码当中的mac_to_port的作用是什么？
保存（交换机id，mac地址）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？
在simple_switch_13.py中为dpid = format(datapath.id, "d").zfill(16)
在simple_switch.py中为dpid = datapath.id
在simple_switch_13.py中使用了zfill() 方法返回指定长度为16的字符串，原字符串右对齐，前面填充0；而simple_switch.py直接输出dpid
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
增加了实现交换机以特性应答消息响应特性请求功能
d) simple_switch_13是如何实现流规则下发的？
在触发PacketIn事件后，首先解析相关数据结构，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。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还有交换机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，如果没有就洪泛转发。如果学习过，则查看是否有buffer_id，如果有则在添加流时加上buffer_id指定缓冲区内的数据包，向交换机发送流表即可；如果没有buffer_id，控制器不仅需要向交换机发送流表，还要将数据包转交给交换机。
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
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)
-
运行结果
![]()
-
查看流表项
![]()
（三）实验报告
本次实验本身的难度与实验五相当，但是由于个人的原因使得难度飙升...
因为一开始不太熟悉ryu的各种功能和操作方法，在遇到问题的时候就明显慌了神。基础要求中需要打开网页展示图形界面时，我只能刷新出“Ryu Topology Viewer”字样，而并未出现任何图形，我还以为是ryu安装过程中产生瑕疵，这一点导致我陷入僵局，不断地查看ryu的各种操作指南尝试修复bug，花费了大量的时间而做无用功，当我退无可退准备重新安装ryu时我才发现虚拟机的网络设置出现了问题，无法从github进行clone操作...于是又花了很长时间查询虚拟机网络设置的修复指南，最后的最后才因为误点开了浏览器才发现是VMware的网络设置问题，恢复默认网络设置之后才终于可以正常进行实验...
后面的其他操作都比较顺利，在代码的注释和编写上花了相对多的时间去查阅文档资料。
通过这次实验，我明白了应该在实验前就做好充足的准备，不打无准备之仗，也意识到有一个好心态是多么重要，只要不放弃，一定天无绝人之路。在实验中，我明白了ryu与pox控制器之间的差异，在对ryu模块代码进行注释的过程中也加强了我对python代码的理解程度，同时对于其模块的运行过程有了相对深入的了解。
浙公网安备 33010602011771号