Ubuntu 20.04 Desktop amd64
h1 ping
h1 ping h3
可以看出无论是h1 ping h2还是h1 ping h3,h2和h3都能同时接收到数据包。结果验证Hub模块的作用:Hub模块采用洪泛转发,每个交换机上都安装泛洪通配符规则,将数据包广播转发,此时交换机等效于集线器。所以在ping某个主机时,会在另一台主机上接收到。
本次实验操作复杂但代码不复杂,也是由于pox是第一次接触,所以会遇到到一些问题在实验过程中,Hub模块创建拓扑时,由于POX目前仅支持OpenFlow 1.0,所以需实验OpenFlow10;之后开启POX,需在pox下才可以开启;实验过程中发现无论是h1 ping h2或者是h1 ping h3,h2和h3都可以抓包。在做第二题的时候可能会遇到pox报error而不是debug,这是应为第一题的pox没关闭导致的,所以需要命令关闭或重启虚拟机,在实验过程中应为pox文件带锁所以权限不够可能需要修改权限。ping的过程中实现断开功能需要先发送先发送SendFlowInSingle3然后关闭在发送SendPoxHardTimeOut。
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。
下载虚拟机软件Oracle VisualBox或VMware;
在虚拟机中安装Ubuntu 20.04 Desktop amd64,并完整安装Mininet;
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。
ryu-manager gui_topology.py --observe-links
启动控制器
使用命令sudo mn --topo=single,3 --mac --cOntroller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow10
搭建上述拓扑
2.通过Ryu的图形界面查看网络拓扑
3.阅读Ryu文档的The First Application一节,运行并使用 tcpdump 验证L2Switch,分析和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)
ryu-manager L2Switch.py
重新创建拓扑
利用mininet的xterm开启h1,h2,h3的命令行终端,并在h2和h3使用开启抓包(抓取eth0端口)
由图可见,h1 ping h2时h3也能收到数据包,h1 ping h3时h2也能收到数据包,说明L2Switch模块的功能同hub模块:为每一个交换机建立通配的洪泛规则,让交换机拥有集线器的功能
分析和POX的Hub模块有何不同
1.查看下发流表dpctl dump-flows
2.运行ryuryu-manager L2Switch.py
3.运行pox(Hub模块)./pox.py log.level --DEBUG forwarding.hub
无法查看L2Switch下发的流表
而hub模块下发的流表可以查看
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)
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. a) 代码当中的mac_to_port的作用是什么? 实验很难,为L2Switch添加流表的操作很容易出现问题,经过查阅技术博客、文档等资料才解决。 ryu与pox转发的流表的区别:pox是直接向交换机发送流表项的,而ryu要经过处理packet_in事件后,才向交换机下发流表; RYU工作原理: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
#
# 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):
# 指定OpenFlow版本为1.3
OFP_VERSIOnS= [ofproto_v1_3.OFP_VERSION]
def __init__(self, *args, **kwargs):
super(SimpleSwitch13, self).__init__(*args, **kwargs)
self.mac_to_port = {} # 一个保存(交换机id, mac地址)到转发端口的字典
# 处理EventOFPSwitchFeatures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:流表项匹配,OFPMatch():不匹配任何信息
actiOns= [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
ofproto.OFPCML_NO_BUFFER)]
self.add_flow(datapath, 0, match, actions)#添加流表项
# 添加流表
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
# 包装action
inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
actions)]
# 判断是否有buffer_id,生成相应的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mod
datapath.send_msg(mod)
# 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.msg_len, ev.msg.total_len)
# 获取Packet_In报文中的各种信息:包信息,交换机信息,协议等等
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]
# 忽略LLDP类型
if eth.ethertype == ether_types.ETH_TYPE_LLDP:
# ignore lldp packet
return
# 获取源端口,目的端口
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)
# 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
# 在字典中查找目的mac地址是否有对应的出端口
if dst in self.mac_to_port[dpid]:
out_port = self.mac_to_port[dpid][dst]
# 没有就进行洪泛
else:
out_port = ofproto.OFPP_FLOOD
actiOns= [parser.OFPActionOutput(out_port)]
# 下发流表处理后续包,不再触发 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)
答: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?
答: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?
答: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?
答: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?
答:switch_features_handler下发流表的优先级高于_packet_in_handler。(三)实验报告