实验6：开源控制器实践——RYU
（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。
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。
Hub和L2Switch实现的都是洪泛发送ICMP报文，比如当h1 ping h2时，h1发送给h2的ICMP报文，h3也会收到，但L2Switch下发的流表无法查看，而Hub可以查看。
3.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.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER, CONFIG_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3
class L2102299222(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
def __init__(self, *args, **kwargs):
super(L2102299222, 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
match=ofp_parser.OFPMatch()
actions=[ofp_parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, ofproto.OFPCML_NO_BUFFER)]
self.add_flow(datapath, 0, match, actions)
def add_flow(self, datapath, priority, match, actions):
ofp = datapath.ofproto
ofp_parser = datapath.ofproto_parser
inst=[ofp_parser.OFPInstructionActions(ofp.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
dp = msg.datapath
ofp = dp.ofproto
ofp_parser = dp.ofproto_parser
in_port=msg.match['in_port']
match=ofp_parser.OFPMatch()
actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]
data = None
if msg.buffer_id == ofp.OFP_NO_BUFFER:
data = msg.data
self.add_flow(dp, 1, match, actions)
out = ofp_parser.OFPPacketOut(datapath=dp, buffer_id=msg.buffer_id, in_port=in_port, actions=actions, data = data)
dp.send_msg(out)
（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.
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): #继承了ryu.base.app_manager
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION] #OFP_VERSIONS指OpenFlow版本
def __init__(self, *args, **kwargs):
super(SimpleSwitch13, self).__init__(*args, **kwargs)
self.mac_to_port = {} #self.mac_to_port是一个保存(交换机id, mac地址)到转发端口的映射
#处理SwitchFeatures事件
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev):
datapath = ev.msg.datapath #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。
#add_flow()函数作用是增加流表，参数有datapath，priority, match, actions, buffer_id；
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)
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'] #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:#从接收到的Packet_In报文中取出各种信息，如果报文是lldp报文，忽略它。随后用此dpid（交换机id)初始化mac_to_port，并在日志打印此Packet_In的基本信息。
# ignore lldp packet
return
dst = eth.dst #获取目标端口
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.
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。
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]
else:
out_port = ofproto.OFPP_FLOOD #泛洪
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) #add_flow函数内部就已发送了Flow_mod报文。，后面不用send_msg()
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)
a) 代码当中的mac_to_port的作用是什么？
mac_to_port是一个保存(交换机id, mac地址)到转发端口的映射。
b) simple_switch和simple_switch_13在dpid的输出上有何不同？
simple_switch_13中dpid = format(datapath.id, "d").zfill(16)，即dpid的输出格式为用0在dpid前填充至总长度为16，而simple_switch中dpid = datapath.id，即直接输出dpid。
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
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？
当控制器处于CONFIG_DISPATCHER状态并且接受到FEATURE_REPLY报文时，执行switch_features_handler()函数。该函数的最后是add_flow添加流表项，当流表项匹配成功后应立即执行所规定的动作。如果此函数参数有buffer_id，那发送的Flow_Mod报文就带上buffer_id，若没有buffer_id，buffer_id就是None。最后，发出Flow_Mod报文，实现流规则的下发。
当控制器处于MAIN_DISPATCHER状态并且触发Packet_In事件时调用_packet_in_handler函数，然后从接收到的Packet_In报文中取出各种信息，用此dpid（交换机id)初始化mac_to_port，然后进行交换机自学习，取来往数据包的交换机id、源mac和入端口绑定来构造表。如果交换机发来的数据包没有buffer_id，则要回复一个Packet_out报文并带上原数据包的信息，实现流规则的下发。
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。因为switch_features_handler是在交换机处于协商版本并发送FEATURE-REQUEST报文状态时调用的，而_packet_in_handler是在已收到FEATURE-REPLY报文并发送SET-CONFIG报文时被调用的。
2.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 hardtimeout(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
def __init__(self, *args, **kwargs):
super(hardtimeout, 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)
运行结果：
交换机流表：
个人总结
本次实验我学到了部署RYU控制器，理解了RYU控制器实现软件定义的集线器原理和RYU控制器实现软件定义的交换机原理。本次实验对我来说难度较大，特别是代码阅读量较大，阅读起来较困难，花费了较多的时间。在运行L2Switch.py时，通过使用 tcpdump的结果没有发现L2Switch和POX的Hub模块有何不同，经过上网查询和对比代码后才发现二者的不同之处在于L2Switch不能查看到下发的流表。在编程修改L2Switch.py使之和POX的Hub模块的变得一致时遇到了各种错误，比如openflow的版本以及一些语法问题等，通过上网查询后修改代码得以完成。
浙公网安备 33010602011771号