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。
a) L2Switch代码
点击查看代码
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 h3
c）L2Switch和POX的Hub模块有何不同；
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。
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）
a）L2102299245代码
点击查看代码
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)
（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：
- 代码注释
点击查看代码
# 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 #app的基类
from ryu.controller import ofp_event #OpenFlow的事件
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3 #应用的是OpenFlow1.3协议
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet #引入了基本的网络协议
from ryu.lib.packet import ether_types
class SimpleSwitch13(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION] # 定义openflow版本
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
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER) #@set_ev_cls是一个装饰器，当参数表示的事件触发后会执行下面的函数,其事件名称是由接收到的报文类型来命名的，名字为Event+报文类型
#起到了事件响应的功能
#当接收到feature-reply报文后执行下面的函数下发table-miss表项
def switch_features_handler(self, ev):
datapath = ev.msg.datapath #获取数据通路即交换机
ofproto = datapath.ofproto #获取数据通路的协议
parser = datapath.ofproto_parser #对协议进行解析
# 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() #全匹配
actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
ofproto.OFPCML_NO_BUFFER)]
#设置table-miss表项的动作：将数据包发至控制器
self.add_flow(datapath, 0, match, actions)
#将0优先级、全匹配、动作为“将数据包发至控制器”的table-miss表项下发给交换机。
#这样以后交换机不知道咋处理的数据包会自动发至控制器。
def add_flow(self, datapath, priority, match, actions, buffer_id=None):
#下发流表项
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)
#如果此函数参数有buffer_id(就是交换机发送来的数据包有buffer_id，即交换机有缓存），那发送的Flow_Mod报文就带上buffer_id，若没有buffer_id，buffer_id就是None
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
#在MAIN_DISPATCHER阶段碰到EventOFPPacketIn事件的时候调用_packet_in_handler函数。
#即控制器收到数据包的时候执行下面的函数。
#控制器什么时候会收到数据包呢：就是交换机现有的流表项无法与数据包匹配，利用table-miss表项交给控制器处理。
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) #传输出错，打印debug信息
msg = ev.msg
datapath = msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
in_port = msg.match['in_port']
#此时能进入这里的都是不知道该被咋处理的数据包。
#记录下数据包从哪个端口进来
#提取数据包的信息
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 #获取数据包的目的MAC地址
src = eth.src #获取数据包的源MAC地址
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)
#从接收到的Packet_In报文中取出各种信息，如果报文时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。
# learn a mac address to avoid FLOOD next time.交换机自学习，类似传统二层交换机的MAC地址表自学习，取来往数据包的交换机id、源mac和入端口绑定来构造表。
#设置该交换机的MAC-端口对。
#即将数据包的源MAC地址与进入的端口相对应，完成了学习。
self.mac_to_port[dpid][src] = in_port
#如果知道目的MAC地址与哪个出的端口相对应，那么就直接转发。
if dst in self.mac_to_port[dpid]:
out_port = self.mac_to_port[dpid][dst]
#否则需要泛洪寻找出的端口。
else:
out_port = ofproto.OFPP_FLOOD
#给流表项赋予动作：遇到该目的MAC地址的时候从这个端口转发。
actions = [parser.OFPActionOutput(out_port)]
# install a flow to avoid packet_in next time 创建流表项来避免再次收到Packet_in报文
if out_port != ofproto.OFPP_FLOOD:
#创建匹配域：以后再遇到这种情况就知道从哪个端口转发了
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
#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。
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 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)
datapath.send_msg(out)
-
回答问题
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？
- 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？
- 实现了事件响应的功能，交换机不知道咋处理的数据包会自动发至控制器。
d) simple_switch_13是如何实现流规则下发的？
- 碰到EventOFPPacketIn事件的时候调用_packet_in_handler函数，提取数据包的信息，从接收到的Packet_In报文中取出各种信息，如果报文时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。将数据包的源MAC地址与进入的端口相对应，完成交换机自学习。如果知道目的MAC地址与哪个出的端口相对应，那么就直接转发，如果没有就洪泛转发查看是否有buffer_id，如果有则在添加流时加上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优先级高于_packet_in_handler
- switch_features_handler在接收到feature-reply后执行
- _packet_in_handler在接收到PacketIn后执行
2.编程实现和ODL实验的一样的硬超时功能。
a）硬超时代码
点击查看代码
# 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, 65535, 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, 65535, 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)
b）结果验证
（三）参考资料
https://blog.csdn.net/weixin_44480014/article/details/123258955
https://www.cnblogs.com/kl107/p/13138568.html
（四）个人总结
1.这次的实验基础部分第一部分一如既往按照pdf上的实验指引即可完成，L2Switch的代码老师亦有提供，实验结果验证较为简单，第二部分通过查找资料和查看源码自己动手试验得以运行成功；
2.进阶部分较难，代码注释方面有幸查找到上述参考资料，内容介绍的很详细，得以理解源码中每一步的具体作用，硬超时相比起来简单许多，在理解源码后，添加新的优先级流规则即可实现。
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