实验6：开源控制器实践——RYU
（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
- L2Switch.py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 h2(观察到h2，h3都接收到数据包)
- h1 ping h3(观察到h2，h3都接收到数据包)
-
分析L2Switch和POX的Hub模块有何不同
在连接ryu控制器，启动L2Switch模块后查看下发流表
在连接pox控制器，启动Hub模块后查看下发流表
- 结论：
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。
- 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）
L2032002240.py
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)
- 运行L2032002126.py
- 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)a) 代码当中的mac_to_port的作用是什么？
答：保存mac地址到交换机端口的映射，可用于交换机自学习
b) simple_switch和simple_switch_13在dpid的输出上有何不同？
#simple_switch.py dpid = datapath.id ################################# #simple_switch_13.py dpid = format(datapath.id, "d").zfill(16)答：simple_switch直接输出dpid，而simple_switch_13则在dpid前端填充0直至满16位
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
答：实现了交换机以特性应答消息来响应特性请求的功能
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。若以太网类型是LLDP类型，则不予处理。如果不是，则获取源端口的目的端口和交换机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，则在添加流表信息时加上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下发流表的优先级比_packet_in_handler的优先级高。
-
编程实现和ODL实验的一样的硬超时功能。
L2_TimeOut.py
# 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, 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)
四、个人总结
实验难度:
本次实验的基本要求部分难度不大，在完成进阶要求的源码注释过程中，明显感觉到困难。原因有几点：首先，一开始对RYU的工作原理并没有十分了解；同时，源码中使用了许多RYU中定义的数据结构，阅读时根本没有一点的基础概念。基于此，我使用搜索引擎，查找了RYU使用的相应数据结构，并了解了其中各个参数的基本含义，再重新阅读源码，同时，在网上查找RYU工作原理的说明材料，才最终成功完成源码的注释。这次实验相比上次难度更大，对源码分析和对openflow协议的理解有一定的要求，但是做完实验后感受到收获颇多，学习到了更多的知识。
实验过程遇到的困难及解决办法:
- 困难：在搭建好网络拓扑，运行 ryu 后，使用命令
h1 ping h2发现 ping 不通。
解决方法：在分析后得知，应该先执行命令ryu-manager L2Switch.py运行 ryu，再建立拓扑。
- 命令行没找对位置，运行L2Switch.py时试了半天才发现路径不对，最后改了路径成功了
个人感想:
通过ryu的使用，明白了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。
这次基本要求倒是中规中矩，没什么感想。而进阶要求难度不小，有些问题需要真正去阅读代码以及查一些资料相结合才能搞明白，花了不少时间，看来如何高效使用搜索引擎也是一门必修课，还有就是发现注释很重要。通过本次实验，也使得我对RYU的控制机制有了深入的认识，同时也对SDN有了更深刻的认识。总之，收获颇丰！
标签：控制器,self,parser,datapath,msg,开源,ofproto,RYU,port From： https://www.cnblogs.com/zxxsss/p/16801269.html