实验6：开源控制器实践——RYU
实验6：开源控制器实践——RYU
基本要求
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分析L2Switch和POX的Hub模块有何不同
Ryu的L2Switch模块和POX的Hub模块都采用洪泛转发的方式，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（如图）。
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修改过的L2032002227.py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) -
体现和验证修改的截图
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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：
- simple_switch_13.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. # 导包 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): OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION] # OpenFlow1.3版本（注意） 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 # 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)] # 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) # Packet_In # 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 # ev.msg 是代表packet_in data structure对象 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: # 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？
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？
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？
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？
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。
- SendRyuL2TimeOut.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)![]()
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- simple_switch_13.py
个人总结
- 实验难度：
本次的实验难度基本要求部分难度不大，只需要按照课件一步一步进行即可，但是进阶部分的难度较大，在还没有完全了解ryu的控制器原理的时候无从下手，而且很多问题很难通过搜索引擎完成相关知识的了解。 - 实验过程遇到的困难及解决办法:
- 困难：在搭建好拓扑的时候，运行ryu后，发现pingall全都ping不通。
- 解决办法：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。 - 困难：修改模块的时候发现程序运行错误。
- 解决办法：发现有些方法使用错误，参考同学的修正。
- 个人感想：
通过本次的实验，我明白了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，因此可以直接查看交换机流表项，而ryu要经过处理packet_in事件后，才向交换机下发流表。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（因为有一次我建立拓扑的时候协议的版本使用错了，但是我即时发现了），对于ryu的源码阅读也是比较累的，只能大概翻译，但总的来说还是学到了很多。
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