实验6：开源控制器实践——RYU
实验6：开源控制器实践——RYU
一、实验目的
- 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。
二、实验环境
Ubuntu 20.04 Desktop amd64
三、实验要求
（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。
启动控制器，利用Web图形界面查看网络拓扑ryu-manager ryu/ryu/app/gui_topology/gui_topology.py --observe-links
- 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。
(1)建立拓扑：sudo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow10
(2)运行Ryu：ryu-manager L2Switch.py ,验证L2Switch
h1 ping h2：h2，h3都接收到icmp报文
h1 ping h3：h2，h3都接收到icmp报文
L2Switch和POX的Hub模块有何不同？
L2Switch代码
1 from ryu.base import app_manager 2 from ryu.controller import ofp_event 3 from ryu.controller.handler import MAIN_DISPATCHER 4 from ryu.controller.handler import set_ev_cls 5 from ryu.ofproto import ofproto_v1_0 6 7 class L2Switch(app_manager.RyuApp): 8 OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION] 9 10 def __init__(self, *args, **kwargs): 11 super(L2Switch, self).__init__(*args, **kwargs) 12 13 @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER) 14 def packet_in_handler(self, ev): 15 msg = ev.msg 16 dp = msg.datapath 17 ofp = dp.ofproto 18 ofp_parser = dp.ofproto_parser 19 20 actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)] 21 22 data = None 23 if msg.buffer_id == ofp.OFP_NO_BUFFER: 24 data = msg.data 25 26 out = ofp_parser.OFPPacketOut( 27 datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port, 28 actions=actions, data = data) 29 dp.send_msg(out)
L2Switch模块
POX的Hub模块
所以可得 Ryu的L2Switch模块和POX的Hub模块都是采用洪泛转发，但是不同之处是：可以查看Hub模块下发的流表，无法查看L2Switch模块下发的流表。
-
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）
1 from ryu.base import app_manager 2 from ryu.ofproto import ofproto_v1_3 3 from ryu.controller import ofp_event 4 from ryu.controller.handler import MAIN_DISPATCHER, CONFIG_DISPATCHER 5 from ryu.controller.handler import set_ev_cls 6 7 class hub(app_manager.RyuApp): 8 OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION] 9 10 def __init__(self, *args, **kwargs): 11 super(hub, self).__init__(*args, **kwargs) 12 13 @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER) 14 def switch_feathers_handler(self, ev): 15 datapath = ev.msg.datapath 16 ofproto = datapath.ofproto 17 ofp_parser = datapath.ofproto_parser 18 19 # install flow table-miss flow entry 20 match = ofp_parser.OFPMatch() 21 actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, ofproto.OFPCML_NO_BUFFER)] 22 # 1\OUTPUT PORT, 2\BUFF IN SWITCH? 23 self.add_flow(datapath, 0, match, actions) 24 25 def add_flow(self, datapath, priority, match, actions): 26 # 1\ datapath for the switch, 2\priority for flow entry, 3\match field, 4\action for packet 27 ofproto = datapath.ofproto 28 ofp_parser = datapath.ofproto_parser 29 # install flow 30 inst = [ofp_parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS, actions)] 31 mod = ofp_parser.OFPFlowMod(datapath=datapath, priority=priority, match=match, instructions=inst) 32 datapath.send_msg(mod) 33 34 @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER) 35 def packet_in_handler(self, ev): 36 msg = ev.msg 37 datapath = msg.datapath 38 ofproto = datapath.ofproto 39 ofp_parser = datapath.ofproto_parser 40 in_port = msg.match['in_port'] # get in port of the packet 41 42 # add a flow entry for the packet 43 match = ofp_parser.OFPMatch() 44 actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_FLOOD)] 45 self.add_flow(datapath, 1, match, actions) 46 47 # to output the current packet. for install rules only output later packets 48 out = ofp_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=in_port, actions=actions) 49 # buffer id: locate the buffered packet 50 datapath.send_msg(out)
（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，
1 # Copyright (C) 2011 Nippon Telegraph and Telephone Corporation. 2 # 3 # Licensed under the Apache License, Version 2.0 (the "License"); 4 # you may not use this file except in compliance with the License. 5 # You may obtain a copy of the License at 6 # 7 # http://www.apache.org/licenses/LICENSE-2.0 8 # 9 # Unless required by applicable law or agreed to in writing, software 10 # distributed under the License is distributed on an "AS IS" BASIS, 11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 12 # implied. 13 # See the License for the specific language governing permissions and 14 # limitations under the License. 15 16 from ryu.base import app_manager 17 from ryu.controller import ofp_event 18 from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER 19 from ryu.controller.handler import set_ev_cls 20 from ryu.ofproto import ofproto_v1_3 21 from ryu.lib.packet import packet 22 from ryu.lib.packet import ethernet 23 from ryu.lib.packet import ether_types 24 25 26 class SimpleSwitch13(app_manager.RyuApp): # 继承 27 # 定义openflow版本 28 OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION] 29 30 def __init__(self, *args, **kwargs): 31 super(SimpleSwitch13, self).__init__(*args, **kwargs) # py2.7版本的书写方式 32 self.mac_to_port = {} # 用字典存储MAC地址表 33 34 35 # 监听事件，参数是事件名和状态 36 @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER) 37 # 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 38 def switch_features_handler(self, ev): 39 datapath = ev.msg.datapath # datapath可认为是交换机n上发生的事 40 ofproto = datapath.ofproto # openflow协议的版本 41 parser = datapath.ofproto_parser # openflow协议的解析器 42 43 # install table-miss flow entry 44 # 45 # We specify NO BUFFER to max_len of the output action due to 46 # OVS bug. At this moment, if we specify a lesser number, e.g., 47 # 128, OVS will send Packet-In with invalid buffer_id and 48 # truncated packet data. In that case, we cannot output packets 49 # correctly. The bug has been fixed in OVS v2.1.0. 50 match = parser.OFPMatch() # 空的，为了匹配所有的封包 51 # actions是为了转送到控制器端口，参数里是发往控制器端口，不进行缓存 52 actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, 53 ofproto.OFPCML_NO_BUFFER)] 54 self.add_flow(datapath, 0, match, actions) # 添加流表 55 56 def add_flow(self, datapath, priority, match, actions, buffer_id=None): 57 # 获取交换机信息 58 ofproto = datapath.ofproto 59 parser = datapath.ofproto_parser 60 61 # inst是instruction的缩写，第一个参数是马上执行动作，第二个参数是执行动作的对象 62 inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS, 63 actions)] 64 # 判断是否存在buffer_id，并生成mod对象 65 if buffer_id: 66 mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id, 67 priority=priority, match=match, 68 instructions=inst) 69 else: 70 mod = parser.OFPFlowMod(datapath=datapath, priority=priority, 71 match=match, instructions=inst) 72 datapath.send_msg(mod) # 发送操作指令给交换机 73 74 75 # 监听packet_in消息是否被触发，用来处理未知目的地的封包 76 @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER) 77 def _packet_in_handler(self, ev): 78 # If you hit this you might want to increase 79 # the "miss_send_length" of your switch 80 if ev.msg.msg_len < ev.msg.total_len: 81 self.logger.debug("packet truncated: only %s of %s bytes", 82 ev.msg.msg_len, ev.msg.total_len) 83 msg = ev.msg 84 datapath = msg.datapath 85 ofproto = datapath.ofproto 86 parser = datapath.ofproto_parser 87 in_port = msg.match['in_port'] # 获取源端口 88 89 pkt = packet.Packet(msg.data) 90 eth = pkt.get_protocols(ethernet.ethernet)[0] 91 92 if eth.ethertype == ether_types.ETH_TYPE_LLDP: 93 # ignore lldp packet 94 return 95 dst = eth.dst # 获取目的端口 96 src = eth.src # 获取源端口 97 98 99 dpid = format(datapath.id, "d").zfill(16) # MAC地址表和每个交换机之间的识别，用dpid确认 100 self.mac_to_port.setdefault(dpid, {}) 101 102 # 打印日志信息 103 self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port) 104 105 # learn a mac address to avoid FLOOD next time. 106 self.mac_to_port[dpid][src] = in_port # 学习MAC地址，避免下次泛洪 107 108 if dst in self.mac_to_port[dpid]: # 如果目标Mac地址已经被学习了，决定哪个从哪个端口发送数据包,否则范洪 109 out_port = self.mac_to_port[dpid][dst] 110 else: 111 out_port = ofproto.OFPP_FLOOD 112 113 actions = [parser.OFPActionOutput(out_port)] 114 115 # 下发流表避免下次触发 packet in 事件 116 # install a flow to avoid packet_in next time 117 if out_port != ofproto.OFPP_FLOOD: 118 match = parser.OFPMatch(in_port=in_port, eth_dst=dst, eth_src=src) 119 # verify if we have a valid buffer_id, if yes avoid to send both 120 # flow_mod & packet_out 121 if msg.buffer_id != ofproto.OFP_NO_BUFFER: 122 self.add_flow(datapath, 1, match, actions, msg.buffer_id) 123 return 124 else: 125 self.add_flow(datapath, 1, match, actions) 126 data = None 127 if msg.buffer_id == ofproto.OFP_NO_BUFFER: 128 data = msg.data 129 # 构造一个pack_out消息然后发送 130 out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, 131 in_port=in_port, actions=actions, data=data) 132 datapath.send_msg(out)
并回答下列问题：
a)代码当中的mac_to_port的作用是什么？
答：mac_to_port的作用是保存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对dpid进行了格式化，并填充为16位数字，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：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。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。
1 from ryu.base import app_manager 2 from ryu.controller import ofp_event 3 from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER 4 from ryu.controller.handler import set_ev_cls 5 from ryu.ofproto import ofproto_v1_3 6 from ryu.lib.packet import packet 7 from ryu.lib.packet import ethernet 8 from ryu.lib.packet import ether_types 9 10 11 class SimpleSwitch13(app_manager.RyuApp): 12 OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION] 13 14 def __init__(self, *args, **kwargs): 15 super(SimpleSwitch13, self).__init__(*args, **kwargs) 16 self.mac_to_port = {} 17 18 @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER) 19 def switch_features_handler(self, ev): 20 datapath = ev.msg.datapath 21 ofproto = datapath.ofproto 22 parser = datapath.ofproto_parser 23 24 match = parser.OFPMatch() 25 actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, 26 ofproto.OFPCML_NO_BUFFER)] 27 self.add_flow(datapath, 0, match, actions) 28 29 def add_flow(self, datapath, priority, match, actions, buffer_id=None, hard_timeout=0): 30 ofproto = datapath.ofproto 31 parser = datapath.ofproto_parser 32 33 inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS, 34 actions)] 35 if buffer_id: 36 mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id, 37 priority=priority, match=match, 38 instructions=inst, hard_timeout=hard_timeout) 39 else: 40 mod = parser.OFPFlowMod(datapath=datapath, priority=priority, 41 match=match, instructions=inst, hard_timeout=hard_timeout) 42 datapath.send_msg(mod) 43 44 @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER) 45 def _packet_in_handler(self, ev): 46 # If you hit this you might want to increase 47 # the "miss_send_length" of your switch 48 if ev.msg.msg_len < ev.msg.total_len: 49 self.logger.debug("packet truncated: only %s of %s bytes", 50 ev.msg.msg_len, ev.msg.total_len) 51 msg = ev.msg 52 datapath = msg.datapath 53 ofproto = datapath.ofproto 54 parser = datapath.ofproto_parser 55 in_port = msg.match['in_port'] 56 57 pkt = packet.Packet(msg.data) 58 eth = pkt.get_protocols(ethernet.ethernet)[0] 59 60 if eth.ethertype == ether_types.ETH_TYPE_LLDP: 61 # ignore lldp packet 62 return 63 dst = eth.dst 64 src = eth.src 65 66 dpid = format(datapath.id, "d").zfill(16) 67 self.mac_to_port.setdefault(dpid, {}) 68 69 self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port) 70 71 # learn a mac address to avoid FLOOD next time. 72 self.mac_to_port[dpid][src] = in_port 73 74 if dst in self.mac_to_port[dpid]: 75 out_port = self.mac_to_port[dpid][dst] 76 else: 77 out_port = ofproto.OFPP_FLOOD 78 79 actions = [parser.OFPActionOutput(out_port)]\ 80 81 actions_timeout=[] 82 83 # install a flow to avoid packet_in next time 84 if out_port != ofproto.OFPP_FLOOD: 85 match = parser.OFPMatch(in_port=in_port, eth_dst=dst, eth_src=src) 86 # verify if we have a valid buffer_id, if yes avoid to send both 87 # flow_mod & packet_out 88 hard_timeout=10 89 if msg.buffer_id != ofproto.OFP_NO_BUFFER: 90 self.add_flow(datapath, 2, match,actions_timeout, msg.buffer_id,hard_timeout=10) 91 self.add_flow(datapath, 1, match, actions, msg.buffer_id) 92 return 93 else: 94 self.add_flow(datapath, 2, match, actions_timeout, hard_timeout=10) 95 self.add_flow(datapath, 1, match, actions) 96 data = None 97 if msg.buffer_id == ofproto.OFP_NO_BUFFER: 98 data = msg.data 99 100 out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, 101 in_port=in_port, actions=actions, data=data) 102 datapath.send_msg(out)
（三）个人总结
在本次实验中，我已经能够独立部署RYU控制器；也大概能能够理解RYU控制器实现软件定义的集线器和交换机原理，不仅加深了理论知识，还提升了上机实践能力。但是在实验过程中，还是出现了很多问题，比如在lab6下面运行ryu-manager L2Switch.py后，拓扑图执行pingall操作却ping不通，最后，在同学的帮助下才发现需要关闭利用Web图形界面查看网络拓扑的控制器，因为这两个命令可能有冲突。对我而言，这次的实验难度还是挺大的，主要是要对比分析L2Switch和POX的Hub模块的不同，代码一直报错，最后在建立拓扑图的时候没有加上协议，才成功运行出来，所以对于理论还是要加强学习，这样实验才会更加顺利！
