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
- 下载虚拟机软件Oracle VisualBox或VMware；
- 在虚拟机中安装Ubuntu 20.04 Desktop amd64，并完整安装Mininet；
三、实验要求
（一）基本要求
- 完成Ryu控制器的安装。
- 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，运行并使用 tcpdump 验证L2Switch，分析和POX的Hub模块有何不同。
- ryu --version 结果截图
- tcpdump的验证过程截图
- h1 ping h2
- h1 ping h3
（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：
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_typesclass 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 = {}#MAC位址表，用于存放MAC地址和端口之间的映射 @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) #为交换机的流表新增Table-miss Flow Entry项，用于封包在无法匹配到流表项后与之匹配 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)] #Entry的Instruction项，指定为output action中的动作，OFPIT_APPLY_ACTIONS表示动作立即执行 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) @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 #获取目的和源Mac地址 #获取OpenFlow交换器的标识ID dpid = format(datapath.id, "d").zfill(16) #Python zfill() 方法返回指定长度的字符串，原字符串右对齐，前面填充0 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]:#判断目的Mac地址是否存在于Mac位址表中，若不存在则进行洪泛 out_port = self.mac_to_port[dpid][dst] else: out_port = ofproto.OFPP_FLOOD actions = [parser.OFPActionOutput(out_port)] # install a flow to avoid packet_in next time #添加交换机中的流表项 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: self.add_flow(datapath, 1, match, actions, msg.buffer_id) return else: self.add_flow(datapath, 1, match, actions) data = None if msg.buffer_id == ofproto.OFP_NO_BUFFER: data = msg.data #将Packet-Out讯息对应的类别OFPPacketOut的实体发送给交换机 out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=in_port, actions=actions, data=data) datapath.send_msg(out)
- a) 代码当中的mac_to_port的作用是什么？
MAC位址表，用于存放MAC地址和端口之间的映射 - b) simple_switch和simple_switch_13在dpid的输出上有何不同？
simple_switch_13的dpid的输出为右对齐的16位字符串，在前面填充0，末尾加d。 - c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
为交换机的流表新增Table-miss Flow Entry项 - d) simple_switch_13是如何实现流规则下发的？
先判断以太网类型，若为LLDP类型则返回。再判断判断目的Mac地址是否存在于Mac位址表中，若不存在则进行洪泛。然后查看是否有buffer_id，如果有的话在添加流动作时加上buffer_id，最后向交换机发送流表。 - 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？
（三）实验总结
这次实验感觉难度还是挺大的。要看很多英文文档，很多专有名词都不太懂，同时也有些地方没能找到答案。像和pox中的hub比较，我没能确认下发的流表是否像各位同学写的那样能不能查看。进阶实验的e题如果看add_flow的话，我觉得应该是_packet_in_handler的优先级高。不过对这方面的知识确实没有那么深入地去了解，所以还是放空了。留下问题没解开真是挺遗憾的，在之后的学习中希望能找到解答。除此之外，刚开始实验的时候对Ryu的使用还是有点手足无措，也是在同学的帮助下才找到方向的。感觉做实验可能会遇到很多不会的，要多查多问才好。
