一、实验目的
1.能够独立部署RYU控制器
2.能够理解RYU控制器实现软件定义的集线器原理
3.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
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。
2.建立拓扑并连接RYU控制器
3.通过Ryu的图形界面查看网络拓扑
启动ryu控制器后，在浏览器中输入地址http://127.0.0.1:8080即可打开ryu的图形界面
4.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。
L2Switch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)
(1)运行并使用 tcpdump 验证L2Switch
h1 ping h2
h1 ping h3
(2)分析和POX的Hub模块有何不同
Hub和L2Switch模块都是洪泛转发，但L2Switch模块下发的流表无法查看，而Hub模块下发的流表可以查看
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）
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)
查看流表信息：
四.个人总结
这次实验总体来说比较难，在基础部分遇到运行L2xxxx.py,之后仍然ping不同的情况，先开启控制器，之后运行，再建拓扑就可以了。
遇到的问题：在执行L2Switch.py的程序时，不能通过查看流表查询到空表而是出现有信息的流表。经查阅分析，此次的流表是因为上一次实验所构建的拓扑残留下的流表，使用命令dpctl del-flows删除流表，再重新操作后才实现。