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。

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。
在lab6中创建L2Switch.py文件输入代码
`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)`

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）



创建L2212106658.py
输入代码
`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_features_handler(self,ev):
    datapath = ev.msg.datapath
    ofproto = datapath.ofproto
    ofp_parser = datapath.ofproto_parser

    match = ofp_parser.OFPMatch()
    actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,ofproto.OFPCML_NO_BUFFER)]

    self.add_flow(datapath,0,match,actions,"default flow entry")

def add_flow(self,datapath,priority,match,actions,remind_content):
    ofproto = datapath.ofproto
    ofp_parser = datapath.ofproto_parser

    inst = [ofp_parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                         actions)]

    mod = ofp_parser.OFPFlowMod(datapath=datapath,priority=priority,
                                match=match,instructions=inst);
    print("install to datapath,"+remind_content)
    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']

    print("get packet in, install flow entry,and lookback parket to datapath")

    match = ofp_parser.OFPMatch();
    actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_FLOOD)]

    self.add_flow(datapath,1,match,actions,"hub flow entry")

    out = ofp_parser.OFPPacketOut(datapath=datapath,buffer_id=msg.buffer_id,
                                        in_port=in_port,actions=actions)

    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，并回答下列问题：
a) 代码当中的mac_to_port的作用是什么？
b) simple_switch和simple_switch_13在dpid的输出上有何不同？
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
d) simple_switch_13是如何实现流规则下发的？
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？
编程实现和ODL实验的一样的硬超时功能。
（三）实验报告
总结：本次实验难度适中，前面部署期ryu和拓扑的时候如果顺序搞错，会导致后面L2Switch.py运行出现报错，顺序不能乱，本次是第一次使用ryu做实验，对比分析出ryu的L2Switch模块和POX的Hub模块都采用洪泛转发，其不同点在pox的Hub模块运行时查看流表，但是在ryu的L2Switch模块运行时无法查看到流表。