SDN-实验6：开源控制器实践-RYU

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，通过Ryu的图形界面查看网络拓扑。

搭建拓扑

连接ryu控制器

通过Ryu的图形界面查看网络拓扑,在浏览器中输入127.0.0.1:8080

2.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。
编写L2Switch.py
`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)`

运行L2Switch.py

重新构建拓扑，并对h2、h3节点进行抓包

h1 ping h2

h1 ping h3

查看流表

pox下查看拓扑流表

由此可知，ryu下查不到流表，而在pox下可以查到流表
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）
L2_212006137.py
`from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3

class L2Switch(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

def __init__(self, *args, **kwargs):
    super(L2Switch, 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
    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):
    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)
    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):
    msg = ev.msg
    dp = msg.datapath
    ofp = dp.ofproto
    ofp_parser = dp.ofproto_parser
    in_port = msg.match['in_port']

    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=in_port,
        actions=actions, data = data)
    dp.send_msg(out)

`
运行L2_212006137.py
ryu-manager L2_212006137.py
创建拓扑
sudo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow13
测试
pingall
查看流表
dpctl dump-flows
总结：本次实验考察了我们对于ryu的使用，通过本次实验，能了解到了ryu控制器的工作原理，以及与pox控制器的区别。