一：實驗目的
（一）案例目的
（二）實驗內容
（三）網絡拓撲結構
二：OpenFlow流表實驗准備
（一）使用Python設置網絡拓撲 --- tree_topo.py
from mininet.topo import Topo from mininet.net import Mininet from mininet.node import RemoteController from mininet.link import TCLink from mininet.util import dumpNodeConnections class MyTopo(Topo): def __init__(self): super(MyTopo,self).__init__() # add host Host1 = self.addHost('h1') Host2 = self.addHost('h2') Host3 = self.addHost('h3') switch1 = self.addSwitch('s1') switch2 = self.addSwitch('s2') self.addLink(Host1,switch1) self.addLink(Host2,switch1) self.addLink(Host3,switch2) self.addLink(switch1,switch2) topos = {"mytopo":(lambda:MyTopo())}
（二）啟動遠程Ryu控制器
ryu-manager simple_switch.py 注意，該控制器py文件在app目錄下
# 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. """ An OpenFlow 1.0 L2 learning switch implementation. """ 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 from ryu.lib.mac import haddr_to_bin from ryu.lib.packet import packet from ryu.lib.packet import ethernet from ryu.lib.packet import ether_types class SimpleSwitch(app_manager.RyuApp): 不同與之前的Ryu實驗，這里面沒有在交換機初始連接時下發默認流表...待思考 OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION] def __init__(self, *args, **kwargs): super(SimpleSwitch, self).__init__(*args, **kwargs) self.mac_to_port = {} def add_flow(self, datapath, in_port, dst, src, actions): 下發流表 ofproto = datapath.ofproto match = datapath.ofproto_parser.OFPMatch( in_port=in_port, dl_dst=haddr_to_bin(dst), dl_src=haddr_to_bin(src)) mod = datapath.ofproto_parser.OFPFlowMod( datapath=datapath, match=match, cookie=0, command=ofproto.OFPFC_ADD, idle_timeout=0, hard_timeout=0, priority=ofproto.OFP_DEFAULT_PRIORITY, flags=ofproto.OFPFF_SEND_FLOW_REM, actions=actions) datapath.send_msg(mod) @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER) def _packet_in_handler(self, ev): 交換機向控制器發送數據 msg = ev.msg datapath = msg.datapath ofproto = datapath.ofproto pkt = packet.Packet(msg.data) eth = pkt.get_protocol(ethernet.ethernet) if eth.ethertype == ether_types.ETH_TYPE_LLDP: # ignore lldp packet return dst = eth.dst src = eth.src dpid = datapath.id self.mac_to_port.setdefault(dpid, {}) self.logger.info("packet in %s %s %s %s", dpid, src, dst, msg.in_port) # learn a mac address to avoid FLOOD next time. self.mac_to_port[dpid][src] = msg.in_port if dst in self.mac_to_port[dpid]: out_port = self.mac_to_port[dpid][dst] else: out_port = ofproto.OFPP_FLOOD actions = [datapath.ofproto_parser.OFPActionOutput(out_port)] # install a flow to avoid packet_in next time if out_port != ofproto.OFPP_FLOOD: self.add_flow(datapath, msg.in_port, dst, src, actions) data = None if msg.buffer_id == ofproto.OFP_NO_BUFFER: data = msg.data out = datapath.ofproto_parser.OFPPacketOut( datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port, actions=actions, data=data) datapath.send_msg(out) @set_ev_cls(ofp_event.EventOFPPortStatus, MAIN_DISPATCHER) def _port_status_handler(self, ev): msg = ev.msg reason = msg.reason port_no = msg.desc.port_no ofproto = msg.datapath.ofproto if reason == ofproto.OFPPR_ADD: self.logger.info("port added %s", port_no) elif reason == ofproto.OFPPR_DELETE: self.logger.info("port deleted %s", port_no) elif reason == ofproto.OFPPR_MODIFY: self.logger.info("port modified %s", port_no) else: self.logger.info("Illeagal port state %s %s", port_no, reason)
（三）Mininet開始啟動網絡拓撲
sudo mn --custom tree_topt.py --topo=mytopo --controller=remote,ip=127.0.0.1,port=6633
注意：應該是主機連接發送了數據，導致控制器對網絡進行了拓撲收集，問題同上：SDN實驗---Ryu的應用開發（二）Learning Switch
三：進行OpenFlow流表分析
（一）主要流表操作命令
dpctl dump-flows 查看靜態流表
dpctl del-flows 刪除所有交換機中的流表
dpctl add-flow in_port=1,actions=output:2 添加流表項到所有交換機，注意：一般是成對添加，實現雙方通信
sh ovs-ofctl del-flows s1 in_port=2 刪除指定交換機的，匹配in_port=2的流表
dpctl del-flows in_port=1 刪除所有交換機中符合in_port=1的流表
dpctl add-flow in_port=2,actions=drop 添加丟棄數據包的流表項
（二）先解決上面問題，是不是啟動Mininet后進行了數據包發送，導致控制器下發流表
重新啟動Ryu和Mininet，直接查看交換機中是否有流表.
1.先啟動交換機，查看流表，為空
2.啟動控制器，之后再查看交換機中流表信息，依舊為空
3.主機使用pingall命令后，查看流表，發生變化
已解決。但是交換機是如何設置默認流表當不知道packet如何處理的時候發生給控制器？如果這是默認動作，那么我們之前Ryu實驗中為何要實現 @set_ev_cls(ofp_event.EventOFPSwitchFeatures,CONFIG_DISPATCHER) def switch_features_handler(self,ev): ？？？？？
經過啟動hub.py在控制器上，進行測試，發現會進入switch_features_handler,並且會下發默認流表---所以說，我們可以不用設置這個默認流表也可以，但是這個函數中，我們可以設置一些其他的流表進行控制---所以說還是比較有用的
注意從（三）開始的實驗我們需要關閉控制器Ryu進行
（三）刪除所有流表
由於沒有流表，所有ping操作不可達
（四）添加h1與和h2之間的流表轉發
1.單個交換機操作
2.h1 ping h2,信息可達（因為有流表進行指導）
3.h1 ping h3,消息不可達（因為交換機2中沒有流表項，並且交換機1也沒有配置到port3的動作
4.實現所有網絡所有主機互通（先清空流表）
為所有交換機添加端口1和端口2的操作---兩個交換機公共操作
dpctl add-flow in_port=1,actions=output:2
dpctl add-flow in_port=2,actions=output:1
為交換機之間端口提供交互---只操作s1(因為只有s1有端口3)
sh ovs-ofctl add-flow s1 in_port=1,actions=output:2,3
sh ovs-ofctl add-flow s1 in_port=3,actions=output:1,2
sh ovs-ofctl add-flow s1 in_port=2,actions=output:1,3
實驗結果顯示
或者：我們直接添加下面流表也可以實現上面操作
mininet> dpctl add-flow in_port=1,actions=output:2,3 mininet> dpctl add-flow in_port=2,actions=output:1,3 mininet> dpctl add-flow in_port=3,actions=output:1,2
5.為交換機2添加丟棄流表，使得兩個交換機不可通信（在前面互通基礎上實現）
mininet> sh ovs-ofctl del-flows s2 in_port=1 刪除原有流表 mininet> sh ovs-ofctl add-flow s2 in_port=1,actions=drop 添加丟棄流表
