一、实验目的
Mininet 安装之后，会连带安装 Open vSwitch，可以直接通过 Python 脚本调用
Open vSwitch 命令，从而直接控制 Open vSwitch，通过实验了解调用控制的方法。
二、实验任务
在本实验中，使用 Mininet 基于 Python 的脚本，调用“ovs-vsctl”命令直接控制
Open vSwitch。使用默认的交换机泛洪规则，设置更高的优先级规则进行预先定
义 IP 报文的转发。在多个交换机中通过设置不同 TOS 值的数据包将通过不同的
方式到达目的地址，验证主机间的连通性及到达目的地址的时间。
三、实验步骤
1. 实验环境
安装了 Ubuntu 18.04.5 Desktop amd64 的虚拟机
2. 实验过程
SDNLAB 实验参考资料：https://www.sdnlab.com/15083.html
（1）实验目的：学习 ovsSingleBr.py 和 ovsMultiBr.py，在下图拓扑中实现一个 VLAN。
（2）代码：
1 #!/usr/bin/python 2 3 from mininet.net import Mininet 4 from mininet.node import Node 5 from mininet.link import TCLink 6 from mininet.log import setLogLevel, info 7 8 def myNet(): 9 "Create network from scratch using Open vSwitch." 10 11 info( "*** Creating nodes " ) 12 switch0 = Node( 's0', inNamespace=False ) 13 switch1 = Node( 's1', inNamespace=False ) 14 15 h0 = Node( 'h0' ) 16 h1 = Node( 'h1' ) 17 h2 = Node( 'h2' ) 18 h3 = Node( 'h3' ) 19 20 info( "*** Creating links " ) 21 linkopts0=dict(bw=100, delay='1ms', loss=0) 22 linkopts1=dict(bw=1, delay='10ms', loss=0) 23 TCLink( h0, switch0, **linkopts0) 24 TCLink( h1, switch0, **linkopts0) 25 TCLink( h2, switch1, **linkopts0) 26 TCLink( h3, switch1, **linkopts0) 27 TCLink( switch0, switch1, **linkopts1) 28 29 30 info( "*** Configuring hosts " ) 31 h0.setIP( '192.168.123.1/24' ) 32 h1.setIP( '192.168.123.2/24' ) 33 h2.setIP( '192.168.123.3/24' ) 34 h3.setIP( '192.168.123.4/24' ) 35 36 info( "*** Starting network using Open vSwitch " ) 37 switch0.cmd( 'ovs-vsctl del-br dp0' ) 38 switch0.cmd( 'ovs-vsctl add-br dp0' ) 39 switch1.cmd( 'ovs-vsctl del-br dp1' ) 40 switch1.cmd( 'ovs-vsctl add-br dp1' ) 41 42 for intf in switch0.intfs.values(): 43 print intf 44 print switch0.cmd( 'ovs-vsctl add-port dp0 %s' % intf ) 45 46 for intf in switch1.intfs.values(): 47 print intf 48 print switch1.cmd( 'ovs-vsctl add-port dp1 %s' % intf ) 49 50 # Note: controller and switch are in root namespace, and we 51 # can connect via loopback interface 52 #switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:127.0.0.1:6633' ) 53 # switch0.cmd(r'ovs-ofctl del-flows dp0') 54 # switch1.cmd(r'ovs-ofctl del-flows dp1') 55 56 print switch0.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096->vlan_vid,output:3') 57 print switch0.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,in_port=2,actions=push_vlan:0x8100,set_field:4097->vlan_vid,output:3') 58 print switch0.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=0,actions=pop_vlan,output:1') 59 print switch0.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=1,actions=pop_vlan,output:2') 60 61 print switch1.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096->vlan_vid,output:3') 62 print switch1.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,in_port=2,actions=push_vlan:0x8100,set_field:4097->vlan_vid,output:3') 63 print switch1.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=0,actions=pop_vlan,output:1') 64 print switch1.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=1,actions=pop_vlan,output:2') 65 66 #switch0.cmd('tcpdump -i s0-eth0 -U -w aaa &') 67 #h0.cmd('tcpdump -i h0-eth0 -U -w aaa &') 68 info( "*** Running test " ) 69 h0.cmdPrint( 'ping -Q 0x10 -c 3 ' + h1.IP() ) 70 h0.cmdPrint( 'ping -Q 0x10 -c 3 ' + h2.IP() ) 71 h0.cmdPrint( 'ping -Q 0x10 -c 3 ' + h3.IP() ) 72 h1.cmdPrint( 'ping -Q 0x10 -c 3 ' + h2.IP() ) 73 h1.cmdPrint( 'ping -Q 0x10 -c 3 ' + h3.IP() ) 74 h2.cmdPrint( 'ping -Q 0x10 -c 3 ' + h3.IP() ) 75 76 #print switch0.cmd( 'ovs-ofctl show dp0' ) 77 #print switch0.cmd( 'ovs-ofctl dump-tables dp0' ) 78 #print switch0.cmd( 'ovs-ofctl dump-ports dp0' ) 79 #print switch0.cmd( 'ovs-ofctl dump-flows dp0' ) 80 #print switch0.cmd( 'ovs-ofctl dump-aggregate dp0' ) 81 #print switch0.cmd( 'ovs-ofctl queue-stats dp0' ) 82 83 info( "*** Stopping network " ) 84 switch0.cmd( 'ovs-vsctl del-br dp0' ) 85 switch0.deleteIntfs() 86 switch1.cmd( 'ovs-vsctl del-br dp1' ) 87 switch1.deleteIntfs() 88 info( ' ' ) 89 90 if __name__ == '__main__': 91 setLogLevel( 'info' ) 92 info( '*** Scratch network demo (kernel datapath) ' ) 93 Mininet.init() 94 myNet()
上述代码将 h0 和 h2 划分在 VLAN 0 中，h1 和 h3 划分在 VLAN 1 中，由于拓扑没
有控制器，并且初始化时删除了交换机中的所有流表，因此除非下发流表，否则
主机之间网络无法连通。请尝试修改代码，利用 ovs 命令直接下发 VLAN 设置的
流表项，最终测试 h0 和 h2 互通，h1 和 h3 互通，其余主机均不通，结果如下图。
OVS 实现 VLAN 可参考博客：https://www.cnblogs.com/fjlinww/p/11791846.html
（3）ovs流表
1 sudo ovs-ofctl -O OpenFlow13 add-flow s0 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096->vlan_vid,output:3 2 sudo ovs-ofctl -O OpenFlow13 add-flow s0 priority=1,in_port=2,actions=push_vlan:0x8100,set_field:4097->vlan_vid,output:3 3 sudo ovs-ofctl -O OpenFlow13 add-flow s0 priority=1,dl_vlan=0,actions=pop_vlan,output:1 4 sudo ovs-ofctl -O OpenFlow13 add-flow s0 priority=1,dl_vlan=1,actions=pop_vlan,output:2 5 6 sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096->vlan_vid,output:3 7 sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,in_port=2,actions=push_vlan:0x8100,set_field:4097->vlan_vid,output:3 8 sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,dl_vlan=0,actions=pop_vlan,output:1 9 sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,dl_vlan=1,actions=pop_vlan,output:2
（4）实验结果
