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
学习 ovsSingleBr.py 和 ovsMultiBr.py，在下图拓扑中实现一个 VLAN。

代码：

from mininet.net import Mininet
from mininet.node import Node
from mininet.link import TCLink
from mininet.log import setLogLevel, info

def myNet():
"Create network from scratch using Open vSwitch."

info( "*** Creating nodes\n" )
switch0 = Node( 's0', inNamespace=False )
switch1 = Node( 's1', inNamespace=False )

h0 = Node( 'h0' )
h1 = Node( 'h1' )
h2 = Node( 'h2' )
h3 = Node( 'h3' )

info( "*** Creating links\n" )
linkopts0=dict(bw=100, delay='1ms', loss=0)
linkopts1=dict(bw=1, delay='10ms', loss=0)
TCLink( h0, switch0, **linkopts0)
TCLink( h1, switch0, **linkopts0)
TCLink( h2, switch1, **linkopts0)
TCLink( h3, switch1, **linkopts0)
TCLink( switch0, switch1, **linkopts1)

info( "*** Configuring hosts\n" )
h0.setIP( '192.168.123.1/24' )
h1.setIP( '192.168.123.2/24' )
h2.setIP( '192.168.123.3/24' )
h3.setIP( '192.168.123.4/24' )

info( "*** Starting network using Open vSwitch\n" )
switch0.cmd( 'ovs-vsctl del-br dp0' )
switch0.cmd( 'ovs-vsctl add-br dp0' )
switch1.cmd( 'ovs-vsctl del-br dp1' )
switch1.cmd( 'ovs-vsctl add-br dp1' )

for intf in switch0.intfs.values():
print intf
print switch0.cmd( 'ovs-vsctl add-port dp0 %s' % intf )

for intf in switch1.intfs.values():
print intf
print switch1.cmd( 'ovs-vsctl add-port dp1 %s' % intf )

# Note: controller and switch are in root namespace, and we
# can connect via loopback interface
#switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:127.0.0.1:6633' )
# switch0.cmd(r'ovs-ofctl del-flows dp0')
# switch1.cmd(r'ovs-ofctl del-flows dp1')

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')
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')
print switch0.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=0,actions=pop_vlan,output:1')
print switch0.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=1,actions=pop_vlan,output:2')

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')
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')
print switch1.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=0,actions=pop_vlan,output:1')
print switch1.cmd(r'ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=1,actions=pop_vlan,output:2')

#switch0.cmd('tcpdump -i s0-eth0 -U -w aaa &')
#h0.cmd('tcpdump -i h0-eth0 -U -w aaa &')
info( "*** Running test\n" )
h0.cmdPrint( 'ping -Q 0x10 -c 3 ' + h1.IP() )
h0.cmdPrint( 'ping -Q 0x10 -c 3 ' + h2.IP() )
h0.cmdPrint( 'ping -Q 0x10 -c 3 ' + h3.IP() )
h1.cmdPrint( 'ping -Q 0x10 -c 3 ' + h2.IP() )
h1.cmdPrint( 'ping -Q 0x10 -c 3 ' + h3.IP() )
h2.cmdPrint( 'ping -Q 0x10 -c 3 ' + h3.IP() )

#print switch0.cmd( 'ovs-ofctl show dp0' )
#print switch0.cmd( 'ovs-ofctl dump-tables dp0' )
#print switch0.cmd( 'ovs-ofctl dump-ports dp0' )
#print switch0.cmd( 'ovs-ofctl dump-flows dp0' )
#print switch0.cmd( 'ovs-ofctl dump-aggregate dp0' )
#print switch0.cmd( 'ovs-ofctl queue-stats dp0' )

info( "*** Stopping network\n" )
switch0.cmd( 'ovs-vsctl del-br dp0' )
switch0.deleteIntfs()
switch1.cmd( 'ovs-vsctl del-br dp1' )
switch1.deleteIntfs()
info( '\n' )

if __name__ == '__main__':
setLogLevel( 'info' )
info( '*** Scratch network demo (kernel datapath)\n' )
Mininet.init()
myNet()

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.htm