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

OVS 实现 VLAN 可参考博客：https://www.cnblogs.com/fjlinww/p/11791846.html

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

ovsSingleBr.py代码如下

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=‘5ms‘, loss=0)
    linkopts1 = dict(bw=200, 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( str( h0 ) + ‘\n‘ )
    info( str( h1 ) + ‘\n‘ )
    info( str( h2 ) + ‘\n‘ )
    info( str( h3 ) + ‘\n‘ )
    
    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 ))

    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 dp1 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 dp1 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 dp1 priority=1,dl_vlan=0,actions=pop_vlan,output:1‘ ))
    print(switch1.cmd(r‘ovs-ofctl -O OpenFlow13 add-flow dp1 priority=1,dl_vlan=1,actions=pop_vlan,output:2‘ ))

    info( "*** Running test\n" )
    h0.cmdPrint( ‘ping -c 3 ‘ + h1.IP() )
    h0.cmdPrint( ‘ping -c 3 ‘ + h2.IP() )
    h0.cmdPrint( ‘ping -c 3 ‘ + h3.IP() )
    h1.cmdPrint( ‘ping -c 3 ‘ + h2.IP() )
    h1.cmdPrint( ‘ping -c 3 ‘ + h3.IP() )
    h2.cmdPrint( ‘ping -c 3 ‘ + h3.IP() )

    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()

结果如下图

实验 4：Open vSwitch 实验——Mininet 中使用 OVS 命令