Mininet系列实验（七）：Mininet脚本实现控制交换机行为

1 实验目的

• 熟悉Mininet自定义拓扑脚本的编写；
• 掌握使用“ovs-vsctl”命令直接控制Open vSwitch。

2 实验原理

在SDN环境中，控制器可以通过对交换机下发流表操作来控制交换机的转发行为。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。

3 实验任务

本实验在基于Mininet脚本的不同拓扑环境下使用OpenDaylight控制交换机行为。任务一：一台交换机两台主机，从1端口进入的数据流转发到2端口，从2端口进入的数据流转发到1端口；任务二：两台交换机两台主机，主机0连接交换机0，主机1连接交换机1，交换机0连接交换机1，数据转发端口同任务一；任务三：与任务二类似，但是在创建link的时候，设置带宽、延迟以及丢包率。

任务一：一台交换机两台主机，实现从1端口进入的数据流转发到2端口，从2端口进入的数据流转发到1端口。

还是那个流程：

打开mininet文件夹——创建mymininet1.py——编辑脚本保存——改为可执行——清内存——开发者模式内打开

 # !/usr/bin/python
 from mininet.net import Mininet
 from mininet.node import Node
 from mininet.link import Link
 from mininet.log import setLogLevel, info
 from mininet.util import quietRun
 # 调用Mininet相关模块

 from time import sleep
 # 调用sleep模块 

 def scratchNet( cname='controller', cargs='-v ptcp:' ):
     "Create network from scratch using Open vSwitch."

     # 创建网络节点其中有两个主机，一个交换机，一个控制器
     info( "*** Creating nodes\n" )
     controller = Node( 'c0', inNamespace=False )
     switch0 = Node( 's0', inNamespace=False )
     h0 = Node( 'h0' )
     h1 = Node( 'h1' )

     # 创建网络连接，分别是h0-s0和h1-s0
     info( "*** Creating links\n" )
     Link( h0, switch0 )
     Link( h1, switch0 )

     # 设置主机的IP地址，然后再诊断的同时打印出string化的h0h1
     info( "*** Configuring hosts\n" )
     h0.setIP( '192.168.123.1/24' )
     h1.setIP( '192.168.123.2/24' )
     info( str( h0 ) + '\n' )
     info( str( h1 ) + '\n' )

     # 开启控制器和s0的链路
     info( "*** Starting network using Open vSwitch\n" )
     controller.cmd( cname + ' ' + cargs + '&' )
     switch0.cmd( 'ovs-vsctl del-br dp0' )
     switch0.cmd( 'ovs-vsctl add-br dp0' )

     # 在交换机的信息库里面依次打出信息
     for intf in switch0.intfs.values():
         print intf
         print switch0.cmd( 'ovs-vsctl add-port dp0 %s' % intf )
     switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:10.0.0.8:6633' )
     switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=1 actions=output:2\"' )
     switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=2 actions=output:1\"' )

     # 等待连接的小程序
     info( '*** Waiting for switch to connect to controller' )
     while 'is_connected' not in quietRun( 'ovs-vsctl show' ):
         sleep( 1 )
         info( '.' )
     info( '\n' )

     # 两个互ping6次
     info( "*** Running test\n" )
     h0.cmdPrint( 'ping -c6 ' + h1.IP() )
     h1.cmdPrint( 'ping -c6 ' + h0.IP() )

     # 关闭这个网络
     info( "*** Stopping network\n" )
     controller.cmd( 'kill %' + cname )
     switch0.cmd( 'ovs-vsctl del-br dp0' )
     switch0.deleteIntfs()
     info( '\n' )

 # 主函数部分，设置打印等级，还有调用以上的一些函数
 if __name__ == '__main__':
     setLogLevel( 'info' )
     info( '*** Scratch network demo (kernel datapath)\n' )
     Mininet.init()
     scratchNet()

任务二：两台交换机两台主机，主机0连接交换机0，主机1连接交换机1，交换机0连接交换机1，数据转发端口要求同任务一。

和前者的脚本大同小异，这里就解释mymininet1.py没有的，print switch0.cmd( 'ovs-ofctl show dp0' )意思就是打出关于s0的信息

1.  1 #!/usr/bin/python  
    2 from mininet.net import Mininet
    from mininet.node import Node
    from mininet.link import Link
    from mininet.log import setLogLevel, info
    from mininet.util import quietRun
   
    from time import sleep
   
    def scratchNet( cname='controller', cargs='-v ptcp:' ):
        "Create network from scratch using Open vSwitch."
   
        info( "*** Creating nodes\n" )
        controller = Node( 'c0', inNamespace=False )
        switch0 = Node( 's0', inNamespace=False )
        switch1 = Node( 's1', inNamespace=False )
        h0 = Node( 'h0' )
        h1 = Node( 'h1' )
   
        info( "*** Creating links\n" )
        Link( h0, switch0 )
        Link( h1, switch1 )
        Link( switch0, switch1 )
   
        info( "*** Configuring hosts\n" )
        h0.setIP( '192.168.123.1/24' )
        h1.setIP( '192.168.123.2/24' )
        info( str( h0 ) + '\n' )
        info( str( h1 ) + '\n' )
   
        info( "*** Starting network using Open vSwitch\n" )
        controller.cmd( cname + ' ' + cargs + '&' )
        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 )
   
        switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:10.0.0.8:6633' )
        switch1.cmd( 'ovs-vsctl set-controller dp1 tcp: 10.0.0.8:6633' )
        switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=1 actions=output:2\"' )
        switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=2 actions=output:1\"' )
        switch1.cmd( 'ovs-ofctl add-flow dp1 \"in_port=1 actions=output:2\"' )
        switch1.cmd( 'ovs-ofctl add-flow dp1 \"in_port=2 actions=output:1\"' )
   
        info( '*** Waiting for switch to connect to controller' )
        while 'is_connected' not in quietRun( 'ovs-vsctl show' ):
            sleep( 1 )
            info( '.' )
        info( '\n' )
        print switch0.cmd( 'ovs-ofctl show dp0' )
        print switch1.cmd( 'ovs-ofctl show dp1' )
   
        info( "*** Running test\n" )
        h0.cmdPrint( 'ping -c3 ' + h1.IP() )
        h1.cmdPrint( 'ping -c3 ' + h0.IP() )
   
        info( "*** Stopping network\n" )
        controller.cmd( 'kill %' + cname )
        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()
        scratchNet()

任务三：与任务二类似，但是在创建link的时候，设置带宽、延迟以及丢包率。

 #!/usr/bin/python
 from mininet.net import Mininet
 from mininet.node import Node
 from mininet.link import TCLink
 from mininet.log import setLogLevel, info
 from mininet.util import quietRun

 from time import sleep

 def scratchNet( cname='controller', cargs='-v ptcp:' ):
     "Create network from scratch using Open vSwitch."

     info( "*** Creating nodes\n" )
     controller = Node( 'c0', inNamespace=False )
     switch0 = Node( 's0', inNamespace=False )
     switch1 = Node( 's1', inNamespace=False )
     h0 = Node( 'h0' )
     h1 = Node( 'h1' )

     info( "*** Creating links\n" )

     linkopts0=dict(bw=10)
     linkopts1=dict(bw=10, delay='5ms', loss=10)
     TCLink( h0, switch0,**linkopts0)
     TCLink( h1, switch1,**linkopts0)
     TCLink( switch0, switch1,**linkopts1)

     info( "*** Configuring hosts\n" )
     h0.setIP( '192.168.123.1/24' )
     h1.setIP( '192.168.123.2/24' )
     info( str( h0 ) + '\n' )
     info( str( h1 ) + '\n' )

     info( "*** Starting network using Open vSwitch\n" )
     controller.cmd( cname + ' ' + cargs + '&' )
     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 )

     switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:10.0.0.8:6633' )
     switch1.cmd( 'ovs-vsctl set-controller dp1 tcp: 10.0.0.8:6633' )
     switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=1 actions=output:2\"' )
     switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=2 actions=output:1\"' )
     switch1.cmd( 'ovs-ofctl add-flow dp1 \"in_port=1 actions=output:2\"' )
     switch1.cmd( 'ovs-ofctl add-flow dp1 \"in_port=2 actions=output:1\"' )

     info( '*** Waiting for switch to connect to controller' )
     while 'is_connected' not in quietRun( 'ovs-vsctl show' ):
         sleep( 1 )
         info( '.' )
     info( '\n' )
     print switch0.cmd( 'ovs-ofctl show dp0' )
     print switch1.cmd( 'ovs-ofctl show dp1' )

     info( "*** Running test\n" )
     h0.cmdPrint( 'ping -c3 ' + h1.IP() )
     h1.cmdPrint( 'ping -c3 ' + h0.IP() )

     info( "*** Stopping network\n" )
     controller.cmd( 'kill %' + cname )
     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()
     scratchNet()

总结：

1.对ovs加深理解

2.能够完全看懂脚本

3.需要更深一步了解mininet的模块的函数