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

一、實驗目的

Mininet 安裝之後，會連帶安裝 Open vSwitch，可以直接通過 Python 指令碼呼叫Open vSwitch 命令，從而直接控制 Open vSwitch，通過實驗瞭解呼叫控制的方法。

二、實驗任務

在本實驗中，使用 Mininet 基於 Python 的指令碼，呼叫“ovs-vsctl”命令直接控制Open vSwitch。使用預設的交換機泛洪規則，設定更高的優先順序規則進行預先定義 IP 報文的轉發。在多個交換機中通過設定不同 TOS 值的資料包將通過不同的方式到達目的地址，驗證主機間的連通性及到達目的地址的時間。

三、實驗步驟

1. 實驗環境

安裝了 Ubuntu 18.04.5 Desktop amd64 的虛擬機器

2. 實驗過程

（1）修改程式碼為

#!/usr/bin/python
 
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='100ms', loss=0)
    linkopts2=dict(bw=10, delay='50ms', loss=0)
    TCLink( switch0, switch1, **linkopts0)
    TCLink( h0, switch0, **linkopts1)
    TCLink( h2, switch1, **linkopts1)
    TCLink( h1, switch0, **linkopts2)
    TCLink( h3, switch1, **linkopts2)	
 
    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'sudo ovs-ofctl -O OpenFlow13 add-flow dp0 priority=1,dl_vlan=0,actions=pop_vlan,output:1' )
    print switch0.cmd(r'sudo 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' )

    #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 0x20 -c 3 ' + h2.IP() )
    h0.cmdPrint( 'ping -Q 0x30 -c 3 ' + h3.IP() )
    h1.cmdPrint( 'ping -Q 0x40 -c 3 ' + h2.IP() )
    h1.cmdPrint( 'ping -Q 0x50 -c 3 ' + h3.IP() )
    h2.cmdPrint( 'ping -Q 0x60 -c 3 ' + h3.IP() )
    #h1.cmdPrint('iperf -s -p 12345 -u &')
    #h0.cmdPrint('iperf -c ' + h1.IP() +' -u -b 10m -p 12345 -t 10 -i 1')

    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()