软件定义网络实验记录④--Open vSwitch 实验——Mininet 中使用 OVS 命令

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
   创建ovsMyVlanBr.py 脚本并运行
   ovsMyVlanBr.py对应的拓扑图如下：
   
   ovsMyVlanBr.py代码如下：

#!/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)
  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') 
  
  #print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.2,actions=output:4')
  
  #print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.1,actions=output:1')

  #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')

  #print switch0.cmd( 'ovs-ofctl show dp0' )    
  #print switch1.cmd( 'ovs-ofctl show dp1' )
  #print switch2.cmd( 'ovs-ofctl show dp2' )
  #print switch3.cmd( 'ovs-ofctl show dp3' )
  #print switch4.cmd( 'ovs-ofctl show dp4' )  
  #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' )

  #print "Testing video transmission between h1 and h2"
  #h1.cmd('./myrtg_svc -u > myrd &')
  #h0.cmd('./mystg_svc -trace st 192.168.123.2')

  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()

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。通过尝试修改代码，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。