实验5：开源控制器实践——POX

（一）基本要求
1.h1 ping h2、h2和h3的tcpdump抓包结果
使用 tcpdump 验证Hub模块

使用 tcpdump 验证Switch模块

2.L2_learning模块代码流程图

（二）进阶要求

1.重新搭建（一）的拓扑，此时交换机内无流表规则，拓扑内主机互不相通；编写Python程序自定义一个POX模块SendFlowInSingle3，并且将拓扑连接至SendFlowInSingle3（默认端口6633），实现向s1发送流表规则使得所有主机两两互通

SendFlowInSingle3代码

from pox.core import core
import pox.openflow.libopenflow_01 as of
from pox.openflow.of_json import *

def _handle_ConnectionUp(event):

  # h1 -> h2 h1 -> h3
  msg = of.ofp_flow_mod()
  msg.priority = 1
  msg.match.in_port = 1
  msg.actions.append(of.ofp_action_output(port=2))
  msg.actions.append(of.ofp_action_output(port=3))
  event.connection.send(msg)

  # h2 -> h1 h2 -> h3
  msg = of.ofp_flow_mod()
  msg.priority = 1
  msg.match.in_port = 2
  msg.actions.append(of.ofp_action_output(port=1))
  msg.actions.append(of.ofp_action_output(port=3))
  event.connection.send(msg)

  # h3 -> h1 h3 -> h2 
  msg = of.ofp_flow_mod()
  msg.priority = 1
  msg.match.in_port = 3
  msg.actions.append(of.ofp_action_output(port=1))
  msg.actions.append(of.ofp_action_output(port=2))
  event.connection.send(msg)


def launch():
  core.openflow.addListenerByName("ConnectionUp", _handle_ConnectionUp) 

2.基于进阶1的代码，完成ODL实验的硬超时功能
先运行SendFlowSingle3，先通再断再恢复

直接运行SendPoxHardTimeOut，先断后通，能验证流表项生效即可

SendPoxHardTimeOut代码

from pox.core import core
import pox.openflow.libopenflow_01 as of

class SendPoxHardTimeOut(object):
   def __init__(self):
       core.openflow.addListeners(self)
   def _handle_ConnectionUp(self, event):
 
       msg = of.ofp_flow_mod()  
       msg.priority = 3
       msg.match.in_port = 1 
       msg.hard_timeout = 10  
       event.connection.send(msg)
       
       msg = of.ofp_flow_mod()  
       msg.priority = 1
       msg.match.in_port = 1 
       msg.actions.append(of.ofp_action_output(port = of.OFPP_ALL)) 
       event.connection.send(msg)

       msg = of.ofp_flow_mod()  
       msg.priority = 3
       msg.match.in_port = 3 
       msg.hard_timeout = 10 
       event.connection.send(msg)
       
       msg = of.ofp_flow_mod() 
       msg.priority = 1
       msg.match.in_port = 3  
       msg.actions.append(of.ofp_action_output(port = of.OFPP_ALL))
       event.connection.send(msg)

def launch():
   core.registerNew(SendPoxHardTimeOut)

三.实验心得
这次的实验让我对pox各个模块的功能以及使用方法有了更加深刻的认识，理解了pox控制器的工作原理，掌握运用pox控制器编写自定义网络应用程序，进一步熟悉POX控制器流表下发的方法。
本次实验在编写python代码时编写不了 需要开权限 chmod 777 +文件名。