SDN/Pox simple firewall module

'''
Software Defined Networking
Pox Controller module
Simple firewall module
All deny rules located in the firewall-policies file in CSV format
'''

from pox.core import core
import pox.openflow.libopenflow_01 as of
from pox.lib.revent import *
from pox.lib.util import dpidToStr
from pox.lib.addresses import EthAddr
from collections import namedtuple
import os
import csv


log = core.getLogger()
policyFile = "%s/pox/pox/misc/firewall-policies.csv" % os.environ[ 'HOME' ]

rules = []

with open(policyFile, 'rb') as f:
    reader = csv.reader(f)
    header = f.readline()
    for row in reader:
        row.pop(0)
        rules.append(row)



log = core.getLogger()

HARD_TIMEOUT = 30
IDLE_TIMEOUT = 30
class FirewallLogic (EventMixin):

  def __init__ (self,connection):

    self.connection= connection
    self.listenTo(connection)


  def _handle_PacketIn (self, event):


    for (src,dst) in rules:
      # drop - no action
      log.debug("Packet from %s to %s is not allowed" % (src, dst))
      match = of.ofp_match()
      match.dl_src = src
      match.dl_dst = dst
      msg = of.ofp_packet_out()
      msg.match = match
      self.connection.send(msg)
      return


class Firewall (EventMixin):

    def __init__ (self):
        self.listenTo(core.openflow)
        log.debug("Enabling Firewall Module")

    def _handle_ConnectionUp (self, event):
        FirewallLogic(event.connection)


        log.debug("Firewall rules installed on %s", dpidToStr(event.dpid))

def launch ():
    '''
    Starting the Firewall module
    '''
    core.registerNew(Firewall)