Netfilter example in python

netfilter.py

## Installation
# sudo apt-get install build-essential python-dev libnetfilter-queue-dev
# sudp pip install NetfilterQueue scapy

## References
# https://www.digitalocean.com/community/tutorials/how-to-list-and-delete-iptables-firewall-rules
# https://github.com/phaethon/scapy
# https://5d4a.wordpress.com/2011/08/25/having-fun-with-nfqueue-and-scapy/
# https://pypi.python.org/pypi/NetfilterQueue/0.3
# http://www.netfilter.org/documentation/HOWTO/netfilter-hacking-HOWTO-3.html
# http://www.linuxjournal.com/article/7356

import netfilterqueue
import socket
import sys

from scapy.all import *

def process(pkt):
    data = pkt.get_payload()
    p = IP(data)
    pkt.set_verdict_modified(nfqueue.NF_ACCEPT, str(p), len(p))

nfqueue = netfilterqueue.NetfilterQueue()
nfqueue.bind(1, process)

try:
    nfqueue.run()
except:
    nfqueue.unbind()
    sys.exit(1)

# sudo iptables -A INPUT -d 127.0.0.1/32 -j NFQUEUE --queue-num 1