an attempt to create a async twisted interface to the iptables NFLOG blocking packet reads; this example happens to use an echo server because it's simple. Use this with an iptables rule to populate the NFLOG e.g. iptables -A INPUT -p tcp --dport 2600 -j NFLOG

nflog twisted

#!/usr/bin/env python

import os
from nflog_cffi import NFLOG
from twisted.internet.protocol import Protocol, Factory
from twisted.internet import reactor



def NFLOG_get_packets(callback):

    def packet_handler(data):
        print 'NFLOG heard: sz=%dB' % len(data)
        reactor.callFromThread(callback, len(data))

    nflog_kwargs = dict()
    queues       = 0, 1
    nflog        = NFLOG().generator(queues, **nflog_kwargs)
    nflog.next()

    for pkt in nflog:        
        packet_handler(pkt)



class NFLOG_Echo(Protocol):
    def connectionLost(self, reason):
        os._exit(0)
 
    def connectionMade(self):
        reactor.callInThread(NFLOG_get_packets, self.packetReceived)
 
    def dataReceived(self, data):
        print 'echo got: %s' % data
 
    def packetReceived(self, sz):
        self.transport.write('pcap got: %uB\n' % sz)
 
def main():
    factory = Factory()
    factory.protocol = NFLOG_Echo
    reactor.listenTCP(9999, factory)
    reactor.run()
 
if __name__ == "__main__":
    main()