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#!/usr/bin/python
# need root privileges
import struct
import sys
import time
from socket import AF_INET, AF_INET6, inet_ntoa
sys.path.append('python')
sys.path.append('build/python')
import nfqueue
sys.path.append('dpkt-1.6')
from dpkt import ip, tcp, hexdump
def cb(i,payload):
print "payload len ", payload.get_length()
data = payload.get_data()
pkt = ip.IP(data)
print "proto:", pkt.p
print "source: %s" % inet_ntoa(pkt.src)
print "dest: %s" % inet_ntoa(pkt.dst)
if pkt.p == ip.IP_PROTO_TCP:
print " sport: %s" % pkt.tcp.sport
print " dport: %s" % pkt.tcp.dport
print " flags: %s" % pkt.tcp.flags
if pkt.tcp.flags & tcp.TH_PUSH:
pkt2 = pkt
print "PUSH *****"
print pkt2.tcp.data
old_len = len(pkt2.tcp.data)
#pkt2.tcp.data = "GET /\r\n"
pkt2.tcp.data = str(pkt2.tcp.data).replace('love','hate')
print pkt2.tcp.data
pkt2.len = pkt2.len - old_len + len(pkt2.tcp.data)
pkt2.tcp.sum = 0
pkt2.sum = 0
ret = payload.set_verdict_modified(nfqueue.NF_ACCEPT,str(pkt2),len(pkt2))
print "ret = ",ret
return 0
payload.set_verdict(nfqueue.NF_ACCEPT)
sys.stdout.flush()
return 1
q = nfqueue.queue()
print "setting callback"
q.set_callback(cb)
print "open"
q.fast_open(0, AF_INET)
print "trying to run"
try:
q.try_run()
except KeyboardInterrupt, e:
print "interrupted"
print "unbind"
q.unbind(AF_INET)
print "close"
q.close()
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