python – NetfilterQueue set_payload不起作用

但我遇到麻烦,NetfilterQueue模块的set_payload()方法对我来说似乎不起作用.

这是我的源代码.

from netfilterqueue import NetfilterQueue as nfqueue
from scapy.all import *
import os
import socket
import re

baidu_ip = socket.gethostbyname('www.baidu.com')
print "Got baidu ip: " + baidu_ip

iptablesr = 'iptables -t mangle -A POSTROUTING -p tcp -j NFQUEUE --queue-num 1'
print("Adding iptable rules :")
print(iptablesr)
os.system(iptablesr)
iptablesr = 'iptables -t mangle -A POSTROUTING -p udp -j NFQUEUE --queue-num 1'
print(iptablesr)
os.system(iptablesr)


def callback(packet):
    modified = False
    sca_pkt = IP(packet.get_payload())

    # This is the main logic,to modify the packet
    try:
        dns_lookup = re.search(r'DNS Qry "([w.]+)"',sca_pkt[DNS].summary()).group(1)
        if re.search(r'baidu.com',dns_lookup) != None:
            sca_pkt[DNS].qd = DNSQR(qname='www.163.com')
            sca_pkt[UDP].len = len(bytes(sca_pkt[UDP]))
            sca_pkt[UDP].chksum = 0x0000
            modified = True
    except:
        pass

    # Accept the modified packet
    if modified == True:
        print 'debug sca_pkt: ' + sca_pkt.summary()
        packet.set_payload(str(sca_pkt))
        print 'debug packet: ' + IP(packet.get_payload()).summary()
        packet.accept()
        return 

    packet.accept()

def main():
    q = nfqueue()
    q.bind(1,callback)
    try:
        q.run()
    except KeyboardInterrupt:
        q.unbind()
        print "Flushing iptables."
        os.system('iptables -F')
        os.system('iptables -F -t mangle')

if __name__ == '__main__':
    main()

这是我得到的输出.

Got baidu ip: 180.97.33.108
Adding iptable rules :
iptables -t mangle -A POSTROUTING -p tcp -j NFQUEUE --queue-num 1
iptables -t mangle -A POSTROUTING -p udp -j NFQUEUE --queue-num 1
debug sca_pkt: IP / UDP / DNS Qry "www.163.com" 
debug packet: IP / UDP / DNS Qry "baidu.com."

您可以从调试信息中看到,set_payload()不起作用. (我将数据包设置为sca_pkt中显示的值,但是当我获得数据包有效负载摘要时,它仍然是原始值)

我刚刚尝试了两个版本的NetfilterQueue,包括pip版本和https://github.com/kti/python-netfilterqueue.git版本.

那么有人可以帮助我吗？我对此非常好奇.