一个简单的DNS server

'''
This program simulate as a DNS server

'''

一直工作在UDP 53端口监听DNS请求。收到请求后取出transcation id，query的数据，构造一个DNS相应包。每次返回的IP地址都是127.0.0.1(\x7f\x00\x00\x01)

用于样本分析，触发网络行为。

import socket

server = '192.168.160.1'
dns_header = '\x81\x80\x00\x01\x00\x01\x00\x00\x00\x00'
dns_queries = ''
#\x7f\x00\x00\x01 is 127.0.0.1 you can replace it with
dns_answers = '\xc0\x0c\x00\x01\x00\x01'+'\x00\x00\x01\x2c'+'\x00\x04\x7f\x00\x00\x01'


address = (server, 53)
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind(address)


while True:
    data, addr = s.recvfrom(2048)
    print "received from", addr
    id = data[0:2]
    dns_queries = data[12:]
    dns_msg = id+dns_header+dns_queries+dns_answers
    s.sendto(dns_msg,addr)
s.close()