gistfile1.py

# Original from http://code.activestate.com/recipes/491264/ (r4)
import socket

class DNSQuery:
  def __init__(self, data):
    self.data=data
    self.dominio=''

    tipo = (ord(data[2]) >> 3) & 15   # Opcode bits
    if tipo == 0:                     # Standard query
      ini=12
      lon=ord(data[ini])
      while lon != 0:
        self.dominio+=data[ini+1:ini+lon+1]+'.'
        ini+=lon+1
        lon=ord(data[ini])

  def respuesta(self, ip):
    packet=''
    if self.dominio:
      packet+=self.data[:2] + "\x81\x80"
      packet+=self.data[4:6] + self.data[4:6] + '\x00\x00\x00\x00'   # Questions and Answers Counts
      packet+=self.data[12:]                                         # Original Domain Name Question
      packet+='\xc0\x0c'                                             # Pointer to domain name
      packet+='\x00\x01\x00\x01\x00\x00\x00\x3c\x00\x04'             # Response type, ttl and resource data length -> 4 bytes
      packet+=str.join('',map(lambda x: chr(int(x)), ip.split('.'))) # 4bytes of IP
    return packet

if __name__ == '__main__':
  ip='192.168.1.1'
  print 'pyminifakeDNS:: dom.query. 60 IN A %s' % ip
  
  udps = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
  udps.bind(('',53))
  
  try:
    while 1:
      data, addr = udps.recvfrom(1024)
      p=DNSQuery(data)
      udps.sendto(p.respuesta(ip), addr)
      print 'Respuesta: %s -> %s' % (p.dominio, ip)
  except KeyboardInterrupt:
    print 'Finalizando'
    udps.close()

gistfile2.py

# coding=utf-8

"""
 $ python dns.py
 $ dig @0.0.0.0 -p 5053 -t A ietf.org
"""

import socket
import datetime


TTL = 300
IP = '192.168.1.1'
RECORD_TYPES = {
    '\x00\x01': 'A',
    '\x00\x05': 'CNAME',
    '\x00\x0f': 'MX',
    '\x00\x02': 'NS',
    '\x00\x10': 'TXT',
    '\x00\x1c': 'AAAA',
    '\x00\xff': 'ANY',
}


class Request(object):

    def __init__(self, data):
        self.data = data

    def get_domain(self):
        domain = ''
        tipo = (ord(self.data[2]) >> 3) & 15  # Opcode bits
        if tipo == 0:  # Standard query
            ini = 12
            lon = ord(self.data[ini])
            while lon != 0:
                domain += self.data[ini + 1:ini + lon + 1] + '.'
                ini += lon + 1
                lon = ord(self.data[ini])
        return domain

    def get_raw_type(self):
        return self.data[-4:-2]

    def get_type(self):
        return RECORD_TYPES.get(self.get_raw_type(), 'Unknown')

    def response(self):
        return Response(request=self)


def int_to_hex(value, zfill=None):
    h = hex(value)  # 300 -> '0x12c'
    h = h[2:].zfill((zfill or 0) * 2)  # '0x12c' -> '00012c' if zfill=3
    return h.decode('hex')


def bin_to_hex(value):
    # http://stackoverflow.com/questions/2072351/python-conversion-from-binary-string-to-hexadecimal/2072384#2072384
    # '0000 0100 1000 1101' -> '\x04\x8d'
    value = value.replace(' ', '')
    h = '%0*X' % ((len(value) + 3) // 4, int(value, 2))
    return h.decode('hex')


class Response(object):

    def __init__(self, request):
        self.request = request

    def __str__(self):
        return self.render_packet()

    def _get_ip_bytes(self):
        return str.join('', map(lambda x: chr(int(x)), IP.split('.')))

    def _get_ttl_bytes(self):
        return int_to_hex(TTL, zfill=4)

    def render_packet(self):
        packet = ''
        if self.request.get_domain():
            d = self.request.data
            packet += d[:2]  # Transaction ID
            flags = ''
            flags += '1'  # 1=response, 0=query
            flags += '0000'  # opcode, 0=standard query, 1=inverse query, 2=server status request
            flags += '1'  # Authoritative Answer
            flags += '0'  # Trancated response
            flags += '0'  # Recursion Desired
            flags += '0'  # Recursion Available
            flags += '000'  # reserved, have to be 0
            flags += '0000'  # RCode, 0=no error
            packet += bin_to_hex(flags)
            packet += d[4:6]  # Number of Questions
            packet += d[4:6]  # Number of Answer RRs
            packet += '\x00\x00'  # Number of Authority RRs
            packet += '\x00\x00'  # Number of Additional RRs
            packet += d[12:]  # Original Domain Name Question
            packet += '\xc0\x0c'  # NAME (domain)
            packet += self.request.get_raw_type()  # TYPE
            packet += '\x00\x01'  # CLASS (Internet)
            packet += self._get_ttl_bytes()  # TTL time to live
            packet += int_to_hex(4, zfill=2)  # RDLENGTH
            packet += self._get_ip_bytes()  # RDATA
        return packet


if __name__ == '__main__':
    print "Starting name server..."

    udps = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    udps.bind(('', 5053))

    try:
        while 1:
            data, addr = udps.recvfrom(2048)
            p = Request(data)
            resp = str(p.response())
            udps.sendto(resp, addr)

            now = datetime.datetime.utcnow()
            cols = [now.strftime('%Y-%m-%d %H:%M:%S.%f')] + list(addr) + [p.get_type(), p.get_domain()]
            print '  '.join((unicode(x) for x in cols))
            print data.encode('hex')
            print resp.encode('hex')

except KeyboardInterrupt:
        print "Done."
        udps.close()

Simple DNS server.py

# Tutorial: http://mysshlog.co.uk/tutorials/Python-Simple-Dns-Server
# Source: http://mysshlog.co.uk/download/Dns_Server_Python.py
## {{{ http://code.activestate.com/recipes/491264/ (r4)
#Edited By MySSHLog.co.uk
import socket
import optparse
import time

class DNSQuery:
  def __init__(self, data):
    self.data=data
    self.dominio=''
    self.DnsType=''

    HDNS=data[-4:-2].encode("hex")
    if HDNS == "0001":
      self.DnsType='A'
    elif HDNS == "000f":
      self.DnsType='MX'
    elif HDNS == "0002":
      self.DnsType='NS'
    elif HDNS == "0010":
       self.DnsType="TXT"
    else:
      self.DnsType="Unknown"

    tipo = (ord(data[2]) >> 3) & 15   # Opcode bits
    if tipo == 0:                     # Standard query
      ini=12
      lon=ord(data[ini])
      while lon != 0:
        self.dominio+=data[ini+1:ini+lon+1]+'.'
        ini+=lon+1
        lon=ord(data[ini])

  def respuesta(self, ip):
    packet=''
    if self.dominio:
      packet+=self.data[:2] + "\x81\x80"
      packet+=self.data[4:6] + self.data[4:6] + '\x00\x00\x00\x00'   # Questions and Answers Counts
      packet+=self.data[12:]                                         # Original Domain Name Question
      packet+='\xc0\x0c'                                             # Pointer to domain name
      packet+='\x00\x01\x00\x01\x00\x00\x00\x3c\x00\x04'             # Response type, ttl and resource data length -> 4 bytes
      packet+=str.join('',map(lambda x: chr(int(x)), ip.split('.'))) # 4bytes of IP
    return packet

if __name__ == '__main__':
  parser = optparse.OptionParser()
  parser.add_option("-f", "--filename", action="store", type="string",dest="SaveFile", help="input a filename to log output too")
  (options, args) = parser.parse_args()
  
  ip='192.168.1.1'
  print 'pyminifakeDNS:: dom.query. 60 IN A %s' % ip
  
  udps = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
  udps.bind(('',53))
  
  try:
    while 1:
      data, addr = udps.recvfrom(1024)
      p=DNSQuery(data)
      udps.sendto(p.respuesta(ip), addr)
      print 'Respuesta: %s -> %s -> %s -> %s' % (addr[0], p.DnsType, p.dominio, ip)
      if options.SaveFile:
        MyDate=time.strftime('%Y %m %d')
        MyTime=time.strftime('%H:%M:%S')
        logfile = open(options.SaveFile,"a")
        logfile.write('%s,%s,%s,%s,%s,%s\n' % (MyDate,MyTime,addr[0], p.DnsType,p.dominio,ip))
        logfile.close 
  except KeyboardInterrupt:
    print 'Finalizando'
    udps.close()
## end of http://code.activestate.com/recipes/491264/ }}}

An error in "gistfile1.py" and "Simple DNS server.py":

Server log:

$ sudo python2 dns.py 
pyminifakeDNS:: dom.query. 60 IN A 192.168.1.1
Respuesta: 127.0.0.1 -> Unknown -> test.ru. -> 192.168.1.1

Client log:

$ dig test.ru @127.0.0.1
;; Warning: Message parser reports malformed message packet.

; <<>> DiG 9.10.6 <<>> test.ru @127.0.0.1 -p 5555
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57386
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: Message has 16 extra bytes at end

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;test.ru.			IN	A
......

And there is no dns response

Retry with dig test.ru @127.0.0.1 +noedns