#!/usr/pkg/bin/python
"""fake DNS server for internet cafe lockdown

   this is for use in a situation where you only want certain people
   to have access to the gateway, but everyone can reach the local net.
   this returns the same IP for every name lookup. of course, this
   doesn't help against smart-alecks who know what IP they want to
   visit, so you have to play with the routing also."""

Copyright = """
    fakebind -- return chosen IP for every name lookup
    Copyright (C) 2004  John Comeau <jc@jcomeau.com>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
    """
errormessage = "Not all needed libraries found, upgrade or check path"
try:
 True # not defined in older Python releases
except:
 True, False = 1, 0
try:
 import sys, os, types, re, pwd
 sys.path.append(os.sep.join([pwd.getpwuid(os.geteuid())[5], 'lib', 'python']))
 from com.jcomeau import gpl, jclicense
except:
 try:
  sys.stderr.write("%s\n" % errormessage)
 except:
  print errormessage
 raise

# get name this program was called as
self = sys.argv[0].split(os.sep)[-1]
command = self.split('.')[0]  # chop any suffix (extension)
# now get name we gave it when we wrote it
originalself = Copyright.split()[0]

# globals and routines that should be in every program
# (yes, you could import them, but there are problems in that approach too)

def DebugPrint(*whatever):
 return False  # defined instead by pytest module, use that for debugging

# other globals, specific to this program
from socket import *

def serve():
 """listen for DNS queries and answer...

    our answers don't have to match any reality but our own
    all dns questions and answers have 5 fields, some of which are often
    empty: header, question, answer RRs, authority RRs, additional RRs, where
    RR is Resource Record; see RFC 1035 for specifics
 """
 dns_port = getservbyname('domain', 'udp')
 udplistener = socket(AF_INET, SOCK_DGRAM)
 try:
  udplistener.bind(('0.0.0.0', dns_port))  # note double parens, must be tuple
 except:
  dns_port = dns_port + 1024  # set to non-privileged port number
  udplistener.bind(('0.0.0.0', dns_port))
  sys.stderr.write('Using unprivileged port %d\n' % dns_port)
 sys.stderr.write('Fake DNS server listening\n')
 while True:
  request = udplistener.recv(1024)
  DebugPrint(request)

def dns_header():
 pass

if __name__ == '__main__':
 # if this program was imported by another, the above test will fail,
 # and this following code won't be used...
 serve()
else:
 # if you want something to be done on import, do it here; otherwise pass
 pass