webtv server routes script

routes.py

#!/usr/bin/env python3

import os
import subprocess

## Change me!
ServerIP = '74.76.120.18' # MattMan
#ServerIP = '51.222.164.146' # Zefie

DNSServer = '9.9.9.9' # quad9.net
#DNSServer = '1.1.1.1' # cloudflare-dns.com
#DNSServer = '8.8.8.8' # dns.google
#DNSServer = '208.67.222.222' # use.opendns.com

## Don't change me!
tmppath = '/tmp/routes.txt'

ipranges = [
    '10.0.0.1', # US Production
    '10.0.0.2', 
    '10.0.1.1', 
    '10.0.1.2', 
    '10.0.1.3', 
    '10.0.1.4', 
    '10.0.128.1', # US Daily
    '10.0.1.129', # Japanese Dreamcast
    '10.0.128.2', 
    '10.0.129.1', 
    '10.0.129.2', 
    '10.0.130.1', 
    '10.0.130.2', 
    '10.0.131.1', 
    '10.0.131.2', 
    '10.0.132.1', 
    '10.0.132.2', 
    '209.240.192.0/19', # US WebTV IP address range
    '204.254.74.126', # listed on ConnectSetup page
    '210.150.22.37', # JP WebTV Service
    '210.150.22.58', # JP WebTV Service
]   

for ip in ipranges:
    if os.path.isfile(tmppath): # this file existing means we already set routes
        oldip = open(tmppath, 'r').read().strip()
        # purge old routes without clearing all rules
        try:
            subprocess.check_output(['iptables', '-t', 'nat', '-D', 'PREROUTING', '-d', ip, '-j', 'DNAT', '--to-destination', oldip])
        except Exception as e:
            pass
        try:
            oip = ip
            if oip == '209.240.192.0/19':
                oip = '209.240.192.0-209.240.223.255'
            x = subprocess.check_output(['iptables', '-t', 'nat', '-D', 'POSTROUTING', '-d', oldip, '-j', 'SNAT', '--to-source', oip])
        except Exception as e:
            pass
    # add routes
    oldip = open(tmppath, 'w').write(ServerIP)
    subprocess.check_output(['iptables', '-t', 'nat', '-A', 'PREROUTING', '-d', ip, '-j', 'DNAT', '--to-destination', ServerIP])
    if ip == '209.240.192.0/19': ip = '209.240.192.0-209.240.223.255'
    subprocess.check_output(['iptables', '-t', 'nat', '-A', 'POSTROUTING', '-d', ServerIP, '-j', 'SNAT', '--to-source', ip])

# special route for DNS server
subprocess.check_output(['iptables', '-t', 'nat', '-A', 'PREROUTING', '-d', '157.57.221.51', '-j', 'DNAT', '--to-destination', DNSServer])
subprocess.check_output(['iptables', '-t', 'nat', '-A', 'POSTROUTING', '-d', DNSServer, '-j', 'SNAT', '--to-source', '157.57.221.51'])