Switch the proxy automatically

ipaddr.php

<?php
    echo $_SERVER["REMOTE_ADDR"];

ssh-autoproxy.py

#!/usr/bin/python
#
# ssh-autoproxy.py : Switch the proxy automatically
#
# When you are in the inside of a firewall, I connect to the server
# directly. But you are in the outside of a firewall, I connect to the
# server over proxy.
#
# Usage:
#   $HOME/.ssh/config:
#
#     # foo.example.com need to connect via proxy.example.com
#     # if you are in the outside of 192.0.2.0/24 or 198.51.100.0/24
#     Host foo
#       HostName foo.example.com
#       ProxyCommand ssh-autoproxy.py proxy.example.com %h %p 192.0.2.0/24 198.51.100.0/24
#
#
# ipaddr::branches/3144 is needed. Stable version of ipaddr is not
# suitable for pep 3144
# @see http://code.google.com/p/ipaddr-py/wiki/Using3144
#

import ipaddr
import urllib2
import subprocess
import argparse

def get_wan_ip(check_url = "http://yunazuno.net/misc/ipaddr/ipaddr.php"):
    """Get the own global IP address

    Get the own global IP address via specific url.
    """
    handle = urllib2.urlopen(check_url, timeout=2)
    data = handle.read(16)

    try:
        wanip = ipaddr.ip_address(data)
    except ValueError:
        wanip = ipaddr.ip_address("0.0.0.0")

    return wanip

def is_inside_network(networks):
    wanipaddr = get_wan_ip()

    is_inside = False
    for network_str in networks:
        network = ipaddr.ip_network(network_str)
        if wanipaddr in network:
            is_inside = True
            break

    return is_inside

def main():
    ## Parse arguments
    parser = argparse.ArgumentParser()
    parser.add_argument("proxy", help="proxy")
    parser.add_argument("hostname", help="hostname")
    parser.add_argument("port", help="port")
    parser.add_argument('network', nargs='+', default=[],
                        help="Networks")
    args = parser.parse_args()

    networks = args.network
    proxy = args.proxy
    hostname = args.hostname
    port = args.port

    ## Check the wan ipaddr: is inside or not
    is_inside = is_inside_network(networks)

    ## connect
    if is_inside:
        # connect directly
        cmd = "nc {0} {1}".format(hostname, port)
    else:
        # connect over proxy
        cmd = "ssh {0} nc {1} {2}".format(proxy, hostname, port)

    subprocess.call(cmd, shell=True)

    return

if __name__ == '__main__':
    main()