#! /usr/bin/perl

# UpdateDynDNS.pl -- Dynamic DNS Updater for DynDNS.org.
# Copyright (c) 2002-2004 Tudor Hulubei.
# Improved by Dan Lipsa to support 3Com routers.
# Distributed under the GNU GPL.

# 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, 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.  */

# This script parses the "Status" web page of a LinkSys router,
# gathers the IP address and then feeds it to the dyndns.org server
# taking care of dynamic dns registration, allowing a home machine to
# be named something like 'hulubei.homeip.net'.  The script needs to
# be executed every hour or so from cron so that it detects any change
# in the IP address of the router and properly updates the dyndns.org
# database.


use LWP::UserAgent;
use HTTP::Request;
use MIME::Base64;
use File::stat;

my $g_program = $0;
my $g_name = "UpdateDynDNS";
my $g_version = "0.0.4";

# USER CONFIGURABLE PARAMETERS!
# NOTE: Since these include passwords, we don't want them
# as command line parameters.  At least I don't.
my $g_debug = 0; # Set to 1 to enable debug messages.
my $g_test = 0; # Set to 1 to activate test mode.
my $configFile = "/etc/dyndns.conf";
my $g_routerInternalIP = "192.168.1.1";
my $g_routerUsername = $g_test ? "root" : "root";
my $g_routerPassword = $g_test ? "admin" : "********";
my $g_dyndnsUsername = $g_test ? "test" : "YourAccount";
my $g_dyndnsPassword = $g_test ? "test" : "YourPassword";
my $g_email = $g_test ? "test\@test.net" : "you\@whatever.net";
my $g_hostname = $g_test ? "test.homeip.net" : "machine.homeip.net";
# Valid values for router are: "linksys" & "3com".
# These values are _not_ autodetected.
my $g_router = $g_test ? "test" : "linksys";
# END OF USER CONFIGURABLE PARAMETERS!


sub getIpPageRequestLinksys($)
{
    my ($ua) = @_;
    my $routerAuthentication = encode_base64
	("$g_routerUsername:$g_routerPassword");
    chomp $routerAuthentication;

    # Grab the 'Status.htm' page from the LinkSys router/switch.
    # Is this piece of crap running Windows?
    # What's with the ".htm" extension?
    my $routerHeader = HTTP::Headers->new
	("Authorization" => "Basic $routerAuthentication",
	 "Content_Type" => "text/plain; version=3.2");

    my $routerURI = "http://$g_routerInternalIP/Status.htm";
    return $request = HTTP::Request->new("GET", $routerURI, $routerHeader);
}


sub getIpPageRequest3Com($)
{
    my ($ua) = @_;
    # Log in.
    my $time = time();
    my $routerURI = "http://$g_routerInternalIP/login.htm?GetTimeVal=$time&page=login&URL=$g_routerPassword";
    my $request = HTTP::Request->new("POST", $routerURI);
    print "\n" . $request->as_string() if ($g_debug);
    my $response = $ua->request($request);

    if (!$response->is_success())
    {
	print $response->error_as_HTML if ($g_debug);
	die "\n$g_program: failed to get router IP";
    }

    # Get the IP page.
    my $routerURI = "http://$g_routerInternalIP/main/status_admin.htm";
    return $request = HTTP::Request->new("GET", $routerURI);
}


sub getIpPageRequest($)
{
  my ($ua) = @_;

  if ($g_router eq "linksys")
  {
      return getIpPageRequestLinksys($ua);
  }
  elsif($g_router eq "3com")
  {
      return getIpPageRequest3Com($ua);
  }
  else
  {
      die "Invalid router name";
  }
}


sub routerExternalIP()
{
    print "Detecting ", $g_router, "'s WAN IP address...";
    my $ip = "";
    my $ua = LWP::UserAgent->new;

    my $request = getIpPageRequest($ua);
    print "\n" . $request->as_string() if ($g_debug);
    my $response = $ua->request($request);

    if (!$response->is_success())
    {
	print $response->error_as_HTML if ($g_debug);
	die "\n$g_program: failed to get router IP";
    }

    $_ = $response->content();
    chomp $_;
    while (s/([012]?[0-9]?[0-9]\.[012]?[0-9]?[0-9]\.[012]?[0-9]?[0-9]\.[012]?[0-9]?[0-9])//)
    {
	# LinkSys shows first the IP address, then the netmask, the
	# default gateway, and finally the DNS servers.  We assume
	# that the IP is the first valid address that we get here,
	# unfortunately.
	next if ($1 =~ /255\.255\./);
	next if ($1 =~ /192\.168\./);
	next if ($1 =~ /0\.0\./);
	$ip = $1;
	last;
    }

    die "\n$g_program: failed to get router IP" if ("$ip" == "");
    print " $ip\n";
    return "$ip";
}


sub externalIP()
{
    # WARNING: This is a pathetic attempt at figuring out the current
    # machine's IP address.  You may need to adjust it if your Linux
    # ifconfig is outputing information in a different format.  In
    # addition to that, this makes the simplistic assumption that you
    # only have one ethernet card.  Being the geek that you are, you
    # probably have 3. :-)
    print "Detecting dynamic DNS configuration...";
    my $ip = `/sbin/ifconfig eth0 | grep inet | cut -d: -f2 | cut -d' ' -f1`;

    if ($ip =~ /^192.168/)
    {
	# eth0 has an IP in the reserved range.  We're probably behind
	# a router of some sort.
	print " Computer->Router->Modem->Internet\n";
	return routerExternalIP();
    }
    else
    {
	# We have a real world address.
	print " Computer->Modem->Internet\n";
	return $ip;
    }
}


sub usage()
{
    print "$g_name version $g_version\n";
    print "Copyright (c) 2002-2003 Tudor Hulubei\n";
}


sub updateDynDNS($$)
{
    my ($hostname, $externalIP) = @_;

    my $dyndnsAuthentication = encode_base64("$g_dyndnsUsername:$g_dyndnsPassword");
    chomp $dyndnsAuthentication;
    my $ua = LWP::UserAgent->new;
    print "Updating IP address for $g_hostname...";
    my $dyndnsHeader = HTTP::Headers->new(
	"Host" => "members.dyndns.org",
	"Authorization" => "Basic $dyndnsAuthentication",
	"User-Agent" => "$g_program/1.0 $g_email",
	"Content_Type" => "text/html; version=3.2");
    my $dyndnsURI =
	"http://members.dyndns.org/nic/update?" .
	"system=dyndns&" .
	"hostname=$g_hostname&" .
	"myip=$externalIP&" .
	"wildcard=OFF&" .
	"mx=localhost&" .
	"backmx=NO&" .
	"offline=NO " .
	"HTTP/1.0";

    my $request = HTTP::Request->new("GET", $dyndnsURI, $dyndnsHeader);
    print "\n" . $request->as_string() if ($g_debug);
    my $response = $ua->request($request);

    if (!$response->is_success())
    {
	print $response->error_as_HTML if ($g_debug);
	die "$g_program: failed to set IP address $externalIP for $g_hostname\n"
    }

    print " done (" . $response->content . ")\n";
}


usage();

# The IP address needs to be updated _ONLY_ if it changed, or if 28
# days have passed.  Anything else would be considered an abuse and
# the hostname will be disabled.
my $sb = stat($configFile);
my $externalIP = externalIP();
my $previousExternalIP = `cat $configFile 2>/dev/null`;
if ($? != 0 || ($externalIP . "\n") ne $previousExternalIP ||
    time() - $sb->mtime > (28 * 24 * 60 * 60))
{
    updateDynDNS($g_hostname, $externalIP);
    `echo $externalIP > $configFile`;
}

exit 0;