#!/usr/bin/perl
#
#                       IP-UPDATE - Update Dynamic DNS
#                             November 2000
#
# Query the LinkSys router to determine the currently assigned DHCP
# address. Then send an update to the Dynamic DNS server at JustLinux.com
# if it's changed from the last time.
#
  if ($ARGV[0] eq "-h") {
     print STDERR "Usage: ip-update.pl [-v | -h]\n";
     exit;
  }
#
# JustLinux settings
#
  $USER_ID="your_ID";
  $PASSWORD="your_password";
  $DNSID="your_dynsid";
#
#      Get current IP address
#
  $_ = `lynx -dump http://192.168.1.1/Status.htm`;
  s/IP Address:/ip address/;  # Skip first entry
  if (/IP Address: (.*)/) {
     $newip = $1;
  } else {
     print STDERR "Failure, couldn't get new IP address\n$_\n";
     exit;
  }
  if ($ARGV[0] eq "-v") {
     print "Current  IP address: $newip\n";
  }
#
#      Get old IP address
#
  if (-e "/tmp/old-ip") {
     if (open(OLD,"/tmp/old-ip")) {
        $oldip = <OLD>;
        $oldip =~ tr/\n\r//d;
        close(OLD);
        if ($ARGV[0] eq "-v") {
           print "Previous IP address: $oldip\n";
        }
     } else {
        print STDERR "Error: /tmp/old-ip exists, but I can't read from it: $!\n";
        exit;
     }
  } else {
     if ($ARGV[0] eq "-v") {
        print "No previous IP address, updating.\n";
     }
  }
#
#      Compare and update
#
  if (($oldip eq "") || ($newip ne $oldip)) {
     if (open(OLD,">/tmp/old-ip")) {
        print OLD $newip,"\n";
        close(OLD);
     } else {
        print STDERR "Couldn't update /tmp/old-ip: $!\n";
     }
  }
#
#      Update DNS server
#
  if ($oldip ne $newip) {
     $url1 = "-accept_all_cookies http://www.justlinux.com/bin/dologin?username=$USER_ID&password=$PASSWORD"
;
     `lynx -dump $url1`;    # Get a cookie(?)
     if ($? == 0) {
        $url2 = "http://www.justlinux.com/bin/controlpanel/dyndns/update.pl?dnsid=$DNSID&ip=$newip&action=up
date";
        `lynx -dump $url2`;
     }
     if ($? != 0) {
        $rc = $? / 256;
        print STDERR "Return code: $rc from Lynx\n$s\n";
        exit;
     }
     `logger IP-UPDATE: IP address changed to $newip... updating DNS`;
     if ($ARGV[0] eq "-v") {
        print "Updating 'justlinux'\n";
        print "lynx -dump $url1\n";
        print "lynx -dump $url2\n";
     }
  }