#!/usr/bin/perl

$WGET = "/usr/bin/wget";
$NSUPDATE = "/usr/bin/nsupdate";
$MAILTO ="your\@mail.address";
$MAIL = "/usr/sbin/sendmail $MAILTO";
$KEY = "KEY FILE";
$DOMAIN = "Your.Domain.";
$PREREQ ="prereq yxrrset $DOMAIN IN A\n";
$DELETE ="update delete $DOMAIN IN A\n";
$ADD = "update add $DOMAIN 300 IN A ";
open(IP,"$WGET -q --http-user='admin' --http-passwd='******' -O '-' 'http://MODEM_ADDRESS/info_main.html' | ");

while(<IP>){
  if( $_ =~  /<TD><LABEL\sonMouseOver=msgShow\(event\,11\)\sonMouseOut=msgHide\(\)>WAN‘¤\sIPƒAƒhƒŒƒX<\/LABEL><\/TD>/){
    $html = <IP>;
    if ( $html =~ /<TD>(\d*\.\d*\.\d*\.\d*)\S*\s*<\/TD>/ ){
    $now_ip = $1;
    $addr = (gethostbyname('doragon2.net'))[4];
    $addr = sprintf("%u.%u.%u.%u", unpack("C*", $addr));
    if ( $now_ip ne $addr ){
      print("$now_ip : $addr \n");
      $nsword = "$PREREQ $DELETE $ADD $now_ip\n\n";
      system("echo \'$nsword\' | $NSUPDATE -k $KEY");
      system("echo \'$now_ip\' | $MAIL ");
    }
    }
  }
}