I was reading about the security problems with IE and dotless IP addresses and decided to write a little conversion script for dotless ips (have I just reinvented the wheel?). My script converts to the dotless IP just fine, but when it converts back, the last octet is one lower than it should be. What did I do wrong?

#!D:/perl/bin/perl.exe -w
use strict;
use Socket;

my $domain = shift or die "Usage: $0 [domain]\n[domain] should *not* i
+nclude the protocol (e.g. http://)";
my $address = inet_ntoa( inet_aton( $domain ) );
print "Original ip: $address\n";

my $dotless = ip_to_dotless( $address );
print "Dotless ip:  $dotless\n";

my $orig_address = dotless_to_ip( $dotless );
print "Original ip: $orig_address";

sub ip_to_dotless {
    my $ip      = shift;
    my $index   = 3;
    my $dotless = 0;
    $dotless += $_ * ( 256 ** $index-- ) foreach ( split /\./, $ip );
    return $dotless;
}

sub dotless_to_ip {
    use integer;
    my $dotless = shift;
    my $index   = 3;
    my @ip      = ();
    
    while ( @ip < 4 ) {
        my $temp = 256 ** $index--;
        push @ip, $dotless / $temp;
        $dotless -= $ip[ -1 ] * $temp;
    }
    @ip = map { $_ + 255 } @ip;
    return join '.', @ip;
}

[download]

You can read about dotless IPs here if you're not familiar with this.

My output is as follows:

C:\>test.pl www.yahoo.com
Original ip: 216.115.102.78
Dotless ip:  3631441486
Original ip: 216.115.102.77

C:\>test.pl www.perlmonks.org
Original ip: 206.170.14.76
Dotless ip:  3467251276
Original ip: 206.170.14.75

[download]

Cheers,
Ovid

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In reply to Dotless IP address problem by Ovid

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