How to match IPv6 addresses?

[frik]

Hello,

 

In my personal PHP application, I like to identify visitors to my website by checking the IP range

that their IP address falls into. This is easy enough for IPv4 when I have the CIDR.

For IPv6 however it is another matter entirely, because at present I don't know

how to match an IPv6 address. As a result I am using the cumbersome substr matching

approach, which does not work for many addresses.

 

For example, consider 2620:149:f01:2b0:99ad:f010:61c1:63c5.

The CIDR is 2620:149::/36. The 0 nybble in the 3rd 32-bit word is implied most of the time

and this breaks the substr approach.

 

Surely there is by now a simple way to do this.

Can someone tell me the best solution that exists at present?

 

Thanks.

 

[kicken]

You'll need to use GMP to store the addresses and compare against a given prefix. If your PHP build supports IPv6, you can use inet_pton to convert the human-readable address into a binary number. If you do not have IPv6 support, you will have to find or create your own parser for IPv6 addresses.

 

For example:

$address = '2620:149:f01:2b0:99ad:f010:61c1:63c5';
$network = '2620:149::/36';

$address = inet_pton($address);
$address = gmp_init(bin2hex($address), 16);

if (false !== $pos=strpos($network, '/')){
    $prefix = substr($network, 0, $pos);
    $bitlength = substr($network, $pos+1);
    $network = inet_pton($prefix);
    $network = gmp_init(bin2hex($network), 16);

    $mask = str_repeat('1', $bitlength).str_repeat('0', 128-$bitlength);
    $mask = gmp_init($mask, 2);
}
else {
    $network = inet_pton($prefix);
    $network = gmp_init(bin2hex($network), 16);

    $mask = str_repeat('1', 128);
    $mask = gmp_init($mask, 2);
}

$masked_address = gmp_and($address, $mask);
$masked_network = gmp_and($network, $mask);
if (gmp_cmp($masked_address, $masked_network) === 0){
    echo 'address is within the network.'.PHP_EOL;
}
else {
    echo 'address is not within the network.'.PHP_EOL;
}

[frik]

You'll need to use GMP to store the addresses and compare against a given prefix. If your PHP build supports IPv6, you can use inet_pton to convert the human-readable address into a binary number. If you do not have IPv6 support, you will have to find or create your own parser for IPv6 addresses.

 

 

 

OK, that helps. Thanks.