Match IPv4 address given IP range/mask?

Question

Either with PHP or a RegExp (or both), how do I match a range of IP addresses?

Sample Incoming IPs

10.210.12.12
10.253.12.12
10.210.12.254
10.210.1         


        

Answer 1

I've improved on the above example (I have a netmask with /29 so it doesn't work).

function check_netmask($mask, $ip) {
    @list($net, $bits) = explode('/', $mask);
    $bits = isset($bits) ? $bits : 32;
    $bitmask = -pow(2, 32-$bits) & 0x00000000FFFFFFFF;
    $netmask = ip2long($net) & $bitmask;
    $ip_bits = ip2long($ip)  & $bitmask;
    return (($netmask ^ $ip_bits) == 0);
}

If you want to see it in action, add this:

print("IP Bits: " . str_pad(decbin(ip2long($ip)), 32, '0', STR_PAD_LEFT));
print "\n";
print("Bitmask: " . str_pad(decbin($bitmask), 32, '0', STR_PAD_LEFT));
print "\n";
print("Netmask: " . str_pad(decbin($netmask), 32, '0', STR_PAD_LEFT));
print "\n";
print("Match:   " . str_pad(decbin($netmask ^ $ip_bits), 32, '0', STR_PAD_LEFT));
print "\n";

Run it with something like this:

print var_dump(check_netmask($argv[1], $argv[2]));