php/ipv6wildcard.php

   1 <?php
   2
   3 /**
   4  * Given IPv6 address and prefix creates array of * wildcard suffixed
   5  * addresses to be used for as reverse DNS records
   6  */
   7 function ipv6_prefix2wildcards($address, $prefix) {
   8
   9         //Parse ip and prefix
  10         echo("IPv6 prefix: ".$address."/".$prefix."\n");
  11         $addr = inet_pton ($address);
  12         $pref = $prefix;
  13         $a = gmp_import($addr);
  14
  15         //Separate maskable octets
  16         $pref_hex = ceil($pref / 4)*4; //Prefix rounded up to full octets
  17         $pref_rem = $pref_hex - $pref; //Remainder of prefix
  18         echo("Rounding prefix: ".$pref_hex."-".$pref_rem."\n");
  19
  20         $a = gmp_div_q($a, gmp_pow(2,128-$prefix)); //Truncate to just prefix
  21         $a = gmp_mul($a, gmp_pow(2,$pref_rem)); //Fill remaining bits in last wildcard octet with zeros
  22
  23         //Generate wildcards
  24         $wildcards = [];
  25         for($i = 0; $i < (2**$pref_rem) ; $i++) {
  26                 //echo("ADDED: ".$i." = ".decbin($i)."\n");
  27                 $ap = gmp_or($a, gmp_init($i));
  28                 $wildcards[] = $ap;
  29         }
  30
  31         return $wildcards;
  32 }
  33
  34 if(isset($argv[2])) {
  35         $wcs = ipv6_prefix2wildcards($argv[1],$argv[2]);
  36 } else {
  37         $wcs = ipv6_prefix2wildcards('2001:1:3::10', 67);
  38 }
  39
  40 echo("\n");
  41 foreach($wcs as $w) {
  42   //echo(gmp_strval($w, 2)."* :-)\n");
  43   echo(gmp_strval($w, 16)."*\n");
  44 }