ipv6 wildcard code

diff --git a/php/ipv6wildcard.php b/php/ipv6wildcard.php
new file mode 100644 (file)
index 0000000..15c3ad5
--- /dev/null
+++ b/php/ipv6wildcard.php
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * Given IPv6 address and prefix creates array of * wildcard suffixed
+ * addresses to be used for as reverse DNS records
+ */
+function ipv6_prefix2wildcards($address, $prefix) {
+
+       //Parse ip and prefix
+       echo("IPv6 prefix: ".$address."/".$prefix."\n");
+       $addr = inet_pton ($address);
+       $pref = $prefix;
+       $a = gmp_import($addr);
+
+       //Separate maskable octets
+       $pref_hex = ceil($pref / 4)*4; //Prefix rounded up to full octets
+       $pref_rem = $pref_hex - $pref; //Remainder of prefix
+       echo("Rounding prefix: ".$pref_hex."-".$pref_rem."\n");
+
+       $a = gmp_div_q($a, gmp_pow(2,128-$prefix)); //Truncate to just prefix
+       $a = gmp_mul($a, gmp_pow(2,$pref_rem)); //Fill remaining bits in last wildcard octet with zeros
+
+       //Generate wildcards
+       $wildcards = [];
+       for($i = 0; $i < (2**$pref_rem) ; $i++) {
+               //echo("ADDED: ".$i." = ".decbin($i)."\n");
+               $ap = gmp_or($a, gmp_init($i));
+               $wildcards[] = $ap;
+       }
+
+       return $wildcards;
+}
+
+if(isset($argv[2])) {
+       $wcs = ipv6_prefix2wildcards($argv[1],$argv[2]);
+} else {
+       $wcs = ipv6_prefix2wildcards('2001:1:3::10', 67);
+}
+
+echo("\n");
+foreach($wcs as $w) {
+  //echo(gmp_strval($w, 2)."* :-)\n");
+  echo(gmp_strval($w, 16)."*\n");
+}