From: Tomas Mudrunka <tomas@mudrunka.cz>
Date: Wed, 7 Oct 2020 20:13:20 +0000 (+0200)
Subject: ipv6 wildcard code
X-Git-Url: http://git.harvie.cz/?p=mirrors%2FPrograms.git;a=commitdiff_plain;h=85bedcf1a82b8f35ec66de1960b618f554d74181

ipv6 wildcard code
---

diff --git a/php/ipv6wildcard.php b/php/ipv6wildcard.php
new file mode 100644
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");
+}