Add IPv6 support for DNSBL

Should have used the library but didn't want to experiement and posiibly break the includes

inc/functions.php

@@ -1753,9 +1753,6 @@ function buildJavascript() {
 function checkDNSBL() {
 	global $config;
 
-	if (isIPv6())
-		return; // No IPv6 support yet.
-
 	if (!isset($_SERVER['REMOTE_ADDR']))
 		return; // Fix your web server configuration
 
@@ -1765,7 +1762,11 @@ function checkDNSBL() {
 	if (in_array($_SERVER['REMOTE_ADDR'], $config['dnsbl_exceptions']))
 		return;
 
-	$ipaddr = ReverseIPOctets($_SERVER['REMOTE_ADDR']);
+	if (isIPv6()) {
+		$ipaddr = ReverseIPv6Octets($_SERVER['REMOTE_ADDR']);
+	} else {
+		$ipaddr = ReverseIPv4Octets($_SERVER['REMOTE_ADDR']);
+	}
 
 	foreach ($config['dnsbl'] as $blacklist) {
 		if (!is_array($blacklist))
@@ -1801,10 +1802,30 @@ function isIPv6() {
 	return strstr($_SERVER['REMOTE_ADDR'], ':') !== false;
 }
 
-function ReverseIPOctets($ip) {
+function ReverseIPv4Octets($ip) {
 	return implode('.', array_reverse(explode('.', $ip)));
 }
 
+function ReverseIPv6Octets($ip) {
+	return strrev(implode(".", str_split(str_replace(':', '', inet_expand($ip)))));
+}
+
+// copypastad from lib/IP/Lifo/IP.php, TODO replace this with a proper include
+function inet_expand($ip)
+{
+	// strip possible cidr notation off
+	if (($pos = strpos($ip, '/')) !== false) {
+		$ip = substr($ip, 0, $pos);
+	}
+	$bytes = unpack('n*', inet_pton($ip));
+	if (count($bytes) > 2) {
+		return implode(':', array_map(function ($b) {
+			return sprintf("%04x", $b);
+		}, $bytes));
+	}
+	return $ip;
+}
+
 function wordfilters(&$body) {
         global $config;