Get IPv6 address for MAC on PFSense

ip_list.php

<?php

/* ip_list.php
 *
 * Copyright (c) 2022 Tyler Szabo
 * All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* 
 * Example Usage: https://localhost/ip_list.php?mac=00:09:8c:00:69:63
 */

define('NDP_COMMAND', '/usr/sbin/ndp -n -a');
define('REGEX_GLOBAL_IPV6_IP', '[23][[:xdigit:]][[:xdigit:]][[:xdigit:]]:[[:xdigit:]:]*');
define('REGEX_MAC_ADDR', '[[:xdigit:]:]*');
define('QS_MAC', 'mac');

header("Content-type: text/plain");

$valid_client = false;
$ip = $_SERVER['REMOTE_ADDR'];
if ($ip == "127.0.0.1" or $ip == "::1") {
  $valid_client = true;
}

if (!$valid_client) {
  header($_SERVER['SERVER_PROTOCOL'] . ' 403 Forbidden');
  echo "403 Forbidden\n";
  exit;
}

$gen_date = gmdate("D, j M Y H:i:s") . " GMT";
header("Last-Modified: " . $gen_date);

exec(NDP_COMMAND, $ndp_output);

$mac = $_GET[QS_MAC];

echo "## IPv6 neighbors for " . $mac . "\n";
echo "## Generated " . $gen_date . "\n";
foreach ($ndp_output as $line) {
  //echo "# " . $line . "\n";
  
  preg_match('/^(?P<ipv6>'.REGEX_GLOBAL_IPV6_IP.') (?P<mac>'.REGEX_MAC_ADDR.')/', $line, $matches);

  if ($matches['mac'] == $mac) {
    echo $matches['ipv6'] . "\n";
  }
}
echo "## End\n";

?>