Add bin/check-dns.php script

Author: carlbennett

bin/check-dns.php

@@ -0,0 +1,64 @@
+#!/usr/bin/env php
+<?php /* vim: set colorcolumn=: */
+/**
+ * @project bnetdocs-web <https://github.com/BNETDocs/bnetdocs-web/>
+ *
+ * Dec 5 2020 - Resolve DNS entries from JSON input to A/AAAA/CNAME records, intended to be piped from bin/discover-dns.php.
+ */
+declare(strict_types=1);
+
+$user_input = file_get_contents('php://stdin');
+$json = json_decode($user_input);
+
+if (json_last_error() !== 0)
+{
+  die('json error, check input');
+}
+
+$scan = $json;
+while ($scan)
+{
+  $scan = do_scan($scan);
+  echo PHP_EOL;
+}
+
+function do_scan($names)
+{
+  $late_scan = [];
+
+  foreach ($names as $name)
+  {
+    $record_a = dns_get_record($name, DNS_A);
+    $record_aaaa = dns_get_record($name, DNS_AAAA);
+    $record_cname = dns_get_record($name, DNS_CNAME);
+    $records = array_merge($record_a ?? [], $record_aaaa ?? [], $record_cname ?? []);
+
+    if (count($records) == 0)
+    {
+      printf("%s: %s", $name, PHP_EOL);
+    }
+    else
+    {
+      $ips = [];
+      foreach ($records as $record)
+      {
+        if (isset($record['ip']))
+        {
+          $ips[] = $record['ip'];
+        }
+        else
+        {
+          $ips = ['-> ' . $record['target']];
+          if (in_array($record['target'], $names))
+          {
+            $late_scan[] = $record['target']; // add the alias
+          }
+        }
+      }
+      sort($ips);
+      printf("%s: %s%s", $name, implode(' ', $ips), PHP_EOL);
+    }
+  }
+
+  return $late_scan;
+}