acquia ip_address()

gistfile1.php

// Code provided by Acquia.
// Non balanced servers (dev and stage) don't have this problem.
if (!empty($conf['reverse_proxy_addresses'])) {
  $ips = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
  $ips = array_map('trim', $ips);
  // Add REMOTE_ADDR to the X-Forwarded-For list (the ip_address function will
  // also do this) in case it's a 10. internal AWS address; if it is we should
  // add it to the list of reverse proxy addresses so that ip_address will
  // ignore it.
  $ips[] = $_SERVER['REMOTE_ADDR'];
  // Work backwards through the list of IPs, adding 10. addresses to the proxy
  // // list but stop at the first non-10. address we find.
  $ips = array_reverse($ips);
  foreach ($ips as $ip) {
    if (strpos($ip, '10.') === 0) {
      if (!in_array($ip, $conf['reverse_proxy_addresses'])) {
        $conf['reverse_proxy_addresses'][] = $ip;
      }
    } else { // we hit the first non-10. address, so stop.
      break;
    }
  }
}