x-forwarded-proto + F5 + Drupal issues

Check to make sure they did not enable x-forwarded-for on the HTTP F5 virtual server that the application uses. If you enable HTTPS in drupal only when the x-forwarded-for header is set, then enabling x-forwarded-for on the http virtual server on the f5 (which is a normal thing to do) could cause undesirable application effects

Also, as I am unfamiliar with drupal, what does "$_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https'" do? the contents of a legitimate x-forwarded-for header will never contain the text "https"