Support » Plugin: WordPress MU Domain Mapping » [Plugin: WordPress MU Domain Mapping] infinite loop, and HTTP header controls

  • We use domain mapper extensively and found a glitch when combined with caching.

    It caches the script …
    < $cript src='{$protocol}{$current_site->domain}{$current_site->path}?dm={$hash}&action=load&blogid={$current_blog->blog_id}&siteid={$current_blog->site_id}&t=" . mt_rand() . "&back=" . urlencode( $protocol . $current_blog->domain . $_SERVER[ 'REQUEST_URI' ] ) . "' type='text/javascript'></ $cript> //changed for HTML safety

    … on pages and forces Admins through an infinite redirect loop.

    We have 2 fixes for this.

    Preferably, somewhere, log the dm={$hash} and t=mt_rand() combination temporarily so that dm+time -code is used only once and then ignored in future iterations preventing the loop. If dm=x & t=y gets generated on a page, the first person to use it is sent the redirect (log its use at that time). Then, all people who hit the cached page, will call that script and it will be found as a duplicate in the logs, and they will NOT be sent the redirect again.

    As a temporary fix:
    We are currently using cookies in a modified remote_login_js() :

    $wpdb->query( $wpdb->prepare( "INSERT INTO {$wpdb->dmtablelogins} ( 'id', 'user_id', 'blog_id', 't' ) VALUES( %s, %d, %d, NOW() )", $key, $current_user->ID, $_GET[ 'blogid' ] ) );
    $url = add_query_arg( array( 'action' => 'login', 'dm' => $hash, 'k' => $key, 't' => mt_rand() ), $_GET[ 'back' ] );
    setcookie('dmredirect', 'recent', time()+5, '/'); //stop login redirects for 5 seconds//
    header("Cache-Control: no-cache, must-revalidate", true);  //prevent caching this script.
    echo "window.location = '$url'";


    Then above that, in the begining of the function, we made a few more changes.
    It is not proper code to just ‘exit’ php. A 204 SHOULD be returned indicating no content. This is also where I put my code looking for the cookie to prevent redirects:

    if ( !is_user_logged_in() ) {
      header('HTTP/1.0 204 No Content', true, 204); //tell them nothing
    //if recently redirected, halt the process and discontinue
    if($_COOKIE['dmredirect'] == 'recent'){
      header('HTTP/1.0 204 No Content', true, 204);

    So this corrects the empty pages being returned with a http status 200,
    prevents an infinite loop from cached pages with a cookie
    and uses Cache-Control headers to prevent caching of dynamically generated scripts.

    Instead of the cookie solution, we would like to see a DB-logging of redirects on dm= and t= to prevent people getting the cached redirect.
    That way they don’t receive the first redirect in order to set a cookie to stop it the 2nd time.


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  • Not sure if that is the right place to post that?

    🙂 Sorry way above my head. But I am taking note, “possible complication when domain mapping is combined with caching.” Anyone doing domain mapping is aiming at a substantial site, so probably is going to consider caching, so this sounds of interest! Hope you get more interest eventually from people of expertise.

    (Maybe you should try the “Hacks” subforum? I don’t know. Currently I am just struggling with my first attempt at domain mapping.)

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