+function akismet_pingback_forwarded_for( $r, $url ) {
+ static $urls = array();
+
+ // Call this with $r == null to prime the callback to add headers on a specific URL
+ if ( is_null( $r ) && !in_array( $url, $urls ) ) {
+ $urls[] = $url;
+ }
+
+ // Add X-Pingback-Forwarded-For header, but only for requests to a specific URL (the apparent pingback source)
+ if ( is_array( $r ) && is_array( $r['headers'] ) && !isset( $r['headers']['X-Pingback-Forwarded-For'] ) && in_array( $url, $urls ) ) {
+ $remote_ip = preg_replace( '/[^a-fx0-9:.,]/i', '', $_SERVER['REMOTE_ADDR'] );
+
+ // Note: this assumes REMOTE_ADDR is correct, and it may not be if a reverse proxy or CDN is in use
+ $r['headers']['X-Pingback-Forwarded-For'] = $remote_ip;
+
+ // Also identify the request as a pingback verification in the UA string so it appears in logs
+ $r['user-agent'] .= '; verifying pingback from ' . $remote_ip;
+ }
+
+ return $r;
+}
+
+function akismet_pre_check_pingback( $method ) {
+
+ if ( $method !== 'pingback.ping' )
+ return;
+
+ global $wp_xmlrpc_server;
+
+ if ( !is_object( $wp_xmlrpc_server ) )
+ return false;
+
+ // Lame: tightly coupled with the IXR class.
+ $args = $wp_xmlrpc_server->message->params;
+
+ if ( !empty( $args[1] ) ) {
+ $post_id = url_to_postid( $args[1] );
+
+ // If this gets through the pre-check, make sure we properly identify the outbound request as a pingback verification
+ akismet_pingback_forwarded_for( null, $args[0] );
+ add_filter( 'http_request_args', 'akismet_pingback_forwarded_for', 10, 2 );
+
+ $comment = array(
+ 'comment_author_url' => $args[0],
+ 'comment_post_ID' => $post_id,
+ 'comment_author' => '',
+ 'comment_author_email' => '',
+ 'comment_content' => '',
+ 'comment_type' => 'pingback',
+ 'akismet_pre_check' => '1',
+ 'comment_pingback_target' => $args[1],
+ );
+
+ $comment = akismet_auto_check_comment( $comment );
+
+ if ( isset( $comment['akismet_result'] ) && 'true' == $comment['akismet_result'] ) {
+ // Lame: tightly coupled with the IXR classes. Unfortunately the action provides no context and no way to return anything.
+ $wp_xmlrpc_server->error( new IXR_Error( 0, 'Invalid discovery target' ) );
+ }
+ }
+}
+
+// Run this early in the pingback call, before doing a remote fetch of the source uri
+add_action( 'xmlrpc_call', 'akismet_pre_check_pingback' );
+