+/**
+ * The filter function of a stream might want to modify the message
+ * before passing it to the handler and/or substreams. In this case,
+ * the filter should make a local copy of `struct log_msg`, call
+ * @log_pass_filtered() on it and return true, so that the original
+ * message will not be processed any further.
+ **/
+void log_pass_filtered(struct log_stream *ls, struct log_msg *m);
+