-int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length) _sd_hidden_;
+int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length);
+
+/*
+ Helper call for identifying a passed file descriptor. Returns 1 if
+ the file descriptor is a POSIX Message Queue of the specified name,
+ 0 otherwise. If path is NULL a message queue name check is not
+ done. Returns a negative errno style error code on failure.
+*/
+int sd_is_mq(int fd, const char *path);