+/* Hint for implementing progress messages for uploaded/incoming data.
+ * The caller sets this to a value > 0 if it knows or can estimate how
+ * much data will be sent (this is not always known, eg. for uploads
+ * coming from a pipe). If this is known then we can emit progress
+ * messages as we write the data.
+ */
+uint64_t progress_hint;
+
+/* Optional arguments bitmask. Caller sets this to indicate which
+ * optional arguments in the guestfs_<foo>_args structure are
+ * meaningful. Optional arguments not covered by the bitmask are set
+ * to arbitrary values and the daemon should ignore them. If the
+ * bitmask has bits set that the daemon doesn't understand, then the
+ * whole call is rejected early in processing.
+ */
+uint64_t optargs_bitmask;
+