+#define NBD_CMD_MASK_COMMAND 0x0000ffff
+#define NBD_CMD_FLAG_FUA (1<<16)
+
+/* values for flags field */
+#define NBD_FLAG_HAS_FLAGS (1 << 0) /* Flags are there */
+#define NBD_FLAG_READ_ONLY (1 << 1) /* Device is read-only */
+#define NBD_FLAG_SEND_FLUSH (1 << 2) /* Send FLUSH */
+#define NBD_FLAG_SEND_FUA (1 << 3) /* Send FUA (Force Unit Access) */
+#define NBD_FLAG_ROTATIONAL (1 << 4) /* Use elevator algorithm - rotational media */
+