[Libguestfs] [nbdkit PATCH 01/10] protocol: Add NBD_INFO_INIT_STATE extension

[Eric Blake]

The NBD protocol is adding an extension to make it possible for
servers to advertise to the client if the export is known to start
life as a sparse file or with all-zero state.  Although this extension
is optional, clients can take advantage of it during certain
operations (such as making image copying more efficient by not having
to request a pre-zeroing pass).  This patch exposes the constants that
will be used by nbdkit, as well as shared in libnbd for client side
use.

Signed-off-by: Eric Blake <eblake at redhat.com>
---
 common/protocol/nbd-protocol.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/common/protocol/nbd-protocol.h b/common/protocol/nbd-protocol.h
index df0b4c6..50531a0 100644
--- a/common/protocol/nbd-protocol.h
+++ b/common/protocol/nbd-protocol.h
@@ -1,5 +1,5 @@
 /* nbdkit
- * Copyright (C) 2013-2019 Red Hat Inc.
+ * Copyright (C) 2013-2020 Red Hat Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
@@ -146,6 +146,7 @@ struct nbd_fixed_new_option_reply {
 #define NBD_INFO_NAME        1
 #define NBD_INFO_DESCRIPTION 2
 #define NBD_INFO_BLOCK_SIZE  3
+#define NBD_INFO_INIT_STATE  4

 /* NBD_INFO_EXPORT reply (follows fixed_new_option_reply). */
 struct nbd_fixed_new_option_reply_info_export {
@@ -154,6 +155,16 @@ struct nbd_fixed_new_option_reply_info_export {
   uint16_t eflags;              /* per-export flags */
 } NBD_ATTRIBUTE_PACKED;

+/* NBD_INFO_INIT_STATE reply. */
+struct nbd_fixed_new_option_reply_info_init {
+  uint16_t info;                /* NBD_INFO_INIT_STATE */
+  uint16_t flags;               /* per-export init flags */
+} NBD_ATTRIBUTE_PACKED;
+
+/* Constants for use in reply to NBD_INFO_INIT_STATE. */
+#define NBD_INIT_SPARSE   (1 << 0)
+#define NBD_INIT_ZERO     (1 << 1)
+
 /* NBD_REP_META_CONTEXT reply (follows fixed_new_option_reply). */
 struct nbd_fixed_new_option_reply_meta_context {
   uint32_t context_id;          /* metadata context ID */
-- 
2.24.1