Libguestfs - Sep 2019 - [PATCH libnbd] lib: Copy nbd-protocol.h from nbdkit 1.15.3.

Eventually nbdkit will install this as a public header file and we
will be able to consume it from $includedir.  In the mean time
synchronize with the copy in nbdkit.
---
 lib/nbd-protocol.h | 57 +++++++++++++++++++++++-----------------------
 1 file changed, 28 insertions(+), 29 deletions(-)

diff --git a/lib/nbd-protocol.h b/lib/nbd-protocol.h
index 699aa22..7df411a 100644
--- a/lib/nbd-protocol.h
+++ b/lib/nbd-protocol.h
@@ -30,21 +30,22 @@
  * SUCH DAMAGE.
  */
 
-/* This is derived from nbdkit's common/protocol/protocol.h.  In time
- * we expect that this library, nbdkit (and maybe others) should use
- * the exact same header.
- */
-
 #ifndef NBD_PROTOCOL_H
 #define NBD_PROTOCOL_H
 
 #include <stdint.h>
 
 /* Note that all NBD fields are sent on the wire in network byte
- * order, so we must use beXXtoh or htobeXX when reading or writing
+ * order, so you must use beXXtoh or htobeXX when reading or writing
  * these structures.
  */
 
+#if defined(__GNUC__) || defined(__clang__)
+#define NBD_ATTRIBUTE_PACKED __attribute__((__packed__))
+#else
+#define NBD_ATTRIBUTE_PACKED
+#endif
+
 #define NBD_MAX_STRING 4096 /* Maximum length of a string field */
 
 /* Old-style handshake. */
@@ -55,7 +56,7 @@ struct nbd_old_handshake {
   uint16_t gflags;            /* global flags */
   uint16_t eflags;            /* per-export flags */
   char zeroes[124];           /* must be sent as zero bytes */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 #define NBD_OLD_VERSION UINT64_C(0x420281861253)
 
@@ -64,7 +65,7 @@ struct nbd_new_handshake {
   char nbdmagic[8];           /* "NBDMAGIC" */
   uint64_t version;           /* NBD_NEW_VERSION */
   uint16_t gflags;            /* global flags */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 #define NBD_NEW_VERSION UINT64_C(0x49484156454F5054)
 
@@ -74,14 +75,14 @@ struct nbd_new_option {
   uint32_t option;            /* NBD_OPT_* */
   uint32_t optlen;            /* option data length */
   /* option data follows */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 /* Newstyle handshake OPT_EXPORT_NAME reply message. */
 struct nbd_export_name_option_reply {
   uint64_t exportsize;          /* size of export */
   uint16_t eflags;              /* per-export flags */
   char zeroes[124];             /* optional zeroes */
-} __attribute__((packed));;
+} NBD_ATTRIBUTE_PACKED;;
 
 /* Fixed newstyle handshake reply message. */
 struct nbd_fixed_new_option_reply {
@@ -89,14 +90,13 @@ struct nbd_fixed_new_option_reply {
   uint32_t option;            /* option we are replying to */
   uint32_t reply;             /* NBD_REP_* */
   uint32_t replylen;
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 #define NBD_REP_MAGIC UINT64_C(0x3e889045565a9)
 
-/* Global flags. Exposed by the generator as LIBNBD_HANDSHAKE_FLAG_* instead
+/* Global flags. */
 #define NBD_FLAG_FIXED_NEWSTYLE 1
 #define NBD_FLAG_NO_ZEROES      2
- */
 
 /* Per-export flags. */
 #define NBD_FLAG_HAS_FLAGS         (1 << 0)
@@ -146,19 +146,19 @@ struct nbd_fixed_new_option_reply_info_export {
   uint16_t info;                /* NBD_INFO_EXPORT */
   uint64_t exportsize;          /* size of export */
   uint16_t eflags;              /* per-export flags */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 /* 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 */
   /* followed by a string */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 /* NBD_REPLY_TYPE_BLOCK_STATUS block descriptor. */
 struct nbd_block_descriptor {
   uint32_t length;              /* length of block */
   uint32_t status_flags;        /* block type (hole etc) */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 /* New-style handshake server reply when using NBD_OPT_EXPORT_NAME.
  * Modern clients use NBD_OPT_GO instead of this.
@@ -167,7 +167,7 @@ struct nbd_new_handshake_finish {
   uint64_t exportsize;
   uint16_t eflags;            /* per-export flags */
   char zeroes[124];           /* must be sent as zero bytes */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 /* Request (client -> server). */
 struct nbd_request {
@@ -177,14 +177,14 @@ struct nbd_request {
   uint64_t handle;              /* Opaque handle. */
   uint64_t offset;              /* Request offset. */
   uint32_t count;               /* Request length. */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 /* Simple reply (server -> client). */
 struct nbd_simple_reply {
   uint32_t magic;               /* NBD_SIMPLE_REPLY_MAGIC. */
   uint32_t error;               /* NBD_SUCCESS or one of NBD_E*. */
   uint64_t handle;              /* Opaque handle. */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 /* Structured reply (server -> client). */
 struct nbd_structured_reply {
@@ -193,23 +193,23 @@ struct nbd_structured_reply {
   uint16_t type;                /* NBD_REPLY_TYPE_* */
   uint64_t handle;              /* Opaque handle. */
   uint32_t length;              /* Length of payload which follows. */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 struct nbd_structured_reply_offset_data {
   uint64_t offset;              /* offset */
   /* Followed by data. */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 struct nbd_structured_reply_offset_hole {
   uint64_t offset;
   uint32_t length;              /* Length of hole. */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 struct nbd_structured_reply_error {
   uint32_t error;               /* NBD_E* error number */
   uint16_t len;                 /* Length of human readable error. */
   /* Followed by human readable error string, and possibly more structure. */
-} __attribute__((packed));
+} NBD_ATTRIBUTE_PACKED;
 
 #define NBD_REQUEST_MAGIC           0x25609513
 #define NBD_SIMPLE_REPLY_MAGIC      0x67446698
@@ -239,12 +239,11 @@ struct nbd_structured_reply_error {
 #define NBD_CMD_WRITE_ZEROES      6
 #define NBD_CMD_BLOCK_STATUS      7
 
-/* Command flags. Exposed by the generator as LIBNBD_CMD_FLAG_* instead
-#define NBD_CMD_FLAG_FUA      (1<<0)
-#define NBD_CMD_FLAG_NO_HOLE  (1<<1)
-#define NBD_CMD_FLAG_DF       (1<<2)
-#define NBD_CMD_FLAG_REQ_ONE  (1<<3)
-*/
+#define NBD_CMD_FLAG_FUA       (1<<0)
+#define NBD_CMD_FLAG_NO_HOLE   (1<<1)
+#define NBD_CMD_FLAG_DF        (1<<2)
+#define NBD_CMD_FLAG_REQ_ONE   (1<<3)
+#define NBD_CMD_FLAG_FAST_ZERO (1<<4)
 
 /* NBD error codes. */
 #define NBD_SUCCESS     0
-- 
2.23.0

On 9/24/19 4:07 PM, Richard W.M. Jones wrote:
> Eventually nbdkit will install this as a public header file and we
> will be able to consume it from $includedir.  In the mean time
> synchronize with the copy in nbdkit.
> ---
>  lib/nbd-protocol.h | 57 +++++++++++++++++++++++-----------------------
>  1 file changed, 28 insertions(+), 29 deletions(-)
> 
>  /* Newstyle handshake OPT_EXPORT_NAME reply message. */
>  struct nbd_export_name_option_reply {
>    uint64_t exportsize;          /* size of export */
>    uint16_t eflags;              /* per-export flags */
>    char zeroes[124];             /* optional zeroes */
> -} __attribute__((packed));;
> +} NBD_ATTRIBUTE_PACKED;;
Double ;;

>  
> -/* Global flags. Exposed by the generator as LIBNBD_HANDSHAKE_FLAG_*
instead
> +/* Global flags. */
>  #define NBD_FLAG_FIXED_NEWSTYLE 1
>  #define NBD_FLAG_NO_ZEROES      2
> - */
We won't be using these names in the rest of libnbd, except maybe we
should add a compile-time assertion that NBD_FLAG_FIXED_NEWSTYLE
=LIBNBD_FLAG_FIXED_NEWSTYLE (ie. that our generator produces public
constants in <libnbd.h> that match the NBD protocol constants).

>  /* New-style handshake server reply when using NBD_OPT_EXPORT_NAME.
>   * Modern clients use NBD_OPT_GO instead of this.
> @@ -167,7 +167,7 @@ struct nbd_new_handshake_finish {
>    uint64_t exportsize;
>    uint16_t eflags;            /* per-export flags */
>    char zeroes[124];           /* must be sent as zero bytes */
> -} __attribute__((packed));
> +} NBD_ATTRIBUTE_PACKED;
Redundant type.

>  
> -/* Command flags. Exposed by the generator as LIBNBD_CMD_FLAG_* instead
> -#define NBD_CMD_FLAG_FUA      (1<<0)
> -#define NBD_CMD_FLAG_NO_HOLE  (1<<1)
> -#define NBD_CMD_FLAG_DF       (1<<2)
> -#define NBD_CMD_FLAG_REQ_ONE  (1<<3)
> -*/
> +#define NBD_CMD_FLAG_FUA       (1<<0)
> +#define NBD_CMD_FLAG_NO_HOLE   (1<<1)
> +#define NBD_CMD_FLAG_DF        (1<<2)
> +#define NBD_CMD_FLAG_REQ_ONE   (1<<3)
> +#define NBD_CMD_FLAG_FAST_ZERO (1<<4)
Another case where having compile-time assertions that our generator
matches protocol constants is probably worthwhile.

ACK to the plan for synchronizing.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On Tue, Sep 24, 2019 at 05:24:34PM -0500, Eric Blake
wrote:
> On 9/24/19 4:07 PM, Richard W.M. Jones wrote:
> >  /* New-style handshake server reply when using NBD_OPT_EXPORT_NAME.
> >   * Modern clients use NBD_OPT_GO instead of this.
> > @@ -167,7 +167,7 @@ struct nbd_new_handshake_finish {
> >    uint64_t exportsize;
> >    uint16_t eflags;            /* per-export flags */
> >    char zeroes[124];           /* must be sent as zero bytes */
> > -} __attribute__((packed));
> > +} NBD_ATTRIBUTE_PACKED;
> 
> Redundant type.
Indeed, we don't actually use this anywhere (for obvious reasons of
course).  As I was only synchronizing the two headers I didn't notice.
I'll remove it instead.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org