[Libguestfs] [libnbd PATCH v4 3/6] protocol: Add definitions for extended headers

[Eric Blake]

Add the magic numbers and new structs necessary to implement the NBD
protocol extension of extended headers providing 64-bit lengths.  This
corresponds to upstream nbd commits 36abf47d and a9384e2f on the
extension-ext-header branch[1] (commit e6f3b94a for
NBD_FLAG_BLOCK_STATUS_PAYLOAD is saved for a later patch).

[1] https://github.com/NetworkBlockDevice/nbd/blob/extension-ext-header/doc/proto.md

Signed-off-by: Eric Blake <eblake at redhat.com>
Reviewed-by: Laszlo Ersek <lersek at redhat.com>
---

v4: tweak comment on block_status_64.count [Laszlo], rebase to earlier
struct renames (for example, nbd_block_descriptor_64 instead of
nbd_structured_reply_block_status_hdr). Seemed obvious enough that I
felt okay keeping Laszlo's R-b.
---
 lib/nbd-protocol.h | 55 ++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 46 insertions(+), 9 deletions(-)

diff --git a/lib/nbd-protocol.h b/lib/nbd-protocol.h
index 58583d1d..b5a28ae4 100644
--- a/lib/nbd-protocol.h
+++ b/lib/nbd-protocol.h
@@ -124,6 +124,7 @@ struct nbd_fixed_new_option_reply {
 #define NBD_OPT_STRUCTURED_REPLY   8
 #define NBD_OPT_LIST_META_CONTEXT  9
 #define NBD_OPT_SET_META_CONTEXT   10
+#define NBD_OPT_EXTENDED_HEADERS   11

 #define NBD_REP_ERR(val) (0x80000000 | (val))
 #define NBD_REP_IS_ERR(val) (!!((val) & 0x80000000))
@@ -141,6 +142,7 @@ struct nbd_fixed_new_option_reply {
 #define NBD_REP_ERR_SHUTDOWN         NBD_REP_ERR (7)
 #define NBD_REP_ERR_BLOCK_SIZE_REQD  NBD_REP_ERR (8)
 #define NBD_REP_ERR_TOO_BIG          NBD_REP_ERR (9)
+#define NBD_REP_ERR_EXT_HEADER_REQD  NBD_REP_ERR (10)

 #define NBD_INFO_EXPORT      0
 #define NBD_INFO_NAME        1
@@ -182,16 +184,26 @@ struct nbd_fixed_new_option_reply_meta_context {
   /* followed by a string */
 } NBD_ATTRIBUTE_PACKED;

-/* Request (client -> server). */
+/* Compact request (client -> server). */
 struct nbd_request {
   uint32_t magic;               /* NBD_REQUEST_MAGIC. */
-  uint16_t flags;               /* Request flags. */
-  uint16_t type;                /* Request type. */
+  uint16_t flags;               /* Request flags: NBD_CMD_FLAG_*. */
+  uint16_t type;                /* Request type: NBD_CMD_*. */
   uint64_t cookie;              /* Opaque handle. */
   uint64_t offset;              /* Request offset. */
   uint32_t count;               /* Request length. */
 } NBD_ATTRIBUTE_PACKED;

+/* Extended request (client -> server). */
+struct nbd_request_ext {
+  uint32_t magic;               /* NBD_EXTENDED_REQUEST_MAGIC. */
+  uint16_t flags;               /* Request flags: NBD_CMD_FLAG_*. */
+  uint16_t type;                /* Request type: NBD_CMD_*. */
+  uint64_t cookie;              /* Opaque handle. */
+  uint64_t offset;              /* Request offset. */
+  uint64_t count;               /* Request effect or payload length. */
+} NBD_ATTRIBUTE_PACKED;
+
 /* Simple reply (server -> client). */
 struct nbd_simple_reply {
   uint32_t magic;               /* NBD_SIMPLE_REPLY_MAGIC. */
@@ -208,6 +220,16 @@ struct nbd_structured_reply {
   uint32_t length;              /* Length of following nbd_chunk_* payload. */
 } NBD_ATTRIBUTE_PACKED;

+/* Extended reply (server -> client). */
+struct nbd_extended_reply {
+  uint32_t magic;               /* NBD_EXTENDED_REPLY_MAGIC. */
+  uint16_t flags;               /* NBD_REPLY_FLAG_* */
+  uint16_t type;                /* NBD_REPLY_TYPE_* */
+  uint64_t cookie;              /* Opaque handle. */
+  uint64_t offset;              /* Client's offset. */
+  uint64_t length;              /* Length of following nbd_chunk_* payload. */
+} NBD_ATTRIBUTE_PACKED;
+
 struct nbd_chunk_offset_data {
   uint64_t offset;              /* offset */
   /* Followed by data. */
@@ -228,6 +250,17 @@ struct nbd_block_descriptor_32 {
   uint32_t status_flags;        /* block type (hole etc) */
 } NBD_ATTRIBUTE_PACKED;

+struct nbd_chunk_block_status_64 {
+  uint32_t context_id;          /* metadata context ID */
+  uint32_t count;               /* non-zero descriptor count */
+  /* followed by nbd_block_descriptor_64[count] extents */
+} NBD_ATTRIBUTE_PACKED;
+
+struct nbd_block_descriptor_64 {
+  uint64_t length;              /* length of block */
+  uint64_t status_flags;        /* block type (hole etc) */
+} NBD_ATTRIBUTE_PACKED;
+
 struct nbd_chunk_error {
   uint32_t error;               /* NBD_E* error number */
   uint16_t len;                 /* Length of human readable error. */
@@ -235,8 +268,10 @@ struct nbd_chunk_error {
 } NBD_ATTRIBUTE_PACKED;

 #define NBD_REQUEST_MAGIC           0x25609513
+#define NBD_EXTENDED_REQUEST_MAGIC  0x21e41c71
 #define NBD_SIMPLE_REPLY_MAGIC      0x67446698
 #define NBD_STRUCTURED_REPLY_MAGIC  0x668e33ef
+#define NBD_EXTENDED_REPLY_MAGIC    0x6e8a278c

 /* Structured reply flags. */
 #define NBD_REPLY_FLAG_DONE         (1U << 0)
@@ -245,12 +280,13 @@ struct nbd_chunk_error {
 #define NBD_REPLY_TYPE_IS_ERR(val) (!!((val) & (1U<<15)))

 /* Structured reply types. */
-#define NBD_REPLY_TYPE_NONE         0
-#define NBD_REPLY_TYPE_OFFSET_DATA  1
-#define NBD_REPLY_TYPE_OFFSET_HOLE  2
-#define NBD_REPLY_TYPE_BLOCK_STATUS 5
-#define NBD_REPLY_TYPE_ERROR        NBD_REPLY_TYPE_ERR (1)
-#define NBD_REPLY_TYPE_ERROR_OFFSET NBD_REPLY_TYPE_ERR (2)
+#define NBD_REPLY_TYPE_NONE             0
+#define NBD_REPLY_TYPE_OFFSET_DATA      1
+#define NBD_REPLY_TYPE_OFFSET_HOLE      2
+#define NBD_REPLY_TYPE_BLOCK_STATUS     5
+#define NBD_REPLY_TYPE_BLOCK_STATUS_EXT 6
+#define NBD_REPLY_TYPE_ERROR            NBD_REPLY_TYPE_ERR (1)
+#define NBD_REPLY_TYPE_ERROR_OFFSET     NBD_REPLY_TYPE_ERR (2)

 /* NBD commands. */
 #define NBD_CMD_READ              0
@@ -267,6 +303,7 @@ struct nbd_chunk_error {
 #define NBD_CMD_FLAG_DF           (1U << 2)
 #define NBD_CMD_FLAG_REQ_ONE      (1U << 3)
 #define NBD_CMD_FLAG_FAST_ZERO    (1U << 4)
+#define NBD_CMD_FLAG_PAYLOAD_LEN  (1U << 5)

 /* NBD error codes. */
 #define NBD_SUCCESS     0
-- 
2.41.0