[libnbd PATCH v3 03/22] 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@redhat.com>
---
 lib/nbd-protocol.h | 66 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 14 deletions(-)

diff --git a/lib/nbd-protocol.h b/lib/nbd-protocol.h
index f4640a98..b6fa9b8a 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 handle;              /* 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 handle;              /* 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 payload which follows. */
 } 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 handle;              /* Opaque handle. */
+  uint64_t offset;              /* Client's offset. */
+  uint64_t length;              /* Length of payload which follows. */
+} NBD_ATTRIBUTE_PACKED;
+
 struct nbd_structured_reply_offset_data {
   uint64_t offset;              /* offset */
   /* Followed by data. */
@@ -224,11 +246,23 @@ struct nbd_block_descriptor {
   uint32_t status_flags;        /* block type (hole etc) */
 } NBD_ATTRIBUTE_PACKED;

+/* NBD_REPLY_TYPE_BLOCK_STATUS_EXT block descriptor. */
+struct nbd_block_descriptor_ext {
+  uint64_t length;              /* length of block */
+  uint64_t status_flags;        /* block type (hole etc) */
+} NBD_ATTRIBUTE_PACKED;
+
 struct nbd_structured_reply_block_status_hdr {
   uint32_t context_id;          /* metadata context ID */
   /* followed by array of nbd_block_descriptor extents */
 } NBD_ATTRIBUTE_PACKED;

+struct nbd_structured_reply_block_status_ext_hdr {
+  uint32_t context_id;          /* metadata context ID */
+  uint32_t count;               /* length of following array */
+  /* followed by array of nbd_block_descriptor_ext extents */
+} NBD_ATTRIBUTE_PACKED;
+
 struct nbd_structured_reply_error {
   uint32_t error;               /* NBD_E* error number */
   uint16_t len;                 /* Length of human readable error. */
@@ -236,8 +270,10 @@ struct nbd_structured_reply_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         (1<<0)
@@ -246,12 +282,13 @@ struct nbd_structured_reply_error {
 #define NBD_REPLY_TYPE_IS_ERR(val) (!!((val) & (1<<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
@@ -263,11 +300,12 @@ struct nbd_structured_reply_error {
 #define NBD_CMD_WRITE_ZEROES      6
 #define NBD_CMD_BLOCK_STATUS      7

-#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)
+#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)
+#define NBD_CMD_FLAG_PAYLOAD_LEN (1<<5)

 /* NBD error codes. */
 #define NBD_SUCCESS     0
-- 
2.40.1