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[Qemu-devel] [PATCH] doc: Revert swap of NBD_REP_SERVER fields in NBD_OP

From: Eric Blake
Subject: [Qemu-devel] [PATCH] doc: Revert swap of NBD_REP_SERVER fields in NBD_OPT_GO
Date: Wed, 6 Apr 2016 22:12:10 -0600

Commit 730c5830 included a reordering of the fields of
NBD_REP_SERVER, under the guise of putting the variable-sized
data last.  However, this makes life harder for sharing
code - the regular NBD_REP_SERVER used by NBD_OPT_LIST
already has _two_ variable-sized fields: name, and an optional
string of additional information, and the wording of the
surrounding text implied that NBD_OPT_GO was just re-purposing
the tail end as binary data instead of a string, not
reorganizing all the fields.

Furthermore, sticking the same fields last in both NBD_OPT_GO
and NBD_OPT_EXPORT_NAME means that any other future handshake
extension that sends a few more bytes of data behind the
transmission flags can do so in both places without reordering
the first half of NBD_REP_SERVER (such an extension is already
envisioned, where the client and server agree to have the server
advertise minimum, preferred, and maximum block sizes).

Signed-off-by: Eric Blake <address@hidden>

I'm trying to implement NBD_OPT_GO in qemu, and found the original
order easier to support than the swapped order.

 doc/proto.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/doc/proto.md b/doc/proto.md
index 7b36be4..0775360 100644
--- a/doc/proto.md
+++ b/doc/proto.md
@@ -744,13 +744,13 @@ Therefore these commands share common documentation.
     in place of the default UTF-8 free-form string). The option reply length
     MUST be *length of name* + 14, and the option data has the following 

-    - 64 bits, size of the export in bytes (unsigned)
-    - 16 bits, transmission flags.
     - 32 bits, length of name (unsigned)
     - Name of the export. This name MAY be different from the one
       given in the `NBD_OPT_INFO` or `NBD_OPT_GO` option in case the
       server has multiple alternate names for a single export, or a
       default export was specified.
+    - 64 bits, size of the export in bytes (unsigned)
+    - 16 bits, transmission flags.

     The server MUST NOT fail an NBD_OPT_GO sent with the same parameters
     as a previous NBD_OPT_INFO which returned successfully (i.e. with

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