[Qemu-devel] [RFC PATCH 00/18] NBD protocol additions

[Eric Blake <eblake@redhat.com>]

This series is for qemu 2.7, and will probably need some rework
especially since some of it is trying to implement features
that are still marked experimental in upstream NBD.

Included are some interoperability bug fixes, code cleanups, then
added support both client-side and server-side for:
NBD_FLAG_C_NO_ZEROES
NBD_CMD_WRITE_ZEROES
NBD_CMD_CLOSE
NBD_OPT_INFO
NBD_OPT_GO

Still to come:
improvements to NBD_CMD_WRITE_ZEROES
support for NBD_OPT_STRUCTURED_REPLY
strawman implementations to help with discussions towards
 NBD_CMD_BLOCK_STATUS
proposal I'm still working up to teach NBD servers to advertise
 minimum/preferred/maximum block sizes

This posting is tied to this particular version of the NBD protocol:
https://github.com/yoe/nbd/blob/18918eb/doc/proto.md
plus this email about NBD_CMD_CLOSE:
https://sourceforge.net/p/nbd/mailman/message/35000466/

I performed testing by temporarily turning on DEBUG_NBD while
compiling, then connecting variations on:
  ./qemu-nbd -f raw -x foo file
  ./qemu-io -f raw nbd://localhost:10809/foo
and watching the traces on both screen (both for startup negotiation,
and for various 'write -z', 'discard', and 'q' commands in qemu-io).
I intentionally tested all three combinations of:
old client, new server
new client, old server
new client, new server
to make sure that either side gracefully handles unknown
advertisements when the other side is newer, and correctly falls
back to older usage when the other side is too old.

I'm posting now so that others may compile my work and help with
cross-project testing (such as qemu client to Alex's NBDGO
server), which in turn will help us move experimental extensions
into final form in the NBD protocol.

Also available as a tag at this location:
git fetch git://repo.or.cz/qemu/ericb.git nbd-flags-v2

Tag is named v2 because patches 1 and 2 in this grouping have
been previously posted for inclusion in qemu 2.6

Eric Blake (18):
  nbd: Don't kill server on client that doesn't request TLS
  nbd: Don't fail handshake on NBD_OPT_LIST descriptions
  nbd: More debug typo fixes, use correct formats
  nbd: Detect servers that send unexpected error values
  nbd: Reject unknown request flags
  nbd: Avoid magic number for NBD max name size
  nbd: Treat flags vs. command type as separate fields
  nbd: Limit nbdflags to 16 bits
  nbd: Share common reply-sending code in server
  nbd: Share common option-sending code in client
  nbd: Let client skip portions of server reply
  nbd: Less allocation during NBD_OPT_LIST
  nbd: Support shorter handshake
  nbd: Implement NBD_OPT_GO on client
  nbd: Implement NBD_OPT_GO on server
  nbd: Support NBD_CMD_CLOSE
  nbd: Implement NBD_CMD_WRITE_ZEROES on server
  nbd: Implement NBD_CMD_WRITE_ZEROES on client

 block/nbd-client.h  |   2 +
 include/block/nbd.h |  61 ++++--
 nbd/nbd-internal.h  |  13 +-
 block/nbd-client.c  |  88 ++++++++-
 block/nbd.c         |  23 +++
 nbd/client.c        | 522 ++++++++++++++++++++++++++++++----------------------
 nbd/server.c        | 356 ++++++++++++++++++++++++++---------
 qemu-nbd.c          |   2 +-
 8 files changed, 744 insertions(+), 323 deletions(-)

-- 
2.5.5