[Libguestfs] [nbdkit PATCH 4/4] server: Fix OPT_GO on different export than SET_META_CONTEXT

[Eric Blake]

On 9/18/19 10:01 PM, Eric Blake wrote:
> The NBD spec says that if a client requests SET_META_CONTEXT for
> exportA, but later requests NBD_OPT_GO/EXPORT_NAME for exportB, then
> the server should reject NBD_CMD_BLOCK_STATUS requests (that is, the
> context returned for exportA need not apply to exportB).  When we
> originally added base:allocation, our argument was that we always
> ignore export names, so it was easier to just treat any two export
> names as being the same export, so no need to reset things.  But now
> that we have nbdkit_export_name(), we are better off obeying the spec.
> 
> Note that there are no known clients in the wild that can actually
> perform this cross-export-name request; this was found by inspection.
> I also don't see the point in hacking up libnbd to become such a
> client.
> 
> Fixes: 4f303e44
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
>  server/internal.h                    |  1 +
>  server/protocol-handshake-newstyle.c | 24 ++++++++++++++++++++++--
>  2 files changed, 23 insertions(+), 2 deletions(-)
> 

This missed NBD_OPT_EXPORT_NAME, I'll see if I can factor out a common
helper function rather than duplicating code.  (Then again, a client
that requests SET_META_CONTEXT but doesn't use OPT_GO is an anomaly)

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

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