On 02/03/2016 09:33 AM, Max Reitz wrote: > We have to introduce a new object (BlockdevOptionsNbd) for several > reasons: > - Neither of InetSocketAddress nor UnixSocketAddress alone is > sufficient, because both are supported > - We cannot use SocketAddress because NBD does not support an fd, > and because it is not a flat union which BlockdevOptionsNbd is
Can we do it anyways, and just error out/document that fd is unsupported?
> - We cannot use a flat union of InetSocketAddress and
> UnixSocketAddress because we would need some kind of discriminator
> which we do not have; we could inline the UnixSocketAddress as a
> string and then make it an 'alternate' type instead of a union, but
> this will not work either, because:
> - InetSocketAddress itself is not suitable for NBD because the port is
> not optional (which it is for NBD) and because it offers more options
> (like choosing between ipv4 and ipv6) which NBD does not support.
That, and qapi doesn't (yet) support the use of a flat union as the
branch of yet another flat union.
I'd like to reach the point where we can have a flat union with an
implicit discriminator (if the discriminator was not present, the
require a default branch), but don't think it should hold up this patch.
I also think that future qapi improvements may make it possible to
retrofit this struct to make the mutual exclusion between host/file more
obvious during introspection, rather than just by documentation.
>
> Signed-off-by: Max Reitz <mre...@redhat.com>
> ---
> qapi/block-core.json | 28 ++++++++++++++++++++++++++--
> 1 file changed, 26 insertions(+), 2 deletions(-)
>
> ##
> +# @BlockdevOptionsNbd
> +#
> +# Driver specific block device options for NBD. Either of @host or @path
> must be
> +# specified, but not both.
> +#
> +# @host: #optional Connects to the given host using TCP.
> +#
> +# @port: #optional Specifies the TCP port to connect to; may be used only
> in
> +# conjunction with @host. Defaults to 10809.
> +#
> +# @path: #optional Connects to the given Unix socket path.
> +#
> +# @export: #optional Name of the NBD export to open.
Maybe mention that the default is no export name.
> +#
> +# Since: 2.6
> +##
> +{ 'struct': 'BlockdevOptionsNbd',
> + 'data': { '*host': 'str',
> + '*port': 'str',
> + '*path': 'str',
> + '*export': 'str' } }
I'm not entirely convinced this is the final representation we want, but
I can't immediately propose anything nicer.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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