9pfs/virtio: implement response_buffer_size callback

Add and implement the response_buffer_size callback for the virtio
transport.

Returns the actual current virtio response buffer size for the supplied
PDU, which will be used as safety guard for limiting the response size
when generating a 9p response.

Link: https://lore.kernel.org/qemu-devel/5bbed2768f7a0da8fa2be183e75928c5d1ef691d.1781287774.git.qemu_oss@crudebyte.com
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
1 file changed