Re: [Qemu-devel] [PATCH 3/7] qemu-nbd: add support for --object command line arg

[Eric Blake <eblake@redhat.com>]

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On 12/22/2015 04:06 AM, Daniel P. Berrange wrote:
> Allow creation of user creatable object types with qemu-nbd
> via a --object command line arg. This will be used to supply
> passwords and/or encryption keys to the various block driver
> backends via the recently added 'secret' object type.
> 
>  # echo -n letmein > mypasswd.txt
>  # qemu-nbd --object secret,id=sec0,file=mypasswd.txt \
>       ...other nbd args...

Same comments as on 2/7.


> @@ -45,6 +48,7 @@
>  #define QEMU_NBD_OPT_AIO           2
>  #define QEMU_NBD_OPT_DISCARD       3
>  #define QEMU_NBD_OPT_DETECT_ZEROES 4
> +#define QEMU_NBD_OPT_OBJECT        5

Pre-existing, but these are unsafe; they conflict with actual byte
values.  As long as you are touching this, you should fix them to start
at 256 (a separate patch wouldn't hurt).


> +static int object_create(void *opaque, QemuOpts *opts, Error **errp)
> +{
> +    Error *err = NULL;
> +    char *type = NULL;
> +    char *id = NULL;
> +    void *dummy = NULL;
> +    OptsVisitor *ov;
> +    QDict *pdict;
> +
> +    ov = opts_visitor_new(opts);
> +    pdict = qemu_opts_to_qdict(opts, NULL);
> +
> +    visit_start_struct(opts_get_visitor(ov), &dummy, NULL, NULL, 0, &err);

Same comments as on 2/7.


> @@ -417,6 +485,7 @@ int main(int argc, char **argv)
>          { "format", 1, NULL, 'f' },
>          { "persistent", 0, NULL, 't' },
>          { "verbose", 0, NULL, 'v' },
> +        { "object", 1, NULL, QEMU_NBD_OPT_OBJECT },
>          { NULL, 0, NULL, 0 }

Pre-existing, but 0 and 1 are magic numbers; I prefer the symbolic names
no_argument and required_argument (and optional_argument for 2).


> +++ b/qemu-nbd.texi
> @@ -14,6 +14,13 @@ Export QEMU disk image using NBD protocol.
>  @table @option
>  @item @var{filename}
>   is a disk image filename
> +@item --object type,id=@var{id},...props...
> +  define a new instance of the @var{type} object class
> +  identified by @var{id}. See the @code{qemu(1)} manual
> +  page for full details of the properties supported.
> +  The only object type that it makes sense to define
> +  is the @code{secret} object, which is used to supply
> +  passwords and/or encryption keys.

Awfully short line-wrapping; although it doesn't matter in the final
generated docs.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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