Re: [Qemu-devel] [PATCH RFC v2 3/5] net/filter: Introduce a helper to add a filter to the netdev

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Jan 27, 2016 at 04:29:38PM +0800, zhanghailiang wrote:
> We add a new helper function netdev_add_filter(), this function
> can help adding a filter object to a netdev.
> Besides, we add a is_default member for struct NetFilterState
> to indicate whether the filter is default or not.
> 
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
> v2:
>  -Re-implement netdev_add_filter() by re-using object_create()
>   (Jason's suggestion)
> ---
>  include/net/filter.h |  7 +++++
>  net/filter.c         | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 87 insertions(+)

> +void netdev_add_filter(const char *netdev_id,
> +                       const char *filter_type,
> +                       const char *id,
> +                       bool is_default,
> +                       Error **errp)
> +{
> +    NetClientState *nc = qemu_find_netdev(netdev_id);
> +    char *optarg;
> +    QemuOpts *opts = NULL;
> +    Error *err = NULL;
> +
> +    /* FIXME: Not support multiple queues */
> +    if (!nc || nc->queue_index > 1) {
> +        return;
> +    }
> +    /* Not support vhost-net */
> +    if (get_vhost_net(nc)) {
> +        return;
> +    }
> +
> +    optarg = g_strdup_printf("qom-type=%s,id=%s,netdev=%s,status=%s",
> +            filter_type, id, netdev_id, is_default ? "disable" : "enable");
> +    opts = qemu_opts_parse_noisily(&qemu_filter_opts,
> +                                   optarg, false);

Formatting a string and then immediately parsing it again is totally
crazy, not least because you're not taking care to do escaping of
special characters like ',' in the string parameters.

> +    if (!opts) {
> +        error_report("Failed to parse param '%s'", optarg);
> +        exit(1);
> +    }
> +    g_free(optarg);
> +    if (object_create(NULL, opts, &err) < 0) {
> +        error_report("Failed to create object");
> +        goto out_clean;
> +    }

Don't use object_create() - use object_new_with_props() which avoids
the need to format + parse the string above. ie do

  object_new_with_props(filter_type,
                        object_get_objects_root(),
			id,
			&err,
			"netdev", netdev_id,
			"status", is_default ? "disable" : "enable",
			NULL);


Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|