Re: [Qemu-devel] [PATCH v7 13/15] net: Complete qapi-fication of netdev_add

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> We finally have all the required pieces for doing a type-safe
> representation of netdev_add as a flat union, where the
> discriminator 'type' now selects which additional members may
> appear in the "arguments" JSON object sent over QMP, while
> making no changes to the set of previously-valid QMP commands
> that would work, and without breaking command line parsing.

Isn't it amazing that you pulled this off without a compatibility break?

>
> Signed-off-by: Eric Blake <eblake@redhat.com>
>
> ---
> v7: no change
> v6: don't lose qemu_opts handling
> ---
>  qapi-schema.json  | 15 +++------------
>  include/net/net.h |  1 -
>  net/net.c         |  6 +++---
>  qmp-commands.hx   |  2 +-
>  4 files changed, 7 insertions(+), 17 deletions(-)
>
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 4fee44b..fee4d07 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -2301,26 +2301,17 @@
>  #
>  # Add a network backend.
>  #
> -# @type: the type of network backend.  Current valid values are 'user', 'tap',
> -#        'vde', 'socket', 'dump' and 'bridge'
> +# @type: the type of network backend; determines which additional arguments
> +#        are valid. See Netdev documentation for more details.
>  #
>  # @id: the name of the new network backend
>  #
> -# Additional arguments depend on the type.
> -#
> -# TODO This command effectively bypasses QAPI completely due to its
> -# "additional arguments" business.  It shouldn't have been added to
> -# the schema in this form.  It should be qapified properly, or
> -# replaced by a properly qapified command.
> -#
>  # Since: 0.14.0
>  #
>  # Returns: Nothing on success
>  #          If @type is not a valid network backend, DeviceNotFound
>  ##
> -{ 'command': 'netdev_add',
> -  'data': {'type': 'str', 'id': 'str'},
> -  'gen': false }                # so we can get the additional arguments
> +{ 'command': 'netdev_add', 'data': 'Netdev', 'box': true }
>
>  ##
>  # @netdev_del:
> diff --git a/include/net/net.h b/include/net/net.h
> index 74b32e0..8f9be98 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -193,7 +193,6 @@ void net_cleanup(void);
>  void hmp_host_net_add(Monitor *mon, const QDict *qdict);
>  void hmp_host_net_remove(Monitor *mon, const QDict *qdict);
>  void netdev_add(QemuOpts *opts, Error **errp);
> -void qmp_netdev_add(QDict *qdict, QObject **ret, Error **errp);

Only a dead QemuOpts is a good QemuOpts.

>
>  int net_hub_id_for_client(NetClientState *nc, int *id);
>  NetClientState *net_hub_port_find(int hub_id);
> diff --git a/net/net.c b/net/net.c
> index e159506..b93ff00 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -1188,7 +1188,7 @@ void netdev_add(QemuOpts *opts, Error **errp)
>      net_client_init(opts, true, errp);
>  }
>
> -void qmp_netdev_add(QDict *qdict, QObject **ret, Error **errp)
> +void qmp_netdev_add(Netdev *netdev, Error **errp)
>  {
>      Error *local_err = NULL;
>      QemuOptsList *opts_list;
> @@ -1199,12 +1199,12 @@ void qmp_netdev_add(QDict *qdict, QObject **ret, Error **errp)
>          goto out;
>      }
>
> -    opts = qemu_opts_from_qdict(opts_list, qdict, &local_err);
> +    opts = qemu_opts_create(opts_list, netdev->id, 1, &local_err);

We keep creating a QemuOpts for the network backend, but its opts->head
remains empty.  We need it for qmp_netdev_del().  Possibly more, but I
doubt it.

I think this is worth a mention in the commit message.  

>      if (local_err) {
>          goto out;
>      }
>
> -    netdev_add(opts, &local_err);
> +    net_client_init1(netdev, true, &local_err);
>      if (local_err) {
>          qemu_opts_del(opts);
>          goto out;

Suggest to inline netdev_add() into its only remaining caller
hmp_netdev_add().

> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 94847e5..3804030 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -949,7 +949,7 @@ EQMP
>      {
>          .name       = "netdev_add",
>          .args_type  = "netdev:O",
> -        .mhandler.cmd_new = qmp_netdev_add,
> +        .mhandler.cmd_new = qmp_marshal_netdev_add,
>      },
>
>  SQMP