Re: [PATCH v3 1/4] qapi: net: Add query-netdevs command

From: Markus Armbruster <armbru@redhat.com>
To: Alexey Kirillov <lekiravi@yandex-team.ru>
Cc: Laurent Vivier <lvivier@redhat.com>,
	Thomas Huth <thuth@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Stefan Weil <sw@weilnetz.de>, Jason Wang <jasowang@redhat.com>,
	qemu-devel@nongnu.org, Vincenzo Maffione <v.maffione@gmail.com>,
	Luigi Rizzo <rizzo@iet.unipi.it>,
	yc-core@yandex-team.ru,
	Samuel Thibault <samuel.thibault@ens-lyon.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Giuseppe Lettieri <g.lettieri@iet.unipi.it>
Subject: Re: [PATCH v3 1/4] qapi: net: Add query-netdevs command
Date: Wed, 02 Sep 2020 13:23:32 +0200	[thread overview]
Message-ID: <87lfhsjubv.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: <20200901182326.59633-2-lekiravi@yandex-team.ru> (Alexey Kirillov's message of "Tue, 1 Sep 2020 21:23:23 +0300")

Alexey Kirillov <lekiravi@yandex-team.ru> writes:

> Add a qmp command that provides information about currently attached
> backend network devices and their configuration.
>
> Signed-off-by: Alexey Kirillov <lekiravi@yandex-team.ru>
[...]
> diff --git a/qapi/net.json b/qapi/net.json
> index ddb113e5e5..c09322bb42 100644
> --- a/qapi/net.json
> +++ b/qapi/net.json
> @@ -714,3 +714,71 @@
>  ##
>  { 'event': 'FAILOVER_NEGOTIATED',
>    'data': {'device-id': 'str'} }
> +
> +##
> +# @NetdevInfo:
> +#
> +# Configuration of a network backend device (netdev).
> +#
> +# @id: Device identifier.
> +#
> +# @type: Specify the driver used for interpreting remaining arguments.
> +#
> +# @peer-id: Connected frontend network device identifier.
> +#
> +# Since: 5.2
> +##
> +{ 'union': 'NetdevInfo',
> +  'base': { 'id': 'str',
> +            'type': 'NetClientDriver',
> +            '*peer-id': 'str' },
> +  'discriminator': 'type',
> +  'data': {
> +      'user':       'NetdevUserOptions',
> +      'tap':        'NetdevTapOptions',
> +      'l2tpv3':     'NetdevL2TPv3Options',
> +      'socket':     'NetdevSocketOptions',
> +      'vde':        'NetdevVdeOptions',
> +      'bridge':     'NetdevBridgeOptions',
> +      'netmap':     'NetdevNetmapOptions',
> +      'vhost-user': 'NetdevVhostUserOptions',
> +      'vhost-vdpa': 'NetdevVhostVDPAOptions' } }

This is union Netdev plus a common member @peer-id, less the variant
members for NetClientDriver values 'nic' and 'hubport'.

Can 'type: 'nic' and 'type': 'hubport' occur?

What's the use case for @peer-id?

Assuming we want @peer-id: its documentation is too vague.  Cases:

* Not connected to a frontend: I guess @peer-id is absent then.

* Connected to a frontend

  - that has a qdev ID (the thing you set with -device id=...): I guess
    it's the qdev ID then.

  - that doesn't have a qdev ID: anyone's guess.

> +
> +##
> +# @query-netdevs:
> +#
> +# Get a list of @NetdevInfo for all virtual network backend devices (netdevs).
> +#
> +# Returns: a list of @NetdevInfo describing each netdev.
> +#
> +# Since: 5.2
> +#
> +# Example:
> +#
> +# -> { "execute": "query-netdevs" }
> +# <- { "return": [
> +#          {
> +#              "ipv6": true,
> +#              "ipv4": true,
> +#              "host": "10.0.2.2",
> +#              "ipv6-dns": "fec0::3",
> +#              "ipv6-prefix": "fec0::",
> +#              "net": "10.0.2.0/255.255.255.0",
> +#              "ipv6-host": "fec0::2",
> +#              "type": "user",
> +#              "peer-id": "net0",
> +#              "dns": "10.0.2.3",
> +#              "hostfwd": [
> +#                  {
> +#                      "str": "tcp::20004-:22"
> +#                  }
> +#              ],
> +#              "ipv6-prefixlen": 64,
> +#              "id": "netdev0",
> +#              "restrict": false
> +#          }
> +#      ]
> +#    }
> +#
> +##
> +{ 'command': 'query-netdevs', 'returns': ['NetdevInfo'] }