netdev - Re: [PATCH net-next V3 2/2] rtnl: Add support for netdev event attribute to link messages

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Date:   Sun, 23 Apr 2017 19:07:56 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Vladislav Yasevich <vyasevich@...il.com>, netdev@...r.kernel.org
Cc:     Vladislav Yasevich <vyasevic@...hat.com>,
        roopa <roopa@...ulusnetworks.com>, Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH net-next V3 2/2] rtnl: Add support for netdev event
 attribute to link messages

On 4/21/17 11:31 AM, Vladislav Yasevich wrote:
> @@ -1276,9 +1277,40 @@ static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev)
>  	return err;
>  }
>  
> +static int rtnl_fill_link_event(struct sk_buff *skb, unsigned long event)
> +{
> +	u32 rtnl_event;
> +
> +	switch (event) {
> +	case NETDEV_REBOOT:
> +		rtnl_event = IFLA_EVENT_REBOOT;
> +		break;
> +	case NETDEV_FEAT_CHANGE:
> +		rtnl_event = IFLA_EVENT_FEAT_CHANGE;
> +		break;
> +	case NETDEV_BONDING_FAILOVER:
> +		rtnl_event = IFLA_EVENT_BONDING_FAILOVER;
> +		break;
> +	case NETDEV_NOTIFY_PEERS:
> +		rtnl_event = IFLA_EVENT_NOTIFY_PEERS;
> +		break;
> +	case NETDEV_RESEND_IGMP:
> +		rtnl_event = IFLA_EVENT_RESEND_IGMP;
> +		break;
> +	case NETDEV_CHANGEINFODATA:
> +		rtnl_event = IFLA_EVENT_CHANGE_INFO_DATA;
> +		break;
> +	default:
> +		return 0;
> +	}
> +
> +	return nla_put_u32(skb, IFLA_EVENT, rtnl_event);
> +}
> +

I still have doubts about encoding kernel events into a uapi.

For example, NETDEV_CHANGEINFODATA is only for bonds though nothing
about the name suggests it is a bonding notification. This one was added
specifically to notify userspace (d4261e5650004), yet seems to happen
only during a changelink and that already generates a RTM_NEWLINK
message via do_setlink. Since the rtnetlink_event message does not
contain anything "NETDEV_CHANGEINFODATA" related what purpose does it
really serve besides duplicating netlink messages to userspace.

The REBOOT, IGMP, FEAT_CHANGE and BONDING_FAILOVER seem to be unique
messages (code analysis only) which I get for notifying userspace.

NETDEV_NOTIFY_PEERS is not so clear in how often it duplicates other
messages.