Re: [PATCH net-next v5 09/22] ethtool: implement EVENT notifications

[Michal Kubecek]

On Wed, Mar 27, 2019 at 02:04:28PM +0100, Jiri Pirko wrote:
> Mon, Mar 25, 2019 at 06:08:21PM CET, mkubecek@xxxxxxx wrote:
> >Three types of netlink notifications are introduced:
> >
> >  - ETHA_EVENT_NEWDEV to notify about newly registered network devices
> >  - ETHA_EVENT_DELDEV to notify about unregistered network devices
> >  - ETHA_EVENT_RENAMEDEV to notify about renamed network device
> >
> >The notifications are triggered by NETDEV_REGISTER, NETDEV_UNREGISTER and
> >NETDEV_CHANGENAME notifiers.
> >
> >These notifications are intended for applications and daemons monitoring
> >ethtool events to allow updating the list of existing devices without
> >having to open another socket for rtnetlink.
> 
> Wait. You duplicate events that are already going out through RTNETLINK.
> App should open RTNETLINK in order to get those. Other apps are doing
> that too. I don't think that duplications like this are desirable :/

Is there a way to filter or at least recognize these events when using
rtnetlink? I couldn't find any. The only way seems to be getting every
RTM_NEWLINK message (there can be quite a lot of those), always perform
the lookup in my device list and recognize what happened - only to
almost always find that nothing interesting. It is possible, sure, but
I would really like to avoid it.

Michal