netdev - Re: [RFC PATCH net-next v3 07/21] ethtool: implement EVENT notifications

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Date:   Tue, 19 Feb 2019 08:02:26 +0100
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jiri Pirko <jiri@...nulli.us>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net-next v3 07/21] ethtool: implement EVENT
 notifications

On Tue, Feb 19, 2019 at 12:46:08AM +0100, Andrew Lunn wrote:
> On Mon, Feb 18, 2019 at 07:21:59PM +0100, Michal Kubecek 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.
> 
> Hi Michal
> 
> Does ETHA_EVENT_RENAMEDEV actually contain enough information to avoid
> needing a rtnetlink lookup? If i understand the code correctly, all
> you have is the new name. You don't know the old name?
> 
> Having said that, i don't see an easy way to get access to the old
> name when handling the NETDEV_CHANGENAME.

We don't have the old name and without modifying the NETDEV_CHANGENAME
notifier to pass it, there is probably no way to get it. But the ethtool
notification also contains ifindex so that userspace applications which
want to track the configuration can remember both and identify the
renamed device by ifindex.

Michal