netdev - Re: [PATCH net-next v25 01/23] net: introduce OpenVPN Data Channel Offload (ovpn)

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Message-ID: <Z_keORW4OWc8i5Vz@krikkit>
Date: Fri, 11 Apr 2025 15:50:49 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: Antonio Quartulli <antonio@...nvpn.net>
Cc: Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Donald Hunter <donald.hunter@...il.com>,
	Shuah Khan <shuah@...nel.org>, ryazanov.s.a@...il.com,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Simon Horman <horms@...nel.org>, linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org, Xiao Liang <shaw.leon@...il.com>,
	steffen.klassert@...unet.com, antony.antony@...unet.com
Subject: Re: [PATCH net-next v25 01/23] net: introduce OpenVPN Data Channel
 Offload (ovpn)

2025-04-11, 10:04:10 +0200, Antonio Quartulli wrote:
> Hi Jakub,
> 
> thanks for taking the time to go through my patchset :)
> 
> On 11/04/2025 04:54, Jakub Kicinski wrote:
> > On Mon, 07 Apr 2025 21:46:09 +0200 Antonio Quartulli wrote:
> > > +static int ovpn_netdev_notifier_call(struct notifier_block *nb,
> > > +				     unsigned long state, void *ptr)
> > > +{
> > > +	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> > > +
> > > +	if (!ovpn_dev_is_valid(dev))
> > > +		return NOTIFY_DONE;
> > > +
> > > +	switch (state) {
> > > +	case NETDEV_REGISTER:
> > > +		/* add device to internal list for later destruction upon
> > > +		 * unregistration
> > > +		 */
> > > +		break;
> > > +	case NETDEV_UNREGISTER:
> > > +		/* can be delivered multiple times, so check registered flag,
> > > +		 * then destroy the interface
> > > +		 */
> > > +		break;
> > > +	case NETDEV_POST_INIT:
> > > +	case NETDEV_GOING_DOWN:
> > > +	case NETDEV_DOWN:
> > > +	case NETDEV_UP:
> > > +	case NETDEV_PRE_UP:
> > > +	default:
> > > +		return NOTIFY_DONE;
> > > +	}
> > 
> > Why are you using a notifier to get events for your own device?
> 
> My understanding is that this is the standard approach to:
> 1) hook in the middle of registration/deregistration;
> 2) handle events generated by other components/routines.
> 
> I see in /drivers/net/ almost every driver registers a notifier for their
> own device.

I think most of them register a notifier for their lower device
(bridge port, real device under a vlan, or similar).

I've mentioned at some point that it would be more usual to replace
this notifier with a custom dellink, and that ovpn->registered could
likely be replaced with checking for NETREG_REGISTERED. I just thought
it could be cleaned up a bit later, but it seems Jakub wants it done
before taking the patches :)

-- 
Sabrina