netdev - Re: [PATCH net-next] net: netdevsim: Support setting dev->perm

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Message-ID: <4b9a6e08-df15-44c1-accd-8f157c62849f@lunn.ch>
Date: Tue, 4 Feb 2025 00:04:09 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Toke Høiland-Jørgensen <toke@...hat.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: netdevsim: Support setting dev->perm_addr

On Mon, Feb 03, 2025 at 02:39:58PM -0800, Jakub Kicinski wrote:
> On Mon, 03 Feb 2025 18:21:24 +0100 Toke Høiland-Jørgensen wrote:
> > Network management daemons that match on the device permanent address
> > currently have no virtual interface types to test against.
> > NetworkManager, in particular, has carried an out of tree patch to set
> > the permanent address on netdevsim devices to use in its CI for this
> > purpose.
> > 
> > To support this use case, add a debugfs file for netdevsim to set the
> > permanent address to an arbitrary value.
> 
> netdevsim is not for user space testing. We have gone down the path
> of supporting random features in it already, and then wasted time trying
> to maintain them thru various devlink related perturbations, just to
> find out that the features weren't actually used any more.
> 
> NetworkManager can do the HW testing using virtme-ng.
> 
> If you want to go down the netdevsim path you must provide a meaningful 
> in-tree test, but let's be clear that we will 100% delete both the test
> and the netdevsim functionality if it causes any issues.

Hi Toke

What are your actual requirements? A permanent address is not expected
to change, it is by definition, permanent. Could it be hard coded in
netdevsim that the first instance created gets the MAC address
24:42:42:42:42:42? And maybe to make testing a bit more evil, keep the
current behaviour that the actually used MAC is random, since that MAC
address is not permanent.

	Andrew