netdev - Re: [PATCH net-next] rtnetlink: Allow setting IFLA_PERM

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Message-ID: <87zfij57t8.fsf@toke.dk>
Date: Tue, 18 Feb 2025 21:14:43 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
 <horms@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] rtnetlink: Allow setting IFLA_PERM_ADDRESS at
 device creation time

Jakub Kicinski <kuba@...nel.org> writes:

> On Tue, 18 Feb 2025 13:51:42 +0100 Toke Høiland-Jørgensen wrote:
>> >> Hmm, and you don't see any value in being able to specify a permanent
>> >> identifier for virtual devices? That bit was not just motivated
>> >> reasoning on my part... :)  
>> >
>> > I can't think of any :( Specifying an address is already possible.  
>> 
>> Right, but the address can be changed later. Setting the perm_addr makes
>> it possible for a management daemon to set a unique identifier at device
>> creation time which is guaranteed to persist through any renames and
>> address changes that other utilities may perform. That seems like a
>> useful robustness feature that comes at a relatively low cost (the patch
>> is fairly small and uncomplicated)?
>> 
>> > Permanent address is a property of the hardware platform.
>> > Virtual devices OTOH are primarily used by containers, 
>> > which are ephemeral by design. At least that's my mental model.  
>> 
>> Sure, any device feature that comes from hardware is only going to fit
>> virtual devices by analogy. But I don't think the analogy here is super
>> far fetched (cf the above)? :)
>
> I'm not sure how to answer this. It all sounds really speculative
> and disconnected with how I see virtual devices being used.


Alright fine - I'll respin the netdevsim patch instead...

-Toke