netdev - Re: [PATCH net-next v2] netconsole: Enable live renaming for network interfaces used by netconsole

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Message-ID: <20221101204006.75b46660@kernel.org>
Date:   Tue, 1 Nov 2022 20:40:06 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Andy Ren <andy.ren@...cruise.com>, netdev@...r.kernel.org,
        richardbgobert@...il.com, davem@...emloft.net,
        wsa+renesas@...g-engineering.com, edumazet@...gle.com,
        petrm@...dia.com, pabeni@...hat.com, corbet@....net,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        roman.gushchin@...ux.dev
Subject: Re: [PATCH net-next v2] netconsole: Enable live renaming for
 network interfaces used by netconsole

On Wed, 2 Nov 2022 01:48:09 +0100 Andrew Lunn wrote:
> Changing the interface name while running is probably not an
> issue. There are a few drivers which report the name to the firmware,
> presumably for logging, and phoning home, but it should not otherwise
> affect the hardware.

Agreed. BTW I wonder if we really want to introduce a netconsole
specific uAPI for this or go ahead with something more general.
A sysctl for global "allow UP rename"?

We added the live renaming for failover a while back and there were 
no reports of user space breaking as far as I know. So perhaps nobody
actually cares and we should allow renaming all interfaces while UP?
For backwards compat we can add a sysctl as mentioned or a rtnetlink 
"I know what I'm doing" flag? 

Maybe print an info message into the logs for a few releases to aid
debug?

IOW either there is a reason we don't allow rename while up, and
netconsole being bound to an interface is immaterial. Or there is 
no reason and we should allow all.