netdev - Re: net: ipconfig: dev_set_mtu call is incompatible with a number of Ethernet drivers

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Message-ID: <58519bfa-260c-4745-a145-fdca89b4e9d1@kernel.org>
Date: Fri, 15 Dec 2023 09:49:45 -0800
From: David Ahern <dsahern@...nel.org>
To: Graeme Smecher <gsmecher@...eespeedlogic.com>, davem@...emloft.net
Cc: netdev@...r.kernel.org, claudiu.beznea@...on.dev,
 nicolas.ferre@...rochip.com, mdf@...nel.org
Subject: Re: net: ipconfig: dev_set_mtu call is incompatible with a number of
 Ethernet drivers

On 12/14/23 12:07 PM, Graeme Smecher wrote:
> Hi all,
> 
> In a number of ethernet drivers, the MTU can't be changed on a running
> device. Here's one example (from drivers/net/ethernet/cadence/macb_main.c):
> 

...

> 
> So - what to do? I can see three defensible arguments:
> 
> - The network drivers should allow MTU changes on-the-fly (many do), or
> - The ipconfig code could bring the adapter down and up again, or

looking at the ordering, bringing down the selected device to change the
MTU seems the more reasonable solution.

> - This is out-of-scope, and I should be reconfiguring the interface in
> userspace anyways.
>