Re: [PATCH v3 2/2] netconsole: allow selection of egress interface via MAC address

[Jakub Kicinski]

On Wed, 05 Feb 2025 22:21:31 -0700 Uday Shankar wrote:
> Currently, netconsole has two methods of configuration - module
> parameter and configfs. The former interface allows for netconsole
> activation earlier during boot (by specifying the module parameter on
> the kernel command line), so it is preferred for debugging issues which
> arise before userspace is up/the configfs interface can be used. The
> module parameter syntax requires specifying the egress interface name.
> This requirement makes it hard to use for a couple reasons:
> - The egress interface name can be hard or impossible to predict. For
>   example, installing a new network card in a system can change the
>   interface names assigned by the kernel.
> - When constructing the module parameter, one may have trouble
>   determining the original (kernel-assigned) name of the interface
>   (which is the name that should be given to netconsole) if some stable
>   interface naming scheme is in effect. A human can usually look at
>   kernel logs to determine the original name, but this is very painful
>   if automation is constructing the parameter.
> 
> For these reasons, allow selection of the egress interface via MAC
> address when configuring netconsole using the module parameter. Update
> the netconsole documentation with an example of the new syntax.
> Selection of egress interface by MAC address via configfs is far less
> interesting (since when this interface can be used, one should be able
> to easily convert between MAC address and interface name), so it is left
> unimplemented.

Sounds like dev_getbyhwaddr_rcu() will warn here. Either wrap it 
in  RCU temporarily or combine the series with Breno's patch to 
add a new helper?
-- 
pw-bot: cr