[PATCH 01/10 net-next] ipv6: convert CONFIG_IPV6 to built-in only and clean up Kconfigs

[Arnd Bergmann]

On Tue, Mar 10, 2026, at 20:40, Kolbjørn Barmen wrote:
> On Mon, 9 Mar 2026, Krzysztof Kozlowski wrote:
>> On 09/03/2026 03:19, Fernando Fernandez Mancera wrote:
>>
>> It must stay module for me. Alternatively, drop it, but then some users
>> will be really affected.
>
> I agree. If anything I would prefer to see IPv4 be made optional (and
> modular) as well, and not as something IPv6 depends on, it's (AFAIK)
> impossible today to build an IPv6-only Linux kernel. 

My first feeling was that this is a bad idea as well. On the other hand
I found that the default changed from =m to -y over 10 years ago, all
recent distros listed in https://github.com/nyrahul/linux-kernel-configs
use that default (the only two exceptions are board specific builds
of Debian and Ubuntu for linux-5.x).

The list does not include openwrt though, and I know that in
previous releases, there was an optional kmod-ipv6 package
that could be left out of an install without rebuilding
the kernel. Configurations under 128MB are only partially
supported there these days, so maybe it's no longer important
for openwrt either, but it would be good to get a confirmation
from someone doing the packaging.

For optional IPv4 support, I would expect that it's possible
to make it a loadable module, with a significant amount of
work and little benefit. Loading an ipv6 module without also
loading ipv4 sounds completely unrealistic though, given
the way the code is structured today.

    Arnd