Re: [PATCH 01/13 RFC net-next] net: ipv4: introduce CONFIG_IPV4 to decouple the IPv4 stack

On Sun, Jul 12, 2026, at 03:38, Fernando Fernandez Mancera wrote:

Historically, the IPv4 protocol has been linked to the core INET
subsystem. Because shared infrastructure like the TCP/UDP engine,
routing or INET hashtables live inside net/ipv4/, it has been impossible
to compile a kernel with only IPv6 support.

This patch introduces the CONFIG_IPV4 Kconfig symbol, which is set to
'def_bool y' for now. This does not allow to completely disable the
IPv4 stack yet but it lays the necessary build-system work for that
goal.

I expect this will cause additional (trivial) build regression in the
next step when randconfig builds run into obscure corner cases, either
with INET=y IPV4=n IPV6=y or with INET=y IPV4=n IPV6=n.

I can probably give your patch (with IPV4 visible or disabled) an
early go on the randconfig tree to find these more quickly.
If I run into regressions, should I just add more 'depends on IPV4',
or do you have other plans?

Should we have some logic to ensure that at least one of IPV4 or
IPV6 is enabled? I think this would work

config IPV4
      bool "The IPv4 protocol" if IPV6
      default INET

which only allows turning IPV4 off if IPV6 has enabled.

       Arnd