Re: [PATCH 0/6] Deprecate Legacy IP

Fernando Fernandez Mancera
2026-04-01T08:07:20Z

On 4/1/26 9:44 AM, David Woodhouse wrote:
> RFC1883, the IPv6 standard, was published in the final decade of the 1900s.
> That's closer in time to the Apollo 11 moon landing than it was to today.
>
> Even our esteemed Maddog has worked with computers for longer in the IPv6
> era, than he ever did before it.
>
> Yet Linux still can't even be *built* with only IPv6 support and without
> support for Legacy IP. This long overdue patch series fixes that, and
> immediately marks Legacy IP for deprecation.
>
> It also cleans up a few tautological "INET && IPV6" and "INET || IPV6"
> checks, since IPV6 (and now LEGACY_IP) cannot be selected without the
> overall CONFIG_INET option.
>
> For now, we only add a warning when a process *listens* on a Legacy IP
> socket (since you can listen on IPv6 and still accept connections which
> have come through a timewarp from the 20th century. Adding warnings for
> making outbound connections or *accepting* on Legacy IP can come later.
>
> 'I would be happy if "Legacy IP" ceased to be the "industry standard"
> and IPv6 be the default, even if I had to beat IPv6 into the head of
> every single network administrator's head with a shovel.' said Jon
> 'maddog' Hall, ancient supporter of Free and Open Source Software.
>

Dammit, you've beaten me to it! This was my next step for 7.2.

Fully-endorsed-by: Fernando Fernandez Mancera <fmancera@suse.de>