Re: [v6ops] IPv6-Only Preferred DHCPv4 option

[Lorenzo Colitti <[e-mail]>]

On Mon, Dec 9, 2019 at 11:17 PM Ted Lemon <[e-mail]> wrote:

> One way to resolve this impasse would be to specify it do it would *work*
> with your minimal change, but *also* allow the server to send no address
> in the offer. That way you can implement the full change at your leisure,
> but we still get a good long term outcome.
>

>From the perspective of a host OS developer and not a server developer,
that seems like a good compromise. I hadn't thought of the "I just want a
little stub on my network" argument. Though I'd wager it will be more than
ten years before every network has one of those, it does seem like a nice
minimalist approach especially good for small/home networks where we don't
expect there to be any middleboxes to choke on an offer for 0.0.0.0.

If we want hosts to support this (and we do, because otherwise even on such
networks hosts might choke on the offer for 0.0.0.0) it should be in the
document from day one and we should say that if the host gets 0.0.0.0 in
the offer and a v6only-preferred option it MUST operate in IPv6-only mode
and MUST NOT send a request for the address.

Presumably what happens if the host gets 0.0.0.0 in the offer and no
v6only-preferred option is left to the implementer. Just as a data point,
the Android implementation will ignore it and continue to send discover
packets. At the moment I can't remember why I did that and I don't know
what other implementations do.