Re: [v6ops] IPv6-Only Preferred DHCPv4 option

Philip Homburg <pch-v6ops-9@u-1.phicoh.com> Thu, 05 December 2019 08:49 UTC

Return-Path: <pch-b9D3CB0F5@u-1.phicoh.com>
X-Original-To: v6ops@ietfa.amsl.com
Delivered-To: v6ops@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 639121200F1 for <v6ops@ietfa.amsl.com>; Thu, 5 Dec 2019 00:49:29 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.499
X-Spam-Level:
X-Spam-Status: No, score=-1.499 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, KHOP_HELO_FCRDNS=0.399, SPF_HELO_NONE=0.001, SPF_NONE=0.001] autolearn=no autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id cUo1clbI06Rv for <v6ops@ietfa.amsl.com>; Thu, 5 Dec 2019 00:49:28 -0800 (PST)
Received: from stereo.hq.phicoh.net (stereo6-tun.hq.phicoh.net [IPv6:2001:888:1044:10:2a0:c9ff:fe9f:17a9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 8DC271200F6 for <v6ops@ietf.org>; Thu, 5 Dec 2019 00:49:28 -0800 (PST)
Received: from stereo.hq.phicoh.net (localhost [::ffff:127.0.0.1]) by stereo.hq.phicoh.net with esmtp (TLS version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384) (Smail #157) id m1icmpA-0000KmC; Thu, 5 Dec 2019 09:49:24 +0100
Message-Id: <m1icmpA-0000KmC@stereo.hq.phicoh.net>
To: v6ops@ietf.org
Cc: Lorenzo Colitti <lorenzo=40google.com@dmarc.ietf.org>
From: Philip Homburg <pch-v6ops-9@u-1.phicoh.com>
Sender: pch-b9D3CB0F5@u-1.phicoh.com
References: <CAFU7BAR1JLUZps=CAqJfeQtUf-xQ88RYvgYrPCP+QP0Ter7YFg@mail.gmail.com> <E03BBE6C-3BED-4D49-8F79-0A1B313EFD9D@apple.com> <28594.1575483729@localhost> <7ac18a46-31d9-74cc-117a-0fd908413aac@gmail.com> <9bd73ee1-46f7-5084-06a6-59c7b391f9cb@foobar.org> <CAKD1Yr0KPfFvk7Y49WkiVnm1q0E6i1u1hi4p_x56=p+kP9g=0g@mail.gmail.com> <CAO42Z2w1hK75xBEKfFH52ki9U5ZTC=RNSs4d+9K0PFAtMYa42A@mail.gmail.com> <CAKD1Yr1M-00APXU4F2dnf1aaTqp7wmuugKSC=Rn14wW5WPk+CA@mail.gmail.com>
In-reply-to: Your message of "Thu, 5 Dec 2019 11:19:52 +0900 ." <CAKD1Yr1M-00APXU4F2dnf1aaTqp7wmuugKSC=Rn14wW5WPk+CA@mail.gmail.com>
Date: Thu, 05 Dec 2019 09:49:24 +0100
Archived-At: <https://mailarchive.ietf.org/arch/msg/v6ops/qpEONhVdWs0YTsnr84y6sQ4fVQ4>
Subject: Re: [v6ops] IPv6-Only Preferred DHCPv4 option
X-BeenThere: v6ops@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: v6ops discussion list <v6ops.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/v6ops>, <mailto:v6ops-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/v6ops/>
List-Post: <mailto:v6ops@ietf.org>
List-Help: <mailto:v6ops-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/v6ops>, <mailto:v6ops-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 05 Dec 2019 08:49:29 -0000

>Speaking as an OS implementer: how do I know whether an application is an
>IPv4 application?
>
>   - When it calls getaddrinfo() with AF_UNSPEC? Pretty much all apps do
>   that.
>   - When it creates an IPv4 socket? But what if it's creating an IPv4
>   socket for the purpose of connecting to another network on the system
>   (e.g., cellular data) that does have IPv4?
>   - When it does a connect() on an IPv4 socket? But what if that's just a
>   happy eyeballs stack that is using IPv4 because it might be available?
>   - What if the app knows it needs IPv4 and will refuse to do any
>   networking if it doesn't find an IPv4 address on the system?

I agree with Lorenzo here. Changing a host to defer trying to get an IPv4
address while at the same time not showing any delay to the user when the
device connects to a new network would be an enormous amount of effort with
essentally no benefit to the vendor of the host device.