ifupdown behaviour with IPv6 DAD failure (Was: proposal: Hybrid network stack for Trixie)

From	Daniel Gröber <dxld@darkboxed.org>
Newsgroups	linux.debian.devel
Subject	ifupdown behaviour with IPv6 DAD failure (Was: proposal: Hybrid network stack for Trixie)
Date	2024-09-23 13:50 +0200
Message-ID	<JpPJL-egZP-1@gated-at.bofh.it> (permalink)
References	<JoJQ7-dBrt-9@gated-at.bofh.it> <JpNHX-efOk-1@gated-at.bofh.it> <JpOum-eglq-17@gated-at.bofh.it>
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On Mon, Sep 23, 2024 at 12:25:15PM +0200, Chris Hofstaedtler wrote:
> * Pierre-Elliott Bécue <peb@debian.org> [240923 11:34]:
> > I like ifupdown. It's simple and just works.
> 
> I find this quite funny, given a recent discussion about IPv6 dad
> issues with ifupdown on #debian-admin.

The "discussion" was about ifup@eth0 being in a failed state on a
particular server due to a DAD failure and someone having to manually
intervene.

Chris, what behaviour do you expect here? Below I'm going to assume what
you're getting at is that we should continue to retry DAD.

To me going to a stable failure state seems desirable. Continuing to re-try
for IPs could cause instability in the face of legitimate address
conflicts: when the owning machine reboots the conflicting machine would
now win the IP due to continous retrying. The change in owner would cause
disruption to services entirely unrelated to the machine that was just
rebooted.

Sounds like the setup for a very drawn out and frustrating debugging story
to me.

--Daniel

PS: I was wondering if the RFCs have anything to say on the matter:
[ADDRCONF] says:

> 5.4.5.  When Duplicate Address Detection Fails
> 
>    [...] If the address is a link-local address formed from an interface
>    identifier, the interface SHOULD be disabled.

[Enhanced DAD] while not directly applicable seems to be under the
impression that manual intervention is the "current behaviour":

> 3.3.  Operational Considerations
> 
>    [...]the noncompliant device would
>    follow current behavior and disable IPv6 on that interface due to DAD
>    until manual intervention restores it.

[ADDRCONF]: RFC 2462 - IPv6 Stateless Address Autoconfiguration
[Enhanced DAD]: RFC 7527 - Enhanced Duplicate Address Detection

Thread

proposal: Hybrid network stack for Trixie Lukas Märdian <slyon@debian.org> - 2024-09-20 13:20 +0200
  Re: proposal: Hybrid network stack for Trixie Marco d'Itri <md@Linux.IT> - 2024-09-20 15:50 +0200
    Re: proposal: Hybrid network stack for Trixie Bill MacAllister <bill@ca-zephyr.org> - 2024-09-20 22:20 +0200
  Re: proposal: Hybrid network stack for Trixie Chris Hofstaedtler <zeha@debian.org> - 2024-09-22 12:30 +0200
    Re: proposal: Hybrid network stack for Trixie Marc Haber <mh+debian-devel@zugschlus.de> - 2024-09-22 13:10 +0200
      Re: proposal: Hybrid network stack for Trixie Chris Hofstaedtler <zeha@debian.org> - 2024-09-22 13:50 +0200
        Re: proposal: Hybrid network stack for Trixie "Jonathan Dowland" <jmtd@debian.org> - 2024-09-22 16:50 +0200
          Re: proposal: Hybrid network stack for Trixie "Andrew M.A. Cater" <amacater@einval.com> - 2024-09-22 17:20 +0200
        Re: proposal: Hybrid network stack for Trixie Hakan Bayındır <hakan@bayindir.org> - 2024-09-22 23:30 +0200
    Re: proposal: Hybrid network stack for Trixie Simon McVittie <smcv@debian.org> - 2024-09-22 13:10 +0200
      Re: proposal: Hybrid network stack for Trixie Josh Triplett <josh@joshtriplett.org> - 2024-09-22 20:10 +0200
        Re: proposal: Hybrid network stack for Trixie "Andrea Pappacoda" <andrea@pappacoda.it> - 2024-09-22 22:40 +0200
          Re: proposal: Hybrid network stack for Trixie Josh Triplett <josh@joshtriplett.org> - 2024-09-23 00:10 +0200
            Re: proposal: Hybrid network stack for Trixie Lukas Märdian <slyon@debian.org> - 2024-09-23 12:40 +0200
    Re: proposal: Hybrid network stack for Trixie Lukas Märdian <slyon@debian.org> - 2024-09-23 13:10 +0200
      Re: proposal: Hybrid network stack for Trixie Marco d'Itri <md@Linux.IT> - 2024-09-23 14:10 +0200
      Re: proposal: Hybrid network stack for Trixie Marvin Renich <mrvn@renich.org> - 2024-09-23 14:50 +0200
      Re: proposal: Hybrid network stack for Trixie Didier 'OdyX' Raboud <odyx@debian.org> - 2024-09-23 15:00 +0200
      Re: proposal: Hybrid network stack for Trixie Daniel Baumann <daniel@debian.org> - 2024-09-24 08:10 +0200
    Re: proposal: Hybrid network stack for Trixie Simon Richter <sjr@debian.org> - 2024-09-24 14:20 +0200
  Re: proposal: Hybrid network stack for Trixie Ansgar 🙀 <ansgar@debian.org> - 2024-09-22 16:30 +0200
    Re: proposal: Hybrid network stack for Trixie Lukas Märdian <slyon@debian.org> - 2024-09-23 12:30 +0200
      Re: proposal: Hybrid network stack for Trixie Ansgar 🙀 <ansgar@debian.org> - 2024-09-23 12:50 +0200
        Re: proposal: Hybrid network stack for Trixie Lukas Märdian <slyon@debian.org> - 2024-09-23 13:20 +0200
          Re: proposal: Hybrid network stack for Trixie Richard Lewis <richard.lewis.debian@googlemail.com> - 2024-09-23 13:40 +0200
            Re: proposal: Hybrid network stack for Trixie Lukas Märdian <slyon@debian.org> - 2024-09-24 15:40 +0200
              Re: proposal: Hybrid network stack for Trixie Ansgar 🙀 <ansgar@debian.org> - 2024-09-27 10:10 +0200
          Re: proposal: Hybrid network stack for Trixie Bjørn Mork <bjorn@mork.no> - 2024-09-23 14:20 +0200
        Re: proposal: Hybrid network stack for Trixie Steve Langasek <vorlon@debian.org> - 2024-09-27 20:20 +0200
          Re: proposal: Hybrid network stack for Trixie Ansgar 🙀 <ansgar@debian.org> - 2024-09-27 21:10 +0200
  Re: proposal: Hybrid network stack for Trixie Sirius <sirius@trudheim.com> - 2024-09-22 17:50 +0200
    Re: proposal: Hybrid network stack for Trixie Jonas Smedegaard <jonas@jones.dk> - 2024-09-22 23:50 +0200
      Re: proposal: Hybrid network stack for Trixie Sirius <sirius@trudheim.com> - 2024-09-23 08:30 +0200
        ifupdown-ng source stanza (Was: proposal: Hybrid network stack for  Trixie) Daniel Gröber <dxld@darkboxed.org> - 2024-09-23 11:00 +0200
          Re: ifupdown-ng source stanza (Was: proposal: Hybrid network stack  for Trixie) Sirius <sirius@trudheim.com> - 2024-09-24 13:40 +0200
  Re: proposal: Hybrid network stack for Trixie Holger Levsen <holger@layer-acht.org> - 2024-09-23 10:10 +0200
    Re: proposal: Hybrid network stack for Trixie Chris Hofstaedtler <zeha@debian.org> - 2024-09-23 10:20 +0200
      Re: proposal: Hybrid network stack for Trixie Holger Levsen <holger@layer-acht.org> - 2024-09-23 10:30 +0200
        Re: proposal: Hybrid network stack for Trixie Marco d'Itri <md@Linux.IT> - 2024-09-23 11:10 +0200
          Re: proposal: Hybrid network stack for Trixie Lukas Märdian <slyon@debian.org> - 2024-09-23 12:10 +0200
          Re: proposal: Hybrid network stack for Trixie Holger Levsen <holger@layer-acht.org> - 2024-09-23 12:10 +0200
            Re: proposal: Hybrid network stack for Trixie Chris Hofstaedtler <zeha@debian.org> - 2024-09-23 12:30 +0200
  Re: proposal: Hybrid network stack for Trixie Pierre-Elliott Bécue <peb@debian.org> - 2024-09-23 11:40 +0200
    Re: proposal: Hybrid network stack for Trixie Chris Hofstaedtler <zeha@debian.org> - 2024-09-23 12:30 +0200
      ifupdown behaviour with IPv6 DAD failure (Was: proposal: Hybrid  network stack for Trixie) Daniel Gröber <dxld@darkboxed.org> - 2024-09-23 13:50 +0200
        Re: ifupdown behaviour with IPv6 DAD failure (Was: proposal: Hybrid  network stack for Trixie) Philipp Kern <pkern@debian.org> - 2024-09-23 17:50 +0200
          Re: ifupdown behaviour with IPv6 DAD failure (Was: proposal: Hybrid  network stack for Trixie) Noah Meyerhans <noahm@debian.org> - 2024-09-24 00:20 +0200
      Re: proposal: Hybrid network stack for Trixie Pierre-Elliott Bécue <peb@debian.org> - 2024-09-24 10:50 +0200
  Re: proposal: Hybrid network stack for Trixie Antoine Beaupré <anarcat@debian.org> - 2024-10-07 18:30 +0200

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