Bug#1091864: tech-ctte: Avahi and systemd-resolved cannot a run mDNS responder at the same time

[Josh Triplett <josh@joshtriplett.org>]

On Thu, 23 Jan 2025 18:27:03 +0100 Helmut Grohne <helmut@subdivi.de> wrote:
> Given that it was mentioned often enough, having a resolution reaffirm
> that avahi-daemon should be the default in either case seems fine to me.
> As such I now see the following possible ballot options:
> 
> (S) The CTTE reaffirms that avahi-daemon is the default mDNS
>     implementation in Debian trixie. Therefore systemd-resolved should
>     disable the mDNS functionality in its default installation in Debian
>     trixie.
>     (Requires a 3:1 majority overruling a developer.)
> 
> (A) The CTTE reaffirms that avahi-daemon is the default mDNS
>     implementation in Debian trixie. This does not preclude other
>     resolvers such as systemd-resolved operating when avahi-daemon is
>     not installed. To achieve this, avahi-daemon should disable
>     systemd-resolved using a resolved configuration file.
>     (Requires a 3:1 majority overruling a developer.)

If these end up being the options in front of the CTTE, please consider
doing A rather than S. The two are equivalent in terms of net effect,
but the latter would have two advantages over the former, and no obvious
disadvantage:

1) It would mean that mDNS works on more systems, which has the net
   effect of improving the usability of mDNS for everyone: more people
   expect `.local` names to Just Work, and expect systems to be findable
   via those names.

2) It would allow experimentation with enabling support for systemd as
   an mDNS responder for services. If systemd's mDNS responder were
   required to be disabled by default *even if avahi is not installed*,
   that would make it much harder to work on it as an alternative and
   gradually enable support for it.