Hi Michael and Laurent, I talked to Michael yesterday and that deepened my understanding of the conflict. I'm giving a summary here. I appreciate feedback on the accuracy.
For one thing, I now perceive consensus on avahi-daemon providing mDNS functonality when both are installed. As such the actual conflict is the behaviour of systemd-resolved when avahi-daemon is not installed. Where Laurent and Michael believe mDNS functionality should be default-disabled, Luca thinks it should be enabled. Once a decision is made on this aspect, the rest of the matter becomes relatively obvious. In the default-disabled, the there is nothing more to do. In the default-enabled case, the change drafted by Luca can be applied to mDNS. On Thu, Jan 02, 2025 at 11:01:51AM +0100, Helmut Grohne wrote: > Another proposed solution is to have avahi-daemon disable mDNS > functionality in resolved by dropping a configuration file for resolved > containing MulticastDNS=no. Luca Bocassi is in favour of this approach > whereas Michael Biebl expressed concern. Arguments in favour of enabling mDNS in resolved by default: * It is default-enabled by systemd upstream. * mDNS resolution should just work by default. * Luca is a systemd maintainer and this decision normally is up to him. * mDNS is default-enabled in Arch. https://gitlab.archlinux.org/archlinux/packaging/packages/systemd/-/blob/main/PKGBUILD?ref_type=heads * mDNS is default-enabled in OpenSUSE. https://build.opensuse.org/projects/openSUSE:Factory/packages/systemd/files/systemd.spec?expand=1 Arguments in favour of disabling mDNS in resolved by default: * mDNS is default-disabled in Fedora. https://src.fedoraproject.org/rpms/systemd/blob/rawhide/f/systemd.spec#_832 * mDNS is default-disabled in Ubuntu. https://git.launchpad.net/ubuntu/+source/systemd/tree/debian/rules#n24 * mDNS is default-disabled in SteamOS. https://github.com/systemd/systemd/issues/6602#issuecomment-1859241687 * Having avahi-daemon disable mDNS in resolved is surprising and may confuse users. There is no precedent for one service disabling another in Debian. (e.g. installing rsyslog does not disable the persistent journal) * Downstream projects may require avahi-specific functionality and become subtly broken when working with resolved. (details missing) * The systemd-resolved implementation of mDNS is not yet seen as sufficiently mature. (details missing) * avahi-daemon has significant reverse dependencies and recommenders causing it to show up in typical desktop installations. It should remain the only default-enabled mDNS resolver for the time being. This gives rise possible CTTE actions. (O) The CTTE overrules the systemd maintainers and requires mDNS to be default-disabled in systemd-resolved for the trixie release. (Requires a 3:1 majority overruling a developer.) (D) The CTTE decleines to overrule the systemd maintainers regarding the default of mDNS in systemd-resolved and recommends that avahi-daemon disables mDNS in systemd-resolved upon its installation. (F) Further discussion. Helmut Helmut
