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jochen 5c212531da avahi: the discovery daemon declared, and why it hears nothing reported

On all four machines and owned by none. The module declares the package and
the daemon. It leaves nsswitch.conf and nss-mdns as found — the hosts: line is
one list every name source shares, and the host writes blocks, not line
members — and opens nothing: the mesh's filter drops inbound UDP 5353 on every
machine and `listens` has no local-link scope. avahi_status, _browse, _resolve
and _services report both (to-be 42 Phase 1).

2026-10-04 12:50:20 +02:00

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avahi

The local network's name and service discovery (mDNS/DNS-SD) as a module (novox/hq to-be 42 Phase 1, research 027).

What it owns

The avahi package.
avahi-daemon.service, running and enabled.

What it improves

It was on all four machines and owned by none. It is now declared, and its tools show why discovery does not work today:

The packet filter drops mDNS. The mesh's filter has no rule for inbound UDP 5353 on any of the four machines, so avahi announces this machine but hears no other machine's answers. A browse finds nothing, and resolving even the machine's own .local name times out. A module's listens can reach the private network, this machine or anywhere, but not the local link. Opening the port to anywhere would answer the internet on a public machine, so the module opens nothing. This needs a decision in novox/hq: a local-link source scope for listens. Until then, avahi_status reports inbound_mdns_accepted: false, and browse and resolve say so whenever they hear nothing.

What it leaves found

nss-mdns and /etc/nsswitch.conf. An ordinary lookup reaches avahi only through the hosts: line. That line is one ordered list shared by every name source: containers, files, DNS, mDNS and the resolver daemon. The host can write a marked block into a file, but it cannot add a member to a line. Owning the whole file would make this module the owner of every machine's name resolution. On 2026-10-04 all four machines had the same file, with mdns4_minimal wired by hand and nss-mdns installed. Both are left as found, and avahi_status reports the wiring.
/etc/avahi/avahi-daemon.conf, including each workstation's hand-set allow-interfaces, which names that machine's own network interface.

Tools

tool		answers
`avahi_status`	r	the daemon, its version and configuration, the `hosts:` line and whether mdns is on it, nss-mdns, whether the filter accepts inbound 5353, systemd-resolved beside it, and notes
`avahi_browse`	r	every service announced in a few seconds (`avahi-browse -prt`), resolved where possible, narrowed to a type
`avahi_resolve`	r	a `.local` name through avahi and through the name service side by side, or an address to its name
`avahi_services`	r	what this machine publishes from `/etc/avahi/services`

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