jochen
5c212531da
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).
43 lines
2.3 KiB
Markdown
43 lines
2.3 KiB
Markdown
# avahi
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The local network's name and service discovery (mDNS/DNS-SD) as a module (novox/hq to-be 42 Phase 1,
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research 027).
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## What it owns
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- The `avahi` package.
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- `avahi-daemon.service`, running and enabled.
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## What it improves
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It was on all four machines and owned by none. It is now declared, and its tools show why discovery
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does not work today:
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- **The packet filter drops mDNS.** The mesh's filter has no rule for inbound UDP 5353 on any of the
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four machines, so avahi announces this machine but hears no other machine's answers. A browse
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finds nothing, and resolving even the machine's own `.local` name times out. A module's `listens`
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can reach the private network, this machine or anywhere, but not the local link. Opening the port
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to anywhere would answer the internet on a public machine, so the module opens nothing. This needs
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a decision in novox/hq: a local-link source scope for `listens`. Until then, `avahi_status` reports
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`inbound_mdns_accepted: false`, and browse and resolve say so whenever they hear nothing.
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## What it leaves found
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- **`nss-mdns` and `/etc/nsswitch.conf`.** An ordinary lookup reaches avahi only through the
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`hosts:` line. That line is one ordered list shared by every name source: containers, files, DNS,
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mDNS and the resolver daemon. The host can write a marked block into a file, but it cannot add a
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member to a line. Owning the whole file would make this module the owner of every machine's name
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resolution. On 2026-10-04 all four machines had the same file, with `mdns4_minimal` wired by hand
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and nss-mdns installed. Both are left as found, and `avahi_status` reports the wiring.
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- `/etc/avahi/avahi-daemon.conf`, including each workstation's hand-set `allow-interfaces`, which
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names that machine's own network interface.
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## Tools
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| tool | | answers |
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|---|---|---|
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| `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 |
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| `avahi_browse` | r | every service announced in a few seconds (`avahi-browse -prt`), resolved where possible, narrowed to a type |
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| `avahi_resolve` | r | a `.local` name through avahi and through the name service side by side, or an address to its name |
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| `avahi_services` | r | what this machine publishes from `/etc/avahi/services` |
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