Issue 171: a module that names its own resolver knows no mesh name

Found and fixed the afternoon ADR 0148 landed: mailu-admin lost its
database behind Mailu's own resolver. Two catalogue PRs; an insight on
0148 that a container's dns is a decision, not a preference.

02-DECISIONS/0148-the-meshs-names-are-resolved-not-copied-into-containers.md

@@ -150,6 +150,16 @@ closed by this record, only answered by it.
   resolvable inside the mesh — holds unchanged and by the same means the machine already uses.
 - **Issue 110 stops being a container-DNS inconvenience and becomes a prerequisite** for the mesh not
   restarting itself whenever it learns a name.
+- **A container that names a resolver of its own has opted out of the machine's**, and the copy this
+  record removes was the only reason such a container could reach anything by a mesh name.
+
+  > **Progressive insight — 2026-09-30, the afternoon this landed. Found the hard way.** The mail
+  > system's admin, behind Mailu's own resolver, lost its database the moment the copy went
+  > ([issue 171](../04-ISSUES/171-a-modules-own-resolver-knows-no-mesh-name/00-report.md)). A `dns` on
+  > a container is a decision about whether mesh names exist inside it, not a preference; the module
+  > was corrected, and whether the controller should refuse the contradiction is that issue's open
+  > question.
+
 - **A container started by hand gets the mesh's names too**, where before only declared containers did.
   Design 08 drew that boundary deliberately, on the grounds that reaching into every container is what
   a nameserver would be for. This record accepts that consequence rather than working around it: a

04-ISSUES/171-a-modules-own-resolver-knows-no-mesh-name/00-report.md

@@ -0,0 +1,78 @@
+---
+status: resolved
+opened: 2026-09-30
+located-in:
+  - mesh-catalog modules/mailu (eight containers name Mailu's own resolver, and one of them binds a mesh name)
+  - mesh-catalog modules/dnsmasq (dropped the DNSSEC bit its upstreams set)
+fixed-by: mesh-catalog PR 178 (mailu-admin uses the machine's resolver) and PR 179 (the machine's resolver passes the DNSSEC bit down) — 2026-09-30, the same afternoon
+amended-design:
+---
+
+# 171 — A module that names its own resolver knows no mesh name
+
+## What was observed
+
+The afternoon [ADR 0148](../../02-DECISIONS/0148-the-meshs-names-are-resolved-not-copied-into-containers.md)
+landed — no container is given the mesh's names any more; it asks the machine's resolver — the mail
+system's admin container began logging, 523 times in three minutes:
+
+```
+psycopg2.OperationalError: could not translate host name "novox.internal" to address: Name does not resolve
+```
+
+Mail was accepted on every port and the web front answered; the admin and the spam filter beside it
+were unhealthy, and anything that needed the database — a mailbox change through the API, the spam
+filter's domain list — failed. Found by the operator asking whether mail was back, forty minutes in.
+
+Mailu ships its own resolver, an unbound in a container, and every other Mailu container is told to
+use it — the module carries `dns: [192.168.203.254]` on eight containers. That resolver recurses from the
+root and knows nothing under `.internal`. Until that afternoon the admin container had the database's
+name anyway, because the mesh wrote every name into every container at creation; the copy was the only
+reason a container behind its own resolver could reach anything by a mesh name, and nobody knew it was
+load-bearing.
+
+**Removing the override was not enough.** Given the machine's resolver instead, the admin refused to
+start: `Your DNS resolver at 127.0.0.11 isn't doing DNSSEC validation`. Mailu checks, at start, that
+its resolver returns the Authenticated Data bit for a signed name. The mesh's resolver forwards to two
+upstreams that validate and set the bit, and dropped it on the way down — dnsmasq does unless told
+otherwise. Mailu's own unbound has no hook to forward a zone elsewhere, so it could not be taught the
+mesh's names either.
+
+## Why it matters beyond this instance
+
+**A container with a resolver of its own has opted out of the machine's, and nothing says so.** 0148
+made the machine's resolver load-bearing for every container; a `dns` on a container is a quiet
+exception to that, and the exception used to be papered over by the copy the record removed. The
+manifest field reads like a preference and is a decision about whether mesh names exist inside the
+container.
+
+**A resolver that forwards to validating upstreams and hides the fact is less useful than it could
+be**, and the first program to check found out.
+
+**The mesh reported nothing.** Every container ran; the failing one accepted connections; the report
+was about bytes. It is [issue 145](../145-a-machine-reads-healthy-while-its-modules-cannot-reach-each-other/00-report.md)
+again, and the check that would have caught it is the same unbuilt one.
+
+## What was done
+
+- The one Mailu container that binds a mesh name — the admin, through the database it is granted —
+  no longer names Mailu's resolver and uses the machine's, like every container without a `dns` of
+  its own (mesh-catalog PR 178). The other seven keep unbound: the spam filter needs a validating
+  resolver for its blocklist lookups, and none of them asks for a mesh name.
+- The machine's resolver passes the DNSSEC bit down from its upstreams, `proxy-dnssec` (PR 179). It
+  does not validate itself; the trust is the upstream's and the path to it, as a forwarding resolver's
+  always was, and the configuration says so.
+
+## What checks it
+
+The admin container's own start-up check, which is what failed, and the mesh's status once it reads
+healthy. A container-level check that a mesh name resolves from inside every declared container is
+the one 110 and 145 both ask for and is not built.
+
+## Open questions
+
+- Should a container's `dns` be refused, or made to say what it gives up? A module that names its
+  own resolver and binds a mesh name is a contradiction the controller can see at composition — the
+  grant hands it a name its resolver will not answer.
+- Should the machine's resolver validate rather than proxy? It would cost a trust anchor on every
+  machine and make the resolver slower to start; proxying was enough for the one program that asked.