feat(pihole): authoritative LAN DNS for the zone on udp/53 + tcp/53 at a pinned VIP

platform/coredns/coredns-custom.yaml has always said its split-horizon is for
PODS and deferred LAN clients to "PiHole split-horizon". PiHole served no DNS:
its Service was ClusterIP with ports 80 and 4180 only. The LAN half of R-DNS-03
that docs/09 and the README's Phase 2 row both claim did not exist, so LAN
clients ran on hand-maintained per-client dnsmasq files - one went stale after
the dev decommission and cost the operator sonarr.home.keithjackson.dev. The
SOHO router that owns 192.168.2.0/24 cannot cover for it either: it strips
RFC1918 answers for public domains as rebind protection and returns NOERROR
with no answer.

EXPOSURE (apps/wave-0/pihole-dns.yaml, hand-written, placed into wave 0 by
render.py's EXTRA_UNITS - the schema has no field for a LoadBalancer Service, a
pinned lbipam VIP, a sharing key, source ranges or UDP, the same reason
apps/vms/unifi and platform/crafty hand-write theirs):
  - two Services, udp/53 and tcp/53, sharing one pinned VIP
    ${PIHOLE_DNS_VIP} = 192.168.2.23 on prod, the next free address in the
    .20-.30 pool (pool status IPsUsed 3 of 11; .20 Gateway, .21 unifi, .22
    crafty; arping from a LAN host got no reply).
  - no external-dns hostname annotation: nothing public is created, and
    platform/externaldns/ is untouched.

ANSWERS (catalog/pihole.yaml env - declarative, no reconciler): PiHole v6 takes
every FTL setting as an FTLCONF_ environment variable and treats it as
env-forced, applied ahead of pihole.toml on every cold start and read-only in
the UI. That is a real declarative entry point, which the Keycloak and CNPG
CronJob reconcilers exist precisely because their state lacks, so a reconciler
here would be ceremony. misc.dnsmasq_lines carries a wildcard
address=/<zone>/<GATEWAY_VIP> plus one longer-domain override per L4 service
(unifi, crafty-mc, pihole-dns); dnsmasq resolves overlaps by longest matching
domain, so precedence is structural and a newly onboarded Gateway-fronted
service needs no DNS change. dns.upstreams is declared too - the live pod
carried hand-set upstreams that no manifest knew about and that every restart
discarded.

externalTrafficPolicy Cluster, NOT Local, and loadBalancerSourceRanges for the
LAN restriction. Measured on prod, Cilium 1.20.1: the L2 announcer does not
filter lease candidates by which nodes hold a backend - the two Services landed
on k3s-prod-3 and k3s-prod-2 while the pod ran on k3s-prod-1 - and it keeps
renewing after the pod moves away, so with Local a reschedule leaves LAN DNS
dead indefinitely. Cluster serves the VIP from any node; the LAN restriction
moves to loadBalancerSourceRanges, which Cilium enforces in eBPF on the VIP
before load-balancing (verified by narrowing the range to exclude the test
client and back). The cost is SNAT: forwarded queries reach PiHole from the
ingress node, so PiHole's per-client rate limit is disabled in the catalog or
the whole LAN would count as one client against its 1000-per-60s default.

Proven from a LAN host (192.168.2.132) against 192.168.2.23 with the pod and
both leases on three DIFFERENT nodes: sonarr/grafana/nextcloud/keycloak/apex
-> 192.168.2.20, unifi -> .21, crafty-mc -> .22, pihole-dns -> .23, recursion
(cloudflare.com, github.com, debian.org) intact over both udp and tcp, AAAA
NODATA, NXDOMAIN outside the zone, and still answering after a forced
prod-1 -> prod-2 reschedule.

Co-Authored-By: Claude Opus 5 <[email protected]>

catalog/pihole.yaml

@@ -13,6 +13,93 @@ storage:
     size: 2Gi
     class: longhorn           # replicated config state; DR-critical (docs/04 line 118; R-STATE-02/03)
 dependencies: []              # default-deny: reaches only DNS; it PROVIDES DNS (docs/03; R-NET-01/02)
+# ------------------------------------------------------------------------------------------------
+# LAN SPLIT-HORIZON DNS — the half of R-DNS-03 that platform/coredns/coredns-custom.yaml defers to.
+# ------------------------------------------------------------------------------------------------
+# coredns-custom answers the ${BASE_DOMAIN} zone for PODS ONLY and says so in its own header ("LAN
+# clients keep their own answers (PiHole split-horizon)"). Until now PiHole served no DNS at all —
+# its Service was ClusterIP :80/:4180, no port 53, no LoadBalancer — so the LAN half did not exist
+# and LAN clients depended on hand-maintained per-client dnsmasq files. One went stale after the dev
+# decommission and cost the operator sonarr.${BASE_DOMAIN}. Upstream cannot cover for it either: the
+# SOHO router that owns this LAN strips RFC1918 answers for public domains as rebind protection and
+# returns NOERROR / ANSWER 0. apps/wave-0/pihole-dns.yaml exposes udp/53 + tcp/53 on
+# ${PIHOLE_DNS_VIP}; these env vars are what make the ANSWERS declarative.
+#
+# WHY env AND NOT A RECONCILER: the repo's level-triggered CronJob reconcilers
+# (platform/keycloak/client-secret-reconciler.yaml, the CNPG grant reconciler in
+# apps/wave-0/nextcloud-db.yaml) exist because their state has NO declarative entry point — a
+# Keycloak client secret lives in Keycloak's own database and a Postgres GRANT lives in the
+# catalog, and nothing in a manifest can express either. PiHole v6 is not that case. Every FTL
+# setting has an `FTLCONF_<section>_<key>` environment variable, and a value supplied that way is
+# ENV-FORCED: FTL logs it as "forced through environment", applies it on every start ahead of
+# /etc/pihole/pihole.toml, and marks it read-only in the admin UI so a human cannot drift it. That
+# is strictly better than a reconciler — it is enforced at t=0 on a cold start rather than at the
+# next cron tick, it cannot be defeated by the UI, and it carries no extra RBAC, image or Job. A
+# CronJob here would be ceremony around a knob the app already exposes. (Verified on the live prod
+# image, PiHole Core v6.4.3 / FTL v6.7, 2026-09-14.)
+#
+# THE PVC IS NOT THE MECHANISM AND MUST NOT BE. The `config` volume below mounts at /data/config;
+# PiHole's actual state directory is /etc/pihole, which is EPHEMERAL in this Deployment. Anything
+# configured through the UI is lost on the next reschedule — which is exactly what happened to the
+# upstream servers: the live pod's pihole.toml carried a hand-set `upstreams` marked "### CHANGED"
+# that no manifest declared, so a restart would have left PiHole with upstreams = [] and no
+# recursion at all. Declaring upstreams here closes that too: PiHole must stay a usable GENERAL
+# resolver, not only authoritative for this zone, or pointing LAN clients at it breaks the internet.
+env:
+  # Default is LOCAL, which answers only clients on the same subnet as the listening interface. The
+  # pod's interface is on the CLUSTER pod CIDR, so every LAN client would be refused. ALL is
+  # required for a LoadBalancer-fronted resolver; what keeps PiHole from being an OPEN resolver is
+  # the exposure, not this setting — `loadBalancerSourceRanges: [${LAN_CIDR}]` on the DNS Services,
+  # enforced by Cilium in the datapath before load-balancing, plus a CiliumNetworkPolicy that admits
+  # nothing but udp/53 and tcp/53. See apps/wave-0/pihole-dns.yaml.
+  - name: FTLCONF_dns_listeningMode
+    value: "ALL"
+  # Recursion for everything that is NOT this zone. Public resolvers on purpose, NOT the SOHO
+  # router at the LAN gateway: that router is the box whose rebind protection strips RFC1918
+  # answers, and forwarding to a device that may forward back here invites a loop.
+  - name: FTLCONF_dns_upstreams
+    value: "8.8.8.8;8.8.4.4"
+  # Per-client query rate limit OFF (default: 1000 queries per 60s, then REFUSED). It has to be off
+  # because of how the DNS Services are exposed: apps/wave-0/pihole-dns.yaml uses
+  # externalTrafficPolicy Cluster — it must, or LAN resolution breaks whenever Cilium's L2
+  # announcement lease and the pihole pod land on different nodes, which is most of the time — and
+  # Cilium runs in SNAT mode here, so a query forwarded between nodes reaches PiHole carrying the
+  # INGRESS NODE's address instead of the client's. Every LAN device therefore counts against ONE
+  # apparent client's budget, and a normal evening of browsing from a handful of machines would trip
+  # a limit meant to catch one misbehaving host. Leaving it at the default turns the whole LAN's DNS
+  # off for 60 seconds at a time, intermittently, which is the worst possible failure shape. The
+  # limit becomes meaningful again — and should be restored — if Cilium is ever switched to
+  # `loadBalancer.mode: dsr`, which preserves the client address.
+  - name: FTLCONF_dns_rateLimit_count
+    value: "0"
+  # THE SPLIT-HORIZON ANSWERS. A dnsmasq `address=/<domain>/<ip>` entry answers that domain AND
+  # every subdomain of it, and dnsmasq resolves overlapping entries by LONGEST MATCHING DOMAIN —
+  # so the first line is a wildcard for the whole zone and each later line is a specific override.
+  # PRECEDENCE IS THEREFORE STRUCTURAL, not order-dependent: `unifi.${BASE_DOMAIN}` matches both
+  # line 1 and line 2, line 2 is the longer domain, line 2 wins. Rewriting these in any order
+  # changes nothing.
+  #
+  # A NEWLY ONBOARDED SERVICE NEEDS NO CHANGE HERE. Every catalog ingressRoute host is
+  # `<label>.${BASE_DOMAIN}` served by the shared Gateway, so the wildcard already answers it with
+  # ${GATEWAY_VIP} — the same guarantee, and the same reasoning, as the `template IN A` block in
+  # platform/coredns/coredns-custom.yaml. Add a line here ONLY for a service that does not live
+  # behind the Gateway: an L4 LoadBalancer on its own pinned VIP. Those are enumerated from the
+  # repo, not from memory — grep `external-dns.alpha.kubernetes.io/hostname` on a Service, which
+  # is the annotation that means "this Service publishes its own hostname at its own address":
+  # apps/vms/unifi/50-service-l4.yaml (unifi -> ${UNIFI_L4_VIP}) and
+  # platform/crafty/service-l4.yaml (crafty-mc -> ${CRAFTY_L4_VIP}). Those two, plus PiHole's own
+  # resolver address, are the complete set of exceptions today.
+  #
+  # AAAA needs nothing: dnsmasq answers a AAAA query for an `address=`d name with NODATA
+  # (NOERROR, no answer), so IPv6-capable clients fall back to the A record instead of getting
+  # NXDOMAIN — the same behaviour coredns-custom hand-writes a `template IN AAAA` block for.
+  #
+  # Array-valued FTLCONF variables are SEMICOLON-separated. A JSON-looking list is accepted and
+  # then silently wrong: FTL stores `["a","b"]` as ONE array element containing those literal
+  # characters, writes that single bogus line into /etc/pihole/dnsmasq.conf and reports "0 invalid"
+  # while resolution for the zone does not work. Confirmed both ways against the live image.
+  - name: FTLCONF_misc_dnsmasq_lines
+    value: "address=/${BASE_DOMAIN}/${GATEWAY_VIP};address=/unifi.${BASE_DOMAIN}/${UNIFI_L4_VIP};address=/crafty-mc.${BASE_DOMAIN}/${CRAFTY_L4_VIP};address=/pihole-dns.${BASE_DOMAIN}/${PIHOLE_DNS_VIP}"
 ingressRoutes:
   - host: pihole.${BASE_DOMAIN}
     port: 80                  # admin web UI, protected at the Gateway by forward-auth (docs/09)

catalog/render.py

@@ -1679,6 +1679,25 @@ EXTRA_UNITS: dict = {
             "gitea-actions-runner-secret.sops.yaml",
         ],
     },
+    # PiHole's DNS exposure: the udp/53 + tcp/53 LoadBalancer Services on a pinned VIP, plus the
+    # narrow LAN ingress CiliumNetworkPolicy that admits them (apps/wave-0/pihole-dns.yaml).
+    # `above: False` co-locates it in pihole's OWN wave: these are the pihole pod's own Services and
+    # its own policy, applied in the same wave as the Deployment they select, exactly as the
+    # rendered Service and CNPs in pihole.yaml are. It is NOT a runtime prerequisite of anything, so
+    # there is nothing for a higher wave to gate on.
+    #
+    # It is a non-catalog unit because the ServiceDefinition schema cannot express a LoadBalancer
+    # Service, a pinned lbipam VIP, a sharing key or UDP exposure at all (additionalProperties is
+    # false, and `ingressRoutes` only renders HTTPRoutes on the L7 Gateway) — the same reason
+    # apps/vms/unifi/50-service-l4.yaml and platform/crafty/service-l4.yaml are hand-written. The
+    # split-horizon ANSWERS are in the catalog, as FTLCONF env on catalog/pihole.yaml.
+    "pihole-dns": {
+        "anchor": "pihole",
+        "above": False,
+        "files": [
+            "pihole-dns.yaml",
+        ],
+    },
 }