# fancy-dns

A recursive DNS server with blocklists, per-client ACLs, a query log, an
embedded admin console and optional clustering over Valkey/Redis.

* **What it is** — a single Go binary that answers DNS over UDP, TCP,
  DNS-over-TLS (RFC 7858) and DNS-over-HTTPS (RFC 8484), resolves everything
  else from a pool of upstream recursors, filters it through blocklists and
  client ACLs, caches the answers, logs the queries, and serves an admin REST
  API plus a React console from the same process.

## Features

Each line points at the package that implements it.

| Feature | Where |
|---|---|
| UDP, TCP, DoT and DoH listeners, all funnelling into one handler | `internal/server` |
| DoH with the RFC 8484 `GET ?dns=` and `POST application/dns-message` profiles over h2, with an h2c fallback; `/.well-known/dns-query` alias; `/healthz` on the same listener | `internal/server/server.go` |
| DoT with optional mTLS (`client_ca`) and configurable `min_version` | `internal/server/server.go` |
| One query pipeline: `rate limit → ACL → local zone → blocklist → cache → upstream` | `internal/engine` |
| Sharded LRU answer cache over packed wire bytes, TTL clamping, serve-stale, prefetch, bbolt snapshot for warm restarts | `internal/cache` |
| Upstream pool with `parallel` / `random` / `failover` policies, weighted selection, per-upstream circuit breakers, health probes, bootstrap IPs for TLS upstreams | `internal/resolver` |
| Blocklists from hosts, Adblock Plus, plain and RPZ sources, compiled into one immutable set that is swapped atomically | `internal/blocklist` |
| Authoritative local data and RPZ policy zones from RFC 1035 master files | `internal/zonefile`, `internal/localzone` |
| Per-client ACL groups matched on CIDR, PTR suffix or reverse-name tag, with per-group domain policy, rate limit, concurrency cap, cache and blocklist toggles | `internal/acl` |
| Query log in a bbolt ring plus an in-memory live ring, sampling, per-domain counters and an SSE stream | `internal/qlog` |
| Prometheus metrics (`fancydns_*`) | `internal/metrics` |
| Admin REST API with API-key / basic / no auth, read-only keys, CORS, per-IP rate limiting and login lockout | `internal/api` |
| Admin console embedded in the binary with `go:embed` | `internal/web`, `web/` |
| Hot reload of the config file (SIGHUP, API, or a cluster peer) with every component swapped atomically | `internal/config`, `internal/app` |
| Cluster coordination over Valkey/Redis: pub/sub events, heartbeats, blocklist-digest divergence detection and a single list-fetch leader lease | `internal/cluster` |
| YAML config with `${VAR}` / `${VAR:-default}` expansion, hot-reloadable atomic store, aggregated validation errors | `internal/config` |

## Quick start

Requirements: Go 1.27 (the `go` directive in `go.mod`), Node 22 for the console
build, and a privileged port (53/443/853) or `CAP_NET_BIND_SERVICE` for the
default listener set.

```sh
git clone <this repository> fancy-dns && cd fancy-dns
make build            # builds the console into internal/web/dist, then dist/fancy-dns
```

`make build` depends on `make web`, which runs `npm ci` (if `web/node_modules`
is missing) and `npm run build` — the Vite build writes to
`internal/web/dist`, which is what `//go:embed all:dist` in
`internal/web/web.go` reads. On a fresh clone that has to happen before the
first `go build` of a console-serving binary.

A minimal `config.yaml`. It listens on unprivileged ports so it can be run
without privileges, and it uses a local plain list so the first start needs no
network:

```yaml
server:
  max_concurrent: 512

dns:
  udp: ["127.0.0.1:5353"]
  tcp: ["127.0.0.1:5353"]
  max_udp_size: 1232

upstream:
  policy: parallel
  servers:
    - addr: 9.9.9.9:53
      proto: udp

cache:
  enabled: true
  size: 10000
  persist:
    enabled: false

blocklist:
  enabled: true
  default_action: nxdomain
  lists:
    - name: local
      format: plain
      path: lists/blocked.txt
      enabled: true          # lists are OFF unless you say enabled: true
      refresh: 0s            # 0 disables the scheduled refresh

qlog:
  enabled: true
  path: data/queries.db

api:
  enabled: true
  listen: ["127.0.0.1:8080"]
  base_path: /api
  ui: true
  auth:
    mode: apikey
    api_keys: ["CHANGE-ME-long-random-string"]
    trust_loopback: true
```

```sh
printf '# one domain per line\nads.example.com\ntracker.example.net\n' > lists/blocked.txt

./dist/fancy-dns -config config.yaml -check     # validate and exit
./dist/fancy-dns -config config.yaml            # run (SIGHUP reloads, SIGINT/SIGTERM stops)

dig @127.0.0.1 -p 5353 example.com A            # NOERROR, resolved upstream
dig @127.0.0.1 -p 5353 ads.example.com A        # NXDOMAIN + synthetic SOA
dig @127.0.0.1 -p 5353 sub.ads.example.com A    # NXDOMAIN (subdomains are covered too)

curl -s http://127.0.0.1:8080/api/healthz        # unauthenticated probe
curl -s -H 'X-API-Key: CHANGE-ME-long-random-string' http://127.0.0.1:8080/api/whoami
```

The console is at <http://127.0.0.1:8080/> and the metrics at
<http://127.0.0.1:8080/api/metrics>.

### Command line

| Flag | Default | Meaning |
|---|---|---|
| `-config PATH` | `$FANCYDNS_CONFIG`, else `/etc/fancy-dns/config.yaml` | config file |
| `-version` | off | print the version and exit |
| `-check` | off | validate the config and exit |
| `-log-level LEVEL` | `$FANCYDNS_LOG_LEVEL` | override `log.level` (`debug`, `info`, `warn`, `error`) |
| `-log-format FORMAT` | `$FANCYDNS_LOG_FORMAT` | override `log.format` (`text`, `json`) |
| `-admin-addr ADDR` | `$FANCYDNS_ADMIN_ADDR` | override `api.listen` without touching the config file |

Signals: `SIGHUP` re-reads the config file and hot-swaps every component; a
failed reload is logged and the running configuration keeps serving. `SIGINT`
and `SIGTERM` start a graceful shutdown with a 15 s drain
(`cmd/fancy-dns/main.go`).

Environment expansion: before parsing, `config.Load` expands `${VAR}`,
`${VAR:-default}` and `${VAR-default}` outside YAML comments. An unset variable
with no default is a **startup error** — that is what makes a missing Kubernetes
Secret a crash loop instead of an unauthenticated API.

## Configuration reference

The document is unmarshalled on top of `config.Default()`, so every key is
optional. Durations accept Go duration strings (`"30s"`, `"1h30m"`) or a bare
number, which is seconds. Relative paths resolve against the directory of the
config file (`Config.AbsPath`). Validation is aggregated: `-check` and
`POST /api/settings/validate` report every problem at once.

Keys marked **unused** are parsed and validated but not read by any code path
today (see [Known inconsistencies](#known-inconsistencies)).

### server

| Key | Type | Default | What it does |
|---|---|---|---|
| `version` | int | `0` | bumped by the admin API on every write; echoed in `/api/settings` and `/api/status` |
| `server.max_concurrent` | int | `1024` | in-flight upstream resolutions; excess queries get SERVFAIL instead of queueing |
| `server.max_concurrent_per_client` | int | `0` (off) | **unused** — use `acl.groups[].max_concurrent` |
| `server.timeouts.udp` | duration | `2s` | not enforced as named: the UDP loop uses a fixed 500 ms read tick and a 2 s write deadline |
| `server.timeouts.tcp` | duration | `4s` | not enforced as named; the TCP/DoT idle timeout is `timeouts.tls` |
| `server.timeouts.tls` | duration | `4s` | DoT/DoH connection idle timeout |
| `server.timeouts.query` | duration | `5s` | **unused** |
| `server.timeouts.upstream` | duration | `2s` | bounds one upstream exchange (including the RFC 1035 retry over TCP) |
| `server.timeouts.list_fetch` | duration | `60s` | seeds `blocklist.lists[].timeout`; **unused** at fetch time (the list HTTP client uses a fixed 120 s) |
| `server.working_dir` | string | config file's directory | base for relative paths; shown in the UI |

### dns

| Key | Type | Default | What it does |
|---|---|---|---|
| `dns.udp` | list of `host:port` | `["0.0.0.0:53", "[::]:53"]` | plain DNS over UDP |
| `dns.tcp` | list of `host:port` | `["0.0.0.0:53", "[::]:53"]` | plain DNS over TCP (length-prefixed, pipelining allowed) |
| `dns.max_udp_size` | int (512–4096) | `1232` | advertised EDNS0 buffer size for our own answers and upstream queries |
| `dns.serve_stale` | duration | `0s` | **unused** — serve-stale is configured per cache (`cache.serve_stale`) |
| `dns.recursion_desired` | bool | `true` | **unused** — RD is always set on outbound queries |
| `dns.hide_identity` | bool | `false` | drop the `fancy-dns` EDNS0 NSID and the `Server: fancy-dns/<version>` header on DoH |
| `dns.dot.enabled` | bool | `false` | enable the DoT listener |
| `dns.dot.listen` | list of `host:port` | `["0.0.0.0:853"]` | DoT bind addresses |
| `dns.dot.cert_file` / `key_file` | path | — | required when `enabled`; both empty means the listener starts but serves plaintext, one empty is a start error |
| `dns.dot.client_ca` | path | — | enables mTLS (`RequireAndVerifyClientCert`) |
| `dns.dot.min_version` | `"1.2"` \| `"1.3"` \| `"1.0"` | `"1.2"` | anything else means TLS 1.2 |
| `dns.dot.upstream` | bool | `false` | **unused** |
| `dns.doh.enabled` | bool | `false` | enable the DoH listener |
| `dns.doh.listen` | list of `host:port` | `["0.0.0.0:443"]` | DoH bind addresses |
| `dns.doh.cert_file` / `key_file` | path | — | without both, the listener logs "running without TLS" and serves h2c |
| `dns.doh.base_path` | path | `/dns-query` | RFC 8484 endpoint; `/.well-known/dns-query` is also served when it differs |
| `dns.doh.allow_post` | bool | `true` | enable the `POST application/dns-message` profile |
| `dns.doh.min_version` | string | `"1.2"` | as `dns.dot.min_version` |
| `dns.doh.transport.mode` | `"auto"` | `"auto"` | **unused** — the listener is always h2 with an h2c fallback; there is no HTTP/3 |
| `dns.doh.transport.alt_svc` | string | — | **unused** |
| `dns.edns0.client_subnet` | bool | `true` | **unused** — ECS is forwarded whenever `preserve` is on |
| `dns.edns0.ipv4_bits` / `ipv6_bits` | int | `24` / `56` | **unused** — the client's ECS option is forwarded verbatim |
| `dns.edns0.cookie_support` | bool | `false` | **unused** — cookies are deliberately not forwarded |
| `dns.edns0.preserve` | bool | `true` | copy the client's ECS and padding into the upstream query |

### upstream

| Key | Type | Default | What it does |
|---|---|---|---|
| `upstream.policy` | `parallel` \| `random` \| `failover` | `parallel` | `parallel` races every chosen upstream and takes the first non-SERVFAIL; `random` shuffles and tries up to `max_attempts` in order; `failover` walks the list in order |
| `upstream.servers` | list | Quad9 ×2 (UDP + DoT), Cloudflare ×2 | the pool; must not be empty |
| `upstream.servers[].addr` | `host:port` | — | required; a bare host gets `:53`, or `:853` for `proto: tls` |
| `upstream.servers[].proto` | `udp` \| `tcp` \| `tls` | `udp` | `tls` is DoT with SNI from `server_name` |
| `upstream.servers[].server_name` | string | host part of `addr` | SNI / TLS verification name for `proto: tls` |
| `upstream.servers[].insecure_skip_verify` | bool | `false` | disables upstream certificate validation |
| `upstream.servers[].health_name` | string | — | **unused**; health probes always ask the dialled address for `. NS` |
| `upstream.servers[].weight` | int | `1` | biases the `random` shuffle |
| `upstream.servers[].max_fails` | int | `0` (use global) | per-upstream breaker threshold |
| `upstream.servers[].comment` | string | — | free text shown in the UI |
| `upstream.max_attempts` | int | `3` | how many upstreams one query may try |
| `upstream.healthcheck_interval` | duration | `30s` | active probe interval (`0` disables it) |
| `upstream.breaker_threshold` | int | `5` | consecutive failures that open the breaker |
| `upstream.breaker_cooldown` | duration | `30s` | how long the breaker stays open; a success closes it early |
| `upstream.bootstraps` | list | none | `name` → `addresses`, used when `addr`'s host is a name; the first address is dialled and the name stays for SNI |
| `upstream.bootstraps[].refresh` | duration | — | **unused** |

### cache

| Key | Type | Default | What it does |
|---|---|---|---|
| `cache.enabled` | bool | `true` | master switch |
| `cache.size` | int (entries) | `200000` | LRU entry budget |
| `cache.shards` | int | `32` | rounded **up** to a power of two |
| `cache.min_ttl` / `cache.max_ttl` | duration | `0s` / `1h` | clamp for TTLs taken from upstream answers |
| `cache.serve_stale` | duration | `30m` | how long an expired entry stays answerable (served with TTL 1) |
| `cache.prefetch` | bool | `true` | re-resolve stale entries in the background |
| `cache.negative_ttl` | duration | `30m` | bounds cached NXDOMAIN / NODATA |
| `cache.prewarm` | list of `"name/TYPE"` | empty | **unused** (`App.prewarm` exists but is never called) |
| `cache.persist.enabled` | bool | `true` | write a bbolt snapshot |
| `cache.persist.path` | path | `data/cache.db` | snapshot file |
| `cache.persist.interval` | duration | `30s` | snapshot cadence (also written on shutdown) |
| `cache.persist.max_entries` | int | `500000` | cap on the snapshot |
| `cache.persist.load_on_start` | bool | `true` | restore the snapshot at boot; entries past `ExpiresAt` are dropped and the rest get the TTL they have left |

Snapshot record format (`internal/cache/store.go`): `byte 0` format version,
`byte 1` flags (`neg`, `truncated`), then uvarints for `ExpiresAt`,
`StaleUntil` and `CreatedAt` (Unix nanoseconds, 0 = zero time), `TTL` seconds,
length-prefixed `Origin` and `Upstream`, the packed wire answer, and a
little-endian CRC-32C trailer. One damaged record costs one entry, not the
file.

### blocklist

| Key | Type | Default | What it does |
|---|---|---|---|
| `blocklist.enabled` | bool | `true` | when on, at least one of `lists`, `local_zones`, `block_entries`, `allow_entries` must be set or `Validate` fails |
| `blocklist.default_action` | `nxdomain` \| `zero` \| `redirect` \| `drop` \| `refused` | `nxdomain` | the synthesised answer for a blocked name |
| `blocklist.response_ip` / `response_ipv6` | IP | `0.0.0.0` / `::` | used by `zero`; the family is chosen from the question |
| `blocklist.response_ttl` | duration | `60s` | TTL of synthesised answers |
| `blocklist.redirect_name` | name | — | required when `default_action: redirect` |
| `blocklist.local_zones` | list of globs | empty | RPZ policy zones and/or local authoritative data, read from master files |
| `blocklist.block_entries` / `allow_entries` | list of lines | empty | inline rules, compiled as `inline:block` / `inline:allow` and applied before every list |
| `blocklist.parallelism` | int | `4` | **unused** — compilation is single-threaded |
| `blocklist.lists[].name` | string | — | required, unique |
| `blocklist.lists[].format` | `auto` \| `hosts` \| `adblock` \| `plain` \| `rpz` | `auto` | see [Blocklists](#blocklists) |
| `blocklist.lists[].url` | http(s):// or file:// | — | one of `url` or `path` is required; `url` wins and its result is written to `path` so restarts work offline |
| `blocklist.lists[].path` | path | — | on-disk copy, resolved against the config directory |
| `blocklist.lists[].mirror` | list of URLs | empty | tried in order when the primary URL fails |
| `blocklist.lists[].enabled` | bool | **`false`** | a list is skipped entirely unless this is `true` |
| `blocklist.lists[].refresh` | duration | `24h` | the scheduler ticks every 5 minutes, so a source is refreshed within 5 minutes of its interval; `0` disables scheduled refresh (manual `/api/blocklists/refresh` only) |
| `blocklist.lists[].timeout` | duration | `server.timeouts.list_fetch` | **unused** at fetch time |
| `blocklist.lists[].max_bytes` | int | `536870912` (512 MiB) | refuses a list larger than this |
| `blocklist.lists[].etag` / `last_modified` | string | — | sent as `If-None-Match` / `If-Modified-Since`; a 304 keeps the previous content |
| `blocklist.lists[].categories` | list of strings | empty | tags copied onto every rule from this source; they feed the UI breakdown |
| `blocklist.lists[].insecure_skip_tls_verify` | bool | `false` | for a self-hosted mirror with a private CA; also stops the download being persisted |
| `blocklist.lists[].comment` | string | — | free text |

### acl

| Key | Type | Default | What it does |
|---|---|---|---|
| `acl.default_policy` | `allow` \| `deny` \| `block_only` | `allow` | applied when no group matches |
| `acl.default_rate_limit` | int (queries/s per client) | `0` (unlimited) | fixed-window cap |
| `acl.groups` | list | empty | evaluated top to bottom, first match wins |
| `acl.groups[].name` / `comment` | string | — | `name` required and unique |
| `acl.groups[].match.cidrs` | list of CIDR | empty | matched against the client address (v4 or v6) |
| `acl.groups[].match.ptr_suffixes` | list | empty | matched against reverse-DNS names of the client, on a label boundary; a missing trailing dot is added |
| `acl.groups[].match.tags` | list | empty | labels derived from the reverse name (e.g. `laptop` for `laptop.lan.internal.`) |
| `acl.groups[].match.any` | bool | `false` | catch-all; must be the last group |
| `acl.groups[].policy` | `allow` \| `deny` \| `block_only` | `allow` | `deny` answers REFUSED and wins over the local zone |
| `acl.groups[].allow_domains` / `deny_domains` | list | empty | per-group name policy with the blocklist wildcards; `deny_domains` is checked first |
| `acl.groups[].skip_blocklist` | bool | `false` | the group opts out of blocklist filtering |
| `acl.groups[].skip_cache` | bool | `false` | the group only gets fresh lookups |
| `acl.groups[].rate_limit` | int | inherit | queries/second for this group |
| `acl.groups[].max_concurrent` | int | `0` (off) | in-flight cap for this client |
| `acl.groups[].log_queries` | bool | `false` | log every query from this group regardless of `qlog.sample_rate` |
| `acl.groups[].upstreams` | list of addrs | empty | restrict this group to named upstreams; a list that matches nothing falls back to the whole pool |

### qlog

| Key | Type | Default | What it does |
|---|---|---|---|
| `qlog.enabled` | bool | `true` | when off the bbolt file is not opened (the live ring and counters stay) |
| `qlog.path` | path | `data/queries.db` | bbolt ring file |
| `qlog.max_entries` | int | `200000` | ring bound; the oldest entries are dropped |
| `qlog.flush_interval` | duration | `1s` | batches writes onto a background goroutine |
| `qlog.sample_rate` | 0–1 | `1.0` | sampling for ordinary queries; blocked/error/cached logging is governed by the flags below |
| `qlog.log_blocked` | bool | `true` | always log blocks |
| `qlog.log_cached` | bool | `true` | log cache hits (set `false` on a busy instance) |
| `qlog.log_errors` | bool | `true` | always log SERVFAIL and friends |
| `qlog.log_client_names` | bool | `false` | **unused** |
| `qlog.live_buffer` | int | `2000` | in-memory ring that feeds the UI and the SSE stream |
| `qlog.top_domains` | int | `5000` | number of per-domain counters kept |
| `qlog.top_ttl` | duration | `5m` | how long those counters are aggregated |

### api

| Key | Type | Default | What it does |
|---|---|---|---|
| `api.enabled` | bool | `true` | master switch for the admin listener |
| `api.listen` | list of `host:port` | `["127.0.0.1:8080"]` | plaintext admin listener (also serves the console) |
| `api.tls_listen` | list of `host:port` | empty | extra listeners with TLS |
| `api.cert_file` / `key_file` | path | — | required for `tls_listen`; h2 + http/1.1, TLS 1.2 minimum |
| `api.base_path` | path | `/api` | prefix for every route; the console is served on the rest |
| `api.ui` | bool | `true` | serve the embedded console |
| `api.allow_config_write` | bool | `true` | lets `PUT /api/settings` rewrite the config file |
| `api.allow_blocklist_write` | bool | `true` | **unused** |
| `api.trusted_proxies` | list of CIDR | empty | the only peers whose `X-Forwarded-For` / `X-Real-IP` is believed |
| `api.cors_origins` | list | empty | `"*"` is allowed but discouraged; the origin is echoed per request so credentials keep working |
| `api.auth.mode` | `none` \| `apikey` \| `basic` | `apikey` | see [Admin API](#admin-api) |
| `api.auth.api_keys` | list | empty | full-access keys (`X-API-Key` header, or basic auth with any user) |
| `api.auth.read_only_api_keys` | list | empty | GET-only keys; mutations answer 403 |
| `api.auth.username` / `password` | string | — | for `mode: basic`; the password may be plaintext or a bcrypt hash (it is hashed either way and compared in constant time) |
| `api.auth.session_ttl` | duration | `12h` | lifetime of a `POST /api/auth/login` bearer token |
| `api.auth.trust_loopback` | bool | `true` | requests from `127.0.0.0/8` and `::1` authenticate as a local principal without a key |
| `api.rate_limit.per_minute` | int | `60` | requests per minute per client IP; `0` disables |
| `api.rate_limit.failures` | int | `10` | failed logins per minute per IP before a lockout |
| `api.rate_limit.lockout` | duration | `5m` | lockout length; 429 carries `Retry-After` |

### metrics

| Key | Type | Default | What it does |
|---|---|---|---|
| `metrics.enabled` | bool | `true` | registers the route |
| `metrics.path` | path | `/metrics` | **unused** — the endpoint is always `${api.base_path}/metrics` |
| `metrics.protect` | bool | `false` | require a principal for `/api/metrics` |

Metric names: `fancydns_queries_total`, `fancydns_blocked_total`,
`fancydns_cache_hits_total`, `fancydns_cache_misses_total`,
`fancydns_cache_stale_hits_total`, `fancydns_upstream_errors_total`,
`fancydns_errors_total`, `fancydns_dropped_total`, `fancydns_refused_total`,
`fancydns_upstream_health`, `fancydns_concurrent_queries`,
`fancydns_blocklist_rules`, `fancydns_blocklist_source_bytes`,
`fancydns_acl_groups`, `fancydns_local_records`, `fancydns_up`,
`fancydns_query_duration_seconds`, `fancydns_upstream_duration_seconds`,
`fancydns_blocklist_compile_seconds`.

### log

| Key | Type | Default | What it does |
|---|---|---|---|
| `log.level` | `debug` \| `info` \| `warn` \| `error` | `info` | overridden by `-log-level` |
| `log.format` | `text` \| `json` | `text` | overridden by `-log-format` |
| `log.addr` | path | empty (stderr) | when it starts with `/` the log is appended to that file; any other value is ignored |

### cluster

| Key | Type | Default | What it does |
|---|---|---|---|
| `cluster.enabled` | bool | `false` | when on, `cluster.valkey.addrs` must not be empty |
| `cluster.node_id` | string | hostname | identity in the cluster view, suffixed with a random 4-byte id |
| `cluster.advertise` | string | empty | published in the heartbeat; **nothing dials it** today |
| `cluster.peer_sync` | bool | `false` | **unused** |
| `cluster.peer_ttl` | duration | `15s` | the heartbeat period is half this; the node hash expires after 4× |
| `cluster.valkey.addrs` | list of `host:port` | — | Valkey/Redis endpoints (joined with commas into one client) |
| `cluster.valkey.username` / `password` / `db` | string/int | — | ACL-based auth, DB index |
| `cluster.valkey.prefix` | string | `fancydns` | key prefix: `<prefix>:nodes`, `<prefix>:leader`, `<prefix>:events:<kind>` |
| `cluster.valkey.tls` | bool | `false` | **unused** — no TLS is configured on the client |
| `cluster.valkey.pool_size` | int | `10` | minimum 1 |
| `cluster.valkey.dial_timeout` / `read_timeout` | duration | `2s` | client timeouts; `read_timeout` is also the write timeout |
| `cluster.valkey.leader_ttl` | duration | `30s` | length of the list-refresh lease |

## Zone files and local zones

`internal/zonefile` parses an RFC 1035 master-file subset:

* `$TTL <ttl>` sets the default TTL, `$ORIGIN <name>` changes the origin.
* Parenthesised continuations are folded into one logical line; `;` starts a
  comment outside quoted strings; a leading UTF-8 BOM is stripped.
* A record may omit the owner (it repeats the previous one), the TTL and the
  class, in any order, as long as the type token is recognisable. TTLs accept
  the `s`/`m`/`h`/`d`/`w` unit suffixes or bare seconds.
* `@` means the current origin; a name that ends in a dot is absolute and is
  never origin-relative.
* `$INCLUDE` is **rejected**: `internal/zonefile/zonefile.go` returns
  "`$INCLUDE … is not supported; use blocklist.local_zones or a list source
  instead`". Split the data into more `local_zones` globs instead.
* `zonefile.SerialNext` implements RFC 1982 arithmetic (`+N`, `-N`, absolute),
  but there is no zone transfer, so nothing calls it.

**Zone name from a path.** `localzone.Load` derives each file's origin with
`zonefile.OriginFromPath`, which takes the base name and truncates it at the
first dot: `zones/lan.zone` and `lan.zone` both become the origin `lan.`
(the doc comment on that function says `ads.zone.`, which is wrong — see
[Known inconsistencies](#known-inconsistencies)). An explicit `$ORIGIN` inside
the file wins, because `Parse` starts from that derived origin and the
directive replaces it. Records that fall outside their own zone are dropped
(`localzone.add` returns false).

The practical consequence: a *relative* name is qualified with the file's base
name, not with the zone you had in mind. In `local.example.zone` (origin
`local.`) the record `ns1 A 192.168.1.2` becomes `ns1.local.`, and in a policy
zone `*.doubleclick.net` becomes `*.doubleclick.net.local.` — a rule that blocks
nothing you asked about. Both shipped examples therefore spell every name out in
full, which is the only spelling that does not depend on what the file is
called: `TestExampleLocalZoneIsOriginIndependent` (`internal/zonefile`) and
`TestExampleRPZZoneBlocksWhatItSays` (`internal/blocklist`) fail if they are
"tidied up" back to relative names.

**Policy zone vs ordinary local zone.** Both come from
`blocklist.local_zones` and both are master files; the difference is what the
records mean and where they are matched:

| | RPZ-style policy zone | Ordinary local zone |
|---|---|---|
| Compiled by | `blocklist.parseRPZ` / `parseRPZFiles` | `localzone.Load` |
| Matching | by rule name; `*.name` covers subdomains but **not** the name itself (see [Known inconsistencies](#known-inconsistencies)); the rdata carries the action | by the question: exact `name\|TYPE`, then `*.<name>`, then any type at the name |
| Action from rdata | `CNAME .` → NXDOMAIN, `CNAME rpz-drop.` → drop, `CNAME rpz-passthru.` / `rpz-tcp-only.` → passthrough, other CNAME → CNAME answer, `A`/`AAAA` → that address, `TXT` containing `allow` → allow | none; records are answers, and the zone's SOA is returned for NXDOMAIN/NODATA |
| In the pipeline | after the ACL, before the cache | after the ACL, before the blocklist |
| Delegation | n/a | an `NS` record below the apex marks a delegation and the data below it is not answered |

`deploy/local.example.zone` is a local authoritative zone (SOA, NS, A/AAAA,
one-label and deeper wildcards, SRV, TXT). `deploy/zones/local.rpz.zone.example`
is a policy zone.

## Blocklists

A source is compiled into rules, and every source is merged into one immutable
`Set`; the `Manager` swaps a whole new set in with one atomic store, so a query
sees either the old rules or the new ones. Matching is a few map lookups
against an exact map, a subdomain map and a wildcard map.

Name patterns: `example.com` matches the name itself, `*.example.com` matches
strict subdomains, `**.example.com` matches the apex and everything under it.
Sources are parsed with subdomains on by default, so a bare hosts-file or
plain-list entry becomes `**.name`.

| `format` | Accepts | Example | Notes |
|---|---|---|---|
| `hosts` | `IP name [name…]`, `0 name`, `localhost` lines, `#`/`;` comments | `0.0.0.0 ads.example.com` | `localhost`/`broadcasthost`/`ip6-*` lines are skipped; a line whose first field is not an address falls back to the plain parser, with a notice in the parse stats |
| `adblock` | `\|\|host^` and `\|http://host/…` (blocked), `@@\|\|host^` (allowed), bare hostnames | `\|\|ads.example.com^$third-party` | element-hiding rules (`##`, `#@#`, `#?#`) and regex rules are skipped and reported in `stats.notices`; a URL path rule blocks the whole host |
| `plain` | one name per line, `0.0.0.0 name`, `!allow name` / `!name` / `@@…` allow markers, adblock tails on pasted lines | `ads.example.com` | a single-label name without a dot is rejected |
| `rpz` | an RFC 1035 policy zone | `ads.example.com CNAME .` | parsed by `internal/zonefile`; the zone's own default TTL wins for records with no TTL column |
| `auto` | sniffs the first 200 meaningful lines | — | default; a `$TTL`/`$ORIGIN`/`$INCLUDE` line or a `name TTL IN A …` shape means `rpz`, an address-first line means `hosts`, `\|\|`/`##`/`@@` means `adblock`, otherwise `plain` |

**Categories.** `blocklist.lists[].categories` are copied onto every rule from
that source and surfaced in the console's per-category breakdown. They have no
effect on matching.

**Refresh and replication.** A list is fetched with a conditional GET
(`If-None-Match` / `If-Modified-Since`); a 304 keeps the previous content. The
downloaded copy is written to `path` (atomically) unless
`insecure_skip_tls_verify` is set, and a later start prefers that copy, so a
restart without network still has rules. A source that fails keeps its previous
compiled content and is flagged stale in the UI, so a bad deploy never leaves
the resolver with no blocklists. The scheduler ticks every 5 minutes and
refreshes every source whose interval has elapsed, and the first pass after a
start is staggered per source name.

**Only the Valkey lease holder fetches.** With `cluster.enabled`, the lease
(`${prefix}:leader`, `SET NX` with `valkey.leader_ttl`) is acquired and renewed
by one instance. A `blocklists` event from any peer triggers a refresh **only**
in the lease holder; followers keep serving their compiled copy. Without
clustering, every instance fetches for itself.

## Admin API

Base path `/api` (`api.base_path`). `GET /api/healthz` is unauthenticated — it
is the liveness and readiness probe and deliberately reveals only a coarse
status (503 when `status: down`). `POST /api/auth/login` is unauthenticated by
necessity. `GET /api/whoami` is behind the same authentication as the rest of
the API; with `auth.trust_loopback: true` a request from loopback is authorised
as a local principal, and otherwise it answers 401 (the CI smoke test asserts
exactly that). `GET /api/metrics` is unauthenticated unless `metrics.protect`
is on.

| Method | Path | Write | Purpose |
|---|---|---|---|
| GET | `/api/healthz` | — | status payload (public) |
| GET | `/api/metrics` | — | Prometheus exposition; gated by `metrics.protect` |
| POST | `/api/auth/login` | — | exchange an API key or user/password for a bearer token (public) |
| POST | `/api/auth/logout` | yes | revoke the caller's bearer token |
| GET | `/api/whoami` | — | caller's name, mode, `read_only`, `can_write` |
| GET | `/api/dashboard?range=…` | — | aggregated counters and the rolling series |
| GET | `/api/status` | — | version, uptime, config generation/last error, per-component status, listeners |
| GET | `/api/blocklists` | — | compiled state, per-source metadata, errors |
| POST | `/api/blocklists/refresh` | yes | recompile now; body `{"names":[…]}` or empty for everything |
| POST | `/api/blocklists/toggle` | yes | `{"name":…,"enabled":…}` |
| GET | `/api/domains?q=&action=&list=&page=&per_page=` | — | page the compiled rules |
| GET | `/api/domains/check?name=…` | — | explain how a name would be treated (the fastest "why isn't this blocked" tool) |
| POST | `/api/domains` | yes | add an inline rule |
| DELETE | `/api/domains/{name…}?action=&list=` | yes | remove a rule |
| GET | `/api/clients` | — | ACL groups and the default policy |
| PUT | `/api/clients` | yes | replace the ACL (`{"groups":[…],"default_policy":…}`); validates, writes the file, swaps, broadcasts |
| GET | `/api/upstreams` | — | pool state, health, latency, breaker |
| PUT | `/api/upstreams` | yes | replace policy/servers/bootstraps/attempts/threshold (cooldown is preserved) |
| GET | `/api/logs?q=&action=&client=&rcode=&blocked=&since=&limit=&offset=` | — | page the query log |
| GET | `/api/logs/stream` | — | Server-Sent Events: `ready`, `entry`, `stats` and `: ping` keep-alives |
| POST | `/api/logs/clear` | yes | empty the query log |
| GET | `/api/cache` | — | cache statistics |
| GET | `/api/cache/top?limit=` | — | hottest cached names |
| POST | `/api/cache/flush` | yes | drop the cache (also done after a rule change) |
| GET | `/api/settings` | — | file YAML, effective YAML, defaults YAML, writability |
| PUT | `/api/settings` | yes | validate, write (atomic, mode 0600), bump `version`, swap, broadcast; needs `api.allow_config_write` |
| POST | `/api/settings/validate` | — | validate a document without applying it; returns errors and warnings |
| POST | `/api/settings/reload` | yes | re-read the config file from disk |

**Auth modes.** `apikey` (default): `X-API-Key` with a full or read-only key;
basic auth with the key in the password field is also accepted, and a `bearer`
token from `/api/auth/login` works everywhere. Keys are compared by SHA-256
hash in constant time. `basic`: HTTP basic against `auth.username` /
`auth.password`; a successful login mints a bearer token valid for
`auth.session_ttl`. `none`: no credential is required — the console and every
mutation are open to anyone who can reach the port; the settings validator
emits a warning for exactly this.

JSON request bodies are capped at 4 MiB and unknown fields are rejected, so a
typo is a 400 rather than a silent no-op. A panic in a handler becomes a 500
and is logged.

## Deployment

### Container

```sh
make image                      # docker build --build-arg VERSION=$(git describe) -t fancydns/fancy-dns:<version> .
docker run --rm -p 53:53/udp -p 53:53/tcp -p 8080:8080 \
  -v fancydns-data:/var/lib/fancy-dns \
  -v "$PWD/config.yaml:/etc/fancy-dns/config.yaml:ro" \
  fancydns/fancy-dns:<version> -config /etc/fancy-dns/config.yaml
```

The `Dockerfile` builds the console in a Node stage, then a static
`CGO_ENABLED=0` binary with it embedded, and ships it on
`gcr.io/distroless/static-debian12:nonroot`. It declares `VOLUME
/var/lib/fancy-dns` (cache snapshot, query log, downloaded lists) and copies
`deploy/config.example.yaml` plus `deploy/zones/` to `/etc/fancy-dns/`; there
is no `config.yaml` in the image, so its `CMD` (`-config
/etc/fancy-dns/config.yaml`) requires you to mount one.

### Kubernetes

`deploy/k8s/` is a kustomization: namespace, ConfigMap, ServiceAccount
(`automountServiceAccountToken: false` — the server never talks to the API
server), the API-key Secret, a StatefulSet, three Services, an Ingress and a
PodDisruptionBudget.

```sh
kubectl -n dns create secret generic fancy-dns-apikey \
  --from-literal=api-key="$(openssl rand -hex 32)"        # the API-key step
kubectl kustomize deploy/k8s | kubectl apply -f -
```

Things to know before you apply it:

* **The API key comes from a Secret, not the ConfigMap.** The config contains
  `api_keys: ["${FANCYDNS_API_KEY}"]` and the loader substitutes it from the
  pod's environment. A missing variable is a startup error, so a forgotten
  Secret is a `CrashLoopBackOff`, not an open console. The checked-in Secret
  holds the placeholder `REPLACE-ME`; applying it as-is overwrites a real key,
  and nothing rejects a weak key.
* **A LoadBalancer is required for DNS.** `fancy-dns-dns` is a `LoadBalancer`
  with `externalTrafficPolicy: Local` on 53/UDP, 53/TCP and 853/TCP. The pods
  deliberately do **not** use `hostNetwork`: the server does not set
  `SO_REUSEPORT`, so two host-network pods cannot share the node's `:53` and
  the second would crash-loop on bind. If your provider cannot health-check
  UDP, use DNS-level failover instead of a TCP health check.
* **`NET_BIND_SERVICE`.** The container drops all capabilities and adds only
  `NET_BIND_SERVICE`, which exists solely for the low ports (53/443/853). The
  pod runs as uid 65532, non-root, with a read-only root filesystem. Drop the
  capability and the Service if you move the listeners above 1024.
* **Ingress annotations for SSE.** The live log page needs
  `nginx.ingress.kubernetes.io/proxy-buffering: "off"` plus
  `proxy-read-timeout` / `proxy-send-timeout: "3600"`. With buffering on, nginx
  holds events until the buffer fills and the page looks frozen; with the
  default 60 s read timeout the stream is cut every minute and the console
  reconnects in a loop. `backend-protocol: HTTP` matches the h2c DoH listener.
  The handler also sends `X-Accel-Buffering: no`.
* **Per-pod PVC sizing.** The StatefulSet uses a 4 Gi `ReadWriteOnce`
  template. `cache.size` is an *entry count*, not bytes: a packed answer is
  roughly 300–600 bytes on the wire and nearer 1 kB resident, so 500k entries
  lands around 500 MB, and `qlog.max_entries` is the other consumer. The PVC
  cannot be shared between replicas, and being a StatefulSet also means an HPA
  cannot drive the replica count.
* Probes all hit `/api/healthz` on the admin port, which is unauthenticated on
  purpose. `terminationGracePeriodSeconds: 30` gives the 15 s drain room. The
  `reloader.stakater.com/auto` annotation is for reloader-class controllers;
  without one, `kubectl rollout restart` is the manual equivalent.
* The TLS Secret `fancy-dns-tls` ships with empty `tls.crt` / `tls.key`; fill
  it (cert-manager in production) or the DoT/DoH listeners fail to build their
  `tls.Config`.

## Security notes

* **`api.trusted_proxies` and `X-Forwarded-For`.** The client IP is the socket
  peer unless that peer is inside a `trusted_proxies` CIDR; only then is the
  left-most `X-Forwarded-For` entry (or `X-Real-IP`) believed. Put the ingress
  controller's pod CIDR there and nothing else. If you trust a range clients
  can reach directly — or leave the list empty behind a proxy that rewrites
  nothing — a client can send an arbitrary `X-Forwarded-For` and choose its own
  identity: it lands in whichever `acl.groups` CIDR it names, escapes a `deny`
  group, and gets its own rate-limit bucket, so per-group rate limits and
  concurrency caps stop applying to it.
* **`metrics.protect`.** Default `false`, so `/api/metrics` is open to anyone
  who can reach the admin port and publishes client addresses, top domains and
  upstream names. Set it to `true` (as `deploy/config.example.yaml` does) and
  scrape with `X-API-Key`. The settings validator warns when it is off.
* **`api.auth.mode`.** `none` means no credential is checked at all, and the
  API can rewrite your config, your ACL and your upstreams. `Validate` refuses
  `apikey` with an empty `api_keys` *and* `trust_loopback: false`, because that
  combination is `none` in everything but name. `trust_loopback: true` (the
  default) is an implicit bypass for anything on the same host — including other
  containers sharing the pod's network namespace — so set it to `false` in
  Kubernetes.
* **`api.cors_origins: ["*"]`** echoes any origin back with
  `Access-Control-Allow-Credentials: true`. Only do that for a console you are
  willing to expose to arbitrary web pages.
* **TLS material.** `dns.dot.*`, `dns.doh.*` and `api.cert_file` / `key_file`
  are read from disk at start and on reload; the API never writes them. The
  config file is written with mode `0600`, and a config written through the API
  is broadcast to peers verbatim — so keep API keys and Valkey passwords in a
  Secret (via `${VAR}`) rather than in a committed file. A key in a ConfigMap is
  readable by anyone with `get configmaps`.
* **Plain-HTTP DoT/DoH.** Enabling `doh` without `cert_file` / `key_file` serves
  the endpoint in cleartext and the server only logs a warning.
* **Rate limiting is per client IP, fixed window** (`acl.*.rate_limit`,
  `api.rate_limit.per_minute`), so it is a runaway-client guard, not DDoS
  defence, and many clients behind one NAT share a bucket.
* **Upstream TLS.** `insecure_skip_verify` on an upstream disables certificate
  validation for every query sent to it; the validator warns about it.
  `insecure_skip_tls_verify` on a list source disables validation for the
  download *and* stops the copy from being persisted.

## Limitations

* **No DNSSEC validation.** There is no trust anchor, no validator, no
  `dnssec` package. The AD bit, the CD bit, the DO bit and the extended RCODE
  are copied from the upstream answer to the client (`engine.fromUpstream`) so a
  validating stub sees what the upstream claimed, but fancy-dns neither checks
  nor vouches for any of it. `cache.Key` keeps DO in the key because a DO query
  legitimately gets a different answer; CD is deliberately not part of the key.
* **No zone transfer.** AXFR/IXFR are not implemented: the master-file parser
  knows the record types, but nothing serves or accepts a transfer, and
  `zonefile.SerialNext` is unused.
* **No dynamic update.** An UPDATE message passes the engine's shape check
  (`validate` tolerates `OpcodeUpdate`) and is then handled as an ordinary
  query. There is no RFC 2136 handling, no journal and no NOTIFY. A local zone
  only changes when the file changes and the config is reloaded (SIGHUP,
  `POST /api/settings/reload`, or a restart).
* **No HTTP/3** for DoH despite `dns.doh.transport.mode` / `alt_svc`; the
  listener is h2 with an h2c fallback.
* **No certificate automation**: certificates are files on disk, one per
  listener; there is no ACME client and no wildcard handling.
* **Local zones are not a full authoritative server**: no DNSSEC, no transfer,
  and a delegated name is resolved upstream rather than answered with a
  referral.
* **Unknown config keys are silently ignored** (no `yaml` `KnownFields`), so a
  typo such as `block:` instead of `blocklist:` yields a plausible server
  instead of an error. Likewise, a list without `enabled: true` is silently
  skipped.

## Development

```sh
make            # help screen
make build      # console + binary with the console embedded -> dist/fancy-dns
make go-build   # binary without console assets (fast; used by the test loop)
make web        # npm ci (if needed) + npm run build -> internal/web/dist
make web-dev    # Vite dev server, proxying /api to 127.0.0.1:8080
make web-check  # npm ci + tsc -b --noEmit + npm run build
make check      # what CI runs: fmt-check, vet, test
make test       # go test -race -count=1 ./...
make test-short # go test -short -count=1 ./...   (no race detector)
make cover      # coverage.html + a summary line
make bench      # cache and blocklist benchmarks
make fmt / make fmt-check / make vet / make lint
make run        # dist/fancy-dns-noassets -config deploy/config.example.yaml -log-level debug
make check-config CONFIG=path/to/config.yaml   # -check only
make image / make push / make clean / make clean-web
```

**The Go build embeds `internal/web/dist`.** `internal/web/web.go` has
`//go:embed all:dist`, and the Vite config writes there. On a fresh clone the
directory holds only a `.gitkeep`, so `npm ci && npm run build` (i.e. `make
web`) must run before a `go build` that should serve the console; otherwise the
server starts, logs "web console assets missing from this binary", and answers
`/` with a page telling you to run `make web`. CI asserts the bundle exists
after `npm run build`. Note that `vite build` empties `outDir` and deletes
`.gitkeep` — restore it afterwards or the directory disappears from git.

`make test` is what CI runs for Go; the race detector is not optional there
because every hot path uses atomic holders and swap hooks.
`.github/workflows/ci.yml` has four jobs: `go` (gofmt, vet, `go test -race`, a
`-short` run with coverage, and a build without the console), `web` (npm ci,
`tsc -b --noEmit`, build, assert `internal/web/dist/index.html`), `binary`
(build the console, build the binary with it embedded, then a smoke test that
rewrites `deploy/config.example.yaml` to unprivileged ports, asserts
`/api/healthz` answers, that `/` is HTML, that `/api/whoami` is 401 without a
key and 200 with one), and `image` (build and push to ghcr.io on `main`).

## Known inconsistencies

Found while writing this file; each is a to-do, not something fixed here.
`README.md` is the only file this change touches.

1. **`internal/config/config.go:117` — `dns.serve_stale` is dead.** Parsed,
   defaulted and shown in `/api/settings`, but nothing reads it; the serve-stale
   window comes from `cache.serve_stale` (`internal/app/app.go:startCache`).
2. **`internal/config/config.go:121` — `dns.recursion_desired` is dead.** The
   engine always sets `RecursionDesired = true` on outbound queries
   (`internal/engine/engine.go:prepareUpstream`).
3. **`internal/config/config.go:94` — `server.max_concurrent_per_client` is
   dead.** Per-client caps come from `acl.groups[].max_concurrent`, which its
   own comment already points at.
4. **`internal/config/config.go:80-88` — `server.timeouts.query` is dead**;
   only defaulted. In the same struct, `server.timeouts.udp` / `.tcp` are not
   enforced under those names: the UDP loop uses a hard-coded 500 ms read tick
   and 2 s write deadline (`internal/server/server.go:serveUDP`,
   `servePacket`), and the TCP/DoT idle timeout is `timeouts.tls`.
5. **`internal/config/config.go:197` — `upstream.servers[].health_name` is
   dead.** `Pool.HealthCheck` always probes the dialled address for `. NS`
   (`internal/resolver/pool.go`); the field is only set by a test fixture.
6. **`internal/config/config.go:229` — `cache.prewarm` is dead.**
   `App.prewarm` exists (`internal/app/app.go:220`) but nothing calls it, while
   `deploy/config.example.yaml:97` ships `prewarm: []`.
7. **`internal/config/config.go:358` — `qlog.log_client_names` is dead.**
8. **`internal/config/config.go:373` — `cluster.peer_sync` is dead**, and
   **`cluster.advertise`** (`:371`, "the address other instances dial for the
   admin API") is only echoed in heartbeats: no code dials a peer.
9. **`internal/config/config.go:411` — `api.allow_blocklist_write` is dead.**
   Only `allow_config_write` is enforced (`internal/api/handlers.go:
   handleSettingsPut`).
10. **`internal/config/config.go:418` — `metrics.path` is dead.** The route is
    built from `api.base_path` (`internal/api/api.go:routes`:
    `GET <base>metrics`), so `metrics.path: /metrics` in
    `deploy/config.example.yaml:196` and in `deploy/k8s/00-config.yaml` has no
    effect; the endpoint is `/api/metrics`.
11. **`internal/config/config.go` — `dns.doh.transport.alt_svc` (`:157`) and
    `.mode` (`:156`), `dns.dot.upstream` (`:129`), `dns.edns0.cookie_support`
    (`:166`), `dns.edns0.client_subnet` (`:162`), `dns.edns0.ipv4_bits` /
    `ipv6_bits` (`:163-164`) are all dead.** `serveDoH` always speaks h2 with an
    h2c fallback (no HTTP/3, no Alt-Svc), there is no encrypted-upstream DoT
    switch (`upstream.servers[].proto: tls` is the way to get that), and ECS is
    forwarded verbatim whenever `dns.edns0.preserve` is on.
12. **`internal/config/config.go:266` — `blocklist.parallelism` is dead**;
    `RefreshAll` compiles single-threaded.
13. **`internal/config/config.go` (`ListSource.Timeout`) and
    `server.timeouts.list_fetch`** — the fetch timeout is never applied:
    `blocklist.NewManager` hardcodes a 120 s `http.Client` and
    `internal/blocklist/manager.go:fetch` never consults `l.Timeout`.
14. **`internal/config/config.go` (`UpstreamBootstrap.Refresh`)** — bootstrap
    names are resolved once per pool rebuild; `refresh` never triggers a
    re-resolution.
15. **`internal/config/config.go` (`Valkey.TLS`)** — `cluster.valkey.tls` is
    never applied; `internal/cluster/cluster.go:dial` builds a plain
    `redis.Client` with no `TLSConfig`.
16. **`internal/zonefile/zonefile.go:525-526` — the `OriginFromPath` doc
    comment is wrong.** It claims `"rpz/ads.zone"` and `"ads.zone"` both become
    `"ads.zone."`; the code truncates at the first dot, so both become `"ads."`.
    The behaviour is what `localzone.Load` and `blocklist.parseRPZFiles` rely
    on — fix the comment.
17. **`internal/zonefile/zonefile.go:1-8` and `:238-243` — the package comment
    advertises `$INCLUDE`, the parser rejects it** ("`$INCLUDE … is not
    supported; use blocklist.local_zones or a list source instead`"), and
    `Options.MaxIncludeDepth` is never set by any caller. Either implement it or
    correct the comment and drop the field.
18. **`Makefile:113` — `make run` claims it runs
    `deploy/config.example.yaml` "on unprivileged ports", but that file binds
    `0.0.0.0:53` and `[::]:53`** (`deploy/config.example.yaml:23-24`).
    Unprivileged use needs the same `sed` rewrite the CI smoke test does
    (`.github/workflows/ci.yml`, "Smoke test the real binary"), or a port you
    can bind.
19. **`deploy/k8s/10-deployment.yaml` — the comment tells the reader to manage
    zones "through the admin API (`/api/zones`)", which does not exist.** There
    is no zone endpoint in `internal/api/api.go:routes`; local zones are edited
    on disk.
20. **`deploy/k8s/20-service.yaml` — the load-balancer comment says to leave
    the LB health check on the HTTP admin port, but the `fancy-dns-dns`
    LoadBalancer Service publishes only 53/UDP, 53/TCP and 853/TCP.** The admin
    port is on the separate `fancy-dns-web` ClusterIP Service, which the LB
    cannot health-check. Pick a provider with UDP health checks or use DNS-level
    failover.
21. **`deploy/k8s/00-config.yaml` enables `dot` and `doh` against
    `/etc/fancy-dns/tls/tls.crt` while the Secret it mounts ships empty
    `tls.crt` / `tls.key`.** Applying the kustomization unchanged leaves both
    listeners unable to build a `tls.Config`; a comment says so, but an example
    that cannot come up as-is is still a footgun.
22. **`api.rate_limit.per_minute` defaults to `60` in `config.Default()` but
    `deploy/config.example.yaml:189` says `600`**, and
    `deploy/config.example.yaml` sets `qlog.log_cached: false` where the default
    is `true`. Harmless, but the example is not a dump of the defaults and
    readers will assume it is.
23. **`api.auth.mode: apikey` with an emptied `api_keys` list and
    `trust_loopback: true` is indistinguishable from `none`.** `Validate` only
    rejects the combination with `trust_loopback: false`; the unsafe case is
    reported solely as a warning from `POST /api/settings/validate`.
24. **`config.Load` does not use `yaml.Decoder.KnownFields`**, so unknown keys
    are ignored silently. A settled decision (pinning, not changing, the
    behaviour); `TestLoadIgnoresUnknownKeys` in `internal/config` holds it.
25. **`internal/blocklist/parse.go:485-495` — an RPZ record does not cover the
    name it names.** `rpzRule` gives a bare owner name the subdomain form
    (`*.name`), and a subdomain-form rule matches that name's children but not
    the name itself, so `analytics.example.org.` in a policy zone blocks
    `cdn.analytics.example.org.` and leaves `analytics.example.org.` resolving
    normally. RPZ semantics say the record applies to the domain and everything
    under it, so the apex form (`**.name`) is what belongs here — a
    one-character change in `rpzRule` that alters which queries get blocked, so
    it wants a decision rather than a quiet fix. Pinned by
    `TestExampleRPZZoneApexIsNotCovered`. The same gap means an
    `rpz-passthru.` record for a domain does not allowlist the domain itself.
26. **`internal/api/api.go:288-317` — `api.cors_origins: ["*"]` echoes the
    request's `Origin` *and* sets `Access-Control-Allow-Credentials: true`.**
    That is deliberate (a literal `*` is ignored by browsers when credentials
    are involved, so echoing is the only way a wildcard can work with a session
    token), but it does mean a wildcard CORS origin lets any website drive the
    admin API with whatever the browser already has cached for that host —
    relevant to `auth.mode: basic` and to a loopback-trusted console. The
    preflight also answers 204 for *any* origin and any path, and credentials
    are advertised for exact origins too. Pinned by
    `TestCORSWildcardEchoesTheOrigin` and `TestCORSPreflight`; whether a
    wildcard should be refused outright is a decision.