Names beside inside addresses

Reverse lookups (internal/names, POST /names) put a name beside each
inside address in connections, the log, quota usage, the dashboard's
quotas and the statistics' devices and blocked sources, in the web UI
and hc (--no-names to leave them out). Only inside addresses are looked
up: an inside zone's networks, and private ones outside the external
zones'. Names are cached (names.cache, 10m) and never stored;
names.resolver picks the DNS server.

Also: hc stats top devices listed each device twice; the dashboard's
quotas named the rule's ID twice.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/api.md

@@ -82,6 +82,7 @@ Creating answers 201, other changes 200.
 | `GET /counters` | `{"since", "counters": {"r12": {"packets", "bytes"}, ...}}`, by mark ([design.md](design.md#its-own-table-only)); totals since housecarld started |
 | `GET /quotas` | each rule's quota: `rule_id`, `rule`, `quota`, `used` (bytes), `addresses` (`[{"address", "used"}]` for a per-address quota), `last_reset`, `next_reset` |
 | `GET /connections[?q=&limit=]` | tracked connections: `family`, `protocol`, `source`, `source_port`, `destination`, `destination_port` (or `icmp_id`, `icmp_type`, `icmp_code`), `dnat_to`, `dnat_port`, `snat_to`, `state`, `assured`, `timeout` (seconds left), `packets` and `bytes` when the kernel counts them. `q`: all of its words in the addresses, `:port`, protocol, state |
+| `POST /names` | `{"addresses": [...]}` (at most 2000): `{"enabled", "names": {"192.168.1.20": "laptop.example.net"}}`, the names of the inside addresses among them, by reverse lookup ([configuration.md](configuration.md#names)). Addresses without a name, outside ones, and those still being looked up after a second are left out; ask again for those. `log:read` |
 | `POST /connections/close` | `{"connections": [...]}` (as listed) or `{"search": "192.168.1.50"}`: delete their tracking entries (`config:write`, audited); answers `{"closed": N}`. 409 in shadow mode |
 | `POST /trace` | `{"address", "port", "protocol", "seconds"}` (5-600, default 60): start tracing (`config:write`, audited); 409 while one runs |
 | `GET /trace` | the trace running, or the last: `running`, `input`, `started`, `ends`, `error`, `packets`: each with `time`, `in`, `out`, `protocol`, addresses and ports, `tcp_flags`, `icmp_type`, `steps` (`table`, `chain`, `kind` rule or policy, `rule`, `mark`, `label`, `verdict`), `verdict` (accepted, dropped) and `decided_by`; in shadow mode `would_drop`, the step where Housecarl would have dropped it |

docs/cli.md

@@ -32,6 +32,7 @@ command and its flags.
 | `-C, --changeset ID` | `HOUSECARL_CHANGESET` (checked, see [Changesets](#changesets)) | stage configuration changes in this changeset instead of making them |
 | `-o, --output FORMAT` | | `table` (default), `json`, `yaml` or `id` |
 | `-q, --quiet` | | print only errors (and the IDs of new objects) |
+| `--no-names` | | show inside addresses without their names: tables show `192.168.1.20 (laptop)` ([configuration.md](configuration.md#names)) |
 
 Exit codes: 0 ok, 1 error, 3 not authenticated or not allowed, 4 not
 found, 5 conflict, 6 invalid or refused by validation or nftables, 7

docs/configuration.md

@@ -32,12 +32,34 @@ reads the file when it starts.
 | `stats.top_n` | `100` | entries kept per top list, per hour and per day |
 | `shadow.enabled` | `false` | shadow mode: Housecarl's ruleset is loaded beside the firewall you have, but blocks, rejects and translates nothing; its counters, log and tracer show what it would do. No change is on probation, and takeovers and closing connections are refused ([shadow.md](shadow.md)) |
 | `shadow.position` | `after` | where Housecarl's filter chains run in shadow mode: `after` the other firewall's (`filter + 10`: it sees only what that one lets through, so what it would drop is what switching would break) or `before` them (`filter - 10`: it sees every packet) |
+| `names.enabled` | `true` | show inside addresses' names beside them, found by reverse lookups (below) |
+| `names.resolver` | `""` | the DNS server to ask, such as `10.10.0.1:53`; empty: the system's (`/etc/hosts`, then `/etc/resolv.conf`) |
+| `names.cache` | `10m` | how long a name, or the lack of one, is kept |
 
 Durations are written `15s`, `12h` or `30d`.
 
 Shadow mode is here, and not a firewall setting, so that no user or API
 token can switch enforcement off; restart housecarld to switch.
 
+### Names
+
+The web UI and `hc` show a name beside each **inside** address in
+connections, the log, quotas and traffic per device: `laptop
+192.168.1.20`. Housecarl finds it with a reverse (PTR) lookup, so the
+names are your reverse zones' (and `/etc/hosts`'). An address counts as
+inside when it is in a network connected to an inside zone's interface,
+or private (`10.0.0.0/8`, `172.16.0.0/12`, `192.168.0.0/16`, `fc00::/7`)
+and not in an external zone's network. Outside addresses get no name:
+their reverse zones belong to whoever holds the addresses, who would
+choose the names, and looking up every scanner is slow.
+
+Names are looked up when a page or `hc` asks, cached (a failed lookup is
+tried again after a minute), and never stored: statistics stay by
+address. With a split DNS (views), the server asked must answer the
+firewall as an inside client; set `names.resolver` if the system's
+resolver doesn't. IPv6 traffic per device is counted per /64, which has
+no name. `hc --no-names` leaves them out.
+
 The probation's length is a firewall setting, not here: `hc settings set
 --probation 5m`. So is counting traffic per device for the statistics:
 `hc settings set --stats-per-device on`.