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>

internal/config/config.go

@@ -44,6 +44,19 @@ type Config struct {
 	// Shadow loads the ruleset without letting it block, reject or
 	// translate anything, beside the firewall in force (docs/shadow.md).
 	Shadow Shadow `yaml:"shadow"`
+	// Names shows inside addresses' names, by reverse lookups
+	// (docs/configuration.md).
+	Names Names `yaml:"names"`
+}
+
+// Names configures the reverse lookups that put names beside inside
+// addresses in the web UI and hc.
+type Names struct {
+	Enabled bool `yaml:"enabled"`
+	// Resolver is a DNS server ("10.10.0.1:53"; "": the system's).
+	Resolver string `yaml:"resolver"`
+	// Cache is how long a name is kept.
+	Cache Duration `yaml:"cache"`
 }
 
 // Shadow is shadow mode: Housecarl's ruleset is loaded and counts, logs
@@ -224,6 +237,7 @@ func Default() *Config {
 		Stats: Stats{Enabled: true, Database: "/var/lib/housecarl/stats.db", TopN: 100,
 			Retention: StatsRetention{Minute: Duration(7 * 24 * time.Hour), Hour: Duration(90 * 24 * time.Hour), Day: Duration(730 * 24 * time.Hour)}},
 		Shadow: Shadow{Position: ShadowAfter},
+		Names:  Names{Enabled: true, Cache: Duration(10 * time.Minute)},
 		TLS:    TLS{ACME: ACME{Directory: "letsencrypt-staging", Resolvers: []string{"1.1.1.1:53", "9.9.9.9:53", "8.8.8.8:53"}, CheckPropagation: true}},
 	}
 }
@@ -298,6 +312,14 @@ func (c *Config) check() error {
 	if c.Shadow.Position != ShadowAfter && c.Shadow.Position != ShadowBefore {
 		return fmt.Errorf("shadow.position must be after or before")
 	}
+	if c.Names.Resolver != "" {
+		if _, err := netip.ParseAddrPort(c.Names.Resolver); err != nil {
+			return fmt.Errorf("names.resolver must be an address and port, such as 10.10.0.1:53")
+		}
+	}
+	if c.Names.Cache <= 0 {
+		return fmt.Errorf("names.cache must be a duration, such as 10m")
+	}
 	return nil
 }