Sets from Jarl: sets holding the addresses of names in Jarl

A set can take its addresses from Jarl: every A and AAAA record of its
names (NAME@VIEW), CNAMEs followed within Jarl's zones in the same view.
housecarld reads them every jarl.refresh and after each change, keeps
only the addresses within the zones and networks the set allows, and
keeps what it last read (saved in the database and the boot ruleset)
while Jarl can't be reached. A change of the addresses applies the
ruleset again without a history entry and is audited (set.jarl).

hc set add --jarl --within, hc set jarl; the kind "from Jarl" and
Addresses… on the Sets page; GET /sets/{name}/jarl and /jarl/refresh;
validation codes set_jarl_*, status warnings jarl_*; docs/jarl.md.
e2e phase with scripts/fakejarl.

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

cmd/housecarld/main.go

@@ -30,6 +30,7 @@ import (
 	"housecarl/internal/engine"
 	"housecarl/internal/hostif"
 	"housecarl/internal/jarl"
+	"housecarl/internal/jarlsets"
 	"housecarl/internal/linkwatch"
 	"housecarl/internal/model"
 	"housecarl/internal/names"
@@ -165,19 +166,43 @@ func serveCmd() *cobra.Command {
 			for _, p := range eng.Problems() {
 				a.log.Warn("configuration problem: "+p.Message, "object", p.Object, "code", p.Code)
 			}
-			var acme *certs.Manager
-			if a.cfg.TLS.ACME.Domain != "" {
+			var jc *jarl.Client
+			if a.cfg.Jarl.Enabled() {
 				tok, err := a.cfg.Jarl.ReadToken()
 				if err != nil {
 					return err
 				}
-				jc, err := jarl.New(a.cfg.Jarl.Server, tok, a.cfg.Jarl.CACert, a.cfg.Jarl.Insecure)
-				if err != nil {
+				if jc, err = jarl.New(a.cfg.Jarl.Server, tok, a.cfg.Jarl.CACert, a.cfg.Jarl.Insecure); err != nil {
 					return err
 				}
+			}
+			var acme *certs.Manager
+			if a.cfg.TLS.ACME.Domain != "" {
+				if jc == nil {
+					return errors.New("tls.acme needs Jarl: set jarl.server and its token (docs/certificates.md)")
+				}
 				acme = certs.New(ctx, certs.Config{ACME: a.cfg.TLS.ACME, Version: version.Short()}, jc, a.store, a.log)
 				go acme.Run(ctx)
 			}
+			// The sets whose addresses come from Jarl: what was last read
+			// is put in force at once, Jarl is read again soon after.
+			jarlSets := &jarlsets.Resolver{Interval: time.Duration(a.cfg.Jarl.Refresh), State: eng.State, Log: a.log,
+				Apply: func(ctx context.Context) error {
+					if err := eng.ApplyCurrent(ctx); err != nil {
+						return err
+					}
+					return fw.SaveBoot(eng.State())
+				},
+				Audit: func(ctx context.Context, set, detail string) {
+					eng.Audit(ctx, &auth.Principal{Method: "jarl"}, "set.jarl", set, "success", detail)
+				},
+				Load: func(ctx context.Context) (string, error) { return a.store.GetMeta(ctx, jarlsets.MetaKey) },
+				Save: func(ctx context.Context, v string) error { return a.store.SetMeta(ctx, jarlsets.MetaKey, v) }}
+			if jc != nil {
+				jarlSets.Source = jc
+			}
+			jarlSets.Restore(ctx)
+			fw.JarlSets = jarlSets
 			var resolver *names.Resolver
 			if a.cfg.Names.Enabled {
 				resolver = names.New(a.cfg.Names.Resolver, time.Duration(a.cfg.Names.Cache))
@@ -186,8 +211,9 @@ func serveCmd() *cobra.Command {
 				Listen: a.cfg.Listen, TLSCertFile: a.cfg.TLS.CertFile, TLSKeyFile: a.cfg.TLS.KeyFile, TrustedProxies: a.cfg.Proxies(),
 				SessionLifetime: time.Duration(a.cfg.Session.Lifetime), SessionIdle: time.Duration(a.cfg.Session.IdleTimeout),
 				CookieSecure: a.cfg.Session.CookieSecure, Socket: a.cfg.Socket, ACME: acme,
-				Shadow: a.cfg.Shadow.Enabled, ShadowPosition: a.cfg.Shadow.Position, Names: resolver,
+				Shadow: a.cfg.Shadow.Enabled, ShadowPosition: a.cfg.Shadow.Position, Names: resolver, JarlSets: jarlSets,
 			}, eng, fw, host, a.log, web.FS())
+			jarlSets.Connected = srv.Connected
 			// Put the ruleset in force: what was on probation when
 			// housecarld stopped is rolled back first. An empty
 			// configuration applies nothing: its default policies would
@@ -217,6 +243,7 @@ func serveCmd() *cobra.Command {
 			go func() {
 				err := linkwatch.Watch(ctx, func() {
 					host.Forget()
+					jarlSets.Kick() // a zone's networks may have changed
 					if !fw.FlowtableStale(eng.State()) {
 						return
 					}
@@ -253,6 +280,7 @@ func serveCmd() *cobra.Command {
 					}
 				}()
 			}
+			go jarlSets.Run(ctx)
 			go nflog.Listen(ctx, render.LogGroup, a.log, srv.LogPacket)
 			go srv.RunQuotas(ctx)
 			srv.SetConntrack(conntrack.Client{})