DNSSEC: say where the DS record really goes

The DNSSEC tab said "give this to your registrar" for every zone whose
parent wasn't in Jarl in the same view. The DNSSEC response now has
ds_at/ds_place/ds_note: the parent zone in Jarl (any view, its own
first, then a public one), the registrar for a registered domain, the
parent zone wherever it is hosted for a subdomain, the ISP or RIR for a
reverse zone, and nowhere for a private name. The page and the CLI use
them.

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

internal/server/h_dnssec.go

@@ -36,31 +36,70 @@ func (s *Server) zoneDNSSEC(w http.ResponseWriter, r *http.Request, p *auth.Prin
 		return badRequest("only primary zones are signed by Jarl (this is a %s zone)", z.Type)
 	}
 	resp := api.DNSSECResponse{Zone: z.Name, View: st.ViewName(z), Type: z.Type, Status: s.eng.DNSSEC(r.Context(), st, z), Registrar: s.registrarFor(z)}
-	if pz := parentInJarl(st, z); pz != nil {
+	public := map[int64]bool{}
+	for _, e := range s.eng.Exposures(st) {
+		public[e.ViewID] = e.Public
+	}
+	name := dnsname.Display(z.Name)
+	reg, regOK := dnsname.RegisteredDomain(z.Name)
+	switch pz := parentInJarl(st, z, public); {
+	case pz != nil:
+		resp.DSAt = "parent_zone"
 		resp.ParentZone, resp.ParentZoneID, resp.ParentView = pz.Name, pz.ID, st.ViewName(pz)
 		for _, rec := range st.ServedRecords(pz.ID) {
 			if rec.Name == z.Name && rec.Type == "DS" {
 				resp.ParentDS = append(resp.ParentDS, rec.Data)
 			}
 		}
+		resp.DSPlace = "in the parent zone " + dnsname.Display(pz.Name)
+		if pz.ViewID != z.ViewID {
+			resp.DSPlace += " (view " + st.ViewName(pz) + ")"
+		}
+	case dnsname.IsReverse(z.Name):
+		resp.DSAt = "reverse"
+		resp.DSPlace = "with whoever delegates " + name + " to you (your ISP, or your RIR for an address block of your own; many ISPs don't take DS records)"
+	case !regOK:
+		resp.DSAt = "none"
+		resp.DSNote = "No zone on the internet delegates " + name + ", so it can't get a DS record and resolvers never validate it. Signing only matters for a zone on the internet."
+	case reg == name:
+		resp.DSAt, resp.DSPlace = "registrar", "at your registrar"
+	default:
+		resp.DSAt = "parent"
+		resp.DSPlace = "in its parent zone (most likely " + reg + "), wherever that zone's DNS is hosted (at Porkbun: " + reg + "'s DNS records, as a DS record named " + strings.TrimSuffix(name, "."+reg) + ")"
 	}
 	writeJSON(w, http.StatusOK, resp)
 	return nil
 }
 
-// parentInJarl returns the primary zone in z's view that z is delegated
-// from, if Jarl has it.
-func parentInJarl(st *model.State, z *model.Zone) *model.Zone {
-	var best *model.Zone
-	for _, o := range st.ZonesInView(z.ViewID) {
-		if o.ID == z.ID || o.Type != model.ZonePrimary || o.Name == z.Name || !dnsname.IsSubdomain(z.Name, o.Name) {
+// parentInJarl returns the primary zone in Jarl that z is delegated from:
+// in z's own view, else in another view, a public one first (the one the
+// internet asks).
+func parentInJarl(st *model.State, z *model.Zone, public map[int64]bool) *model.Zone {
+	in := func(viewID int64) *model.Zone {
+		var best *model.Zone
+		for _, o := range st.ZonesInView(viewID) {
+			if o.Type != model.ZonePrimary || o.Name == z.Name || !dnsname.IsSubdomain(z.Name, o.Name) {
+				continue
+			}
+			if best == nil || len(o.Name) > len(best.Name) {
+				best = o
+			}
+		}
+		return best
+	}
+	if pz := in(z.ViewID); pz != nil {
+		return pz
+	}
+	var other *model.Zone
+	for _, v := range st.OrderedViews() {
+		if v.ID == z.ViewID {
 			continue
 		}
-		if best == nil || len(o.Name) > len(best.Name) {
-			best = o
+		if pz := in(v.ID); pz != nil && (other == nil || public[v.ID] && !public[other.ViewID]) {
+			other = pz
 		}
 	}
-	return best
+	return other
 }
 
 // dsChecker returns the checker for parent DS lookups, with ?resolver=IP.