checker: split monolithic rule into per-concern rules

checker/rules_recursion.go

@@ -0,0 +1,53 @@
+package checker
+
+import (
+	"context"
+	"fmt"
+
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+// noRecursionRule flags authoritative nameservers that still advertise
+// recursion to the public (RA bit set), a classic open-resolver posture.
+type noRecursionRule struct{}
+
+func (r *noRecursionRule) Name() string { return "ns_no_recursion" }
+func (r *noRecursionRule) Description() string {
+	return "Verifies that authoritative nameservers do not advertise recursion (RA bit unset)"
+}
+
+func (r *noRecursionRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
+	report, errSt := loadReport(ctx, obs, "ns_recursion_error")
+	if errSt != nil {
+		return []sdk.CheckState{*errSt}
+	}
+
+	servers := probedServers(report)
+	if len(servers) == 0 {
+		return []sdk.CheckState{noProbesState("ns_recursion_skipped")}
+	}
+
+	out := make([]sdk.CheckState, 0, len(servers))
+	for _, srv := range servers {
+		state := sdk.CheckState{
+			Subject: serverLabel(srv),
+			Meta:    serverMeta(srv),
+		}
+		switch {
+		case srv.SOA.Error != "":
+			state.Status = sdk.StatusUnknown
+			state.Code = "ns_recursion_skipped"
+			state.Message = fmt.Sprintf("query failed: %s", srv.SOA.Error)
+		case srv.SOA.RecursionAvailable:
+			state.Status = sdk.StatusWarn
+			state.Code = "ns_recursion_available"
+			state.Message = "recursion available (RA bit set)"
+		default:
+			state.Status = sdk.StatusOK
+			state.Code = "ns_recursion_ok"
+			state.Message = "recursion not available"
+		}
+		out = append(out, state)
+	}
+	return out
+}