api/v1alpha1/bindzone_types.go

@@ -103,7 +103,7 @@ type BindZoneSpec struct {
 	// +optional
 	DNSSECPolicyRef string `json:"dnssecPolicyRef,omitempty"`
 
-	// Forwarders lists upstreams for a forward-type zone.
+	// Forwarders lists upstreams for a forward-type zone; an empty list disables forwarding for the zone.
 	// +optional
 	Forwarders []string `json:"forwarders,omitempty"`
 

config/crd/bases/bind.unkin.net_bindzones.yaml

@@ -90,7 +90,8 @@ spec:
                   When true, UpdateKeyRef must reference a BindTSIGKey.
                 type: boolean
               forwarders:
-                description: Forwarders lists upstreams for a forward-type zone.
+                description: Forwarders lists upstreams for a forward-type zone; an
+                  empty list disables forwarding for the zone.
                 items:
                   type: string
                 type: array

config/crd/install.yaml

@@ -2756,7 +2756,8 @@ spec:
                   When true, UpdateKeyRef must reference a BindTSIGKey.
                 type: boolean
               forwarders:
-                description: Forwarders lists upstreams for a forward-type zone.
+                description: Forwarders lists upstreams for a forward-type zone; an
+                  empty list disables forwarding for the zone.
                 items:
                   type: string
                 type: array

internal/bind/render.go

@@ -154,8 +154,10 @@ func renderForwardZone(z bindv1alpha1.BindZone, indent string) string {
 	b.WriteString(fmt.Sprintf("%szone \"%s\" {\n", indent, z.Spec.ZoneName))
 	b.WriteString(indent + "    type forward;\n")
 	b.WriteString(indent + "    forward only;\n")
-	if len(z.Spec.Forwarders) > 0 {
-		b.WriteString(fmt.Sprintf("%s    forwarders { %s };\n", indent, terminate(z.Spec.Forwarders)))
+	if list := terminate(z.Spec.Forwarders); list != "" {
+		b.WriteString(fmt.Sprintf("%s    forwarders { %s };\n", indent, list))
+	} else {
+		b.WriteString(indent + "    forwarders { };\n")
 	}
 	b.WriteString(indent + "};\n")
 	return b.String()

internal/bind/render_test.go

@@ -261,3 +261,19 @@ func TestRenderDeterministicWithShuffledForwards(t *testing.T) {
 		t.Fatalf("render must be independent of forward-zone input order:\n--- A ---\n%s\n--- B ---\n%s", pa, pb)
 	}
 }
+
+func TestRenderForwardZoneForwarders(t *testing.T) {
+	for _, tc := range []struct {
+		fwd  []string
+		want string
+	}{
+		{nil, "    forwarders { };\n"},
+		{[]string{"198.18.19.15", "198.18.19.16;"}, "    forwarders { 198.18.19.15; 198.18.19.16; };\n"},
+	} {
+		z := bindv1alpha1.BindZone{Spec: bindv1alpha1.BindZoneSpec{ZoneName: "spamhaus.org", Type: bindv1alpha1.ZoneForward, Forwarders: tc.fwd}}
+		want := "zone \"spamhaus.org\" {\n    type forward;\n    forward only;\n" + tc.want + "};\n"
+		if got := renderForwardZone(z, ""); got != want {
+			t.Errorf("forwarders %v:\ngot  %q\nwant %q", tc.fwd, got, want)
+		}
+	}
+}