plugin/hosts: fall through unsupported query types (#8193)

plugin/hosts/hosts.go

@@ -50,6 +50,10 @@ func (h Hosts) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 	case dns.TypeAAAA:
 		ips := h.LookupStaticHostV6(qname)
 		answers = aaaa(qname, h.options.ttl, ips)
+	default:
+		if h.Fall.Through(qname) {
+			return plugin.NextOrFailure(h.Name(), h.Next, ctx, w, r)
+		}
 	}
 
 	// Only on NXDOMAIN we will fallthrough.

plugin/hosts/hosts_test.go

@@ -57,6 +57,35 @@ func TestLookupA(t *testing.T) {
 	}
 }
 
+func TestFallthroughUnsupportedType(t *testing.T) {
+	h := Hosts{
+		Next: test.NextHandler(dns.RcodeRefused, nil),
+		Hostsfile: &Hostsfile{
+			Origins: []string{"."},
+			hmap:    newMap(),
+			inline:  newMap(),
+			options: newOptions(),
+		},
+		Fall: fall.Root,
+	}
+	h.hmap = h.parse(strings.NewReader(hostsExample))
+
+	m := new(dns.Msg)
+	m.SetQuestion("example.org.", dns.TypeTXT)
+	rec := dnstest.NewRecorder(&test.ResponseWriter{})
+
+	rcode, err := h.ServeDNS(context.Background(), rec, m)
+	if err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+	if rcode != dns.RcodeRefused {
+		t.Fatalf("Expected fallthrough rcode %d, got %d", dns.RcodeRefused, rcode)
+	}
+	if rec.Msg != nil {
+		t.Fatalf("Expected no response from hosts after fallthrough, got %#v", rec.Msg)
+	}
+}
+
 var hostsTestCases = []test.Case{
 	{
 		Qname: "example.org.", Qtype: dns.TypeA,