hosts middleware should return NoError if other records exist in the zone (#782)

* hosts middleware should return NoError if other records exist in the zone

* return RcodeSuccess for hosts queries for non A,AAAA records if the zone exists

* return NXDOMAIN instead of REFUSED when zone is not found

middleware/hosts/hosts.go

@@ -59,7 +59,9 @@ func (h Hosts) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 		if h.Fallthrough {
 			return middleware.NextOrFailure(h.Name(), h.Next, ctx, w, r)
 		}
-		return dns.RcodeRefused, nil
+		if !h.otherRecordsExist(state.QType(), qname) {
+			return dns.RcodeNameError, nil
+		}
 	}
 
 	m := new(dns.Msg)
@@ -73,6 +75,28 @@ func (h Hosts) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 	return dns.RcodeSuccess, nil
 }
 
+func (h Hosts) otherRecordsExist(qtype uint16, qname string) bool {
+	switch qtype {
+	case dns.TypeA:
+		if len(h.LookupStaticHostV6(qname)) > 0 {
+			return true
+		}
+	case dns.TypeAAAA:
+		if len(h.LookupStaticHostV4(qname)) > 0 {
+			return true
+		}
+	default:
+		if len(h.LookupStaticHostV4(qname)) > 0 {
+			return true
+		}
+		if len(h.LookupStaticHostV6(qname)) > 0 {
+			return true
+		}
+	}
+	return false
+
+}
+
 // Name implements the middleware.Handle interface.
 func (h Hosts) Name() string { return "hosts" }
 

middleware/hosts/hosts_test.go

@@ -78,6 +78,14 @@ var hostsTestCases = []test.Case{
 			test.PTR("1.0.0.127.in-addr.arpa. 3600 PTR localhost.domain."),
 		},
 	},
+	{
+		Qname: "example.org.", Qtype: dns.TypeAAAA,
+		Answer: []dns.RR{},
+	},
+	{
+		Qname: "example.org.", Qtype: dns.TypeMX,
+		Answer: []dns.RR{},
+	},
 }
 
 const hostsExample = `