Modify HTTP status codes to affect the error

doh-server/server.go

@@ -205,7 +205,7 @@ func (s *Server) handlerFunc(w http.ResponseWriter, r *http.Request) {
 
 	resp, err := s.doDNSQuery(msg)
 	if err != nil {
-		jsonDNS.FormatError(w, fmt.Sprintf("DNS query failure (%s)", err.Error()), 503)
+		jsonDNS.FormatError(w, fmt.Sprintf("DNS query failure (%s)", err.Error()), 502)
 		return
 	}
 	respJson := jsonDNS.Marshal(resp)
@@ -223,6 +223,9 @@ func (s *Server) handlerFunc(w http.ResponseWriter, r *http.Request) {
 		}
 		w.Header().Set("Expires", respJson.EarliestExpires.Format(time.RFC1123))
 	}
+	if respJson.Status == dns.RcodeServerFailure {
+		w.WriteHeader(503)
+	}
 	w.Write(respStr)
 }