inline truncateResponse

nameserver/dns.go

@@ -247,19 +247,12 @@ func (h *handler) makeResponse(req *dns.Msg, answers []dns.RR) *dns.Msg {
 	response.RecursionAvailable = true
 	response.Authoritative = true
 	response.Answer = answers
-	h.truncateResponse(req, response)
-	return response
-}
 
-func (h *handler) truncateResponse(req, response *dns.Msg) {
 	maxSize := h.getMaxResponseSize(req)
 	if len(response.Answer) <= 1 || maxSize <= 0 {
-		return
+		return response
 	}
 
-	// take a copy of answers, as we're going to mutate response
-	answers := response.Answer
-
 	// search for smallest i that is too big
 	i := sort.Search(len(response.Answer), func(i int) bool {
 		// return true if too big
@@ -268,11 +261,12 @@ func (h *handler) truncateResponse(req, response *dns.Msg) {
 	})
 	if i == len(answers) {
 		response.Answer = answers
-		return
+		return response
 	}
 
 	response.Answer = answers[:i]
 	response.Truncated = true
+	return response
 }
 
 func (h *handler) getMaxResponseSize(req *dns.Msg) int {

nameserver/dns_test.go

@@ -83,18 +83,17 @@ func TestTruncateResponse(t *testing.T) {
 	}
 
 	for i := 0; i < 10000; i++ {
-		// generate a random msg
-		response := &dns.Msg{}
+		// generate a random answer set
 		numAnswers := 40 + rand.Intn(200)
-		response.Answer = make([]dns.RR, numAnswers)
+		answers := make([]dns.RR, numAnswers)
 		for j := 0; j < numAnswers; j++ {
-			response.Answer[j] = &dns.A{Hdr: header, A: address.Address(j).IP4()}
+			answers[j] = &dns.A{Hdr: header, A: address.Address(j).IP4()}
 		}
 
 		// pick a random max size, truncate response to that, check it
-		maxSize := 512 + rand.Intn(response.Len()-512)
+		maxSize := 512 + rand.Intn(2*512)
 		h := handler{maxResponseSize: maxSize}
-		h.truncateResponse(&dns.Msg{}, response)
+		response := h.makeResponse(&dns.Msg{}, answers)
 		require.True(t, response.Len() <= maxSize)
 	}
 }