Improve DNS output: distinguish NS resolution failures from domain errors (#20)

internal/output/stats.go

@@ -144,6 +144,8 @@ func summaryTypeLabel(respType string) string {
 		return "query type not implemented by server"
 	case "cname_loop":
 		return "resulted in a CNAME loop"
+	case "ns_error":
+		return "nameserver lookup failed"
 	case "error":
 		return "resulted in an error"
 	case "referral":

internal/output/stats_test.go

@@ -88,6 +88,7 @@ func TestSummaryTypeLabelAllTypes(t *testing.T) {
 		"refused":    "query refused by server",
 		"notimp":     "query type not implemented by server",
 		"cname_loop": "resulted in a CNAME loop",
+		"ns_error":   "nameserver lookup failed",
 		"error":      "resulted in an error",
 		"referral":   "resulted in a referral",
 		"unknown_type": "unknown_type",

internal/output/text.go

@@ -220,6 +220,12 @@ func (f *textFormatter) formatResultLine(result traverse.TraversalResult) string
 			msg = result.Response.ErrorMessage
 		}
 		return f.colorize(fmt.Sprintf("%s %s", prob, msg), colorRed)
+	case traverse.RespNSResolutionFailed:
+		msg := "nameserver lookup failed"
+		if result.Response.ErrorMessage != "" {
+			msg = result.Response.ErrorMessage
+		}
+		return f.colorize(fmt.Sprintf("%s %s", prob, msg), colorYellow)
 	case traverse.RespError:
 		msg := "resulted in an error"
 		if result.Response.ErrorMessage != "" {

internal/output/text_test.go

@@ -121,6 +121,7 @@ Answers: []miekgdns.RR{
 {"refused", traverse.RespREFUSED, nil, ""},
 {"notimp", traverse.RespNOTIMPL, nil, ""},
 {"cname_loop", traverse.RespCNAMELoop, nil, "loop detected"},
+{"ns_error", traverse.RespNSResolutionFailed, nil, "nameserver ns1.example.com could not be resolved"},
 {"error", traverse.RespError, nil, "something went wrong"},
 }