check: dns-record: add support for MX and NS types (#537)

check/dns-record/check.go

@@ -52,6 +52,10 @@ func New(_ check.Database, configure func(interface{}) error) (check.Check, erro
 		check.lookup = lookupAAAA
 	case "CNAME":
 		check.lookup = lookupCNAME
+	case "MX":
+		check.lookup = lookupMX
+	case "NS":
+		check.lookup = lookupNS
 	case "TXT":
 		check.lookup = lookupTXT
 	default:
@@ -89,21 +93,25 @@ func resolver(addr string) *net.Resolver {
 }
 
 func lookupA(r *net.Resolver, name string) ([]string, error) {
-	records, err := r.LookupIP(context.Background(), "ip4", name)
-
-	if err != nil {
-		return nil, err
-	}
-	return mapToStrings(records), nil
+	return lookupIP(r, "ip4", name)
 }
 
 func lookupAAAA(r *net.Resolver, name string) ([]string, error) {
-	records, err := r.LookupIP(context.Background(), "ip6", name)
+	return lookupIP(r, "ip6", name)
+}
+
+func lookupIP(r *net.Resolver, network, name string) ([]string, error) {
+	ips, err := r.LookupIP(context.Background(), network, name)
 
 	if err != nil {
 		return nil, err
 	}
-	return mapToStrings(records), nil
+	records := make([]string, len(ips))
+
+	for i, ip := range ips {
+		records[i] = ip.String()
+	}
+	return records, nil
 }
 
 func lookupCNAME(r *net.Resolver, name string) ([]string, error) {
@@ -115,15 +123,34 @@ func lookupCNAME(r *net.Resolver, name string) ([]string, error) {
 	return []string{record}, nil
 }
 
-func lookupTXT(r *net.Resolver, name string) ([]string, error) {
-	return r.LookupTXT(context.Background(), name)
+func lookupMX(r *net.Resolver, name string) ([]string, error) {
+	mxs, err := r.LookupMX(context.Background(), name)
+
+	if err != nil {
+		return nil, err
+	}
+	records := make([]string, len(mxs))
+
+	for i, mx := range mxs {
+		records[i] = mx.Host
+	}
+	return records, nil
 }
 
-func mapToStrings[T fmt.Stringer](values []T) []string {
-	s := make([]string, len(values))
+func lookupNS(r *net.Resolver, name string) ([]string, error) {
+	nss, err := r.LookupNS(context.Background(), name)
+
+	if err != nil {
+		return nil, err
+	}
+	records := make([]string, len(nss))
 
-	for i, val := range values {
-		s[i] = val.String()
+	for i, ns := range nss {
+		records[i] = ns.Host
 	}
-	return s
+	return records, nil
+}
+
+func lookupTXT(r *net.Resolver, name string) ([]string, error) {
+	return r.LookupTXT(context.Background(), name)
 }