DNS hosts: Support returning RCode (#4681)

features/dns/client.go

@@ -42,6 +42,24 @@ func (e RCodeError) Error() string {
 	return serial.Concat("rcode: ", uint16(e))
 }
 
+func (RCodeError) IP() net.IP {
+	panic("Calling IP() on a RCodeError.")
+}
+
+func (RCodeError) Domain() string {
+	panic("Calling Domain() on a RCodeError.")
+}
+
+func (RCodeError) Family() net.AddressFamily {
+	panic("Calling Family() on a RCodeError.")
+}
+
+func (e RCodeError) String() string {
+	return e.Error()
+}
+
+var _ net.Address = (*RCodeError)(nil)
+
 func RCodeFromError(err error) uint16 {
 	if err == nil {
 		return 0