code: protected ByteBuf allocateBuffer(
          ChannelHandlerContext ctx,
          @SuppressWarnings("unused") AddressedEnvelope<DnsResponse, InetSocketAddress> msg) throws Exception {
          return ctx.alloc().ioBuffer(1024);
      }
docs: Allocate a {@link ByteBuf} which will be used for constructing a datagram packet.
  Sub-classes may override this method to return a {@link ByteBuf} with a perfect matching initial capacity.