code: public EpollSocketChannelConfig setTcpMd5Sig(Map<InetAddress, byte[]> keys) {
          try {
              ((EpollSocketChannel) channel).setTcpMd5Sig(keys);
              return this;
          } catch (IOException e) {
              throw new ChannelException(e);
          }
      }
docs: Set the {@code TCP_MD5SIG} option on the socket. See {@code linux/tcp.h} for more details.
  Keys can only be set on, not read to prevent a potential leak, as they are confidential.
  Allowing them being read would mean anyone with access to the channel could get them.