code: static byte[] inet6AsByteArray(InetAddress ia) {
          if (ia instanceof Inet6Address) {
              return ia.getAddress();
          }
  
          // need to construct IPv4-mapped address
          if (ia instanceof Inet4Address) {
              byte[] ip4address = ia.getAddress();
              byte[] address = new byte[16];
              address[10] = (byte)0xff;
              address[11] = (byte)0xff;
              address[12] = ip4address[0];
              address[13] = ip4address[1];
              address[14] = ip4address[2];
              address[15] = ip4address[3];
              return address;
          }
  
          throw new AssertionError("Should not reach here");
      }
docs: Returns an IPv6 address as a byte array