the length of the header in 32-bit multiples, it is accurate
to calculate data address by th+HLEN*4 */
data = data_start = (char *)th + (th->doff << 2);
the length of the header in 32-bit multiples, it is accurate
to calculate data address by th+HLEN*4 */
data = data_start = (char *)th + (th->doff << 2);