FLAG_OPTION_SACK_PERMITTED
fFlags &= ~FLAG_OPTION_SACK_PERMITTED;
if ((fFlags & FLAG_OPTION_SACK_PERMITTED) != 0)
&& (fFlags & FLAG_OPTION_SACK_PERMITTED) != 0) {
| FLAG_OPTION_SACK_PERMITTED | FLAG_AUTO_RECEIVE_BUFFER_SIZE)