IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED
IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED &&
sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;