CUBIC_BETAB
K = tcp_cubic_cbrt(tp->snd_cubic_wmax / CUBIC_BETAB *
tp->snd_cubic_wmax * CUBIC_BETAA / CUBIC_BETAB / 2;
tcp_common_congestion_exp(tp, CUBIC_BETAA, CUBIC_BETAB);
w_tcp = tp->snd_cubic_wmax * CUBIC_BETAA / CUBIC_BETAB +