bbr_inflight
inflight >= bbr_inflight(sk, bw, bbr->pacing_gain));
inflight <= bbr_inflight(sk, bw, BBR_UNIT);
bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT);
bbr_inflight(sk, bbr_max_bw(sk), BBR_UNIT))