Function bbr_substate_change

freebsd/netinet/tcp_stacks/bbr.c:10396–10540

}

static void
bbr_substate_change(struct tcp_bbr *bbr, uint32_t cts, int32_t line, int dolog)
{
	/*
	 * Now what state are we going into now? Is there adjustments
	 * needed?
	 */
	int32_t old_state, old_gain;

	old_state = bbr_state_val(bbr);
	old_gain = bbr->r_ctl.rc_bbr_hptsi_gain;
	if (bbr_state_val(bbr) == BBR_SUB_LEVEL1) {
		/* Save the lowest srtt we saw in our end of the sub-state */
		bbr->rc_hit_state_1 = 0;
		if (bbr->r_ctl.bbr_smallest_srtt_this_state != 0xffffffff)
			bbr->r_ctl.bbr_smallest_srtt_state2 = bbr->r_ctl.bbr_smallest_srtt_this_state;
	}
	bbr->rc_bbr_substate++;
	if (bbr->rc_bbr_substate >= BBR_SUBSTATE_COUNT) {
		/* Cycle back to first state-> gain */
		bbr->rc_bbr_substate = 0;
	}
	if (bbr_state_val(bbr) == BBR_SUB_GAIN) {
		/*
		 * We enter the gain(5/4) cycle (possibly less if
		 * shallow buffer detection is enabled)
		 */
		if (bbr->skip_gain) {
			/*
			 * Hardware pacing has set our rate to
			 * the max and limited our b/w just
			 * do level i.e. no gain.
			 */
			bbr->r_ctl.rc_bbr_hptsi_gain = bbr_hptsi_gain[BBR_SUB_LEVEL1];
		} else if (bbr->gain_is_limited &&
			   bbr->bbr_hdrw_pacing &&
			   bbr->r_ctl.crte) {
			/*
			 * We can't gain above the hardware pacing
			 * rate which is less than our rate + the gain
			 * calculate the gain needed to reach the hardware
			 * pacing rate..
			 */
			uint64_t bw, rate, gain_calc;

			bw = bbr_get_bw(bbr);
			rate = bbr->r_ctl.crte->rate;
			if ((rate > bw) &&
			    (((bw *  (uint64_t)bbr_hptsi_gain[BBR_SUB_GAIN]) / (uint64_t)BBR_UNIT) > rate)) {
				gain_calc = (rate * BBR_UNIT) / bw;
				if (gain_calc < BBR_UNIT)
					gain_calc = BBR_UNIT;
				bbr->r_ctl.rc_bbr_hptsi_gain = (uint16_t)gain_calc;
			} else {
				bbr->r_ctl.rc_bbr_hptsi_gain = bbr_hptsi_gain[BBR_SUB_GAIN];
			}
		} else
			bbr->r_ctl.rc_bbr_hptsi_gain = bbr_hptsi_gain[BBR_SUB_GAIN];