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Diffstat (limited to '')
| -rw-r--r-- | lib/ngtcp2_bbr2.c | 1489 |
1 files changed, 1489 insertions, 0 deletions
diff --git a/lib/ngtcp2_bbr2.c b/lib/ngtcp2_bbr2.c new file mode 100644 index 0000000..508ab55 --- /dev/null +++ b/lib/ngtcp2_bbr2.c @@ -0,0 +1,1489 @@ +/* + * ngtcp2 + * + * Copyright (c) 2021 ngtcp2 contributors + * + * Permission is hereby granted, free of charge, to any person obtaining + * a copy of this software and associated documentation files (the + * "Software"), to deal in the Software without restriction, including + * without limitation the rights to use, copy, modify, merge, publish, + * distribute, sublicense, and/or sell copies of the Software, and to + * permit persons to whom the Software is furnished to do so, subject to + * the following conditions: + * + * The above copyright notice and this permission notice shall be + * included in all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE + * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION + * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION + * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. + */ +#include "ngtcp2_bbr2.h" + +#include <assert.h> + +#include "ngtcp2_log.h" +#include "ngtcp2_macro.h" +#include "ngtcp2_mem.h" +#include "ngtcp2_rcvry.h" +#include "ngtcp2_rst.h" + +#define NGTCP2_BBR_MAX_BW_FILTERLEN 2 + +#define NGTCP2_BBR_EXTRA_ACKED_FILTERLEN 10 + +#define NGTCP2_BBR_STARTUP_PACING_GAIN ((double)2.77) + +#define NGTCP2_BBR_STARTUP_CWND_GAIN 2 + +#define NGTCP2_BBR_PROBE_RTT_CWND_GAIN ((double)0.5) + +#define NGTCP2_BBR_BETA_NUMER 7 +#define NGTCP2_BBR_BETA_DENOM 10 + +#define NGTCP2_BBR_LOSS_THRESH_NUMER 2 +#define NGTCP2_BBR_LOSS_THRESH_DENOM 100 + +#define NGTCP2_BBR_HEADROOM_NUMER 15 +#define NGTCP2_BBR_HEADROOM_DENOM 100 + +#define NGTCP2_BBR_PROBE_RTT_INTERVAL (5 * NGTCP2_SECONDS) +#define NGTCP2_BBR_MIN_RTT_FILTERLEN (10 * NGTCP2_SECONDS) + +#define NGTCP2_BBR_PROBE_RTT_DURATION (200 * NGTCP2_MILLISECONDS) + +#define NGTCP2_BBR_PACING_MARGIN_PERCENT 1 + +static void bbr_on_init(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp initial_ts); + +static void bbr_on_transmit(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts); + +static void bbr_reset_congestion_signals(ngtcp2_bbr2_cc *bbr); + +static void bbr_reset_lower_bounds(ngtcp2_bbr2_cc *bbr); + +static void bbr_init_round_counting(ngtcp2_bbr2_cc *bbr); + +static void bbr_init_full_pipe(ngtcp2_bbr2_cc *bbr); + +static void bbr_init_pacing_rate(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat); + +static void bbr_set_pacing_rate_with_gain(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + double pacing_gain); + +static void bbr_set_pacing_rate(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat); + +static void bbr_enter_startup(ngtcp2_bbr2_cc *bbr); + +static void bbr_check_startup_done(ngtcp2_bbr2_cc *bbr, + const ngtcp2_cc_ack *ack); + +static void bbr_update_on_ack(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts); + +static void bbr_update_model_and_state(ngtcp2_bbr2_cc *cc, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, + ngtcp2_tstamp ts); + +static void bbr_update_control_parameters(ngtcp2_bbr2_cc *cc, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack); + +static void bbr_update_on_loss(ngtcp2_bbr2_cc *cc, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_pkt *pkt, ngtcp2_tstamp ts); + +static void bbr_update_latest_delivery_signals(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_advance_latest_delivery_signals(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_update_congestion_signals(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack); + +static void bbr_adapt_lower_bounds_from_congestion(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_init_lower_bounds(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat); + +static void bbr_loss_lower_bounds(ngtcp2_bbr2_cc *bbr); + +static void bbr_bound_bw_for_model(ngtcp2_bbr2_cc *bbr); + +static void bbr_update_max_bw(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack); + +static void bbr_update_round(ngtcp2_bbr2_cc *bbr, const ngtcp2_cc_ack *ack); + +static void bbr_start_round(ngtcp2_bbr2_cc *bbr); + +static int bbr_is_in_probe_bw_state(ngtcp2_bbr2_cc *bbr); + +static void bbr_update_ack_aggregation(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, + ngtcp2_tstamp ts); + +static void bbr_enter_drain(ngtcp2_bbr2_cc *bbr); + +static void bbr_check_drain(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts); + +static void bbr_enter_probe_bw(ngtcp2_bbr2_cc *bbr, ngtcp2_tstamp ts); + +static void bbr_start_probe_bw_down(ngtcp2_bbr2_cc *bbr, ngtcp2_tstamp ts); + +static void bbr_start_probe_bw_cruise(ngtcp2_bbr2_cc *bbr); + +static void bbr_start_probe_bw_refill(ngtcp2_bbr2_cc *bbr); + +static void bbr_start_probe_bw_up(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts); + +static void bbr_update_probe_bw_cycle_phase(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, + ngtcp2_tstamp ts); + +static int bbr_check_time_to_cruise(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, ngtcp2_tstamp ts); + +static int bbr_has_elapsed_in_phase(ngtcp2_bbr2_cc *bbr, + ngtcp2_duration interval, ngtcp2_tstamp ts); + +static uint64_t bbr_inflight_with_headroom(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_raise_inflight_hi_slope(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_probe_inflight_hi_upward(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack); + +static void bbr_adapt_upper_bounds(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts); + +static int bbr_check_time_to_probe_bw(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts); + +static void bbr_pick_probe_wait(ngtcp2_bbr2_cc *bbr); + +static int bbr_is_reno_coexistence_probe_time(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static uint64_t bbr_target_inflight(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static int bbr_check_inflight_too_high(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts); + +static int is_inflight_too_high(const ngtcp2_rs *rs); + +static void bbr_handle_inflight_too_high(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_rs *rs, ngtcp2_tstamp ts); + +static void bbr_handle_lost_packet(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_pkt *pkt, ngtcp2_tstamp ts); + +static uint64_t bbr_inflight_hi_from_lost_packet(ngtcp2_bbr2_cc *bbr, + const ngtcp2_rs *rs, + const ngtcp2_cc_pkt *pkt); + +static void bbr_update_min_rtt(ngtcp2_bbr2_cc *bbr, const ngtcp2_cc_ack *ack, + ngtcp2_tstamp ts); + +static void bbr_check_probe_rtt(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts); + +static void bbr_enter_probe_rtt(ngtcp2_bbr2_cc *bbr); + +static void bbr_handle_probe_rtt(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts); + +static void bbr_check_probe_rtt_done(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, ngtcp2_tstamp ts); + +static void bbr_mark_connection_app_limited(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_exit_probe_rtt(ngtcp2_bbr2_cc *bbr, ngtcp2_tstamp ts); + +static void bbr_handle_restart_from_idle(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts); + +static uint64_t bbr_bdp_multiple(ngtcp2_bbr2_cc *bbr, uint64_t bw, double gain); + +static uint64_t bbr_quantization_budget(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + uint64_t inflight); + +static uint64_t bbr_inflight(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + uint64_t bw, double gain); + +static void bbr_update_max_inflight(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_update_offload_budget(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static uint64_t min_pipe_cwnd(size_t max_udp_payload_size); + +static void bbr_advance_max_bw_filter(ngtcp2_bbr2_cc *bbr); + +static void bbr_modulate_cwnd_for_recovery(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack); + +static void bbr_save_cwnd(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat); + +static void bbr_restore_cwnd(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat); + +static uint64_t bbr_probe_rtt_cwnd(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_bound_cwnd_for_probe_rtt(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_set_cwnd(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack); + +static void bbr_bound_cwnd_for_model(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat); + +static void bbr_set_send_quantum(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat); + +static int in_congestion_recovery(const ngtcp2_conn_stat *cstat, + ngtcp2_tstamp sent_time); + +static void bbr_handle_recovery(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack); + +static void bbr_on_init(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp initial_ts) { + ngtcp2_window_filter_init(&bbr->max_bw_filter, NGTCP2_BBR_MAX_BW_FILTERLEN); + ngtcp2_window_filter_init(&bbr->extra_acked_filter, + NGTCP2_BBR_EXTRA_ACKED_FILTERLEN); + + bbr->min_rtt = UINT64_MAX; + bbr->min_rtt_stamp = initial_ts; + /* remark: Use UINT64_MAX instead of 0 for consistency. */ + bbr->probe_rtt_done_stamp = UINT64_MAX; + bbr->probe_rtt_round_done = 0; + bbr->prior_cwnd = 0; + bbr->idle_restart = 0; + bbr->extra_acked_interval_start = initial_ts; + bbr->extra_acked_delivered = 0; + + bbr_reset_congestion_signals(bbr); + bbr_reset_lower_bounds(bbr); + bbr_init_round_counting(bbr); + bbr_init_full_pipe(bbr); + bbr_init_pacing_rate(bbr, cstat); + bbr_enter_startup(bbr); + + cstat->send_quantum = cstat->max_tx_udp_payload_size * 10; + + /* Missing in documentation */ + bbr->loss_round_start = 0; + bbr->loss_round_delivered = UINT64_MAX; + + bbr->rounds_since_bw_probe = 0; + + bbr->max_bw = 0; + bbr->bw = 0; + + bbr->cycle_count = 0; + + bbr->extra_acked = 0; + + bbr->bytes_lost_in_round = 0; + bbr->loss_events_in_round = 0; + + bbr->offload_budget = 0; + + bbr->probe_up_cnt = UINT64_MAX; + bbr->cycle_stamp = UINT64_MAX; + bbr->ack_phase = 0; + bbr->bw_probe_wait = 0; + bbr->bw_probe_samples = 0; + bbr->bw_probe_up_rounds = 0; + bbr->bw_probe_up_acks = 0; + + bbr->inflight_hi = UINT64_MAX; + bbr->bw_hi = UINT64_MAX; + + bbr->probe_rtt_expired = 0; + bbr->probe_rtt_min_delay = UINT64_MAX; + bbr->probe_rtt_min_stamp = initial_ts; + + bbr->in_loss_recovery = 0; + bbr->packet_conservation = 0; + + bbr->max_inflight = 0; + + bbr->congestion_recovery_start_ts = UINT64_MAX; + bbr->congestion_recovery_next_round_delivered = 0; + + bbr->prior_inflight_lo = 0; + bbr->prior_inflight_hi = 0; + bbr->prior_bw_lo = 0; +} + +static void bbr_reset_congestion_signals(ngtcp2_bbr2_cc *bbr) { + bbr->loss_in_round = 0; + bbr->bw_latest = 0; + bbr->inflight_latest = 0; +} + +static void bbr_reset_lower_bounds(ngtcp2_bbr2_cc *bbr) { + bbr->bw_lo = UINT64_MAX; + bbr->inflight_lo = UINT64_MAX; +} + +static void bbr_init_round_counting(ngtcp2_bbr2_cc *bbr) { + bbr->next_round_delivered = 0; + bbr->round_start = 0; + bbr->round_count = 0; +} + +static void bbr_init_full_pipe(ngtcp2_bbr2_cc *bbr) { + bbr->filled_pipe = 0; + bbr->full_bw = 0; + bbr->full_bw_count = 0; +} + +static void bbr_check_startup_full_bandwidth(ngtcp2_bbr2_cc *bbr) { + if (bbr->filled_pipe || !bbr->round_start || bbr->rst->rs.is_app_limited) { + return; + } + + if (bbr->max_bw * 100 >= bbr->full_bw * 125) { + bbr->full_bw = bbr->max_bw; + bbr->full_bw_count = 0; + } + + ++bbr->full_bw_count; + + if (bbr->full_bw_count >= 3) { + bbr->filled_pipe = 1; + + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, + "bbr2 filled pipe, full_bw=%" PRIu64, bbr->full_bw); + } +} + +static void bbr_check_startup_high_loss(ngtcp2_bbr2_cc *bbr, + const ngtcp2_cc_ack *ack) { + if (bbr->filled_pipe || !bbr->round_start || bbr->rst->rs.is_app_limited) { + return; + } + + if (bbr->loss_events_in_round <= 3) { + return; + } + + /* loss_thresh = 2% */ + if (bbr->bytes_lost_in_round * 100 <= ack->prior_bytes_in_flight * 2) { + return; + } + + bbr->filled_pipe = 1; +} + +static void bbr_init_pacing_rate(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat) { + double nominal_bandwidth = (double)bbr->initial_cwnd; + + cstat->pacing_rate = NGTCP2_BBR_STARTUP_PACING_GAIN * nominal_bandwidth / + (double)NGTCP2_MILLISECONDS; +} + +static void bbr_set_pacing_rate_with_gain(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + double pacing_gain) { + double rate = pacing_gain * (double)bbr->bw * + (100 - NGTCP2_BBR_PACING_MARGIN_PERCENT) / 100 / NGTCP2_SECONDS; + + if (bbr->filled_pipe || rate > cstat->pacing_rate) { + cstat->pacing_rate = rate; + } +} + +static void bbr_set_pacing_rate(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat) { + bbr_set_pacing_rate_with_gain(bbr, cstat, bbr->pacing_gain); +} + +static void bbr_enter_startup(ngtcp2_bbr2_cc *bbr) { + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, "bbr2 enter Startup"); + + bbr->state = NGTCP2_BBR2_STATE_STARTUP; + bbr->pacing_gain = NGTCP2_BBR_STARTUP_PACING_GAIN; + bbr->cwnd_gain = NGTCP2_BBR_STARTUP_CWND_GAIN; +} + +static void bbr_check_startup_done(ngtcp2_bbr2_cc *bbr, + const ngtcp2_cc_ack *ack) { + bbr_check_startup_full_bandwidth(bbr); + bbr_check_startup_high_loss(bbr, ack); + + if (bbr->state == NGTCP2_BBR2_STATE_STARTUP && bbr->filled_pipe) { + bbr_enter_drain(bbr); + } +} + +static void bbr_on_transmit(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + bbr_handle_restart_from_idle(bbr, cstat, ts); +} + +static void bbr_update_on_ack(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts) { + bbr_update_model_and_state(bbr, cstat, ack, ts); + bbr_update_control_parameters(bbr, cstat, ack); +} + +static void bbr_update_model_and_state(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, + ngtcp2_tstamp ts) { + bbr_update_latest_delivery_signals(bbr, cstat); + bbr_update_congestion_signals(bbr, cstat, ack); + bbr_update_ack_aggregation(bbr, cstat, ack, ts); + bbr_check_startup_done(bbr, ack); + bbr_check_drain(bbr, cstat, ts); + bbr_update_probe_bw_cycle_phase(bbr, cstat, ack, ts); + bbr_update_min_rtt(bbr, ack, ts); + bbr_check_probe_rtt(bbr, cstat, ts); + bbr_advance_latest_delivery_signals(bbr, cstat); + bbr_bound_bw_for_model(bbr); +} + +static void bbr_update_control_parameters(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack) { + bbr_set_pacing_rate(bbr, cstat); + bbr_set_send_quantum(bbr, cstat); + bbr_set_cwnd(bbr, cstat, ack); +} + +static void bbr_update_on_loss(ngtcp2_bbr2_cc *cc, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_pkt *pkt, ngtcp2_tstamp ts) { + bbr_handle_lost_packet(cc, cstat, pkt, ts); +} + +static void bbr_update_latest_delivery_signals(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + bbr->loss_round_start = 0; + bbr->bw_latest = ngtcp2_max(bbr->bw_latest, cstat->delivery_rate_sec); + bbr->inflight_latest = + ngtcp2_max(bbr->inflight_latest, bbr->rst->rs.delivered); + + if (bbr->rst->rs.prior_delivered >= bbr->loss_round_delivered) { + bbr->loss_round_delivered = bbr->rst->delivered; + bbr->loss_round_start = 1; + } +} + +static void bbr_advance_latest_delivery_signals(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + if (bbr->loss_round_start) { + bbr->bw_latest = cstat->delivery_rate_sec; + bbr->inflight_latest = bbr->rst->rs.delivered; + } +} + +static void bbr_update_congestion_signals(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack) { + bbr_update_max_bw(bbr, cstat, ack); + + if (ack->bytes_lost) { + bbr->bytes_lost_in_round += ack->bytes_lost; + ++bbr->loss_events_in_round; + + if (!bbr->loss_in_round) { + bbr->loss_in_round = 1; + bbr->loss_round_delivered = bbr->rst->delivered; + } + } + + if (!bbr->loss_round_start) { + return; + } + + bbr_adapt_lower_bounds_from_congestion(bbr, cstat); + + bbr->loss_in_round = 0; +} + +static void bbr_adapt_lower_bounds_from_congestion(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + if (!bbr->filled_pipe || bbr_is_in_probe_bw_state(bbr)) { + return; + } + + if (bbr->loss_in_round) { + bbr_init_lower_bounds(bbr, cstat); + bbr_loss_lower_bounds(bbr); + } +} + +static void bbr_init_lower_bounds(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + if (bbr->bw_lo == UINT64_MAX) { + bbr->bw_lo = bbr->max_bw; + } + + if (bbr->inflight_lo == UINT64_MAX) { + bbr->inflight_lo = cstat->cwnd; + } +} + +static void bbr_loss_lower_bounds(ngtcp2_bbr2_cc *bbr) { + bbr->bw_lo = ngtcp2_max(bbr->bw_latest, bbr->bw_lo * NGTCP2_BBR_BETA_NUMER / + NGTCP2_BBR_BETA_DENOM); + bbr->inflight_lo = ngtcp2_max(bbr->inflight_latest, + bbr->inflight_lo * NGTCP2_BBR_BETA_NUMER / + NGTCP2_BBR_BETA_DENOM); +} + +static void bbr_bound_bw_for_model(ngtcp2_bbr2_cc *bbr) { + bbr->bw = ngtcp2_min(bbr->max_bw, bbr->bw_lo); + bbr->bw = ngtcp2_min(bbr->bw, bbr->bw_hi); +} + +static void bbr_update_max_bw(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack) { + bbr_update_round(bbr, ack); + bbr_handle_recovery(bbr, cstat, ack); + + if (cstat->delivery_rate_sec >= bbr->max_bw || !bbr->rst->rs.is_app_limited) { + ngtcp2_window_filter_update(&bbr->max_bw_filter, cstat->delivery_rate_sec, + bbr->cycle_count); + + bbr->max_bw = ngtcp2_window_filter_get_best(&bbr->max_bw_filter); + } +} + +static void bbr_update_round(ngtcp2_bbr2_cc *bbr, const ngtcp2_cc_ack *ack) { + if (ack->pkt_delivered >= bbr->next_round_delivered) { + bbr_start_round(bbr); + + ++bbr->round_count; + ++bbr->rounds_since_bw_probe; + bbr->round_start = 1; + + bbr->bytes_lost_in_round = 0; + bbr->loss_events_in_round = 0; + + bbr->rst->is_cwnd_limited = 0; + + return; + } + + bbr->round_start = 0; +} + +static void bbr_start_round(ngtcp2_bbr2_cc *bbr) { + bbr->next_round_delivered = bbr->rst->delivered; +} + +static int bbr_is_in_probe_bw_state(ngtcp2_bbr2_cc *bbr) { + switch (bbr->state) { + case NGTCP2_BBR2_STATE_PROBE_BW_DOWN: + case NGTCP2_BBR2_STATE_PROBE_BW_CRUISE: + case NGTCP2_BBR2_STATE_PROBE_BW_REFILL: + case NGTCP2_BBR2_STATE_PROBE_BW_UP: + return 1; + default: + return 0; + } +} + +static void bbr_update_ack_aggregation(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, + ngtcp2_tstamp ts) { + ngtcp2_duration interval = ts - bbr->extra_acked_interval_start; + uint64_t expected_delivered = bbr->bw * interval / NGTCP2_SECONDS; + uint64_t extra; + + if (bbr->extra_acked_delivered <= expected_delivered) { + bbr->extra_acked_delivered = 0; + bbr->extra_acked_interval_start = ts; + expected_delivered = 0; + } + + bbr->extra_acked_delivered += ack->bytes_delivered; + extra = bbr->extra_acked_delivered - expected_delivered; + extra = ngtcp2_min(extra, cstat->cwnd); + + ngtcp2_window_filter_update(&bbr->extra_acked_filter, extra, + bbr->round_count); + + bbr->extra_acked = ngtcp2_window_filter_get_best(&bbr->extra_acked_filter); +} + +static void bbr_enter_drain(ngtcp2_bbr2_cc *bbr) { + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, "bbr2 enter Drain"); + + bbr->state = NGTCP2_BBR2_STATE_DRAIN; + bbr->pacing_gain = 1. / NGTCP2_BBR_STARTUP_CWND_GAIN; + bbr->cwnd_gain = NGTCP2_BBR_STARTUP_CWND_GAIN; +} + +static void bbr_check_drain(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + if (bbr->state == NGTCP2_BBR2_STATE_DRAIN && + cstat->bytes_in_flight <= bbr_inflight(bbr, cstat, bbr->bw, 1.0)) { + bbr_enter_probe_bw(bbr, ts); + } +} + +static void bbr_enter_probe_bw(ngtcp2_bbr2_cc *bbr, ngtcp2_tstamp ts) { + bbr_start_probe_bw_down(bbr, ts); +} + +static void bbr_start_probe_bw_down(ngtcp2_bbr2_cc *bbr, ngtcp2_tstamp ts) { + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, + "bbr2 start ProbeBW_DOWN"); + + bbr_reset_congestion_signals(bbr); + + bbr->probe_up_cnt = UINT64_MAX; + + bbr_pick_probe_wait(bbr); + + bbr->cycle_stamp = ts; + bbr->ack_phase = NGTCP2_BBR2_ACK_PHASE_ACKS_PROBE_STOPPING; + + bbr_start_round(bbr); + + bbr->state = NGTCP2_BBR2_STATE_PROBE_BW_DOWN; + bbr->pacing_gain = 0.9; + bbr->cwnd_gain = 2; +} + +static void bbr_start_probe_bw_cruise(ngtcp2_bbr2_cc *bbr) { + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, + "bbr2 start ProbeBW_CRUISE"); + + bbr->state = NGTCP2_BBR2_STATE_PROBE_BW_CRUISE; + bbr->pacing_gain = 1.0; + bbr->cwnd_gain = 2; +} + +static void bbr_start_probe_bw_refill(ngtcp2_bbr2_cc *bbr) { + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, + "bbr2 start ProbeBW_REFILL"); + + bbr_reset_lower_bounds(bbr); + + bbr->bw_probe_up_rounds = 0; + bbr->bw_probe_up_acks = 0; + bbr->ack_phase = NGTCP2_BBR2_ACK_PHASE_ACKS_REFILLING; + + bbr_start_round(bbr); + + bbr->state = NGTCP2_BBR2_STATE_PROBE_BW_REFILL; + bbr->pacing_gain = 1.0; + bbr->cwnd_gain = 2; +} + +static void bbr_start_probe_bw_up(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, "bbr2 start ProbeBW_UP"); + + bbr->ack_phase = NGTCP2_BBR2_ACK_PHASE_ACKS_PROBE_STARTING; + + bbr_start_round(bbr); + + bbr->cycle_stamp = ts; + bbr->state = NGTCP2_BBR2_STATE_PROBE_BW_UP; + bbr->pacing_gain = 1.25; + bbr->cwnd_gain = 2; + + bbr_raise_inflight_hi_slope(bbr, cstat); +} + +static void bbr_update_probe_bw_cycle_phase(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, + ngtcp2_tstamp ts) { + if (!bbr->filled_pipe) { + return; + } + + bbr_adapt_upper_bounds(bbr, cstat, ack, ts); + + if (!bbr_is_in_probe_bw_state(bbr)) { + return; + } + + switch (bbr->state) { + case NGTCP2_BBR2_STATE_PROBE_BW_DOWN: + if (bbr_check_time_to_probe_bw(bbr, cstat, ts)) { + return; + } + + if (bbr_check_time_to_cruise(bbr, cstat, ts)) { + bbr_start_probe_bw_cruise(bbr); + } + + break; + case NGTCP2_BBR2_STATE_PROBE_BW_CRUISE: + if (bbr_check_time_to_probe_bw(bbr, cstat, ts)) { + return; + } + + break; + case NGTCP2_BBR2_STATE_PROBE_BW_REFILL: + if (bbr->round_start) { + bbr->bw_probe_samples = 1; + bbr_start_probe_bw_up(bbr, cstat, ts); + } + + break; + case NGTCP2_BBR2_STATE_PROBE_BW_UP: + if (bbr_has_elapsed_in_phase(bbr, bbr->min_rtt, ts) && + cstat->bytes_in_flight > bbr_inflight(bbr, cstat, bbr->max_bw, 1.25)) { + bbr_start_probe_bw_down(bbr, ts); + } + + break; + default: + break; + } +} + +static int bbr_check_time_to_cruise(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, ngtcp2_tstamp ts) { + (void)ts; + + if (cstat->bytes_in_flight > bbr_inflight_with_headroom(bbr, cstat)) { + return 0; + } + + if (cstat->bytes_in_flight <= bbr_inflight(bbr, cstat, bbr->max_bw, 1.0)) { + return 1; + } + + return 0; +} + +static int bbr_has_elapsed_in_phase(ngtcp2_bbr2_cc *bbr, + ngtcp2_duration interval, + ngtcp2_tstamp ts) { + return ts > bbr->cycle_stamp + interval; +} + +static uint64_t bbr_inflight_with_headroom(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t headroom; + uint64_t mpcwnd; + if (bbr->inflight_hi == UINT64_MAX) { + return UINT64_MAX; + } + + headroom = ngtcp2_max(cstat->max_tx_udp_payload_size, + bbr->inflight_hi * NGTCP2_BBR_HEADROOM_NUMER / + NGTCP2_BBR_HEADROOM_DENOM); + mpcwnd = min_pipe_cwnd(cstat->max_tx_udp_payload_size); + + if (bbr->inflight_hi > headroom) { + return ngtcp2_max(bbr->inflight_hi - headroom, mpcwnd); + } + + return mpcwnd; +} + +static void bbr_raise_inflight_hi_slope(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t growth_this_round = cstat->max_tx_udp_payload_size + << bbr->bw_probe_up_rounds; + + bbr->bw_probe_up_rounds = ngtcp2_min(bbr->bw_probe_up_rounds + 1, 30); + bbr->probe_up_cnt = ngtcp2_max(cstat->cwnd / growth_this_round, 1) * + cstat->max_tx_udp_payload_size; +} + +static void bbr_probe_inflight_hi_upward(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack) { + uint64_t delta; + + if (!bbr->rst->is_cwnd_limited || cstat->cwnd < bbr->inflight_hi) { + return; + } + + bbr->bw_probe_up_acks += ack->bytes_delivered; + + if (bbr->bw_probe_up_acks >= bbr->probe_up_cnt) { + delta = bbr->bw_probe_up_acks / bbr->probe_up_cnt; + bbr->bw_probe_up_acks -= delta * bbr->probe_up_cnt; + bbr->inflight_hi += delta * cstat->max_tx_udp_payload_size; + } + + if (bbr->round_start) { + bbr_raise_inflight_hi_slope(bbr, cstat); + } +} + +static void bbr_adapt_upper_bounds(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts) { + if (bbr->ack_phase == NGTCP2_BBR2_ACK_PHASE_ACKS_PROBE_STARTING && + bbr->round_start) { + bbr->ack_phase = NGTCP2_BBR2_ACK_PHASE_ACKS_PROBE_FEEDBACK; + } + + if (bbr->ack_phase == NGTCP2_BBR2_ACK_PHASE_ACKS_PROBE_STOPPING && + bbr->round_start) { + if (bbr_is_in_probe_bw_state(bbr) && !bbr->rst->rs.is_app_limited) { + bbr_advance_max_bw_filter(bbr); + } + } + + if (!bbr_check_inflight_too_high(bbr, cstat, ts)) { + /* bbr->bw_hi never be updated */ + if (bbr->inflight_hi == UINT64_MAX /* || bbr->bw_hi == UINT64_MAX */) { + return; + } + + if (bbr->rst->rs.tx_in_flight > bbr->inflight_hi) { + bbr->inflight_hi = bbr->rst->rs.tx_in_flight; + } + + if (cstat->delivery_rate_sec > bbr->bw_hi) { + bbr->bw_hi = cstat->delivery_rate_sec; + } + + if (bbr->state == NGTCP2_BBR2_STATE_PROBE_BW_UP) { + bbr_probe_inflight_hi_upward(bbr, cstat, ack); + } + } +} + +static int bbr_check_time_to_probe_bw(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + if (bbr_has_elapsed_in_phase(bbr, bbr->bw_probe_wait, ts) || + bbr_is_reno_coexistence_probe_time(bbr, cstat)) { + bbr_start_probe_bw_refill(bbr); + + return 1; + } + + return 0; +} + +static void bbr_pick_probe_wait(ngtcp2_bbr2_cc *bbr) { + uint8_t rand; + + bbr->rand(&rand, 1, &bbr->rand_ctx); + + bbr->rounds_since_bw_probe = (uint64_t)(rand * 2 / 256); + + bbr->rand(&rand, 1, &bbr->rand_ctx); + + bbr->bw_probe_wait = 2 * NGTCP2_SECONDS + + (ngtcp2_tstamp)((double)rand / 255. * NGTCP2_SECONDS); +} + +static int bbr_is_reno_coexistence_probe_time(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t reno_rounds = + bbr_target_inflight(bbr, cstat) / cstat->max_tx_udp_payload_size; + + return bbr->rounds_since_bw_probe >= ngtcp2_min(reno_rounds, 63); +} + +static uint64_t bbr_target_inflight(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t bdp = bbr_inflight(bbr, cstat, bbr->bw, 1.0); + + return ngtcp2_min(bdp, cstat->cwnd); +} + +static int bbr_check_inflight_too_high(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + if (is_inflight_too_high(&bbr->rst->rs)) { + if (bbr->bw_probe_samples) { + bbr_handle_inflight_too_high(bbr, cstat, &bbr->rst->rs, ts); + } + + return 1; + } + + return 0; +} + +static int is_inflight_too_high(const ngtcp2_rs *rs) { + return rs->lost * NGTCP2_BBR_LOSS_THRESH_DENOM > + rs->tx_in_flight * NGTCP2_BBR_LOSS_THRESH_NUMER; +} + +static void bbr_handle_inflight_too_high(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_rs *rs, + ngtcp2_tstamp ts) { + bbr->bw_probe_samples = 0; + + if (!rs->is_app_limited) { + bbr->prior_inflight_hi = bbr->inflight_hi; + + bbr->inflight_hi = ngtcp2_max( + rs->tx_in_flight, bbr_target_inflight(bbr, cstat) * + NGTCP2_BBR_BETA_NUMER / NGTCP2_BBR_BETA_DENOM); + } + + if (bbr->state == NGTCP2_BBR2_STATE_PROBE_BW_UP) { + bbr_start_probe_bw_down(bbr, ts); + } +} + +static void bbr_handle_lost_packet(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_pkt *pkt, ngtcp2_tstamp ts) { + ngtcp2_rs rs = {0}; + + if (!bbr->bw_probe_samples) { + return; + } + + rs.tx_in_flight = pkt->tx_in_flight; + /* bbr->rst->lost is not incremented for pkt yet */ + rs.lost = bbr->rst->lost + pkt->pktlen - pkt->lost; + rs.is_app_limited = pkt->is_app_limited; + + if (is_inflight_too_high(&rs)) { + rs.tx_in_flight = bbr_inflight_hi_from_lost_packet(bbr, &rs, pkt); + + bbr_handle_inflight_too_high(bbr, cstat, &rs, ts); + } +} + +static uint64_t bbr_inflight_hi_from_lost_packet(ngtcp2_bbr2_cc *bbr, + const ngtcp2_rs *rs, + const ngtcp2_cc_pkt *pkt) { + uint64_t inflight_prev, lost_prev, lost_prefix; + (void)bbr; + + assert(rs->tx_in_flight >= pkt->pktlen); + + inflight_prev = rs->tx_in_flight - pkt->pktlen; + + assert(rs->lost >= pkt->pktlen); + + lost_prev = rs->lost - pkt->pktlen; + + if (inflight_prev * NGTCP2_BBR_LOSS_THRESH_NUMER < + lost_prev * NGTCP2_BBR_LOSS_THRESH_DENOM) { + return inflight_prev; + } + + lost_prefix = (inflight_prev * NGTCP2_BBR_LOSS_THRESH_NUMER - + lost_prev * NGTCP2_BBR_LOSS_THRESH_DENOM) / + (NGTCP2_BBR_LOSS_THRESH_DENOM - NGTCP2_BBR_LOSS_THRESH_NUMER); + + return inflight_prev + lost_prefix; +} + +static void bbr_update_min_rtt(ngtcp2_bbr2_cc *bbr, const ngtcp2_cc_ack *ack, + ngtcp2_tstamp ts) { + int min_rtt_expired; + + bbr->probe_rtt_expired = + ts > bbr->probe_rtt_min_stamp + NGTCP2_BBR_PROBE_RTT_INTERVAL; + + if (ack->rtt != UINT64_MAX && + (ack->rtt < bbr->probe_rtt_min_delay || bbr->probe_rtt_expired)) { + bbr->probe_rtt_min_delay = ack->rtt; + bbr->probe_rtt_min_stamp = ts; + } + + min_rtt_expired = ts > bbr->min_rtt_stamp + NGTCP2_BBR_MIN_RTT_FILTERLEN; + + if (bbr->probe_rtt_min_delay < bbr->min_rtt || min_rtt_expired) { + bbr->min_rtt = bbr->probe_rtt_min_delay; + bbr->min_rtt_stamp = bbr->probe_rtt_min_stamp; + + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, + "bbr2 update min_rtt=%" PRIu64, bbr->min_rtt); + } +} + +static void bbr_check_probe_rtt(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + if (bbr->state != NGTCP2_BBR2_STATE_PROBE_RTT && bbr->probe_rtt_expired && + !bbr->idle_restart) { + bbr_enter_probe_rtt(bbr); + bbr_save_cwnd(bbr, cstat); + + bbr->probe_rtt_done_stamp = UINT64_MAX; + bbr->ack_phase = NGTCP2_BBR2_ACK_PHASE_ACKS_PROBE_STOPPING; + + bbr_start_round(bbr); + } + + if (bbr->state == NGTCP2_BBR2_STATE_PROBE_RTT) { + bbr_handle_probe_rtt(bbr, cstat, ts); + } + + if (bbr->rst->rs.delivered) { + bbr->idle_restart = 0; + } +} + +static void bbr_enter_probe_rtt(ngtcp2_bbr2_cc *bbr) { + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, "bbr2 enter ProbeRTT"); + + bbr->state = NGTCP2_BBR2_STATE_PROBE_RTT; + bbr->pacing_gain = 1; + bbr->cwnd_gain = NGTCP2_BBR_PROBE_RTT_CWND_GAIN; +} + +static void bbr_handle_probe_rtt(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + bbr_mark_connection_app_limited(bbr, cstat); + + if (bbr->probe_rtt_done_stamp == UINT64_MAX && + cstat->bytes_in_flight <= bbr_probe_rtt_cwnd(bbr, cstat)) { + bbr->probe_rtt_done_stamp = ts + NGTCP2_BBR_PROBE_RTT_DURATION; + bbr->probe_rtt_round_done = 0; + + bbr_start_round(bbr); + + return; + } + + if (bbr->probe_rtt_done_stamp != UINT64_MAX) { + if (bbr->round_start) { + bbr->probe_rtt_round_done = 1; + } + + if (bbr->probe_rtt_round_done) { + bbr_check_probe_rtt_done(bbr, cstat, ts); + } + } +} + +static void bbr_check_probe_rtt_done(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + if (bbr->probe_rtt_done_stamp != UINT64_MAX && + ts > bbr->probe_rtt_done_stamp) { + bbr->probe_rtt_min_stamp = ts; + bbr_restore_cwnd(bbr, cstat); + bbr_exit_probe_rtt(bbr, ts); + } +} + +static void bbr_mark_connection_app_limited(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t app_limited = bbr->rst->delivered + cstat->bytes_in_flight; + + if (app_limited) { + bbr->rst->app_limited = app_limited; + } else { + bbr->rst->app_limited = cstat->max_tx_udp_payload_size; + } +} + +static void bbr_exit_probe_rtt(ngtcp2_bbr2_cc *bbr, ngtcp2_tstamp ts) { + bbr_reset_lower_bounds(bbr); + + if (bbr->filled_pipe) { + bbr_start_probe_bw_down(bbr, ts); + bbr_start_probe_bw_cruise(bbr); + } else { + bbr_enter_startup(bbr); + } +} + +static void bbr_handle_restart_from_idle(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + if (cstat->bytes_in_flight == 0 && bbr->rst->app_limited) { + ngtcp2_log_info(bbr->ccb.log, NGTCP2_LOG_EVENT_RCV, + "bbr2 restart from idle"); + + bbr->idle_restart = 1; + bbr->extra_acked_interval_start = ts; + + if (bbr_is_in_probe_bw_state(bbr)) { + bbr_set_pacing_rate_with_gain(bbr, cstat, 1); + } else if (bbr->state == NGTCP2_BBR2_STATE_PROBE_RTT) { + bbr_check_probe_rtt_done(bbr, cstat, ts); + } + } +} + +static uint64_t bbr_bdp_multiple(ngtcp2_bbr2_cc *bbr, uint64_t bw, + double gain) { + uint64_t bdp; + + if (bbr->min_rtt == UINT64_MAX) { + return bbr->initial_cwnd; + } + + bdp = bw * bbr->min_rtt / NGTCP2_SECONDS; + + return (uint64_t)(gain * (double)bdp); +} + +static uint64_t min_pipe_cwnd(size_t max_udp_payload_size) { + return max_udp_payload_size * 4; +} + +static uint64_t bbr_quantization_budget(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + uint64_t inflight) { + bbr_update_offload_budget(bbr, cstat); + + inflight = ngtcp2_max(inflight, bbr->offload_budget); + inflight = + ngtcp2_max(inflight, min_pipe_cwnd(cstat->max_tx_udp_payload_size)); + + if (bbr->state == NGTCP2_BBR2_STATE_PROBE_BW_UP) { + inflight += 2 * cstat->max_tx_udp_payload_size; + } + + return inflight; +} + +static uint64_t bbr_inflight(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + uint64_t bw, double gain) { + uint64_t inflight = bbr_bdp_multiple(bbr, bw, gain); + + return bbr_quantization_budget(bbr, cstat, inflight); +} + +static void bbr_update_max_inflight(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t inflight; + + /* Not documented */ + /* bbr_update_aggregation_budget(bbr); */ + + inflight = bbr_bdp_multiple(bbr, bbr->bw, bbr->cwnd_gain) + bbr->extra_acked; + bbr->max_inflight = bbr_quantization_budget(bbr, cstat, inflight); +} + +static void bbr_update_offload_budget(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + bbr->offload_budget = 3 * cstat->send_quantum; +} + +static void bbr_advance_max_bw_filter(ngtcp2_bbr2_cc *bbr) { + ++bbr->cycle_count; +} + +static void bbr_modulate_cwnd_for_recovery(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack) { + if (ack->bytes_lost > 0) { + if (cstat->cwnd > ack->bytes_lost) { + cstat->cwnd -= ack->bytes_lost; + cstat->cwnd = ngtcp2_max(cstat->cwnd, 2 * cstat->max_tx_udp_payload_size); + } else { + cstat->cwnd = 2 * cstat->max_tx_udp_payload_size; + } + } + + if (bbr->packet_conservation) { + cstat->cwnd = + ngtcp2_max(cstat->cwnd, cstat->bytes_in_flight + ack->bytes_delivered); + } +} + +static void bbr_save_cwnd(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat) { + if (!bbr->in_loss_recovery && bbr->state != NGTCP2_BBR2_STATE_PROBE_RTT) { + bbr->prior_cwnd = cstat->cwnd; + return; + } + + bbr->prior_cwnd = ngtcp2_max(bbr->prior_cwnd, cstat->cwnd); +} + +static void bbr_restore_cwnd(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat) { + cstat->cwnd = ngtcp2_max(cstat->cwnd, bbr->prior_cwnd); +} + +static uint64_t bbr_probe_rtt_cwnd(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t probe_rtt_cwnd = + bbr_bdp_multiple(bbr, bbr->bw, NGTCP2_BBR_PROBE_RTT_CWND_GAIN); + uint64_t mpcwnd = min_pipe_cwnd(cstat->max_tx_udp_payload_size); + + return ngtcp2_max(probe_rtt_cwnd, mpcwnd); +} + +static void bbr_bound_cwnd_for_probe_rtt(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t probe_rtt_cwnd; + + if (bbr->state == NGTCP2_BBR2_STATE_PROBE_RTT) { + probe_rtt_cwnd = bbr_probe_rtt_cwnd(bbr, cstat); + + cstat->cwnd = ngtcp2_min(cstat->cwnd, probe_rtt_cwnd); + } +} + +static void bbr_set_cwnd(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack) { + uint64_t mpcwnd; + + bbr_update_max_inflight(bbr, cstat); + bbr_modulate_cwnd_for_recovery(bbr, cstat, ack); + + if (!bbr->packet_conservation) { + if (bbr->filled_pipe) { + cstat->cwnd += ack->bytes_delivered; + cstat->cwnd = ngtcp2_min(cstat->cwnd, bbr->max_inflight); + } else if (cstat->cwnd < bbr->max_inflight || + bbr->rst->delivered < bbr->initial_cwnd) { + cstat->cwnd += ack->bytes_delivered; + } + + mpcwnd = min_pipe_cwnd(cstat->max_tx_udp_payload_size); + cstat->cwnd = ngtcp2_max(cstat->cwnd, mpcwnd); + } + + bbr_bound_cwnd_for_probe_rtt(bbr, cstat); + bbr_bound_cwnd_for_model(bbr, cstat); +} + +static void bbr_bound_cwnd_for_model(ngtcp2_bbr2_cc *bbr, + ngtcp2_conn_stat *cstat) { + uint64_t cap = UINT64_MAX; + uint64_t mpcwnd = min_pipe_cwnd(cstat->max_tx_udp_payload_size); + + if (bbr_is_in_probe_bw_state(bbr) && + bbr->state != NGTCP2_BBR2_STATE_PROBE_BW_CRUISE) { + cap = bbr->inflight_hi; + } else if (bbr->state == NGTCP2_BBR2_STATE_PROBE_RTT || + bbr->state == NGTCP2_BBR2_STATE_PROBE_BW_CRUISE) { + cap = bbr_inflight_with_headroom(bbr, cstat); + } + + cap = ngtcp2_min(cap, bbr->inflight_lo); + cap = ngtcp2_max(cap, mpcwnd); + + cstat->cwnd = ngtcp2_min(cstat->cwnd, cap); +} + +static void bbr_set_send_quantum(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat) { + size_t send_quantum = + (size_t)(cstat->pacing_rate * (double)(bbr->min_rtt == UINT64_MAX + ? NGTCP2_MILLISECONDS + : bbr->min_rtt)); + (void)bbr; + + cstat->send_quantum = ngtcp2_min(send_quantum, 64 * 1024); + cstat->send_quantum = + ngtcp2_max(cstat->send_quantum, cstat->max_tx_udp_payload_size * 10); +} + +static int in_congestion_recovery(const ngtcp2_conn_stat *cstat, + ngtcp2_tstamp sent_time) { + return cstat->congestion_recovery_start_ts != UINT64_MAX && + sent_time <= cstat->congestion_recovery_start_ts; +} + +static void bbr_handle_recovery(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack) { + if (bbr->in_loss_recovery) { + if (ack->pkt_delivered >= bbr->congestion_recovery_next_round_delivered) { + bbr->packet_conservation = 0; + } + + if (!in_congestion_recovery(cstat, ack->largest_acked_sent_ts)) { + bbr->in_loss_recovery = 0; + bbr->packet_conservation = 0; + bbr_restore_cwnd(bbr, cstat); + } + + return; + } + + if (bbr->congestion_recovery_start_ts != UINT64_MAX) { + bbr->in_loss_recovery = 1; + bbr_save_cwnd(bbr, cstat); + cstat->cwnd = + cstat->bytes_in_flight + + ngtcp2_max(ack->bytes_delivered, cstat->max_tx_udp_payload_size); + + cstat->congestion_recovery_start_ts = bbr->congestion_recovery_start_ts; + bbr->congestion_recovery_start_ts = UINT64_MAX; + bbr->packet_conservation = 1; + bbr->congestion_recovery_next_round_delivered = bbr->rst->delivered; + bbr->prior_inflight_lo = bbr->inflight_lo; + bbr->prior_bw_lo = bbr->bw_lo; + } +} + +static void bbr2_cc_init(ngtcp2_bbr2_cc *bbr, ngtcp2_conn_stat *cstat, + ngtcp2_rst *rst, ngtcp2_tstamp initial_ts, + ngtcp2_rand rand, const ngtcp2_rand_ctx *rand_ctx, + ngtcp2_log *log) { + bbr->ccb.log = log; + bbr->rst = rst; + bbr->rand = rand; + bbr->rand_ctx = *rand_ctx; + bbr->initial_cwnd = cstat->cwnd; + + bbr_on_init(bbr, cstat, initial_ts); +} + +static void bbr2_cc_free(ngtcp2_bbr2_cc *bbr) { (void)bbr; } + +static void bbr2_cc_on_pkt_acked(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_pkt *pkt, ngtcp2_tstamp ts) { + (void)ccx; + (void)cstat; + (void)pkt; + (void)ts; +} + +static void bbr2_cc_on_pkt_lost(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_pkt *pkt, ngtcp2_tstamp ts) { + ngtcp2_bbr2_cc *bbr = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr2_cc, ccb); + + bbr_update_on_loss(bbr, cstat, pkt, ts); +} + +static void bbr2_cc_congestion_event(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp sent_ts, ngtcp2_tstamp ts) { + ngtcp2_bbr2_cc *bbr = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr2_cc, ccb); + + if (!bbr->filled_pipe || bbr->in_loss_recovery || + bbr->congestion_recovery_start_ts != UINT64_MAX || + in_congestion_recovery(cstat, sent_ts)) { + return; + } + + bbr->congestion_recovery_start_ts = ts; +} + +static void bbr2_cc_on_spurious_congestion(ngtcp2_cc *ccx, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + ngtcp2_bbr2_cc *bbr = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr2_cc, ccb); + (void)ts; + + bbr->congestion_recovery_start_ts = UINT64_MAX; + cstat->congestion_recovery_start_ts = UINT64_MAX; + + if (bbr->in_loss_recovery) { + bbr->in_loss_recovery = 0; + bbr->packet_conservation = 0; + bbr_restore_cwnd(bbr, cstat); + bbr->full_bw_count = 0; + bbr->loss_in_round = 0; + bbr->inflight_lo = ngtcp2_max(bbr->inflight_lo, bbr->prior_inflight_lo); + bbr->inflight_hi = ngtcp2_max(bbr->inflight_hi, bbr->prior_inflight_hi); + bbr->bw_lo = ngtcp2_max(bbr->bw_lo, bbr->prior_bw_lo); + } +} + +static void bbr2_cc_on_persistent_congestion(ngtcp2_cc *ccx, + ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + ngtcp2_bbr2_cc *bbr = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr2_cc, ccb); + (void)ts; + + cstat->congestion_recovery_start_ts = UINT64_MAX; + bbr->congestion_recovery_start_ts = UINT64_MAX; + bbr->in_loss_recovery = 0; + bbr->packet_conservation = 0; + + bbr_save_cwnd(bbr, cstat); + cstat->cwnd = cstat->bytes_in_flight + cstat->max_tx_udp_payload_size; + cstat->cwnd = + ngtcp2_max(cstat->cwnd, min_pipe_cwnd(cstat->max_tx_udp_payload_size)); +} + +static void bbr2_cc_on_ack_recv(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts) { + ngtcp2_bbr2_cc *bbr = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr2_cc, ccb); + + bbr_update_on_ack(bbr, cstat, ack, ts); +} + +static void bbr2_cc_on_pkt_sent(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat, + const ngtcp2_cc_pkt *pkt) { + ngtcp2_bbr2_cc *bbr = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr2_cc, ccb); + + bbr_on_transmit(bbr, cstat, pkt->sent_ts); +} + +static void bbr2_cc_new_rtt_sample(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + (void)ccx; + (void)cstat; + (void)ts; +} + +static void bbr2_cc_reset(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat, + ngtcp2_tstamp ts) { + ngtcp2_bbr2_cc *bbr = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr2_cc, ccb); + + bbr_on_init(bbr, cstat, ts); +} + +static void bbr2_cc_event(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat, + ngtcp2_cc_event_type event, ngtcp2_tstamp ts) { + (void)ccx; + (void)cstat; + (void)event; + (void)ts; +} + +int ngtcp2_cc_bbr2_cc_init(ngtcp2_cc *cc, ngtcp2_log *log, + ngtcp2_conn_stat *cstat, ngtcp2_rst *rst, + ngtcp2_tstamp initial_ts, ngtcp2_rand rand, + const ngtcp2_rand_ctx *rand_ctx, + const ngtcp2_mem *mem) { + ngtcp2_bbr2_cc *bbr; + + bbr = ngtcp2_mem_calloc(mem, 1, sizeof(ngtcp2_bbr2_cc)); + if (bbr == NULL) { + return NGTCP2_ERR_NOMEM; + } + + bbr2_cc_init(bbr, cstat, rst, initial_ts, rand, rand_ctx, log); + + cc->ccb = &bbr->ccb; + cc->on_pkt_acked = bbr2_cc_on_pkt_acked; + cc->on_pkt_lost = bbr2_cc_on_pkt_lost; + cc->congestion_event = bbr2_cc_congestion_event; + cc->on_spurious_congestion = bbr2_cc_on_spurious_congestion; + cc->on_persistent_congestion = bbr2_cc_on_persistent_congestion; + cc->on_ack_recv = bbr2_cc_on_ack_recv; + cc->on_pkt_sent = bbr2_cc_on_pkt_sent; + cc->new_rtt_sample = bbr2_cc_new_rtt_sample; + cc->reset = bbr2_cc_reset; + cc->event = bbr2_cc_event; + + return 0; +} + +void ngtcp2_cc_bbr2_cc_free(ngtcp2_cc *cc, const ngtcp2_mem *mem) { + ngtcp2_bbr2_cc *bbr = ngtcp2_struct_of(cc->ccb, ngtcp2_bbr2_cc, ccb); + + bbr2_cc_free(bbr); + ngtcp2_mem_free(mem, bbr); +} |