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-rw-r--r--lib/ngtcp2_bbr.c692
1 files changed, 692 insertions, 0 deletions
diff --git a/lib/ngtcp2_bbr.c b/lib/ngtcp2_bbr.c
new file mode 100644
index 0000000..ed26d3e
--- /dev/null
+++ b/lib/ngtcp2_bbr.c
@@ -0,0 +1,692 @@
+/*
+ * 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_bbr.h"
+
+#include <assert.h>
+
+#include "ngtcp2_log.h"
+#include "ngtcp2_macro.h"
+#include "ngtcp2_mem.h"
+#include "ngtcp2_rcvry.h"
+#include "ngtcp2_rst.h"
+
+static const double pacing_gain_cycle[] = {1.25, 0.75, 1, 1, 1, 1, 1, 1};
+
+#define NGTCP2_BBR_GAIN_CYCLELEN ngtcp2_arraylen(pacing_gain_cycle)
+
+#define NGTCP2_BBR_HIGH_GAIN 2.89
+#define NGTCP2_BBR_PROBE_RTT_DURATION (200 * NGTCP2_MILLISECONDS)
+#define NGTCP2_RTPROP_FILTERLEN (10 * NGTCP2_SECONDS)
+#define NGTCP2_BBR_BTL_BW_FILTERLEN 10
+
+static void bbr_update_on_ack(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts);
+static void bbr_update_model_and_state(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack,
+ ngtcp2_tstamp ts);
+static void bbr_update_control_parameters(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack);
+static void bbr_on_transmit(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat);
+static void bbr_init_round_counting(ngtcp2_bbr_cc *cc);
+static void bbr_update_round(ngtcp2_bbr_cc *cc, const ngtcp2_cc_ack *ack);
+static void bbr_update_btl_bw(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack);
+static void bbr_update_rtprop(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts);
+static void bbr_init_pacing_rate(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat);
+static void bbr_set_pacing_rate_with_gain(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat,
+ double pacing_gain);
+static void bbr_set_pacing_rate(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat);
+static void bbr_set_send_quantum(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat);
+static void bbr_update_target_cwnd(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat);
+static void bbr_modulate_cwnd_for_recovery(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack);
+static void bbr_save_cwnd(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat);
+static void bbr_restore_cwnd(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat);
+static void bbr_modulate_cwnd_for_probe_rtt(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat);
+static void bbr_set_cwnd(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack);
+static void bbr_init(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp initial_ts);
+static void bbr_enter_startup(ngtcp2_bbr_cc *cc);
+static void bbr_init_full_pipe(ngtcp2_bbr_cc *cc);
+static void bbr_check_full_pipe(ngtcp2_bbr_cc *cc);
+static void bbr_enter_drain(ngtcp2_bbr_cc *cc);
+static void bbr_check_drain(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts);
+static void bbr_enter_probe_bw(ngtcp2_bbr_cc *cc, ngtcp2_tstamp ts);
+static void bbr_check_cycle_phase(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts);
+static void bbr_advance_cycle_phase(ngtcp2_bbr_cc *cc, ngtcp2_tstamp ts);
+static int bbr_is_next_cycle_phase(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts);
+static void bbr_handle_restart_from_idle(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat);
+static void bbr_check_probe_rtt(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts);
+static void bbr_enter_probe_rtt(ngtcp2_bbr_cc *cc);
+static void bbr_handle_probe_rtt(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts);
+static void bbr_exit_probe_rtt(ngtcp2_bbr_cc *cc, ngtcp2_tstamp ts);
+
+void ngtcp2_bbr_cc_init(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_rst *rst, ngtcp2_tstamp initial_ts,
+ ngtcp2_rand rand, const ngtcp2_rand_ctx *rand_ctx,
+ ngtcp2_log *log) {
+ cc->ccb.log = log;
+ cc->rst = rst;
+ cc->rand = rand;
+ cc->rand_ctx = *rand_ctx;
+ cc->initial_cwnd = cstat->cwnd;
+ bbr_init(cc, cstat, initial_ts);
+}
+
+void ngtcp2_bbr_cc_free(ngtcp2_bbr_cc *cc) { (void)cc; }
+
+int ngtcp2_cc_bbr_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_bbr_cc *bbr_cc;
+
+ bbr_cc = ngtcp2_mem_calloc(mem, 1, sizeof(ngtcp2_bbr_cc));
+ if (bbr_cc == NULL) {
+ return NGTCP2_ERR_NOMEM;
+ }
+
+ ngtcp2_bbr_cc_init(bbr_cc, cstat, rst, initial_ts, rand, rand_ctx, log);
+
+ cc->ccb = &bbr_cc->ccb;
+ cc->on_pkt_acked = ngtcp2_cc_bbr_cc_on_pkt_acked;
+ cc->congestion_event = ngtcp2_cc_bbr_cc_congestion_event;
+ cc->on_spurious_congestion = ngtcp2_cc_bbr_cc_on_spurious_congestion;
+ cc->on_persistent_congestion = ngtcp2_cc_bbr_cc_on_persistent_congestion;
+ cc->on_ack_recv = ngtcp2_cc_bbr_cc_on_ack_recv;
+ cc->on_pkt_sent = ngtcp2_cc_bbr_cc_on_pkt_sent;
+ cc->new_rtt_sample = ngtcp2_cc_bbr_cc_new_rtt_sample;
+ cc->reset = ngtcp2_cc_bbr_cc_reset;
+ cc->event = ngtcp2_cc_bbr_cc_event;
+
+ return 0;
+}
+
+void ngtcp2_cc_bbr_cc_free(ngtcp2_cc *cc, const ngtcp2_mem *mem) {
+ ngtcp2_bbr_cc *bbr_cc = ngtcp2_struct_of(cc->ccb, ngtcp2_bbr_cc, ccb);
+
+ ngtcp2_bbr_cc_free(bbr_cc);
+ ngtcp2_mem_free(mem, bbr_cc);
+}
+
+void ngtcp2_cc_bbr_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 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;
+}
+
+void ngtcp2_cc_bbr_cc_congestion_event(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp sent_ts,
+ ngtcp2_tstamp ts) {
+ ngtcp2_bbr_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr_cc, ccb);
+
+ if (cc->in_loss_recovery || cc->congestion_recovery_start_ts != UINT64_MAX ||
+ in_congestion_recovery(cstat, sent_ts)) {
+ return;
+ }
+
+ cc->congestion_recovery_start_ts = ts;
+}
+
+void ngtcp2_cc_bbr_cc_on_spurious_congestion(ngtcp2_cc *ccx,
+ ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts) {
+ ngtcp2_bbr_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr_cc, ccb);
+ (void)ts;
+
+ cc->congestion_recovery_start_ts = UINT64_MAX;
+ cstat->congestion_recovery_start_ts = UINT64_MAX;
+
+ if (cc->in_loss_recovery) {
+ cc->in_loss_recovery = 0;
+ cc->packet_conservation = 0;
+ bbr_restore_cwnd(cc, cstat);
+ }
+}
+
+void ngtcp2_cc_bbr_cc_on_persistent_congestion(ngtcp2_cc *ccx,
+ ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts) {
+ ngtcp2_bbr_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr_cc, ccb);
+ (void)ts;
+
+ cstat->congestion_recovery_start_ts = UINT64_MAX;
+ cc->congestion_recovery_start_ts = UINT64_MAX;
+ cc->in_loss_recovery = 0;
+ cc->packet_conservation = 0;
+
+ bbr_save_cwnd(cc, cstat);
+ cstat->cwnd = 2 * cstat->max_tx_udp_payload_size;
+}
+
+void ngtcp2_cc_bbr_cc_on_ack_recv(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts) {
+ ngtcp2_bbr_cc *bbr_cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr_cc, ccb);
+
+ bbr_update_on_ack(bbr_cc, cstat, ack, ts);
+}
+
+void ngtcp2_cc_bbr_cc_on_pkt_sent(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_pkt *pkt) {
+ ngtcp2_bbr_cc *bbr_cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr_cc, ccb);
+ (void)pkt;
+
+ bbr_on_transmit(bbr_cc, cstat);
+}
+
+void ngtcp2_cc_bbr_cc_new_rtt_sample(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts) {
+ (void)ccx;
+ (void)cstat;
+ (void)ts;
+}
+
+void ngtcp2_cc_bbr_cc_reset(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts) {
+ ngtcp2_bbr_cc *bbr_cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_bbr_cc, ccb);
+ bbr_init(bbr_cc, cstat, ts);
+}
+
+void ngtcp2_cc_bbr_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;
+}
+
+static void bbr_update_on_ack(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts) {
+ bbr_update_model_and_state(cc, cstat, ack, ts);
+ bbr_update_control_parameters(cc, cstat, ack);
+}
+
+static void bbr_update_model_and_state(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack,
+ ngtcp2_tstamp ts) {
+ bbr_update_btl_bw(cc, cstat, ack);
+ bbr_check_cycle_phase(cc, cstat, ack, ts);
+ bbr_check_full_pipe(cc);
+ bbr_check_drain(cc, cstat, ts);
+ bbr_update_rtprop(cc, cstat, ts);
+ bbr_check_probe_rtt(cc, cstat, ts);
+}
+
+static void bbr_update_control_parameters(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack) {
+ bbr_set_pacing_rate(cc, cstat);
+ bbr_set_send_quantum(cc, cstat);
+ bbr_set_cwnd(cc, cstat, ack);
+}
+
+static void bbr_on_transmit(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat) {
+ bbr_handle_restart_from_idle(cc, cstat);
+}
+
+static void bbr_init_round_counting(ngtcp2_bbr_cc *cc) {
+ cc->next_round_delivered = 0;
+ cc->round_start = 0;
+ cc->round_count = 0;
+}
+
+static void bbr_update_round(ngtcp2_bbr_cc *cc, const ngtcp2_cc_ack *ack) {
+ if (ack->pkt_delivered >= cc->next_round_delivered) {
+ cc->next_round_delivered = cc->rst->delivered;
+ ++cc->round_count;
+ cc->round_start = 1;
+
+ return;
+ }
+
+ cc->round_start = 0;
+}
+
+static void bbr_handle_recovery(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack) {
+ if (cc->in_loss_recovery) {
+ if (ack->pkt_delivered >= cc->congestion_recovery_next_round_delivered) {
+ cc->packet_conservation = 0;
+ }
+
+ if (!in_congestion_recovery(cstat, ack->largest_acked_sent_ts)) {
+ cc->in_loss_recovery = 0;
+ cc->packet_conservation = 0;
+ bbr_restore_cwnd(cc, cstat);
+ }
+
+ return;
+ }
+
+ if (cc->congestion_recovery_start_ts != UINT64_MAX) {
+ cc->in_loss_recovery = 1;
+ bbr_save_cwnd(cc, cstat);
+ cstat->cwnd =
+ cstat->bytes_in_flight +
+ ngtcp2_max(ack->bytes_delivered, cstat->max_tx_udp_payload_size);
+
+ cstat->congestion_recovery_start_ts = cc->congestion_recovery_start_ts;
+ cc->congestion_recovery_start_ts = UINT64_MAX;
+ cc->packet_conservation = 1;
+ cc->congestion_recovery_next_round_delivered = cc->rst->delivered;
+ }
+}
+
+static void bbr_update_btl_bw(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack) {
+ bbr_update_round(cc, ack);
+ bbr_handle_recovery(cc, cstat, ack);
+
+ if (cstat->delivery_rate_sec < cc->btl_bw && cc->rst->rs.is_app_limited) {
+ return;
+ }
+
+ ngtcp2_window_filter_update(&cc->btl_bw_filter, cstat->delivery_rate_sec,
+ cc->round_count);
+
+ cc->btl_bw = ngtcp2_window_filter_get_best(&cc->btl_bw_filter);
+}
+
+static void bbr_update_rtprop(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts) {
+ cc->rtprop_expired = ts > cc->rtprop_stamp + NGTCP2_RTPROP_FILTERLEN;
+
+ /* Need valid RTT sample */
+ if (cstat->latest_rtt &&
+ (cstat->latest_rtt <= cc->rt_prop || cc->rtprop_expired)) {
+ cc->rt_prop = cstat->latest_rtt;
+ cc->rtprop_stamp = ts;
+
+ ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+ "bbr update RTprop=%" PRIu64, cc->rt_prop);
+ }
+}
+
+static void bbr_init_pacing_rate(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat) {
+ double nominal_bandwidth =
+ (double)cc->initial_cwnd / (double)NGTCP2_MILLISECONDS;
+
+ cstat->pacing_rate = cc->pacing_gain * nominal_bandwidth;
+}
+
+static void bbr_set_pacing_rate_with_gain(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat,
+ double pacing_gain) {
+ double rate = pacing_gain * (double)cc->btl_bw / NGTCP2_SECONDS;
+
+ if (cc->filled_pipe || rate > cstat->pacing_rate) {
+ cstat->pacing_rate = rate;
+ }
+}
+
+static void bbr_set_pacing_rate(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat) {
+ bbr_set_pacing_rate_with_gain(cc, cstat, cc->pacing_gain);
+}
+
+static void bbr_set_send_quantum(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat) {
+ uint64_t send_quantum;
+ (void)cc;
+
+ if (cstat->pacing_rate < 1.2 * 1024 * 1024 / 8 / NGTCP2_SECONDS) {
+ cstat->send_quantum = cstat->max_tx_udp_payload_size;
+ } else if (cstat->pacing_rate < 24.0 * 1024 * 1024 / 8 / NGTCP2_SECONDS) {
+ cstat->send_quantum = cstat->max_tx_udp_payload_size * 2;
+ } else {
+ send_quantum =
+ (uint64_t)(cstat->pacing_rate * (double)(cstat->min_rtt == UINT64_MAX
+ ? NGTCP2_MILLISECONDS
+ : cstat->min_rtt));
+ cstat->send_quantum = (size_t)ngtcp2_min(send_quantum, 64 * 1024);
+ }
+
+ cstat->send_quantum =
+ ngtcp2_max(cstat->send_quantum, cstat->max_tx_udp_payload_size * 10);
+}
+
+static uint64_t bbr_inflight(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ double gain) {
+ uint64_t quanta = 3 * cstat->send_quantum;
+ double estimated_bdp;
+
+ if (cc->rt_prop == UINT64_MAX) {
+ /* no valid RTT samples yet */
+ return cc->initial_cwnd;
+ }
+
+ estimated_bdp = (double)cc->btl_bw * (double)cc->rt_prop / NGTCP2_SECONDS;
+
+ return (uint64_t)(gain * estimated_bdp) + quanta;
+}
+
+static void bbr_update_target_cwnd(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat) {
+ cc->target_cwnd = bbr_inflight(cc, cstat, cc->cwnd_gain);
+}
+
+static void bbr_modulate_cwnd_for_recovery(ngtcp2_bbr_cc *cc,
+ 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 (cc->packet_conservation) {
+ cstat->cwnd =
+ ngtcp2_max(cstat->cwnd, cstat->bytes_in_flight + ack->bytes_delivered);
+ }
+}
+
+static void bbr_save_cwnd(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat) {
+ if (!cc->in_loss_recovery && cc->state != NGTCP2_BBR_STATE_PROBE_RTT) {
+ cc->prior_cwnd = cstat->cwnd;
+ return;
+ }
+
+ cc->prior_cwnd = ngtcp2_max(cc->prior_cwnd, cstat->cwnd);
+}
+
+static void bbr_restore_cwnd(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat) {
+ cstat->cwnd = ngtcp2_max(cstat->cwnd, cc->prior_cwnd);
+}
+
+static uint64_t min_pipe_cwnd(size_t max_udp_payload_size) {
+ return max_udp_payload_size * 4;
+}
+
+static void bbr_modulate_cwnd_for_probe_rtt(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat) {
+ if (cc->state == NGTCP2_BBR_STATE_PROBE_RTT) {
+ cstat->cwnd =
+ ngtcp2_min(cstat->cwnd, min_pipe_cwnd(cstat->max_tx_udp_payload_size));
+ }
+}
+
+static void bbr_set_cwnd(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack) {
+ bbr_update_target_cwnd(cc, cstat);
+ bbr_modulate_cwnd_for_recovery(cc, cstat, ack);
+
+ if (!cc->packet_conservation) {
+ if (cc->filled_pipe) {
+ cstat->cwnd =
+ ngtcp2_min(cstat->cwnd + ack->bytes_delivered, cc->target_cwnd);
+ } else if (cstat->cwnd < cc->target_cwnd ||
+ cc->rst->delivered < cc->initial_cwnd) {
+ cstat->cwnd += ack->bytes_delivered;
+ }
+
+ cstat->cwnd =
+ ngtcp2_max(cstat->cwnd, min_pipe_cwnd(cstat->max_tx_udp_payload_size));
+ }
+
+ bbr_modulate_cwnd_for_probe_rtt(cc, cstat);
+}
+
+static void bbr_init(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp initial_ts) {
+ cc->pacing_gain = NGTCP2_BBR_HIGH_GAIN;
+ cc->prior_cwnd = 0;
+ cc->target_cwnd = 0;
+ cc->btl_bw = 0;
+ cc->rt_prop = UINT64_MAX;
+ cc->rtprop_stamp = initial_ts;
+ cc->cycle_stamp = UINT64_MAX;
+ cc->probe_rtt_done_stamp = UINT64_MAX;
+ cc->cycle_index = 0;
+ cc->rtprop_expired = 0;
+ cc->idle_restart = 0;
+ cc->packet_conservation = 0;
+ cc->probe_rtt_round_done = 0;
+
+ cc->congestion_recovery_start_ts = UINT64_MAX;
+ cc->congestion_recovery_next_round_delivered = 0;
+ cc->in_loss_recovery = 0;
+
+ cstat->send_quantum = cstat->max_tx_udp_payload_size * 10;
+
+ ngtcp2_window_filter_init(&cc->btl_bw_filter, NGTCP2_BBR_BTL_BW_FILTERLEN);
+
+ bbr_init_round_counting(cc);
+ bbr_init_full_pipe(cc);
+ bbr_init_pacing_rate(cc, cstat);
+ bbr_enter_startup(cc);
+}
+
+static void bbr_enter_startup(ngtcp2_bbr_cc *cc) {
+ cc->state = NGTCP2_BBR_STATE_STARTUP;
+ cc->pacing_gain = NGTCP2_BBR_HIGH_GAIN;
+ cc->cwnd_gain = NGTCP2_BBR_HIGH_GAIN;
+}
+
+static void bbr_init_full_pipe(ngtcp2_bbr_cc *cc) {
+ cc->filled_pipe = 0;
+ cc->full_bw = 0;
+ cc->full_bw_count = 0;
+}
+
+static void bbr_check_full_pipe(ngtcp2_bbr_cc *cc) {
+ if (cc->filled_pipe || !cc->round_start || cc->rst->rs.is_app_limited) {
+ /* no need to check for a full pipe now. */
+ return;
+ }
+
+ /* cc->btl_bw still growing? */
+ if (cc->btl_bw * 100 >= cc->full_bw * 125) {
+ /* record new baseline level */
+ cc->full_bw = cc->btl_bw;
+ cc->full_bw_count = 0;
+ return;
+ }
+ /* another round w/o much growth */
+ ++cc->full_bw_count;
+ if (cc->full_bw_count >= 3) {
+ cc->filled_pipe = 1;
+ ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+ "bbr filled pipe, btl_bw=%" PRIu64, cc->btl_bw);
+ }
+}
+
+static void bbr_enter_drain(ngtcp2_bbr_cc *cc) {
+ cc->state = NGTCP2_BBR_STATE_DRAIN;
+ /* pace slowly */
+ cc->pacing_gain = 1.0 / NGTCP2_BBR_HIGH_GAIN;
+ /* maintain cwnd */
+ cc->cwnd_gain = NGTCP2_BBR_HIGH_GAIN;
+}
+
+static void bbr_check_drain(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts) {
+ if (cc->state == NGTCP2_BBR_STATE_STARTUP && cc->filled_pipe) {
+ ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+ "bbr exit Startup and enter Drain");
+
+ bbr_enter_drain(cc);
+ }
+
+ if (cc->state == NGTCP2_BBR_STATE_DRAIN &&
+ cstat->bytes_in_flight <= bbr_inflight(cc, cstat, 1.0)) {
+ ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+ "bbr exit Drain and enter ProbeBW");
+
+ /* we estimate queue is drained */
+ bbr_enter_probe_bw(cc, ts);
+ }
+}
+
+static void bbr_enter_probe_bw(ngtcp2_bbr_cc *cc, ngtcp2_tstamp ts) {
+ uint8_t rand;
+
+ cc->state = NGTCP2_BBR_STATE_PROBE_BW;
+ cc->pacing_gain = 1;
+ cc->cwnd_gain = 2;
+
+ assert(cc->rand);
+
+ cc->rand(&rand, 1, &cc->rand_ctx);
+
+ cc->cycle_index = NGTCP2_BBR_GAIN_CYCLELEN - 1 - (size_t)(rand * 7 / 256);
+ bbr_advance_cycle_phase(cc, ts);
+}
+
+static void bbr_check_cycle_phase(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts) {
+ if (cc->state == NGTCP2_BBR_STATE_PROBE_BW &&
+ bbr_is_next_cycle_phase(cc, cstat, ack, ts)) {
+ bbr_advance_cycle_phase(cc, ts);
+ }
+}
+
+static void bbr_advance_cycle_phase(ngtcp2_bbr_cc *cc, ngtcp2_tstamp ts) {
+ cc->cycle_stamp = ts;
+ cc->cycle_index = (cc->cycle_index + 1) & (NGTCP2_BBR_GAIN_CYCLELEN - 1);
+ cc->pacing_gain = pacing_gain_cycle[cc->cycle_index];
+}
+
+static int bbr_is_next_cycle_phase(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts) {
+ int is_full_length = (ts - cc->cycle_stamp) > cc->rt_prop;
+
+ if (cc->pacing_gain > 1) {
+ return is_full_length && (ack->bytes_lost > 0 ||
+ ack->prior_bytes_in_flight >=
+ bbr_inflight(cc, cstat, cc->pacing_gain));
+ }
+
+ if (cc->pacing_gain < 1) {
+ return is_full_length ||
+ ack->prior_bytes_in_flight <= bbr_inflight(cc, cstat, 1);
+ }
+
+ return is_full_length;
+}
+
+static void bbr_handle_restart_from_idle(ngtcp2_bbr_cc *cc,
+ ngtcp2_conn_stat *cstat) {
+ if (cstat->bytes_in_flight == 0 && cc->rst->app_limited) {
+ ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV, "bbr restart from idle");
+
+ cc->idle_restart = 1;
+
+ if (cc->state == NGTCP2_BBR_STATE_PROBE_BW) {
+ bbr_set_pacing_rate_with_gain(cc, cstat, 1);
+ }
+ }
+}
+
+static void bbr_check_probe_rtt(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts) {
+ if (cc->state != NGTCP2_BBR_STATE_PROBE_RTT && cc->rtprop_expired &&
+ !cc->idle_restart) {
+ ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV, "bbr enter ProbeRTT");
+
+ bbr_enter_probe_rtt(cc);
+ bbr_save_cwnd(cc, cstat);
+ cc->probe_rtt_done_stamp = UINT64_MAX;
+ }
+
+ if (cc->state == NGTCP2_BBR_STATE_PROBE_RTT) {
+ bbr_handle_probe_rtt(cc, cstat, ts);
+ }
+
+ cc->idle_restart = 0;
+}
+
+static void bbr_enter_probe_rtt(ngtcp2_bbr_cc *cc) {
+ cc->state = NGTCP2_BBR_STATE_PROBE_RTT;
+ cc->pacing_gain = 1;
+ cc->cwnd_gain = 1;
+}
+
+static void bbr_handle_probe_rtt(ngtcp2_bbr_cc *cc, ngtcp2_conn_stat *cstat,
+ ngtcp2_tstamp ts) {
+ uint64_t app_limited = cc->rst->delivered + cstat->bytes_in_flight;
+
+ /* Ignore low rate samples during NGTCP2_BBR_STATE_PROBE_RTT. */
+ cc->rst->app_limited = app_limited ? app_limited : 1;
+
+ if (cc->probe_rtt_done_stamp == UINT64_MAX &&
+ cstat->bytes_in_flight <= min_pipe_cwnd(cstat->max_tx_udp_payload_size)) {
+ cc->probe_rtt_done_stamp = ts + NGTCP2_BBR_PROBE_RTT_DURATION;
+ cc->probe_rtt_round_done = 0;
+ cc->next_round_delivered = cc->rst->delivered;
+
+ return;
+ }
+
+ if (cc->probe_rtt_done_stamp != UINT64_MAX) {
+ if (cc->round_start) {
+ cc->probe_rtt_round_done = 1;
+ }
+
+ if (cc->probe_rtt_round_done && ts > cc->probe_rtt_done_stamp) {
+ cc->rtprop_stamp = ts;
+ bbr_restore_cwnd(cc, cstat);
+ bbr_exit_probe_rtt(cc, ts);
+ }
+ }
+}
+
+static void bbr_exit_probe_rtt(ngtcp2_bbr_cc *cc, ngtcp2_tstamp ts) {
+ if (cc->filled_pipe) {
+ ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+ "bbr exit ProbeRTT and enter ProbeBW");
+
+ bbr_enter_probe_bw(cc, ts);
+
+ return;
+ }
+
+ ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+ "bbr exit ProbeRTT and enter Startup");
+
+ bbr_enter_startup(cc);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-25 09:09:38 +0000