1 files changed, 615 insertions, 0 deletions

diff --git a/lib/ngtcp2_cc.c b/lib/ngtcp2_cc.c
new file mode 100644
index 0000000..0536639
--- /dev/null
+++ b/lib/ngtcp2_cc.c
@@ -0,0 +1,615 @@
+/*
+ * ngtcp2
+ *
+ * Copyright (c) 2018 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_cc.h"
+
+#include <assert.h>
+
+#if defined(_MSC_VER)
+#  include <intrin.h>
+#endif
+
+#include "ngtcp2_log.h"
+#include "ngtcp2_macro.h"
+#include "ngtcp2_mem.h"
+#include "ngtcp2_rcvry.h"
+
+uint64_t ngtcp2_cc_compute_initcwnd(size_t max_udp_payload_size) {
+  uint64_t n = 2 * max_udp_payload_size;
+  n = ngtcp2_max(n, 14720);
+  return ngtcp2_min(10 * max_udp_payload_size, n);
+}
+
+ngtcp2_cc_pkt *ngtcp2_cc_pkt_init(ngtcp2_cc_pkt *pkt, int64_t pkt_num,
+                                  size_t pktlen, ngtcp2_pktns_id pktns_id,
+                                  ngtcp2_tstamp sent_ts, uint64_t lost,
+                                  uint64_t tx_in_flight, int is_app_limited) {
+  pkt->pkt_num = pkt_num;
+  pkt->pktlen = pktlen;
+  pkt->pktns_id = pktns_id;
+  pkt->sent_ts = sent_ts;
+  pkt->lost = lost;
+  pkt->tx_in_flight = tx_in_flight;
+  pkt->is_app_limited = is_app_limited;
+
+  return pkt;
+}
+
+static void reno_cc_reset(ngtcp2_reno_cc *cc) {
+  cc->max_delivery_rate_sec = 0;
+  cc->target_cwnd = 0;
+  cc->pending_add = 0;
+}
+
+void ngtcp2_reno_cc_init(ngtcp2_reno_cc *cc, ngtcp2_log *log) {
+  cc->ccb.log = log;
+  reno_cc_reset(cc);
+}
+
+void ngtcp2_reno_cc_free(ngtcp2_reno_cc *cc) { (void)cc; }
+
+int ngtcp2_cc_reno_cc_init(ngtcp2_cc *cc, ngtcp2_log *log,
+                           const ngtcp2_mem *mem) {
+  ngtcp2_reno_cc *reno_cc;
+
+  reno_cc = ngtcp2_mem_calloc(mem, 1, sizeof(ngtcp2_reno_cc));
+  if (reno_cc == NULL) {
+    return NGTCP2_ERR_NOMEM;
+  }
+
+  ngtcp2_reno_cc_init(reno_cc, log);
+
+  cc->ccb = &reno_cc->ccb;
+  cc->on_pkt_acked = ngtcp2_cc_reno_cc_on_pkt_acked;
+  cc->congestion_event = ngtcp2_cc_reno_cc_congestion_event;
+  cc->on_persistent_congestion = ngtcp2_cc_reno_cc_on_persistent_congestion;
+  cc->on_ack_recv = ngtcp2_cc_reno_cc_on_ack_recv;
+  cc->reset = ngtcp2_cc_reno_cc_reset;
+
+  return 0;
+}
+
+void ngtcp2_cc_reno_cc_free(ngtcp2_cc *cc, const ngtcp2_mem *mem) {
+  ngtcp2_reno_cc *reno_cc = ngtcp2_struct_of(cc->ccb, ngtcp2_reno_cc, ccb);
+
+  ngtcp2_reno_cc_free(reno_cc);
+  ngtcp2_mem_free(mem, reno_cc);
+}
+
+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_reno_cc_on_pkt_acked(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                                    const ngtcp2_cc_pkt *pkt,
+                                    ngtcp2_tstamp ts) {
+  ngtcp2_reno_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_reno_cc, ccb);
+  uint64_t m;
+  (void)ts;
+
+  if (in_congestion_recovery(cstat, pkt->sent_ts)) {
+    return;
+  }
+
+  if (cc->target_cwnd && cc->target_cwnd < cstat->cwnd) {
+    return;
+  }
+
+  if (cstat->cwnd < cstat->ssthresh) {
+    cstat->cwnd += pkt->pktlen;
+    ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                    "pkn=%" PRId64 " acked, slow start cwnd=%" PRIu64,
+                    pkt->pkt_num, cstat->cwnd);
+    return;
+  }
+
+  m = cstat->max_tx_udp_payload_size * pkt->pktlen + cc->pending_add;
+  cc->pending_add = m % cstat->cwnd;
+
+  cstat->cwnd += m / cstat->cwnd;
+}
+
+void ngtcp2_cc_reno_cc_congestion_event(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                                        ngtcp2_tstamp sent_ts,
+                                        ngtcp2_tstamp ts) {
+  ngtcp2_reno_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_reno_cc, ccb);
+  uint64_t min_cwnd;
+
+  if (in_congestion_recovery(cstat, sent_ts)) {
+    return;
+  }
+
+  cstat->congestion_recovery_start_ts = ts;
+  cstat->cwnd >>= NGTCP2_LOSS_REDUCTION_FACTOR_BITS;
+  min_cwnd = 2 * cstat->max_tx_udp_payload_size;
+  cstat->cwnd = ngtcp2_max(cstat->cwnd, min_cwnd);
+  cstat->ssthresh = cstat->cwnd;
+
+  cc->pending_add = 0;
+
+  ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                  "reduce cwnd because of packet loss cwnd=%" PRIu64,
+                  cstat->cwnd);
+}
+
+void ngtcp2_cc_reno_cc_on_persistent_congestion(ngtcp2_cc *ccx,
+                                                ngtcp2_conn_stat *cstat,
+                                                ngtcp2_tstamp ts) {
+  (void)ccx;
+  (void)ts;
+
+  cstat->cwnd = 2 * cstat->max_tx_udp_payload_size;
+  cstat->congestion_recovery_start_ts = UINT64_MAX;
+}
+
+void ngtcp2_cc_reno_cc_on_ack_recv(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                                   const ngtcp2_cc_ack *ack, ngtcp2_tstamp ts) {
+  ngtcp2_reno_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_reno_cc, ccb);
+  uint64_t target_cwnd, initcwnd;
+  (void)ack;
+  (void)ts;
+
+  /* TODO Use sliding window for min rtt measurement */
+  /* TODO Use sliding window */
+  cc->max_delivery_rate_sec =
+      ngtcp2_max(cc->max_delivery_rate_sec, cstat->delivery_rate_sec);
+
+  if (cstat->min_rtt != UINT64_MAX && cc->max_delivery_rate_sec) {
+    target_cwnd = cc->max_delivery_rate_sec * cstat->min_rtt / NGTCP2_SECONDS;
+    initcwnd = ngtcp2_cc_compute_initcwnd(cstat->max_tx_udp_payload_size);
+    cc->target_cwnd = ngtcp2_max(initcwnd, target_cwnd) * 289 / 100;
+
+    ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                    "target_cwnd=%" PRIu64 " max_delivery_rate_sec=%" PRIu64
+                    " min_rtt=%" PRIu64,
+                    cc->target_cwnd, cc->max_delivery_rate_sec, cstat->min_rtt);
+  }
+}
+
+void ngtcp2_cc_reno_cc_reset(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                             ngtcp2_tstamp ts) {
+  ngtcp2_reno_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_reno_cc, ccb);
+  (void)cstat;
+  (void)ts;
+
+  reno_cc_reset(cc);
+}
+
+static void cubic_cc_reset(ngtcp2_cubic_cc *cc) {
+  cc->max_delivery_rate_sec = 0;
+  cc->target_cwnd = 0;
+  cc->w_last_max = 0;
+  cc->w_tcp = 0;
+  cc->origin_point = 0;
+  cc->epoch_start = UINT64_MAX;
+  cc->k = 0;
+
+  cc->prior.cwnd = 0;
+  cc->prior.ssthresh = 0;
+  cc->prior.w_last_max = 0;
+  cc->prior.w_tcp = 0;
+  cc->prior.origin_point = 0;
+  cc->prior.epoch_start = UINT64_MAX;
+  cc->prior.k = 0;
+
+  cc->rtt_sample_count = 0;
+  cc->current_round_min_rtt = UINT64_MAX;
+  cc->last_round_min_rtt = UINT64_MAX;
+  cc->window_end = -1;
+}
+
+void ngtcp2_cubic_cc_init(ngtcp2_cubic_cc *cc, ngtcp2_log *log) {
+  cc->ccb.log = log;
+  cubic_cc_reset(cc);
+}
+
+void ngtcp2_cubic_cc_free(ngtcp2_cubic_cc *cc) { (void)cc; }
+
+int ngtcp2_cc_cubic_cc_init(ngtcp2_cc *cc, ngtcp2_log *log,
+                            const ngtcp2_mem *mem) {
+  ngtcp2_cubic_cc *cubic_cc;
+
+  cubic_cc = ngtcp2_mem_calloc(mem, 1, sizeof(ngtcp2_cubic_cc));
+  if (cubic_cc == NULL) {
+    return NGTCP2_ERR_NOMEM;
+  }
+
+  ngtcp2_cubic_cc_init(cubic_cc, log);
+
+  cc->ccb = &cubic_cc->ccb;
+  cc->on_pkt_acked = ngtcp2_cc_cubic_cc_on_pkt_acked;
+  cc->congestion_event = ngtcp2_cc_cubic_cc_congestion_event;
+  cc->on_spurious_congestion = ngtcp2_cc_cubic_cc_on_spurious_congestion;
+  cc->on_persistent_congestion = ngtcp2_cc_cubic_cc_on_persistent_congestion;
+  cc->on_ack_recv = ngtcp2_cc_cubic_cc_on_ack_recv;
+  cc->on_pkt_sent = ngtcp2_cc_cubic_cc_on_pkt_sent;
+  cc->new_rtt_sample = ngtcp2_cc_cubic_cc_new_rtt_sample;
+  cc->reset = ngtcp2_cc_cubic_cc_reset;
+  cc->event = ngtcp2_cc_cubic_cc_event;
+
+  return 0;
+}
+
+void ngtcp2_cc_cubic_cc_free(ngtcp2_cc *cc, const ngtcp2_mem *mem) {
+  ngtcp2_cubic_cc *cubic_cc = ngtcp2_struct_of(cc->ccb, ngtcp2_cubic_cc, ccb);
+
+  ngtcp2_cubic_cc_free(cubic_cc);
+  ngtcp2_mem_free(mem, cubic_cc);
+}
+
+static uint64_t ngtcp2_cbrt(uint64_t n) {
+  int d;
+  uint64_t a;
+
+  if (n == 0) {
+    return 0;
+  }
+
+#if defined(_MSC_VER)
+#  if defined(_M_X64)
+  d = (int)__lzcnt64(n);
+#  elif defined(_M_ARM64)
+  {
+    unsigned long index;
+    d = sizeof(uint64_t) * CHAR_BIT;
+    if (_BitScanReverse64(&index, n)) {
+      d = d - 1 - index;
+    }
+  }
+#  else
+  if ((n >> 32) != 0) {
+    d = __lzcnt((unsigned int)(n >> 32));
+  } else {
+    d = 32 + __lzcnt((unsigned int)n);
+  }
+#  endif
+#else
+  d = __builtin_clzll(n);
+#endif
+  a = 1ULL << ((64 - d) / 3 + 1);
+
+  for (; a * a * a > n;) {
+    a = (2 * a + n / a / a) / 3;
+  }
+  return a;
+}
+
+/* HyStart++ constants */
+#define NGTCP2_HS_MIN_SSTHRESH 16
+#define NGTCP2_HS_N_RTT_SAMPLE 8
+#define NGTCP2_HS_MIN_ETA (4 * NGTCP2_MILLISECONDS)
+#define NGTCP2_HS_MAX_ETA (16 * NGTCP2_MILLISECONDS)
+
+void ngtcp2_cc_cubic_cc_on_pkt_acked(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                                     const ngtcp2_cc_pkt *pkt,
+                                     ngtcp2_tstamp ts) {
+  ngtcp2_cubic_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_cubic_cc, ccb);
+  ngtcp2_duration t, eta;
+  uint64_t target, cwnd_thres;
+  uint64_t tx, kx, time_delta, delta;
+  uint64_t add, tcp_add;
+  uint64_t m;
+
+  if (pkt->pktns_id == NGTCP2_PKTNS_ID_APPLICATION && cc->window_end != -1 &&
+      cc->window_end <= pkt->pkt_num) {
+    cc->window_end = -1;
+  }
+
+  if (in_congestion_recovery(cstat, pkt->sent_ts)) {
+    return;
+  }
+
+  if (cc->target_cwnd && cc->target_cwnd < cstat->cwnd) {
+    return;
+  }
+
+  if (cstat->cwnd < cstat->ssthresh) {
+    /* slow-start */
+    cstat->cwnd += pkt->pktlen;
+
+    ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                    "pkn=%" PRId64 " acked, slow start cwnd=%" PRIu64,
+                    pkt->pkt_num, cstat->cwnd);
+
+    if (cc->last_round_min_rtt != UINT64_MAX &&
+        cc->current_round_min_rtt != UINT64_MAX &&
+        cstat->cwnd >=
+            NGTCP2_HS_MIN_SSTHRESH * cstat->max_tx_udp_payload_size &&
+        cc->rtt_sample_count >= NGTCP2_HS_N_RTT_SAMPLE) {
+      eta = cc->last_round_min_rtt / 8;
+
+      if (eta < NGTCP2_HS_MIN_ETA) {
+        eta = NGTCP2_HS_MIN_ETA;
+      } else if (eta > NGTCP2_HS_MAX_ETA) {
+        eta = NGTCP2_HS_MAX_ETA;
+      }
+
+      if (cc->current_round_min_rtt >= cc->last_round_min_rtt + eta) {
+        ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                        "HyStart++ exit slow start");
+
+        cc->w_last_max = cstat->cwnd;
+        cstat->ssthresh = cstat->cwnd;
+      }
+    }
+
+    return;
+  }
+
+  /* congestion avoidance */
+
+  if (cc->epoch_start == UINT64_MAX) {
+    cc->epoch_start = ts;
+    if (cstat->cwnd < cc->w_last_max) {
+      cc->k = ngtcp2_cbrt((cc->w_last_max - cstat->cwnd) * 10 / 4 /
+                          cstat->max_tx_udp_payload_size);
+      cc->origin_point = cc->w_last_max;
+    } else {
+      cc->k = 0;
+      cc->origin_point = cstat->cwnd;
+    }
+
+    cc->w_tcp = cstat->cwnd;
+
+    ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                    "cubic-ca epoch_start=%" PRIu64 " k=%" PRIu64
+                    " origin_point=%" PRIu64,
+                    cc->epoch_start, cc->k, cc->origin_point);
+
+    cc->pending_add = 0;
+    cc->pending_w_add = 0;
+  }
+
+  t = ts - cc->epoch_start;
+
+  tx = (t << 10) / NGTCP2_SECONDS;
+  kx = (cc->k << 10);
+
+  if (tx > kx) {
+    time_delta = tx - kx;
+  } else {
+    time_delta = kx - tx;
+  }
+
+  delta = cstat->max_tx_udp_payload_size *
+          ((((time_delta * time_delta) >> 10) * time_delta) >> 10) * 4 / 10;
+  delta >>= 10;
+
+  if (tx > kx) {
+    target = cc->origin_point + delta;
+  } else {
+    target = cc->origin_point - delta;
+  }
+
+  cwnd_thres =
+      (target * (((t + cstat->smoothed_rtt) << 10) / NGTCP2_SECONDS)) >> 10;
+  if (cwnd_thres < cstat->cwnd) {
+    target = cstat->cwnd;
+  } else if (2 * cwnd_thres > 3 * cstat->cwnd) {
+    target = cstat->cwnd * 3 / 2;
+  } else {
+    target = cwnd_thres;
+  }
+
+  if (target > cstat->cwnd) {
+    m = cc->pending_add +
+        cstat->max_tx_udp_payload_size * (target - cstat->cwnd);
+    add = m / cstat->cwnd;
+    cc->pending_add = m % cstat->cwnd;
+  } else {
+    m = cc->pending_add + cstat->max_tx_udp_payload_size;
+    add = m / (100 * cstat->cwnd);
+    cc->pending_add = m % (100 * cstat->cwnd);
+  }
+
+  m = cc->pending_w_add + cstat->max_tx_udp_payload_size * pkt->pktlen;
+
+  cc->w_tcp += m / cstat->cwnd;
+  cc->pending_w_add = m % cstat->cwnd;
+
+  if (cc->w_tcp > cstat->cwnd) {
+    tcp_add = cstat->max_tx_udp_payload_size * (cc->w_tcp - cstat->cwnd) /
+              cstat->cwnd;
+    if (tcp_add > add) {
+      add = tcp_add;
+    }
+  }
+
+  cstat->cwnd += add;
+
+  ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                  "pkn=%" PRId64 " acked, cubic-ca cwnd=%" PRIu64 " t=%" PRIu64
+                  " k=%" PRIi64 " time_delta=%" PRIu64 " delta=%" PRIu64
+                  " target=%" PRIu64 " w_tcp=%" PRIu64,
+                  pkt->pkt_num, cstat->cwnd, t, cc->k, time_delta >> 4, delta,
+                  target, cc->w_tcp);
+}
+
+void ngtcp2_cc_cubic_cc_congestion_event(ngtcp2_cc *ccx,
+                                         ngtcp2_conn_stat *cstat,
+                                         ngtcp2_tstamp sent_ts,
+                                         ngtcp2_tstamp ts) {
+  ngtcp2_cubic_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_cubic_cc, ccb);
+  uint64_t min_cwnd;
+
+  if (in_congestion_recovery(cstat, sent_ts)) {
+    return;
+  }
+
+  if (cc->prior.cwnd < cstat->cwnd) {
+    cc->prior.cwnd = cstat->cwnd;
+    cc->prior.ssthresh = cstat->ssthresh;
+    cc->prior.w_last_max = cc->w_last_max;
+    cc->prior.w_tcp = cc->w_tcp;
+    cc->prior.origin_point = cc->origin_point;
+    cc->prior.epoch_start = cc->epoch_start;
+    cc->prior.k = cc->k;
+  }
+
+  cstat->congestion_recovery_start_ts = ts;
+
+  cc->epoch_start = UINT64_MAX;
+  if (cstat->cwnd < cc->w_last_max) {
+    cc->w_last_max = cstat->cwnd * 17 / 10 / 2;
+  } else {
+    cc->w_last_max = cstat->cwnd;
+  }
+
+  min_cwnd = 2 * cstat->max_tx_udp_payload_size;
+  cstat->ssthresh = cstat->cwnd * 7 / 10;
+  cstat->ssthresh = ngtcp2_max(cstat->ssthresh, min_cwnd);
+  cstat->cwnd = cstat->ssthresh;
+
+  ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                  "reduce cwnd because of packet loss cwnd=%" PRIu64,
+                  cstat->cwnd);
+}
+
+void ngtcp2_cc_cubic_cc_on_spurious_congestion(ngtcp2_cc *ccx,
+                                               ngtcp2_conn_stat *cstat,
+                                               ngtcp2_tstamp ts) {
+  ngtcp2_cubic_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_cubic_cc, ccb);
+  (void)ts;
+
+  if (cstat->cwnd >= cc->prior.cwnd) {
+    return;
+  }
+
+  cstat->congestion_recovery_start_ts = UINT64_MAX;
+
+  cstat->cwnd = cc->prior.cwnd;
+  cstat->ssthresh = cc->prior.ssthresh;
+  cc->w_last_max = cc->prior.w_last_max;
+  cc->w_tcp = cc->prior.w_tcp;
+  cc->origin_point = cc->prior.origin_point;
+  cc->epoch_start = cc->prior.epoch_start;
+  cc->k = cc->prior.k;
+
+  cc->prior.cwnd = 0;
+  cc->prior.ssthresh = 0;
+  cc->prior.w_last_max = 0;
+  cc->prior.w_tcp = 0;
+  cc->prior.origin_point = 0;
+  cc->prior.epoch_start = UINT64_MAX;
+  cc->prior.k = 0;
+
+  ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                  "spurious congestion is detected and congestion state is "
+                  "restored cwnd=%" PRIu64,
+                  cstat->cwnd);
+}
+
+void ngtcp2_cc_cubic_cc_on_persistent_congestion(ngtcp2_cc *ccx,
+                                                 ngtcp2_conn_stat *cstat,
+                                                 ngtcp2_tstamp ts) {
+  (void)ccx;
+  (void)ts;
+
+  cstat->cwnd = 2 * cstat->max_tx_udp_payload_size;
+  cstat->congestion_recovery_start_ts = UINT64_MAX;
+}
+
+void ngtcp2_cc_cubic_cc_on_ack_recv(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                                    const ngtcp2_cc_ack *ack,
+                                    ngtcp2_tstamp ts) {
+  ngtcp2_cubic_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_cubic_cc, ccb);
+  uint64_t target_cwnd, initcwnd;
+  (void)ack;
+  (void)ts;
+
+  /* TODO Use sliding window for min rtt measurement */
+  /* TODO Use sliding window */
+  cc->max_delivery_rate_sec =
+      ngtcp2_max(cc->max_delivery_rate_sec, cstat->delivery_rate_sec);
+
+  if (cstat->min_rtt != UINT64_MAX && cc->max_delivery_rate_sec) {
+    target_cwnd = cc->max_delivery_rate_sec * cstat->min_rtt / NGTCP2_SECONDS;
+    initcwnd = ngtcp2_cc_compute_initcwnd(cstat->max_tx_udp_payload_size);
+    cc->target_cwnd = ngtcp2_max(initcwnd, target_cwnd) * 289 / 100;
+
+    ngtcp2_log_info(cc->ccb.log, NGTCP2_LOG_EVENT_RCV,
+                    "target_cwnd=%" PRIu64 " max_delivery_rate_sec=%" PRIu64
+                    " min_rtt=%" PRIu64,
+                    cc->target_cwnd, cc->max_delivery_rate_sec, cstat->min_rtt);
+  }
+}
+
+void ngtcp2_cc_cubic_cc_on_pkt_sent(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                                    const ngtcp2_cc_pkt *pkt) {
+  ngtcp2_cubic_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_cubic_cc, ccb);
+  (void)cstat;
+
+  if (pkt->pktns_id != NGTCP2_PKTNS_ID_APPLICATION || cc->window_end != -1) {
+    return;
+  }
+
+  cc->window_end = pkt->pkt_num;
+  cc->last_round_min_rtt = cc->current_round_min_rtt;
+  cc->current_round_min_rtt = UINT64_MAX;
+  cc->rtt_sample_count = 0;
+}
+
+void ngtcp2_cc_cubic_cc_new_rtt_sample(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                                       ngtcp2_tstamp ts) {
+  ngtcp2_cubic_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_cubic_cc, ccb);
+  (void)ts;
+
+  if (cc->window_end == -1) {
+    return;
+  }
+
+  cc->current_round_min_rtt =
+      ngtcp2_min(cc->current_round_min_rtt, cstat->latest_rtt);
+  ++cc->rtt_sample_count;
+}
+
+void ngtcp2_cc_cubic_cc_reset(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                              ngtcp2_tstamp ts) {
+  ngtcp2_cubic_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_cubic_cc, ccb);
+  (void)cstat;
+  (void)ts;
+
+  cubic_cc_reset(cc);
+}
+
+void ngtcp2_cc_cubic_cc_event(ngtcp2_cc *ccx, ngtcp2_conn_stat *cstat,
+                              ngtcp2_cc_event_type event, ngtcp2_tstamp ts) {
+  ngtcp2_cubic_cc *cc = ngtcp2_struct_of(ccx->ccb, ngtcp2_cubic_cc, ccb);
+  ngtcp2_tstamp last_ts;
+
+  if (event != NGTCP2_CC_EVENT_TYPE_TX_START || cc->epoch_start == UINT64_MAX) {
+    return;
+  }
+
+  last_ts = cstat->last_tx_pkt_ts[NGTCP2_PKTNS_ID_APPLICATION];
+  if (last_ts == UINT64_MAX || last_ts <= cc->epoch_start) {
+    return;
+  }
+
+  assert(ts >= last_ts);
+
+  cc->epoch_start += ts - last_ts;
+}