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haproxy/src/quic_cc_cubic.c
Amaury Denoyelle 7bad88c35c BUG/MINOR: quic: ensure cwnd limits are always enforced 
Congestion window is limit by a minimal and maximum values which can
never be exceeded. Min value is hardcoded to 2 datagrams as recommended
by the specification. Max value is specified via haproxy configuration.

These values must be respected each time the congestion window size is
adjusted. However, in some rare occasions, limit were not always
enforced. Fix this by implementing wrappers to set or increment the
congestion window. These functions ensure limits are always applied
after the operation.

Additionnally, wrappers also ensure that if window reached a new maximum
value, it is saved in <cwnd_last_max> field.

This should be backported up to 2.6, after a brief period of
observation.
2025-04-29 15:10:06 +02:00

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#include <haproxy/global-t.h>
#include <haproxy/quic_cc.h>
#include <haproxy/quic_cc_hystart.h>
#include <haproxy/quic_trace.h>
#include <haproxy/quic_tune.h>
#include <haproxy/ticks.h>
#include <haproxy/trace.h>
/* IMPORTANT NOTE about the units defined by the RFC 9438
* (CUBIC for Fast and Long-Distance Networks):
*
* RFC 9438 4.1. Definitions:
* The unit of all window sizes in this document is segments of the SMSS, and
* the unit of all times is seconds. Implementations can use bytes to express
* window sizes, which would require factoring in the SMSS wherever necessary
* and replacing segments_acked (Figure 4) with the number of acknowledged
* bytes.
*/
/* So, this is the reason why here in this implementation each time a number
* of segments is used (typically a congestion window value), its value is
* multiplied by the MTU value.
*/
/* This source file is highly inspired from Linux kernel source file
* implementation for TCP Cubic. In fact, we have no choice if we do
* not want to use any floating point operations to be fast!
* (See net/ipv4/tcp_cubic.c)
*/
/* Constants definitions:
* CUBIC_BETA_SCALED refers to the scaled value of RFC 9438 beta_cubic variable.
* CUBIC_C_SCALED refers to the scaled value of RFC 9438 C variable.
*/
/* The right shifting value to apply to scaled values to get its real value. */
#define CUBIC_SCALE_FACTOR_SHIFT 10
/* CUBIC multiplicative decrease factor as described in RFC 9438 section 4.6 */
#define CUBIC_BETA_SCALED 717 /* beta_cubic = 0.7 (constant) */
/* CUBIC C constant that determines the aggressiveness of CUBIC in competing
* with other congestion control algorithms in high-BDP networks.
*/
#define CUBIC_C_SCALED 410 /* RFC 9438 C = 0.4 segment/seconds^3
* or 410 mB/s^3 in this implementation.
*/
/* The scaled value of 1 */
#define CUBIC_ONE_SCALED (1 << CUBIC_SCALE_FACTOR_SHIFT)
/* The maximum time value which may be cubed and multiplied by CUBIC_C_SCALED */
#define CUBIC_TIME_LIMIT 355535ULL /* ms */
/* By connection CUBIC algorithm state. Note that the current congestion window
* value is not stored in this structure.
*/
struct cubic {
/* QUIC_CC_ST_* state values. */
uint32_t state;
/* Slow start threshold (in bytes) */
uint32_t ssthresh;
/* Remaining number of acknowledged bytes between two ACK for CUBIC congestion
* control window (in bytes).
*/
uint32_t remaining_inc;
/* Start time of at which the current avoidance stage started (in ms). */
uint32_t t_epoch;
/* The window to reach for each recovery period during a concave region (in bytes). */
uint32_t W_target;
/* The time period to reach W_target during a concave region (in ms). */
uint32_t K;
/* The last window maximum reached (in bytes). */
uint32_t last_w_max;
/* Estimated value of the Reno congestion window in the TCP-friendly region (in bytes). */
uint32_t W_est;
/* Remaining number of acknowledged bytes between two ACKs for estimated
* TCP-Reno congestion control window (in bytes).
*/
uint32_t remaining_W_est_inc;
/* Start time of recovery period (used to avoid re-entering this state, if already
* in recovery period) (in ms).
*/
uint32_t recovery_start_time;
/* HyStart++ state. */
struct quic_hystart hystart;
/* Consecutive number of losses since last ACK */
uint32_t consecutive_losses;
};
static void quic_cc_cubic_reset(struct quic_cc *cc)
{
struct cubic *c = quic_cc_priv(cc);
TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
c->state = QUIC_CC_ST_SS;
c->ssthresh = QUIC_CC_INFINITE_SSTHESH;
c->remaining_inc = 0;
c->remaining_W_est_inc = 0;
c->t_epoch = 0;
c->W_target = 0;
c->K = 0;
c->last_w_max = 0;
c->W_est = 0;
c->recovery_start_time = 0;
if (quic_tune.options & QUIC_TUNE_CC_HYSTART)
quic_cc_hystart_reset(&c->hystart);
TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
}
static int quic_cc_cubic_init(struct quic_cc *cc)
{
struct cubic *c = quic_cc_priv(cc);
quic_cc_cubic_reset(cc);
c->consecutive_losses = 0;
return 1;
}
/* Cubic root.
* Highly inspired from Linux kernel sources.
* See net/ipv4/tcp_cubic.c
*/
static uint32_t cubic_root(uint64_t val)
{
uint32_t x, b, shift;
static const uint8_t v[] = {
0, 54, 54, 54, 118, 118, 118, 118,
123, 129, 134, 138, 143, 147, 151, 156,
157, 161, 164, 168, 170, 173, 176, 179,
181, 185, 187, 190, 192, 194, 197, 199,
200, 202, 204, 206, 209, 211, 213, 215,
217, 219, 221, 222, 224, 225, 227, 229,
231, 232, 234, 236, 237, 239, 240, 242,
244, 245, 246, 248, 250, 251, 252, 254,
};
if (!val || (b = my_flsl(val)) < 7) {
/* val in [0..63] */
return ((uint32_t)v[(uint32_t)val] + 35) >> 6;
}
b = ((b * 84) >> 8) - 1;
shift = (val >> (b * 3));
x = ((uint32_t)(((uint32_t)v[shift] + 10) << b)) >> 6;
x = 2 * x + (uint32_t)(val / ((uint64_t)x * (uint64_t)(x - 1)));
x = ((x * 341) >> 10);
return x;
}
/*
* RFC 9438 3.1. Principle 1 for the CUBIC Increase Function
*
* For better network utilization and stability, CUBIC [HRX08] uses a cubic
* window increase function in terms of the elapsed time from the last
* congestion event. While most congestion control algorithms that provide
* alternatives to Reno increase the congestion window using convex functions,
* CUBIC uses both the concave and convex profiles of a cubic function for
* window growth.
*
* After a window reduction in response to a congestion event detected by
* duplicate acknowledgments (ACKs), Explicit Congestion Notification-Echo
* (ECN-Echo (ECE)) ACKs [RFC3168], RACK-TLP for TCP [RFC8985], or QUIC loss
* detection [RFC9002], CUBIC remembers the congestion window size at which it
* received the congestion event and performs a multiplicative decrease of the
* congestion window. When CUBIC enters into congestion avoidance, it starts to
* increase the congestion window using the concave profile of the cubic
* function. The cubic function is set to have its plateau at the remembered
* congestion window size, so that the concave window increase continues until
* then. After that, the cubic function turns into a convex profile and the
* convex window increase begins.
*
* W_cubic(time) (bytes)
* ^ convex region
* | <------------------------->
* | . +
* | . +
* | . +
* | . +
* | . + ^
* | . + | W_cubic_t
* | . + |
* | . + |
* W_target |-----------+--------------------------+------------------------+
* (W_max) | +. + . t
* | + . + .
* | + . + .
* | + . + .
* | + . + .
* | .+ .
* | + .
* | + .
* | + .
* | . .
* | . .
* | . .
* +-----------+--------------------------+-+------------------------> time (s)
* 0 t_epoch (t_epoch + K)
* <-------------------------->
* . concave region
* .
* congestion
* event
*
* RFC 9438 4.2. Window Increase Function:
*
* W_cubic(t) = C*(t-K)^3 + W_max (Figure 1)
* K = cubic_root((W_max - cwnd_epoch)/C) (Figure 2)
*
* +--------------------------------------------------------------------+
* | RFC 9438 definitions | Code variables |
* +--------------------------------------------------------------------+
* | C (segments/s^3) | CUBIC_C_SCALED (mB/s^3) |
* +--------------------------------------------------------------------+
* | W_max (segments) | c->last_w_max - path->cwnd (bytes) |
* +--------------------------------------------------------------------+
* | K (s) | c->K (ms) |
* +--------------------------------------------------------------------+
* | beta_cubic (constant) | CUBIC_BETA_SCALED (constant) |
* +--------------------------------------------------------------------+
*/
static inline void quic_cubic_update(struct quic_cc *cc, uint32_t acked)
{
struct cubic *c = quic_cc_priv(cc);
struct quic_cc_path *path = container_of(cc, struct quic_cc_path, cc);
/* The elapsed time since the start of the congestion event. */
uint32_t elapsed_time;
/* Target value of the congestion window. */
uint32_t target;
/* The time at which the congestion window will be computed based
* on the cubic increase function.
*/
uint64_t t;
/* The computed value of the congestion window at time t based on the cubic
* increase function.
*/
uint64_t W_cubic_t;
uint32_t inc, inc_diff;
TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
if (!c->t_epoch) {
c->t_epoch = now_ms;
if (c->last_w_max <= path->cwnd) {
c->K = 0;
c->W_target = path->cwnd;
}
else {
uint64_t wnd_diff;
/* K value computing (in seconds):
* K = cubic_root((W_max - cwnd_epoch)/C) (Figure 2)
* Note that K is stored in milliseconds and that
* 8000 * 125000 = 1000^3.
*
* Supporting 2^40 windows, shifted by 10, leaves ~13 bits of unused
* precision. We exploit this precision for our NS conversion by
* multiplying by 8000 without overflowing, then later by 125000
* after the divide so that we limit the precision loss to the minimum
* before the cubic_root() call."
*/
wnd_diff = (c->last_w_max - path->cwnd) << CUBIC_SCALE_FACTOR_SHIFT;
wnd_diff *= 8000ULL;
wnd_diff /= CUBIC_C_SCALED * path->mtu;
wnd_diff *= 125000ULL;
c->K = cubic_root(wnd_diff);
c->W_target = c->last_w_max;
}
c->W_est = path->cwnd;
c->remaining_inc = 0;
c->remaining_W_est_inc = 0;
}
elapsed_time = now_ms + path->loss.rtt_min - c->t_epoch;
if (elapsed_time < c->K) {
t = c->K - elapsed_time;
}
else {
t = elapsed_time - c->K;
}
if (t > CUBIC_TIME_LIMIT) {
/* TODO : should not happen if we handle the case
* of very late acks receipt. This must be handled as a congestion
* control event: a very late ack should trigger a congestion
* control algorithm reset.
*/
quic_cc_cubic_reset(cc);
goto leave;
}
/* Compute W_cubic_t at t time. */
W_cubic_t = CUBIC_C_SCALED * path->mtu;
W_cubic_t = (W_cubic_t * t) / 1000;
W_cubic_t = (W_cubic_t * t) / 1000;
W_cubic_t = (W_cubic_t * t) / 1000;
W_cubic_t >>= CUBIC_SCALE_FACTOR_SHIFT;
if (elapsed_time < c->K)
target = c->W_target - W_cubic_t;
else
target = c->W_target + W_cubic_t;
if (target > path->cwnd) {
/* Concave region */
/* RFC 9438 4.4. Concave Region
*
* When receiving a new ACK in congestion avoidance, if CUBIC is not in
* the Reno-friendly region and cwnd is less than Wmax, then CUBIC is
* in the concave region. In this region, cwnd MUST be incremented by
* (target - cwnd) / cwnd.
*/
inc_diff = c->remaining_inc + path->mtu * (target - path->cwnd);
c->remaining_inc = inc_diff % path->cwnd;
inc = inc_diff / path->cwnd;
}
else {
/* Convex region: very small increment */
/* RFC 9438 4.5. Convex Region
*
* When receiving a new ACK in congestion avoidance, if CUBIC is not in
* the Reno-friendly region and cwnd is larger than or equal to Wmax,
* then CUBIC is in the convex region.The convex region indicates that
* the network conditions might have changed since the last congestion
* event, possibly implying more available bandwidth after some flow
* departures. Since the Internet is highly asynchronous, some amount
* of perturbation is always possible without causing a major change in
* available bandwidth.Unless the cwnd is overridden by the AIMD window
* increase, CUBIC will behave cautiously when operating in this region.
* The convex profile aims to increase the window very slowly at the
* beginning when cwnd is around Wmax and then gradually increases its
* rate of increase. This region is also called the "maximum probing
* phase", since CUBIC is searching for a new Wmax. In this region,
* cwnd MUST be incremented by (target - cwnd) / cwnd) for each received
* new ACK, where target is calculated as described in Section 4.2.
*/
inc_diff = c->remaining_inc + path->mtu;
c->remaining_inc = inc_diff % (100 * path->cwnd);
inc = inc_diff / (100 * path->cwnd);
}
inc_diff = c->remaining_W_est_inc + path->mtu * acked;
c->W_est += inc_diff / path->cwnd;
c->remaining_W_est_inc = inc_diff % path->cwnd;
/* TCP friendliness :
* RFC 9438 4.3. Reno-Friendly Region
*
* Reno performs well in certain types of networks -- for example, under
* short RTTs and small bandwidths (or small BDPs). In these networks,
* CUBIC remains in the Reno-friendly region to achieve at least the same
* throughput as Reno.
*
* When receiving a new ACK in congestion avoidance (where cwnd could be
* greater than or less than Wmax), CUBIC checks whether Wcubic(t) is less
* than West. If so, CUBIC is in the Reno-friendly region and cwnd SHOULD
* be set to West at each reception of a new ACK.
*
* West is set equal to cwnd_epoch at the start of the congestion avoidance
* stage. After that, on every new ACK, West is updated using Figure 4.
* Note that this equation uses segments_acked and cwnd is measured in
* segments. An implementation that measures cwnd in bytes should adjust the
* equation accordingly using the number of acknowledged bytes and the SMSS.
* Also note that this equation works for connections with enabled or
* disabled delayed ACKs [RFC5681], as segments_acked will be different based
* on the segments actually acknowledged by a new ACK.
*
* Figure 4 : West = West + alpha_cubic * (segments_acked / cwnd)
*
* Once West has grown to reach the cwnd at the time of most recently
* setting ssthresh -- that is, West >= cwndprior -- the sender SHOULD set
* alpha_cubic to 1 to ensure that it can achieve the same congestion window
* increment rate as Reno, which uses AIMD(1, 0.5).
*/
if (c->W_est > path->cwnd) {
uint32_t W_est_inc = path->mtu * (c->W_est - path->cwnd) / path->cwnd;
if (W_est_inc > inc)
inc = W_est_inc;
}
quic_cc_path_inc(path, inc);
leave:
TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
}
static void quic_cc_cubic_slow_start(struct quic_cc *cc)
{
TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
quic_cc_cubic_reset(cc);
TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
}
static void quic_enter_recovery(struct quic_cc *cc)
{
struct quic_cc_path *path = container_of(cc, struct quic_cc_path, cc);
struct cubic *c = quic_cc_priv(cc);
/* Current cwnd as number of packets */
TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
c->t_epoch = 0;
c->recovery_start_time = now_ms;
/* RFC 9438 4.7. Fast Convergence
*
* To improve convergence speed, CUBIC uses a heuristic. When a new flow
* joins the network, existing flows need to give up some of their bandwidth
* to allow the new flow some room for growth if the existing flows have
* been using all the network bandwidth. To speed up this bandwidth release
* by existing flows, the following fast convergence mechanism SHOULD be
* implemented.With fast convergence, when a congestion event occurs, Wmax
* is updated as follows, before the window reduction described in Section
* 4.6.
*
* if cwnd < Wmax and fast convergence enabled, further reduce Wax:
* Wmax = cwnd * (1 + beta_cubic)
* otherwise, remember cwn before reduction:
* Wmax = cwnd
*/
if (path->cwnd < c->last_w_max) {
/* (1 + beta_cubic) * path->cwnd / 2 */
c->last_w_max = (path->cwnd * (CUBIC_ONE_SCALED + CUBIC_BETA_SCALED) / 2) >> CUBIC_SCALE_FACTOR_SHIFT;
}
else {
c->last_w_max = path->cwnd;
}
c->ssthresh = (CUBIC_BETA_SCALED * path->cwnd) >> CUBIC_SCALE_FACTOR_SHIFT;
quic_cc_path_set(path, c->ssthresh);
c->state = QUIC_CC_ST_RP;
TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc, NULL, cc);
}
/* Congestion slow-start callback. */
static void quic_cc_cubic_ss_cb(struct quic_cc *cc, struct quic_cc_event *ev)
{
struct quic_cc_path *path = container_of(cc, struct quic_cc_path, cc);
struct cubic *c = quic_cc_priv(cc);
TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, ev);
switch (ev->type) {
case QUIC_CC_EVT_ACK:
if (quic_tune.options & QUIC_TUNE_CC_HYSTART) {
struct quic_hystart *h = &c->hystart;
unsigned int acked = QUIC_MIN(ev->ack.acked, (uint64_t)HYSTART_LIMIT * path->mtu);
if (path->cwnd >= QUIC_CC_INFINITE_SSTHESH - acked)
goto out;
quic_cc_path_inc(path, acked);
quic_cc_hystart_track_min_rtt(cc, h, path->loss.latest_rtt);
if (ev->ack.pn >= h->wnd_end)
h->wnd_end = UINT64_MAX;
if (quic_cc_hystart_may_enter_cs(&c->hystart)) {
/* Exit slow start and enter conservative slow start */
c->state = QUIC_CC_ST_CS;
goto out;
}
}
else if (path->cwnd < QUIC_CC_INFINITE_SSTHESH - ev->ack.acked) {
quic_cc_path_inc(path, ev->ack.acked);
}
/* Exit to congestion avoidance if slow start threshold is reached. */
if (path->cwnd >= c->ssthresh)
c->state = QUIC_CC_ST_CA;
break;
case QUIC_CC_EVT_LOSS:
quic_enter_recovery(cc);
break;
case QUIC_CC_EVT_ECN_CE:
/* TODO */
break;
}
out:
TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, NULL, cc);
TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
}
/* Congestion avoidance callback. */
static void quic_cc_cubic_ca_cb(struct quic_cc *cc, struct quic_cc_event *ev)
{
struct cubic *c = quic_cc_priv(cc);
TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, ev);
switch (ev->type) {
case QUIC_CC_EVT_ACK:
c->consecutive_losses = 0;
quic_cubic_update(cc, ev->ack.acked);
break;
case QUIC_CC_EVT_LOSS:
/* Principle: we may want to tolerate one or a few occasional
* losses that are *not* caused by congestion that we'd have
* any control on. Tests show that over long distances this
* significantly improves the transfer stability and
* performance, but can quickly result in a massive loss
* increase if set too high. This counter is reset upon ACKs.
* Maybe we could refine this to consider only certain ACKs
* though.
*/
c->consecutive_losses += ev->loss.count;
if (c->consecutive_losses <= global.tune.quic_cubic_loss_tol)
goto out;
quic_enter_recovery(cc);
break;
case QUIC_CC_EVT_ECN_CE:
/* TODO */
break;
}
out:
TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, NULL, cc);
TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
}
/* Conservative slow start callback. */
static void quic_cc_cubic_cs_cb(struct quic_cc *cc, struct quic_cc_event *ev)
{
struct quic_cc_path *path = container_of(cc, struct quic_cc_path, cc);
TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, ev);
switch (ev->type) {
case QUIC_CC_EVT_ACK:
{
struct cubic *c = quic_cc_priv(cc);
struct quic_hystart *h = &c->hystart;
unsigned int acked =
QUIC_MIN(ev->ack.acked, (uint64_t)HYSTART_LIMIT * path->mtu) / HYSTART_CSS_GROWTH_DIVISOR;
if (path->cwnd >= QUIC_CC_INFINITE_SSTHESH - acked)
goto out;
quic_cc_path_inc(path, acked);
quic_cc_hystart_track_min_rtt(cc, h, path->loss.latest_rtt);
if (quic_cc_hystart_may_reenter_ss(h)) {
/* Exit to slow start */
c->state = QUIC_CC_ST_SS;
goto out;
}
if (h->css_rnd_count >= HYSTART_CSS_ROUNDS) {
/* Exit to congestion avoidance
*
* RFC 9438 4.10. Slow start
*
* When CUBIC uses HyStart++ [RFC9406], it may exit the first slow start
* without incurring any packet loss and thus _W_max_ is undefined. In
* this special case, CUBIC sets _cwnd_prior = cwnd_ and switches to
* congestion avoidance. It then increases its congestion window size
* using Figure 1, where _t_ is the elapsed time since the beginning of
* the current congestion avoidance stage, _K_ is set to 0, and _W_max_
* is set to the congestion window size at the beginning of the current
* congestion avoidance stage.
*/
c->last_w_max = path->cwnd;
c->t_epoch = 0;
c->state = QUIC_CC_ST_CA;
}
break;
}
case QUIC_CC_EVT_LOSS:
quic_enter_recovery(cc);
break;
case QUIC_CC_EVT_ECN_CE:
/* TODO */
break;
}
out:
TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, NULL, cc);
TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
}
/* Recovery period callback */
static void quic_cc_cubic_rp_cb(struct quic_cc *cc, struct quic_cc_event *ev)
{
struct cubic *c = quic_cc_priv(cc);
TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc, ev);
TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, ev, cc);
switch (ev->type) {
case QUIC_CC_EVT_ACK:
/* RFC 9002 7.3.2. Recovery
* A recovery period ends and the sender enters congestion avoidance when a
* packet sent during the recovery period is acknowledged.
*/
if (tick_is_le(ev->ack.time_sent, c->recovery_start_time)) {
TRACE_PROTO("CC cubic (still in recov. period)", QUIC_EV_CONN_CC, cc->qc);
goto leave;
}
c->state = QUIC_CC_ST_CA;
c->recovery_start_time = TICK_ETERNITY;
break;
case QUIC_CC_EVT_LOSS:
break;
case QUIC_CC_EVT_ECN_CE:
/* TODO */
break;
}
leave:
TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, NULL, cc);
TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc, NULL, cc);
}
static void (*quic_cc_cubic_state_cbs[])(struct quic_cc *cc,
struct quic_cc_event *ev) = {
[QUIC_CC_ST_SS] = quic_cc_cubic_ss_cb,
[QUIC_CC_ST_CS] = quic_cc_cubic_cs_cb,
[QUIC_CC_ST_CA] = quic_cc_cubic_ca_cb,
[QUIC_CC_ST_RP] = quic_cc_cubic_rp_cb,
};
static void quic_cc_cubic_event(struct quic_cc *cc, struct quic_cc_event *ev)
{
struct cubic *c = quic_cc_priv(cc);
return quic_cc_cubic_state_cbs[c->state](cc, ev);
}
static void quic_cc_cubic_hystart_start_round(struct quic_cc *cc, uint64_t pn)
{
struct cubic *c = quic_cc_priv(cc);
struct quic_hystart *h = &c->hystart;
if (c->state != QUIC_CC_ST_SS && c->state != QUIC_CC_ST_CS)
return;
quic_cc_hystart_start_round(h, pn);
}
static void quic_cc_cubic_state_trace(struct buffer *buf, const struct quic_cc *cc)
{
struct quic_cc_path *path;
struct cubic *c = quic_cc_priv(cc);
path = container_of(cc, struct quic_cc_path, cc);
chunk_appendf(buf, " state=%s cwnd=%llu cwnd_last_max=%llu ssthresh=%d rpst=%dms",
quic_cc_state_str(c->state),
(unsigned long long)path->cwnd,
(unsigned long long)path->cwnd_last_max,
(int)c->ssthresh,
!tick_isset(c->recovery_start_time) ? -1 :
TICKS_TO_MS(tick_remain(c->recovery_start_time, now_ms)));
}
static void quic_cc_cubic_state_cli(struct buffer *buf, const struct quic_cc_path *path)
{
struct cubic *c = quic_cc_priv(&path->cc);
chunk_appendf(buf, " cc: state=%s ssthresh=%u K=%u last_w_max=%u wdiff=%lld\n",
quic_cc_state_str(c->state), c->ssthresh, c->K, c->last_w_max,
(long long)(path->cwnd - c->last_w_max));
}
struct quic_cc_algo quic_cc_algo_cubic = {
.type = QUIC_CC_ALGO_TP_CUBIC,
.flags = QUIC_CC_ALGO_FL_OPT_PACING,
.init = quic_cc_cubic_init,
.event = quic_cc_cubic_event,
.slow_start = quic_cc_cubic_slow_start,
.hystart_start_round = quic_cc_cubic_hystart_start_round,
.pacing_inter = quic_cc_default_pacing_inter,
.pacing_burst = NULL,
.state_trace = quic_cc_cubic_state_trace,
.state_cli = quic_cc_cubic_state_cli,
};
void quic_cc_cubic_check(void)
{
struct quic_cc *cc;
BUG_ON_HOT(sizeof(struct cubic) > sizeof(cc->priv));
}
INITCALL0(STG_REGISTER, quic_cc_cubic_check);
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