Adding upstream version 2.9.5.upstream/2.9.5

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 542 insertions, 0 deletions

diff --git a/src/quic_cc_cubic.c b/src/quic_cc_cubic.c
new file mode 100644
index 0000000..76a62ac
--- /dev/null
+++ b/src/quic_cc_cubic.c
@@ -0,0 +1,542 @@
+#include <haproxy/quic_cc.h>
+#include <haproxy/quic_trace.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;
+};
+
+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;
+	TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
+}
+
+static int quic_cc_cubic_init(struct quic_cc *cc)
+{
+	quic_cc_cubic_reset(cc);
+	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 {
+			/* K value computing (in seconds):
+			 * K = cubic_root((W_max - cwnd_epoch)/C) (Figure 2)
+			 * Note that K is stored in milliseconds.
+			 */
+			c->K = cubic_root(((c->last_w_max - path->cwnd) << CUBIC_SCALE_FACTOR_SHIFT) / (CUBIC_C_SCALED * path->mtu));
+			/* Convert to miliseconds. */
+			c->K *= 1000;
+			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;
+	}
+
+	path->cwnd += inc;
+	path->cwnd = QUIC_MIN(path->max_cwnd, path->cwnd);
+	path->mcwnd = QUIC_MAX(path->cwnd, path->mcwnd);
+ 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;
+	path->cwnd =  QUIC_MAX(c->ssthresh, (uint32_t)path->min_cwnd);
+	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 (path->cwnd < QUIC_CC_INFINITE_SSTHESH - ev->ack.acked) {
+			path->cwnd += ev->ack.acked;
+			path->cwnd = QUIC_MIN(path->max_cwnd, path->cwnd);
+		}
+		/* Exit to congestion avoidance if slow start threshold is reached. */
+		if (path->cwnd >= c->ssthresh)
+			c->state = QUIC_CC_ST_CA;
+		path->mcwnd = QUIC_MAX(path->cwnd, path->mcwnd);
+		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)
+{
+	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:
+		quic_cubic_update(cc, ev->ack.acked);
+		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_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_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 mcwnd=%llu ssthresh=%d rpst=%dms",
+	              quic_cc_state_str(c->state),
+	              (unsigned long long)path->cwnd,
+	              (unsigned long long)path->mcwnd,
+	              (int)c->ssthresh,
+	              !tick_isset(c->recovery_start_time) ? -1 :
+	              TICKS_TO_MS(tick_remain(c->recovery_start_time, now_ms)));
+}
+
+struct quic_cc_algo quic_cc_algo_cubic = {
+	.type        = QUIC_CC_ALGO_TP_CUBIC,
+	.init        = quic_cc_cubic_init,
+	.event       = quic_cc_cubic_event,
+	.slow_start  = quic_cc_cubic_slow_start,
+	.state_trace = quic_cc_cubic_state_trace,
+};