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-rw-r--r--net/ipv4/tcp_hybla.c194
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diff --git a/net/ipv4/tcp_hybla.c b/net/ipv4/tcp_hybla.c
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+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * TCP HYBLA
+ *
+ * TCP-HYBLA Congestion control algorithm, based on:
+ * C.Caini, R.Firrincieli, "TCP-Hybla: A TCP Enhancement
+ * for Heterogeneous Networks",
+ * International Journal on satellite Communications,
+ * September 2004
+ * Daniele Lacamera
+ * root at danielinux.net
+ */
+
+#include <linux/module.h>
+#include <net/tcp.h>
+
+/* Tcp Hybla structure. */
+struct hybla {
+ bool hybla_en;
+ u32 snd_cwnd_cents; /* Keeps increment values when it is <1, <<7 */
+ u32 rho; /* Rho parameter, integer part */
+ u32 rho2; /* Rho * Rho, integer part */
+ u32 rho_3ls; /* Rho parameter, <<3 */
+ u32 rho2_7ls; /* Rho^2, <<7 */
+ u32 minrtt_us; /* Minimum smoothed round trip time value seen */
+};
+
+/* Hybla reference round trip time (default= 1/40 sec = 25 ms), in ms */
+static int rtt0 = 25;
+module_param(rtt0, int, 0644);
+MODULE_PARM_DESC(rtt0, "reference rout trip time (ms)");
+
+/* This is called to refresh values for hybla parameters */
+static inline void hybla_recalc_param (struct sock *sk)
+{
+ struct hybla *ca = inet_csk_ca(sk);
+
+ ca->rho_3ls = max_t(u32,
+ tcp_sk(sk)->srtt_us / (rtt0 * USEC_PER_MSEC),
+ 8U);
+ ca->rho = ca->rho_3ls >> 3;
+ ca->rho2_7ls = (ca->rho_3ls * ca->rho_3ls) << 1;
+ ca->rho2 = ca->rho2_7ls >> 7;
+}
+
+static void hybla_init(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct hybla *ca = inet_csk_ca(sk);
+
+ ca->rho = 0;
+ ca->rho2 = 0;
+ ca->rho_3ls = 0;
+ ca->rho2_7ls = 0;
+ ca->snd_cwnd_cents = 0;
+ ca->hybla_en = true;
+ tcp_snd_cwnd_set(tp, 2);
+ tp->snd_cwnd_clamp = 65535;
+
+ /* 1st Rho measurement based on initial srtt */
+ hybla_recalc_param(sk);
+
+ /* set minimum rtt as this is the 1st ever seen */
+ ca->minrtt_us = tp->srtt_us;
+ tcp_snd_cwnd_set(tp, ca->rho);
+}
+
+static void hybla_state(struct sock *sk, u8 ca_state)
+{
+ struct hybla *ca = inet_csk_ca(sk);
+
+ ca->hybla_en = (ca_state == TCP_CA_Open);
+}
+
+static inline u32 hybla_fraction(u32 odds)
+{
+ static const u32 fractions[] = {
+ 128, 139, 152, 165, 181, 197, 215, 234,
+ };
+
+ return (odds < ARRAY_SIZE(fractions)) ? fractions[odds] : 128;
+}
+
+/* TCP Hybla main routine.
+ * This is the algorithm behavior:
+ * o Recalc Hybla parameters if min_rtt has changed
+ * o Give cwnd a new value based on the model proposed
+ * o remember increments <1
+ */
+static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 acked)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct hybla *ca = inet_csk_ca(sk);
+ u32 increment, odd, rho_fractions;
+ int is_slowstart = 0;
+
+ /* Recalculate rho only if this srtt is the lowest */
+ if (tp->srtt_us < ca->minrtt_us) {
+ hybla_recalc_param(sk);
+ ca->minrtt_us = tp->srtt_us;
+ }
+
+ if (!tcp_is_cwnd_limited(sk))
+ return;
+
+ if (!ca->hybla_en) {
+ tcp_reno_cong_avoid(sk, ack, acked);
+ return;
+ }
+
+ if (ca->rho == 0)
+ hybla_recalc_param(sk);
+
+ rho_fractions = ca->rho_3ls - (ca->rho << 3);
+
+ if (tcp_in_slow_start(tp)) {
+ /*
+ * slow start
+ * INC = 2^RHO - 1
+ * This is done by splitting the rho parameter
+ * into 2 parts: an integer part and a fraction part.
+ * Inrement<<7 is estimated by doing:
+ * [2^(int+fract)]<<7
+ * that is equal to:
+ * (2^int) * [(2^fract) <<7]
+ * 2^int is straightly computed as 1<<int,
+ * while we will use hybla_slowstart_fraction_increment() to
+ * calculate 2^fract in a <<7 value.
+ */
+ is_slowstart = 1;
+ increment = ((1 << min(ca->rho, 16U)) *
+ hybla_fraction(rho_fractions)) - 128;
+ } else {
+ /*
+ * congestion avoidance
+ * INC = RHO^2 / W
+ * as long as increment is estimated as (rho<<7)/window
+ * it already is <<7 and we can easily count its fractions.
+ */
+ increment = ca->rho2_7ls / tcp_snd_cwnd(tp);
+ if (increment < 128)
+ tp->snd_cwnd_cnt++;
+ }
+
+ odd = increment % 128;
+ tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + (increment >> 7));
+ ca->snd_cwnd_cents += odd;
+
+ /* check when fractions goes >=128 and increase cwnd by 1. */
+ while (ca->snd_cwnd_cents >= 128) {
+ tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
+ ca->snd_cwnd_cents -= 128;
+ tp->snd_cwnd_cnt = 0;
+ }
+ /* check when cwnd has not been incremented for a while */
+ if (increment == 0 && odd == 0 && tp->snd_cwnd_cnt >= tcp_snd_cwnd(tp)) {
+ tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
+ tp->snd_cwnd_cnt = 0;
+ }
+ /* clamp down slowstart cwnd to ssthresh value. */
+ if (is_slowstart)
+ tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd(tp), tp->snd_ssthresh));
+
+ tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd(tp), tp->snd_cwnd_clamp));
+}
+
+static struct tcp_congestion_ops tcp_hybla __read_mostly = {
+ .init = hybla_init,
+ .ssthresh = tcp_reno_ssthresh,
+ .undo_cwnd = tcp_reno_undo_cwnd,
+ .cong_avoid = hybla_cong_avoid,
+ .set_state = hybla_state,
+
+ .owner = THIS_MODULE,
+ .name = "hybla"
+};
+
+static int __init hybla_register(void)
+{
+ BUILD_BUG_ON(sizeof(struct hybla) > ICSK_CA_PRIV_SIZE);
+ return tcp_register_congestion_control(&tcp_hybla);
+}
+
+static void __exit hybla_unregister(void)
+{
+ tcp_unregister_congestion_control(&tcp_hybla);
+}
+
+module_init(hybla_register);
+module_exit(hybla_unregister);
+
+MODULE_AUTHOR("Daniele Lacamera");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP Hybla");