109c434b8SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-only
2835b3f0cSDaniele Lacamera /*
3835b3f0cSDaniele Lacamera * TCP HYBLA
4835b3f0cSDaniele Lacamera *
5835b3f0cSDaniele Lacamera * TCP-HYBLA Congestion control algorithm, based on:
6835b3f0cSDaniele Lacamera * C.Caini, R.Firrincieli, "TCP-Hybla: A TCP Enhancement
7835b3f0cSDaniele Lacamera * for Heterogeneous Networks",
8835b3f0cSDaniele Lacamera * International Journal on satellite Communications,
9835b3f0cSDaniele Lacamera * September 2004
10835b3f0cSDaniele Lacamera * Daniele Lacamera
11835b3f0cSDaniele Lacamera * root at danielinux.net
12835b3f0cSDaniele Lacamera */
13835b3f0cSDaniele Lacamera
14835b3f0cSDaniele Lacamera #include <linux/module.h>
15835b3f0cSDaniele Lacamera #include <net/tcp.h>
16835b3f0cSDaniele Lacamera
17835b3f0cSDaniele Lacamera /* Tcp Hybla structure. */
18835b3f0cSDaniele Lacamera struct hybla {
19a2a385d6SEric Dumazet bool hybla_en;
20835b3f0cSDaniele Lacamera u32 snd_cwnd_cents; /* Keeps increment values when it is <1, <<7 */
21835b3f0cSDaniele Lacamera u32 rho; /* Rho parameter, integer part */
22835b3f0cSDaniele Lacamera u32 rho2; /* Rho * Rho, integer part */
23835b3f0cSDaniele Lacamera u32 rho_3ls; /* Rho parameter, <<3 */
24835b3f0cSDaniele Lacamera u32 rho2_7ls; /* Rho^2, <<7 */
25740b0f18SEric Dumazet u32 minrtt_us; /* Minimum smoothed round trip time value seen */
26835b3f0cSDaniele Lacamera };
27835b3f0cSDaniele Lacamera
28a2a385d6SEric Dumazet /* Hybla reference round trip time (default= 1/40 sec = 25 ms), in ms */
29835b3f0cSDaniele Lacamera static int rtt0 = 25;
30835b3f0cSDaniele Lacamera module_param(rtt0, int, 0644);
31835b3f0cSDaniele Lacamera MODULE_PARM_DESC(rtt0, "reference rout trip time (ms)");
32835b3f0cSDaniele Lacamera
33835b3f0cSDaniele Lacamera /* This is called to refresh values for hybla parameters */
hybla_recalc_param(struct sock * sk)346687e988SArnaldo Carvalho de Melo static inline void hybla_recalc_param (struct sock *sk)
35835b3f0cSDaniele Lacamera {
366687e988SArnaldo Carvalho de Melo struct hybla *ca = inet_csk_ca(sk);
37835b3f0cSDaniele Lacamera
38740b0f18SEric Dumazet ca->rho_3ls = max_t(u32,
39740b0f18SEric Dumazet tcp_sk(sk)->srtt_us / (rtt0 * USEC_PER_MSEC),
40740b0f18SEric Dumazet 8U);
41835b3f0cSDaniele Lacamera ca->rho = ca->rho_3ls >> 3;
42835b3f0cSDaniele Lacamera ca->rho2_7ls = (ca->rho_3ls * ca->rho_3ls) << 1;
43835b3f0cSDaniele Lacamera ca->rho2 = ca->rho2_7ls >> 7;
44835b3f0cSDaniele Lacamera }
45835b3f0cSDaniele Lacamera
hybla_init(struct sock * sk)466687e988SArnaldo Carvalho de Melo static void hybla_init(struct sock *sk)
47835b3f0cSDaniele Lacamera {
486687e988SArnaldo Carvalho de Melo struct tcp_sock *tp = tcp_sk(sk);
496687e988SArnaldo Carvalho de Melo struct hybla *ca = inet_csk_ca(sk);
50835b3f0cSDaniele Lacamera
51835b3f0cSDaniele Lacamera ca->rho = 0;
52835b3f0cSDaniele Lacamera ca->rho2 = 0;
53835b3f0cSDaniele Lacamera ca->rho_3ls = 0;
54835b3f0cSDaniele Lacamera ca->rho2_7ls = 0;
55835b3f0cSDaniele Lacamera ca->snd_cwnd_cents = 0;
56a2a385d6SEric Dumazet ca->hybla_en = true;
573308676eSEric Dumazet tcp_snd_cwnd_set(tp, 2);
58835b3f0cSDaniele Lacamera tp->snd_cwnd_clamp = 65535;
59835b3f0cSDaniele Lacamera
60835b3f0cSDaniele Lacamera /* 1st Rho measurement based on initial srtt */
616687e988SArnaldo Carvalho de Melo hybla_recalc_param(sk);
62835b3f0cSDaniele Lacamera
63835b3f0cSDaniele Lacamera /* set minimum rtt as this is the 1st ever seen */
64740b0f18SEric Dumazet ca->minrtt_us = tp->srtt_us;
653308676eSEric Dumazet tcp_snd_cwnd_set(tp, ca->rho);
66835b3f0cSDaniele Lacamera }
67835b3f0cSDaniele Lacamera
hybla_state(struct sock * sk,u8 ca_state)686687e988SArnaldo Carvalho de Melo static void hybla_state(struct sock *sk, u8 ca_state)
69835b3f0cSDaniele Lacamera {
706687e988SArnaldo Carvalho de Melo struct hybla *ca = inet_csk_ca(sk);
71a2a385d6SEric Dumazet
72835b3f0cSDaniele Lacamera ca->hybla_en = (ca_state == TCP_CA_Open);
73835b3f0cSDaniele Lacamera }
74835b3f0cSDaniele Lacamera
hybla_fraction(u32 odds)75835b3f0cSDaniele Lacamera static inline u32 hybla_fraction(u32 odds)
76835b3f0cSDaniele Lacamera {
77835b3f0cSDaniele Lacamera static const u32 fractions[] = {
78835b3f0cSDaniele Lacamera 128, 139, 152, 165, 181, 197, 215, 234,
79835b3f0cSDaniele Lacamera };
80835b3f0cSDaniele Lacamera
81835b3f0cSDaniele Lacamera return (odds < ARRAY_SIZE(fractions)) ? fractions[odds] : 128;
82835b3f0cSDaniele Lacamera }
83835b3f0cSDaniele Lacamera
84835b3f0cSDaniele Lacamera /* TCP Hybla main routine.
85835b3f0cSDaniele Lacamera * This is the algorithm behavior:
86835b3f0cSDaniele Lacamera * o Recalc Hybla parameters if min_rtt has changed
87835b3f0cSDaniele Lacamera * o Give cwnd a new value based on the model proposed
88835b3f0cSDaniele Lacamera * o remember increments <1
89835b3f0cSDaniele Lacamera */
hybla_cong_avoid(struct sock * sk,u32 ack,u32 acked)9024901551SEric Dumazet static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 acked)
91835b3f0cSDaniele Lacamera {
926687e988SArnaldo Carvalho de Melo struct tcp_sock *tp = tcp_sk(sk);
936687e988SArnaldo Carvalho de Melo struct hybla *ca = inet_csk_ca(sk);
94835b3f0cSDaniele Lacamera u32 increment, odd, rho_fractions;
95835b3f0cSDaniele Lacamera int is_slowstart = 0;
96835b3f0cSDaniele Lacamera
97835b3f0cSDaniele Lacamera /* Recalculate rho only if this srtt is the lowest */
98740b0f18SEric Dumazet if (tp->srtt_us < ca->minrtt_us) {
996687e988SArnaldo Carvalho de Melo hybla_recalc_param(sk);
100740b0f18SEric Dumazet ca->minrtt_us = tp->srtt_us;
101835b3f0cSDaniele Lacamera }
102835b3f0cSDaniele Lacamera
10324901551SEric Dumazet if (!tcp_is_cwnd_limited(sk))
104f4805edeSStephen Hemminger return;
105f4805edeSStephen Hemminger
106ab59859dSHarvey Harrison if (!ca->hybla_en) {
10724901551SEric Dumazet tcp_reno_cong_avoid(sk, ack, acked);
108ab59859dSHarvey Harrison return;
109ab59859dSHarvey Harrison }
110835b3f0cSDaniele Lacamera
111835b3f0cSDaniele Lacamera if (ca->rho == 0)
1126687e988SArnaldo Carvalho de Melo hybla_recalc_param(sk);
113835b3f0cSDaniele Lacamera
114835b3f0cSDaniele Lacamera rho_fractions = ca->rho_3ls - (ca->rho << 3);
115835b3f0cSDaniele Lacamera
11676174004SYuchung Cheng if (tcp_in_slow_start(tp)) {
117835b3f0cSDaniele Lacamera /*
118835b3f0cSDaniele Lacamera * slow start
119835b3f0cSDaniele Lacamera * INC = 2^RHO - 1
120835b3f0cSDaniele Lacamera * This is done by splitting the rho parameter
121835b3f0cSDaniele Lacamera * into 2 parts: an integer part and a fraction part.
122835b3f0cSDaniele Lacamera * Inrement<<7 is estimated by doing:
123835b3f0cSDaniele Lacamera * [2^(int+fract)]<<7
124835b3f0cSDaniele Lacamera * that is equal to:
125835b3f0cSDaniele Lacamera * (2^int) * [(2^fract) <<7]
126835b3f0cSDaniele Lacamera * 2^int is straightly computed as 1<<int,
127835b3f0cSDaniele Lacamera * while we will use hybla_slowstart_fraction_increment() to
128835b3f0cSDaniele Lacamera * calculate 2^fract in a <<7 value.
129835b3f0cSDaniele Lacamera */
130835b3f0cSDaniele Lacamera is_slowstart = 1;
131edafe502SDaniele Lacamera increment = ((1 << min(ca->rho, 16U)) *
132edafe502SDaniele Lacamera hybla_fraction(rho_fractions)) - 128;
133835b3f0cSDaniele Lacamera } else {
134835b3f0cSDaniele Lacamera /*
135835b3f0cSDaniele Lacamera * congestion avoidance
136835b3f0cSDaniele Lacamera * INC = RHO^2 / W
137835b3f0cSDaniele Lacamera * as long as increment is estimated as (rho<<7)/window
138835b3f0cSDaniele Lacamera * it already is <<7 and we can easily count its fractions.
139835b3f0cSDaniele Lacamera */
1403308676eSEric Dumazet increment = ca->rho2_7ls / tcp_snd_cwnd(tp);
141835b3f0cSDaniele Lacamera if (increment < 128)
142835b3f0cSDaniele Lacamera tp->snd_cwnd_cnt++;
143835b3f0cSDaniele Lacamera }
144835b3f0cSDaniele Lacamera
145835b3f0cSDaniele Lacamera odd = increment % 128;
1463308676eSEric Dumazet tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + (increment >> 7));
147835b3f0cSDaniele Lacamera ca->snd_cwnd_cents += odd;
148835b3f0cSDaniele Lacamera
149835b3f0cSDaniele Lacamera /* check when fractions goes >=128 and increase cwnd by 1. */
150835b3f0cSDaniele Lacamera while (ca->snd_cwnd_cents >= 128) {
1513308676eSEric Dumazet tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
152835b3f0cSDaniele Lacamera ca->snd_cwnd_cents -= 128;
153835b3f0cSDaniele Lacamera tp->snd_cwnd_cnt = 0;
154835b3f0cSDaniele Lacamera }
1559d2c27e1SDaniele Lacamera /* check when cwnd has not been incremented for a while */
1563308676eSEric Dumazet if (increment == 0 && odd == 0 && tp->snd_cwnd_cnt >= tcp_snd_cwnd(tp)) {
1573308676eSEric Dumazet tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
1589d2c27e1SDaniele Lacamera tp->snd_cwnd_cnt = 0;
1599d2c27e1SDaniele Lacamera }
160835b3f0cSDaniele Lacamera /* clamp down slowstart cwnd to ssthresh value. */
161835b3f0cSDaniele Lacamera if (is_slowstart)
1623308676eSEric Dumazet tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd(tp), tp->snd_ssthresh));
163835b3f0cSDaniele Lacamera
1643308676eSEric Dumazet tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd(tp), tp->snd_cwnd_clamp));
165835b3f0cSDaniele Lacamera }
166835b3f0cSDaniele Lacamera
167a252bebeSStephen Hemminger static struct tcp_congestion_ops tcp_hybla __read_mostly = {
168835b3f0cSDaniele Lacamera .init = hybla_init,
169835b3f0cSDaniele Lacamera .ssthresh = tcp_reno_ssthresh,
170e9799183SFlorian Westphal .undo_cwnd = tcp_reno_undo_cwnd,
171835b3f0cSDaniele Lacamera .cong_avoid = hybla_cong_avoid,
172835b3f0cSDaniele Lacamera .set_state = hybla_state,
173835b3f0cSDaniele Lacamera
174835b3f0cSDaniele Lacamera .owner = THIS_MODULE,
175835b3f0cSDaniele Lacamera .name = "hybla"
176835b3f0cSDaniele Lacamera };
177835b3f0cSDaniele Lacamera
hybla_register(void)178835b3f0cSDaniele Lacamera static int __init hybla_register(void)
179835b3f0cSDaniele Lacamera {
18074975d40SAlexey Dobriyan BUILD_BUG_ON(sizeof(struct hybla) > ICSK_CA_PRIV_SIZE);
181835b3f0cSDaniele Lacamera return tcp_register_congestion_control(&tcp_hybla);
182835b3f0cSDaniele Lacamera }
183835b3f0cSDaniele Lacamera
hybla_unregister(void)184835b3f0cSDaniele Lacamera static void __exit hybla_unregister(void)
185835b3f0cSDaniele Lacamera {
186835b3f0cSDaniele Lacamera tcp_unregister_congestion_control(&tcp_hybla);
187835b3f0cSDaniele Lacamera }
188835b3f0cSDaniele Lacamera
189835b3f0cSDaniele Lacamera module_init(hybla_register);
190835b3f0cSDaniele Lacamera module_exit(hybla_unregister);
191835b3f0cSDaniele Lacamera
192835b3f0cSDaniele Lacamera MODULE_AUTHOR("Daniele Lacamera");
193835b3f0cSDaniele Lacamera MODULE_LICENSE("GPL");
194835b3f0cSDaniele Lacamera MODULE_DESCRIPTION("TCP Hybla");
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