1 // SPDX-License-Identifier: GPL-2.0-only 1 // SPDX-License-Identifier: GPL-2.0-only
2 /* 2 /*
3 * TCP HYBLA 3 * TCP HYBLA
4 * 4 *
5 * TCP-HYBLA Congestion control algorithm, bas 5 * TCP-HYBLA Congestion control algorithm, based on:
6 * C.Caini, R.Firrincieli, "TCP-Hybla: A TCP 6 * C.Caini, R.Firrincieli, "TCP-Hybla: A TCP Enhancement
7 * for Heterogeneous Networks", 7 * for Heterogeneous Networks",
8 * International Journal on satellite Commun 8 * International Journal on satellite Communications,
9 * Septemb 9 * September 2004
10 * Daniele Lacamera 10 * Daniele Lacamera
11 * root at danielinux.net 11 * root at danielinux.net
12 */ 12 */
13 13
14 #include <linux/module.h> 14 #include <linux/module.h>
15 #include <net/tcp.h> 15 #include <net/tcp.h>
16 16
17 /* Tcp Hybla structure. */ 17 /* Tcp Hybla structure. */
18 struct hybla { 18 struct hybla {
19 bool hybla_en; 19 bool hybla_en;
20 u32 snd_cwnd_cents; /* Keeps increme 20 u32 snd_cwnd_cents; /* Keeps increment values when it is <1, <<7 */
21 u32 rho; /* Rho parameter 21 u32 rho; /* Rho parameter, integer part */
22 u32 rho2; /* Rho * Rho, in 22 u32 rho2; /* Rho * Rho, integer part */
23 u32 rho_3ls; /* Rho parameter 23 u32 rho_3ls; /* Rho parameter, <<3 */
24 u32 rho2_7ls; /* Rho^2, <<7 24 u32 rho2_7ls; /* Rho^2, <<7 */
25 u32 minrtt_us; /* Minimum smoot 25 u32 minrtt_us; /* Minimum smoothed round trip time value seen */
26 }; 26 };
27 27
28 /* Hybla reference round trip time (default= 1 28 /* Hybla reference round trip time (default= 1/40 sec = 25 ms), in ms */
29 static int rtt0 = 25; 29 static int rtt0 = 25;
30 module_param(rtt0, int, 0644); 30 module_param(rtt0, int, 0644);
31 MODULE_PARM_DESC(rtt0, "reference rout trip ti 31 MODULE_PARM_DESC(rtt0, "reference rout trip time (ms)");
32 32
33 /* This is called to refresh values for hybla 33 /* This is called to refresh values for hybla parameters */
34 static inline void hybla_recalc_param (struct 34 static inline void hybla_recalc_param (struct sock *sk)
35 { 35 {
36 struct hybla *ca = inet_csk_ca(sk); 36 struct hybla *ca = inet_csk_ca(sk);
37 37
38 ca->rho_3ls = max_t(u32, 38 ca->rho_3ls = max_t(u32,
39 tcp_sk(sk)->srtt_u 39 tcp_sk(sk)->srtt_us / (rtt0 * USEC_PER_MSEC),
40 8U); 40 8U);
41 ca->rho = ca->rho_3ls >> 3; 41 ca->rho = ca->rho_3ls >> 3;
42 ca->rho2_7ls = (ca->rho_3ls * ca->rho_ 42 ca->rho2_7ls = (ca->rho_3ls * ca->rho_3ls) << 1;
43 ca->rho2 = ca->rho2_7ls >> 7; 43 ca->rho2 = ca->rho2_7ls >> 7;
44 } 44 }
45 45
46 static void hybla_init(struct sock *sk) 46 static void hybla_init(struct sock *sk)
47 { 47 {
48 struct tcp_sock *tp = tcp_sk(sk); 48 struct tcp_sock *tp = tcp_sk(sk);
49 struct hybla *ca = inet_csk_ca(sk); 49 struct hybla *ca = inet_csk_ca(sk);
50 50
51 ca->rho = 0; 51 ca->rho = 0;
52 ca->rho2 = 0; 52 ca->rho2 = 0;
53 ca->rho_3ls = 0; 53 ca->rho_3ls = 0;
54 ca->rho2_7ls = 0; 54 ca->rho2_7ls = 0;
55 ca->snd_cwnd_cents = 0; 55 ca->snd_cwnd_cents = 0;
56 ca->hybla_en = true; 56 ca->hybla_en = true;
57 tcp_snd_cwnd_set(tp, 2); !! 57 tp->snd_cwnd = 2;
58 tp->snd_cwnd_clamp = 65535; 58 tp->snd_cwnd_clamp = 65535;
59 59
60 /* 1st Rho measurement based on initia 60 /* 1st Rho measurement based on initial srtt */
61 hybla_recalc_param(sk); 61 hybla_recalc_param(sk);
62 62
63 /* set minimum rtt as this is the 1st 63 /* set minimum rtt as this is the 1st ever seen */
64 ca->minrtt_us = tp->srtt_us; 64 ca->minrtt_us = tp->srtt_us;
65 tcp_snd_cwnd_set(tp, ca->rho); !! 65 tp->snd_cwnd = ca->rho;
66 } 66 }
67 67
68 static void hybla_state(struct sock *sk, u8 ca 68 static void hybla_state(struct sock *sk, u8 ca_state)
69 { 69 {
70 struct hybla *ca = inet_csk_ca(sk); 70 struct hybla *ca = inet_csk_ca(sk);
71 71
72 ca->hybla_en = (ca_state == TCP_CA_Ope 72 ca->hybla_en = (ca_state == TCP_CA_Open);
73 } 73 }
74 74
75 static inline u32 hybla_fraction(u32 odds) 75 static inline u32 hybla_fraction(u32 odds)
76 { 76 {
77 static const u32 fractions[] = { 77 static const u32 fractions[] = {
78 128, 139, 152, 165, 181, 197, 78 128, 139, 152, 165, 181, 197, 215, 234,
79 }; 79 };
80 80
81 return (odds < ARRAY_SIZE(fractions)) 81 return (odds < ARRAY_SIZE(fractions)) ? fractions[odds] : 128;
82 } 82 }
83 83
84 /* TCP Hybla main routine. 84 /* TCP Hybla main routine.
85 * This is the algorithm behavior: 85 * This is the algorithm behavior:
86 * o Recalc Hybla parameters if min_rtt ha 86 * o Recalc Hybla parameters if min_rtt has changed
87 * o Give cwnd a new value based on the mo 87 * o Give cwnd a new value based on the model proposed
88 * o remember increments <1 88 * o remember increments <1
89 */ 89 */
90 static void hybla_cong_avoid(struct sock *sk, 90 static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 acked)
91 { 91 {
92 struct tcp_sock *tp = tcp_sk(sk); 92 struct tcp_sock *tp = tcp_sk(sk);
93 struct hybla *ca = inet_csk_ca(sk); 93 struct hybla *ca = inet_csk_ca(sk);
94 u32 increment, odd, rho_fractions; 94 u32 increment, odd, rho_fractions;
95 int is_slowstart = 0; 95 int is_slowstart = 0;
96 96
97 /* Recalculate rho only if this srtt 97 /* Recalculate rho only if this srtt is the lowest */
98 if (tp->srtt_us < ca->minrtt_us) { 98 if (tp->srtt_us < ca->minrtt_us) {
99 hybla_recalc_param(sk); 99 hybla_recalc_param(sk);
100 ca->minrtt_us = tp->srtt_us; 100 ca->minrtt_us = tp->srtt_us;
101 } 101 }
102 102
103 if (!tcp_is_cwnd_limited(sk)) 103 if (!tcp_is_cwnd_limited(sk))
104 return; 104 return;
105 105
106 if (!ca->hybla_en) { 106 if (!ca->hybla_en) {
107 tcp_reno_cong_avoid(sk, ack, a 107 tcp_reno_cong_avoid(sk, ack, acked);
108 return; 108 return;
109 } 109 }
110 110
111 if (ca->rho == 0) 111 if (ca->rho == 0)
112 hybla_recalc_param(sk); 112 hybla_recalc_param(sk);
113 113
114 rho_fractions = ca->rho_3ls - (ca->rho 114 rho_fractions = ca->rho_3ls - (ca->rho << 3);
115 115
116 if (tcp_in_slow_start(tp)) { 116 if (tcp_in_slow_start(tp)) {
117 /* 117 /*
118 * slow start 118 * slow start
119 * INC = 2^RHO - 1 119 * INC = 2^RHO - 1
120 * This is done by splitting t 120 * This is done by splitting the rho parameter
121 * into 2 parts: an integer pa 121 * into 2 parts: an integer part and a fraction part.
122 * Inrement<<7 is estimated by 122 * Inrement<<7 is estimated by doing:
123 * [2^(int+fract)] 123 * [2^(int+fract)]<<7
124 * that is equal to: 124 * that is equal to:
125 * (2^int) * [(2 125 * (2^int) * [(2^fract) <<7]
126 * 2^int is straightly compute 126 * 2^int is straightly computed as 1<<int,
127 * while we will use hybla_slo 127 * while we will use hybla_slowstart_fraction_increment() to
128 * calculate 2^fract in a <<7 128 * calculate 2^fract in a <<7 value.
129 */ 129 */
130 is_slowstart = 1; 130 is_slowstart = 1;
131 increment = ((1 << min(ca->rho 131 increment = ((1 << min(ca->rho, 16U)) *
132 hybla_fraction(rho_fra 132 hybla_fraction(rho_fractions)) - 128;
133 } else { 133 } else {
134 /* 134 /*
135 * congestion avoidance 135 * congestion avoidance
136 * INC = RHO^2 / W 136 * INC = RHO^2 / W
137 * as long as increment is est 137 * as long as increment is estimated as (rho<<7)/window
138 * it already is <<7 and we ca 138 * it already is <<7 and we can easily count its fractions.
139 */ 139 */
140 increment = ca->rho2_7ls / tcp !! 140 increment = ca->rho2_7ls / tp->snd_cwnd;
141 if (increment < 128) 141 if (increment < 128)
142 tp->snd_cwnd_cnt++; 142 tp->snd_cwnd_cnt++;
143 } 143 }
144 144
145 odd = increment % 128; 145 odd = increment % 128;
146 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) !! 146 tp->snd_cwnd += increment >> 7;
147 ca->snd_cwnd_cents += odd; 147 ca->snd_cwnd_cents += odd;
148 148
149 /* check when fractions goes >=128 and 149 /* check when fractions goes >=128 and increase cwnd by 1. */
150 while (ca->snd_cwnd_cents >= 128) { 150 while (ca->snd_cwnd_cents >= 128) {
151 tcp_snd_cwnd_set(tp, tcp_snd_c !! 151 tp->snd_cwnd++;
152 ca->snd_cwnd_cents -= 128; 152 ca->snd_cwnd_cents -= 128;
153 tp->snd_cwnd_cnt = 0; 153 tp->snd_cwnd_cnt = 0;
154 } 154 }
155 /* check when cwnd has not been increm 155 /* check when cwnd has not been incremented for a while */
156 if (increment == 0 && odd == 0 && tp-> !! 156 if (increment == 0 && odd == 0 && tp->snd_cwnd_cnt >= tp->snd_cwnd) {
157 tcp_snd_cwnd_set(tp, tcp_snd_c !! 157 tp->snd_cwnd++;
158 tp->snd_cwnd_cnt = 0; 158 tp->snd_cwnd_cnt = 0;
159 } 159 }
160 /* clamp down slowstart cwnd to ssthre 160 /* clamp down slowstart cwnd to ssthresh value. */
161 if (is_slowstart) 161 if (is_slowstart)
162 tcp_snd_cwnd_set(tp, min(tcp_s !! 162 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
163 163
164 tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd( !! 164 tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
165 } 165 }
166 166
167 static struct tcp_congestion_ops tcp_hybla __r 167 static struct tcp_congestion_ops tcp_hybla __read_mostly = {
168 .init = hybla_init, 168 .init = hybla_init,
169 .ssthresh = tcp_reno_ssthresh, 169 .ssthresh = tcp_reno_ssthresh,
170 .undo_cwnd = tcp_reno_undo_cwnd, 170 .undo_cwnd = tcp_reno_undo_cwnd,
171 .cong_avoid = hybla_cong_avoid, 171 .cong_avoid = hybla_cong_avoid,
172 .set_state = hybla_state, 172 .set_state = hybla_state,
173 173
174 .owner = THIS_MODULE, 174 .owner = THIS_MODULE,
175 .name = "hybla" 175 .name = "hybla"
176 }; 176 };
177 177
178 static int __init hybla_register(void) 178 static int __init hybla_register(void)
179 { 179 {
180 BUILD_BUG_ON(sizeof(struct hybla) > IC 180 BUILD_BUG_ON(sizeof(struct hybla) > ICSK_CA_PRIV_SIZE);
181 return tcp_register_congestion_control 181 return tcp_register_congestion_control(&tcp_hybla);
182 } 182 }
183 183
184 static void __exit hybla_unregister(void) 184 static void __exit hybla_unregister(void)
185 { 185 {
186 tcp_unregister_congestion_control(&tcp 186 tcp_unregister_congestion_control(&tcp_hybla);
187 } 187 }
188 188
189 module_init(hybla_register); 189 module_init(hybla_register);
190 module_exit(hybla_unregister); 190 module_exit(hybla_unregister);
191 191
192 MODULE_AUTHOR("Daniele Lacamera"); 192 MODULE_AUTHOR("Daniele Lacamera");
193 MODULE_LICENSE("GPL"); 193 MODULE_LICENSE("GPL");
194 MODULE_DESCRIPTION("TCP Hybla"); 194 MODULE_DESCRIPTION("TCP Hybla");
195 195
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