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Linux/net/ipv4/tcp_highspeed.c

  1 /*
  2  * Sally Floyd's High Speed TCP (RFC 3649) congestion control
  3  *
  4  * See http://www.icir.org/floyd/hstcp.html
  5  *
  6  * John Heffner <jheffner@psc.edu>
  7  */
  8 
  9 #include <linux/module.h>
 10 #include <net/tcp.h>
 11 
 12 /* From AIMD tables from RFC 3649 appendix B,
 13  * with fixed-point MD scaled <<8.
 14  */
 15 static const struct hstcp_aimd_val {
 16         unsigned int cwnd;
 17         unsigned int md;
 18 } hstcp_aimd_vals[] = {
 19         {     38,  128, /*  0.50 */ },
 20         {    118,  112, /*  0.44 */ },
 21         {    221,  104, /*  0.41 */ },
 22         {    347,   98, /*  0.38 */ },
 23         {    495,   93, /*  0.37 */ },
 24         {    663,   89, /*  0.35 */ },
 25         {    851,   86, /*  0.34 */ },
 26         {   1058,   83, /*  0.33 */ },
 27         {   1284,   81, /*  0.32 */ },
 28         {   1529,   78, /*  0.31 */ },
 29         {   1793,   76, /*  0.30 */ },
 30         {   2076,   74, /*  0.29 */ },
 31         {   2378,   72, /*  0.28 */ },
 32         {   2699,   71, /*  0.28 */ },
 33         {   3039,   69, /*  0.27 */ },
 34         {   3399,   68, /*  0.27 */ },
 35         {   3778,   66, /*  0.26 */ },
 36         {   4177,   65, /*  0.26 */ },
 37         {   4596,   64, /*  0.25 */ },
 38         {   5036,   62, /*  0.25 */ },
 39         {   5497,   61, /*  0.24 */ },
 40         {   5979,   60, /*  0.24 */ },
 41         {   6483,   59, /*  0.23 */ },
 42         {   7009,   58, /*  0.23 */ },
 43         {   7558,   57, /*  0.22 */ },
 44         {   8130,   56, /*  0.22 */ },
 45         {   8726,   55, /*  0.22 */ },
 46         {   9346,   54, /*  0.21 */ },
 47         {   9991,   53, /*  0.21 */ },
 48         {  10661,   52, /*  0.21 */ },
 49         {  11358,   52, /*  0.20 */ },
 50         {  12082,   51, /*  0.20 */ },
 51         {  12834,   50, /*  0.20 */ },
 52         {  13614,   49, /*  0.19 */ },
 53         {  14424,   48, /*  0.19 */ },
 54         {  15265,   48, /*  0.19 */ },
 55         {  16137,   47, /*  0.19 */ },
 56         {  17042,   46, /*  0.18 */ },
 57         {  17981,   45, /*  0.18 */ },
 58         {  18955,   45, /*  0.18 */ },
 59         {  19965,   44, /*  0.17 */ },
 60         {  21013,   43, /*  0.17 */ },
 61         {  22101,   43, /*  0.17 */ },
 62         {  23230,   42, /*  0.17 */ },
 63         {  24402,   41, /*  0.16 */ },
 64         {  25618,   41, /*  0.16 */ },
 65         {  26881,   40, /*  0.16 */ },
 66         {  28193,   39, /*  0.16 */ },
 67         {  29557,   39, /*  0.15 */ },
 68         {  30975,   38, /*  0.15 */ },
 69         {  32450,   38, /*  0.15 */ },
 70         {  33986,   37, /*  0.15 */ },
 71         {  35586,   36, /*  0.14 */ },
 72         {  37253,   36, /*  0.14 */ },
 73         {  38992,   35, /*  0.14 */ },
 74         {  40808,   35, /*  0.14 */ },
 75         {  42707,   34, /*  0.13 */ },
 76         {  44694,   33, /*  0.13 */ },
 77         {  46776,   33, /*  0.13 */ },
 78         {  48961,   32, /*  0.13 */ },
 79         {  51258,   32, /*  0.13 */ },
 80         {  53677,   31, /*  0.12 */ },
 81         {  56230,   30, /*  0.12 */ },
 82         {  58932,   30, /*  0.12 */ },
 83         {  61799,   29, /*  0.12 */ },
 84         {  64851,   28, /*  0.11 */ },
 85         {  68113,   28, /*  0.11 */ },
 86         {  71617,   27, /*  0.11 */ },
 87         {  75401,   26, /*  0.10 */ },
 88         {  79517,   26, /*  0.10 */ },
 89         {  84035,   25, /*  0.10 */ },
 90         {  89053,   24, /*  0.10 */ },
 91 };
 92 
 93 #define HSTCP_AIMD_MAX  ARRAY_SIZE(hstcp_aimd_vals)
 94 
 95 struct hstcp {
 96         u32     ai;
 97 };
 98 
 99 static void hstcp_init(struct sock *sk)
100 {
101         struct tcp_sock *tp = tcp_sk(sk);
102         struct hstcp *ca = inet_csk_ca(sk);
103 
104         ca->ai = 0;
105 
106         /* Ensure the MD arithmetic works.  This is somewhat pedantic,
107          * since I don't think we will see a cwnd this large. :) */
108         tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
109 }
110 
111 static void hstcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
112 {
113         struct tcp_sock *tp = tcp_sk(sk);
114         struct hstcp *ca = inet_csk_ca(sk);
115 
116         if (!tcp_is_cwnd_limited(sk))
117                 return;
118 
119         if (tcp_in_slow_start(tp))
120                 tcp_slow_start(tp, acked);
121         else {
122                 /* Update AIMD parameters.
123                  *
124                  * We want to guarantee that:
125                  *     hstcp_aimd_vals[ca->ai-1].cwnd <
126                  *     snd_cwnd <=
127                  *     hstcp_aimd_vals[ca->ai].cwnd
128                  */
129                 if (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd) {
130                         while (tp->snd_cwnd > hstcp_aimd_vals[ca->ai].cwnd &&
131                                ca->ai < HSTCP_AIMD_MAX - 1)
132                                 ca->ai++;
133                 } else if (ca->ai && tp->snd_cwnd <= hstcp_aimd_vals[ca->ai-1].cwnd) {
134                         while (ca->ai && tp->snd_cwnd <= hstcp_aimd_vals[ca->ai-1].cwnd)
135                                 ca->ai--;
136                 }
137 
138                 /* Do additive increase */
139                 if (tp->snd_cwnd < tp->snd_cwnd_clamp) {
140                         /* cwnd = cwnd + a(w) / cwnd */
141                         tp->snd_cwnd_cnt += ca->ai + 1;
142                         if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
143                                 tp->snd_cwnd_cnt -= tp->snd_cwnd;
144                                 tp->snd_cwnd++;
145                         }
146                 }
147         }
148 }
149 
150 static u32 hstcp_ssthresh(struct sock *sk)
151 {
152         const struct tcp_sock *tp = tcp_sk(sk);
153         const struct hstcp *ca = inet_csk_ca(sk);
154 
155         /* Do multiplicative decrease */
156         return max(tp->snd_cwnd - ((tp->snd_cwnd * hstcp_aimd_vals[ca->ai].md) >> 8), 2U);
157 }
158 
159 
160 static struct tcp_congestion_ops tcp_highspeed __read_mostly = {
161         .init           = hstcp_init,
162         .ssthresh       = hstcp_ssthresh,
163         .cong_avoid     = hstcp_cong_avoid,
164 
165         .owner          = THIS_MODULE,
166         .name           = "highspeed"
167 };
168 
169 static int __init hstcp_register(void)
170 {
171         BUILD_BUG_ON(sizeof(struct hstcp) > ICSK_CA_PRIV_SIZE);
172         return tcp_register_congestion_control(&tcp_highspeed);
173 }
174 
175 static void __exit hstcp_unregister(void)
176 {
177         tcp_unregister_congestion_control(&tcp_highspeed);
178 }
179 
180 module_init(hstcp_register);
181 module_exit(hstcp_unregister);
182 
183 MODULE_AUTHOR("John Heffner");
184 MODULE_LICENSE("GPL");
185 MODULE_DESCRIPTION("High Speed TCP");
186 

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