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 (tp->snd_cwnd <= tp->snd_ssthresh)
 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");