LXR linux/net/ipv4/tcp

   1/* Tom Kelly's Scalable TCP
   2 *
   3 * See htt://www-lce.eng.cam.ac.uk/~ctk21/scalable/
   4 *
   5 * John Heffner <jheffner@sc.edu>
   6 */
   7
   8#include <linux/module.h>
   9#include <net/tcp.h>
  10
  11/* These factors derived from the recommended values in the aer:
  12 * .01 and and 7/8. We use 50 instead of 100 to account for
  13 * delayed ack.
  14 */
  15#define TCP_SCALABLE_AI_CNT     50U
  16#define TCP_SCALABLE_MD_SCALE   3
  17
  18static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
  19{
  20        struct tcp_sock *tp = tcp_sk(sk);
  21
  22        if (!tcp_is_cwnd_limited(sk, in_flight))
  23                return;
  24
  25        if (tp->snd_cwnd <= tp->snd_ssthresh)
  26                tcp_slow_start(tp);
  27        else {
  28                tp->snd_cwnd_cnt++;
  29                if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
  30                        if (tp->snd_cwnd < tp->snd_cwnd_clamp)
  31                                tp->snd_cwnd++;
  32                        tp->snd_cwnd_cnt = 0;
  33                }
  34        }
  35}
  36
  37static u32 tcp_scalable_ssthresh(struct sock *sk)
  38{
  39        const struct tcp_sock *tp = tcp_sk(sk);
  40        return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
  41}
  42
  43
  44static struct tcp_congestion_ops tcp_scalable = {
  45        .ssthresh       = tcp_scalable_ssthresh,
  46        .cong_avoid     = tcp_scalable_cong_avoid,
  47        .min_cwnd       = tcp_reno_min_cwnd,
  48
  49        .owner          = THIS_MODULE,
  50        .name           = "scalable",
  51};
  52
  53static int __init tcp_scalable_register(void)
  54{
  55        return tcp_register_congestion_control(&tcp_scalable);
  56}
  57
  58static void __exit tcp_scalable_unregister(void)
  59{
  60        tcp_unregister_congestion_control(&tcp_scalable);
  61}
  62
  63module_init(tcp_scalable_register);
  64module_exit(tcp_scalable_unregister);
  65
  66MODULE_AUTHOR("John Heffner");
  67MODULE_LICENSE("GPL");
  68MODULE_DESCRIPTION("Scalable TCP");
  69