linux/net/ipv4/tcp_scalable.c
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   1/* Tom Kelly's Scalable TCP
   2 *
   3 * See http://www.deneholme.net/tom/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                tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT));
  29}
  30
  31static u32 tcp_scalable_ssthresh(struct sock *sk)
  32{
  33        const struct tcp_sock *tp = tcp_sk(sk);
  34        return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
  35}
  36
  37
  38static struct tcp_congestion_ops tcp_scalable __read_mostly = {
  39        .ssthresh       = tcp_scalable_ssthresh,
  40        .cong_avoid     = tcp_scalable_cong_avoid,
  41        .min_cwnd       = tcp_reno_min_cwnd,
  42
  43        .owner          = THIS_MODULE,
  44        .name           = "scalable",
  45};
  46
  47static int __init tcp_scalable_register(void)
  48{
  49        return tcp_register_congestion_control(&tcp_scalable);
  50}
  51
  52static void __exit tcp_scalable_unregister(void)
  53{
  54        tcp_unregister_congestion_control(&tcp_scalable);
  55}
  56
  57module_init(tcp_scalable_register);
  58module_exit(tcp_scalable_unregister);
  59
  60MODULE_AUTHOR("John Heffner");
  61MODULE_LICENSE("GPL");
  62MODULE_DESCRIPTION("Scalable TCP");
  63
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