LXR linux/net/ipv4/tcp

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* Tom Kelly's Scalable TCP
   3 *
   4 * See http://www.deneholme.net/tom/scalable/
   5 *
   6 * John Heffner <jheffner@sc.edu>
   7 */
   8
   9#include <linux/module.h>
  10#include <net/tcp.h>
  11
  12/* These factors derived from the recommended values in the aer:
  13 * .01 and 7/8.
  14 */
  15#define TCP_SCALABLE_AI_CNT     100U
  16#define TCP_SCALABLE_MD_SCALE   3
  17
  18static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
  19{
  20        struct tcp_sock *tp = tcp_sk(sk);
  21
  22        if (!tcp_is_cwnd_limited(sk))
  23                return;
  24
  25        if (tcp_in_slow_start(tp)) {
  26                acked = tcp_slow_start(tp, acked);
  27                if (!acked)
  28                        return;
  29        }
  30        tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
  31                          acked);
  32}
  33
  34static u32 tcp_scalable_ssthresh(struct sock *sk)
  35{
  36        const struct tcp_sock *tp = tcp_sk(sk);
  37
  38        return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
  39}
  40
  41static struct tcp_congestion_ops tcp_scalable __read_mostly = {
  42        .ssthresh       = tcp_scalable_ssthresh,
  43        .undo_cwnd      = tcp_reno_undo_cwnd,
  44        .cong_avoid     = tcp_scalable_cong_avoid,
  45
  46        .owner          = THIS_MODULE,
  47        .name           = "scalable",
  48};
  49
  50static int __init tcp_scalable_register(void)
  51{
  52        return tcp_register_congestion_control(&tcp_scalable);
  53}
  54
  55static void __exit tcp_scalable_unregister(void)
  56{
  57        tcp_unregister_congestion_control(&tcp_scalable);
  58}
  59
  60module_init(tcp_scalable_register);
  61module_exit(tcp_scalable_unregister);
  62
  63MODULE_AUTHOR("John Heffner");
  64MODULE_LICENSE("GPL");
  65MODULE_DESCRIPTION("Scalable TCP");
  66