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(tcp_snd_cwnd(tp), 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(tcp_snd_cwnd(tp) - (tcp_snd_cwnd(tp)>>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(type: &tcp_scalable);
53}
54
55static void __exit tcp_scalable_unregister(void)
56{
57 tcp_unregister_congestion_control(type: &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

source code of linux/net/ipv4/tcp_scalable.c