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
tcp_scalable_cong_avoid(struct sock * sk,u32 ack,u32 acked)18 static 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
tcp_scalable_ssthresh(struct sock * sk)34 static 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
41 static 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
tcp_scalable_register(void)50 static int __init tcp_scalable_register(void)
51 {
52 return tcp_register_congestion_control(&tcp_scalable);
53 }
54
tcp_scalable_unregister(void)55 static void __exit tcp_scalable_unregister(void)
56 {
57 tcp_unregister_congestion_control(&tcp_scalable);
58 }
59
60 module_init(tcp_scalable_register);
61 module_exit(tcp_scalable_unregister);
62
63 MODULE_AUTHOR("John Heffner");
64 MODULE_LICENSE("GPL");
65 MODULE_DESCRIPTION("Scalable TCP");
66