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
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 tcp_slow_start(tp, acked);
27 else
28 tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
29 1);
30 }
31
tcp_scalable_ssthresh(struct sock * sk)32 static u32 tcp_scalable_ssthresh(struct sock *sk)
33 {
34 const struct tcp_sock *tp = tcp_sk(sk);
35
36 return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
37 }
38
39 static struct tcp_congestion_ops tcp_scalable __read_mostly = {
40 .ssthresh = tcp_scalable_ssthresh,
41 .undo_cwnd = tcp_reno_undo_cwnd,
42 .cong_avoid = tcp_scalable_cong_avoid,
43
44 .owner = THIS_MODULE,
45 .name = "scalable",
46 };
47
tcp_scalable_register(void)48 static int __init tcp_scalable_register(void)
49 {
50 return tcp_register_congestion_control(&tcp_scalable);
51 }
52
tcp_scalable_unregister(void)53 static void __exit tcp_scalable_unregister(void)
54 {
55 tcp_unregister_congestion_control(&tcp_scalable);
56 }
57
58 module_init(tcp_scalable_register);
59 module_exit(tcp_scalable_unregister);
60
61 MODULE_AUTHOR("John Heffner");
62 MODULE_LICENSE("GPL");
63 MODULE_DESCRIPTION("Scalable TCP");
64
