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John Heffner0e579762005-06-23 12:29:07 -07001/* Tom Kelly's Scalable TCP
2 *
Joe Perchesa52b8bd2009-02-24 16:40:16 -08003 * See http://www.deneholme.net/tom/scalable/
John Heffner0e579762005-06-23 12:29:07 -07004 *
5 * John Heffner <jheffner@sc.edu>
6 */
7
John Heffner0e579762005-06-23 12:29:07 -07008#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
Ilpo Järvinenc3a05c62007-12-02 00:47:59 +020018static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
John Heffner0e579762005-06-23 12:29:07 -070019{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030020 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemmingerf4805ed2005-11-10 16:53:30 -080021
22 if (!tcp_is_cwnd_limited(sk, in_flight))
John Heffner0e579762005-06-23 12:29:07 -070023 return;
24
Stephen Hemminger7faffa12005-11-10 17:07:24 -080025 if (tp->snd_cwnd <= tp->snd_ssthresh)
26 tcp_slow_start(tp);
Ilpo Järvinen758ce5c2009-02-28 04:44:37 +000027 else
28 tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT));
John Heffner0e579762005-06-23 12:29:07 -070029}
30
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030031static u32 tcp_scalable_ssthresh(struct sock *sk)
John Heffner0e579762005-06-23 12:29:07 -070032{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030033 const struct tcp_sock *tp = tcp_sk(sk);
John Heffner0e579762005-06-23 12:29:07 -070034 return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
35}
36
37
Stephen Hemmingera252beb2011-03-10 00:40:17 -080038static struct tcp_congestion_ops tcp_scalable __read_mostly = {
John Heffner0e579762005-06-23 12:29:07 -070039 .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");