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John Heffner0e579762005-06-23 12:29:07 -07001/* Tom Kelly's Scalable TCP
2 *
3 * See htt://www-lce.eng.cam.ac.uk/~ctk21/scalable/
4 *
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
Stephen Hemminger16751342007-07-16 18:35:52 -070018static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack,
John Heffner0e579762005-06-23 12:29:07 -070019 u32 in_flight, int flag)
20{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030021 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemmingerf4805ed2005-11-10 16:53:30 -080022
23 if (!tcp_is_cwnd_limited(sk, in_flight))
John Heffner0e579762005-06-23 12:29:07 -070024 return;
25
Stephen Hemminger7faffa12005-11-10 17:07:24 -080026 if (tp->snd_cwnd <= tp->snd_ssthresh)
27 tcp_slow_start(tp);
28 else {
John Heffner0e579762005-06-23 12:29:07 -070029 tp->snd_cwnd_cnt++;
30 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
Stephen Hemminger7faffa12005-11-10 17:07:24 -080031 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
32 tp->snd_cwnd++;
John Heffner0e579762005-06-23 12:29:07 -070033 tp->snd_cwnd_cnt = 0;
34 }
35 }
John Heffner0e579762005-06-23 12:29:07 -070036}
37
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030038static u32 tcp_scalable_ssthresh(struct sock *sk)
John Heffner0e579762005-06-23 12:29:07 -070039{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030040 const struct tcp_sock *tp = tcp_sk(sk);
John Heffner0e579762005-06-23 12:29:07 -070041 return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
42}
43
44
45static struct tcp_congestion_ops tcp_scalable = {
46 .ssthresh = tcp_scalable_ssthresh,
47 .cong_avoid = tcp_scalable_cong_avoid,
48 .min_cwnd = tcp_reno_min_cwnd,
49
50 .owner = THIS_MODULE,
51 .name = "scalable",
52};
53
54static int __init tcp_scalable_register(void)
55{
56 return tcp_register_congestion_control(&tcp_scalable);
57}
58
59static void __exit tcp_scalable_unregister(void)
60{
61 tcp_unregister_congestion_control(&tcp_scalable);
62}
63
64module_init(tcp_scalable_register);
65module_exit(tcp_scalable_unregister);
66
67MODULE_AUTHOR("John Heffner");
68MODULE_LICENSE("GPL");
69MODULE_DESCRIPTION("Scalable TCP");