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