summaryrefslogtreecommitdiffstats
path: root/net/ipv4/tcp_scalable.c
blob: f2123075ce6e1be4753e26bb1db81423e272caef (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
/* Tom Kelly's Scalable TCP
 *
 * See http://www.deneholme.net/tom/scalable/
 *
 * John Heffner <jheffner@sc.edu>
 */

#include <linux/module.h>
#include <net/tcp.h>

/* These factors derived from the recommended values in the aer:
 * .01 and and 7/8. We use 50 instead of 100 to account for
 * delayed ack.
 */
#define TCP_SCALABLE_AI_CNT	50U
#define TCP_SCALABLE_MD_SCALE	3

struct scalable {
	u32 loss_cwnd;
};

static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (!tcp_is_cwnd_limited(sk))
		return;

	if (tcp_in_slow_start(tp))
		tcp_slow_start(tp, acked);
	else
		tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
				  1);
}

static u32 tcp_scalable_ssthresh(struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);
	struct scalable *ca = inet_csk_ca(sk);

	ca->loss_cwnd = tp->snd_cwnd;

	return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
}

static u32 tcp_scalable_cwnd_undo(struct sock *sk)
{
	const struct scalable *ca = inet_csk_ca(sk);

	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
}

static struct tcp_congestion_ops tcp_scalable __read_mostly = {
	.ssthresh	= tcp_scalable_ssthresh,
	.undo_cwnd	= tcp_scalable_cwnd_undo,
	.cong_avoid	= tcp_scalable_cong_avoid,

	.owner		= THIS_MODULE,
	.name		= "scalable",
};

static int __init tcp_scalable_register(void)
{
	return tcp_register_congestion_control(&tcp_scalable);
}

static void __exit tcp_scalable_unregister(void)
{
	tcp_unregister_congestion_control(&tcp_scalable);
}

module_init(tcp_scalable_register);
module_exit(tcp_scalable_unregister);

MODULE_AUTHOR("John Heffner");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Scalable TCP");