[TCP]: Add Scalable TCP congestion control module.
[linux-2.6.git] / net / ipv4 / tcp_scalable.c
1 /* 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
8 #include <linux/config.h>
9 #include <linux/module.h>
10 #include <net/tcp.h>
11
12 /* These factors derived from the recommended values in the aer:
13  * .01 and and 7/8. We use 50 instead of 100 to account for
14  * delayed ack.
15  */
16 #define TCP_SCALABLE_AI_CNT     50U
17 #define TCP_SCALABLE_MD_SCALE   3
18
19 static void tcp_scalable_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt,
20                                     u32 in_flight, int flag)
21 {
22         if (in_flight < tp->snd_cwnd)
23                 return;
24
25         if (tp->snd_cwnd <= tp->snd_ssthresh) {
26                 tp->snd_cwnd++;
27         } else {
28                 tp->snd_cwnd_cnt++;
29                 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
30                         tp->snd_cwnd++;
31                         tp->snd_cwnd_cnt = 0;
32                 }
33         }
34         tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
35         tp->snd_cwnd_stamp = tcp_time_stamp;
36 }
37
38 static u32 tcp_scalable_ssthresh(struct tcp_sock *tp)
39 {
40         return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
41 }
42
43
44 static struct tcp_congestion_ops tcp_scalable = {
45         .ssthresh       = tcp_scalable_ssthresh,
46         .cong_avoid     = tcp_scalable_cong_avoid,
47         .min_cwnd       = tcp_reno_min_cwnd,
48
49         .owner          = THIS_MODULE,
50         .name           = "scalable",
51 };
52
53 static int __init tcp_scalable_register(void)
54 {
55         return tcp_register_congestion_control(&tcp_scalable);
56 }
57
58 static void __exit tcp_scalable_unregister(void)
59 {
60         tcp_unregister_congestion_control(&tcp_scalable);
61 }
62
63 module_init(tcp_scalable_register);
64 module_exit(tcp_scalable_unregister);
65
66 MODULE_AUTHOR("John Heffner");
67 MODULE_LICENSE("GPL");
68 MODULE_DESCRIPTION("Scalable TCP");