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0e57976b JH |
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 | ||
0e57976b JH |
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 | ||
6687e988 | 18 | static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 rtt, |
0e57976b JH |
19 | u32 in_flight, int flag) |
20 | { | |
6687e988 | 21 | struct tcp_sock *tp = tcp_sk(sk); |
f4805ede SH |
22 | |
23 | if (!tcp_is_cwnd_limited(sk, in_flight)) | |
0e57976b JH |
24 | return; |
25 | ||
7faffa1c SH |
26 | if (tp->snd_cwnd <= tp->snd_ssthresh) |
27 | tcp_slow_start(tp); | |
28 | else { | |
0e57976b JH |
29 | tp->snd_cwnd_cnt++; |
30 | if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){ | |
7faffa1c SH |
31 | if (tp->snd_cwnd < tp->snd_cwnd_clamp) |
32 | tp->snd_cwnd++; | |
0e57976b JH |
33 | tp->snd_cwnd_cnt = 0; |
34 | } | |
35 | } | |
0e57976b JH |
36 | } |
37 | ||
6687e988 | 38 | static u32 tcp_scalable_ssthresh(struct sock *sk) |
0e57976b | 39 | { |
6687e988 | 40 | const struct tcp_sock *tp = tcp_sk(sk); |
0e57976b JH |
41 | return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U); |
42 | } | |
43 | ||
44 | ||
45 | static 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 | ||
54 | static int __init tcp_scalable_register(void) | |
55 | { | |
56 | return tcp_register_congestion_control(&tcp_scalable); | |
57 | } | |
58 | ||
59 | static void __exit tcp_scalable_unregister(void) | |
60 | { | |
61 | tcp_unregister_congestion_control(&tcp_scalable); | |
62 | } | |
63 | ||
64 | module_init(tcp_scalable_register); | |
65 | module_exit(tcp_scalable_unregister); | |
66 | ||
67 | MODULE_AUTHOR("John Heffner"); | |
68 | MODULE_LICENSE("GPL"); | |
69 | MODULE_DESCRIPTION("Scalable TCP"); |