[TCP]: rare bad TCP checksum with 2.6.19
[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/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
18 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
19                                     u32 in_flight, int flag)
20 {
21         struct tcp_sock *tp = tcp_sk(sk);
22
23         if (!tcp_is_cwnd_limited(sk, in_flight))
24                 return;
25
26         if (tp->snd_cwnd <= tp->snd_ssthresh)
27                 tcp_slow_start(tp);
28         else {
29                 tp->snd_cwnd_cnt++;
30                 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){
31                         if (tp->snd_cwnd < tp->snd_cwnd_clamp)
32                                 tp->snd_cwnd++;
33                         tp->snd_cwnd_cnt = 0;
34                 }
35         }
36 }
37
38 static u32 tcp_scalable_ssthresh(struct sock *sk)
39 {
40         const struct tcp_sock *tp = tcp_sk(sk);
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");