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 in_flight) 19 { 20 struct tcp_sock *tp = tcp_sk(sk); 21 22 if (!tcp_is_cwnd_limited(sk, in_flight)) 23 return; 24 25 if (tp->snd_cwnd <= tp->snd_ssthresh) 26 tcp_slow_start(tp); 27 else { 28 tp->snd_cwnd_cnt++; 29 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){ 30 if (tp->snd_cwnd < tp->snd_cwnd_clamp) 31 tp->snd_cwnd++; 32 tp->snd_cwnd_cnt = 0; 33 } 34 } 35 } 36 37 static u32 tcp_scalable_ssthresh(struct sock *sk) 38 { 39 const struct tcp_sock *tp = tcp_sk(sk); 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"); 69