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, 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"); 70