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"); 69