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 sock *sk, u32 ack, u32 rtt, 20 u32 in_flight, int flag) 21 { 22 struct tcp_sock *tp = tcp_sk(sk); 23 24 if (!tcp_is_cwnd_limited(sk, in_flight)) 25 return; 26 27 if (tp->snd_cwnd <= tp->snd_ssthresh) 28 tcp_slow_start(tp); 29 else { 30 tp->snd_cwnd_cnt++; 31 if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){ 32 if (tp->snd_cwnd < tp->snd_cwnd_clamp) 33 tp->snd_cwnd++; 34 tp->snd_cwnd_cnt = 0; 35 } 36 } 37 } 38 39 static u32 tcp_scalable_ssthresh(struct sock *sk) 40 { 41 const struct tcp_sock *tp = tcp_sk(sk); 42 return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U); 43 } 44 45 46 static struct tcp_congestion_ops tcp_scalable = { 47 .ssthresh = tcp_scalable_ssthresh, 48 .cong_avoid = tcp_scalable_cong_avoid, 49 .min_cwnd = tcp_reno_min_cwnd, 50 51 .owner = THIS_MODULE, 52 .name = "scalable", 53 }; 54 55 static int __init tcp_scalable_register(void) 56 { 57 return tcp_register_congestion_control(&tcp_scalable); 58 } 59 60 static void __exit tcp_scalable_unregister(void) 61 { 62 tcp_unregister_congestion_control(&tcp_scalable); 63 } 64 65 module_init(tcp_scalable_register); 66 module_exit(tcp_scalable_unregister); 67 68 MODULE_AUTHOR("John Heffner"); 69 MODULE_LICENSE("GPL"); 70 MODULE_DESCRIPTION("Scalable TCP"); 71