1 /* Tom Kelly's Scalable TCP 2 * 3 * See http://www.deneholme.net/tom/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 tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)); 29 } 30 31 static u32 tcp_scalable_ssthresh(struct sock *sk) 32 { 33 const struct tcp_sock *tp = tcp_sk(sk); 34 return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U); 35 } 36 37 38 static struct tcp_congestion_ops tcp_scalable __read_mostly = { 39 .ssthresh = tcp_scalable_ssthresh, 40 .cong_avoid = tcp_scalable_cong_avoid, 41 .min_cwnd = tcp_reno_min_cwnd, 42 43 .owner = THIS_MODULE, 44 .name = "scalable", 45 }; 46 47 static int __init tcp_scalable_register(void) 48 { 49 return tcp_register_congestion_control(&tcp_scalable); 50 } 51 52 static void __exit tcp_scalable_unregister(void) 53 { 54 tcp_unregister_congestion_control(&tcp_scalable); 55 } 56 57 module_init(tcp_scalable_register); 58 module_exit(tcp_scalable_unregister); 59 60 MODULE_AUTHOR("John Heffner"); 61 MODULE_LICENSE("GPL"); 62 MODULE_DESCRIPTION("Scalable TCP"); 63