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 struct scalable { 19 u32 loss_cwnd; 20 }; 21 22 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked) 23 { 24 struct tcp_sock *tp = tcp_sk(sk); 25 26 if (!tcp_is_cwnd_limited(sk)) 27 return; 28 29 if (tcp_in_slow_start(tp)) 30 tcp_slow_start(tp, acked); 31 else 32 tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT), 33 1); 34 } 35 36 static u32 tcp_scalable_ssthresh(struct sock *sk) 37 { 38 const struct tcp_sock *tp = tcp_sk(sk); 39 struct scalable *ca = inet_csk_ca(sk); 40 41 ca->loss_cwnd = tp->snd_cwnd; 42 43 return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U); 44 } 45 46 static u32 tcp_scalable_cwnd_undo(struct sock *sk) 47 { 48 const struct scalable *ca = inet_csk_ca(sk); 49 50 return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd); 51 } 52 53 static struct tcp_congestion_ops tcp_scalable __read_mostly = { 54 .ssthresh = tcp_scalable_ssthresh, 55 .undo_cwnd = tcp_scalable_cwnd_undo, 56 .cong_avoid = tcp_scalable_cong_avoid, 57 58 .owner = THIS_MODULE, 59 .name = "scalable", 60 }; 61 62 static int __init tcp_scalable_register(void) 63 { 64 return tcp_register_congestion_control(&tcp_scalable); 65 } 66 67 static void __exit tcp_scalable_unregister(void) 68 { 69 tcp_unregister_congestion_control(&tcp_scalable); 70 } 71 72 module_init(tcp_scalable_register); 73 module_exit(tcp_scalable_unregister); 74 75 MODULE_AUTHOR("John Heffner"); 76 MODULE_LICENSE("GPL"); 77 MODULE_DESCRIPTION("Scalable TCP"); 78