1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Tom Kelly's Scalable TCP 3 * 4 * See http://www.deneholme.net/tom/scalable/ 5 * 6 * John Heffner <jheffner@sc.edu> 7 */ 8 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 acked) 20 { 21 struct tcp_sock *tp = tcp_sk(sk); 22 23 if (!tcp_is_cwnd_limited(sk)) 24 return; 25 26 if (tcp_in_slow_start(tp)) 27 tcp_slow_start(tp, acked); 28 else 29 tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT), 30 1); 31 } 32 33 static u32 tcp_scalable_ssthresh(struct sock *sk) 34 { 35 const struct tcp_sock *tp = tcp_sk(sk); 36 37 return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U); 38 } 39 40 static struct tcp_congestion_ops tcp_scalable __read_mostly = { 41 .ssthresh = tcp_scalable_ssthresh, 42 .undo_cwnd = tcp_reno_undo_cwnd, 43 .cong_avoid = tcp_scalable_cong_avoid, 44 45 .owner = THIS_MODULE, 46 .name = "scalable", 47 }; 48 49 static int __init tcp_scalable_register(void) 50 { 51 return tcp_register_congestion_control(&tcp_scalable); 52 } 53 54 static void __exit tcp_scalable_unregister(void) 55 { 56 tcp_unregister_congestion_control(&tcp_scalable); 57 } 58 59 module_init(tcp_scalable_register); 60 module_exit(tcp_scalable_unregister); 61 62 MODULE_AUTHOR("John Heffner"); 63 MODULE_LICENSE("GPL"); 64 MODULE_DESCRIPTION("Scalable TCP"); 65