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 7/8. 14 */ 15 #define TCP_SCALABLE_AI_CNT 100U 16 #define TCP_SCALABLE_MD_SCALE 3 17 18 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked) 19 { 20 struct tcp_sock *tp = tcp_sk(sk); 21 22 if (!tcp_is_cwnd_limited(sk)) 23 return; 24 25 if (tcp_in_slow_start(tp)) { 26 acked = tcp_slow_start(tp, acked); 27 if (!acked) 28 return; 29 } 30 tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT), 31 acked); 32 } 33 34 static u32 tcp_scalable_ssthresh(struct sock *sk) 35 { 36 const struct tcp_sock *tp = tcp_sk(sk); 37 38 return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U); 39 } 40 41 static struct tcp_congestion_ops tcp_scalable __read_mostly = { 42 .ssthresh = tcp_scalable_ssthresh, 43 .undo_cwnd = tcp_reno_undo_cwnd, 44 .cong_avoid = tcp_scalable_cong_avoid, 45 46 .owner = THIS_MODULE, 47 .name = "scalable", 48 }; 49 50 static int __init tcp_scalable_register(void) 51 { 52 return tcp_register_congestion_control(&tcp_scalable); 53 } 54 55 static void __exit tcp_scalable_unregister(void) 56 { 57 tcp_unregister_congestion_control(&tcp_scalable); 58 } 59 60 module_init(tcp_scalable_register); 61 module_exit(tcp_scalable_unregister); 62 63 MODULE_AUTHOR("John Heffner"); 64 MODULE_LICENSE("GPL"); 65 MODULE_DESCRIPTION("Scalable TCP"); 66