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/* Tom Kelly's Scalable TCP
*
* See http://www.deneholme.net/tom/scalable/
*
* John Heffner <jheffner@sc.edu>
*/
#include <linux/module.h>
#include <net/tcp.h>
/* These factors derived from the recommended values in the aer:
* .01 and and 7/8. We use 50 instead of 100 to account for
* delayed ack.
*/
#define TCP_SCALABLE_AI_CNT 50U
#define TCP_SCALABLE_MD_SCALE 3
struct scalable {
u32 loss_cwnd;
};
static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
{
struct tcp_sock *tp = tcp_sk(sk);
if (!tcp_is_cwnd_limited(sk))
return;
if (tcp_in_slow_start(tp))
tcp_slow_start(tp, acked);
else
tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
1);
}
static u32 tcp_scalable_ssthresh(struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
struct scalable *ca = inet_csk_ca(sk);
ca->loss_cwnd = tp->snd_cwnd;
return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
}
static u32 tcp_scalable_cwnd_undo(struct sock *sk)
{
const struct scalable *ca = inet_csk_ca(sk);
return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
}
static struct tcp_congestion_ops tcp_scalable __read_mostly = {
.ssthresh = tcp_scalable_ssthresh,
.undo_cwnd = tcp_scalable_cwnd_undo,
.cong_avoid = tcp_scalable_cong_avoid,
.owner = THIS_MODULE,
.name = "scalable",
};
static int __init tcp_scalable_register(void)
{
return tcp_register_congestion_control(&tcp_scalable);
}
static void __exit tcp_scalable_unregister(void)
{
tcp_unregister_congestion_control(&tcp_scalable);
}
module_init(tcp_scalable_register);
module_exit(tcp_scalable_unregister);
MODULE_AUTHOR("John Heffner");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Scalable TCP");
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