/* Tom Kelly's Scalable TCP

 *

 *

 * 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

static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)

{

	struct tcp_sock *tp = tcp_sk(sk);

	if (!tcp_is_cwnd_limited(sk, in_flight))

		return;

	if (tp->snd_cwnd <= tp->snd_ssthresh)

		tcp_slow_start(tp);

	else {

		tp->snd_cwnd_cnt++;

		if (tp->snd_cwnd_cnt > min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT)){

			if (tp->snd_cwnd < tp->snd_cwnd_clamp)

				tp->snd_cwnd++;

			tp->snd_cwnd_cnt = 0;

		}

	}

}

static u32 tcp_scalable_ssthresh(struct sock *sk)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);

}

static struct tcp_congestion_ops tcp_scalable = {

	.ssthresh	= tcp_scalable_ssthresh,

	.cong_avoid	= tcp_scalable_cong_avoid,

	.min_cwnd	= tcp_reno_min_cwnd,

	.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");