tcp_scalable.c

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/* Tom Kelly's Scalable TCP
 *
 * See http://www.deneholme.net/tom/scalable/
 *
 * John Heffner <[email protected]>
 */

#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
        tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT));
}

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 __read_mostly = {
    .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");