Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*

 * TCP HYBLA

 *

 * TCP-HYBLA Congestion control algorithm, based on:

 *   C.Caini, R.Firrincieli, "TCP-Hybla: A TCP Enhancement

 *   for Heterogeneous Networks",

 *   International Journal on satellite Communications,

 *                                     September 2004

 *    Daniele Lacamera

 *    root at danielinux.net

 */

#include <linux/module.h>

#include <net/tcp.h>

/* Tcp Hybla structure. */

struct hybla {

        u8    hybla_en;

        u32   snd_cwnd_cents; /* Keeps increment values when it is <1, <<7 */

        u32   rho;            /* Rho parameter, integer part  */

        u32   rho2;           /* Rho * Rho, integer part */

        u32   rho_3ls;        /* Rho parameter, <<3 */

        u32   rho2_7ls;       /* Rho^2, <<7     */

        u32   minrtt;         /* Minimum smoothed round trip time value seen */

};

/* Hybla reference round trip time (default= 1/40 sec = 25 ms),

   expressed in jiffies */

static int rtt0 = 25;

module_param(rtt0, int, 0644);

MODULE_PARM_DESC(rtt0, "reference rout trip time (ms)");

/* This is called to refresh values for hybla parameters */

static inline void hybla_recalc_param (struct sock *sk)

{

        struct hybla *ca = inet_csk_ca(sk);

        ca->rho_3ls = max_t(u32, tcp_sk(sk)->srtt / msecs_to_jiffies(rtt0), 8);

        ca->rho = ca->rho_3ls >> 3;

        ca->rho2_7ls = (ca->rho_3ls * ca->rho_3ls) << 1;

        ca->rho2 = ca->rho2_7ls >>7;

}

static void hybla_init(struct sock *sk)

{

        struct tcp_sock *tp = tcp_sk(sk);

        struct hybla *ca = inet_csk_ca(sk);

        ca->rho = 0;

        ca->rho2 = 0;

        ca->rho_3ls = 0;

        ca->rho2_7ls = 0;

        ca->snd_cwnd_cents = 0;

        ca->hybla_en = 1;

        tp->snd_cwnd = 2;

        tp->snd_cwnd_clamp = 65535;

        /* 1st Rho measurement based on initial srtt */

        hybla_recalc_param(sk);

        /* set minimum rtt as this is the 1st ever seen */

        ca->minrtt = tp->srtt;

        tp->snd_cwnd = ca->rho;

}

static void hybla_state(struct sock *sk, u8 ca_state)

{

        struct hybla *ca = inet_csk_ca(sk);

        ca->hybla_en = (ca_state == TCP_CA_Open);

}

static inline u32 hybla_fraction(u32 odds)

{

        static const u32 fractions[] = {

                128, 139, 152, 165, 181, 197, 215, 234,

        };

        return (odds < ARRAY_SIZE(fractions)) ? fractions[odds] : 128;

}

/* TCP Hybla main routine.

 * This is the algorithm behavior:

 *     o Recalc Hybla parameters if min_rtt has changed

 *     o Give cwnd a new value based on the model proposed

 *     o remember increments <1

 */

static void hybla_cong_avoid(struct sock *sk, u32 ack,

                            u32 in_flight, int flag)

{

        struct tcp_sock *tp = tcp_sk(sk);

        struct hybla *ca = inet_csk_ca(sk);

        u32 increment, odd, rho_fractions;

        int is_slowstart = 0;

        /*  Recalculate rho only if this srtt is the lowest */

        if (tp->srtt < ca->minrtt){

                hybla_recalc_param(sk);

                ca->minrtt = tp->srtt;

        }

        if (!tcp_is_cwnd_limited(sk, in_flight))

                return;

        if (!ca->hybla_en)

                return tcp_reno_cong_avoid(sk, ack, in_flight, flag);

        if (ca->rho == 0)

                hybla_recalc_param(sk);

        rho_fractions = ca->rho_3ls - (ca->rho << 3);

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

                /*

                 * slow start

                 *      INC = 2^RHO - 1

                 * This is done by splitting the rho parameter

                 * into 2 parts: an integer part and a fraction part.

                 * Inrement<<7 is estimated by doing:

                 *             [2^(int+fract)]<<7

                 * that is equal to:

                 *             (2^int)  *  [(2^fract) <<7]

                 * 2^int is straightly computed as 1<<int,

                 * while we will use hybla_slowstart_fraction_increment() to

                 * calculate 2^fract in a <<7 value.

                 */

                is_slowstart = 1;

                increment = ((1 << ca->rho) * hybla_fraction(rho_fractions))

                        - 128;

        } else {

                /*

                 * congestion avoidance

                 * INC = RHO^2 / W

                 * as long as increment is estimated as (rho<<7)/window

                 * it already is <<7 and we can easily count its fractions.

                 */

                increment = ca->rho2_7ls / tp->snd_cwnd;

                if (increment < 128)

                        tp->snd_cwnd_cnt++;

        }

        odd = increment % 128;

        tp->snd_cwnd += increment >> 7;

        ca->snd_cwnd_cents += odd;

        /* check when fractions goes >=128 and increase cwnd by 1. */

        while (ca->snd_cwnd_cents >= 128) {

                tp->snd_cwnd++;

                ca->snd_cwnd_cents -= 128;

                tp->snd_cwnd_cnt = 0;

        }

        /* clamp down slowstart cwnd to ssthresh value. */

        if (is_slowstart)

                tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);

        tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);

}

static struct tcp_congestion_ops tcp_hybla = {

        .init           = hybla_init,

        .ssthresh       = tcp_reno_ssthresh,

        .min_cwnd       = tcp_reno_min_cwnd,

        .cong_avoid     = hybla_cong_avoid,

        .set_state      = hybla_state,

        .owner          = THIS_MODULE,

        .name           = "hybla"

};

static int __init hybla_register(void)

{

        BUILD_BUG_ON(sizeof(struct hybla) > ICSK_CA_PRIV_SIZE);

        return tcp_register_congestion_control(&tcp_hybla);

}

static void __exit hybla_unregister(void)

{

        tcp_unregister_congestion_control(&tcp_hybla);

}

module_init(hybla_register);

module_exit(hybla_unregister);

MODULE_AUTHOR("Daniele Lacamera");

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("TCP Hybla");