Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*

 * TCP Veno congestion control

 *

 * This is based on the congestion detection/avoidance scheme described in

 *    C. P. Fu, S. C. Liew.

 *    "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks."

 *    IEEE Journal on Selected Areas in Communication,

 *    Feb. 2003.

 *      See http://www.ntu.edu.sg/home5/ZHOU0022/papers/CPFu03a.pdf

 */

#include <linux/mm.h>

#include <linux/module.h>

#include <linux/skbuff.h>

#include <linux/inet_diag.h>

#include <net/tcp.h>

/* Default values of the Veno variables, in fixed-point representation

 * with V_PARAM_SHIFT bits to the right of the binary point.

 */

#define V_PARAM_SHIFT 1

static const int beta = 3 << V_PARAM_SHIFT;

/* Veno variables */

struct veno {

        u8 doing_veno_now;      /* if true, do veno for this rtt */

        u16 cntrtt;             /* # of rtts measured within last rtt */

        u32 minrtt;             /* min of rtts measured within last rtt (in usec) */

        u32 basertt;            /* the min of all Veno rtt measurements seen (in usec) */

        u32 inc;                /* decide whether to increase cwnd */

        u32 diff;               /* calculate the diff rate */

};

/* There are several situations when we must "re-start" Veno:

 *

 *  o when a connection is established

 *  o after an RTO

 *  o after fast recovery

 *  o when we send a packet and there is no outstanding

 *    unacknowledged data (restarting an idle connection)

 *

 */

static inline void veno_enable(struct sock *sk)

{

        struct veno *veno = inet_csk_ca(sk);

        /* turn on Veno */

        veno->doing_veno_now = 1;

        veno->minrtt = 0x7fffffff;

}

static inline void veno_disable(struct sock *sk)

{

        struct veno *veno = inet_csk_ca(sk);

        /* turn off Veno */

        veno->doing_veno_now = 0;

}

static void tcp_veno_init(struct sock *sk)

{

        struct veno *veno = inet_csk_ca(sk);

        veno->basertt = 0x7fffffff;

        veno->inc = 1;

        veno_enable(sk);

}

/* Do rtt sampling needed for Veno. */

static void tcp_veno_pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us)

{

        struct veno *veno = inet_csk_ca(sk);

        u32 vrtt;

        if (rtt_us < 0)

                return;

        /* Never allow zero rtt or baseRTT */

        vrtt = rtt_us + 1;

        /* Filter to find propagation delay: */

        if (vrtt < veno->basertt)

                veno->basertt = vrtt;

        /* Find the min rtt during the last rtt to find

         * the current prop. delay + queuing delay:

         */

        veno->minrtt = min(veno->minrtt, vrtt);

        veno->cntrtt++;

}

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

{

        if (ca_state == TCP_CA_Open)

                veno_enable(sk);

        else

                veno_disable(sk);

}

/*

 * If the connection is idle and we are restarting,

 * then we don't want to do any Veno calculations

 * until we get fresh rtt samples.  So when we

 * restart, we reset our Veno state to a clean

 * state. After we get acks for this flight of

 * packets, _then_ we can make Veno calculations

 * again.

 */

static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event)

{

        if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START)

                tcp_veno_init(sk);

}

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

                                u32 in_flight, int flag)

{

        struct tcp_sock *tp = tcp_sk(sk);

        struct veno *veno = inet_csk_ca(sk);

        if (!veno->doing_veno_now)

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

        /* limited by applications */

        if (!tcp_is_cwnd_limited(sk, in_flight))

                return;

        /* We do the Veno calculations only if we got enough rtt samples */

        if (veno->cntrtt <= 2) {

                /* We don't have enough rtt samples to do the Veno

                 * calculation, so we'll behave like Reno.

                 */

                tcp_reno_cong_avoid(sk, ack, in_flight, flag);

        } else {

                u32 rtt, target_cwnd;

                /* We have enough rtt samples, so, using the Veno

                 * algorithm, we determine the state of the network.

                 */

                rtt = veno->minrtt;

                target_cwnd = ((tp->snd_cwnd * veno->basertt)

                               << V_PARAM_SHIFT) / rtt;

                veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;

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

                        /* Slow start.  */

                        tcp_slow_start(tp);

                } else {

                        /* Congestion avoidance. */

                        if (veno->diff < beta) {

                                /* In the "non-congestive state", increase cwnd

                                 *  every rtt.

                                 */

                                if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {

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

                                                tp->snd_cwnd++;

                                        tp->snd_cwnd_cnt = 0;

                                } else

                                        tp->snd_cwnd_cnt++;

                        } else {

                                /* In the "congestive state", increase cwnd

                                 * every other rtt.

                                 */

                                if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {

                                        if (veno->inc

                                            && tp->snd_cwnd <

                                            tp->snd_cwnd_clamp) {

                                                tp->snd_cwnd++;

                                                veno->inc = 0;

                                        } else

                                                veno->inc = 1;

                                        tp->snd_cwnd_cnt = 0;

                                } else

                                        tp->snd_cwnd_cnt++;

                        }

                }

                if (tp->snd_cwnd < 2)

                        tp->snd_cwnd = 2;

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

                        tp->snd_cwnd = tp->snd_cwnd_clamp;

        }

        /* Wipe the slate clean for the next rtt. */

        /* veno->cntrtt = 0; */

        veno->minrtt = 0x7fffffff;

}

/* Veno MD phase */

static u32 tcp_veno_ssthresh(struct sock *sk)

{

        const struct tcp_sock *tp = tcp_sk(sk);

        struct veno *veno = inet_csk_ca(sk);

        if (veno->diff < beta)

                /* in "non-congestive state", cut cwnd by 1/5 */

                return max(tp->snd_cwnd * 4 / 5, 2U);

        else

                /* in "congestive state", cut cwnd by 1/2 */

                return max(tp->snd_cwnd >> 1U, 2U);

}

static struct tcp_congestion_ops tcp_veno = {

        .flags          = TCP_CONG_RTT_STAMP,

        .init           = tcp_veno_init,

        .ssthresh       = tcp_veno_ssthresh,

        .cong_avoid     = tcp_veno_cong_avoid,

        .pkts_acked     = tcp_veno_pkts_acked,

        .set_state      = tcp_veno_state,

        .cwnd_event     = tcp_veno_cwnd_event,

        .owner          = THIS_MODULE,

        .name           = "veno",

};

static int __init tcp_veno_register(void)

{

        BUILD_BUG_ON(sizeof(struct veno) > ICSK_CA_PRIV_SIZE);

        tcp_register_congestion_control(&tcp_veno);

        return 0;

}

static void __exit tcp_veno_unregister(void)

{

        tcp_unregister_congestion_control(&tcp_veno);

}

module_init(tcp_veno_register);

module_exit(tcp_veno_unregister);

MODULE_AUTHOR("Bin Zhou, Cheng Peng Fu");

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("TCP Veno");