/* $NetBSD: ieee80211_rssadapt.c,v 1.9 2005/02/26 22:45:09 perry Exp $ */
/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2010 Rui Paulo <rpaulo@FreeBSD.org>
 * Copyright (c) 2003, 2004 David Young.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above
 *    copyright notice, this list of conditions and the following
 *    disclaimer in the documentation and/or other materials provided
 *    with the distribution.
 * 3. The name of David Young may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY David Young ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL David
 * Young BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 */
#include "opt_wlan.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/socket.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_media.h>
#include <net/ethernet.h>

#include <net80211/ieee80211_var.h>
#include <net80211/ieee80211_rssadapt.h>
#include <net80211/ieee80211_ratectl.h>

struct rssadapt_expavgctl {
        /* RSS threshold decay. */
        u_int rc_decay_denom;
        u_int rc_decay_old;
        /* RSS threshold update. */
        u_int rc_thresh_denom;
        u_int rc_thresh_old;
        /* RSS average update. */
        u_int rc_avgrssi_denom;
        u_int rc_avgrssi_old;
};

static struct rssadapt_expavgctl master_expavgctl = {
        .rc_decay_denom = 16,
        .rc_decay_old = 15,
        .rc_thresh_denom = 8,
        .rc_thresh_old = 4,
        .rc_avgrssi_denom = 8,
        .rc_avgrssi_old = 4
};

#ifdef interpolate
#undef interpolate
#endif
#define interpolate(parm, old, new) ((parm##_old * (old) + \
                                     (parm##_denom - parm##_old) * (new)) / \
                                    parm##_denom)

static void     rssadapt_setinterval(const struct ieee80211vap *, int);
static void     rssadapt_init(struct ieee80211vap *);
static void     rssadapt_deinit(struct ieee80211vap *);
static void     rssadapt_updatestats(struct ieee80211_rssadapt_node *);
static void     rssadapt_node_init(struct ieee80211_node *);
static void     rssadapt_node_deinit(struct ieee80211_node *);
static int      rssadapt_rate(struct ieee80211_node *, void *, uint32_t);
static void     rssadapt_lower_rate(struct ieee80211_rssadapt_node *, int, int);
static void     rssadapt_raise_rate(struct ieee80211_rssadapt_node *,
                        int, int);
static void     rssadapt_tx_complete(const struct ieee80211_node *,
                        const struct ieee80211_ratectl_tx_status *);
static void     rssadapt_sysctlattach(struct ieee80211vap *,
                        struct sysctl_ctx_list *, struct sysctl_oid *);

/* number of references from net80211 layer */
static  int nrefs = 0;

static const struct ieee80211_ratectl rssadapt = {
        .ir_name        = "rssadapt",
        .ir_attach      = NULL,
        .ir_detach      = NULL,
        .ir_init        = rssadapt_init,
        .ir_deinit      = rssadapt_deinit,
        .ir_node_init   = rssadapt_node_init,
        .ir_node_deinit = rssadapt_node_deinit,
        .ir_rate        = rssadapt_rate,
        .ir_tx_complete = rssadapt_tx_complete,
        .ir_tx_update   = NULL,
        .ir_setinterval = rssadapt_setinterval,
};
IEEE80211_RATECTL_MODULE(rssadapt, 1);
IEEE80211_RATECTL_ALG(rssadapt, IEEE80211_RATECTL_RSSADAPT, rssadapt);

static void
rssadapt_setinterval(const struct ieee80211vap *vap, int msecs)
{
        struct ieee80211_rssadapt *rs = vap->iv_rs;

        if (!rs)
                return;

        if (msecs < 100)
                msecs = 100;
        rs->interval = msecs_to_ticks(msecs);
}

static void
rssadapt_init(struct ieee80211vap *vap)
{
        struct ieee80211_rssadapt *rs;

        KASSERT(vap->iv_rs == NULL, ("%s: iv_rs already initialized",
            __func__));

        nrefs++;                /* XXX locking */
        vap->iv_rs = rs = IEEE80211_MALLOC(sizeof(struct ieee80211_rssadapt),
            M_80211_RATECTL, IEEE80211_M_NOWAIT | IEEE80211_M_ZERO);
        if (rs == NULL) {
                net80211_vap_printf(vap, "couldn't alloc ratectl structure\n");
                return;
        }
        rs->vap = vap;
        rssadapt_setinterval(vap, 500 /* msecs */);
        rssadapt_sysctlattach(vap, vap->iv_sysctl, vap->iv_oid);
}

static void
rssadapt_deinit(struct ieee80211vap *vap)
{
        IEEE80211_FREE(vap->iv_rs, M_80211_RATECTL);
        KASSERT(nrefs > 0, ("imbalanced attach/detach"));
        nrefs--;                /* XXX locking */
}

static void
rssadapt_updatestats(struct ieee80211_rssadapt_node *ra)
{
        long interval;

        ra->ra_pktrate = (ra->ra_pktrate + 10*(ra->ra_nfail + ra->ra_nok))/2;
        ra->ra_nfail = ra->ra_nok = 0;

        /*
         * A node is eligible for its rate to be raised every 1/10 to 10
         * seconds, more eligible in proportion to recent packet rates.
         */
        interval = MAX(10*1000, 10*1000 / MAX(1, 10 * ra->ra_pktrate));
        ra->ra_raise_interval = msecs_to_ticks(interval);
}

static void
rssadapt_node_init(struct ieee80211_node *ni)
{
        struct ieee80211_rssadapt_node *ra;
        struct ieee80211vap *vap = ni->ni_vap;
        struct ieee80211_rssadapt *rsa = vap->iv_rs;
        const struct ieee80211_rateset *rs = &ni->ni_rates;

        if (!rsa) {
                net80211_vap_printf(vap,
                    "ratectl structure was not allocated, "
                    "per-node structure allocation skipped\n");
                return;
        }

        if (ni->ni_rctls == NULL) {
                ni->ni_rctls = ra = 
                    IEEE80211_MALLOC(sizeof(struct ieee80211_rssadapt_node),
                        M_80211_RATECTL, IEEE80211_M_NOWAIT | IEEE80211_M_ZERO);
                if (ra == NULL) {
                        net80211_vap_printf(vap,
                            "couldn't alloc per-node ratectl structure\n");
                        return;
                }
        } else
                ra = ni->ni_rctls;
        ra->ra_rs = rsa;
        ra->ra_rates = *rs;
        rssadapt_updatestats(ra);

        /* pick initial rate */
        for (ra->ra_rix = rs->rs_nrates - 1;
             ra->ra_rix > 0 && (rs->rs_rates[ra->ra_rix] & IEEE80211_RATE_VAL) > 72;
             ra->ra_rix--)
                ;
        ieee80211_node_set_txrate_dot11rate(ni,
            rs->rs_rates[ra->ra_rix] & IEEE80211_RATE_VAL);
        ra->ra_ticks = ticks;

        IEEE80211_NOTE(ni->ni_vap, IEEE80211_MSG_RATECTL, ni,
            "RSSADAPT initial rate %d Mbit/s",
            ieee80211_node_get_txrate_kbit(ni) / 1000);
}

static void
rssadapt_node_deinit(struct ieee80211_node *ni)
{

        IEEE80211_FREE(ni->ni_rctls, M_80211_RATECTL);
}

static __inline int
bucket(int pktlen)
{
        int i, top, thridx;

        for (i = 0, top = IEEE80211_RSSADAPT_BKT0;
             i < IEEE80211_RSSADAPT_BKTS;
             i++, top <<= IEEE80211_RSSADAPT_BKTPOWER) {
                thridx = i;
                if (pktlen <= top)
                        break;
        }
        return thridx;
}

static int
rssadapt_rate(struct ieee80211_node *ni, void *arg __unused, uint32_t iarg)
{
        struct ieee80211_rssadapt_node *ra = ni->ni_rctls;
        u_int pktlen = iarg;
        const struct ieee80211_rateset *rs;
        uint16_t (*thrs)[IEEE80211_RATE_SIZE];
        int rix, rssi;

        /* XXX should return -1 here, but drivers may not expect this... */
        if (!ra)
        {
                ieee80211_node_set_txrate_dot11rate(ni,
                    ni->ni_rates.rs_rates[0]);
                return 0;
        }

        rs = &ra->ra_rates;
        if ((ticks - ra->ra_ticks) > ra->ra_rs->interval) {
                rssadapt_updatestats(ra);
                ra->ra_ticks = ticks;
        }

        thrs = &ra->ra_rate_thresh[bucket(pktlen)];

        /* XXX this is average rssi, should be using last value */
        rssi = ni->ni_ic->ic_node_getrssi(ni);
        for (rix = rs->rs_nrates-1; rix >= 0; rix--)
                if ((*thrs)[rix] < (rssi << 8))
                        break;
        if (rix != ra->ra_rix) {
                /* update public rate */
                ieee80211_node_set_txrate_dot11rate(ni,
                    ni->ni_rates.rs_rates[rix] & IEEE80211_RATE_VAL);
                ra->ra_rix = rix;

                IEEE80211_NOTE(ni->ni_vap, IEEE80211_MSG_RATECTL, ni,
                    "RSSADAPT new rate %d Mbit/s (pktlen %d rssi %d)",
                    ieee80211_node_get_txrate_kbit(ni) / 1000, pktlen, rssi);
        }
        return rix;
}

/*
 * Adapt the data rate to suit the conditions.  When a transmitted
 * packet is dropped after RAL_RSSADAPT_RETRY_LIMIT retransmissions,
 * raise the RSS threshold for transmitting packets of similar length at
 * the same data rate.
 */
static void
rssadapt_lower_rate(struct ieee80211_rssadapt_node *ra, int pktlen, int rssi)
{
        uint16_t last_thr;
        uint16_t (*thrs)[IEEE80211_RATE_SIZE];
        u_int rix;

        thrs = &ra->ra_rate_thresh[bucket(pktlen)];

        rix = ra->ra_rix;
        last_thr = (*thrs)[rix];
        (*thrs)[rix] = interpolate(master_expavgctl.rc_thresh,
            last_thr, (rssi << 8));

        IEEE80211_DPRINTF(ra->ra_rs->vap, IEEE80211_MSG_RATECTL,
            "RSSADAPT lower threshold for rate %d (last_thr %d new thr %d rssi %d)\n",
            ra->ra_rates.rs_rates[rix + 1] & IEEE80211_RATE_VAL,
            last_thr, (*thrs)[rix], rssi);
}

static void
rssadapt_raise_rate(struct ieee80211_rssadapt_node *ra, int pktlen, int rssi)
{
        uint16_t (*thrs)[IEEE80211_RATE_SIZE];
        uint16_t newthr, oldthr;
        int rix;

        thrs = &ra->ra_rate_thresh[bucket(pktlen)];

        rix = ra->ra_rix;
        if ((*thrs)[rix + 1] > (*thrs)[rix]) {
                oldthr = (*thrs)[rix + 1];
                if ((*thrs)[rix] == 0)
                        newthr = (rssi << 8);
                else
                        newthr = (*thrs)[rix];
                (*thrs)[rix + 1] = interpolate(master_expavgctl.rc_decay,
                    oldthr, newthr);

                IEEE80211_DPRINTF(ra->ra_rs->vap, IEEE80211_MSG_RATECTL,
                    "RSSADAPT raise threshold for rate %d (oldthr %d newthr %d rssi %d)\n",
                    ra->ra_rates.rs_rates[rix + 1] & IEEE80211_RATE_VAL,
                    oldthr, newthr, rssi);

                ra->ra_last_raise = ticks;
        }
}

static void
rssadapt_tx_complete(const struct ieee80211_node *ni,
    const struct ieee80211_ratectl_tx_status *status)
{
        struct ieee80211_rssadapt_node *ra = ni->ni_rctls;
        int pktlen, rssi;

        if (!ra)
                return;

        if ((status->flags &
            (IEEE80211_RATECTL_STATUS_PKTLEN|IEEE80211_RATECTL_STATUS_RSSI)) !=
            (IEEE80211_RATECTL_STATUS_PKTLEN|IEEE80211_RATECTL_STATUS_RSSI))
                return;

        pktlen = status->pktlen;
        rssi = status->rssi;

        if (status->status == IEEE80211_RATECTL_TX_SUCCESS) {
                ra->ra_nok++;
                if ((ra->ra_rix + 1) < ra->ra_rates.rs_nrates &&
                    (ticks - ra->ra_last_raise) >= ra->ra_raise_interval)
                        rssadapt_raise_rate(ra, pktlen, rssi);
        } else {
                ra->ra_nfail++;
                rssadapt_lower_rate(ra, pktlen, rssi);
        }
}

static int
rssadapt_sysctl_interval(SYSCTL_HANDLER_ARGS)
{
        struct ieee80211vap *vap = arg1;
        struct ieee80211_rssadapt *rs = vap->iv_rs;
        int msecs, error;

        if (!rs)
                return ENOMEM;

        msecs = ticks_to_msecs(rs->interval);
        error = sysctl_handle_int(oidp, &msecs, 0, req);
        if (error || !req->newptr)
                return error;
        rssadapt_setinterval(vap, msecs);
        return 0;
}

static void
rssadapt_sysctlattach(struct ieee80211vap *vap,
    struct sysctl_ctx_list *ctx, struct sysctl_oid *tree)
{

        SYSCTL_ADD_PROC(ctx, SYSCTL_CHILDREN(tree), OID_AUTO,
            "rssadapt_rate_interval",
            CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, vap, 0,
            rssadapt_sysctl_interval, "I", "rssadapt operation interval (ms)");
}