/*      $NetBSD: athrate-sample.c,v 1.21 2021/08/09 21:20:50 andvar Exp $ */

/*-
 * Copyright (c) 2005 John Bicket
 * 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,
 *    without modification.
 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
 *    similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
 *    redistribution must be conditioned upon including a substantially
 *    similar Disclaimer requirement for further binary redistribution.
 * 3. Neither the names of the above-listed copyright holders nor the names
 *    of any contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * NO WARRANTY
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR 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 DAMAGES.
 */

#include <sys/cdefs.h>
#ifdef __FreeBSD__
__FBSDID("$FreeBSD: src/sys/dev/ath/ath_rate/sample/sample.c,v 1.9 2005/07/22 16:50:17 sam Exp $");
#endif
#ifdef __NetBSD__
__KERNEL_RCSID(0, "$NetBSD: athrate-sample.c,v 1.21 2021/08/09 21:20:50 andvar Exp $");
#endif


/*
 * John Bicket's SampleRate control algorithm.
 */
#ifdef _KERNEL_OPT
#include "opt_inet.h"
#endif

#include <sys/param.h>
#include <sys/systm.h> 
#include <sys/sysctl.h>
#include <sys/kernel.h>
#include <sys/errno.h>
#include <sys/device.h>

#include <sys/bus.h>

#include <sys/socket.h>
 
#include <net/if.h>
#include <net/if_media.h>
#include <net/if_arp.h>
#include <net/if_ether.h>               /* XXX for ether_sprintf */

#include <net80211/ieee80211_var.h>

#include <net/bpf.h>

#ifdef INET
#include <netinet/in.h> 
#endif

#include "ah_desc.h"
#include <dev/ic/athvar.h>
#include <dev/ic/athrate-sample.h>

#define SAMPLE_DEBUG
#ifdef SAMPLE_DEBUG
enum {
        ATH_DEBUG_RATE          = 0x00000010    /* rate control */
};
#define DPRINTF(sc, _fmt, ...) do {                             \
        if (sc->sc_debug & ATH_DEBUG_RATE)                      \
                printf(_fmt, __VA_ARGS__);                      \
} while (0)
#else
#define DPRINTF(sc, _fmt, ...)
#endif

/*
 * This file is an implementation of the SampleRate algorithm
 * in "Bit-rate Selection in Wireless Networks"
 * (http://www.pdos.lcs.mit.edu/papers/jbicket-ms.ps)
 *
 * SampleRate chooses the bit-rate it predicts will provide the most
 * throughput based on estimates of the expected per-packet
 * transmission time for each bit-rate.  SampleRate periodically sends
 * packets at bit-rates other than the current one to estimate when
 * another bit-rate will provide better performance. SampleRate
 * switches to another bit-rate when its estimated per-packet
 * transmission time becomes smaller than the current bit-rate's.
 * SampleRate reduces the number of bit-rates it must sample by
 * eliminating those that could not perform better than the one
 * currently being used.  SampleRate also stops probing at a bit-rate
 * if it experiences several successive losses.
 *
 * The difference between the algorithm in the thesis and the one in this
 * file is that the one in this file uses a ewma instead of a window.
 *
 * Also, this implementation tracks the average transmission time for
 * a few different packet sizes independently for each link.
 */

#define STALE_FAILURE_TIMEOUT_MS 10000
#define MIN_SWITCH_MS 1000

static void     ath_rate_ctl_reset(struct ath_softc *, struct ieee80211_node *);

static inline int
size_to_bin(int size) 
{
        int x = 0;
        for (x = 0; x < NUM_PACKET_SIZE_BINS; x++) {
                if (size <= packet_size_bins[x]) {
                        return x;
                }
        }
        return NUM_PACKET_SIZE_BINS-1;
}
static inline int bin_to_size(int index) {
        return packet_size_bins[index];
}

static inline int
rate_to_ndx(struct sample_node *sn, int rate) {
        int x = 0;
        for (x = 0; x < sn->num_rates; x++) {
                if (sn->rates[x].rate == rate) {
                        return x;
                }      
        }
        return -1;
}

void
ath_rate_node_init(struct ath_softc *sc, struct ath_node *an)
{
        DPRINTF(sc, "%s:\n", __func__);
        /* NB: assumed to be zero'd by caller */
}

void
ath_rate_node_cleanup(struct ath_softc *sc, struct ath_node *an)
{
        DPRINTF(sc, "%s:\n", __func__);
}


/*
 * returns the ndx with the lowest average_tx_time,
 * or -1 if all the average_tx_times are 0.
 */
static inline int best_rate_ndx(struct sample_node *sn, int size_bin, 
                                  int require_acked_before)
{
        int x = 0;
        int best_ndx = 0;
        int best_rate_tt = 0;
        for (x = 0; x < sn->num_rates; x++) {
                int tt = sn->stats[size_bin][x].average_tx_time;
                if (tt <= 0 || (require_acked_before && 
                                !sn->stats[size_bin][x].packets_acked)) {
                        continue;
                }

                /* 9 megabits never works better than 12 */
                if (sn->rates[x].rate == 18) 
                        continue;

                /* don't use a bit-rate that has been failing */
                if (sn->stats[size_bin][x].successive_failures > 3)
                        continue;

                if (!best_rate_tt || best_rate_tt > tt) {
                        best_rate_tt = tt;
                        best_ndx = x;
                }
        }
        return (best_rate_tt) ? best_ndx : -1;
}

/*
 * pick a good "random" bit-rate to sample other than the current one
 */
static inline int
pick_sample_ndx(struct sample_node *sn, int size_bin) 
{
        int x = 0;
        int current_ndx = 0;
        unsigned current_tt = 0;
        
        current_ndx = sn->current_rate[size_bin];
        if (current_ndx < 0) {
                /* no successes yet, send at the lowest bit-rate */
                return 0;
        }
        
        current_tt = sn->stats[size_bin][current_ndx].average_tx_time;
        
        for (x = 0; x < sn->num_rates; x++) {
                int ndx = (sn->last_sample_ndx[size_bin]+1+x) % sn->num_rates;

                /* don't sample the current bit-rate */
                if (ndx == current_ndx) 
                        continue;

                /* this bit-rate is always worse than the current one */
                if (sn->stats[size_bin][ndx].perfect_tx_time > current_tt) 
                        continue;

                /* rarely sample bit-rates that fail a lot */
                if (ticks - sn->stats[size_bin][ndx].last_tx < ((hz * STALE_FAILURE_TIMEOUT_MS)/1000) &&
                    sn->stats[size_bin][ndx].successive_failures > 3)
                        continue;

                /* don't sample more than 2 indexes higher 
                 * for rates higher than 11 megabits
                 */
                if (sn->rates[ndx].rate > 22 && ndx > current_ndx + 2)
                        continue;

                /* 9 megabits never works better than 12 */
                if (sn->rates[ndx].rate == 18) 
                        continue;

                /* if we're using 11 megabits, only sample up to 12 megabits
                 */
                if (sn->rates[current_ndx].rate == 22 && ndx > current_ndx + 1) 
                        continue;

                sn->last_sample_ndx[size_bin] = ndx;
                return ndx;
        }
        return current_ndx;
}

void
ath_rate_findrate(struct ath_softc *sc, struct ath_node *an,
                  int shortPreamble, size_t frameLen,
                  u_int8_t *rix, int *try0, u_int8_t *txrate)
{
        struct sample_node *sn = ATH_NODE_SAMPLE(an);
        struct sample_softc *ssc = ATH_SOFTC_SAMPLE(sc);
        struct ieee80211com *ic = &sc->sc_ic;
        int ndx, size_bin, mrr, best_ndx, change_rates;
        unsigned average_tx_time;

        mrr = sc->sc_mrretry && !(ic->ic_flags & IEEE80211_F_USEPROT);
        size_bin = size_to_bin(frameLen);
        best_ndx = best_rate_ndx(sn, size_bin, !mrr);

        if (best_ndx >= 0) {
                average_tx_time = sn->stats[size_bin][best_ndx].average_tx_time;
        } else {
                average_tx_time = 0;
        }
        
        if (sn->static_rate_ndx != -1) {
                ndx = sn->static_rate_ndx;
                *try0 = ATH_TXMAXTRY;
        } else {
                *try0 = mrr ? 2 : ATH_TXMAXTRY;
                
                if (sn->sample_tt[size_bin] < average_tx_time * (sn->packets_since_sample[size_bin]*ssc->ath_sample_rate/100)) {
                        /*
                         * we want to limit the time measuring the performance
                         * of other bit-rates to ath_sample_rate% of the
                         * total transmission time.
                         */
                        ndx = pick_sample_ndx(sn, size_bin);
                        if (ndx != sn->current_rate[size_bin]) {
                                sn->current_sample_ndx[size_bin] = ndx;
                        } else {
                                sn->current_sample_ndx[size_bin] = -1;
                        }
                        sn->packets_since_sample[size_bin] = 0;

                } else {
                        change_rates = 0;
                        if (!sn->packets_sent[size_bin] || best_ndx == -1) {
                                /* no packet has been sent successfully yet */
                                for (ndx = sn->num_rates-1; ndx > 0; ndx--) {
                                        /* 
                                         * pick the highest rate <= 36 Mbps
                                         * that hasn't failed.
                                         */
                                        if (sn->rates[ndx].rate <= 72 && 
                                            sn->stats[size_bin][ndx].successive_failures == 0) {
                                                break;
                                        }
                                }
                                change_rates = 1;
                                best_ndx = ndx;
                        } else if (sn->packets_sent[size_bin] < 20) {
                                /* let the bit-rate switch quickly during the first few packets */
                                change_rates = 1;
                        } else if (ticks - ((hz*MIN_SWITCH_MS)/1000) > sn->ticks_since_switch[size_bin]) {
                                /* 2 seconds have gone by */
                                change_rates = 1;
                        } else if (average_tx_time * 2 < sn->stats[size_bin][sn->current_rate[size_bin]].average_tx_time) {
                                /* the current bit-rate is twice as slow as the best one */
                                change_rates = 1;
                        }

                        sn->packets_since_sample[size_bin]++;
                        
                        if (change_rates) {
                                if (best_ndx != sn->current_rate[size_bin]) {
                                        DPRINTF(sc, "%s: %s size %d switch rate %d (%d/%d) -> %d (%d/%d) after %d packets mrr %d\n",
                                                __func__,
                                                ether_sprintf(an->an_node.ni_macaddr),
                                                packet_size_bins[size_bin],
                                                sn->rates[sn->current_rate[size_bin]].rate,
                                                sn->stats[size_bin][sn->current_rate[size_bin]].average_tx_time,
                                                sn->stats[size_bin][sn->current_rate[size_bin]].perfect_tx_time,
                                                sn->rates[best_ndx].rate,
                                                sn->stats[size_bin][best_ndx].average_tx_time,
                                                sn->stats[size_bin][best_ndx].perfect_tx_time,
                                                sn->packets_since_switch[size_bin],
                                                mrr);
                                }
                                sn->packets_since_switch[size_bin] = 0;
                                sn->current_rate[size_bin] = best_ndx;
                                sn->ticks_since_switch[size_bin] = ticks;
                        }
                        ndx = sn->current_rate[size_bin];
                        sn->packets_since_switch[size_bin]++;
                        if (size_bin == 0) {
                                /* 
                                 * set the visible txrate for this node
                                 * to the rate of small packets
                                 */
                                an->an_node.ni_txrate = ndx;
                        }
                }
        }

        KASSERTMSG(ndx >= 0 && ndx < sn->num_rates, "ndx is %d", ndx);

        *rix = sn->rates[ndx].rix;
        if (shortPreamble) {
                *txrate = sn->rates[ndx].shortPreambleRateCode;
        } else {
                *txrate = sn->rates[ndx].rateCode;
        }
        sn->packets_sent[size_bin]++;
}

void
ath_rate_setupxtxdesc(struct ath_softc *sc, struct ath_node *an,
    struct ath_desc *ds, int shortPreamble, u_int8_t rix)
{
        struct sample_node *sn = ATH_NODE_SAMPLE(an);
        int rateCode = -1;
        int frame_size = 0;
        int size_bin = 0;
        int ndx = 0;

        size_bin = size_to_bin(frame_size);     // TODO: it's correct that frame_size always 0 ?
        ndx = sn->current_rate[size_bin]; /* retry at the current bit-rate */
        
        if (!sn->stats[size_bin][ndx].packets_acked) {
                ndx = 0;  /* use the lowest bit-rate */
        }

        if (shortPreamble) {
                rateCode = sn->rates[ndx].shortPreambleRateCode;
        } else {
                rateCode = sn->rates[ndx].rateCode;
        }
        ath_hal_setupxtxdesc(sc->sc_ah, ds
                             , rateCode, 3              /* series 1 */
                             , sn->rates[0].rateCode, 3 /* series 2 */
                             , 0, 0                     /* series 3 */
                             );
}

static void
update_stats(struct ath_softc *sc, struct ath_node *an, 
                  int frame_size,
                  int ndx0, int tries0,
                  int ndx1, int tries1,
                  int ndx2, int tries2,
                  int ndx3, int tries3,
                  int short_tries, int tries, int status)
{
        struct sample_node *sn = ATH_NODE_SAMPLE(an);
        struct sample_softc *ssc = ATH_SOFTC_SAMPLE(sc);
        int tt = 0;
        int tries_so_far = 0;
        int size_bin;
        int size;
        int rate;

        if (ndx0 == -1)
                return;

        size_bin = size_to_bin(frame_size);
        size = bin_to_size(size_bin);
        rate = sn->rates[ndx0].rate;

        tt += calc_usecs_unicast_packet(sc, size, sn->rates[ndx0].rix,
            short_tries - 1, MIN(tries0, tries) - 1);
        tries_so_far += tries0;
        if (tries1 && tries0 < tries) {
                tt += calc_usecs_unicast_packet(sc, size,
                    ndx1 == -1 ? 0 : sn->rates[ndx1].rix, short_tries - 1, 
                    MIN(tries1 + tries_so_far, tries) - tries_so_far - 1);
        }
        tries_so_far += tries1;

        if (tries2 && tries0 + tries1 < tries) {
                tt += calc_usecs_unicast_packet(sc, size,
                    ndx2 == -1 ? 0 : sn->rates[ndx2].rix, short_tries - 1, 
                    MIN(tries2 + tries_so_far, tries) - tries_so_far - 1);
        }

        tries_so_far += tries2;

        if (tries3 && tries0 + tries1 + tries2 < tries) {
                tt += calc_usecs_unicast_packet(sc, size,
                    ndx3 == -1 ? 0 : sn->rates[ndx3].rix, short_tries - 1, 
                    MIN(tries3 + tries_so_far, tries) - tries_so_far - 1);
        }

        if (sn->stats[size_bin][ndx0].total_packets < (100 / (100 - ssc->ath_smoothing_rate))) {
                /* just average the first few packets */
                int avg_tx = sn->stats[size_bin][ndx0].average_tx_time;
                int packets = sn->stats[size_bin][ndx0].total_packets;
                sn->stats[size_bin][ndx0].average_tx_time = (tt+(avg_tx*packets))/(packets+1);
        } else {
                /* use a ewma */
                sn->stats[size_bin][ndx0].average_tx_time = 
                        ((sn->stats[size_bin][ndx0].average_tx_time * ssc->ath_smoothing_rate) + 
                         (tt * (100 - ssc->ath_smoothing_rate))) / 100;
        }
        
        if (status) {
                int y;
                sn->stats[size_bin][ndx0].successive_failures++;
                for (y = size_bin+1; y < NUM_PACKET_SIZE_BINS; y++) {
                        /* also say larger packets failed since we
                         * assume if a small packet fails at a lower
                         * bit-rate then a larger one will also.
                         */
                        sn->stats[y][ndx0].successive_failures++;
                        sn->stats[y][ndx0].last_tx = ticks;
                        sn->stats[y][ndx0].tries += tries;
                        sn->stats[y][ndx0].total_packets++;
                }
        } else {
                sn->stats[size_bin][ndx0].packets_acked++;
                sn->stats[size_bin][ndx0].successive_failures = 0;
        }
        sn->stats[size_bin][ndx0].tries += tries;
        sn->stats[size_bin][ndx0].last_tx = ticks;
        sn->stats[size_bin][ndx0].total_packets++;


        if (ndx0 == sn->current_sample_ndx[size_bin]) {
                DPRINTF(sc, "%s: %s size %d sample rate %d tries (%d/%d) tt %d avg_tt (%d/%d) status %d\n", 
                        __func__, ether_sprintf(an->an_node.ni_macaddr), 
                        size, rate, short_tries, tries, tt, 
                        sn->stats[size_bin][ndx0].average_tx_time,
                        sn->stats[size_bin][ndx0].perfect_tx_time,
                        status);
                sn->sample_tt[size_bin] = tt;
                sn->current_sample_ndx[size_bin] = -1;
        }
}

void
ath_rate_tx_complete(struct ath_softc *sc, struct ath_node *an,
        const struct ath_desc *ds, const struct ath_desc *ds0)
{
        struct ieee80211com *ic = &sc->sc_ic;
        struct sample_node *sn = ATH_NODE_SAMPLE(an);
        const struct ar5212_desc *ads = (const struct ar5212_desc *)&ds->ds_ctl0;
        int final_rate, short_tries, long_tries, frame_size;
        int ndx = -1;
        int mrr;

        final_rate = sc->sc_hwmap[ds->ds_txstat.ts_rate &~ HAL_TXSTAT_ALTRATE].ieeerate;
        short_tries = ds->ds_txstat.ts_shortretry + 1;
        long_tries = ds->ds_txstat.ts_longretry + 1;
        frame_size = ds0->ds_ctl0 & 0x0fff; /* low-order 12 bits of ds_ctl0 */
        if (frame_size == 0)                /* NB: should not happen */
                frame_size = 1500;

        if (sn->num_rates <= 0) {
                DPRINTF(sc, "%s: %s size %d status %d rate/try %d/%d "
                        "no rates yet\n", 
                        __func__, ether_sprintf(an->an_node.ni_macaddr),
                        bin_to_size(size_to_bin(frame_size)),
                        ds->ds_txstat.ts_status,
                        short_tries, long_tries);
                return;
        }

        mrr = sc->sc_mrretry && !(ic->ic_flags & IEEE80211_F_USEPROT);

        if (sc->sc_mrretry && ds->ds_txstat.ts_status) {
                /* this packet failed */
                DPRINTF(sc, "%s: %s size %d rate/try %d/%d %d/%d %d/%d %d/%d status %s retries (%d/%d)\n", 
                        __func__,
                        ether_sprintf(an->an_node.ni_macaddr),
                        bin_to_size(size_to_bin(frame_size)),
                        sc->sc_hwmap[ads->xmit_rate0].ieeerate,
                                ads->xmit_tries0,
                        sc->sc_hwmap[ads->xmit_rate1].ieeerate,
                                ads->xmit_tries1,
                        sc->sc_hwmap[ads->xmit_rate2].ieeerate,
                                ads->xmit_tries2,
                        sc->sc_hwmap[ads->xmit_rate3].ieeerate,
                                ads->xmit_tries3,
                        ds->ds_txstat.ts_status ? "FAIL" : "OK",
                        short_tries, 
                        long_tries);
        }

        if (!mrr || !(ds->ds_txstat.ts_rate & HAL_TXSTAT_ALTRATE)) {
                /* only one rate was used */
                ndx = rate_to_ndx(sn, final_rate);
                DPRINTF(sc, "%s: %s size %d status %d rate/try %d/%d/%d\n", 
                        __func__, ether_sprintf(an->an_node.ni_macaddr),
                        bin_to_size(size_to_bin(frame_size)),
                        ds->ds_txstat.ts_status,
                        ndx, short_tries, long_tries);
                if (ndx >= 0 && ndx < sn->num_rates) {
                        update_stats(sc, an, frame_size, 
                                     ndx, long_tries,
                                     0, 0,
                                     0, 0,
                                     0, 0,
                                     short_tries, long_tries, ds->ds_txstat.ts_status);
                }
        } else {
                int rate0, tries0, ndx0;
                int rate1, tries1, ndx1;
                int rate2, tries2, ndx2;
                int rate3, tries3, ndx3;
                int finalTSIdx = ads->final_ts_index;

                /*
                 * Process intermediate rates that failed.
                 */

                rate0 = sc->sc_hwmap[ads->xmit_rate0].ieeerate;
                tries0 = ads->xmit_tries0;
                ndx0 = rate_to_ndx(sn, rate0);
                
                rate1 = sc->sc_hwmap[ads->xmit_rate1].ieeerate;
                tries1 = ads->xmit_tries1;
                ndx1 = rate_to_ndx(sn, rate1);
                
                rate2 = sc->sc_hwmap[ads->xmit_rate2].ieeerate;
                tries2 = ads->xmit_tries2;
                ndx2 = rate_to_ndx(sn, rate2);
                
                rate3 = sc->sc_hwmap[ads->xmit_rate3].ieeerate;
                tries3 = ads->xmit_tries3;
                ndx3 = rate_to_ndx(sn, rate3);
                
#if 1
                DPRINTF(sc, "%s: %s size %d finaltsidx %d tries %d status %d rate/try %d/%d %d/%d %d/%d %d/%d\n", 
                        __func__, ether_sprintf(an->an_node.ni_macaddr),
                        bin_to_size(size_to_bin(frame_size)),
                        finalTSIdx,
                        long_tries, 
                        ds->ds_txstat.ts_status,
                        rate0, tries0,
                        rate1, tries1,
                        rate2, tries2,
                        rate3, tries3);
#endif

                if (tries0) {
                        update_stats(sc, an, frame_size, 
                                     ndx0, tries0, 
                                     ndx1, tries1, 
                                     ndx2, tries2, 
                                     ndx3, tries3, 
                                     short_tries, ds->ds_txstat.ts_longretry + 1, 
                                     long_tries > tries0);
                }
                
                if (tries1 && finalTSIdx > 0) {
                        update_stats(sc, an, frame_size, 
                                     ndx1, tries1, 
                                     ndx2, tries2, 
                                     ndx3, tries3, 
                                     0, 0, 
                                     short_tries, ds->ds_txstat.ts_longretry + 1 - tries0, 
                                     ds->ds_txstat.ts_status);
                }

                if (tries2 && finalTSIdx > 1) {
                        update_stats(sc, an, frame_size, 
                                     ndx2, tries2, 
                                     ndx3, tries3, 
                                     0, 0,
                                     0, 0,
                                     short_tries, ds->ds_txstat.ts_longretry + 1 - tries0 - tries1, 
                                     ds->ds_txstat.ts_status);
                }

                if (tries3 && finalTSIdx > 2) {
                        update_stats(sc, an, frame_size, 
                                     ndx3, tries3, 
                                     0, 0,
                                     0, 0,
                                     0, 0,
                                     short_tries, ds->ds_txstat.ts_longretry + 1 - tries0 - tries1 - tries2, 
                                     ds->ds_txstat.ts_status);
                }
        }
}

void
ath_rate_newassoc(struct ath_softc *sc, struct ath_node *an, int isnew)
{
        DPRINTF(sc, "%s: %s isnew %d\n", __func__,
                ether_sprintf(an->an_node.ni_macaddr), isnew);
        if (isnew)
                ath_rate_ctl_reset(sc, &an->an_node);
}

/*
 * Initialize the tables for a node.
 */
static void
ath_rate_ctl_reset(struct ath_softc *sc, struct ieee80211_node *ni)
{
#define RATE(_ix)       (ni->ni_rates.rs_rates[(_ix)] & IEEE80211_RATE_VAL)
        struct ieee80211com *ic = &sc->sc_ic;
        struct ath_node *an = ATH_NODE(ni);
        struct sample_node *sn = ATH_NODE_SAMPLE(an);
        const HAL_RATE_TABLE *rt = sc->sc_currates;
        int x, y, srate;

        KASSERTMSG(rt != NULL, "no rate table, mode %u", sc->sc_curmode);
        sn->static_rate_ndx = -1;
        if (ic->ic_fixed_rate != IEEE80211_FIXED_RATE_NONE) {
                /*
                 * A fixed rate is to be used; ic_fixed_rate is an
                 * index into the supported rate set.  Convert this
                 * to the index into the negotiated rate set for
                 * the node.  We know the rate is there because the
                 * rate set is checked when the station associates.
                 */
                const struct ieee80211_rateset *rs =
                        &ic->ic_sup_rates[ic->ic_curmode];
                int r = rs->rs_rates[ic->ic_fixed_rate] & IEEE80211_RATE_VAL;
                /* NB: the rate set is assumed sorted */
                srate = ni->ni_rates.rs_nrates - 1;
                for (; srate >= 0 && RATE(srate) != r; srate--)
                        ;
                KASSERTMSG(srate >= 0,
                        "fixed rate %d not in rate set", ic->ic_fixed_rate);
                sn->static_rate_ndx = srate;
        }

        DPRINTF(sc, "%s: %s size 1600 rate/tt", __func__, ether_sprintf(ni->ni_macaddr));

        sn->num_rates = ni->ni_rates.rs_nrates;
        for (x = 0; x < ni->ni_rates.rs_nrates; x++) {
                sn->rates[x].rate = ni->ni_rates.rs_rates[x] & IEEE80211_RATE_VAL;
                sn->rates[x].rix = sc->sc_rixmap[sn->rates[x].rate];
                sn->rates[x].rateCode = rt->info[sn->rates[x].rix].rateCode;
                sn->rates[x].shortPreambleRateCode = 
                        rt->info[sn->rates[x].rix].rateCode | 
                        rt->info[sn->rates[x].rix].shortPreamble;

                DPRINTF(sc, " %d/%d", sn->rates[x].rate,
                        calc_usecs_unicast_packet(sc, 1600, sn->rates[x].rix, 
                                                  0,0));
        }
        DPRINTF(sc, "%s\n", "");
        
        /* set the visible bit-rate to the lowest one available */
        ni->ni_txrate = 0;
        sn->num_rates = ni->ni_rates.rs_nrates;
        
        for (y = 0; y < NUM_PACKET_SIZE_BINS; y++) {
                int size = bin_to_size(y);
                int ndx = 0;
                sn->packets_sent[y] = 0;
                sn->current_sample_ndx[y] = -1;
                sn->last_sample_ndx[y] = 0;
                
                for (x = 0; x < ni->ni_rates.rs_nrates; x++) {
                        sn->stats[y][x].successive_failures = 0;
                        sn->stats[y][x].tries = 0;
                        sn->stats[y][x].total_packets = 0;
                        sn->stats[y][x].packets_acked = 0;
                        sn->stats[y][x].last_tx = 0;
                        
                        sn->stats[y][x].perfect_tx_time = 
                                calc_usecs_unicast_packet(sc, size, 
                                                          sn->rates[x].rix,
                                                          0, 0);
                        sn->stats[y][x].average_tx_time = sn->stats[y][x].perfect_tx_time;
                }

                /* set the initial rate */
                for (ndx = sn->num_rates-1; ndx > 0; ndx--) {
                        if (sn->rates[ndx].rate <= 72) {
                                break;
                        }
                }
                sn->current_rate[y] = ndx;
        }

        DPRINTF(sc, "%s: %s %d rates %d%sMbps (%dus)- %d%sMbps (%dus)\n",
                __func__, ether_sprintf(ni->ni_macaddr), 
                sn->num_rates,
                sn->rates[0].rate/2, sn->rates[0].rate % 0x1 ? ".5" : "",
                sn->stats[1][0].perfect_tx_time,
                sn->rates[sn->num_rates-1].rate/2,
                        sn->rates[sn->num_rates-1].rate % 0x1 ? ".5" : "",
                sn->stats[1][sn->num_rates-1].perfect_tx_time
        );

        ni->ni_txrate = sn->current_rate[0];
#undef RATE
}

static void
rate_cb(void *arg, struct ieee80211_node *ni)
{
        struct ath_softc *sc = arg;

        ath_rate_newassoc(sc, ATH_NODE(ni), 1);
}

/*
 * Reset the rate control state for each 802.11 state transition.
 */
void
ath_rate_newstate(struct ath_softc *sc, enum ieee80211_state state)
{
        struct ieee80211com *ic = &sc->sc_ic;

        if (state == IEEE80211_S_RUN) {
                if (ic->ic_opmode != IEEE80211_M_STA) {
                        /*
                         * Sync rates for associated stations and neighbors.
                         */
                        ieee80211_iterate_nodes(&ic->ic_sta, rate_cb, sc);
                }
                ath_rate_newassoc(sc, ATH_NODE(ic->ic_bss), 1);
        }
}

static void
ath_rate_sysctlattach(struct ath_softc *sc, struct sample_softc *osc)
{
        int rc;
        struct sysctllog **log = &sc->sc_sysctllog;
        const struct sysctlnode *cnode, *rnode;

        if ((rnode = ath_sysctl_instance(device_xname(sc->sc_dev), log)) == NULL)
                return;

        /* XXX bounds check [0..100] */
        if ((rc = SYSCTL_PFX_INT(osc->ath_, CTLFLAG_READWRITE, smoothing_rate,
            "rate control: retry threshold to credit rate raise (%%)")) != 0)
                goto err;

        /* XXX bounds check [2..100] */
        if ((rc = SYSCTL_PFX_INT(osc->ath_, CTLFLAG_READWRITE, sample_rate,
            "rate control: # good periods before raising rate")) != 0)
                goto err;

        return;
err:
        printf("%s: sysctl_createv failed, rc = %d\n", __func__, rc);
}

struct ath_ratectrl *
ath_rate_attach(struct ath_softc *sc)
{
        struct sample_softc *osc;
        
        DPRINTF(sc, "%s:\n", __func__);
        osc = malloc(sizeof(struct sample_softc), M_DEVBUF, M_WAITOK|M_ZERO);
        osc->arc.arc_space = sizeof(struct sample_node);
        osc->ath_smoothing_rate = 95;   /* ewma percentage (out of 100) */
        osc->ath_sample_rate = 10;      /* send a different bit-rate 1/X packets */
        ath_rate_sysctlattach(sc, osc);
        return &osc->arc;
}

void
ath_rate_detach(struct ath_ratectrl *arc)
{
        struct sample_softc *osc = (struct sample_softc *) arc;
        
        free(osc, M_DEVBUF);
}