rate.c

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/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright (c) 2006 Jiri Benc <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <linux/module.h>
#include "rate.h"
#include "ieee80211_i.h"
#include "debugfs.h"

struct rate_control_alg {
    struct list_head list;
    struct rate_control_ops *ops;
};

static LIST_HEAD(rate_ctrl_algs);
static DEFINE_MUTEX(rate_ctrl_mutex);

static char *ieee80211_default_rc_algo = CONFIG_MAC80211_RC_DEFAULT;
module_param(ieee80211_default_rc_algo, charp, 0644);
MODULE_PARM_DESC(ieee80211_default_rc_algo,
         "Default rate control algorithm for mac80211 to use");

int ieee80211_rate_control_register(struct rate_control_ops *ops)
{
    struct rate_control_alg *alg;

    if (!ops->name)
        return -EINVAL;

    mutex_lock(&rate_ctrl_mutex);
    list_for_each_entry(alg, &rate_ctrl_algs, list) {
        if (!strcmp(alg->ops->name, ops->name)) {
            /* don't register an algorithm twice */
            WARN_ON(1);
            mutex_unlock(&rate_ctrl_mutex);
            return -EALREADY;
        }
    }

    alg = kzalloc(sizeof(*alg), GFP_KERNEL);
    if (alg == NULL) {
        mutex_unlock(&rate_ctrl_mutex);
        return -ENOMEM;
    }
    alg->ops = ops;

    list_add_tail(&alg->list, &rate_ctrl_algs);
    mutex_unlock(&rate_ctrl_mutex);

    return 0;
}
EXPORT_SYMBOL(ieee80211_rate_control_register);

void ieee80211_rate_control_unregister(struct rate_control_ops *ops)
{
    struct rate_control_alg *alg;

    mutex_lock(&rate_ctrl_mutex);
    list_for_each_entry(alg, &rate_ctrl_algs, list) {
        if (alg->ops == ops) {
            list_del(&alg->list);
            kfree(alg);
            break;
        }
    }
    mutex_unlock(&rate_ctrl_mutex);
}
EXPORT_SYMBOL(ieee80211_rate_control_unregister);

static struct rate_control_ops *
ieee80211_try_rate_control_ops_get(const char *name)
{
    struct rate_control_alg *alg;
    struct rate_control_ops *ops = NULL;

    if (!name)
        return NULL;

    mutex_lock(&rate_ctrl_mutex);
    list_for_each_entry(alg, &rate_ctrl_algs, list) {
        if (!strcmp(alg->ops->name, name))
            if (try_module_get(alg->ops->module)) {
                ops = alg->ops;
                break;
            }
    }
    mutex_unlock(&rate_ctrl_mutex);
    return ops;
}

/* Get the rate control algorithm. */
static struct rate_control_ops *
ieee80211_rate_control_ops_get(const char *name)
{
    struct rate_control_ops *ops;
    const char *alg_name;

    kparam_block_sysfs_write(ieee80211_default_rc_algo);
    if (!name)
        alg_name = ieee80211_default_rc_algo;
    else
        alg_name = name;

    ops = ieee80211_try_rate_control_ops_get(alg_name);
    if (!ops) {
        request_module("rc80211_%s", alg_name);
        ops = ieee80211_try_rate_control_ops_get(alg_name);
    }
    if (!ops && name)
        /* try default if specific alg requested but not found */
        ops = ieee80211_try_rate_control_ops_get(ieee80211_default_rc_algo);

    /* try built-in one if specific alg requested but not found */
    if (!ops && strlen(CONFIG_MAC80211_RC_DEFAULT))
        ops = ieee80211_try_rate_control_ops_get(CONFIG_MAC80211_RC_DEFAULT);
    kparam_unblock_sysfs_write(ieee80211_default_rc_algo);

    return ops;
}

static void ieee80211_rate_control_ops_put(struct rate_control_ops *ops)
{
    module_put(ops->module);
}

#ifdef CONFIG_MAC80211_DEBUGFS
static ssize_t rcname_read(struct file *file, char __user *userbuf,
               size_t count, loff_t *ppos)
{
    struct rate_control_ref *ref = file->private_data;
    int len = strlen(ref->ops->name);

    return simple_read_from_buffer(userbuf, count, ppos,
                       ref->ops->name, len);
}

static const struct file_operations rcname_ops = {
    .read = rcname_read,
    .open = simple_open,
    .llseek = default_llseek,
};
#endif

static struct rate_control_ref *rate_control_alloc(const char *name,
                        struct ieee80211_local *local)
{
    struct dentry *debugfsdir = NULL;
    struct rate_control_ref *ref;

    ref = kmalloc(sizeof(struct rate_control_ref), GFP_KERNEL);
    if (!ref)
        goto fail_ref;
    ref->local = local;
    ref->ops = ieee80211_rate_control_ops_get(name);
    if (!ref->ops)
        goto fail_ops;

#ifdef CONFIG_MAC80211_DEBUGFS
    debugfsdir = debugfs_create_dir("rc", local->hw.wiphy->debugfsdir);
    local->debugfs.rcdir = debugfsdir;
    debugfs_create_file("name", 0400, debugfsdir, ref, &rcname_ops);
#endif

    ref->priv = ref->ops->alloc(&local->hw, debugfsdir);
    if (!ref->priv)
        goto fail_priv;
    return ref;

fail_priv:
    ieee80211_rate_control_ops_put(ref->ops);
fail_ops:
    kfree(ref);
fail_ref:
    return NULL;
}

static void rate_control_free(struct rate_control_ref *ctrl_ref)
{
    ctrl_ref->ops->free(ctrl_ref->priv);

#ifdef CONFIG_MAC80211_DEBUGFS
    debugfs_remove_recursive(ctrl_ref->local->debugfs.rcdir);
    ctrl_ref->local->debugfs.rcdir = NULL;
#endif

    ieee80211_rate_control_ops_put(ctrl_ref->ops);
    kfree(ctrl_ref);
}

static bool rc_no_data_or_no_ack_use_min(struct ieee80211_tx_rate_control *txrc)
{
    struct sk_buff *skb = txrc->skb;
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    __le16 fc;

    fc = hdr->frame_control;

    return (info->flags & (IEEE80211_TX_CTL_NO_ACK |
                   IEEE80211_TX_CTL_USE_MINRATE)) ||
        !ieee80211_is_data(fc);
}

static void rc_send_low_broadcast(s8 *idx, u32 basic_rates,
                  struct ieee80211_supported_band *sband)
{
    u8 i;

    if (basic_rates == 0)
        return; /* assume basic rates unknown and accept rate */
    if (*idx < 0)
        return;
    if (basic_rates & (1 << *idx))
        return; /* selected rate is a basic rate */

    for (i = *idx + 1; i <= sband->n_bitrates; i++) {
        if (basic_rates & (1 << i)) {
            *idx = i;
            return;
        }
    }

    /* could not find a basic rate; use original selection */
}

static inline s8
rate_lowest_non_cck_index(struct ieee80211_supported_band *sband,
              struct ieee80211_sta *sta)
{
    int i;

    for (i = 0; i < sband->n_bitrates; i++) {
        struct ieee80211_rate *srate = &sband->bitrates[i];
        if ((srate->bitrate == 10) || (srate->bitrate == 20) ||
            (srate->bitrate == 55) || (srate->bitrate == 110))
            continue;

        if (rate_supported(sta, sband->band, i))
            return i;
    }

    /* No matching rate found */
    return 0;
}


bool rate_control_send_low(struct ieee80211_sta *sta,
               void *priv_sta,
               struct ieee80211_tx_rate_control *txrc)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
    struct ieee80211_supported_band *sband = txrc->sband;
    int mcast_rate;

    if (!sta || !priv_sta || rc_no_data_or_no_ack_use_min(txrc)) {
        if ((sband->band != IEEE80211_BAND_2GHZ) ||
            !(info->flags & IEEE80211_TX_CTL_NO_CCK_RATE))
            info->control.rates[0].idx =
                rate_lowest_index(txrc->sband, sta);
        else
            info->control.rates[0].idx =
                rate_lowest_non_cck_index(txrc->sband, sta);
        info->control.rates[0].count =
            (info->flags & IEEE80211_TX_CTL_NO_ACK) ?
            1 : txrc->hw->max_rate_tries;
        if (!sta && txrc->bss) {
            mcast_rate = txrc->bss_conf->mcast_rate[sband->band];
            if (mcast_rate > 0) {
                info->control.rates[0].idx = mcast_rate - 1;
                return true;
            }

            rc_send_low_broadcast(&info->control.rates[0].idx,
                          txrc->bss_conf->basic_rates,
                          sband);
        }
        return true;
    }
    return false;
}
EXPORT_SYMBOL(rate_control_send_low);

static bool rate_idx_match_legacy_mask(struct ieee80211_tx_rate *rate,
                       int n_bitrates, u32 mask)
{
    int j;

    /* See whether the selected rate or anything below it is allowed. */
    for (j = rate->idx; j >= 0; j--) {
        if (mask & (1 << j)) {
            /* Okay, found a suitable rate. Use it. */
            rate->idx = j;
            return true;
        }
    }

    /* Try to find a higher rate that would be allowed */
    for (j = rate->idx + 1; j < n_bitrates; j++) {
        if (mask & (1 << j)) {
            /* Okay, found a suitable rate. Use it. */
            rate->idx = j;
            return true;
        }
    }
    return false;
}

static bool rate_idx_match_mcs_mask(struct ieee80211_tx_rate *rate,
                    u8 mcs_mask[IEEE80211_HT_MCS_MASK_LEN])
{
    int i, j;
    int ridx, rbit;

    ridx = rate->idx / 8;
    rbit = rate->idx % 8;

    /* sanity check */
    if (ridx < 0 || ridx >= IEEE80211_HT_MCS_MASK_LEN)
        return false;

    /* See whether the selected rate or anything below it is allowed. */
    for (i = ridx; i >= 0; i--) {
        for (j = rbit; j >= 0; j--)
            if (mcs_mask[i] & BIT(j)) {
                rate->idx = i * 8 + j;
                return true;
            }
        rbit = 7;
    }

    /* Try to find a higher rate that would be allowed */
    ridx = (rate->idx + 1) / 8;
    rbit = (rate->idx + 1) % 8;

    for (i = ridx; i < IEEE80211_HT_MCS_MASK_LEN; i++) {
        for (j = rbit; j < 8; j++)
            if (mcs_mask[i] & BIT(j)) {
                rate->idx = i * 8 + j;
                return true;
            }
        rbit = 0;
    }
    return false;
}



static void rate_idx_match_mask(struct ieee80211_tx_rate *rate,
                struct ieee80211_tx_rate_control *txrc,
                u32 mask,
                u8 mcs_mask[IEEE80211_HT_MCS_MASK_LEN])
{
    struct ieee80211_tx_rate alt_rate;

    /* handle HT rates */
    if (rate->flags & IEEE80211_TX_RC_MCS) {
        if (rate_idx_match_mcs_mask(rate, mcs_mask))
            return;

        /* also try the legacy rates. */
        alt_rate.idx = 0;
        /* keep protection flags */
        alt_rate.flags = rate->flags &
                 (IEEE80211_TX_RC_USE_RTS_CTS |
                  IEEE80211_TX_RC_USE_CTS_PROTECT |
                  IEEE80211_TX_RC_USE_SHORT_PREAMBLE);
        alt_rate.count = rate->count;
        if (rate_idx_match_legacy_mask(&alt_rate,
                           txrc->sband->n_bitrates,
                           mask)) {
            *rate = alt_rate;
            return;
        }
    } else {
        struct sk_buff *skb = txrc->skb;
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        __le16 fc;

        /* handle legacy rates */
        if (rate_idx_match_legacy_mask(rate, txrc->sband->n_bitrates,
                           mask))
            return;

        /* if HT BSS, and we handle a data frame, also try HT rates */
        if (txrc->bss_conf->channel_type == NL80211_CHAN_NO_HT)
            return;

        fc = hdr->frame_control;
        if (!ieee80211_is_data(fc))
            return;

        alt_rate.idx = 0;
        /* keep protection flags */
        alt_rate.flags = rate->flags &
                 (IEEE80211_TX_RC_USE_RTS_CTS |
                  IEEE80211_TX_RC_USE_CTS_PROTECT |
                  IEEE80211_TX_RC_USE_SHORT_PREAMBLE);
        alt_rate.count = rate->count;

        alt_rate.flags |= IEEE80211_TX_RC_MCS;

        if ((txrc->bss_conf->channel_type == NL80211_CHAN_HT40MINUS) ||
            (txrc->bss_conf->channel_type == NL80211_CHAN_HT40PLUS))
            alt_rate.flags |= IEEE80211_TX_RC_40_MHZ_WIDTH;

        if (rate_idx_match_mcs_mask(&alt_rate, mcs_mask)) {
            *rate = alt_rate;
            return;
        }
    }

    /*
     * Uh.. No suitable rate exists. This should not really happen with
     * sane TX rate mask configurations. However, should someone manage to
     * configure supported rates and TX rate mask in incompatible way,
     * allow the frame to be transmitted with whatever the rate control
     * selected.
     */
}

void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
               struct sta_info *sta,
               struct ieee80211_tx_rate_control *txrc)
{
    struct rate_control_ref *ref = sdata->local->rate_ctrl;
    void *priv_sta = NULL;
    struct ieee80211_sta *ista = NULL;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
    int i;
    u32 mask;
    u8 mcs_mask[IEEE80211_HT_MCS_MASK_LEN];

    if (sta && test_sta_flag(sta, WLAN_STA_RATE_CONTROL)) {
        ista = &sta->sta;
        priv_sta = sta->rate_ctrl_priv;
    }

    for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
        info->control.rates[i].idx = -1;
        info->control.rates[i].flags = 0;
        info->control.rates[i].count = 0;
    }

    if (sdata->local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL)
        return;

    ref->ops->get_rate(ref->priv, ista, priv_sta, txrc);

    /*
     * Try to enforce the rateidx mask the user wanted. skip this if the
     * default mask (allow all rates) is used to save some processing for
     * the common case.
     */
    mask = sdata->rc_rateidx_mask[info->band];
    memcpy(mcs_mask, sdata->rc_rateidx_mcs_mask[info->band],
           sizeof(mcs_mask));
    if (mask != (1 << txrc->sband->n_bitrates) - 1) {
        if (sta) {
            /* Filter out rates that the STA does not support */
            mask &= sta->sta.supp_rates[info->band];
            for (i = 0; i < sizeof(mcs_mask); i++)
                mcs_mask[i] &= sta->sta.ht_cap.mcs.rx_mask[i];
        }
        /*
         * Make sure the rate index selected for each TX rate is
         * included in the configured mask and change the rate indexes
         * if needed.
         */
        for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
            /* Skip invalid rates */
            if (info->control.rates[i].idx < 0)
                break;
            rate_idx_match_mask(&info->control.rates[i], txrc,
                        mask, mcs_mask);
        }
    }

    BUG_ON(info->control.rates[0].idx < 0);
}

int ieee80211_init_rate_ctrl_alg(struct ieee80211_local *local,
                 const char *name)
{
    struct rate_control_ref *ref;

    ASSERT_RTNL();

    if (local->open_count)
        return -EBUSY;

    if (local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL) {
        if (WARN_ON(!local->ops->set_rts_threshold))
            return -EINVAL;
        return 0;
    }

    ref = rate_control_alloc(name, local);
    if (!ref) {
        wiphy_warn(local->hw.wiphy,
               "Failed to select rate control algorithm\n");
        return -ENOENT;
    }

    WARN_ON(local->rate_ctrl);
    local->rate_ctrl = ref;

    wiphy_debug(local->hw.wiphy, "Selected rate control algorithm '%s'\n",
            ref->ops->name);

    return 0;
}

void rate_control_deinitialize(struct ieee80211_local *local)
{
    struct rate_control_ref *ref;

    ref = local->rate_ctrl;

    if (!ref)
        return;

    local->rate_ctrl = NULL;
    rate_control_free(ref);
}