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    Subject[RFC v1] mac80211: minstrel_ht: respect RTS threshold setting
    Date
    Despite the 'RTS thr:off' setting a wireshark trace of IBSS
    traffic with HT40 mode enabled between two ath9k cards revealed
    some RTS/CTS traffic.

    Debug and code analysis showed that most places setting
    IEEE80211_TX_RC_USE_RTS_CTS respect the RTS strategy by
    evaluating rts_threshold, e.g. net/mac80211/tx.c:

    698 /* set up RTS protection if desired */
    699 if (len > tx->local->hw.wiphy->rts_threshold) {
    700 txrc.rts = true;
    701 }
    702
    703 info->control.use_rts = txrc.rts;

    or drivers/net/wireless/ath/ath9k/xmit.c

    1238 /*
    1239 * Handle RTS threshold for unaggregated HT frames.
    1240 */
    1241 if (bf_isampdu(bf) && !bf_isaggr(bf) &&
    1242 (rates[i].flags & IEEE80211_TX_RC_MCS) &&
    1243 unlikely(rts_thresh != (u32) -1)) {
    1244 if (!rts_thresh || (len > rts_thresh))
    1245 rts = true;
    1246 }

    The only place setting IEEE80211_TX_RC_USE_RTS_CTS unconditionally
    was found in net/mac80211/rc80211_minstrel_ht.c.

    Fix this by propagating the calculated use_rts value to the
    minstrel_ht_set_rate() function and evaluate it accordingly
    before setting IEEE80211_TX_RC_USE_RTS_CTS.

    Signed-off-by: Peter Seiderer <ps.report@gmx.net>
    ---
    net/mac80211/rc80211_minstrel_ht.c | 21 ++++++++++++---------
    1 file changed, 12 insertions(+), 9 deletions(-)

    diff --git a/net/mac80211/rc80211_minstrel_ht.c b/net/mac80211/rc80211_minstrel_ht.c
    index 72b44d4c42d0..f52edef443fa 100644
    --- a/net/mac80211/rc80211_minstrel_ht.c
    +++ b/net/mac80211/rc80211_minstrel_ht.c
    @@ -276,7 +276,8 @@ static const u8 minstrel_sample_seq[] = {
    };

    static void
    -minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi);
    +minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
    + bool use_rts);

    /*
    * Some VHT MCSes are invalid (when Ndbps / Nes is not an integer)
    @@ -1254,7 +1255,7 @@ minstrel_ht_tx_status(void *priv, struct ieee80211_supported_band *sband,
    }

    if (update)
    - minstrel_ht_update_rates(mp, mi);
    + minstrel_ht_update_rates(mp, mi, info->control.use_rts);
    }

    static void
    @@ -1319,7 +1320,8 @@ minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,

    static void
    minstrel_ht_set_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
    - struct ieee80211_sta_rates *ratetbl, int offset, int index)
    + struct ieee80211_sta_rates *ratetbl, int offset, int index,
    + bool use_rts)
    {
    int group_idx = MI_RATE_GROUP(index);
    const struct mcs_group *group = &minstrel_mcs_groups[group_idx];
    @@ -1357,7 +1359,7 @@ minstrel_ht_set_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
    * - if station is in dynamic SMPS (and streams > 1)
    * - for fallback rates, to increase chances of getting through
    */
    - if (offset > 0 ||
    + if ((offset > 0 && use_rts) ||
    (mi->sta->smps_mode == IEEE80211_SMPS_DYNAMIC &&
    group->streams > 1)) {
    ratetbl->rate[offset].count = ratetbl->rate[offset].count_rts;
    @@ -1426,7 +1428,8 @@ minstrel_ht_get_max_amsdu_len(struct minstrel_ht_sta *mi)
    }

    static void
    -minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
    +minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
    + bool use_rts)
    {
    struct ieee80211_sta_rates *rates;
    int i = 0;
    @@ -1436,15 +1439,15 @@ minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
    return;

    /* Start with max_tp_rate[0] */
    - minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate[0]);
    + minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate[0], use_rts);

    if (mp->hw->max_rates >= 3) {
    /* At least 3 tx rates supported, use max_tp_rate[1] next */
    - minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate[1]);
    + minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate[1], use_rts);
    }

    if (mp->hw->max_rates >= 2) {
    - minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_prob_rate);
    + minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_prob_rate, use_rts);
    }

    mi->sta->max_rc_amsdu_len = minstrel_ht_get_max_amsdu_len(mi);
    @@ -1705,7 +1708,7 @@ minstrel_ht_update_caps(void *priv, struct ieee80211_supported_band *sband,

    /* create an initial rate table with the lowest supported rates */
    minstrel_ht_update_stats(mp, mi);
    - minstrel_ht_update_rates(mp, mi);
    + minstrel_ht_update_rates(mp, mi, false);
    }

    static void
    --
    2.33.1
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