[PATCH 2/2] mac80211: use STA info in rate_control_send_low()

[Johannes Berg <johannes@sipsolutions.net>]

From: Johannes Berg <johannes.berg@intel.com>

Even if we have a station, we currently call rate_control_send_low()
with the NULL station unless further rate control (driver, minstrel)
has been initialized.

Change this so we can use more information about the station to use
a better rate. For example, when we associate with an AP, we will
now use the lowest rate it advertised as supported (that we can)
rather than the lowest mandatory rate. This aligns our behaviour
with most other 802.11 implementations.

To make this possible, we need to also ensure that we have non-zero
rates at all times, so in case we really have *nothing* pre-fill
the supp_rates bitmap with the very lowest mandatory bitmap (11b
and 11a on 2.4 and 5 GHz respectively).

Additionally, hostapd appears to be giving us an empty supported
rates bitmap (it can and should do better, since the STA must have
supported for at least the basic rates in the BSS), so ignore any
such bitmaps that would actually zero out the supp_rates, and in
that case just keep the pre-filled mandatory rates.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/mac80211/cfg.c      |  2 +-
 net/mac80211/mlme.c     |  7 ++++++-
 net/mac80211/rate.c     | 12 ++++++------
 net/mac80211/sta_info.c | 31 +++++++++++++++++++++++++++++++
 4 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 52e6a091b7e4..58c97e6dadb0 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1466,7 +1466,7 @@ static int sta_apply_parameters(struct ieee80211_local *local,
 			return ret;
 	}
 
-	if (params->supported_rates) {
+	if (params->supported_rates && params->supported_rates_len) {
 		ieee80211_parse_bitrates(&sdata->vif.bss_conf.chandef,
 					 sband, params->supported_rates,
 					 params->supported_rates_len,
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index b7a9fe3d5fcb..bc2fdadf69bc 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -4941,7 +4941,12 @@ static int ieee80211_prep_connection(struct ieee80211_sub_if_data *sdata,
 			basic_rates = BIT(min_rate_index);
 		}
 
-		new_sta->sta.supp_rates[cbss->channel->band] = rates;
+		if (rates)
+			new_sta->sta.supp_rates[cbss->channel->band] = rates;
+		else
+			sdata_info(sdata,
+				   "No rates found, keeping mandatory only\n");
+
 		sdata->vif.bss_conf.basic_rates = basic_rates;
 
 		/* cf. IEEE 802.11 9.2.12 */
diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index 09f89d004a70..bc3cedc653f0 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -886,11 +886,6 @@ void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
 	int i;
 
-	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;
@@ -900,9 +895,14 @@ void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 	if (ieee80211_hw_check(&sdata->local->hw, HAS_RATE_CONTROL))
 		return;
 
-	if (rate_control_send_low(ista, txrc))
+	if (rate_control_send_low(sta ? &sta->sta : NULL, txrc))
 		return;
 
+	if (sta && test_sta_flag(sta, WLAN_STA_RATE_CONTROL)) {
+		ista = &sta->sta;
+		priv_sta = sta->rate_ctrl_priv;
+	}
+
 	if (ista) {
 		spin_lock_bh(&sta->rate_ctrl_lock);
 		ref->ops->get_rate(ref->priv, ista, priv_sta, txrc);
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index a4932ee3595c..4b4774e07151 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -404,6 +404,37 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	for (i = 0; i < IEEE80211_NUM_TIDS; i++)
 		sta->last_seq_ctrl[i] = cpu_to_le16(USHRT_MAX);
 
+	for (i = 0; i < NUM_NL80211_BANDS; i++) {
+		u32 mandatory = 0;
+		int r;
+
+		if (!hw->wiphy->bands[i])
+			continue;
+
+		switch (i) {
+		case NL80211_BAND_2GHZ:
+			mandatory = IEEE80211_RATE_MANDATORY_B;
+			break;
+		case NL80211_BAND_5GHZ:
+			mandatory = IEEE80211_RATE_MANDATORY_G;
+			break;
+		case NL80211_BAND_60GHZ:
+			WARN_ON(1);
+			mandatory = 0;
+			break;
+		}
+
+		for (r = 0; r < hw->wiphy->bands[i]->n_bitrates; r++) {
+			struct ieee80211_rate *rate;
+
+			rate = &hw->wiphy->bands[i]->bitrates[r];
+
+			if (!(rate->flags & mandatory))
+				continue;
+			sta->sta.supp_rates[i] |= BIT(r);
+		}
+	}
+
 	sta->sta.smps_mode = IEEE80211_SMPS_OFF;
 	if (sdata->vif.type == NL80211_IFTYPE_AP ||
 	    sdata->vif.type == NL80211_IFTYPE_AP_VLAN) {
-- 
2.17.2