mac80211: improve the rate control API

Allow rate control modules to pass a rate selection table to mac80211
and the driver. This allows drivers to fetch the most recent rate
selection from the sta pointer for already buffered frames. This allows
rate control to respond faster to sudden link changes and it is also a
step towards adding minstrel_ht support to drivers like iwlwifi.

When a driver sets IEEE80211_HW_SUPPORTS_RC_TABLE, mac80211 will not
fill info->control.rates with rates from the rate table (to preserve
explicit overrides by the rate control module). The driver then
explicitly calls ieee80211_get_tx_rates to merge overrides from
info->control.rates with defaults from the sta rate table.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 268 insertions, 59 deletions

diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index 5d545dd..0d51877 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -252,6 +252,25 @@ rate_lowest_non_cck_index(struct ieee80211_supported_band *sband,
 	return 0;
 }
 
+static void __rate_control_send_low(struct ieee80211_hw *hw,
+				    struct ieee80211_supported_band *sband,
+				    struct ieee80211_sta *sta,
+				    struct ieee80211_tx_info *info)
+{
+	if ((sband->band != IEEE80211_BAND_2GHZ) ||
+	    !(info->flags & IEEE80211_TX_CTL_NO_CCK_RATE))
+		info->control.rates[0].idx = rate_lowest_index(sband, sta);
+	else
+		info->control.rates[0].idx =
+			rate_lowest_non_cck_index(sband, sta);
+
+	info->control.rates[0].count =
+		(info->flags & IEEE80211_TX_CTL_NO_ACK) ?
+		1 : hw->max_rate_tries;
+
+	info->control.skip_table = 1;
+}
+
 
 bool rate_control_send_low(struct ieee80211_sta *sta,
 			   void *priv_sta,
@@ -262,16 +281,8 @@ bool rate_control_send_low(struct ieee80211_sta *sta,
 	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;
+		__rate_control_send_low(txrc->hw, sband, sta, info);
+
 		if (!sta && txrc->bss) {
 			mcast_rate = txrc->bss_conf->mcast_rate[sband->band];
 			if (mcast_rate > 0) {
@@ -355,7 +366,8 @@ static bool rate_idx_match_mcs_mask(struct ieee80211_tx_rate *rate,
 
 
 static void rate_idx_match_mask(struct ieee80211_tx_rate *rate,
-				struct ieee80211_tx_rate_control *txrc,
+				struct ieee80211_supported_band *sband,
+				enum nl80211_chan_width chan_width,
 				u32 mask,
 				u8 mcs_mask[IEEE80211_HT_MCS_MASK_LEN])
 {
@@ -375,27 +387,17 @@ static void rate_idx_match_mask(struct ieee80211_tx_rate *rate,
 				  IEEE80211_TX_RC_USE_SHORT_PREAMBLE);
 		alt_rate.count = rate->count;
 		if (rate_idx_match_legacy_mask(&alt_rate,
-					       txrc->sband->n_bitrates,
-					       mask)) {
+					       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))
+		if (rate_idx_match_legacy_mask(rate, sband->n_bitrates, mask))
 			return;
 
 		/* if HT BSS, and we handle a data frame, also try HT rates */
-		if (txrc->bss_conf->chandef.width == NL80211_CHAN_WIDTH_20_NOHT)
-			return;
-
-		fc = hdr->frame_control;
-		if (!ieee80211_is_data(fc))
+		if (chan_width == NL80211_CHAN_WIDTH_20_NOHT)
 			return;
 
 		alt_rate.idx = 0;
@@ -408,7 +410,7 @@ static void rate_idx_match_mask(struct ieee80211_tx_rate *rate,
 
 		alt_rate.flags |= IEEE80211_TX_RC_MCS;
 
-		if (txrc->bss_conf->chandef.width == NL80211_CHAN_WIDTH_40)
+		if (chan_width == NL80211_CHAN_WIDTH_40)
 			alt_rate.flags |= IEEE80211_TX_RC_40_MHZ_WIDTH;
 
 		if (rate_idx_match_mcs_mask(&alt_rate, mcs_mask)) {
@@ -426,6 +428,228 @@ static void rate_idx_match_mask(struct ieee80211_tx_rate *rate,
 	 */
 }
 
+static void rate_fixup_ratelist(struct ieee80211_vif *vif,
+				struct ieee80211_supported_band *sband,
+				struct ieee80211_tx_info *info,
+				struct ieee80211_tx_rate *rates,
+				int max_rates)
+{
+	struct ieee80211_rate *rate;
+	bool inval = false;
+	int i;
+
+	/*
+	 * Set up the RTS/CTS rate as the fastest basic rate
+	 * that is not faster than the data rate unless there
+	 * is no basic rate slower than the data rate, in which
+	 * case we pick the slowest basic rate
+	 *
+	 * XXX: Should this check all retry rates?
+	 */
+	if (!(rates[0].flags & IEEE80211_TX_RC_MCS)) {
+		u32 basic_rates = vif->bss_conf.basic_rates;
+		s8 baserate = basic_rates ? ffs(basic_rates - 1) : 0;
+
+		rate = &sband->bitrates[rates[0].idx];
+
+		for (i = 0; i < sband->n_bitrates; i++) {
+			/* must be a basic rate */
+			if (!(basic_rates & BIT(i)))
+				continue;
+			/* must not be faster than the data rate */
+			if (sband->bitrates[i].bitrate > rate->bitrate)
+				continue;
+			/* maximum */
+			if (sband->bitrates[baserate].bitrate <
+			     sband->bitrates[i].bitrate)
+				baserate = i;
+		}
+
+		info->control.rts_cts_rate_idx = baserate;
+	}
+
+	for (i = 0; i < max_rates; i++) {
+		/*
+		 * make sure there's no valid rate following
+		 * an invalid one, just in case drivers don't
+		 * take the API seriously to stop at -1.
+		 */
+		if (inval) {
+			rates[i].idx = -1;
+			continue;
+		}
+		if (rates[i].idx < 0) {
+			inval = true;
+			continue;
+		}
+
+		/*
+		 * For now assume MCS is already set up correctly, this
+		 * needs to be fixed.
+		 */
+		if (rates[i].flags & IEEE80211_TX_RC_MCS) {
+			WARN_ON(rates[i].idx > 76);
+
+			if (!(rates[i].flags & IEEE80211_TX_RC_USE_RTS_CTS) &&
+			    info->control.use_cts_prot)
+				rates[i].flags |=
+					IEEE80211_TX_RC_USE_CTS_PROTECT;
+			continue;
+		}
+
+		if (rates[i].flags & IEEE80211_TX_RC_VHT_MCS) {
+			WARN_ON(ieee80211_rate_get_vht_mcs(&rates[i]) > 9);
+			continue;
+		}
+
+		/* set up RTS protection if desired */
+		if (info->control.use_rts) {
+			rates[i].flags |= IEEE80211_TX_RC_USE_RTS_CTS;
+			info->control.use_cts_prot = false;
+		}
+
+		/* RC is busted */
+		if (WARN_ON_ONCE(rates[i].idx >= sband->n_bitrates)) {
+			rates[i].idx = -1;
+			continue;
+		}
+
+		rate = &sband->bitrates[rates[i].idx];
+
+		/* set up short preamble */
+		if (info->control.short_preamble &&
+		    rate->flags & IEEE80211_RATE_SHORT_PREAMBLE)
+			rates[i].flags |= IEEE80211_TX_RC_USE_SHORT_PREAMBLE;
+
+		/* set up G protection */
+		if (!(rates[i].flags & IEEE80211_TX_RC_USE_RTS_CTS) &&
+		    info->control.use_cts_prot &&
+		    rate->flags & IEEE80211_RATE_ERP_G)
+			rates[i].flags |= IEEE80211_TX_RC_USE_CTS_PROTECT;
+	}
+}
+
+
+static void rate_control_fill_sta_table(struct ieee80211_sta *sta,
+					struct ieee80211_tx_info *info,
+					struct ieee80211_tx_rate *rates,
+					int max_rates)
+{
+	struct ieee80211_sta_rates *ratetbl = NULL;
+	int i;
+
+	if (sta && !info->control.skip_table)
+		ratetbl = rcu_dereference(sta->rates);
+
+	/* Fill remaining rate slots with data from the sta rate table. */
+	max_rates = min_t(int, max_rates, IEEE80211_TX_RATE_TABLE_SIZE);
+	for (i = 0; i < max_rates; i++) {
+		if (i < ARRAY_SIZE(info->control.rates) &&
+		    info->control.rates[i].idx >= 0 &&
+		    info->control.rates[i].count) {
+			if (rates != info->control.rates)
+				rates[i] = info->control.rates[i];
+		} else if (ratetbl) {
+			rates[i].idx = ratetbl->rate[i].idx;
+			rates[i].flags = ratetbl->rate[i].flags;
+			if (info->control.use_rts)
+				rates[i].count = ratetbl->rate[i].count_rts;
+			else if (info->control.use_cts_prot)
+				rates[i].count = ratetbl->rate[i].count_cts;
+			else
+				rates[i].count = ratetbl->rate[i].count;
+		} else {
+			rates[i].idx = -1;
+			rates[i].count = 0;
+		}
+
+		if (rates[i].idx < 0 || !rates[i].count)
+			break;
+	}
+}
+
+static void rate_control_apply_mask(struct ieee80211_sub_if_data *sdata,
+				    struct ieee80211_sta *sta,
+				    struct ieee80211_supported_band *sband,
+				    struct ieee80211_tx_info *info,
+				    struct ieee80211_tx_rate *rates,
+				    int max_rates)
+{
+	enum nl80211_chan_width chan_width;
+	u8 mcs_mask[IEEE80211_HT_MCS_MASK_LEN];
+	bool has_mcs_mask;
+	u32 mask;
+	int i;
+
+	/*
+	 * 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];
+	has_mcs_mask = sdata->rc_has_mcs_mask[info->band];
+	if (mask == (1 << sband->n_bitrates) - 1 && !has_mcs_mask)
+		return;
+
+	if (has_mcs_mask)
+		memcpy(mcs_mask, sdata->rc_rateidx_mcs_mask[info->band],
+		       sizeof(mcs_mask));
+	else
+		memset(mcs_mask, 0xff, sizeof(mcs_mask));
+
+	if (sta) {
+		/* Filter out rates that the STA does not support */
+		mask &= sta->supp_rates[info->band];
+		for (i = 0; i < sizeof(mcs_mask); i++)
+			mcs_mask[i] &= 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.
+	 */
+	chan_width = sdata->vif.bss_conf.chandef.width;
+	for (i = 0; i < max_rates; i++) {
+		/* Skip invalid rates */
+		if (rates[i].idx < 0)
+			break;
+
+		rate_idx_match_mask(&rates[i], sband, mask, chan_width,
+				    mcs_mask);
+	}
+}
+
+void ieee80211_get_tx_rates(struct ieee80211_vif *vif,
+			    struct ieee80211_sta *sta,
+			    struct sk_buff *skb,
+			    struct ieee80211_tx_rate *dest,
+			    int max_rates)
+{
+	struct ieee80211_sub_if_data *sdata;
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_supported_band *sband;
+
+	rate_control_fill_sta_table(sta, info, dest, max_rates);
+
+	if (!vif)
+		return;
+
+	sdata = vif_to_sdata(vif);
+	sband = sdata->local->hw.wiphy->bands[info->band];
+
+	if (ieee80211_is_data(hdr->frame_control))
+		rate_control_apply_mask(sdata, sta, sband, info, dest, max_rates);
+
+	if (dest[0].idx < 0)
+		__rate_control_send_low(&sdata->local->hw, sband, sta, info);
+
+	if (sta)
+		rate_fixup_ratelist(vif, sband, info, dest, max_rates);
+}
+EXPORT_SYMBOL(ieee80211_get_tx_rates);
+
 void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 			   struct sta_info *sta,
 			   struct ieee80211_tx_rate_control *txrc)
@@ -435,8 +659,6 @@ void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 	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;
@@ -454,40 +676,27 @@ void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 
 	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];
-	if (mask != (1 << txrc->sband->n_bitrates) - 1 || txrc->rate_idx_mcs_mask) {
-		if (txrc->rate_idx_mcs_mask)
-			memcpy(mcs_mask, txrc->rate_idx_mcs_mask, sizeof(mcs_mask));
-		else
-			memset(mcs_mask, 0xff, sizeof(mcs_mask));
-
-		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);
-		}
-	}
+	if (sdata->local->hw.flags & IEEE80211_HW_SUPPORTS_RC_TABLE)
+		return;
+
+	ieee80211_get_tx_rates(&sdata->vif, ista, txrc->skb,
+			       info->control.rates,
+			       ARRAY_SIZE(info->control.rates));
+}
 
-	BUG_ON(info->control.rates[0].idx < 0);
+int rate_control_set_rates(struct ieee80211_hw *hw,
+			   struct ieee80211_sta *pubsta,
+			   struct ieee80211_sta_rates *rates)
+{
+	struct ieee80211_sta_rates *old = rcu_dereference(pubsta->rates);
+
+	rcu_assign_pointer(pubsta->rates, rates);
+	if (old)
+		kfree_rcu(old, rcu_head);
+
+	return 0;
 }
+EXPORT_SYMBOL(rate_control_set_rates);
 
 int ieee80211_init_rate_ctrl_alg(struct ieee80211_local *local,
 				 const char *name)