[MAC80211]: improved short preamble handling

Similarly to CTS protection, whether short preambles are used for 802.11b
transmissions should be a per-subif setting, not device global.

For STAs, this patch makes short preamble handling automatic based on the ERP
IE. For APs, hostapd still uses the prism ioctls, but the write ioctl has been
restricted to AP-only subifs.

ieee80211_txrx_data.short_preamble (an unused field) was removed.

Unfortunately, some API changes were required for the following functions:
 - ieee80211_generic_frame_duration
 - ieee80211_rts_duration
 - ieee80211_ctstoself_duration
 - ieee80211_rts_get
 - ieee80211_ctstoself_get
Affected drivers were updated accordingly.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: Jiri Benc <jbenc@suse.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

5 files changed, 74 insertions, 24 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index e76a5867895..b0af6e9f531 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -127,7 +127,6 @@ struct ieee80211_txrx_data {
 			struct ieee80211_tx_control *control;
 			unsigned int unicast:1;
 			unsigned int ps_buffered:1;
-			unsigned int short_preamble:1;
 			unsigned int probe_last_frag:1;
 			struct ieee80211_hw_mode *mode;
 			struct ieee80211_rate *rate;
@@ -286,6 +285,11 @@ struct ieee80211_sub_if_data {
 	unsigned int promisc:1;
 	unsigned int use_protection:1; /* CTS protect ERP frames */
 
+	/* use short preamble with IEEE 802.11b: this flag is set when the AP
+	 * or beacon generator reports that there are no present stations that
+	 * cannot support short preambles */
+	unsigned int short_preamble:1;
+
 	struct net_device_stats stats;
 	int drop_unencrypted;
 	int eapol; /* 0 = process EAPOL frames as normal data frames,
@@ -447,7 +451,6 @@ struct ieee80211_local {
 	int fragmentation_threshold;
 	int short_retry_limit; /* dot11ShortRetryLimit */
 	int long_retry_limit; /* dot11LongRetryLimit */
-	int short_preamble; /* use short preamble with IEEE 802.11b */
 
 	struct crypto_blkcipher *wep_tx_tfm;
 	struct crypto_blkcipher *wep_rx_tfm;
diff --git a/net/mac80211/ieee80211_ioctl.c b/net/mac80211/ieee80211_ioctl.c
index e7904db5532..8292431ac48 100644
--- a/net/mac80211/ieee80211_ioctl.c
+++ b/net/mac80211/ieee80211_ioctl.c
@@ -1061,7 +1061,10 @@ static int ieee80211_ioctl_prism2_param(struct net_device *dev,
 		break;
 
 	case PRISM2_PARAM_PREAMBLE:
-		local->short_preamble = value;
+		if (sdata->type != IEEE80211_IF_TYPE_AP)
+			ret = -ENOENT;
+		else
+			sdata->short_preamble = value;
 		break;
 
 	case PRISM2_PARAM_STAT_TIME:
@@ -1184,7 +1187,7 @@ static int ieee80211_ioctl_get_prism2_param(struct net_device *dev,
 		break;
 
 	case PRISM2_PARAM_PREAMBLE:
-		*param = local->short_preamble;
+		*param = sdata->short_preamble;
 		break;
 
 	case PRISM2_PARAM_STAT_TIME:
diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c
index 8e6548974a9..0f5f8131bd7 100644
--- a/net/mac80211/ieee80211_sta.c
+++ b/net/mac80211/ieee80211_sta.c
@@ -318,6 +318,7 @@ static void ieee80211_handle_erp_ie(struct net_device *dev, u8 erp_value)
 	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 	struct ieee80211_if_sta *ifsta = &sdata->u.sta;
 	int use_protection = (erp_value & WLAN_ERP_USE_PROTECTION) != 0;
+	int preamble_mode = (erp_value & WLAN_ERP_BARKER_PREAMBLE) != 0;
 
 	if (use_protection != sdata->use_protection) {
 		if (net_ratelimit()) {
@@ -329,6 +330,18 @@ static void ieee80211_handle_erp_ie(struct net_device *dev, u8 erp_value)
 		}
 		sdata->use_protection = use_protection;
 	}
+
+	if (!preamble_mode != sdata->short_preamble) {
+		if (net_ratelimit()) {
+			printk(KERN_DEBUG "%s: switched to %s barker preamble"
+			       " (BSSID=" MAC_FMT ")\n",
+			       dev->name,
+			       (preamble_mode == WLAN_ERP_PREAMBLE_SHORT) ?
+					"short" : "long",
+			       MAC_ARG(ifsta->bssid));
+		}
+		sdata->short_preamble = !preamble_mode;
+	}
 }
 
 
@@ -415,6 +428,7 @@ static void ieee80211_set_associated(struct net_device *dev,
 		ieee80211_sta_send_associnfo(dev, ifsta);
 	} else {
 		netif_carrier_off(dev);
+		sdata->short_preamble = 0;
 		sdata->use_protection = 0;
 		memset(wrqu.ap_addr.sa_data, 0, ETH_ALEN);
 	}
@@ -2281,7 +2295,7 @@ static int ieee80211_sta_join_ibss(struct net_device *dev,
 			       "for IBSS beacon\n", dev->name);
 			break;
 		}
-		control.tx_rate = (local->short_preamble &&
+		control.tx_rate = (sdata->short_preamble &&
 				   (rate->flags & IEEE80211_RATE_PREAMBLE2)) ?
 			rate->val2 : rate->val;
 		control.antenna_sel_tx = local->hw.conf.antenna_sel_tx;
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 532cf5127b7..36761c7139b 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -173,7 +173,7 @@ static u16 ieee80211_duration(struct ieee80211_txrx_data *tx, int group_addr,
 	 * to closest integer */
 
 	dur = ieee80211_frame_duration(local, 10, rate, erp,
-				       local->short_preamble);
+				       tx->sdata->short_preamble);
 
 	if (next_frag_len) {
 		/* Frame is fragmented: duration increases with time needed to
@@ -182,7 +182,7 @@ static u16 ieee80211_duration(struct ieee80211_txrx_data *tx, int group_addr,
 		/* next fragment */
 		dur += ieee80211_frame_duration(local, next_frag_len,
 						txrate->rate, erp,
-						local->short_preamble);
+						tx->sdata->short_preamble);
 	}
 
 	return dur;
@@ -627,12 +627,6 @@ ieee80211_tx_h_rate_ctrl(struct ieee80211_txrx_data *tx)
 		tx->u.tx.control->rate = tx->u.tx.rate;
 	}
 	tx->u.tx.control->tx_rate = tx->u.tx.rate->val;
-	if ((tx->u.tx.rate->flags & IEEE80211_RATE_PREAMBLE2) &&
-	    tx->local->short_preamble &&
-	    (!tx->sta || (tx->sta->flags & WLAN_STA_SHORT_PREAMBLE))) {
-		tx->u.tx.short_preamble = 1;
-		tx->u.tx.control->tx_rate = tx->u.tx.rate->val2;
-	}
 
 	return TXRX_CONTINUE;
 }
@@ -641,6 +635,7 @@ static ieee80211_txrx_result
 ieee80211_tx_h_misc(struct ieee80211_txrx_data *tx)
 {
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) tx->skb->data;
+	u16 fc = le16_to_cpu(hdr->frame_control);
 	u16 dur;
 	struct ieee80211_tx_control *control = tx->u.tx.control;
 	struct ieee80211_hw_mode *mode = tx->u.tx.mode;
@@ -677,6 +672,16 @@ ieee80211_tx_h_misc(struct ieee80211_txrx_data *tx)
 	    !(control->flags & IEEE80211_TXCTL_USE_RTS_CTS))
 		control->flags |= IEEE80211_TXCTL_USE_CTS_PROTECT;
 
+	/* Transmit data frames using short preambles if the driver supports
+	 * short preambles at the selected rate and short preambles are
+	 * available on the network at the current point in time. */
+	if (((fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA) &&
+	    (tx->u.tx.rate->flags & IEEE80211_RATE_PREAMBLE2) &&
+	    tx->sdata->short_preamble &&
+	    (!tx->sta || (tx->sta->flags & WLAN_STA_SHORT_PREAMBLE))) {
+		tx->u.tx.control->tx_rate = tx->u.tx.rate->val2;
+	}
+
 	/* Setup duration field for the first fragment of the frame. Duration
 	 * for remaining fragments will be updated when they are being sent
 	 * to low-level driver in ieee80211_tx(). */
@@ -1750,7 +1755,7 @@ struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw, int if_id,
 			return NULL;
 		}
 
-		control->tx_rate = (local->short_preamble &&
+		control->tx_rate = (sdata->short_preamble &&
 				    (rate->flags & IEEE80211_RATE_PREAMBLE2)) ?
 			rate->val2 : rate->val;
 		control->antenna_sel_tx = local->hw.conf.antenna_sel_tx;
@@ -1765,7 +1770,7 @@ struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw, int if_id,
 }
 EXPORT_SYMBOL(ieee80211_beacon_get);
 
-void ieee80211_rts_get(struct ieee80211_hw *hw,
+void ieee80211_rts_get(struct ieee80211_hw *hw, int if_id,
 		       const void *frame, size_t frame_len,
 		       const struct ieee80211_tx_control *frame_txctl,
 		       struct ieee80211_rts *rts)
@@ -1775,13 +1780,13 @@ void ieee80211_rts_get(struct ieee80211_hw *hw,
 
 	fctl = IEEE80211_FTYPE_CTL | IEEE80211_STYPE_RTS;
 	rts->frame_control = cpu_to_le16(fctl);
-	rts->duration = ieee80211_rts_duration(hw, frame_len, frame_txctl);
+	rts->duration = ieee80211_rts_duration(hw, if_id, frame_len, frame_txctl);
 	memcpy(rts->ra, hdr->addr1, sizeof(rts->ra));
 	memcpy(rts->ta, hdr->addr2, sizeof(rts->ta));
 }
 EXPORT_SYMBOL(ieee80211_rts_get);
 
-void ieee80211_ctstoself_get(struct ieee80211_hw *hw,
+void ieee80211_ctstoself_get(struct ieee80211_hw *hw, int if_id,
 			     const void *frame, size_t frame_len,
 			     const struct ieee80211_tx_control *frame_txctl,
 			     struct ieee80211_cts *cts)
@@ -1791,7 +1796,7 @@ void ieee80211_ctstoself_get(struct ieee80211_hw *hw,
 
 	fctl = IEEE80211_FTYPE_CTL | IEEE80211_STYPE_CTS;
 	cts->frame_control = cpu_to_le16(fctl);
-	cts->duration = ieee80211_ctstoself_duration(hw, frame_len, frame_txctl);
+	cts->duration = ieee80211_ctstoself_duration(hw, if_id, frame_len, frame_txctl);
 	memcpy(cts->ra, hdr->addr1, sizeof(cts->ra));
 }
 EXPORT_SYMBOL(ieee80211_ctstoself_get);
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index c4565830947..091ac0d634a 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -314,31 +314,46 @@ int ieee80211_frame_duration(struct ieee80211_local *local, size_t len,
 }
 
 /* Exported duration function for driver use */
-__le16 ieee80211_generic_frame_duration(struct ieee80211_hw *hw,
+__le16 ieee80211_generic_frame_duration(struct ieee80211_hw *hw, int if_id,
 					size_t frame_len, int rate)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
+	struct net_device *bdev = dev_get_by_index(if_id);
+	struct ieee80211_sub_if_data *sdata;
 	u16 dur;
 	int erp;
 
+	if (unlikely(!bdev))
+		return 0;
+
+	sdata = IEEE80211_DEV_TO_SUB_IF(bdev);
 	erp = ieee80211_is_erp_rate(hw->conf.phymode, rate);
 	dur = ieee80211_frame_duration(local, frame_len, rate,
-				       erp, local->short_preamble);
+				       erp, sdata->short_preamble);
 
+	dev_put(bdev);
 	return cpu_to_le16(dur);
 }
 EXPORT_SYMBOL(ieee80211_generic_frame_duration);
 
-__le16 ieee80211_rts_duration(struct ieee80211_hw *hw,
+__le16 ieee80211_rts_duration(struct ieee80211_hw *hw, int if_id,
 			      size_t frame_len,
 			      const struct ieee80211_tx_control *frame_txctl)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 	struct ieee80211_rate *rate;
-	int short_preamble = local->short_preamble;
+	struct net_device *bdev = dev_get_by_index(if_id);
+	struct ieee80211_sub_if_data *sdata;
+	int short_preamble;
 	int erp;
 	u16 dur;
 
+	if (unlikely(!bdev))
+		return 0;
+
+	sdata = IEEE80211_DEV_TO_SUB_IF(bdev);
+	short_preamble = sdata->short_preamble;
+
 	rate = frame_txctl->rts_rate;
 	erp = !!(rate->flags & IEEE80211_RATE_ERP);
 
@@ -352,20 +367,29 @@ __le16 ieee80211_rts_duration(struct ieee80211_hw *hw,
 	dur += ieee80211_frame_duration(local, 10, rate->rate,
 					erp, short_preamble);
 
+	dev_put(bdev);
 	return cpu_to_le16(dur);
 }
 EXPORT_SYMBOL(ieee80211_rts_duration);
 
-__le16 ieee80211_ctstoself_duration(struct ieee80211_hw *hw,
+__le16 ieee80211_ctstoself_duration(struct ieee80211_hw *hw, int if_id,
 				    size_t frame_len,
 				    const struct ieee80211_tx_control *frame_txctl)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
 	struct ieee80211_rate *rate;
-	int short_preamble = local->short_preamble;
+	struct net_device *bdev = dev_get_by_index(if_id);
+	struct ieee80211_sub_if_data *sdata;
+	int short_preamble;
 	int erp;
 	u16 dur;
 
+	if (unlikely(!bdev))
+		return 0;
+
+	sdata = IEEE80211_DEV_TO_SUB_IF(bdev);
+	short_preamble = sdata->short_preamble;
+
 	rate = frame_txctl->rts_rate;
 	erp = !!(rate->flags & IEEE80211_RATE_ERP);
 
@@ -378,6 +402,7 @@ __le16 ieee80211_ctstoself_duration(struct ieee80211_hw *hw,
 						erp, short_preamble);
 	}
 
+	dev_put(bdev);
 	return cpu_to_le16(dur);
 }
 EXPORT_SYMBOL(ieee80211_ctstoself_duration);