mac80211: retransmit TDLS teardown packet through AP if not ACKed

Since the TDLS peer station might not receive the teardown
packet (e.g., when in PS), this makes sure the packet is
retransmitted - this time through the AP - if the TDLS peer
didn't ACK the packet.
Signed-off-by: Liad Kaufman <liad.kaufman@intel.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/linux/ieee80211.h

@@ -19,6 +19,7 @@
 #include <linux/types.h>
 #include <linux/if_ether.h>
 #include <asm/byteorder.h>
+#include <asm/unaligned.h>
 
 /*
  * DS bit usage
@@ -2418,6 +2419,30 @@ static inline bool ieee80211_check_tim(const struct ieee80211_tim_ie *tim,
 	return !!(tim->virtual_map[index] & mask);
 }
 
+/**
+ * ieee80211_get_tdls_action - get tdls packet action (or -1, if not tdls packet)
+ * @skb: the skb containing the frame, length will not be checked
+ * @hdr_size: the size of the ieee80211_hdr that starts at skb->data
+ *
+ * This function assumes the frame is a data frame, and that the network header
+ * is in the correct place.
+ */
+static inline int ieee80211_get_tdls_action(struct sk_buff *skb, u32 hdr_size)
+{
+	if (!skb_is_nonlinear(skb) &&
+	    skb->len > (skb_network_offset(skb) + 2)) {
+		/* Point to where the indication of TDLS should start */
+		const u8 *tdls_data = skb_network_header(skb) - 2;
+
+		if (get_unaligned_be16(tdls_data) == ETH_P_TDLS &&
+		    tdls_data[2] == WLAN_TDLS_SNAP_RFTYPE &&
+		    tdls_data[3] == WLAN_CATEGORY_TDLS)
+			return tdls_data[4];
+	}
+
+	return -1;
+}
+
 /* convert time units */
 #define TU_TO_JIFFIES(x)	(usecs_to_jiffies((x) * 1024))
 #define TU_TO_EXP_TIME(x)	(jiffies + TU_TO_JIFFIES(x))

net/mac80211/ieee80211_i.h

@@ -525,8 +525,12 @@ struct ieee80211_if_managed {
 	struct ieee80211_vht_cap vht_capa; /* configured VHT overrides */
 	struct ieee80211_vht_cap vht_capa_mask; /* Valid parts of vht_capa */
 
+	/* TDLS support */
 	u8 tdls_peer[ETH_ALEN] __aligned(2);
 	struct delayed_work tdls_peer_del_work;
+	struct sk_buff *orig_teardown_skb; /* The original teardown skb */
+	struct sk_buff *teardown_skb; /* A copy to send through the AP */
+	spinlock_t teardown_lock; /* To lock changing teardown_skb */
 
 	/* WMM-AC TSPEC support */
 	struct ieee80211_sta_tx_tspec tx_tspec[IEEE80211_NUM_ACS];

net/mac80211/mlme.c

@@ -4003,6 +4003,11 @@ void ieee80211_sta_setup_sdata(struct ieee80211_sub_if_data *sdata)
 		ifmgd->req_smps = IEEE80211_SMPS_AUTOMATIC;
 	else
 		ifmgd->req_smps = IEEE80211_SMPS_OFF;
+
+	/* Setup TDLS data */
+	spin_lock_init(&ifmgd->teardown_lock);
+	ifmgd->teardown_skb = NULL;
+	ifmgd->orig_teardown_skb = NULL;
 }
 
 /* scan finished notification */
@@ -4865,6 +4870,13 @@ void ieee80211_mgd_stop(struct ieee80211_sub_if_data *sdata)
 	}
 	if (ifmgd->auth_data)
 		ieee80211_destroy_auth_data(sdata, false);
+	spin_lock_bh(&ifmgd->teardown_lock);
+	if (ifmgd->teardown_skb) {
+		kfree_skb(ifmgd->teardown_skb);
+		ifmgd->teardown_skb = NULL;
+		ifmgd->orig_teardown_skb = NULL;
+	}
+	spin_unlock_bh(&ifmgd->teardown_lock);
 	del_timer_sync(&ifmgd->timer);
 	sdata_unlock(sdata);
 }

net/mac80211/status.c

@@ -390,6 +390,46 @@ ieee80211_add_tx_radiotap_header(struct ieee80211_local *local,
 	}
 }
 
+/*
+ * Handles the tx for TDLS teardown frames.
+ * If the frame wasn't ACKed by the peer - it will be re-sent through the AP
+ */
+static void ieee80211_tdls_td_tx_handle(struct ieee80211_local *local,
+					struct ieee80211_sub_if_data *sdata,
+					struct sk_buff *skb, u32 flags)
+{
+	struct sk_buff *teardown_skb;
+	struct sk_buff *orig_teardown_skb;
+	bool is_teardown = false;
+
+	/* Get the teardown data we need and free the lock */
+	spin_lock(&sdata->u.mgd.teardown_lock);
+	teardown_skb = sdata->u.mgd.teardown_skb;
+	orig_teardown_skb = sdata->u.mgd.orig_teardown_skb;
+	if ((skb == orig_teardown_skb) && teardown_skb) {
+		sdata->u.mgd.teardown_skb = NULL;
+		sdata->u.mgd.orig_teardown_skb = NULL;
+		is_teardown = true;
+	}
+	spin_unlock(&sdata->u.mgd.teardown_lock);
+
+	if (is_teardown) {
+		/* This mechanism relies on being able to get ACKs */
+		WARN_ON(!(local->hw.flags &
+			  IEEE80211_HW_REPORTS_TX_ACK_STATUS));
+
+		/* Check if peer has ACKed */
+		if (flags & IEEE80211_TX_STAT_ACK) {
+			dev_kfree_skb_any(teardown_skb);
+		} else {
+			tdls_dbg(sdata,
+				 "TDLS Resending teardown through AP\n");
+
+			ieee80211_subif_start_xmit(teardown_skb, skb->dev);
+		}
+	}
+}
+
 static void ieee80211_report_used_skb(struct ieee80211_local *local,
 				      struct sk_buff *skb, bool dropped)
 {
@@ -426,7 +466,18 @@ static void ieee80211_report_used_skb(struct ieee80211_local *local,
 		if (!sdata) {
 			skb->dev = NULL;
 		} else if (info->flags & IEEE80211_TX_INTFL_MLME_CONN_TX) {
-			ieee80211_mgd_conn_tx_status(sdata, hdr->frame_control,
+			unsigned int hdr_size =
+				ieee80211_hdrlen(hdr->frame_control);
+
+			/* Check to see if packet is a TDLS teardown packet */
+			if (ieee80211_is_data(hdr->frame_control) &&
+			    (ieee80211_get_tdls_action(skb, hdr_size) ==
+			     WLAN_TDLS_TEARDOWN))
+				ieee80211_tdls_td_tx_handle(local, sdata, skb,
+							    info->flags);
+			else
+				ieee80211_mgd_conn_tx_status(sdata,
+							     hdr->frame_control,
 							     acked);
 		} else if (ieee80211_is_nullfunc(hdr->frame_control) ||
 			   ieee80211_is_qos_nullfunc(hdr->frame_control)) {

net/mac80211/tdls.c

@@ -512,11 +512,13 @@ ieee80211_tdls_prep_mgmt_packet(struct wiphy *wiphy, struct net_device *dev,
 	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 	struct ieee80211_local *local = sdata->local;
 	struct sk_buff *skb = NULL;
+	u32 flags = 0;
 	bool send_direct;
 	struct sta_info *sta;
 	int ret;
 
-	skb = dev_alloc_skb(local->hw.extra_tx_headroom +
+	skb = netdev_alloc_skb(dev,
+			       local->hw.extra_tx_headroom +
 			       max(sizeof(struct ieee80211_mgmt),
 				   sizeof(struct ieee80211_tdls_data)) +
 			       50 + /* supported rates */
@@ -623,9 +625,44 @@ ieee80211_tdls_prep_mgmt_packet(struct wiphy *wiphy, struct net_device *dev,
 		break;
 	}
 
+	/*
+	 * Set the WLAN_TDLS_TEARDOWN flag to indicate a teardown in progress.
+	 * Later, if no ACK is returned from peer, we will re-send the teardown
+	 * packet through the AP.
+	 */
+	if ((action_code == WLAN_TDLS_TEARDOWN) &&
+	    (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS)) {
+		struct sta_info *sta = NULL;
+		bool try_resend; /* Should we keep skb for possible resend */
+
+		/* If not sending directly to peer - no point in keeping skb */
+		rcu_read_lock();
+		sta = sta_info_get(sdata, peer);
+		try_resend = sta && test_sta_flag(sta, WLAN_STA_TDLS_PEER_AUTH);
+		rcu_read_unlock();
+
+		spin_lock_bh(&sdata->u.mgd.teardown_lock);
+		if (try_resend && !sdata->u.mgd.teardown_skb) {
+			/* Mark it as requiring TX status callback  */
+			flags |= IEEE80211_TX_CTL_REQ_TX_STATUS |
+				 IEEE80211_TX_INTFL_MLME_CONN_TX;
+
+			/*
+			 * skb is copied since mac80211 will later set
+			 * properties that might not be the same as the AP,
+			 * such as encryption, QoS, addresses, etc.
+			 *
+			 * No problem if skb_copy() fails, so no need to check.
+			 */
+			sdata->u.mgd.teardown_skb = skb_copy(skb, GFP_ATOMIC);
+			sdata->u.mgd.orig_teardown_skb = skb;
+		}
+		spin_unlock_bh(&sdata->u.mgd.teardown_lock);
+	}
+
 	/* disable bottom halves when entering the Tx path */
 	local_bh_disable();
-	ret = ieee80211_subif_start_xmit(skb, dev);
+	__ieee80211_subif_start_xmit(skb, dev, flags);
 	local_bh_enable();
 
 	return ret;