carl9170: fix HT peer BA session corruption

This patch adds an alternative tx status path
for BlockAck Requests as the hardware doesn't
recognize that a BlockAck Requests is usually
acked with a BlockAck and not a legacy ACK.

Without this patch, the stack would constantly
resent old and stale BARs. So, depending on the
receiver stack, this could lead to:

 - "stuck" ba sessions and package loss, as the
   stale BAR would reset the sequence each time.

 - lots of reorder releases.

 - ...

Reported-by: Sean Patrick Santos <quantheory@gmail.com>
Reported-by: Mikołaj Kuligowski <mikolaj.q@wp.pl>
Reported-by: Per-Erik Westerberg <per-erik.westerberg@bredband.net>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/carl9170/carl9170.h

@@ -289,6 +289,7 @@ struct ar9170 {
 		unsigned int mem_block_size;
 		unsigned int rx_size;
 		unsigned int tx_seq_table;
+		bool ba_filter;
 	} fw;
 
 	/* interface configuration combinations */
@@ -425,6 +426,10 @@ struct ar9170 {
 	struct sk_buff *rx_failover;
 	int rx_failover_missing;
 
+	/* FIFO for collecting outstanding BlockAckRequest */
+	struct list_head bar_list[__AR9170_NUM_TXQ];
+	spinlock_t bar_list_lock[__AR9170_NUM_TXQ];
+
 #ifdef CONFIG_CARL9170_WPC
 	struct {
 		bool pbc_state;
@@ -468,6 +473,12 @@ enum carl9170_ps_off_override_reasons {
 	PS_OFF_BCN	= BIT(1),
 };
 
+struct carl9170_bar_list_entry {
+	struct list_head list;
+	struct rcu_head head;
+	struct sk_buff *skb;
+};
+
 struct carl9170_ba_stats {
 	u8 ampdu_len;
 	u8 ampdu_ack_len;

drivers/net/wireless/ath/carl9170/fw.c

@@ -307,6 +307,9 @@ static int carl9170_fw(struct ar9170 *ar, const __u8 *data, size_t len)
 	if (SUPP(CARL9170FW_WOL))
 		device_set_wakeup_enable(&ar->udev->dev, true);
 
+	if (SUPP(CARL9170FW_RX_BA_FILTER))
+		ar->fw.ba_filter = true;
+
 	if_comb_types = BIT(NL80211_IFTYPE_STATION) |
 			BIT(NL80211_IFTYPE_P2P_CLIENT);
 

drivers/net/wireless/ath/carl9170/main.c

@@ -949,6 +949,9 @@ static void carl9170_op_configure_filter(struct ieee80211_hw *hw,
 	if (ar->fw.rx_filter && changed_flags & ar->rx_filter_caps) {
 		u32 rx_filter = 0;
 
+		if (!ar->fw.ba_filter)
+			rx_filter |= CARL9170_RX_FILTER_CTL_OTHER;
+
 		if (!(*new_flags & (FIF_FCSFAIL | FIF_PLCPFAIL)))
 			rx_filter |= CARL9170_RX_FILTER_BAD;
 
@@ -1753,6 +1756,9 @@ void *carl9170_alloc(size_t priv_size)
 	for (i = 0; i < ar->hw->queues; i++) {
 		skb_queue_head_init(&ar->tx_status[i]);
 		skb_queue_head_init(&ar->tx_pending[i]);
+
+		INIT_LIST_HEAD(&ar->bar_list[i]);
+		spin_lock_init(&ar->bar_list_lock[i]);
 	}
 	INIT_WORK(&ar->ps_work, carl9170_ps_work);
 	INIT_WORK(&ar->ping_work, carl9170_ping_work);

drivers/net/wireless/ath/carl9170/rx.c

@@ -576,6 +576,53 @@ static void carl9170_ps_beacon(struct ar9170 *ar, void *data, unsigned int len)
 	}
 }
 
+static void carl9170_ba_check(struct ar9170 *ar, void *data, unsigned int len)
+{
+	struct ieee80211_bar *bar = (void *) data;
+	struct carl9170_bar_list_entry *entry;
+	unsigned int queue;
+
+	if (likely(!ieee80211_is_back(bar->frame_control)))
+		return;
+
+	if (len <= sizeof(*bar) + FCS_LEN)
+		return;
+
+	queue = TID_TO_WME_AC(((le16_to_cpu(bar->control) &
+		IEEE80211_BAR_CTRL_TID_INFO_MASK) >>
+		IEEE80211_BAR_CTRL_TID_INFO_SHIFT) & 7);
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(entry, &ar->bar_list[queue], list) {
+		struct sk_buff *entry_skb = entry->skb;
+		struct _carl9170_tx_superframe *super = (void *)entry_skb->data;
+		struct ieee80211_bar *entry_bar = (void *)super->frame_data;
+
+#define TID_CHECK(a, b) (						\
+	((a) & cpu_to_le16(IEEE80211_BAR_CTRL_TID_INFO_MASK)) ==	\
+	((b) & cpu_to_le16(IEEE80211_BAR_CTRL_TID_INFO_MASK)))		\
+
+		if (bar->start_seq_num == entry_bar->start_seq_num &&
+		    TID_CHECK(bar->control, entry_bar->control) &&
+		    compare_ether_addr(bar->ra, entry_bar->ta) == 0 &&
+		    compare_ether_addr(bar->ta, entry_bar->ra) == 0) {
+			struct ieee80211_tx_info *tx_info;
+
+			tx_info = IEEE80211_SKB_CB(entry_skb);
+			tx_info->flags |= IEEE80211_TX_STAT_ACK;
+
+			spin_lock_bh(&ar->bar_list_lock[queue]);
+			list_del_rcu(&entry->list);
+			spin_unlock_bh(&ar->bar_list_lock[queue]);
+			kfree_rcu(entry, head);
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+#undef TID_CHECK
+}
+
 static bool carl9170_ampdu_check(struct ar9170 *ar, u8 *buf, u8 ms)
 {
 	__le16 fc;
@@ -738,6 +785,8 @@ static void carl9170_handle_mpdu(struct ar9170 *ar, u8 *buf, int len)
 
 	carl9170_ps_beacon(ar, buf, mpdu_len);
 
+	carl9170_ba_check(ar, buf, mpdu_len);
+
 	skb = carl9170_rx_copy_data(buf, mpdu_len);
 	if (!skb)
 		goto drop;

drivers/net/wireless/ath/carl9170/tx.c

@@ -436,6 +436,45 @@ out_rcu:
 	rcu_read_unlock();
 }
 
+static void carl9170_tx_bar_status(struct ar9170 *ar, struct sk_buff *skb,
+	struct ieee80211_tx_info *tx_info)
+{
+	struct _carl9170_tx_superframe *super = (void *) skb->data;
+	struct ieee80211_bar *bar = (void *) super->frame_data;
+
+	/*
+	 * Unlike all other frames, the status report for BARs does
+	 * not directly come from the hardware as it is incapable of
+	 * matching a BA to a previously send BAR.
+	 * Instead the RX-path will scan for incoming BAs and set the
+	 * IEEE80211_TX_STAT_ACK if it sees one that was likely
+	 * caused by a BAR from us.
+	 */
+
+	if (unlikely(ieee80211_is_back_req(bar->frame_control)) &&
+	   !(tx_info->flags & IEEE80211_TX_STAT_ACK)) {
+		struct carl9170_bar_list_entry *entry;
+		int queue = skb_get_queue_mapping(skb);
+
+		rcu_read_lock();
+		list_for_each_entry_rcu(entry, &ar->bar_list[queue], list) {
+			if (entry->skb == skb) {
+				spin_lock_bh(&ar->bar_list_lock[queue]);
+				list_del_rcu(&entry->list);
+				spin_unlock_bh(&ar->bar_list_lock[queue]);
+				kfree_rcu(entry, head);
+				goto out;
+			}
+		}
+
+		WARN(1, "bar not found in %d - ra:%pM ta:%pM c:%x ssn:%x\n",
+		       queue, bar->ra, bar->ta, bar->control,
+			bar->start_seq_num);
+out:
+		rcu_read_unlock();
+	}
+}
+
 void carl9170_tx_status(struct ar9170 *ar, struct sk_buff *skb,
 			const bool success)
 {
@@ -445,6 +484,8 @@ void carl9170_tx_status(struct ar9170 *ar, struct sk_buff *skb,
 
 	txinfo = IEEE80211_SKB_CB(skb);
 
+	carl9170_tx_bar_status(ar, skb, txinfo);
+
 	if (success)
 		txinfo->flags |= IEEE80211_TX_STAT_ACK;
 	else
@@ -1265,6 +1306,26 @@ out_rcu:
 	return false;
 }
 
+static void carl9170_bar_check(struct ar9170 *ar, struct sk_buff *skb)
+{
+	struct _carl9170_tx_superframe *super = (void *) skb->data;
+	struct ieee80211_bar *bar = (void *) super->frame_data;
+
+	if (unlikely(ieee80211_is_back_req(bar->frame_control)) &&
+	    skb->len >= sizeof(struct ieee80211_bar)) {
+		struct carl9170_bar_list_entry *entry;
+		unsigned int queue = skb_get_queue_mapping(skb);
+
+		entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
+		if (!WARN_ON_ONCE(!entry)) {
+			entry->skb = skb;
+			spin_lock_bh(&ar->bar_list_lock[queue]);
+			list_add_tail_rcu(&entry->list, &ar->bar_list[queue]);
+			spin_unlock_bh(&ar->bar_list_lock[queue]);
+		}
+	}
+}
+
 static void carl9170_tx(struct ar9170 *ar)
 {
 	struct sk_buff *skb;
@@ -1287,6 +1348,8 @@ static void carl9170_tx(struct ar9170 *ar)
 			if (unlikely(carl9170_tx_ps_drop(ar, skb)))
 				continue;
 
+			carl9170_bar_check(ar, skb);
+
 			atomic_inc(&ar->tx_total_pending);
 
 			q = __carl9170_get_queue(ar, i);