mac80211: implement packet loss notification

For drivers that have accurate TX status reporting
we can report the number of consecutive lost packets
to userspace using the new cfg80211 CQM event. The
threshold is fixed right now, this may need to be
improved in the future.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/net/mac80211/status.c b/net/mac80211/status.c
index 8695cd1..bed7e32 100644
--- a/net/mac80211/status.c
+++ b/net/mac80211/status.c
@@ -161,6 +161,15 @@ static void ieee80211_frame_acked(struct sta_info *sta, struct sk_buff *skb)
 		ieee80211_sta_tx_notify(sdata, (void *) skb->data);
 }
 
+/*
+ * Use a static threshold for now, best value to be determined
+ * by testing ...
+ * Should it depend on:
+ *  - on # of retransmissions
+ *  - current throughput (higher value for higher tpt)?
+ */
+#define STA_LOST_PKT_THRESHOLD	50
+
 void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
 {
 	struct sk_buff *skb2;
@@ -247,6 +256,19 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
 		if (!(info->flags & IEEE80211_TX_CTL_INJECTED) &&
 		    (info->flags & IEEE80211_TX_STAT_ACK))
 			ieee80211_frame_acked(sta, skb);
+
+		if (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) {
+			if (info->flags & IEEE80211_TX_STAT_ACK) {
+				if (sta->lost_packets)
+					sta->lost_packets = 0;
+			} else if (++sta->lost_packets >= STA_LOST_PKT_THRESHOLD) {
+				cfg80211_cqm_pktloss_notify(sta->sdata->dev,
+							    sta->sta.addr,
+							    sta->lost_packets,
+							    GFP_ATOMIC);
+				sta->lost_packets = 0;
+			}
+		}
 	}
 
 	rcu_read_unlock();