[PATCH] mac80211: Send nullfunc frames at lower rate during connection monitor

[Rajkumar Manoharan <rmanohar@qca.qualcomm.com>]

Recently mac80211 was changed to use nullfunc instead of probe
request for connection monitoring for tx ack status reporting
hardwares. Sometimes in congested network, STA got disconnected
quickly after the association. It was observered that the rate
control was not adopted to environment due to minimal transmission.

As the nullfunc are used for monitoring purpose, these frames should
not be sacrificed for rate control updation. So it is better to send
the monitoring null func frames at minimum rate that could help to
retain the connection.

Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
---
 include/net/mac80211.h |    4 ++++
 net/mac80211/mlme.c    |    5 +++++
 net/mac80211/rate.c    |    8 +++++---
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 1e83afa..c7328c1 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -366,6 +366,9 @@ struct ieee80211_bss_conf {
  * @IEEE80211_TX_CTL_NO_CCK_RATE: This frame will be sent at non CCK rate.
  *	This flag is actually used for management frame especially for P2P
  *	frames not being sent at CCK rate in 2GHz band.
+ * @IEEE80211_TX_CTL_USE_MINRATE: This frame will be sent at lowest rate.
+ *	This flag is used to send nullfunc frame at minimum rate when
+ *	the nullfunc is used for connection monitoring purpose.
  *
  * Note: If you have to add new flags to the enumeration, then don't
  *	 forget to update %IEEE80211_TX_TEMPORARY_FLAGS when necessary.
@@ -397,6 +400,7 @@ enum mac80211_tx_control_flags {
 	IEEE80211_TX_CTL_TX_OFFCHAN		= BIT(25),
 	IEEE80211_TX_INTFL_TKIP_MIC_FAILURE	= BIT(26),
 	IEEE80211_TX_CTL_NO_CCK_RATE		= BIT(27),
+	IEEE80211_TX_CTL_USE_MINRATE		= BIT(28),
 };
 
 #define IEEE80211_TX_CTL_STBC_SHIFT		23
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 5282a49..c692f57 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -348,6 +348,7 @@ void ieee80211_send_nullfunc(struct ieee80211_local *local,
 {
 	struct sk_buff *skb;
 	struct ieee80211_hdr_3addr *nullfunc;
+	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
 
 	skb = ieee80211_nullfunc_get(&local->hw, &sdata->vif);
 	if (!skb)
@@ -358,6 +359,10 @@ void ieee80211_send_nullfunc(struct ieee80211_local *local,
 		nullfunc->frame_control |= cpu_to_le16(IEEE80211_FCTL_PM);
 
 	IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;
+	if (ifmgd->flags & (IEEE80211_STA_BEACON_POLL |
+			    IEEE80211_STA_CONNECTION_POLL))
+		IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_CTL_USE_MINRATE;
+
 	ieee80211_tx_skb(sdata, skb);
 }
 
diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index f61244c..ff5c3aa 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -199,7 +199,7 @@ static void rate_control_release(struct kref *kref)
 	kfree(ctrl_ref);
 }
 
-static bool rc_no_data_or_no_ack(struct ieee80211_tx_rate_control *txrc)
+static bool rc_no_data_or_no_ack_use_min(struct ieee80211_tx_rate_control *txrc)
 {
 	struct sk_buff *skb = txrc->skb;
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
@@ -208,7 +208,9 @@ static bool rc_no_data_or_no_ack(struct ieee80211_tx_rate_control *txrc)
 
 	fc = hdr->frame_control;
 
-	return (info->flags & IEEE80211_TX_CTL_NO_ACK) || !ieee80211_is_data(fc);
+	return (info->flags & (IEEE80211_TX_CTL_NO_ACK |
+			       IEEE80211_TX_CTL_USE_MINRATE)) ||
+		!ieee80211_is_data(fc);
 }
 
 static void rc_send_low_broadcast(s8 *idx, u32 basic_rates,
@@ -262,7 +264,7 @@ bool rate_control_send_low(struct ieee80211_sta *sta,
 	struct ieee80211_supported_band *sband = txrc->sband;
 	int mcast_rate;
 
-	if (!sta || !priv_sta || rc_no_data_or_no_ack(txrc)) {
+	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 =
-- 
1.7.6.4