mac80211: fix timing for 5 MHz and 10 MHz channels

according to IEEE 802.11-2012 section 18, various timings change
when using 5 MHz and 10 MHz. Reflect this by using a "shift" when
calculating durations.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

1 files changed, 26 insertions, 13 deletions

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 22654452a561..61856e17a1e4 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -107,7 +107,8 @@ void ieee80211_tx_set_protected(struct ieee80211_tx_data *tx)
 }
 
 int ieee80211_frame_duration(enum ieee80211_band band, size_t len,
-			     int rate, int erp, int short_preamble)
+			     int rate, int erp, int short_preamble,
+			     int shift)
 {
 	int dur;
 
@@ -118,6 +119,9 @@ int ieee80211_frame_duration(enum ieee80211_band band, size_t len,
 	 *
 	 * rate is in 100 kbps, so divident is multiplied by 10 in the
 	 * DIV_ROUND_UP() operations.
+	 *
+	 * shift may be 2 for 5 MHz channels or 1 for 10 MHz channels, and
+	 * is assumed to be 0 otherwise.
 	 */
 
 	if (band == IEEE80211_BAND_5GHZ || erp) {
@@ -130,15 +134,21 @@ int ieee80211_frame_duration(enum ieee80211_band band, size_t len,
 		 * TXTIME = T_PREAMBLE + T_SIGNAL + T_SYM x N_SYM + Signal Ext
 		 *
 		 * T_SYM = 4 usec
-		 * 802.11a - 17.5.2: aSIFSTime = 16 usec
+		 * 802.11a - 18.5.2: aSIFSTime = 16 usec
 		 * 802.11g - 19.8.4: aSIFSTime = 10 usec +
 		 *	signal ext = 6 usec
 		 */
 		dur = 16; /* SIFS + signal ext */
-		dur += 16; /* 17.3.2.3: T_PREAMBLE = 16 usec */
-		dur += 4; /* 17.3.2.3: T_SIGNAL = 4 usec */
+		dur += 16; /* IEEE 802.11-2012 18.3.2.4: T_PREAMBLE = 16 usec */
+		dur += 4; /* IEEE 802.11-2012 18.3.2.4: T_SIGNAL = 4 usec */
 		dur += 4 * DIV_ROUND_UP((16 + 8 * (len + 4) + 6) * 10,
 					4 * rate); /* T_SYM x N_SYM */
+
+		/* IEEE 802.11-2012 18.3.2.4: all values above are:
+		 *  * times 4 for 5 MHz
+		 *  * times 2 for 10 MHz
+		 */
+		dur *= 1 << shift;
 	} else {
 		/*
 		 * 802.11b or 802.11g with 802.11b compatibility:
@@ -168,7 +178,7 @@ __le16 ieee80211_generic_frame_duration(struct ieee80211_hw *hw,
 {
 	struct ieee80211_sub_if_data *sdata;
 	u16 dur;
-	int erp;
+	int erp, shift = 0;
 	bool short_preamble = false;
 
 	erp = 0;
@@ -177,10 +187,11 @@ __le16 ieee80211_generic_frame_duration(struct ieee80211_hw *hw,
 		short_preamble = sdata->vif.bss_conf.use_short_preamble;
 		if (sdata->flags & IEEE80211_SDATA_OPERATING_GMODE)
 			erp = rate->flags & IEEE80211_RATE_ERP_G;
+		shift = ieee80211_vif_get_shift(vif);
 	}
 
 	dur = ieee80211_frame_duration(band, frame_len, rate->bitrate, erp,
-				       short_preamble);
+				       short_preamble, shift);
 
 	return cpu_to_le16(dur);
 }
@@ -194,7 +205,7 @@ __le16 ieee80211_rts_duration(struct ieee80211_hw *hw,
 	struct ieee80211_rate *rate;
 	struct ieee80211_sub_if_data *sdata;
 	bool short_preamble;
-	int erp;
+	int erp, shift = 0;
 	u16 dur;
 	struct ieee80211_supported_band *sband;
 
@@ -210,17 +221,18 @@ __le16 ieee80211_rts_duration(struct ieee80211_hw *hw,
 		short_preamble = sdata->vif.bss_conf.use_short_preamble;
 		if (sdata->flags & IEEE80211_SDATA_OPERATING_GMODE)
 			erp = rate->flags & IEEE80211_RATE_ERP_G;
+		shift = ieee80211_vif_get_shift(vif);
 	}
 
 	/* CTS duration */
 	dur = ieee80211_frame_duration(sband->band, 10, rate->bitrate,
-				       erp, short_preamble);
+				       erp, short_preamble, shift);
 	/* Data frame duration */
 	dur += ieee80211_frame_duration(sband->band, frame_len, rate->bitrate,
-					erp, short_preamble);
+					erp, short_preamble, shift);
 	/* ACK duration */
 	dur += ieee80211_frame_duration(sband->band, 10, rate->bitrate,
-					erp, short_preamble);
+					erp, short_preamble, shift);
 
 	return cpu_to_le16(dur);
 }
@@ -235,7 +247,7 @@ __le16 ieee80211_ctstoself_duration(struct ieee80211_hw *hw,
 	struct ieee80211_rate *rate;
 	struct ieee80211_sub_if_data *sdata;
 	bool short_preamble;
-	int erp;
+	int erp, shift = 0;
 	u16 dur;
 	struct ieee80211_supported_band *sband;
 
@@ -250,15 +262,16 @@ __le16 ieee80211_ctstoself_duration(struct ieee80211_hw *hw,
 		short_preamble = sdata->vif.bss_conf.use_short_preamble;
 		if (sdata->flags & IEEE80211_SDATA_OPERATING_GMODE)
 			erp = rate->flags & IEEE80211_RATE_ERP_G;
+		shift = ieee80211_vif_get_shift(vif);
 	}
 
 	/* Data frame duration */
 	dur = ieee80211_frame_duration(sband->band, frame_len, rate->bitrate,
-				       erp, short_preamble);
+				       erp, short_preamble, shift);
 	if (!(frame_txctl->flags & IEEE80211_TX_CTL_NO_ACK)) {
 		/* ACK duration */
 		dur += ieee80211_frame_duration(sband->band, 10, rate->bitrate,
-						erp, short_preamble);
+						erp, short_preamble, shift);
 	}
 
 	return cpu_to_le16(dur);