[PATCHv2] mac80211: Copy tx'ed beacons to monitor mode

[Helmut Schaa <helmut.schaa@googlemail.com>]

When debugging wireless powersave issues on the AP side it's quite helpful
to see our own beacons that are transmitted by the hardware/driver. However,
this is not that easy since beacons don't pass through the regular TX queues.

Preferably drivers would call ieee80211_tx_status also for tx'ed beacons
but that's not always possible. Hence, just send a copy of each beacon
generated by ieee80211_beacon_get_tim to monitor devices when they are
getting fetched by the driver.

Also add a HW flag IEEE80211_HW_BEACON_TX_STATUS that can be used by
drivers to indicate that they report TX status for beacons.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
---

Changes since RFC:
* don't send beacons to cooked monitors
* avoid assignment within if condition
* Introduce IEEE80211_HW_BEACON_TX_STATUS

Changes since v1:
* Invert logic to get shorter lines (<80 chars)

 include/net/mac80211.h |  4 ++++
 net/mac80211/debugfs.c |  1 +
 net/mac80211/tx.c      | 16 ++++++++++++++++
 3 files changed, 21 insertions(+)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index e3314e5..b136ac5 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1892,6 +1892,9 @@ struct ieee80211_txq {
  * @IEEE80211_HW_TDLS_WIDER_BW: The device/driver supports wider bandwidth
  *	than then BSS bandwidth for a TDLS link on the base channel.
  *
+ * @IEEE80211_HW_BEACON_TX_STATUS: The device/driver provides TX status
+ *	for sent beacons.
+ *
  * @NUM_IEEE80211_HW_FLAGS: number of hardware flags, used for sizing arrays
  */
 enum ieee80211_hw_flags {
@@ -1925,6 +1928,7 @@ enum ieee80211_hw_flags {
 	IEEE80211_HW_SUPPORTS_CLONED_SKBS,
 	IEEE80211_HW_SINGLE_SCAN_ON_ALL_BANDS,
 	IEEE80211_HW_TDLS_WIDER_BW,
+	IEEE80211_HW_BEACON_TX_STATUS,
 
 	/* keep last, obviously */
 	NUM_IEEE80211_HW_FLAGS
diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index ced6bf3..d55f5ba 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -123,6 +123,7 @@ static const char *hw_flag_names[NUM_IEEE80211_HW_FLAGS + 1] = {
 	FLAG(SUPPORTS_CLONED_SKBS),
 	FLAG(SINGLE_SCAN_ON_ALL_BANDS),
 	FLAG(TDLS_WIDER_BW),
+	FLAG(BEACON_TX_STATUS),
 
 	/* keep last for the build bug below */
 	(void *)0x1
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 84e0e8c..e482f3e 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3512,6 +3512,9 @@ struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
 {
 	struct ieee80211_mutable_offsets offs = {};
 	struct sk_buff *bcn = __ieee80211_beacon_get(hw, vif, &offs, false);
+	struct sk_buff *copy;
+	struct ieee80211_supported_band *sband;
+	int shift;
 
 	if (tim_offset)
 		*tim_offset = offs.tim_offset;
@@ -3519,6 +3522,19 @@ struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
 	if (tim_length)
 		*tim_length = offs.tim_length;
 
+	if (ieee80211_hw_check(hw, BEACON_TX_STATUS) ||
+	    !hw_to_local(hw)->monitors)
+		return bcn;
+
+	/* send a copy to monitor interfaces */
+	copy = skb_copy(bcn, GFP_ATOMIC);
+	if (!copy)
+		return bcn;
+
+	shift = ieee80211_vif_get_shift(vif);
+	sband = hw->wiphy->bands[ieee80211_get_sdata_band(vif_to_sdata(vif))];
+	ieee80211_tx_monitor(hw_to_local(hw), copy, sband, 1, shift, false);
+
 	return bcn;
 }
 EXPORT_SYMBOL(ieee80211_beacon_get_tim);
-- 
1.8.4.5