[PATCH] wifi: mac80211: reinstate IEEE80211_TX_CTL_AMPDU flag in ieee80211_tx_prep_agg()

["Toke Høiland-Jørgensen" <toke@toke.dk>]

The commit 592234e941f1 ("wifi: mac80211: Fix iTXQ AMPDU fragmentation
handling") changed the way handling of the IEEE80211_TX_CTL_AMPDU flag
is done in mac80211, so the only place it is set is in
ieee80211_tx_dequeue().

This means that any frames that are sent to the driver via drv_tx() will
no longer have the flag set. In particular, this affects packets going
through ieee80211_tx_pending(). Evan reported that this can result in
the ath9k driver failing to account such packets in its block ack
window, eventually overrunning the window and stalling TX.

Fix this by reinstating the flag in ieee80211_tx_prep_agg() when inside
a valid block ack window. This should be harmless for the TXQ path, and
will reinstate the previous behaviour for drivers that use the flag as a
signal to track the packet in the window.

Fixes: 592234e941f1 ("wifi: mac80211: Fix iTXQ AMPDU fragmentation handling")
Cc: stable@vger.kernel.org
Reported-by: Evan Severson <eseverson@gmail.com>
Link: https://lore.kernel.org/all/20261014025734.2288693-1-eseverson@gmail.com/
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
---
 net/mac80211/tx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index e9b6a0415d6a..0f46b5ff0c4a 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1164,6 +1164,7 @@ static bool ieee80211_tx_prep_agg(struct ieee80211_tx_data *tx,
 	struct sk_buff *purge_skb = NULL;
 
 	if (test_bit(HT_AGG_STATE_OPERATIONAL, &tid_tx->state)) {
+		info->flags |= IEEE80211_TX_CTL_AMPDU;
 		reset_agg_timer = true;
 	} else if (test_bit(HT_AGG_STATE_WANT_START, &tid_tx->state)) {
 		/*
@@ -1195,6 +1196,7 @@ static bool ieee80211_tx_prep_agg(struct ieee80211_tx_data *tx,
 		if (!tid_tx) {
 			/* do nothing, let packet pass through */
 		} else if (test_bit(HT_AGG_STATE_OPERATIONAL, &tid_tx->state)) {
+			info->flags |= IEEE80211_TX_CTL_AMPDU;
 			reset_agg_timer = true;
 		} else {
 			queued = true;
-- 
2.56.0