From: Felix Fietkau nbd@nbd.name
[ Upstream commit dedf2ec30fe417d181490896adf89cd6b9885b23 ]
When running in AP mode and deauthenticating a client that's in powersave mode, the disassoc/deauth packet can get stuck in a tx queue along with other buffered frames. This can fill up hardware queues with frames that are only released after the WTBL slot is reused for another client.
Fix this by moving deauth packets to the ALTX queue.
Reported-by: Chad Monroe chad.monroe@adtran.com Link: https://patch.msgid.link/20250707154702.1726-2-nbd@nbd.name Signed-off-by: Felix Fietkau nbd@nbd.name Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
Now I understand the issue and the fix better. Let me analyze this commit:
**YES**
This commit should be backported to stable kernel trees for the following reasons:
1. **It fixes a real bug affecting users**: The commit addresses a specific issue where deauthentication packets sent to clients in powersave mode can get stuck in hardware TX queues. This causes queue exhaustion and prevents the WTBL (Wireless Table) slot from being properly reused for new clients. This is a significant functional bug that impacts AP mode operation.
2. **The fix is small and contained**: The change is minimal - it only adds a single condition (`|| ieee80211_is_deauth(hdr->frame_control)`) to the existing queue assignment logic. This is a low-risk change that doesn't introduce new functionality or architectural changes.
3. **Clear problem and solution**: The commit message clearly describes the issue (deauth packets getting stuck with other buffered frames) and the solution (moving deauth packets to the ALTX/PSD queue). The fix is logical because: - According to `ieee80211_is_bufferable_mmpdu()` (line 4517), deauth frames ARE considered bufferable MMPDUs - However, when a client is being deauthenticated, we don't want these frames to be buffered with regular data - they need immediate transmission - The PSD (Power Save Delivery) queue is more appropriate for management frames that need immediate handling
4. **Similar to previous backported fixes**: Looking at the similar commits, commit #1 (fca9615f1a43) which fixed queue handling for loopback packets was backported. This current fix addresses a similar class of queue assignment issues.
5. **No architectural changes**: The fix uses existing infrastructure (MT_TXQ_PSD queue) and existing helper functions (ieee80211_is_deauth). It doesn't introduce new features or change any APIs.
6. **Prevents resource exhaustion**: The bug can lead to hardware queue exhaustion which is a serious issue in production AP deployments. This makes it an important fix for stable kernels.
The code change shows that previously, only non-bufferable MMPDUs were assigned to the PSD queue, but deauth frames (which are technically bufferable) were getting stuck in regular data queues when sent to powersave clients. This fix ensures deauth frames bypass the normal buffering mechanism and get transmitted promptly via the PSD queue.
drivers/net/wireless/mediatek/mt76/tx.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/net/wireless/mediatek/mt76/tx.c b/drivers/net/wireless/mediatek/mt76/tx.c index 065a1e4537457..da31bf3c18db8 100644 --- a/drivers/net/wireless/mediatek/mt76/tx.c +++ b/drivers/net/wireless/mediatek/mt76/tx.c @@ -615,7 +615,8 @@ mt76_txq_schedule_pending_wcid(struct mt76_phy *phy, struct mt76_wcid *wcid, if ((dev->drv->drv_flags & MT_DRV_HW_MGMT_TXQ) && !(info->flags & IEEE80211_TX_CTL_HW_80211_ENCAP) && !ieee80211_is_data(hdr->frame_control) && - !ieee80211_is_bufferable_mmpdu(skb)) + (!ieee80211_is_bufferable_mmpdu(skb) || + ieee80211_is_deauth(hdr->frame_control))) qid = MT_TXQ_PSD;
q = phy->q_tx[qid];