From 9ec1190d065998650fd9260dea8cf3e1f56c0e8c Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Wed, 28 Nov 2018 22:39:16 +0100
Subject: [PATCH] mac80211: fix reordering of buffered broadcast packets
Git-commit: 9ec1190d065998650fd9260dea8cf3e1f56c0e8c
Patch-mainline: v4.20-rc6
References: FATE#326294, bsc#1051510

If the buffered broadcast queue contains packets, letting new packets bypass
that queue can lead to heavy reordering, since the driver is probably throttling
transmission of buffered multicast packets after beacons.

Keep buffering packets until the buffer has been cleared (and no client
is in powersave mode).

Cc: stable@vger.kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 net/mac80211/tx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index e0ccee23fbcd..1f536ba573b4 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -439,8 +439,8 @@ ieee80211_tx_h_multicast_ps_buf(struct ieee80211_tx_data *tx)
 	if (ieee80211_hw_check(&tx->local->hw, QUEUE_CONTROL))
 		info->hw_queue = tx->sdata->vif.cab_queue;
 
-	/* no stations in PS mode */
-	if (!atomic_read(&ps->num_sta_ps))
+	/* no stations in PS mode and no buffered packets */
+	if (!atomic_read(&ps->num_sta_ps) && skb_queue_empty(&ps->bc_buf))
 		return TX_CONTINUE;
 
 	info->flags |= IEEE80211_TX_CTL_SEND_AFTER_DTIM;
-- 
2.19.2