linux-kernel - [PATCH 3.16 264/305] mac80211: fix reordering of buffered broadcast packets

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Message-ID: <lsq.1549201508.615114819@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Johannes Berg" <johannes.berg@...el.com>,
        "Felix Fietkau" <nbd@....name>
Subject: [PATCH 3.16 264/305] mac80211: fix reordering of buffered
 broadcast packets

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Felix Fietkau <nbd@....name>

commit 9ec1190d065998650fd9260dea8cf3e1f56c0e8c upstream.

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).

Signed-off-by: Felix Fietkau <nbd@....name>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/mac80211/tx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -417,8 +417,8 @@ ieee80211_tx_h_multicast_ps_buf(struct i
 	if (tx->local->hw.flags & IEEE80211_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;