[3.16.y-ckt stable] Patch "mac80211: fix unnecessary frame drops in mesh fwding" has been added to the 3.16.y-ckt tree

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    mac80211: fix unnecessary frame drops in mesh fwding

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt27.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

---8<------------------------------------------------------------

>From 595856d2f238ddf4774b0cef6c3f3e0507e41ded Mon Sep 17 00:00:00 2001
From: Michal Kazior <michal.kazior at tieto.com>
Date: Mon, 25 Jan 2016 14:43:24 +0100
Subject: mac80211: fix unnecessary frame drops in mesh fwding

commit cf44012810ccdd8fd947518e965cb04b7b8498be upstream.

The ieee80211_queue_stopped() expects hw queue
number but it was given raw WMM AC number instead.

This could cause frame drops and problems with
traffic in some cases - most notably if driver
doesn't map AC numbers to queue numbers 1:1 and
uses ieee80211_stop_queues() and
ieee80211_wake_queue() only without ever calling
ieee80211_wake_queues().

On ath10k it was possible to hit this problem in
the following case:

  1. wlan0 uses queue 0
     (ath10k maps queues per vif)
  2. offchannel uses queue 15
  3. queues 1-14 are unused
  4. ieee80211_stop_queues()
  5. ieee80211_wake_queue(q=0)
  6. ieee80211_wake_queue(q=15)
     (other queues are not woken up because both
      driver and mac80211 know other queues are
      unused)
  7. ieee80211_rx_h_mesh_fwding()
  8. ieee80211_select_queue_80211() returns 2
  9. ieee80211_queue_stopped(q=2) returns true
 10. frame is dropped (oops!)

Fixes: d3c1597b8d1b ("mac80211: fix forwarded mesh frame queue mapping")
Signed-off-by: Michal Kazior <michal.kazior at tieto.com>
Signed-off-by: Johannes Berg <johannes.berg at intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/mac80211/rx.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 3ee2abd4007e..94d816b52e56 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2058,7 +2058,7 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
 	struct ieee80211_sub_if_data *sdata = rx->sdata;
 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
-	u16 q, hdrlen;
+	u16 ac, q, hdrlen;

 	hdr = (struct ieee80211_hdr *) skb->data;
 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
@@ -2128,7 +2128,8 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
 	    ether_addr_equal(sdata->vif.addr, hdr->addr3))
 		return RX_CONTINUE;

-	q = ieee80211_select_queue_80211(sdata, skb, hdr);
+	ac = ieee80211_select_queue_80211(sdata, skb, hdr);
+	q = sdata->vif.hw_queue[ac];
 	if (ieee80211_queue_stopped(&local->hw, q)) {
 		IEEE80211_IFSTA_MESH_CTR_INC(ifmsh, dropped_frames_congestion);
 		return RX_DROP_MONITOR;