Commit cf440128 authored Jan 25, 2016 by Michal Kazior Committed by Johannes Berg Feb 24, 2016

mac80211: fix unnecessary frame drops in mesh fwding



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: d3c1597b ("mac80211: fix forwarded mesh frame queue mapping")
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

parent 2a58d42c

net/mac80211/rx.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -2235,7 +2235,7 @@ ieee80211_rx_h_mesh_fwding(struct ieee80211_rx_data *rx)
		struct ieee80211_local *local = rx->local;
		struct ieee80211_sub_if_data *sdata = rx->sdata;
		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);
		@@ -2304,7 +2304,8 @@ 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;

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