mac80211: dont allow fragmentation and requeuing on A-MPDU queues

There really is no reason for a driver to reject a frame on
an A-MPDU queue when it can stop that queue for any period
of time and is given frames one by one. Hence, disallow it
with a big warning and reduce mac80211-internal state.

Also add a warning when we try to fragment a frame destined
for an A-MPDU queue and drop it, the actual bug needs to be
fixed elsewhere but I'm not exactly sure how to yet.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Ron Rindjunsky <ron.rindjunsky@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 26 insertions, 5 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 54960b83db79..4df39eb9115f 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -986,8 +986,10 @@ enum ieee80211_ampdu_mlme_action {
  * @tx: Handler that 802.11 module calls for each transmitted frame.
  *      skb contains the buffer starting from the IEEE 802.11 header.
  *      The low-level driver should send the frame out based on
- *      configuration in the TX control data. Must be implemented and
- *      atomic.
+ *      configuration in the TX control data. This handler should,
+ *      preferably, never fail and stop queues appropriately, more
+ *      importantly, however, it must never fail for A-MPDU-queues.
+ *      Must be implemented and atomic.
  *
  * @start: Called before the first netdevice attached to the hardware
  *      is enabled. This should turn on the hardware and must turn on
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 79a65b3ee02b..86a861251e8c 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -595,7 +595,7 @@ struct ieee80211_local {
         struct timer_list sta_cleanup;
 
         unsigned long state[IEEE80211_MAX_QUEUES + IEEE80211_MAX_AMPDU_QUEUES];
-        struct ieee80211_tx_stored_packet pending_packet[IEEE80211_MAX_QUEUES + IEEE80211_MAX_AMPDU_QUEUES];
+        struct ieee80211_tx_stored_packet pending_packet[IEEE80211_MAX_QUEUES];
         struct tasklet_struct tx_pending_tasklet;
 
         /* number of interfaces with corresponding IFF_ flags */
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index ac9a4af7ad42..6268bbca148e 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -673,6 +673,16 @@ ieee80211_tx_h_fragment(struct ieee80211_tx_data *tx)
         if (!(tx->flags & IEEE80211_TX_FRAGMENTED))
                 return TX_CONTINUE;
 
+        /*
+         * Warn when submitting a fragmented A-MPDU frame and drop it.
+         * This is an error and needs to be fixed elsewhere, but when
+         * done needs to take care of monitor interfaces (injection)
+         * etc.
+         */
+        if (WARN_ON(tx->flags & IEEE80211_TX_CTL_AMPDU ||
+                    IEEE80211_SKB_CB(tx->skb)->queue >= tx->local->hw.queues))
+                return TX_DROP;
+
         first = tx->skb;
 
         hdrlen = ieee80211_get_hdrlen(tx->fc);
@@ -1216,8 +1226,17 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
 retry:
         ret = __ieee80211_tx(local, skb, &tx);
         if (ret) {
-                struct ieee80211_tx_stored_packet *store =
-                        &local->pending_packet[info->queue];
+                struct ieee80211_tx_stored_packet *store;
+
+                /*
+                 * Since there are no fragmented frames on A-MPDU
+                 * queues, there's no reason for a driver to reject
+                 * a frame there, warn and drop it.
+                 */
+                if (WARN_ON(queue >= local->hw.queues))
+                        goto drop;
+
+                store = &local->pending_packet[queue];
 
                 if (ret == IEEE80211_TX_FRAG_AGAIN)
                         skb = NULL;