mac80211: Avoid filling up mesh preq queue with redundant requests

Don't accept redundant PREQs for a given destination. This fixes a
problem under high load:

kernel: [20386.250913] mesh_queue_preq: 235 callbacks suppressed
kernel: [20386.253335] Mesh HWMP (mesh0): PREQ node queue full
kernel: [20386.253352] Mesh HWMP (mesh0): PREQ node queue full
(...)

The 802.11s protocol has a provision to limit the rate of path requests
(PREQs) are transmitted (dot11MeshHWMPpreqMinInterval) but there was no
limit on the rate at which PREQs were being queued up.  There is a valid
reason for queuing PREQs: this way we can even out PREQ bursts.  But
queueing multiple PREQs for the same destination is useless.

Reported-by: Pedro Larbig <pedro.larbig@carhs.de>
Signed-off-by: Javier Cardona <javier@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index 0f2c4e6..622cc96 100644 (file)
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -31,6 +31,8 @@
  * @MESH_PATH_FIXED: the mesh path has been manually set and should not be
  *     modified
  * @MESH_PATH_RESOLVED: the mesh path can has been resolved
+ * @MESH_PATH_REQ_QUEUED: there is an unsent path request for this destination
+ * already queued up, waiting for the discovery process to start.
  *
  * MESH_PATH_RESOLVED is used by the mesh path timer to
  * decide when to stop or cancel the mesh path discovery.
@@ -41,6 +43,7 @@ enum mesh_path_flags {
        MESH_PATH_SN_VALID =    BIT(2),
        MESH_PATH_FIXED =       BIT(3),
        MESH_PATH_RESOLVED =    BIT(4),
+       MESH_PATH_REQ_QUEUED =  BIT(5),
 };
 
 /**

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 9a1f8bb..b22b223 100644 (file)
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -867,9 +867,19 @@ static void mesh_queue_preq(struct mesh_path *mpath, u8 flags)
                return;
        }
 
+       spin_lock_bh(&mpath->state_lock);
+       if (mpath->flags & MESH_PATH_REQ_QUEUED) {
+               spin_unlock_bh(&mpath->state_lock);
+               spin_unlock_bh(&ifmsh->mesh_preq_queue_lock);
+               return;
+       }
+
        memcpy(preq_node->dst, mpath->dst, ETH_ALEN);
        preq_node->flags = flags;
 
+       mpath->flags |= MESH_PATH_REQ_QUEUED;
+       spin_unlock_bh(&mpath->state_lock);
+
        list_add_tail(&preq_node->list, &ifmsh->preq_queue.list);
        ++ifmsh->preq_queue_len;
        spin_unlock_bh(&ifmsh->mesh_preq_queue_lock);
@@ -921,6 +931,7 @@ void mesh_path_start_discovery(struct ieee80211_sub_if_data *sdata)
                goto enddiscovery;
 
        spin_lock_bh(&mpath->state_lock);
+       mpath->flags &= ~MESH_PATH_REQ_QUEUED;
        if (preq_node->flags & PREQ_Q_F_START) {
                if (mpath->flags & MESH_PATH_RESOLVING) {
                        spin_unlock_bh(&mpath->state_lock);
@@ -1028,8 +1039,7 @@ int mesh_nexthop_lookup(struct sk_buff *skb,
                        mesh_queue_preq(mpath, PREQ_Q_F_START);
                }
 
-               if (skb_queue_len(&mpath->frame_queue) >=
-                               MESH_FRAME_QUEUE_LEN)
+               if (skb_queue_len(&mpath->frame_queue) >= MESH_FRAME_QUEUE_LEN)
                        skb_to_free = skb_dequeue(&mpath->frame_queue);
 
                info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
@@ -1061,6 +1071,7 @@ void mesh_path_timer(unsigned long data)
        } else if (mpath->discovery_retries < max_preq_retries(sdata)) {
                ++mpath->discovery_retries;
                mpath->discovery_timeout *= 2;
+               mpath->flags &= ~MESH_PATH_REQ_QUEUED;
                spin_unlock_bh(&mpath->state_lock);
                mesh_queue_preq(mpath, 0);
        } else {