mac80211: update adjusting TBTT bit in beacon

This regression was introduced in "mac80211: cache mesh
beacon".

mesh_sync_offset_adjust_tbtt()  was assuming that the
beacon would be rebuilt in every single pre-tbtt
interrupt, but now the beacon update happens on the
workqueue, and it must be ready for immediate delivery to
the driver.

Save a pointer to the meshconf IE in the beacon_data (this
works because both the IE pointer and beacon buffer are
protected by the same rcu_{dereference,assign_pointer}())
for quick updates during pre-tbtt. This is faster and a
little prettier than iterating over the elements to find
the meshconf IE every time.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

4 files changed, 22 insertions, 4 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index ee13c6593b9a..adbff719638c 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -232,6 +232,7 @@ struct ieee80211_rx_data {
 struct beacon_data {
         u8 *head, *tail;
         int head_len, tail_len;
+        struct ieee80211_meshconf_ie *meshconf;
         struct rcu_head rcu_head;
 };
 
@@ -540,7 +541,10 @@ struct ieee80211_mesh_sync_ops {
                              struct ieee80211_mgmt *mgmt,
                              struct ieee802_11_elems *elems,
                              struct ieee80211_rx_status *rx_status);
-        void (*adjust_tbtt)(struct ieee80211_sub_if_data *sdata);
+
+        /* should be called with beacon_data under RCU read lock */
+        void (*adjust_tbtt)(struct ieee80211_sub_if_data *sdata,
+                            struct beacon_data *beacon);
         /* add other framework functions here */
 };
 
@@ -614,6 +618,9 @@ struct ieee80211_if_mesh {
         bool chsw_init;
         u8 chsw_ttl;
         u16 pre_value;
+
+        /* offset from skb->data while building IE */
+        int meshconf_offset;
 };
 
 #ifdef CONFIG_MAC80211_MESH
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 89df62b2b689..5a74b249ba35 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -259,6 +259,9 @@ int mesh_add_meshconf_ie(struct ieee80211_sub_if_data *sdata,
         *pos++ = WLAN_EID_MESH_CONFIG;
         *pos++ = meshconf_len;
 
+        /* save a pointer for quick updates in pre-tbtt */
+        ifmsh->meshconf_offset = pos - skb->data;
+
         /* Active path selection protocol ID */
         *pos++ = ifmsh->mesh_pp_id;
         /* Active path selection metric ID   */
@@ -723,6 +726,8 @@ ieee80211_mesh_build_beacon(struct ieee80211_if_mesh *ifmsh)
 
         bcn->tail_len = skb->len;
         memcpy(bcn->tail, skb->data, bcn->tail_len);
+        bcn->meshconf = (struct ieee80211_meshconf_ie *)
+                                        (bcn->tail + ifmsh->meshconf_offset);
 
         dev_kfree_skb(skb);
         rcu_assign_pointer(ifmsh->beacon, bcn);
diff --git a/net/mac80211/mesh_sync.c b/net/mac80211/mesh_sync.c
index d1cf2d553499..2bc5dc25d5ad 100644
--- a/net/mac80211/mesh_sync.c
+++ b/net/mac80211/mesh_sync.c
@@ -164,12 +164,15 @@ no_sync:
         rcu_read_unlock();
 }
 
-static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
+static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata,
+                                         struct beacon_data *beacon)
 {
         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+        u8 cap;
 
         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
         BUG_ON(!rcu_read_lock_held());
+        cap = beacon->meshconf->meshconf_cap;
 
         spin_lock_bh(&ifmsh->sync_offset_lock);
 
@@ -194,6 +197,10 @@ static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
                 ifmsh->adjusting_tbtt = false;
         }
         spin_unlock_bh(&ifmsh->sync_offset_lock);
+
+        beacon->meshconf->meshconf_cap = ifmsh->adjusting_tbtt ?
+                        IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING | cap :
+                        ~IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING & cap;
 }
 
 static const struct sync_method sync_methods[] = {
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 002ded2c01f6..2f0e176e7989 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2604,8 +2604,7 @@ struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
                         ieee80211_update_csa(sdata, bcn);
 
                 if (ifmsh->sync_ops)
-                        ifmsh->sync_ops->adjust_tbtt(
-                                                sdata);
+                        ifmsh->sync_ops->adjust_tbtt(sdata, bcn);
 
                 skb = dev_alloc_skb(local->tx_headroom +
                                     bcn->head_len +