mac80211: Implement mesh synchronization framework

This patch adds MBSS extensible synchronization framework (Sec.
13.13.2 of IEEE Std. 802.11-2012).

The framework is implemented via an ops table which defines the
following functions:

    rx_bcn_presp() - this is called every time a mesh beacon is
received.
    adjust_tbtt() - this is called immediately before a beacon is about
to be transmitted.

The default neighbor offset synchronization defined in the standard is
implemented.  We also provide template functions for vendor specific
methods.

When neighbor offset synchronization is active (which is the default)
mesh neighbors in the same MBSS will track timing offsets to each other
and compensate clock drift.

In our tests we observed that this mesh synchronization implementation
successfully corrected drifts between stations of ~2PPM while
introducing a jitter of ~20us.

It is also possible to test this framework on mac80211_hwsim simulated
phys to see how it behaves under different topologies, over poor links,
etc.

Signed-off-by: Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
Signed-off-by: Pavel Zubarev <pavel.zubarev@gmail.com>
Signed-off-by: Javier Cardona <javier@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index 3e52439ed112..fa7d9704c175 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -19,6 +19,20 @@
 /* Data structures */
 
 /**
+ * enum mesh_config_capab_flags - mesh config IE capability flags
+ *
+ * @MESHCONF_CAPAB_ACCEPT_PLINKS: STA is willing to establish
+ * additional mesh peerings with other mesh STAs
+ * @MESHCONF_CAPAB_FORWARDING: the STA forwards MSDUs
+ * @MESHCONF_CAPAB_TBTT_ADJUSTING: TBTT adjustment procedure is ongoing
+ */
+enum mesh_config_capab_flags {
+        MESHCONF_CAPAB_ACCEPT_PLINKS = BIT(0),
+        MESHCONF_CAPAB_FORWARDING = BIT(3),
+        MESHCONF_CAPAB_TBTT_ADJUSTING = BIT(5),
+};
+
+/**
  * enum mesh_path_flags - mac80211 mesh path flags
  *
  *
@@ -56,12 +70,15 @@ enum mesh_path_flags {
  * @MESH_WORK_GROW_MPP_TABLE: the mesh portals table is full and needs to
  * grow
  * @MESH_WORK_ROOT: the mesh root station needs to send a frame
+ * @MESH_WORK_DRIFT_ADJUST: time to compensate for clock drift relative to other
+ * mesh nodes
  */
 enum mesh_deferred_task_flags {
         MESH_WORK_HOUSEKEEPING,
         MESH_WORK_GROW_MPATH_TABLE,
         MESH_WORK_GROW_MPP_TABLE,
         MESH_WORK_ROOT,
+        MESH_WORK_DRIFT_ADJUST,
 };
 
 /**
@@ -234,6 +251,7 @@ void ieee80211_mesh_init_sdata(struct ieee80211_sub_if_data *sdata);
 void ieee80211_start_mesh(struct ieee80211_sub_if_data *sdata);
 void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata);
 void ieee80211_mesh_root_setup(struct ieee80211_if_mesh *ifmsh);
+struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method);
 
 /* Mesh paths */
 int mesh_nexthop_lookup(struct sk_buff *skb,
@@ -327,6 +345,7 @@ void ieee80211_mesh_quiesce(struct ieee80211_sub_if_data *sdata);
 void ieee80211_mesh_restart(struct ieee80211_sub_if_data *sdata);
 void mesh_plink_quiesce(struct sta_info *sta);
 void mesh_plink_restart(struct sta_info *sta);
+void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata);
 #else
 #define mesh_allocated  0
 static inline void