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>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>

diff --git a/include/linux/ieee80211.h b/include/linux/ieee80211.h
index 592b67a1fb288fed8b009c5c6ac9b2b12d7172e1..b7de51388054b523032518203fc1a272ae716ca3 100644 (file)
--- a/include/linux/ieee80211.h
+++ b/include/linux/ieee80211.h
@@ -1468,6 +1468,18 @@ enum ieee80211_tdls_actioncode {
 /* TDLS specific payload type in the LLC/SNAP header */
 #define WLAN_TDLS_SNAP_RFTYPE  0x2
 
+/**
+ * enum - mesh synchronization method identifier
+ *
+ * @IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET: the default synchronization method
+ * @IEEE80211_SYNC_METHOD_VENDOR: a vendor specific synchronization method
+ * that will be specified in a vendor specific information element
+ */
+enum {
+       IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET = 1,
+       IEEE80211_SYNC_METHOD_VENDOR = 255,
+};
+
 /**
  * enum - mesh path selection protocol identifier
  *