[PATCH 0/4] Mesh sync fixes

[PATCH 0/4] Mesh sync fixes

[Javier Cardona]

We noticed these while testing mesh synchronization.

Javier Cardona (4):
  mac80211: Set the correct values for hwmp (1) and airtimeLinkMetric
    (1)
  mac80211_hwsim: fixup for tsf setting
  mac80211: Choose a new toffset setpoint if a big tsf jump is
    detected.
  mac80211: Take into account TSF adjustment latency in Toffset
    setpoint

 drivers/net/wireless/mac80211_hwsim.c |    1 +
 include/linux/ieee80211.h             |    4 ++--
 net/mac80211/mesh_sync.c              |   32 ++++++++++++++++++++++++++------
 3 files changed, 29 insertions(+), 8 deletions(-)

-- 
1.7.5.4

[PATCH 1/4] mac80211: Set the correct values for hwmp (1) and airtimeLinkMetric (1)

[Javier Cardona]

Per sections 8.4.2.100.2 and 8.4.2.100.3 of Std 802.11-2012

Reported-by: Shinichi Hotori <hotorinn@gmail.com>
Signed-off-by: Javier Cardona <javier@cozybit.com>
---
 include/linux/ieee80211.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/ieee80211.h b/include/linux/ieee80211.h
index db84e2f..ce9af89 100644
--- a/include/linux/ieee80211.h
+++ b/include/linux/ieee80211.h
@@ -1458,7 +1458,7 @@ enum {
  * be specified in a vendor specific information element
  */
 enum {
-	IEEE80211_PATH_PROTOCOL_HWMP = 0,
+	IEEE80211_PATH_PROTOCOL_HWMP = 1,
 	IEEE80211_PATH_PROTOCOL_VENDOR = 255,
 };
 
@@ -1470,7 +1470,7 @@ enum {
  * specified in a vendor specific information element
  */
 enum {
-	IEEE80211_PATH_METRIC_AIRTIME = 0,
+	IEEE80211_PATH_METRIC_AIRTIME = 1,
 	IEEE80211_PATH_METRIC_VENDOR = 255,
 };
 
-- 
1.7.5.4

[PATCH 2/4] mac80211_hwsim: fixup for tsf setting

[Javier Cardona]

Last patch I sent failed to take into account the offset of each phy.

Signed-off-by: Javier Cardona <javier@cozybit.com>
---
 drivers/net/wireless/mac80211_hwsim.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 2d2bfce..3edd473 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -694,6 +694,7 @@ static bool mac80211_hwsim_tx_frame_no_nl(struct ieee80211_hw *hw,
 		    ieee80211_is_probe_resp(mgmt->frame_control))
 			mgmt->u.beacon.timestamp = cpu_to_le64(
 				rx_status.mactime +
+				(data->tsf_offset - data2->tsf_offset) +
 				24 * 8 * 10 / txrate->bitrate);
 
 		memcpy(IEEE80211_SKB_RXCB(nskb), &rx_status, sizeof(rx_status));
-- 
1.7.5.4

[PATCH 3/4] mac80211: Choose a new toffset setpoint if a big tsf jump is detected.

[Javier Cardona]

Signed-off-by: Javier Cardona <javier@cozybit.com>
---
 net/mac80211/mesh_sync.c |   26 ++++++++++++++++++++------
 1 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/net/mac80211/mesh_sync.c b/net/mac80211/mesh_sync.c
index f78b013..22a5f1e 100644
--- a/net/mac80211/mesh_sync.c
+++ b/net/mac80211/mesh_sync.c
@@ -22,7 +22,14 @@
 /* This is not in the standard.  It represents a tolerable tbtt drift below
  * which we do no TSF adjustment.
  */
-#define TBTT_MINIMUM_ADJUSTMENT 10
+#define TOFFSET_MINIMUM_ADJUSTMENT 10
+
+/* This is not in the standard.  It represents the maximum Toffset jump above
+ * which we'll invalidate the Toffset setpoint and choose a new setpoint.  This
+ * could be, for instance, in case a neighbor is restarted and its TSF counter
+ * reset.
+ * */
+#define TOFFSET_MAXIMUM_ADJUSTMENT 30000		/* 30 ms */
 
 struct sync_method {
 	u8 method;
@@ -156,15 +163,22 @@ static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 	if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 		s64 t_clockdrift = sta->t_offset_setpoint
 				   - sta->t_offset;
-
-		msync_dbg("STA %pM : sta->t_offset=%lld,"
-			  " sta->t_offset_setpoint=%lld,"
-			  " t_clockdrift=%lld",
+		msync_dbg("STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld",
 			  sta->sta.addr,
 			  (long long) sta->t_offset,
 			  (long long)
 			  sta->t_offset_setpoint,
 			  (long long) t_clockdrift);
+
+		if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
+			t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
+			msync_dbg("STA %pM : t_clockdrift=%lld too large, setpoint reset",
+				  sta->sta.addr,
+				  (long long) t_clockdrift);
+			clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
+			goto no_sync;
+		}
+
 		rcu_read_unlock();
 
 		spin_lock_bh(&ifmsh->sync_offset_lock);
@@ -200,7 +214,7 @@ static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 	spin_lock_bh(&ifmsh->sync_offset_lock);
 
 	if (ifmsh->sync_offset_clockdrift_max >
-		TBTT_MINIMUM_ADJUSTMENT) {
+		TOFFSET_MINIMUM_ADJUSTMENT) {
 		/* Since ajusting the tsf here would
 		 * require a possibly blocking call
 		 * to the driver tsf setter, we punt
-- 
1.7.5.4

[PATCH 4/4] mac80211: Take into account TSF adjustment latency in Toffset setpoint

[Javier Cardona]

When testing mesh synchronization we observed a global TSF slowdown that
was dependent on the number of synchronized mesh stations.  This seems
to be caused by the TSF adjustment (read/write) latency.

Adding a small margin to the Toffset setpoint solved the problem.

Signed-off-by: Shinichi Hotori <hotorinn@gmail.com>
Signed-off-by: Yu Niiro <yu.niiro@gmail.com>
Signed-off-by: Javier Cardona <javier@cozybit.com>
---
 net/mac80211/mesh_sync.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/net/mac80211/mesh_sync.c b/net/mac80211/mesh_sync.c
index 22a5f1e..ff60d6b 100644
--- a/net/mac80211/mesh_sync.c
+++ b/net/mac80211/mesh_sync.c
@@ -24,11 +24,17 @@
  */
 #define TOFFSET_MINIMUM_ADJUSTMENT 10
 
+/* This is not in the standard. It is a margin added to the
+ * Toffset setpoint to mitigate TSF overcorrection
+ * introduced by TSF adjustment latency.
+ */
+#define TOFFSET_SET_MARGIN 20
+
 /* This is not in the standard.  It represents the maximum Toffset jump above
  * which we'll invalidate the Toffset setpoint and choose a new setpoint.  This
  * could be, for instance, in case a neighbor is restarted and its TSF counter
  * reset.
- * */
+ */
 #define TOFFSET_MAXIMUM_ADJUSTMENT 30000		/* 30 ms */
 
 struct sync_method {
-- 
1.7.5.4

Re: [PATCH 0/4] Mesh sync fixes

[Johannes Berg]

On Thu, 2012-04-12 at 14:32 -0700, Javier Cardona wrote:
> We noticed these while testing mesh synchronization.

I think these patches were merged, but there seems to have been some
confusion about what changes belong into what patch -- please try to be
more careful about that.

Also -- no users for TOFFSET_SET_MARGIN?

johannes