mac80211: add time synchronisation with BSS for assoc

Some drivers (iwlegacy, iwlwifi and rt2x00) today use the
bss_conf.last_tsf value. By itself though that value is
completely worthless since it may be ancient. What really
is needed is synchronisation between some device time and
the TSF.

To clarify this, rename bss_conf.last_tsf to sync_tsf and
add sync_device_ts which is obtained from rx_status which
gets a new field device_timestamp for this purpose. This
is intentionally not using the mactime field since that
is used for other things and in IBSS is expected to sync
with the IBSS's TSF which isn't necessarily true for the
device timestamp.

Also, since we have the information and it's useful even
before the connection has been established, give all the
timing details to the driver before authenticating.

Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 7300cb51dd5..bb86aa6f98d 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -233,8 +233,10 @@ enum ieee80211_rssi_event {
  *      valid in station mode only while @assoc is true and if also
  *      requested by %IEEE80211_HW_NEED_DTIM_PERIOD (cf. also hw conf
  *      @ps_dtim_period)
- * @last_tsf: last beacon's/probe response's TSF timestamp (could be old
+ * @sync_tsf: last beacon's/probe response's TSF timestamp (could be old
  *      as it may have been received during scanning long ago)
+ * @sync_device_ts: the device timestamp corresponding to the sync_tsf,
+ *      the driver/device can use this to calculate synchronisation
  * @beacon_int: beacon interval
  * @assoc_capability: capabilities taken from assoc resp
  * @basic_rates: bitmap of basic rates, each bit stands for an
@@ -281,7 +283,8 @@ struct ieee80211_bss_conf {
         u8 dtim_period;
         u16 beacon_int;
         u16 assoc_capability;
-        u64 last_tsf;
+        u64 sync_tsf;
+        u32 sync_device_ts;
         u32 basic_rates;
         int mcast_rate[IEEE80211_NUM_BANDS];
         u16 ht_operation_mode;
@@ -696,6 +699,8 @@ enum mac80211_rx_flags {
  *
  * @mactime: value in microseconds of the 64-bit Time Synchronization Function
  *      (TSF) timer when the first data symbol (MPDU) arrived at the hardware.
+ * @device_timestamp: arbitrary timestamp for the device, mac80211 doesn't use
+ *      it but can store it and pass it back to the driver for synchronisation
  * @band: the active band when this frame was received
  * @freq: frequency the radio was tuned to when receiving this frame, in MHz
  * @signal: signal strength when receiving this frame, either in dBm, in dB or
@@ -709,6 +714,7 @@ enum mac80211_rx_flags {
  */
 struct ieee80211_rx_status {
         u64 mactime;
+        u32 device_timestamp;
         u16 flag;
         u16 freq;
         u8 rate_idx;