wifi: mac80211: allow 64-bit radiotap timestamps

When reporting the radiotap timestamp, the mactime field is
usually unused, we take the data from the device_timestamp.
However, there can be cases where the radiotap timestamp is
better reported as a 64-bit value, so since the mactime is
free, add a flag to support using the mactime as a 64-bit
radiotap timestamp.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Gregory Greenman <gregory.greenman@intel.com>
Reviewed-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20231220133549.00c8b9234f0c.Ie3ce5eae33cce88fa01178e7aea94661ded1ac24@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -1367,6 +1367,11 @@ ieee80211_tx_info_clear_status(struct ieee80211_tx_info *info)
  *	(including FCS) was received.
  * @RX_FLAG_MACTIME_PLCP_START: The timestamp passed in the RX status (@mactime
  *	field) is valid and contains the time the SYNC preamble was received.
+ * @RX_FLAG_MACTIME_IS_RTAP_TS64: The timestamp passed in the RX status @mactime
+ *	is only for use in the radiotap timestamp header, not otherwise a valid
+ *	@mactime value. Note this is a separate flag so that we continue to see
+ *	%RX_FLAG_MACTIME as unset. Also note that in this case the timestamp is
+ *	reported to be 64 bits wide, not just 32.
  * @RX_FLAG_NO_SIGNAL_VAL: The signal strength value is not present.
  *	Valid only for data frames (mainly A-MPDU)
  * @RX_FLAG_AMPDU_DETAILS: A-MPDU details are known, in particular the reference
@@ -1442,7 +1447,7 @@ enum mac80211_rx_flags {
 	RX_FLAG_IV_STRIPPED		= BIT(4),
 	RX_FLAG_FAILED_FCS_CRC		= BIT(5),
 	RX_FLAG_FAILED_PLCP_CRC 	= BIT(6),
-	/* one free bit at 7 */
+	RX_FLAG_MACTIME_IS_RTAP_TS64	= BIT(7),
 	RX_FLAG_NO_SIGNAL_VAL		= BIT(8),
 	RX_FLAG_AMPDU_DETAILS		= BIT(9),
 	RX_FLAG_PN_VALIDATED		= BIT(10),

net/mac80211/rx.c

@@ -566,7 +566,8 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
 
 	if (local->hw.radiotap_timestamp.units_pos >= 0) {
 		u16 accuracy = 0;
-		u8 flags = IEEE80211_RADIOTAP_TIMESTAMP_FLAG_32BIT;
+		u8 flags;
+		u64 ts;
 
 		rthdr->it_present |=
 			cpu_to_le32(BIT(IEEE80211_RADIOTAP_TIMESTAMP));
@@ -575,7 +576,15 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local,
 		while ((pos - (u8 *)rthdr) & 7)
 			pos++;
 
-		put_unaligned_le64(status->device_timestamp, pos);
+		if (status->flag & RX_FLAG_MACTIME_IS_RTAP_TS64) {
+			flags = IEEE80211_RADIOTAP_TIMESTAMP_FLAG_64BIT;
+			ts = status->mactime;
+		} else {
+			flags = IEEE80211_RADIOTAP_TIMESTAMP_FLAG_32BIT;
+			ts = status->device_timestamp;
+		}
+
+		put_unaligned_le64(ts, pos);
 		pos += sizeof(u64);
 
 		if (local->hw.radiotap_timestamp.accuracy >= 0) {