all: distinguish between public and random addresses

This is necessary when connecting to a device when using the SoftDevice.
The information is not set on Linux and Windows and is ignored on those
platform when connecting.

adapter_nrf528xx.go

@@ -71,7 +71,8 @@ func handleEvent() {
 			// callback.
 			scanReportBuffer.len = byte(advReport.data.len)
 			globalScanResult.RSSI = int16(advReport.rssi)
-			globalScanResult.Address = advReport.peer_addr.addr
+			globalScanResult.Address.MAC = advReport.peer_addr.addr
+			globalScanResult.Address.IsRandom = advReport.peer_addr.bitfield_addr_type() != 0
 			globalScanResult.AdvertisementPayload = &scanReportBuffer
 			// Signal to the main thread that there was a scan report.
 			// Scanning will be resumed (from the main thread) once the scan

gap.go

@@ -38,11 +38,29 @@ func NewAdvertisementInterval(intervalMillis uint32) AdvertisementInterval {
 // Connection is a numeric identifier that indicates a connection handle.
 type Connection uint16
 
+// Address contains a Bluetooth address, which is a MAC address plus some extra
+// information.
+type Address struct {
+	// The MAC address of a Bluetooth device.
+	MAC
+
+	// Is this address a random address?
+	// Bluetooth addresses are roughly split in two kinds: public
+	// (IEEE-assigned) addresses and random (not IEEE assigned) addresses.
+	// "Random" here doesn't mean it is exactly random but at least it looks
+	// random. Sometimes, it contains a hash.
+	// For more information:
+	// https://www.novelbits.io/bluetooth-address-privacy-ble/
+	//
+	// This field is unused under Windows and Linux.
+	IsRandom bool
+}
+
 // ScanResult contains information from when an advertisement packet was
 // received. It is passed as a parameter to the callback of the Scan method.
 type ScanResult struct {
-	// MAC address of the scanned device.
+	// Bluetooth address of the scanned device.
-	Address MAC
+	Address Address
 
 	// RSSI the last time a packet from this device has been received.
 	RSSI int16

gap_linux.go

@@ -156,7 +156,7 @@ func makeScanResult(dev *device.Device1) ScanResult {
 
 	return ScanResult{
 		RSSI:    dev.Properties.RSSI,
-		Address: addr,
+		Address: Address{addr, false}, // the 'IsRandom' bit is not supported
 		AdvertisementPayload: &advertisementFields{
 			AdvertisementFields{
 				LocalName: dev.Properties.Name,

gap_windows.go

@@ -24,10 +24,11 @@ func (a *Adapter) Scan(callback func(*Adapter, ScanResult)) (err error) {
 		var result ScanResult
 		result.RSSI = args.RawSignalStrengthInDBm()
 		addr := args.BluetoothAddress()
-		for i := range result.Address {
+		for i := range result.Address.MAC {
-			result.Address[i] = byte(addr)
+			result.Address.MAC[i] = byte(addr)
 			addr >>= 8
 		}
+		// Note: the IsRandom bit is never set.
 		advertisement := args.Advertisement()
 		result.AdvertisementPayload = &advertisementFields{
 			AdvertisementFields{