Windows BT: reverse the latter UUID part to correct order

The Windows IDataReader::ReadGuid function, which is used to read long
128 bit UUIDs from the SDP results, gives the last 8 bytes of the UUID
in reverse order. This commit reverses the byte order.

Without the correct byte order the UUIDs of the services are
reported wrong, and for example the uuidFilter does not work reliably.

The original bug was that the "pingpong" Windows client never finds a
Linux pingpong server. It turned out that it finds it, but interprets
the UUID wrong. The same interpretation error can also be seen against
an Android server. Running the pingpong client against an Android server
however works for the reason below.

This issue has gone undetected so far because the serviceID field is
read differently using different interface and method, and as a
consequence has made the uuid filters to work against some platforms.

Fixes: QTBUG-99689
Change-Id: I71ab44264579f9eb46461ed8fdd7a49dbf402531
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
(cherry picked from commit 0dd124498e91308eb7ac16e976049b431770f7ef)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/bluetooth/qbluetoothservicediscoveryagent_winrt.cpp b/src/bluetooth/qbluetoothservicediscoveryagent_winrt.cpp
index 5ca3382a..170673d3 100644
--- a/src/bluetooth/qbluetoothservicediscoveryagent_winrt.cpp
+++ b/src/bluetooth/qbluetoothservicediscoveryagent_winrt.cpp
@@ -82,6 +82,13 @@ Q_DECLARE_LOGGING_CATEGORY(QT_BT_WINRT)
 #define TYPE_STRING 37
 #define TYPE_SEQUENCE 53
 
+// Helper to reverse given uchar array
+static void reverseArray(uchar data[], size_t length)
+{
+    for (size_t i = length; i > length/2; i--)
+        std::swap(data[length - i], data[i - 1]);
+}
+
 class QWinRTBluetoothServiceDiscoveryWorker : public QObject
 {
     Q_OBJECT
@@ -308,6 +315,8 @@ void QWinRTBluetoothServiceDiscoveryWorker::processServiceSearchResult(quint64 a
                 GUID value;
                 hr = dataReader->ReadGuid(&value);
                 Q_ASSERT_SUCCEEDED(hr);
+                // The latter 8 bytes are in reverse order
+                reverseArray(value.Data4, sizeof(value.Data4)/sizeof(value.Data4[0]));
                 const QBluetoothUuid uuid(value);
                 info.setAttribute(key, uuid);
                 qCDebug(QT_BT_WINRT) << "UUID" << uuid << "KEY" << hex << key << "TYPE" << dec << type << "UUID" << hex << uuid;
@@ -421,7 +430,8 @@ QBluetoothServiceInfo::Sequence QWinRTBluetoothServiceDiscoveryWorker::readSeque
             GUID b;
             hr = dataReader->ReadGuid(&b);
             Q_ASSERT_SUCCEEDED(hr);
-
+            // The latter 8 bytes are in reverse order
+            reverseArray(b.Data4, sizeof(b.Data4)/sizeof(b.Data4[0]));
             const QBluetoothUuid uuid(b);
             result.append(QVariant::fromValue(uuid));
             remainingLength -= sizeof(GUID);