Close socket descriptor when QBluetoothSocketBluez is destroyed

There are two private QBluetoothSocket backends on Linux:
- QBluetoothSocketBluez is native linux socket implementation
  It is always used by the linux QBluetoothServer, and by
  QBluetoothSocket if Bluez version is < 5.46
- QBluetoothSocketBluezDbus used by QBluetoothSocket when
  Bluez >= 5.46

Leaving the native socket unclosed leaks the resource and eventually
we may run out of descriptors. This is reproducible by creating and
destroying QBluetoothServer instances in a loop.

As a related drive-by:
- Fix bluetooth socket autotest version check. DBus socket is used
  with bluez 5.46+ (for clarity: DBus lowenergycontroller
  is used with bluez 5.42+). This is needed for the test to pass
  with Bluez < 5.46
- Add a clarifying comment on socket close()

Fixes: QTBUG-103067
Pick-to: 5.15 6.2 6.3
Change-Id: Idc38c743be09e559ea82bf09c2f9e44e4b80d666
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

2 files changed, 12 insertions, 1 deletions

diff --git a/src/bluetooth/qbluetoothsocket.cpp b/src/bluetooth/qbluetoothsocket.cpp
index 96901c96..b65f0c56 100644
--- a/src/bluetooth/qbluetoothsocket.cpp
+++ b/src/bluetooth/qbluetoothsocket.cpp
@@ -791,10 +791,15 @@ void QBluetoothSocket::close()
   Set the socket to use \a socketDescriptor with a type of \a socketType,
   which is in state, \a socketState, and mode, \a openMode.
 
+  The set socket descriptor is considered owned by the QBluetoothSocket
+  and may be e.g. closed once finished.
+
   Returns true on success
 */
 
-
+// ### Qt 7 consider making this function private. The qbluetoothsocket_bluez backend is the
+// the only backend providing publicly accessible support for this. Other backends implement
+// similarly named, but private, overload
 bool QBluetoothSocket::setSocketDescriptor(int socketDescriptor, QBluetoothServiceInfo::Protocol socketType,
                                            SocketState socketState, OpenMode openMode)
 {
diff --git a/src/bluetooth/qbluetoothsocket_bluez.cpp b/src/bluetooth/qbluetoothsocket_bluez.cpp
index d6987092..1739d42b 100644
--- a/src/bluetooth/qbluetoothsocket_bluez.cpp
+++ b/src/bluetooth/qbluetoothsocket_bluez.cpp
@@ -72,6 +72,10 @@ QBluetoothSocketPrivateBluez::~QBluetoothSocketPrivateBluez()
     readNotifier = nullptr;
     delete connectWriteNotifier;
     connectWriteNotifier = nullptr;
+
+    // If the socket wasn't closed/aborted make sure we free the socket file descriptor
+    if (socket != -1)
+        QT_CLOSE(socket);
 }
 
 bool QBluetoothSocketPrivateBluez::ensureNativeSocket(QBluetoothServiceInfo::Protocol type)
@@ -618,6 +622,8 @@ qint64 QBluetoothSocketPrivateBluez::readData(char *data, qint64 maxSize)
 
 void QBluetoothSocketPrivateBluez::close()
 {
+    // If we have pending data on the write buffer, wait until it has been written,
+    // after which this close() will be called again
     if (txBuffer.size() > 0)
         connectWriteNotifier->setEnabled(true);
     else