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>

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/auto/qbluetoothsocket/tst_qbluetoothsocket.cpp b/tests/auto/qbluetoothsocket/tst_qbluetoothsocket.cpp
index 455e31bb..23e291de 100644
--- a/tests/auto/qbluetoothsocket/tst_qbluetoothsocket.cpp
+++ b/tests/auto/qbluetoothsocket/tst_qbluetoothsocket.cpp
@@ -518,7 +518,7 @@ void tst_QBluetoothSocket::tst_preferredSecurityFlags()
 #elif QT_CONFIG(bluez)
     // The bluezdbus socket uses "NoSecurity" by default, whereas the non-dbus bluez
     // socket uses "Authorization" by default
-    if (bluetoothdVersion() >= QVersionNumber(5, 42))
+    if (bluetoothdVersion() >= QVersionNumber(5, 46))
         QCOMPARE(socket.preferredSecurityFlags(), QBluetooth::Security::NoSecurity);
     else
         QCOMPARE(socket.preferredSecurityFlags(), QBluetooth::Security::Authorization);
@@ -569,7 +569,7 @@ void tst_QBluetoothSocket::tst_unsupportedProtocolError()
     QCOMPARE(errorSpy.size(), 1);
 #if QT_CONFIG(bluez)
     // Bluez dbus socket does not support connecting to port and gives different error code
-    if (bluetoothdVersion() >= QVersionNumber(5, 42)) {
+    if (bluetoothdVersion() >= QVersionNumber(5, 46)) {
         QCOMPARE(errorSpy.takeFirst().at(0).toInt(),
                  int(QBluetoothSocket::SocketError::ServiceNotFoundError));
     } else {