QtDBus: finish all pending call with error if disconnected

libdbus will send a local signal if connection gets disconnected. When
this happens, end all pending calls with QDBusError::Disconnected.

Task-number: QTBUG-51649
Change-Id: I5c7d2a468bb5da746d0c0e53e458c1e376f186a9
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/dbus/dbus_minimal_p.h

@@ -99,9 +99,11 @@ typedef dbus_uint32_t  dbus_bool_t;
 /* dbus-shared.h */
 #define DBUS_SERVICE_DBUS      "org.freedesktop.DBus"
 #define DBUS_PATH_DBUS  "/org/freedesktop/DBus"
+#define DBUS_PATH_LOCAL "/org/freedesktop/DBus/Local"
 #define DBUS_INTERFACE_DBUS           "org.freedesktop.DBus"
 #define DBUS_INTERFACE_INTROSPECTABLE "org.freedesktop.DBus.Introspectable"
 #define DBUS_INTERFACE_PROPERTIES     "org.freedesktop.DBus.Properties"
+#define DBUS_INTERFACE_LOCAL "org.freedesktop.DBus.Local"
 
 #define DBUS_NAME_FLAG_ALLOW_REPLACEMENT 0x1 /**< Allow another service to become the primary owner if requested */
 #define DBUS_NAME_FLAG_REPLACE_EXISTING  0x2 /**< Request to replace the current primary owner */

src/dbus/qdbusconnection_p.h

@@ -260,6 +260,8 @@ private:
 
     QString getNameOwnerNoCache(const QString &service);
 
+    void watchForDBusDisconnection();
+
     void _q_newConnection(QDBusConnectionPrivate *newConnection);
 
 protected:
@@ -279,6 +281,7 @@ private slots:
     void serviceOwnerChangedNoLock(const QString &name, const QString &oldOwner, const QString &newOwner);
     void registerServiceNoLock(const QString &serviceName);
     void unregisterServiceNoLock(const QString &serviceName);
+    void handleDBusDisconnection();
 
 signals:
     void dispatchStatusChanged();

src/dbus/qdbusintegrator.cpp

@@ -1121,6 +1121,12 @@ void QDBusConnectionPrivate::closeConnection()
     rootNode.children.clear();  // free resources
 }
 
+void QDBusConnectionPrivate::handleDBusDisconnection()
+{
+    while (!pendingCalls.isEmpty())
+        processFinishedCall(pendingCalls.first());
+}
+
 void QDBusConnectionPrivate::checkThread()
 {
     Q_ASSERT(thread() == QDBusConnectionManager::instance());
@@ -1646,6 +1652,19 @@ void QDBusConnectionPrivate::handleSignal(const QDBusMessage& msg)
     handleSignal(key, msg);                  // third try
 }
 
+void QDBusConnectionPrivate::watchForDBusDisconnection()
+{
+    SignalHook hook;
+    // Initialize the hook for Disconnected signal
+    hook.service.clear(); // org.freedesktop.DBus.Local.Disconnected uses empty service name
+    hook.path = QDBusUtil::dbusPathLocal();
+    hook.obj = this;
+    hook.params << QMetaType::Void;
+    hook.midx = staticMetaObject.indexOfSlot("handleDBusDisconnection()");
+    Q_ASSERT(hook.midx != -1);
+    signalHooks.insert(QLatin1String("Disconnected:" DBUS_INTERFACE_LOCAL), hook);
+}
+
 void QDBusConnectionPrivate::setServer(QDBusServer *object, DBusServer *s, const QDBusErrorInternal &error)
 {
     mode = ServerMode;
@@ -1711,6 +1730,8 @@ void QDBusConnectionPrivate::setPeer(DBusConnection *c, const QDBusErrorInternal
                                qDBusSignalFilter,
                                this, 0);
 
+    watchForDBusDisconnection();
+
     QMetaObject::invokeMethod(this, "doDispatch", Qt::QueuedConnection);
 }
 
@@ -1787,6 +1808,8 @@ void QDBusConnectionPrivate::setConnection(DBusConnection *dbc, const QDBusError
     Q_ASSERT(hook.midx != -1);
     signalHooks.insert(QLatin1String("NameOwnerChanged:" DBUS_INTERFACE_DBUS), hook);
 
+    watchForDBusDisconnection();
+
     qDBusDebug() << this << ": connected successfully";
 
     // schedule a dispatch:
@@ -1813,10 +1836,16 @@ void QDBusConnectionPrivate::processFinishedCall(QDBusPendingCallPrivate *call)
 
     QDBusMessage &msg = call->replyMessage;
     if (call->pending) {
-        // decode the message
-        DBusMessage *reply = q_dbus_pending_call_steal_reply(call->pending);
-        msg = QDBusMessagePrivate::fromDBusMessage(reply, connection->capabilities);
-        q_dbus_message_unref(reply);
+        // when processFinishedCall is called and pending call is not completed,
+        // it means we received disconnected signal from libdbus
+        if (q_dbus_pending_call_get_completed(call->pending)) {
+            // decode the message
+            DBusMessage *reply = q_dbus_pending_call_steal_reply(call->pending);
+            msg = QDBusMessagePrivate::fromDBusMessage(reply, connection->capabilities);
+            q_dbus_message_unref(reply);
+        } else {
+            msg = QDBusMessage::createError(QDBusError::Disconnected, QDBusUtil::disconnectedErrorMessage());
+        }
     }
     qDBusDebug() << connection << "got message reply:" << msg;
 
@@ -2116,8 +2145,8 @@ void QDBusConnectionPrivate::sendInternal(QDBusPendingCallPrivate *pcall, void *
             pcall->pending = pending;
             q_dbus_pending_call_set_notify(pending, qDBusResultReceived, pcall, 0);
 
-            // DBus won't notify us when a peer disconnects so we need to track these ourselves
-            if (mode == QDBusConnectionPrivate::PeerMode)
+            // DBus won't notify us when a peer disconnects or server terminates so we need to track these ourselves
+            if (mode == QDBusConnectionPrivate::PeerMode || mode == QDBusConnectionPrivate::ClientMode)
                 pendingCalls.append(pcall);
 
             return;

src/dbus/qdbusutil_p.h

@@ -155,6 +155,8 @@ namespace QDBusUtil
     { return QStringLiteral(DBUS_SERVICE_DBUS); }
     inline QString dbusPath()
     { return QStringLiteral(DBUS_PATH_DBUS); }
+    inline QString dbusPathLocal()
+    { return QStringLiteral(DBUS_PATH_LOCAL); }
     inline QString dbusInterface()
     {
         // it's the same string, but just be sure

tests/auto/dbus/qdbusconnection/tst_qdbusconnection.cpp

@@ -1218,6 +1218,27 @@ void tst_QDBusConnection::callVirtualObjectLocal()
     QCOMPARE(obj.replyArguments, subPathReply.arguments());
 }
 
+void tst_QDBusConnection::pendingCallWhenDisconnected()
+{
+    if (!QCoreApplication::instance())
+        QSKIP("Test requires a QCoreApplication");
+
+    QDBusServer *server = new QDBusServer;
+    QDBusConnection con = QDBusConnection::connectToPeer(server->address(), "disconnect");
+    QTestEventLoop::instance().enterLoop(2);
+    QVERIFY(con.isConnected());
+    QDBusMessage message = QDBusMessage::createMethodCall("", "/", QString(), "method");
+    QDBusPendingCall reply = con.asyncCall(message);
+
+    delete server;
+
+    QTestEventLoop::instance().enterLoop(2);
+    QVERIFY(!con.isConnected());
+    QVERIFY(reply.isFinished());
+    QVERIFY(reply.isError());
+    QVERIFY(reply.error().type() == QDBusError::Disconnected);
+}
+
 QString MyObject::path;
 QString MyObjectWithoutInterface::path;
 QString MyObjectWithoutInterface::interface;

tests/auto/dbus/qdbusconnection/tst_qdbusconnection.h

@@ -121,6 +121,7 @@ private slots:
     void registerVirtualObject();
     void callVirtualObject();
     void callVirtualObjectLocal();
+    void pendingCallWhenDisconnected();
 
 public:
     QString serviceName() const { return "org.qtproject.Qt.Autotests.QDBusConnection"; }