Create extra sockets only just before the Wayland compositor is created

Otherwise there will be a window where the socket already exists in file
system, but is not adopted by the compositor yet, leading to "connection
refused" errors should a client try to connect.

Change-Id: Ic96c51c7e8175ab5e9ac40fc70b5f8dc97c11b71
Reviewed-by: Dominik Holland <dominik.holland@qt.io>
(cherry picked from commit 9429d8e84649a4c0a262c16a2eaf394dcc90c79b)

3 files changed, 83 insertions, 52 deletions

diff --git a/src/main-lib/main.cpp b/src/main-lib/main.cpp
index d1d3d11e..03d56747 100644
--- a/src/main-lib/main.cpp
+++ b/src/main-lib/main.cpp
@@ -702,66 +702,82 @@ void Main::setupWindowManager(const QString &waylandSocketName, const QVariantLi
     m_windowManager->enableWatchdog(!uiWatchdog);
 
 #if defined(QT_WAYLANDCOMPOSITOR_LIB)
-    for (const auto &v : waylandExtraSockets) {
-        const QVariantMap &wes = v.toMap();
+    connect(&m_windowManager->internalSignals, &WindowManagerInternalSignals::compositorAboutToBeCreated,
+            this, [this, waylandExtraSockets] {
+        // This needs to be delayed until directly before creating the Wayland compositor.
+        // Otherwise we have a "dangling" socket you cannot connect to.
 
-        const QString path = wes.value(qSL("path")).toString();
+        for (const auto &v : waylandExtraSockets) {
+            const QVariantMap &wes = v.toMap();
 
-        if (path.isEmpty())
-            continue;
-        QFileInfo fi(path);
-        if (!fi.dir().mkpath(qSL(".")))
-            throw Exception("could not create path to extra Wayland socket: %1").arg(path);
+            const QString path = wes.value(qSL("path")).toString();
 
-        auto sudo = SudoClient::instance();
+            if (path.isEmpty())
+                continue;
 
-        if (!sudo || sudo->isFallbackImplementation())
-            QLocalServer::removeServer(path); // if it fails, we'll notice in listen() right away
-        else
-            sudo->removeRecursive(path);
+            try {
+                QFileInfo fi(path);
+                if (!fi.dir().mkpath(qSL(".")))
+                    throw Exception("could not create path to extra Wayland socket: %1").arg(path);
 
-        QScopedPointer<QLocalServer> extraSocket(new QLocalServer);
-        extraSocket->setMaxPendingConnections(0); // disable Qt's new connection handling
-        if (!extraSocket->listen(path)) {
-            throw Exception("could not listen on extra Wayland socket %1: %2")
-                .arg(path, extraSocket->errorString());
-        }
-        int mode = wes.value(qSL("permissions"), -1).toInt();
-        int uid = wes.value(qSL("userId"), -1).toInt();
-        int gid = wes.value(qSL("groupId"), -1).toInt();
-
-        QByteArray encodedPath = QFile::encodeName(path);
-
-        if ((mode > 0) || (uid != -1) || (gid != -1)) {
-            if (!sudo || sudo->isFallbackImplementation()) {
-                if (mode > 0) {
-                    if (::chmod(encodedPath, static_cast<mode_t>(mode)) != 0)
-                        throw Exception(errno, "could not chmod(mode: %1) the extra Wayland socket %2")
-                            .arg(QString::number(mode, 8), path);
+                auto sudo = SudoClient::instance();
+
+                if (!sudo || sudo->isFallbackImplementation()) {
+                    if (!QLocalServer::removeServer(path)) {
+                        throw Exception("could not clean up leftover extra Wayland socket %1").arg(path);
+                    }
+                } else {
+                    sudo->removeRecursive(path);
                 }
-                if ((uid != -1) || (gid != -1)) {
-                    if (::chown(encodedPath, static_cast<uid_t>(uid), static_cast<gid_t>(gid)) != 0)
-                        throw Exception(errno, "could not chown(uid: %1, gid: %2) the extra Wayland socket %3")
-                            .arg(uid).arg(gid).arg(path);
+
+                QScopedPointer<QLocalServer> extraSocket(new QLocalServer);
+                extraSocket->setMaxPendingConnections(0); // disable Qt's new connection handling
+                if (!extraSocket->listen(path)) {
+                    throw Exception("could not listen on extra Wayland socket %1: %2")
+                        .arg(path, extraSocket->errorString());
                 }
-            } else {
-                if (!sudo->setOwnerAndPermissionsRecursive(path, static_cast<uid_t>(uid),
-                                                           static_cast<gid_t>(gid),
-                                                           static_cast<mode_t>(mode))) {
-                    throw Exception(Error::IO, "could not change the owner to %1:%2 and the permission"
-                                               " bits to %3 for the extra Wayland socket %4: %5")
-                            .arg(uid).arg(gid).arg(mode, 0, 8).arg(path).arg(sudo->lastError());
+                int mode = wes.value(qSL("permissions"), -1).toInt();
+                int uid = wes.value(qSL("userId"), -1).toInt();
+                int gid = wes.value(qSL("groupId"), -1).toInt();
+
+                QByteArray encodedPath = QFile::encodeName(path);
+
+                if ((mode > 0) || (uid != -1) || (gid != -1)) {
+                    if (!sudo || sudo->isFallbackImplementation()) {
+                        if (mode > 0) {
+                            if (::chmod(encodedPath, static_cast<mode_t>(mode)) != 0)
+                                throw Exception(errno, "could not chmod(mode: %1) the extra Wayland socket %2")
+                                    .arg(QString::number(mode, 8), path);
+                        }
+                        if ((uid != -1) || (gid != -1)) {
+                            if (::chown(encodedPath, static_cast<uid_t>(uid), static_cast<gid_t>(gid)) != 0)
+                                throw Exception(errno, "could not chown(uid: %1, gid: %2) the extra Wayland socket %3")
+                                    .arg(uid).arg(gid).arg(path);
+                        }
+                    } else {
+                        if (!sudo->setOwnerAndPermissionsRecursive(path, static_cast<uid_t>(uid),
+                                                                   static_cast<gid_t>(gid),
+                                                                   static_cast<mode_t>(mode))) {
+                            throw Exception(Error::IO, "could not change the owner to %1:%2 and the permission"
+                                                       " bits to %3 for the extra Wayland socket %4: %5")
+                                    .arg(uid).arg(gid).arg(mode, 0, 8).arg(path).arg(sudo->lastError());
+                        }
+                        // if we changed the owner, ~QLocalServer might not be able to clean up the
+                        // socket inode, so we need to sudo this removal as well
+                        QObject::connect(extraSocket.data(), &QObject::destroyed, [path, sudo]() {
+                            sudo->removeRecursive(path);
+                        });
+                    }
                 }
-                // if we changed the owner, ~QLocalServer might not be able to clean up the
-                // socket inode, so we need to sudo this removal as well
-                QObject::connect(extraSocket.data(), &QObject::destroyed, [path, sudo]() {
-                    sudo->removeRecursive(path);
-                });
+
+                m_windowManager->addWaylandSocket(extraSocket.take());
+            } catch (const std::exception &e) {
+                qCCritical(LogSystem) << "ERROR:" << e.what();
             }
         }
-
-        m_windowManager->addWaylandSocket(extraSocket.take());
-    }
+    });
+#else
+    Q_UNUSED(waylandExtraSockets)
 #endif
 
     QObject::connect(&m_applicationManager->internalSignals, &ApplicationManagerInternalSignals::newRuntimeCreated,
diff --git a/src/window-lib/windowmanager.cpp b/src/window-lib/windowmanager.cpp
index 69201f01..d237f295 100644
--- a/src/window-lib/windowmanager.cpp
+++ b/src/window-lib/windowmanager.cpp
@@ -687,6 +687,9 @@ void WindowManager::registerCompositorView(QQuickWindow *view)
 #if defined(AM_MULTI_PROCESS)
     if (!ApplicationManager::instance()->isSingleProcess()) {
         if (!d->waylandCompositor) {
+            // this will trigger the creation of extra sockets in main.cpp
+            emit internalSignals.compositorAboutToBeCreated();
+
             d->waylandCompositor = new WaylandCompositor(view, d->waylandSocketName);
             for (const auto &extraSocket : d->extraWaylandSockets)
                 d->waylandCompositor->addSocketDescriptor(extraSocket);
diff --git a/src/window-lib/windowmanager.h b/src/window-lib/windowmanager.h
index 466275fd..8b7fc3dc 100644
--- a/src/window-lib/windowmanager.h
+++ b/src/window-lib/windowmanager.h
@@ -68,6 +68,17 @@ class Application;
 class AbstractRuntime;
 class WaylandCompositor;
 
+
+// A place to collect signals used internally by appman without polluting
+// WindowManager's public QML API.
+class WindowManagerInternalSignals : public QObject
+{
+    Q_OBJECT
+signals:
+    // Emitted right before the WaylandCompositor instance is created
+    void compositorAboutToBeCreated();
+};
+
 class WindowManager : public QAbstractListModel
 {
     Q_OBJECT
@@ -106,6 +117,9 @@ public:
     Q_INVOKABLE int indexOfWindow(Window *window) const;
     Q_INVOKABLE QObject *addExtension(QQmlComponent *component) const;
 
+    WindowManagerInternalSignals internalSignals;
+
+protected:
     bool eventFilter(QObject *watched, QEvent *event) override;
 
 signals:
@@ -124,8 +138,6 @@ signals:
 
     void slowAnimationsChanged(bool);
 
-    void _inProcessSurfaceItemReleased(QSharedPointer<InProcessSurfaceItem>);
-
 private slots:
     void inProcessSurfaceItemCreated(QSharedPointer<InProcessSurfaceItem> surfaceItem);
     void setupWindow(QT_PREPEND_NAMESPACE_AM(Window) *window);