wayland: Set up initialization X11 socket

This is used by GDK and the X11 bits, but may also be used for
other initialization services we might need to run along with
Xwayland initialization.

However, as the -initfd argument in Xwayland is a fairly new
feature, add some meson build-time checks so that the feature
is handled transparently while allowing to explicitly set/unset
it.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/945

config.h.meson

@@ -67,3 +67,6 @@
 /* Either <sys/random.h> or <linux/random.h> */
 #mesondefine HAVE_SYS_RANDOM
 #mesondefine HAVE_LINUX_RANDOM
+
+/* Whether Xwayland has -initfd option */
+#mesondefine HAVE_XWAYLAND_INITFD

meson.build

@@ -377,6 +377,7 @@ if cc.has_header_symbol('sys/prctl.h', 'prctl')
   cdata.set('HAVE_SYS_PRCTL', 1)
 endif
 
+have_xwayland_initfd = false
 if have_wayland
   xwayland_path = get_option('xwayland_path')
   if xwayland_path == ''
@@ -392,6 +393,19 @@ if have_wayland
   else
     error('Required function getrandom not found')
   endif
+
+  # For Xwayland -initfd usage
+  use_initfd = get_option('xwayland_initfd')
+  if use_initfd.auto()
+    xwayland_options = run_command(xwayland_path, '-help')
+    have_xwayland_initfd = xwayland_options.stderr().contains('-initfd')
+  else
+    have_xwayland_initfd = use_initfd.enabled()
+  endif
+
+  if (have_xwayland_initfd)
+    cdata.set('HAVE_XWAYLAND_INITFD', 1)
+  endif
 endif
 
 xwayland_grab_default_access_rules = get_option('xwayland_grab_default_access_rules')
@@ -450,6 +464,7 @@ output = [
   '        Startup notification..... ' + have_startup_notification.to_string(),
   '        Introspection............ ' + have_introspection.to_string(),
   '        Profiler................. ' + have_profiler.to_string(),
+  '        Xwayland initfd.......... ' + have_xwayland_initfd.to_string(),
   '',
   '    Tests:',
   '',

meson_options.txt

@@ -152,3 +152,9 @@ option('xwayland_grab_default_access_rules',
   value: 'gnome-boxes,remote-viewer,virt-viewer,virt-manager,vinagre,vncviewer,Xephyr',
   description: 'Comma delimited list of applications ressources or class allowed to issue X11 grabs in Xwayland'
 )
+
+option('xwayland_initfd',
+  type: 'feature',
+  value: 'auto',
+  description: 'Whether Xwayland -initfd argument is used'
+)

src/wayland/meta-wayland-private.h

@@ -48,11 +48,18 @@ typedef struct
   char *lock_file;
   int abstract_fd;
   int unix_fd;
+  char *name;
+} MetaXWaylandConnection;
+
+typedef struct
+{
+  MetaXWaylandConnection private_connection;
+  MetaXWaylandConnection public_connection;
+
   guint xserver_grace_period_id;
   struct wl_display *wayland_display;
   struct wl_client *client;
   struct wl_resource *xserver_resource;
-  char *display_name;
   char *auth_file;
 
   GCancellable *xserver_died_cancellable;

src/wayland/meta-wayland.c

@@ -446,7 +446,7 @@ meta_wayland_init (void)
 
   if (meta_get_x11_display_policy () != META_DISPLAY_POLICY_DISABLED)
     {
-      set_gnome_env ("DISPLAY", meta_wayland_get_xwayland_display_name (compositor));
+      set_gnome_env ("DISPLAY", compositor->xwayland_manager.public_connection.name);
       set_gnome_env ("XAUTHORITY", meta_wayland_get_xwayland_auth_file (compositor));
     }
 
@@ -462,7 +462,7 @@ meta_wayland_get_wayland_display_name (MetaWaylandCompositor *compositor)
 const char *
 meta_wayland_get_xwayland_display_name (MetaWaylandCompositor *compositor)
 {
-  return compositor->xwayland_manager.display_name;
+  return compositor->xwayland_manager.private_connection.name;
 }
 
 void

src/wayland/meta-xwayland.c

@@ -314,6 +314,7 @@ xserver_died (GObject      *source,
               gpointer      user_data)
 {
   GSubprocess *proc = G_SUBPROCESS (source);
+  MetaDisplay *display = meta_get_display ();
   g_autoptr (GError) error = NULL;
 
   if (!g_subprocess_wait_finish (proc, result, &error))
@@ -338,7 +339,6 @@ xserver_died (GObject      *source,
   else if (meta_get_x11_display_policy () == META_DISPLAY_POLICY_ON_DEMAND)
     {
       MetaWaylandCompositor *compositor = meta_wayland_compositor_get_default ();
-      MetaDisplay *display = meta_get_display ();
 
       if (display->x11_display)
         meta_display_shutdown_x11 (display);
@@ -381,6 +381,8 @@ meta_xwayland_override_display_number (int number)
 static gboolean
 open_display_sockets (MetaXWaylandManager *manager,
                       int                  display_index,
+                      int                 *abstract_fd_out,
+                      int                 *unix_fd_out,
                       gboolean            *fatal)
 {
   int abstract_fd, unix_fd;
@@ -398,14 +400,15 @@ open_display_sockets (MetaXWaylandManager *manager,
       return FALSE;
     }
 
-  manager->abstract_fd = abstract_fd;
+  *abstract_fd_out = abstract_fd;
-  manager->unix_fd = unix_fd;
+  *unix_fd_out = unix_fd;
 
   return TRUE;
 }
 
 static gboolean
-choose_xdisplay (MetaXWaylandManager *manager)
+choose_xdisplay (MetaXWaylandManager    *manager,
+                 MetaXWaylandConnection *connection)
 {
   int display = 0;
   char *lock_file = NULL;
@@ -425,7 +428,10 @@ choose_xdisplay (MetaXWaylandManager *manager)
           return FALSE;
         }
 
-      if (!open_display_sockets (manager, display, &fatal))
+      if (!open_display_sockets (manager, display,
+                                 &connection->abstract_fd,
+                                 &connection->unix_fd,
+                                 &fatal))
         {
           unlink (lock_file);
 
@@ -445,9 +451,9 @@ choose_xdisplay (MetaXWaylandManager *manager)
     }
   while (1);
 
-  manager->display_index = display;
+  connection->display_index = display;
-  manager->display_name = g_strdup_printf (":%d", manager->display_index);
+  connection->name = g_strdup_printf (":%d", connection->display_index);
-  manager->lock_file = lock_file;
+  connection->lock_file = lock_file;
 
   return TRUE;
 }
@@ -611,14 +617,16 @@ meta_xwayland_start_xserver (MetaXWaylandManager *manager,
   launcher = g_subprocess_launcher_new (flags);
 
   g_subprocess_launcher_take_fd (launcher, xwayland_client_fd[1], 3);
-  g_subprocess_launcher_take_fd (launcher, manager->abstract_fd, 4);
+  g_subprocess_launcher_take_fd (launcher, manager->public_connection.abstract_fd, 4);
-  g_subprocess_launcher_take_fd (launcher, manager->unix_fd, 5);
+  g_subprocess_launcher_take_fd (launcher, manager->public_connection.unix_fd, 5);
   g_subprocess_launcher_take_fd (launcher, displayfd[1], 6);
+  g_subprocess_launcher_take_fd (launcher, manager->private_connection.abstract_fd, 7);
 
   g_subprocess_launcher_setenv (launcher, "WAYLAND_SOCKET", "3", TRUE);
 
   manager->proc = g_subprocess_launcher_spawn (launcher, &error,
-                                               XWAYLAND_PATH, manager->display_name,
+                                               XWAYLAND_PATH,
+                                               manager->public_connection.name,
                                                "-rootless",
                                                "-noreset",
                                                "-accessx",
@@ -627,7 +635,13 @@ meta_xwayland_start_xserver (MetaXWaylandManager *manager,
                                                "-listen", "4",
                                                "-listen", "5",
                                                "-displayfd", "6",
+#ifdef HAVE_XWAYLAND_INITFD
+                                               "-initfd", "7",
+#else
+                                               "-listen", "7",
+#endif
                                                NULL);
+
   if (!manager->proc)
     {
       g_task_return_error (task, error);
@@ -728,9 +742,11 @@ meta_xwayland_init (MetaXWaylandManager *manager,
   MetaDisplayPolicy policy;
   gboolean fatal;
 
-  if (!manager->display_name)
+  if (!manager->public_connection.name)
     {
-      if (!choose_xdisplay (manager))
+      if (!choose_xdisplay (manager, &manager->public_connection))
+        return FALSE;
+      if (!choose_xdisplay (manager, &manager->private_connection))
         return FALSE;
 
       if (!prepare_auth_file (manager))
@@ -738,7 +754,18 @@ meta_xwayland_init (MetaXWaylandManager *manager,
     }
   else
     {
-      if (!open_display_sockets (manager, manager->display_index, &fatal))
+      if (!open_display_sockets (manager,
+                                 manager->public_connection.display_index,
+                                 &manager->public_connection.abstract_fd,
+                                 &manager->public_connection.unix_fd,
+                                 &fatal))
+        return FALSE;
+
+      if (!open_display_sockets (manager,
+                                 manager->private_connection.display_index,
+                                 &manager->private_connection.abstract_fd,
+                                 &manager->private_connection.unix_fd,
+                                 &fatal))
         return FALSE;
     }
 
@@ -747,7 +774,7 @@ meta_xwayland_init (MetaXWaylandManager *manager,
 
   if (policy == META_DISPLAY_POLICY_ON_DEMAND)
     {
-      g_unix_fd_add (manager->abstract_fd, G_IO_IN,
+      g_unix_fd_add (manager->public_connection.abstract_fd, G_IO_IN,
                      xdisplay_connection_activity_cb, manager);
     }
 
@@ -793,6 +820,13 @@ meta_xwayland_complete_init (MetaDisplay *display,
     }
 }
 
+static void
+meta_xwayland_connection_release (MetaXWaylandConnection *connection)
+{
+  unlink (connection->lock_file);
+  g_clear_pointer (&connection->lock_file, g_free);
+}
+
 void
 meta_xwayland_shutdown (MetaXWaylandManager *manager)
 {
@@ -800,18 +834,21 @@ meta_xwayland_shutdown (MetaXWaylandManager *manager)
 
   g_cancellable_cancel (manager->xserver_died_cancellable);
 
-  snprintf (path, sizeof path, "/tmp/.X11-unix/X%d", manager->display_index);
+  snprintf (path, sizeof path, "/tmp/.X11-unix/X%d", manager->public_connection.display_index);
   unlink (path);
 
-  g_clear_pointer (&manager->display_name, g_free);
+  snprintf (path, sizeof path, "/tmp/.X11-unix/X%d", manager->private_connection.display_index);
+  unlink (path);
+
+  g_clear_pointer (&manager->public_connection.name, g_free);
+  g_clear_pointer (&manager->private_connection.name, g_free);
+
+  meta_xwayland_connection_release (&manager->public_connection);
+  meta_xwayland_connection_release (&manager->private_connection);
+
   if (manager->auth_file)
     {
       unlink (manager->auth_file);
       g_clear_pointer (&manager->auth_file, g_free);
     }
-  if (manager->lock_file)
-    {
-      unlink (manager->lock_file);
-      g_clear_pointer (&manager->lock_file, g_free);
-    }
 }