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From 09e012860a6e1e074ac1950a4afc3d4131d046d9 Mon Sep 17 00:00:00 2001
From: Tom Gundersen <teg@jklm.no>
Date: Thu, 1 Mar 2018 12:00:09 +0100
Subject: [PATCH] bus-launch: add dbus-broker support

If dbus-broker is enabled at compile-time and found at run-time prefer that
over dbus-daemon.

Unlike with dbus-daemon, this means that at-spi-bus-launch must create the
listening socket and pass it in, rather than having the bus do that and send
back the address. For now we follow what dbus-daemon does, and create a socket
in the abstract namespace, though it might be more suitable to create a socket
in $XDG_RUNTIME_DIR.

The only difference users should observe is that daemons are no longer spawned
by the bus implementation, but spawned and managed by the systemd user instance,
though this should not lead to a difference in behavior. In particular this
applies to `org.a11y.atspi.Registry`.

For non-linux and non-systemd systems, dbus-daemon should continue to be used.

Signed-off-by: Tom Gundersen <teg@jklm.no>
---
 bus/at-spi-bus-launcher.c | 145 ++++++++++++++++++++++++++++++++++++++--------
 bus/meson.build           |  27 +++++++--
 meson_options.txt         |   4 ++
 3 files changed, 147 insertions(+), 29 deletions(-)

diff --git a/bus/at-spi-bus-launcher.c b/bus/at-spi-bus-launcher.c
index eb2b8e3..8aeb490 100644
--- a/bus/at-spi-bus-launcher.c
+++ b/bus/at-spi-bus-launcher.c
@@ -2,7 +2,7 @@
  * 
  * at-spi-bus-launcher: Manage the a11y bus as a child process 
  *
- * Copyright 2011 Red Hat, Inc.
+ * Copyright 2011-2018 Red Hat, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -25,6 +25,11 @@
 #include <unistd.h>
 #include <string.h>
 #include <signal.h>
+#ifdef __linux
+#include <sys/prctl.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#endif
 #include <sys/wait.h>
 #include <errno.h>
 #include <stdio.h>
@@ -58,6 +63,7 @@ typedef struct {
   int a11y_bus_pid;
   char *a11y_bus_address;
   int pipefd[2];
+  int listenfd;
   char *a11y_launch_error_message;
 } A11yBusLauncher;
 
@@ -216,7 +222,7 @@ name_appeared_handler (GDBusConnection *connection,
 }
 
 static void
-setup_bus_child (gpointer data)
+setup_bus_child_daemon (gpointer data)
 {
   A11yBusLauncher *app = data;
   (void) app;
@@ -227,7 +233,6 @@ setup_bus_child (gpointer data)
 
   /* On Linux, tell the bus process to exit if this process goes away */
 #ifdef __linux
-#include <sys/prctl.h>
   prctl (PR_SET_PDEATHSIG, 15);
 #endif  
 }
@@ -277,23 +282,12 @@ on_bus_exited (GPid     pid,
 } 
 
 static gboolean
-ensure_a11y_bus (A11yBusLauncher *app)
+ensure_a11y_bus_daemon (A11yBusLauncher *app, char *config_path)
 {
+  char *argv[] = { DBUS_DAEMON, config_path, "--nofork", "--print-address", "3", NULL };
   GPid pid;
-  char *argv[] = { DBUS_DAEMON, NULL, "--nofork", "--print-address", "3", NULL };
   char addr_buf[2048];
   GError *error = NULL;
-  const char *config_path = NULL;
-
-  if (app->a11y_bus_pid != 0)
-    return FALSE;
-
-  if (g_file_test (SYSCONFDIR"/at-spi2/accessibility.conf", G_FILE_TEST_EXISTS))
-      config_path = "--config-file="SYSCONFDIR"/at-spi2/accessibility.conf";
-  else
-      config_path = "--config-file="DATADIR"/defaults/at-spi2/accessibility.conf";
-
-  argv[1] = config_path;
 
   if (pipe (app->pipefd) < 0)
     g_error ("Failed to create pipe: %s", strerror (errno));
@@ -302,7 +296,7 @@ ensure_a11y_bus (A11yBusLauncher *app)
                       argv,
                       NULL,
                       G_SPAWN_SEARCH_PATH | G_SPAWN_DO_NOT_REAP_CHILD,
-                      setup_bus_child,
+                      setup_bus_child_daemon,
                       app,
                       &pid,
                       &error))
@@ -335,6 +329,116 @@ ensure_a11y_bus (A11yBusLauncher *app)
   app->a11y_bus_address = g_strchomp (g_strdup (addr_buf));
   g_debug ("a11y bus address: %s", app->a11y_bus_address);
 
+  return TRUE;
+
+error:
+  close (app->pipefd[0]);
+  close (app->pipefd[1]);
+  app->state = A11Y_BUS_STATE_ERROR;
+
+  return FALSE;
+}
+
+#ifdef DBUS_BROKER
+static void
+setup_bus_child_broker (gpointer data)
+{
+  A11yBusLauncher *app = data;
+  gchar *pid_str;
+  (void) app;
+
+  dup2 (app->listenfd, 3);
+  close (app->listenfd);
+  g_setenv("LISTEN_FDS", "1", TRUE);
+
+  pid_str = g_strdup_printf("%u", getpid());
+  g_setenv("LISTEN_PID", pid_str, TRUE);
+  g_free(pid_str);
+
+  /* Tell the bus process to exit if this process goes away */
+  prctl (PR_SET_PDEATHSIG, SIGTERM);
+}
+
+static gboolean
+ensure_a11y_bus_broker (A11yBusLauncher *app, char *config_path)
+{
+  char *argv[] = { DBUS_BROKER, config_path, "--scope", "user", "--verbose", NULL };
+  struct sockaddr_un addr = { .sun_family = AF_UNIX };
+  socklen_t addr_len = sizeof(addr);
+  GPid pid;
+  GError *error = NULL;
+
+  if ((app->listenfd = socket (PF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0)) < 0)
+    g_error ("Failed to create listening socket: %s", strerror (errno));
+
+  if (bind (app->listenfd, (struct sockaddr *)&addr, sizeof(sa_family_t)) < 0)
+    g_error ("Failed to bind listening socket: %s", strerror (errno));
+
+  if (getsockname (app->listenfd, (struct sockaddr *)&addr, &addr_len) < 0)
+    g_error ("Failed to get socket name for listening socket: %s", strerror(errno));
+
+  if (listen (app->listenfd, 1024) < 0)
+    g_error ("Failed to listen on socket: %s", strerror(errno));
+
+  if (!g_spawn_async (NULL,
+                      argv,
+                      NULL,
+                      G_SPAWN_SEARCH_PATH | G_SPAWN_DO_NOT_REAP_CHILD,
+                      setup_bus_child_broker,
+                      app,
+                      &pid,
+                      &error))
+    {
+      app->a11y_bus_pid = -1;
+      app->a11y_launch_error_message = g_strdup (error->message);
+      g_clear_error (&error);
+      goto error;
+    }
+
+  close (app->listenfd);
+  app->listenfd = -1;
+
+  g_child_watch_add (pid, on_bus_exited, app);
+  app->a11y_bus_pid = pid;
+  g_debug ("Launched a11y bus, child is %ld", (long) pid);
+  app->state = A11Y_BUS_STATE_RUNNING;
+
+  app->a11y_bus_address = g_strconcat("unix:abstract=", addr.sun_path + 1, NULL);
+  g_debug ("a11y bus address: %s", app->a11y_bus_address);
+
+  return TRUE;
+
+error:
+  close (app->listenfd);
+  app->state = A11Y_BUS_STATE_ERROR;
+
+  return FALSE;
+}
+#endif
+
+static gboolean
+ensure_a11y_bus (A11yBusLauncher *app)
+{
+  char *config_path = NULL;
+  gboolean success = FALSE;
+
+  if (app->a11y_bus_pid != 0)
+    return FALSE;
+
+  if (g_file_test (SYSCONFDIR"/at-spi2/accessibility.conf", G_FILE_TEST_EXISTS))
+      config_path = "--config-file="SYSCONFDIR"/at-spi2/accessibility.conf";
+  else
+      config_path = "--config-file="DATADIR"/defaults/at-spi2/accessibility.conf";
+
+#ifdef DBUS_BROKER
+    success = ensure_a11y_bus_broker (app, config_path);
+#endif
+  if (!success)
+    {
+      if (!ensure_a11y_bus_daemon (app, config_path))
+          return FALSE;
+    }
+
 #ifdef HAVE_X11
   {
     Display *display = XOpenDisplay (NULL);
@@ -353,13 +457,6 @@ ensure_a11y_bus (A11yBusLauncher *app)
 #endif
 
   return TRUE;
-  
- error:
-  close (app->pipefd[0]);
-  close (app->pipefd[1]);
-  app->state = A11Y_BUS_STATE_ERROR;
-
-  return FALSE;
 }
 
 static void
diff --git a/bus/meson.build b/bus/meson.build
index 909103c..ba8ea2c 100644
--- a/bus/meson.build
+++ b/bus/meson.build
@@ -43,13 +43,30 @@ else
                              required: true).path()
 endif
 
-executable('at-spi-bus-launcher', 'at-spi-bus-launcher.c',
-           include_directories: [ root_inc, include_directories('.') ],
-           dependencies: [ gio_dep, x11_deps ],
-           c_args: [
+launcher_args = [
              '-DSYSCONFDIR="@0@"'.format(atspi_sysconfdir),
              '-DDATADIR="@0@"'.format(atspi_datadir),
              '-DDBUS_DAEMON="@0@"'.format(dbus_daemon),
-           ],
+           ]
+
+if get_option('dbus_broker') != 'default'
+  launcher_args += '-DDBUS_BROKER="@0@"'.format(get_option('dbus_broker'))
+else
+  dbus_broker = find_program('dbus-broker-launch',
+                             '/sbin/dbus-broker-launch',
+                             '/usr/sbin/dbus-broker-launch',
+                             '/libexec/dbus-broker-launch',
+                             '/usr/libexec/dbus-broker-launch',
+                             '/usr/pkg/bin/dbus-broker-launch',
+                             required: false)
+  if dbus_broker.found()
+    launcher_args += '-DDBUS_BROKER="@0@"'.format(dbus_broker.path())
+  endif
+endif
+
+executable('at-spi-bus-launcher', 'at-spi-bus-launcher.c',
+           include_directories: [ root_inc, include_directories('.') ],
+           dependencies: [ gio_dep, x11_deps ],
+           c_args: launcher_args,
            install: true,
            install_dir: atspi_libexecdir)
diff --git a/meson_options.txt b/meson_options.txt
index c9afe2f..494e83a 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -6,6 +6,10 @@ option('dbus_daemon',
        description: 'The path of the DBus daemon',
        type: 'string',
        value: 'default')
+option('dbus_broker',
+       description: 'The path of the DBus broker',
+       type: 'string',
+       value: 'default')
 option('systemd_user_dir',
        description: 'Location of the systemd user services',
        type: 'string',