[gnome-session/wip/benzea/systemd-user-switch: 7/13] gnome-session-ctl: Add helper binary for systemd targets

[Benjamin Berg <bberg src gnome org>]

commit c5e6515f605756bd9aa836ec0f1d001b3c7ac030
Author: Benjamin Berg <bberg redhat com>
Date:   Wed Apr 17 11:19:04 2019 +0200

    gnome-session-ctl: Add helper binary for systemd targets
    
    This binary is only intended to be used from systemd target to control
    gnome-session and do a few other tasks.

 tools/gnome-session-ctl.c | 295 ++++++++++++++++++++++++++++++++++++++++++++++
 tools/meson.build         |   4 +
 2 files changed, 299 insertions(+)
---
diff --git a/tools/gnome-session-ctl.c b/tools/gnome-session-ctl.c
new file mode 100644
index 00000000..9276a0ad
--- /dev/null
+++ b/tools/gnome-session-ctl.c
@@ -0,0 +1,295 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*-
+ * gnome-session-tl.c - Small utility program to manage gnome systemd session.
+
+   Copyright (C) 1998 Tom Tromey
+   Copyright (C) 2008,2019 Red Hat, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <config.h>
+
+#include <locale.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <systemd/sd-daemon.h>
+
+#include <glib.h>
+#include <glib-unix.h>
+#include <glib/gstdio.h>
+#include <glib/gi18n.h>
+#include <gio/gio.h>
+
+#define GSM_SERVICE_DBUS   "org.gnome.SessionManager"
+#define GSM_PATH_DBUS      "/org/gnome/SessionManager"
+#define GSM_INTERFACE_DBUS "org.gnome.SessionManager"
+
+#define SYSTEMD_DBUS            "org.freedesktop.systemd1"
+#define SYSTEMD_PATH_DBUS       "/org/freedesktop/systemd1"
+#define SYSTEMD_INTERFACE_DBUS  "org.freedesktop.systemd1.Manager"
+
+static GDBusConnection *
+get_session_bus (void)
+{
+        g_autoptr(GError) error = NULL;
+        GDBusConnection *bus;
+
+        bus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &error);
+
+        if (bus == NULL)
+                g_warning ("Couldn't connect to session bus: %s", error->message);
+
+        return bus;
+}
+
+static void
+do_signal_init (void)
+{
+        g_autoptr(GDBusConnection) connection = NULL;
+        g_autoptr(GVariant) reply = NULL;
+        g_autoptr(GError) error = NULL;
+
+        connection = get_session_bus ();
+        if (connection == NULL)
+                return;
+
+        reply = g_dbus_connection_call_sync (connection,
+                                             GSM_SERVICE_DBUS,
+                                             GSM_PATH_DBUS,
+                                             GSM_INTERFACE_DBUS,
+                                             "Initialized",
+                                             NULL,
+                                             NULL,
+                                             G_DBUS_CALL_FLAGS_NO_AUTO_START,
+                                             -1, NULL, &error);
+
+        if (error != NULL)
+                g_warning ("Failed to call signal initialization: %s",
+                           error->message);
+}
+
+static void
+do_start_unit (const gchar *unit, const char *mode)
+{
+        g_autoptr(GDBusConnection) connection = NULL;
+        g_autoptr(GVariant) reply = NULL;
+        g_autoptr(GError) error = NULL;
+
+        connection = get_session_bus ();
+        if (connection == NULL)
+                return;
+
+        reply = g_dbus_connection_call_sync (connection,
+                                             SYSTEMD_DBUS,
+                                             SYSTEMD_PATH_DBUS,
+                                             SYSTEMD_INTERFACE_DBUS,
+                                             "StartUnit",
+                                             g_variant_new ("(ss)",
+                                                            unit,
+                                                            mode),
+                                             NULL,
+                                             G_DBUS_CALL_FLAGS_NO_AUTO_START,
+                                             -1, NULL, &error);
+
+        if (error != NULL)
+                g_warning ("Failed to start shutdown target: %s",
+                           error->message);
+}
+
+static void
+do_restart_dbus (void)
+{
+        g_autoptr(GDBusConnection) connection = NULL;
+        g_autoptr(GVariant) reply = NULL;
+        g_autoptr(GError) error = NULL;
+
+        connection = get_session_bus ();
+        if (connection == NULL)
+                return;
+
+        reply = g_dbus_connection_call_sync (connection,
+                                             SYSTEMD_DBUS,
+                                             SYSTEMD_PATH_DBUS,
+                                             SYSTEMD_INTERFACE_DBUS,
+                                             "TryRestartUnit",
+                                             g_variant_new ("(ss)",
+                                                            "dbus.service",
+                                                            "replace"),
+                                             NULL,
+                                             G_DBUS_CALL_FLAGS_NO_AUTO_START,
+                                             -1, NULL, &error);
+
+        if (error != NULL)
+                g_warning ("Failed to restart DBus service: %s",
+                           error->message);
+}
+
+typedef struct {
+        GMainLoop *loop;
+        gint fifo_fd;
+} MonitorLeader;
+
+static gboolean
+leader_term_or_int_signal_cb (gpointer user_data)
+{
+        MonitorLeader *data = (MonitorLeader*) user_data;
+
+        g_main_quit (data->loop);
+
+        return G_SOURCE_REMOVE;
+}
+
+static gboolean
+leader_fifo_io_cb (gint fd,
+                   GIOCondition condition,
+                   gpointer user_data)
+{
+        MonitorLeader *data = (MonitorLeader*) user_data;
+
+        sd_notify (0, "STOPPING=1");
+
+        if (condition | G_IO_IN) {
+                char buf[1];
+                read (data->fifo_fd, buf, 1);
+        }
+        if (condition | G_IO_HUP) {
+                g_main_loop_quit (data->loop);
+        }
+
+        return G_SOURCE_CONTINUE;
+}
+
+/**
+ * do_monitor_leader:
+ *
+ * Function to monitor the leader to ensure clean session shutdown and
+ * propagation of this information to/from loginctl/GDM.
+ * See main.c systemd_leader_run() for more information.
+ */
+static void
+do_monitor_leader (void)
+{
+        MonitorLeader data;
+        g_autofree char *fifo_name = NULL;
+        int res;
+
+        data.loop = g_main_loop_new (NULL, TRUE);
+
+        fifo_name = g_strdup_printf ("%s/gnome-session-leader-fifo",
+                                     g_get_user_runtime_dir ());
+        res = mkfifo (fifo_name, 0666);
+        if (res < 0 && errno != -EEXIST)
+                g_warning ("Error creating FIFO: %m");
+
+        data.fifo_fd = g_open (fifo_name, O_RDONLY | O_CLOEXEC, 0666);
+        if (data.fifo_fd >= 0) {
+                struct stat buf;
+
+                res = fstat (data.fifo_fd, &buf);
+                if (res < 0) {
+                        g_warning ("Unable to monitor session leader: stat failed with error %m");
+                        sd_notifyf (0, "STATUS=Unable to monitor session leader: FD is not a FIFO %m");
+                        close (data.fifo_fd);
+                        data.fifo_fd = -1;
+                } else if (!(buf.st_mode & S_IFIFO)) {
+                        g_warning ("Unable to monitor session leader: FD is not a FIFO");
+                        sd_notify (0, "STATUS=Unable to monitor session leader: FD is not a FIFO");
+                        close (data.fifo_fd);
+                        data.fifo_fd = -1;
+                } else {
+                        sd_notify (0, "STATUS=Watching session leader");
+                        g_unix_fd_add (data.fifo_fd, G_IO_HUP | G_IO_IN, leader_fifo_io_cb, &data);
+                }
+        } else {
+                g_warning ("Unable to monitor session leader: Opening FIFO failed with %m");
+                sd_notifyf (0, "STATUS=Unable to monitor session leader: Opening FIFO failed with %m");
+        }
+
+        g_unix_signal_add (SIGTERM, leader_term_or_int_signal_cb, &data);
+        g_unix_signal_add (SIGINT, leader_term_or_int_signal_cb, &data);
+
+        g_main_loop_run (data.loop);
+
+        g_main_loop_unref (data.loop);
+        /* FD is closed with the application. */
+}
+
+int
+main (int argc, char *argv[])
+{
+        g_autoptr(GError) error = NULL;
+        static gboolean   opt_shutdown;
+        static gboolean   opt_monitor;
+        static gboolean   opt_signal_init;
+        static gboolean   opt_restart_dbus;
+        int     conflicting_options;
+        GOptionContext *ctx;
+        static const GOptionEntry options[] = {
+                { "shutdown", '\0', 0, G_OPTION_ARG_NONE, &opt_shutdown, N_("Start 
gnome-session-shutdown.target"), NULL },
+                { "monitor", '\0', 0, G_OPTION_ARG_NONE, &opt_monitor, N_("Start 
gnome-session-shutdown.target when receiving EOF or a single byte on stdin"), NULL },
+                { "signal-init", '\0', 0, G_OPTION_ARG_NONE, &opt_signal_init, N_("Signal initialization 
done to gnome-session"), NULL },
+                { "restart-dbus", '\0', 0, G_OPTION_ARG_NONE, &opt_restart_dbus, N_("Restart dbus.service if 
it is running"), NULL },
+                { NULL },
+        };
+
+        /* Initialize the i18n stuff */
+        setlocale (LC_ALL, "");
+        bindtextdomain (GETTEXT_PACKAGE, LOCALE_DIR);
+        bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
+        textdomain (GETTEXT_PACKAGE);
+
+        ctx = g_option_context_new ("");
+        g_option_context_add_main_entries (ctx, options, GETTEXT_PACKAGE);
+        if (! g_option_context_parse (ctx, &argc, &argv, &error)) {
+                g_warning ("Unable to start: %s", error->message);
+                exit (1);
+        }
+        g_option_context_free (ctx);
+
+        conflicting_options = 0;
+        if (opt_shutdown)
+                conflicting_options++;
+        if (opt_monitor)
+                conflicting_options++;
+        if (opt_signal_init)
+                conflicting_options++;
+        if (opt_restart_dbus)
+                conflicting_options++;
+        if (conflicting_options != 1) {
+                g_printerr (_("Program needs exactly one parameter"));
+                exit (1);
+        }
+
+        sd_notify (0, "READY=1");
+
+        if (opt_signal_init) {
+                do_signal_init ();
+        } else if (opt_restart_dbus) {
+                do_restart_dbus ();
+        } else if (opt_shutdown) {
+                do_start_unit ("gnome-session-shutdown.target", "replace-irreversibly");
+        } else if (opt_monitor) {
+                do_monitor_leader ();
+                do_start_unit ("gnome-session-shutdown.target", "replace-irreversibly");
+       } else {
+                g_assert_not_reached ();
+        }
+
+        return 0;
+}
diff --git a/tools/meson.build b/tools/meson.build
index 10ee918c..68be8a4a 100644
--- a/tools/meson.build
+++ b/tools/meson.build
@@ -16,6 +16,10 @@ programs = [
   ['gnome-session-inhibit', session_deps, cflags, session_bindir]
 ]
 
+if enable_systemd_session
+  programs += [['gnome-session-ctl', session_bin_deps, cflags, session_libexecdir]]
+endif
+
 if enable_session_selector
   deps = [
     glib_dep,