Flesh out the ping implementation

3 files changed, 184 insertions, 0 deletions

diff --git a/shared/meson.build b/shared/meson.build
index 021fe11..a937e92 100644
--- a/shared/meson.build
+++ b/shared/meson.build
@@ -3,10 +3,14 @@ srcs_libshared = [
 	'rcon-protocol.c',
 	'mc-protocol.c',
 	'config-parser.c',
+	'systemd.c',
 	'utils.c',
 ]
 
+dep_libsystemd = dependency('libsystemd')
+
 deps_libshared = [
+	dep_libsystemd,
 	dep_config_h,
 ]
 
diff --git a/shared/systemd.c b/shared/systemd.c
new file mode 100644
index 0000000..c45c7c5
--- /dev/null
+++ b/shared/systemd.c
@@ -0,0 +1,167 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <string.h>
+#include <stdlib.h>
+#include <systemd/sd-bus.h>
+#include <errno.h>
+
+#include "utils.h"
+#include "config-parser.h"
+#include "systemd.h"
+#include "config.h"
+
+static sd_bus *bus = NULL;
+static bool bus_failed = false;
+
+void systemd_delete()
+{
+	assert_return_silent(bus);
+
+	sd_bus_unref(bus);
+	bus = NULL;
+	bus_failed = false;
+}
+
+static sd_bus *get_bus()
+{
+	int r;
+
+	if (bus_failed)
+		return NULL;
+
+	if (!bus) {
+		r = sd_bus_open_user(&bus);
+		if (r < 0) {
+			error("failed to connect to user system bus: %s",
+			      strerror(-r));
+			bus_failed = true;
+			return NULL;
+		}
+	}
+
+	return bus;
+}
+
+/*
+ * Check if a systemd service is running.
+ *
+ * This is equivalent to (assuming service mc@world1):
+ *   gdbus call --session
+ *	--dest org.freedesktop.systemd1
+ *	--object-path /org/freedesktop/systemd1/unit/mc_40world1_2eservice
+ *	--method org.freedesktop.DBus.Properties.Get
+ *		"org.freedesktop.systemd1.Unit"
+ *		"ActiveState"
+ */
+bool systemd_service_running(struct server_config *scfg, const char **error)
+{
+	sd_bus *bus = get_bus();
+	sd_bus_error sderror = SD_BUS_ERROR_NULL;
+	char *status = NULL;
+	bool running = false;
+	int r;
+
+	assert_return(bus && error && scfg && scfg->systemd_service &&
+		      scfg->systemd_obj, false);
+
+again:
+	r = sd_bus_get_property_string(bus, SYSTEMD_DBUS_SERVICE,
+				       scfg->systemd_obj,
+				       SYSTEMD_DBUS_INTERFACE, "ActiveState",
+				       &sderror, &status);
+	if (r < 0) {
+		if (sd_bus_error_get_errno(&sderror) == EINTR)
+			goto again;
+
+		debug(DBG_SYSD, "failed to get status for server %s (%s): %s",
+		      scfg->systemd_service, scfg->systemd_obj, sderror.message);
+		*error = "failed to get service status";
+
+	} else if (streq(status, "active")) {
+		running = true;
+		debug(DBG_SYSD, "systemd service %s (%s) is active",
+		      scfg->systemd_service, scfg->systemd_obj);
+
+	} else {
+		debug(DBG_SYSD, "systemd service %s (%s) is not active (%s)",
+		      scfg->systemd_service, scfg->systemd_obj, status);
+		*error = "service not active";
+	}
+
+	free(status);
+	sd_bus_error_free(&sderror);
+	return running;
+}
+
+static bool systemd_service_action(struct server_config *scfg,
+				   const char *action)
+{
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+	sd_bus_message *m = NULL;
+	sd_bus *bus = get_bus();
+	const char *path;
+	bool performed = false;
+	int r;
+
+	assert_return(bus && scfg && scfg->systemd_service &&
+		      scfg->systemd_obj && action, false);
+
+again:
+	r = sd_bus_call_method(bus, SYSTEMD_DBUS_SERVICE, scfg->systemd_obj,
+			       SYSTEMD_DBUS_INTERFACE, action, &error, &m, "s",
+			       "fail");
+	if (r < 0) {
+		if (sd_bus_error_get_errno(&error) == EINTR)
+			goto again;
+
+		error("failed to perform action %s on systemd service %s: %s",
+		      action, scfg->systemd_service, error.message);
+		goto out;
+	}
+
+	r = sd_bus_message_read(m, "o", &path);
+	if (r < 0) {
+		error("failed to parse response message: %s", strerror(-r));
+		goto out;
+	}
+
+	verbose("action %s queued for service %s", action,
+		scfg->systemd_service);
+	performed = true;
+
+out:
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(m);
+	return performed;
+}
+
+/*
+ * Stop systemd service.
+ *
+ * This is equivalent to (assuming service mc@world1):
+ *   gdbus call --session
+ *	--dest org.freedesktop.systemd1
+ *	--object-path /org/freedesktop/systemd1/unit/mc_40world1_2eservice
+ *	--method org.freedesktop.systemd1.Unit.Stop "fail"
+ */
+bool systemd_service_stop(struct server_config *scfg)
+{
+	assert_return(scfg, false);
+
+	return systemd_service_action(scfg, "Stop");
+}
+
+/*
+ * Start systemd service.
+ *
+ * This is equivalent to (assuming service mc@world1):
+ *   gdbus call --session
+ *	--dest org.freedesktop.systemd1
+ *	--object-path /org/freedesktop/systemd1/unit/mc_40world1_2eservice
+ *	--method org.freedesktop.systemd1.Unit.Start "fail"
+ */
+bool systemd_service_start(struct server_config *scfg)
+{
+	assert_return(scfg, false);
+
+	return systemd_service_action(scfg, "Start");
+}
diff --git a/shared/systemd.h b/shared/systemd.h
new file mode 100644
index 0000000..0da1eca
--- /dev/null
+++ b/shared/systemd.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef foosharedsystemdhfoo
+#define foosharedsystemdhfoo
+
+void systemd_delete();
+
+bool systemd_service_running(struct server_config *scfg, const char **error);
+
+bool systemd_service_stop(struct server_config *scfg);
+
+bool systemd_service_start(struct server_config *scfg);
+
+#endif