bmc: implement reboot update mechanism

Implement an update mechanism that simply triggers a reboot of the BMC.
This implementation isn't tied into anything in the firmware handler
yet.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I116d4f631a44e7a4a999cf8ad403a00935f58710
diff --git a/update_systemd.cpp b/update_systemd.cpp
new file mode 100644
index 0000000..0802f43
--- /dev/null
+++ b/update_systemd.cpp
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2019 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "update_systemd.hpp"
+
+#include "status.hpp"
+#include "update.hpp"
+
+#include <memory>
+#include <sdbusplus/bus.hpp>
+#include <string>
+
+namespace ipmi_flash
+{
+
+std::unique_ptr<UpdateInterface>
+    SystemdUpdateMechanism::CreateSystemdUpdate(sdbusplus::bus::bus&& bus,
+                                                const std::string& target,
+                                                const std::string& mode)
+{
+    return std::make_unique<SystemdUpdateMechanism>(std::move(bus), target,
+                                                    mode);
+}
+
+bool SystemdUpdateMechanism::triggerUpdate()
+{
+    /* TODO: Add a util method for triggering a service with optional additional
+     * parameter. */
+    static constexpr auto systemdService = "org.freedesktop.systemd1";
+    static constexpr auto systemdRoot = "/org/freedesktop/systemd1";
+    static constexpr auto systemdInterface = "org.freedesktop.systemd1.Manager";
+
+    auto method = bus.new_method_call(systemdService, systemdRoot,
+                                      systemdInterface, "StartUnit");
+    method.append(target);
+
+    if (!mode.empty())
+    {
+        method.append(mode);
+    }
+
+    try
+    {
+        bus.call_noreply(method);
+        return true;
+    }
+    catch (const sdbusplus::exception::SdBusError& ex)
+    {
+        return false;
+    }
+}
+
+void SystemdUpdateMechanism::abortUpdate()
+{
+    return;
+}
+
+UpdateStatus SystemdUpdateMechanism::status()
+{
+    /* For now, don't check if the target failed. */
+    return UpdateStatus::running;
+}
+
+} // namespace ipmi_flash