pkg/login1: initial commit

This commit adds login1 package, which is a small subset of
github.com/coreos/go-systemd/v22/login1 package with ability to use
shared D-Bus connection and with proper error handling for Reboot method
call, which is not yet provided by the upstream.

The idea is to use this package in favor of github.com/coreos/go-systemd
in agent code responsible for rebooting the node. However, this requires
tests in agent code, so it will be done in the next step.

See coreos/go-systemd#387 for more details.

Signed-off-by: Mateusz Gozdek <mgozdek@microsoft.com>

pkg/login1/login1.go

@@ -0,0 +1,61 @@
+// Package login1 is a small subset of github.com/coreos/go-systemd/v22/login1 package with
+// ability to use shared D-Bus connection and with proper error handling for Reboot method call, which
+// is not yet provided by the upstream.
+package login1
+
+import (
+	"context"
+	"fmt"
+
+	godbus "github.com/godbus/dbus/v5"
+)
+
+const (
+	// DBusDest is an object path used by systemd-logind.
+	DBusDest = "org.freedesktop.login1"
+	// DBusInterface is an systemd-logind intefrace name.
+	DBusInterface = "org.freedesktop.login1.Manager"
+	// DBusPath is a standard path to systemd-logind interface.
+	DBusPath = "/org/freedesktop/login1"
+	// DBusMethodNameReboot is a login1 manager interface method name responsible for rebooting.
+	DBusMethodNameReboot = "Reboot"
+)
+
+// Client describes functionality of provided login1 client.
+type Client interface {
+	Reboot(context.Context) error
+}
+
+// Objector describes functionality required from given D-Bus connection.
+type Objector interface {
+	Object(string, godbus.ObjectPath) godbus.BusObject
+}
+
+// Caller describes required functionality from D-Bus object.
+type Caller interface {
+	CallWithContext(ctx context.Context, method string, flags godbus.Flags, args ...interface{}) *godbus.Call
+}
+
+type rebooter struct {
+	caller Caller
+}
+
+// New creates new login1 client using given D-Bus connection.
+func New(objector Objector) (Client, error) {
+	if objector == nil {
+		return nil, fmt.Errorf("no objector given")
+	}
+
+	return &rebooter{
+		caller: objector.Object(DBusDest, DBusPath),
+	}, nil
+}
+
+// Reboot reboots machine on which it's called.
+func (r *rebooter) Reboot(ctx context.Context) error {
+	if call := r.caller.CallWithContext(ctx, DBusInterface+"."+DBusMethodNameReboot, 0, false); call.Err != nil {
+		return fmt.Errorf("calling reboot: %w", call.Err)
+	}
+
+	return nil
+}

pkg/login1/login1_test.go

@@ -0,0 +1,89 @@
+package login1_test
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+
+	godbus "github.com/godbus/dbus/v5"
+
+	"github.com/flatcar-linux/flatcar-linux-update-operator/pkg/dbus"
+	"github.com/flatcar-linux/flatcar-linux-update-operator/pkg/login1"
+)
+
+func Test_Creating_new_client_returns_error_when_no_objector_is_given(t *testing.T) {
+	t.Parallel()
+
+	client, err := login1.New(nil)
+	if err == nil {
+		t.Fatalf("Expected error creating client with no connector")
+	}
+
+	if client != nil {
+		t.Fatalf("Expected client to be nil when New returns error")
+	}
+}
+
+func Test_Rebooting(t *testing.T) {
+	t.Parallel()
+
+	t.Run("use_given_context_for_D-Bus_call", func(t *testing.T) {
+		t.Parallel()
+
+		testKey := struct{}{}
+		expectedValue := "bar"
+
+		ctx := context.WithValue(context.Background(), testKey, expectedValue)
+
+		connectionWithContextCheck := &dbus.MockConnection{
+			ObjectF: func(string, godbus.ObjectPath) godbus.BusObject {
+				return &dbus.MockObject{
+					CallWithContextF: func(ctx context.Context, method string, flags godbus.Flags, args ...interface{}) *godbus.Call {
+						if val := ctx.Value(testKey); val != expectedValue {
+							t.Fatalf("Got unexpected context on call")
+						}
+
+						return &godbus.Call{}
+					},
+				}
+			},
+		}
+
+		client, err := login1.New(connectionWithContextCheck)
+		if err != nil {
+			t.Fatalf("Unexpected error creating client: %v", err)
+		}
+
+		if err := client.Reboot(ctx); err != nil {
+			t.Fatalf("Unexpected error rebooting: %v", err)
+		}
+	})
+
+	t.Run("returns_error_when_D-Bus_call_fails", func(t *testing.T) {
+		t.Parallel()
+
+		expectedError := fmt.Errorf("reboot error")
+
+		connectionWithFailingObjectCall := &dbus.MockConnection{
+			ObjectF: func(string, godbus.ObjectPath) godbus.BusObject {
+				return &dbus.MockObject{
+					CallWithContextF: func(ctx context.Context, method string, flags godbus.Flags, args ...interface{}) *godbus.Call {
+						return &godbus.Call{
+							Err: expectedError,
+						}
+					},
+				}
+			},
+		}
+
+		client, err := login1.New(connectionWithFailingObjectCall)
+		if err != nil {
+			t.Fatalf("Unexpected error creating client: %v", err)
+		}
+
+		if err := client.Reboot(context.Background()); !errors.Is(err, expectedError) {
+			t.Fatalf("Unexpected error rebooting: %v", err)
+		}
+	})
+}