Prepare startContainer() to have more action

Currently startContainer() is used to create and to run a container.
In the next patch it will be used to restore a container.

Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

restore.go

@@ -5,13 +5,8 @@ package main
 import (
 	"fmt"
 	"os"
-	"syscall"
 
-	"github.com/Sirupsen/logrus"
 	"github.com/opencontainers/runc/libcontainer"
-	"github.com/opencontainers/runc/libcontainer/configs"
-	"github.com/opencontainers/runc/libcontainer/specconv"
-	"github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/urfave/cli"
 )
 
@@ -92,111 +87,22 @@ using the runc checkpoint command.`,
 			return fmt.Errorf("runc restore requires root")
 		}
 
-		imagePath := context.String("image-path")
-		id := context.Args().First()
-		if id == "" {
-			return errEmptyID
-		}
-		if imagePath == "" {
-			imagePath = getDefaultImagePath(context)
-		}
-		bundle := context.String("bundle")
-		if bundle != "" {
-			if err := os.Chdir(bundle); err != nil {
-				return err
-			}
-		}
-		spec, err := loadSpec(specConfig)
+		spec, err := setupSpec(context)
 		if err != nil {
 			return err
 		}
-		config, err := specconv.CreateLibcontainerConfig(&specconv.CreateOpts{
-			CgroupName:       id,
-			UseSystemdCgroup: context.GlobalBool("systemd-cgroup"),
-			NoPivotRoot:      context.Bool("no-pivot"),
-			Spec:             spec,
-		})
+		options := criuOptions(context)
+		status, err := startContainer(context, spec, CT_ACT_RESTORE, options)
 		if err != nil {
 			return err
 		}
-		status, err := restoreContainer(context, spec, config, imagePath)
-		if err == nil {
-			os.Exit(status)
-		}
-		return err
+		// exit with the container's exit status so any external supervisor is
+		// notified of the exit with the correct exit status.
+		os.Exit(status)
+		return nil
 	},
 }
 
-func restoreContainer(context *cli.Context, spec *specs.Spec, config *configs.Config, imagePath string) (int, error) {
-	var (
-		rootuid = 0
-		rootgid = 0
-		id      = context.Args().First()
-	)
-	factory, err := loadFactory(context)
-	if err != nil {
-		return -1, err
-	}
-	container, err := factory.Load(id)
-	if err != nil {
-		container, err = factory.Create(id, config)
-		if err != nil {
-			return -1, err
-		}
-	}
-	options := criuOptions(context)
-
-	status, err := container.Status()
-	if err != nil {
-		logrus.Error(err)
-	}
-	if status == libcontainer.Running {
-		fatalf("Container with id %s already running", id)
-	}
-
-	setManageCgroupsMode(context, options)
-
-	if err = setEmptyNsMask(context, options); err != nil {
-		return -1, err
-	}
-
-	// ensure that the container is always removed if we were the process
-	// that created it.
-	detach := context.Bool("detach")
-	if !detach {
-		defer destroy(container)
-	}
-	process := &libcontainer.Process{}
-	tty, err := setupIO(process, rootuid, rootgid, false, detach, "")
-	if err != nil {
-		return -1, err
-	}
-
-	notifySocket := newNotifySocket(context, os.Getenv("NOTIFY_SOCKET"), id)
-	if notifySocket != nil {
-		notifySocket.setupSpec(context, spec)
-		notifySocket.setupSocket()
-	}
-
-	handler := newSignalHandler(!context.Bool("no-subreaper"), notifySocket)
-	if err := container.Restore(process, options); err != nil {
-		return -1, err
-	}
-	// We don't need to do a tty.recvtty because config.Terminal is always false.
-	defer tty.Close()
-	if err := tty.ClosePostStart(); err != nil {
-		return -1, err
-	}
-	if pidFile := context.String("pid-file"); pidFile != "" {
-		if err := createPidFile(pidFile, process); err != nil {
-			_ = process.Signal(syscall.SIGKILL)
-			_, _ = process.Wait()
-			return -1, err
-		}
-	}
-	return handler.forward(process, tty, detach)
-}
-
 func criuOptions(context *cli.Context) *libcontainer.CriuOpts {
 	imagePath := getCheckpointImagePath(context)
 	if err := os.MkdirAll(imagePath, 0655); err != nil {