restore: make IsCheckpointImage reusable

Podman allows to store a container checkpoints as an images.
This patch makes the check that is used to recognise such checkpoint
images reusable by moving it in utils. This functionality will be reused
in a subsequent patch to extend the `podman run` command with support
for checkpoint images.

Signed-off-by: Radostin Stoyanov <radostin@redhat.com>

cmd/podman/containers/restore.go

@@ -10,7 +10,6 @@ import (
 	"github.com/containers/podman/v4/cmd/podman/registry"
 	"github.com/containers/podman/v4/cmd/podman/utils"
 	"github.com/containers/podman/v4/cmd/podman/validate"
-	"github.com/containers/podman/v4/libpod/define"
 	"github.com/containers/podman/v4/pkg/domain/entities"
 	"github.com/containers/podman/v4/pkg/rootless"
 	"github.com/spf13/cobra"
@@ -116,26 +115,9 @@ func restore(cmd *cobra.Command, args []string) error {
 
 	if !exists.Value {
 		// Find out if this is an image
-		inspectOpts := entities.InspectOptions{}
+		restoreOptions.CheckpointImage, e = utils.IsCheckpointImage(context.Background(), args)
-		imgData, _, err := registry.ImageEngine().Inspect(context.Background(), args, inspectOpts)
+		if e != nil {
-		if err != nil {
+			return e
-			return err
-		}
-
-		hostInfo, err := registry.ContainerEngine().Info(context.Background())
-		if err != nil {
-			return err
-		}
-
-		for i := range imgData {
-			restoreOptions.CheckpointImage = true
-			checkpointRuntimeName, found := imgData[i].Annotations[define.CheckpointAnnotationRuntimeName]
-			if !found {
-				return fmt.Errorf("image is not a checkpoint: %s", imgData[i].ID)
-			}
-			if hostInfo.Host.OCIRuntime.Name != checkpointRuntimeName {
-				return fmt.Errorf("container image \"%s\" requires runtime: \"%s\"", imgData[i].ID, checkpointRuntimeName)
-			}
 		}
 	}
 

cmd/podman/utils/utils.go

@@ -1,9 +1,12 @@
 package utils
 
 import (
+	"context"
 	"fmt"
 	"os"
 
+	"github.com/containers/podman/v4/cmd/podman/registry"
+	"github.com/containers/podman/v4/libpod/define"
 	"github.com/containers/podman/v4/pkg/domain/entities"
 	"github.com/containers/podman/v4/pkg/domain/entities/reports"
 )
@@ -99,3 +102,40 @@ func PrintNetworkPruneResults(networkPruneReport []*entities.NetworkPruneReport,
 	}
 	return errs.PrintErrors()
 }
+
+// IsCheckpointImage returns true with no error only if all values in
+// namesOrIDs correspond to checkpoint images AND these images are
+// compatible with the container runtime that is currently in use,
+// e.g., crun or runc.
+//
+// IsCheckpointImage returns false with no error when none of the values
+// in namesOrIDs corresponds to an ID or name of an image.
+//
+// Otherwise, IsCheckpointImage returns false with appropriate error.
+func IsCheckpointImage(ctx context.Context, namesOrIDs []string) (bool, error) {
+	inspectOpts := entities.InspectOptions{}
+	imgData, _, err := registry.ImageEngine().Inspect(ctx, namesOrIDs, inspectOpts)
+	if err != nil {
+		return false, err
+	}
+	if len(imgData) == 0 {
+		return false, nil
+	}
+	imgID := imgData[0].ID
+
+	hostInfo, err := registry.ContainerEngine().Info(ctx)
+	if err != nil {
+		return false, err
+	}
+
+	for i := range imgData {
+		checkpointRuntimeName, found := imgData[i].Annotations[define.CheckpointAnnotationRuntimeName]
+		if !found {
+			return false, fmt.Errorf("image is not a checkpoint: %s", imgID)
+		}
+		if hostInfo.Host.OCIRuntime.Name != checkpointRuntimeName {
+			return false, fmt.Errorf("container image \"%s\" requires runtime: \"%s\"", imgID, checkpointRuntimeName)
+		}
+	}
+	return true, nil
+}