Move checkpoint/restore code to pkg/checkpoint/crutils

To be able to reuse common checkpoint/restore functions this commit
moves code to pkg/checkpoint/crutils.

This commit has not functional changes. It only moves code around.

[NO TESTS NEEDED] - only moving code around

Signed-off-by: Adrian Reber <areber@redhat.com>

4 files changed, 217 insertions, 153 deletions

diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index dc0418148..24112ae09 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -33,6 +33,7 @@ import (
 	"github.com/containers/podman/v3/libpod/events"
 	"github.com/containers/podman/v3/pkg/annotations"
 	"github.com/containers/podman/v3/pkg/cgroups"
+	"github.com/containers/podman/v3/pkg/checkpoint/crutils"
 	"github.com/containers/podman/v3/pkg/criu"
 	"github.com/containers/podman/v3/pkg/lookup"
 	"github.com/containers/podman/v3/pkg/resolvconf"
@@ -895,69 +896,20 @@ func (c *Container) exportCheckpoint(options ContainerCheckpointOptions) error {
 		includeFiles[0] = "pre-checkpoint"
 	}
 	// Get root file-system changes included in the checkpoint archive
-	rootfsDiffPath := filepath.Join(c.bundlePath(), "rootfs-diff.tar")
-	deleteFilesList := filepath.Join(c.bundlePath(), "deleted.files")
+	var addToTarFiles []string
 	if !options.IgnoreRootfs {
 		// To correctly track deleted files, let's go through the output of 'podman diff'
-		tarFiles, err := c.runtime.GetDiff("", c.ID())
+		rootFsChanges, err := c.runtime.GetDiff("", c.ID())
 		if err != nil {
-			return errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
+			return errors.Wrapf(err, "error exporting root file-system diff for %q", c.ID())
 		}
-		var rootfsIncludeFiles []string
-		var deletedFiles []string
 
-		for _, file := range tarFiles {
-			if file.Kind == archive.ChangeAdd {
-				rootfsIncludeFiles = append(rootfsIncludeFiles, file.Path)
-				continue
-			}
-			if file.Kind == archive.ChangeDelete {
-				deletedFiles = append(deletedFiles, file.Path)
-				continue
-			}
-			fileName, err := os.Stat(file.Path)
-			if err != nil {
-				continue
-			}
-			if !fileName.IsDir() && file.Kind == archive.ChangeModify {
-				rootfsIncludeFiles = append(rootfsIncludeFiles, file.Path)
-				continue
-			}
-		}
-
-		if len(rootfsIncludeFiles) > 0 {
-			rootfsTar, err := archive.TarWithOptions(c.state.Mountpoint, &archive.TarOptions{
-				Compression:      archive.Uncompressed,
-				IncludeSourceDir: true,
-				IncludeFiles:     rootfsIncludeFiles,
-			})
-			if err != nil {
-				return errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
-			}
-			rootfsDiffFile, err := os.Create(rootfsDiffPath)
-			if err != nil {
-				return errors.Wrapf(err, "error creating root file-system diff file %q", rootfsDiffPath)
-			}
-			defer rootfsDiffFile.Close()
-			_, err = io.Copy(rootfsDiffFile, rootfsTar)
-			if err != nil {
-				return err
-			}
-
-			includeFiles = append(includeFiles, "rootfs-diff.tar")
+		addToTarFiles, err := crutils.CRCreateRootFsDiffTar(&rootFsChanges, c.state.Mountpoint, c.bundlePath())
+		if err != nil {
+			return err
 		}
 
-		if len(deletedFiles) > 0 {
-			formatJSON, err := json.MarshalIndent(deletedFiles, "", "     ")
-			if err != nil {
-				return errors.Wrapf(err, "error creating delete files list file %q", deleteFilesList)
-			}
-			if err := ioutil.WriteFile(deleteFilesList, formatJSON, 0600); err != nil {
-				return errors.Wrap(err, "error creating delete files list file")
-			}
-
-			includeFiles = append(includeFiles, "deleted.files")
-		}
+		includeFiles = append(includeFiles, addToTarFiles...)
 	}
 
 	// Folder containing archived volumes that will be included in the export
@@ -1034,8 +986,9 @@ func (c *Container) exportCheckpoint(options ContainerCheckpointOptions) error {
 		return err
 	}
 
-	os.Remove(rootfsDiffPath)
-	os.Remove(deleteFilesList)
+	for _, file := range addToTarFiles {
+		os.Remove(filepath.Join(c.bundlePath(), file))
+	}
 
 	if !options.IgnoreVolumes {
 		os.RemoveAll(expVolDir)
@@ -1054,23 +1007,6 @@ func (c *Container) checkpointRestoreSupported() error {
 	return nil
 }
 
-func (c *Container) checkpointRestoreLabelLog(fileName string) error {
-	// Create the CRIU log file and label it
-	dumpLog := filepath.Join(c.bundlePath(), fileName)
-
-	logFile, err := os.OpenFile(dumpLog, os.O_CREATE, 0600)
-	if err != nil {
-		return errors.Wrap(err, "failed to create CRIU log file")
-	}
-	if err := logFile.Close(); err != nil {
-		logrus.Error(err)
-	}
-	if err = label.SetFileLabel(dumpLog, c.MountLabel()); err != nil {
-		return err
-	}
-	return nil
-}
-
 func (c *Container) checkpoint(ctx context.Context, options ContainerCheckpointOptions) error {
 	if err := c.checkpointRestoreSupported(); err != nil {
 		return err
@@ -1084,7 +1020,7 @@ func (c *Container) checkpoint(ctx context.Context, options ContainerCheckpointO
 		return errors.Errorf("cannot checkpoint containers that have been started with '--rm' unless '--export' is used")
 	}
 
-	if err := c.checkpointRestoreLabelLog("dump.log"); err != nil {
+	if err := crutils.CRCreateFileWithLabel(c.bundlePath(), "dump.log", c.MountLabel()); err != nil {
 		return err
 	}
 
@@ -1151,28 +1087,13 @@ func (c *Container) checkpoint(ctx context.Context, options ContainerCheckpointO
 }
 
 func (c *Container) importCheckpoint(input string) error {
-	archiveFile, err := os.Open(input)
-	if err != nil {
-		return errors.Wrap(err, "failed to open checkpoint archive for import")
-	}
-
-	defer archiveFile.Close()
-	options := &archive.TarOptions{
-		ExcludePatterns: []string{
-			// config.dump and spec.dump are only required
-			// container creation
-			"config.dump",
-			"spec.dump",
-		},
-	}
-	err = archive.Untar(archiveFile, c.bundlePath(), options)
-	if err != nil {
-		return errors.Wrapf(err, "unpacking of checkpoint archive %s failed", input)
+	if err := crutils.CRImportCheckpointWithoutConfig(c.bundlePath(), input); err != nil {
+		return err
 	}
 
 	// Make sure the newly created config.json exists on disk
 	g := generate.Generator{Config: c.config.Spec}
-	if err = c.saveSpec(g.Config); err != nil {
+	if err := c.saveSpec(g.Config); err != nil {
 		return errors.Wrap(err, "saving imported container specification for restore failed")
 	}
 
@@ -1221,7 +1142,7 @@ func (c *Container) restore(ctx context.Context, options ContainerCheckpointOpti
 		return errors.Wrapf(err, "a complete checkpoint for this container cannot be found, cannot restore")
 	}
 
-	if err := c.checkpointRestoreLabelLog("restore.log"); err != nil {
+	if err := crutils.CRCreateFileWithLabel(c.bundlePath(), "restore.log", c.MountLabel()); err != nil {
 		return err
 	}
 
@@ -1398,36 +1319,12 @@ func (c *Container) restore(ctx context.Context, options ContainerCheckpointOpti
 
 	// Before actually restarting the container, apply the root file-system changes
 	if !options.IgnoreRootfs {
-		rootfsDiffPath := filepath.Join(c.bundlePath(), "rootfs-diff.tar")
-		if _, err := os.Stat(rootfsDiffPath); err == nil {
-			// Only do this if a rootfs-diff.tar actually exists
-			rootfsDiffFile, err := os.Open(rootfsDiffPath)
-			if err != nil {
-				return errors.Wrap(err, "failed to open root file-system diff file")
-			}
-			defer rootfsDiffFile.Close()
-			if err := c.runtime.ApplyDiffTarStream(c.ID(), rootfsDiffFile); err != nil {
-				return errors.Wrapf(err, "failed to apply root file-system diff file %s", rootfsDiffPath)
-			}
+		if err := crutils.CRApplyRootFsDiffTar(c.bundlePath(), c.state.Mountpoint); err != nil {
+			return err
 		}
-		deletedFilesPath := filepath.Join(c.bundlePath(), "deleted.files")
-		if _, err := os.Stat(deletedFilesPath); err == nil {
-			var deletedFiles []string
-			deletedFilesJSON, err := ioutil.ReadFile(deletedFilesPath)
-			if err != nil {
-				return errors.Wrapf(err, "failed to read deleted files file")
-			}
-			if err := json.Unmarshal(deletedFilesJSON, &deletedFiles); err != nil {
-				return errors.Wrapf(err, "failed to unmarshal deleted files file %s", deletedFilesPath)
-			}
-			for _, deleteFile := range deletedFiles {
-				// Using RemoveAll as deletedFiles, which is generated from 'podman diff'
-				// lists completely deleted directories as a single entry: 'D /root'.
-				err = os.RemoveAll(filepath.Join(c.state.Mountpoint, deleteFile))
-				if err != nil {
-					return errors.Wrapf(err, "failed to delete files from container %s during restore", c.ID())
-				}
-			}
+
+		if err := crutils.CRRemoveDeletedFiles(c.ID(), c.bundlePath(), c.state.Mountpoint); err != nil {
+			return err
 		}
 	}
 
diff --git a/libpod/oci_conmon_linux.go b/libpod/oci_conmon_linux.go
index de7630c06..492bc807a 100644
--- a/libpod/oci_conmon_linux.go
+++ b/libpod/oci_conmon_linux.go
@@ -28,6 +28,7 @@ import (
 	"github.com/containers/podman/v3/libpod/define"
 	"github.com/containers/podman/v3/libpod/logs"
 	"github.com/containers/podman/v3/pkg/cgroups"
+	"github.com/containers/podman/v3/pkg/checkpoint/crutils"
 	"github.com/containers/podman/v3/pkg/errorhandling"
 	"github.com/containers/podman/v3/pkg/lookup"
 	"github.com/containers/podman/v3/pkg/rootless"
@@ -837,16 +838,7 @@ func (r *ConmonOCIRuntime) CheckConmonRunning(ctr *Container) (bool, error) {
 // SupportsCheckpoint checks if the OCI runtime supports checkpointing
 // containers.
 func (r *ConmonOCIRuntime) SupportsCheckpoint() bool {
-	// Check if the runtime implements checkpointing. Currently only
-	// runc's checkpoint/restore implementation is supported.
-	cmd := exec.Command(r.path, "checkpoint", "--help")
-	if err := cmd.Start(); err != nil {
-		return false
-	}
-	if err := cmd.Wait(); err == nil {
-		return true
-	}
-	return false
+	return crutils.CRRuntimeSupportsCheckpointRestore(r.path)
 }
 
 // SupportsJSONErrors checks if the OCI runtime supports JSON-formatted error
diff --git a/pkg/checkpoint/checkpoint_restore.go b/pkg/checkpoint/checkpoint_restore.go
index 6285680c0..dd40443b9 100644
--- a/pkg/checkpoint/checkpoint_restore.go
+++ b/pkg/checkpoint/checkpoint_restore.go
@@ -4,15 +4,14 @@ import (
 	"context"
 	"io/ioutil"
 	"os"
-	"path/filepath"
 
+	metadata "github.com/checkpoint-restore/checkpointctl/lib"
 	"github.com/containers/podman/v3/libpod"
 	"github.com/containers/podman/v3/libpod/image"
 	"github.com/containers/podman/v3/pkg/domain/entities"
 	"github.com/containers/podman/v3/pkg/errorhandling"
 	"github.com/containers/podman/v3/pkg/util"
 	"github.com/containers/storage/pkg/archive"
-	jsoniter "github.com/json-iterator/go"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -20,21 +19,6 @@ import (
 
 // Prefixing the checkpoint/restore related functions with 'cr'
 
-// crImportFromJSON imports the JSON files stored in the exported
-// checkpoint tarball
-func crImportFromJSON(filePath string, v interface{}) error {
-	content, err := ioutil.ReadFile(filePath)
-	if err != nil {
-		return errors.Wrap(err, "failed to read container definition for restore")
-	}
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	if err = json.Unmarshal(content, v); err != nil {
-		return errors.Wrapf(err, "failed to unmarshal container definition %s for restore", filePath)
-	}
-
-	return nil
-}
-
 // CRImportCheckpoint it the function which imports the information
 // from checkpoint tarball and re-creates the container from that information
 func CRImportCheckpoint(ctx context.Context, runtime *libpod.Runtime, restoreOptions entities.RestoreOptions) ([]*libpod.Container, error) {
@@ -73,13 +57,13 @@ func CRImportCheckpoint(ctx context.Context, runtime *libpod.Runtime, restoreOpt
 
 	// Load spec.dump from temporary directory
 	dumpSpec := new(spec.Spec)
-	if err := crImportFromJSON(filepath.Join(dir, "spec.dump"), dumpSpec); err != nil {
+	if _, err := metadata.ReadJSONFile(dumpSpec, dir, metadata.SpecDumpFile); err != nil {
 		return nil, err
 	}
 
 	// Load config.dump from temporary directory
 	config := new(libpod.ContainerConfig)
-	if err = crImportFromJSON(filepath.Join(dir, "config.dump"), config); err != nil {
+	if _, err = metadata.ReadJSONFile(config, dir, metadata.ConfigDumpFile); err != nil {
 		return nil, err
 	}
 
diff --git a/pkg/checkpoint/crutils/checkpoint_restore_utils.go b/pkg/checkpoint/crutils/checkpoint_restore_utils.go
new file mode 100644
index 000000000..53ff55865
--- /dev/null
+++ b/pkg/checkpoint/crutils/checkpoint_restore_utils.go
@@ -0,0 +1,191 @@
+package crutils
+
+import (
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	metadata "github.com/checkpoint-restore/checkpointctl/lib"
+	"github.com/containers/storage/pkg/archive"
+	"github.com/opencontainers/selinux/go-selinux/label"
+	"github.com/pkg/errors"
+)
+
+// This file mainly exist to make the checkpoint/restore functions
+// available for other users. One possible candidate would be CRI-O.
+
+// CRImportCheckpointWithoutConfig imports the checkpoint archive (input)
+// into the directory destination without "config.dump" and "spec.dump"
+func CRImportCheckpointWithoutConfig(destination, input string) error {
+	archiveFile, err := os.Open(input)
+	if err != nil {
+		return errors.Wrapf(err, "Failed to open checkpoint archive %s for import", input)
+	}
+
+	defer archiveFile.Close()
+	options := &archive.TarOptions{
+		ExcludePatterns: []string{
+			// Import everything else besides the container config
+			metadata.ConfigDumpFile,
+			metadata.SpecDumpFile,
+		},
+	}
+	if err = archive.Untar(archiveFile, destination, options); err != nil {
+		return errors.Wrapf(err, "Unpacking of checkpoint archive %s failed", input)
+	}
+
+	return nil
+}
+
+// CRRemoveDeletedFiles loads the list of deleted files and if
+// it exists deletes all files listed.
+func CRRemoveDeletedFiles(id, baseDirectory, containerRootDirectory string) error {
+	deletedFiles, _, err := metadata.ReadContainerCheckpointDeletedFiles(baseDirectory)
+	if os.IsNotExist(errors.Unwrap(errors.Unwrap(err))) {
+		// No files to delete. Just return
+		return nil
+	}
+
+	if err != nil {
+		return errors.Wrapf(err, "failed to read deleted files file")
+	}
+
+	for _, deleteFile := range deletedFiles {
+		// Using RemoveAll as deletedFiles, which is generated from 'podman diff'
+		// lists completely deleted directories as a single entry: 'D /root'.
+		if err := os.RemoveAll(filepath.Join(containerRootDirectory, deleteFile)); err != nil {
+			return errors.Wrapf(err, "failed to delete files from container %s during restore", id)
+		}
+	}
+
+	return nil
+}
+
+// CRApplyRootFsDiffTar applies the tar archive found in baseDirectory with the
+// root file system changes on top of containerRootDirectory
+func CRApplyRootFsDiffTar(baseDirectory, containerRootDirectory string) error {
+	rootfsDiffPath := filepath.Join(baseDirectory, metadata.RootFsDiffTar)
+	if _, err := os.Stat(rootfsDiffPath); err != nil {
+		// Only do this if a rootfs-diff.tar actually exists
+		return nil
+	}
+
+	rootfsDiffFile, err := os.Open(rootfsDiffPath)
+	if err != nil {
+		return errors.Wrap(err, "failed to open root file-system diff file")
+	}
+	defer rootfsDiffFile.Close()
+
+	if err := archive.Untar(rootfsDiffFile, containerRootDirectory, nil); err != nil {
+		return errors.Wrapf(err, "failed to apply root file-system diff file %s", rootfsDiffPath)
+	}
+
+	return nil
+}
+
+// CRCreateRootFsDiffTar goes through the 'changes' and can create two files:
+// * metadata.RootFsDiffTar will contain all new and changed files
+// * metadata.DeletedFilesFile will contain a list of deleted files
+// With these two files it is possible to restore the container file system to the same
+// state it was during checkpointing.
+// Changes to directories (owner, mode) are not handled.
+func CRCreateRootFsDiffTar(changes *[]archive.Change, mountPoint, destination string) (includeFiles []string, err error) {
+	if len(*changes) == 0 {
+		return includeFiles, nil
+	}
+
+	var rootfsIncludeFiles []string
+	var deletedFiles []string
+
+	rootfsDiffPath := filepath.Join(destination, metadata.RootFsDiffTar)
+
+	for _, file := range *changes {
+		if file.Kind == archive.ChangeAdd {
+			rootfsIncludeFiles = append(rootfsIncludeFiles, file.Path)
+			continue
+		}
+		if file.Kind == archive.ChangeDelete {
+			deletedFiles = append(deletedFiles, file.Path)
+			continue
+		}
+		fileName, err := os.Stat(file.Path)
+		if err != nil {
+			continue
+		}
+		if !fileName.IsDir() && file.Kind == archive.ChangeModify {
+			rootfsIncludeFiles = append(rootfsIncludeFiles, file.Path)
+			continue
+		}
+	}
+
+	if len(rootfsIncludeFiles) > 0 {
+		rootfsTar, err := archive.TarWithOptions(mountPoint, &archive.TarOptions{
+			Compression:      archive.Uncompressed,
+			IncludeSourceDir: true,
+			IncludeFiles:     rootfsIncludeFiles,
+		})
+		if err != nil {
+			return includeFiles, errors.Wrapf(err, "error exporting root file-system diff to %q", rootfsDiffPath)
+		}
+		rootfsDiffFile, err := os.Create(rootfsDiffPath)
+		if err != nil {
+			return includeFiles, errors.Wrapf(err, "error creating root file-system diff file %q", rootfsDiffPath)
+		}
+		defer rootfsDiffFile.Close()
+		if _, err = io.Copy(rootfsDiffFile, rootfsTar); err != nil {
+			return includeFiles, err
+		}
+
+		includeFiles = append(includeFiles, metadata.RootFsDiffTar)
+	}
+
+	if len(deletedFiles) == 0 {
+		return includeFiles, nil
+	}
+
+	if _, err := metadata.WriteJSONFile(deletedFiles, destination, metadata.DeletedFilesFile); err != nil {
+		return includeFiles, nil
+	}
+
+	includeFiles = append(includeFiles, metadata.DeletedFilesFile)
+
+	return includeFiles, nil
+}
+
+// CRCreateFileWithLabel creates an empty file and sets the corresponding ('fileLabel')
+// SELinux label on the file.
+// This is necessary for CRIU log files because CRIU infects the processes in
+// the container with a 'parasite' and this will also try to write to the log files
+// from the context of the container processes.
+func CRCreateFileWithLabel(directory, fileName, fileLabel string) error {
+	logFileName := filepath.Join(directory, fileName)
+
+	logFile, err := os.OpenFile(logFileName, os.O_CREATE, 0o600)
+	if err != nil {
+		return errors.Wrapf(err, "failed to create file %q", logFileName)
+	}
+	defer logFile.Close()
+	if err = label.SetFileLabel(logFileName, fileLabel); err != nil {
+		return errors.Wrapf(err, "failed to label file %q", logFileName)
+	}
+
+	return nil
+}
+
+// CRRuntimeSupportsCheckpointRestore tests if the given runtime at 'runtimePath'
+// supports checkpointing. The checkpoint restore interface has no definition
+// but crun implements all commands just as runc does. Whathh runc does it the
+// official definition of the checkpoint/restore interface.
+func CRRuntimeSupportsCheckpointRestore(runtimePath string) bool {
+	// Check if the runtime implements checkpointing. Currently only
+	// runc's and crun's checkpoint/restore implementation is supported.
+	cmd := exec.Command(runtimePath, "checkpoint", "--help")
+	if err := cmd.Start(); err != nil {
+		return false
+	}
+	if err := cmd.Wait(); err == nil {
+		return true
+	}
+	return false
+}