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Support symlink layer in image import.

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Signed-off-by: Lantao Liu <lantaol@google.com>
This commit is contained in:
Lantao Liu 2018-04-09 22:34:09 +00:00
parent 304045491c
commit 9f85c48e4c
1 changed files with 40 additions and 8 deletions
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48
pkg/containerd/importer/importer.go
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@ -54,13 +54,29 @@ type manifestDotJSON struct {
Parent string
}
// isLayerTar returns true if name is like "deadbeeddeadbeef/layer.tar"
// isLayerTar returns true if name is like "foobar/layer.tar"
func isLayerTar(name string) bool {
slashes := len(strings.Split(name, "/"))
return slashes == 2 && strings.HasSuffix(name, "/layer.tar")
}
// isDotJSON returns true if name is like "deadbeefdeadbeef.json"
// followSymlinkLayer returns actual layer name of the symlink layer.
// It returns "foobar/layer.tar" if the name is like
// "../foobar/layer.tar", and returns error if the name
// is not in "../foobar/layer.tar" format.
func followSymlinkLayer(name string) (string, error) {
parts := strings.Split(name, "/")
if len(parts) != 3 || parts[0] != ".." {
return "", errors.New("invalid symlink layer")
}
name = strings.TrimPrefix(name, "../")
if !isLayerTar(name) {
return "", errors.New("invalid layer tar")
}
return name, nil
}
// isDotJSON returns true if name is like "foobar.json"
func isDotJSON(name string) bool {
slashes := len(strings.Split(name, "/"))
return slashes == 1 && strings.HasSuffix(name, ".json")
@ -75,7 +91,7 @@ type imageConfig struct {
// An image MUST have `manifest.json`.
// `repositories` file in Docker Image Spec v1.0 is not supported (yet).
// Also, the current implementation assumes the implicit file name convention,
// which is not explicitly documented in the spec. (e.g. deadbeef/layer.tar)
// which is not explicitly documented in the spec. (e.g. foobar/layer.tar)
// It returns a group of image references successfully loaded.
func Import(ctx context.Context, client *containerd.Client, reader io.Reader) (_ []string, retErr error) {
ctx, done, err := client.WithLease(ctx)
@ -97,9 +113,10 @@ func Import(ctx context.Context, client *containerd.Client, reader io.Reader) (_
tr := tar.NewReader(reader)
var (
mfsts []manifestDotJSON
layers = make(map[string]ocispec.Descriptor) // key: filename (deadbeeddeadbeef/layer.tar)
configs = make(map[string]imageConfig) // key: filename (deadbeeddeadbeef.json)
mfsts []manifestDotJSON
symlinkLayers = make(map[string]string) // key: filename (foobar/layer.tar), value: linkname (targetlayerid/layer.tar)
layers = make(map[string]ocispec.Descriptor) // key: filename (foobar/layer.tar)
configs = make(map[string]imageConfig) // key: filename (foobar.json)
)
for {
hdr, err := tr.Next()
@ -109,6 +126,14 @@ func Import(ctx context.Context, client *containerd.Client, reader io.Reader) (_
if err != nil {
return nil, errors.Wrap(err, "get next file")
}
if hdr.Typeflag == tar.TypeSymlink && isLayerTar(hdr.Name) {
linkname, err := followSymlinkLayer(hdr.Linkname)
if err != nil {
return nil, errors.Wrapf(err, "follow symlink layer from %q to %q", hdr.Name, hdr.Linkname)
}
symlinkLayers[hdr.Name] = linkname
continue
}
if hdr.Typeflag != tar.TypeReg && hdr.Typeflag != tar.TypeRegA {
continue
}
@ -136,6 +161,13 @@ func Import(ctx context.Context, client *containerd.Client, reader io.Reader) (_
continue
}
}
for name, linkname := range symlinkLayers {
desc, ok := layers[linkname]
if !ok {
return nil, errors.Errorf("no target for symlink layer from %q to %q", name, linkname)
}
layers[name] = desc
}
var refs []string
defer func() {
if retErr == nil {
@ -255,7 +287,7 @@ func onUntarManifestJSON(r io.Reader) ([]manifestDotJSON, error) {
}
func onUntarLayerTar(ctx context.Context, r io.Reader, cs content.Ingester, name string, size int64) (*ocispec.Descriptor, error) {
// name is like "deadbeeddeadbeef/layer.tar" ( guaranteed by isLayerTar() )
// name is like "foobar/layer.tar" ( guaranteed by isLayerTar() )
split := strings.Split(name, "/")
// note: split[0] is not expected digest here
cw, err := cs.Writer(ctx, "layer-"+split[0], size, "")
@ -277,7 +309,7 @@ func onUntarDotJSON(ctx context.Context, r io.Reader, cs content.Ingester, name
config := imageConfig{}
config.desc.MediaType = images.MediaTypeDockerSchema2Config
config.desc.Size = size
// name is like "deadbeeddeadbeef.json" ( guaranteed by is DotJSON() )
// name is like "foobar.json" ( guaranteed by is DotJSON() )
split := strings.Split(name, ".")
cw, err := cs.Writer(ctx, "config-"+split[0], size, "")
if err != nil {