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moby--moby/distribution/pull_v2.go
Stefan J. Wernli f342b27145 Removing old custom RootFS behavior on Windows.
Windows base layers are no longer the special "layers+base" type, so we can remove all the special handling for that.

Signed-off-by: Stefan J. Wernli <swernli@microsoft.com>
2016-07-29 14:15:59 -07:00

836 lines
24 KiB
Go

package distribution
import (
"encoding/json"
"errors"
"fmt"
"io"
"io/ioutil"
"net/url"
"os"
"runtime"
"github.com/Sirupsen/logrus"
"github.com/docker/distribution"
"github.com/docker/distribution/digest"
"github.com/docker/distribution/manifest/manifestlist"
"github.com/docker/distribution/manifest/schema1"
"github.com/docker/distribution/manifest/schema2"
"github.com/docker/distribution/registry/api/errcode"
"github.com/docker/distribution/registry/client/auth"
"github.com/docker/distribution/registry/client/transport"
"github.com/docker/docker/distribution/metadata"
"github.com/docker/docker/distribution/xfer"
"github.com/docker/docker/image"
"github.com/docker/docker/image/v1"
"github.com/docker/docker/layer"
"github.com/docker/docker/pkg/ioutils"
"github.com/docker/docker/pkg/progress"
"github.com/docker/docker/pkg/stringid"
"github.com/docker/docker/reference"
"github.com/docker/docker/registry"
"golang.org/x/net/context"
)
var errRootFSMismatch = errors.New("layers from manifest don't match image configuration")
// ImageConfigPullError is an error pulling the image config blob
// (only applies to schema2).
type ImageConfigPullError struct {
Err error
}
// Error returns the error string for ImageConfigPullError.
func (e ImageConfigPullError) Error() string {
return "error pulling image configuration: " + e.Err.Error()
}
type v2Puller struct {
V2MetadataService *metadata.V2MetadataService
endpoint registry.APIEndpoint
config *ImagePullConfig
repoInfo *registry.RepositoryInfo
repo distribution.Repository
// confirmedV2 is set to true if we confirm we're talking to a v2
// registry. This is used to limit fallbacks to the v1 protocol.
confirmedV2 bool
}
func (p *v2Puller) Pull(ctx context.Context, ref reference.Named) (err error) {
// TODO(tiborvass): was ReceiveTimeout
p.repo, p.confirmedV2, err = NewV2Repository(ctx, p.repoInfo, p.endpoint, p.config.MetaHeaders, p.config.AuthConfig, "pull")
if err != nil {
logrus.Warnf("Error getting v2 registry: %v", err)
return err
}
if err = p.pullV2Repository(ctx, ref); err != nil {
if _, ok := err.(fallbackError); ok {
return err
}
if continueOnError(err) {
logrus.Errorf("Error trying v2 registry: %v", err)
return fallbackError{
err: err,
confirmedV2: p.confirmedV2,
transportOK: true,
}
}
}
return err
}
func (p *v2Puller) pullV2Repository(ctx context.Context, ref reference.Named) (err error) {
var layersDownloaded bool
if !reference.IsNameOnly(ref) {
layersDownloaded, err = p.pullV2Tag(ctx, ref)
if err != nil {
return err
}
} else {
tags, err := p.repo.Tags(ctx).All(ctx)
if err != nil {
// If this repository doesn't exist on V2, we should
// permit a fallback to V1.
return allowV1Fallback(err)
}
// The v2 registry knows about this repository, so we will not
// allow fallback to the v1 protocol even if we encounter an
// error later on.
p.confirmedV2 = true
for _, tag := range tags {
tagRef, err := reference.WithTag(ref, tag)
if err != nil {
return err
}
pulledNew, err := p.pullV2Tag(ctx, tagRef)
if err != nil {
// Since this is the pull-all-tags case, don't
// allow an error pulling a particular tag to
// make the whole pull fall back to v1.
if fallbackErr, ok := err.(fallbackError); ok {
return fallbackErr.err
}
return err
}
// pulledNew is true if either new layers were downloaded OR if existing images were newly tagged
// TODO(tiborvass): should we change the name of `layersDownload`? What about message in WriteStatus?
layersDownloaded = layersDownloaded || pulledNew
}
}
writeStatus(ref.String(), p.config.ProgressOutput, layersDownloaded)
return nil
}
type v2LayerDescriptor struct {
digest digest.Digest
repoInfo *registry.RepositoryInfo
repo distribution.Repository
V2MetadataService *metadata.V2MetadataService
tmpFile *os.File
verifier digest.Verifier
src distribution.Descriptor
}
func (ld *v2LayerDescriptor) Key() string {
return "v2:" + ld.digest.String()
}
func (ld *v2LayerDescriptor) ID() string {
return stringid.TruncateID(ld.digest.String())
}
func (ld *v2LayerDescriptor) DiffID() (layer.DiffID, error) {
return ld.V2MetadataService.GetDiffID(ld.digest)
}
func (ld *v2LayerDescriptor) Download(ctx context.Context, progressOutput progress.Output) (io.ReadCloser, int64, error) {
logrus.Debugf("pulling blob %q", ld.digest)
var (
err error
offset int64
)
if ld.tmpFile == nil {
ld.tmpFile, err = createDownloadFile()
if err != nil {
return nil, 0, xfer.DoNotRetry{Err: err}
}
} else {
offset, err = ld.tmpFile.Seek(0, os.SEEK_END)
if err != nil {
logrus.Debugf("error seeking to end of download file: %v", err)
offset = 0
ld.tmpFile.Close()
if err := os.Remove(ld.tmpFile.Name()); err != nil {
logrus.Errorf("Failed to remove temp file: %s", ld.tmpFile.Name())
}
ld.tmpFile, err = createDownloadFile()
if err != nil {
return nil, 0, xfer.DoNotRetry{Err: err}
}
} else if offset != 0 {
logrus.Debugf("attempting to resume download of %q from %d bytes", ld.digest, offset)
}
}
tmpFile := ld.tmpFile
layerDownload, err := ld.open(ctx)
if err != nil {
logrus.Errorf("Error initiating layer download: %v", err)
if err == distribution.ErrBlobUnknown {
return nil, 0, xfer.DoNotRetry{Err: err}
}
return nil, 0, retryOnError(err)
}
if offset != 0 {
_, err := layerDownload.Seek(offset, os.SEEK_SET)
if err != nil {
if err := ld.truncateDownloadFile(); err != nil {
return nil, 0, xfer.DoNotRetry{Err: err}
}
return nil, 0, err
}
}
size, err := layerDownload.Seek(0, os.SEEK_END)
if err != nil {
// Seek failed, perhaps because there was no Content-Length
// header. This shouldn't fail the download, because we can
// still continue without a progress bar.
size = 0
} else {
if size != 0 && offset > size {
logrus.Debug("Partial download is larger than full blob. Starting over")
offset = 0
if err := ld.truncateDownloadFile(); err != nil {
return nil, 0, xfer.DoNotRetry{Err: err}
}
}
// Restore the seek offset either at the beginning of the
// stream, or just after the last byte we have from previous
// attempts.
_, err = layerDownload.Seek(offset, os.SEEK_SET)
if err != nil {
return nil, 0, err
}
}
reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, layerDownload), progressOutput, size-offset, ld.ID(), "Downloading")
defer reader.Close()
if ld.verifier == nil {
ld.verifier, err = digest.NewDigestVerifier(ld.digest)
if err != nil {
return nil, 0, xfer.DoNotRetry{Err: err}
}
}
_, err = io.Copy(tmpFile, io.TeeReader(reader, ld.verifier))
if err != nil {
if err == transport.ErrWrongCodeForByteRange {
if err := ld.truncateDownloadFile(); err != nil {
return nil, 0, xfer.DoNotRetry{Err: err}
}
return nil, 0, err
}
return nil, 0, retryOnError(err)
}
progress.Update(progressOutput, ld.ID(), "Verifying Checksum")
if !ld.verifier.Verified() {
err = fmt.Errorf("filesystem layer verification failed for digest %s", ld.digest)
logrus.Error(err)
// Allow a retry if this digest verification error happened
// after a resumed download.
if offset != 0 {
if err := ld.truncateDownloadFile(); err != nil {
return nil, 0, xfer.DoNotRetry{Err: err}
}
return nil, 0, err
}
return nil, 0, xfer.DoNotRetry{Err: err}
}
progress.Update(progressOutput, ld.ID(), "Download complete")
logrus.Debugf("Downloaded %s to tempfile %s", ld.ID(), tmpFile.Name())
_, err = tmpFile.Seek(0, os.SEEK_SET)
if err != nil {
tmpFile.Close()
if err := os.Remove(tmpFile.Name()); err != nil {
logrus.Errorf("Failed to remove temp file: %s", tmpFile.Name())
}
ld.tmpFile = nil
ld.verifier = nil
return nil, 0, xfer.DoNotRetry{Err: err}
}
// hand off the temporary file to the download manager, so it will only
// be closed once
ld.tmpFile = nil
return ioutils.NewReadCloserWrapper(tmpFile, func() error {
tmpFile.Close()
err := os.RemoveAll(tmpFile.Name())
if err != nil {
logrus.Errorf("Failed to remove temp file: %s", tmpFile.Name())
}
return err
}), size, nil
}
func (ld *v2LayerDescriptor) Close() {
if ld.tmpFile != nil {
ld.tmpFile.Close()
if err := os.RemoveAll(ld.tmpFile.Name()); err != nil {
logrus.Errorf("Failed to remove temp file: %s", ld.tmpFile.Name())
}
}
}
func (ld *v2LayerDescriptor) truncateDownloadFile() error {
// Need a new hash context since we will be redoing the download
ld.verifier = nil
if _, err := ld.tmpFile.Seek(0, os.SEEK_SET); err != nil {
logrus.Errorf("error seeking to beginning of download file: %v", err)
return err
}
if err := ld.tmpFile.Truncate(0); err != nil {
logrus.Errorf("error truncating download file: %v", err)
return err
}
return nil
}
func (ld *v2LayerDescriptor) Registered(diffID layer.DiffID) {
// Cache mapping from this layer's DiffID to the blobsum
ld.V2MetadataService.Add(diffID, metadata.V2Metadata{Digest: ld.digest, SourceRepository: ld.repoInfo.FullName()})
}
func (p *v2Puller) pullV2Tag(ctx context.Context, ref reference.Named) (tagUpdated bool, err error) {
manSvc, err := p.repo.Manifests(ctx)
if err != nil {
return false, err
}
var (
manifest distribution.Manifest
tagOrDigest string // Used for logging/progress only
)
if tagged, isTagged := ref.(reference.NamedTagged); isTagged {
// NOTE: not using TagService.Get, since it uses HEAD requests
// against the manifests endpoint, which are not supported by
// all registry versions.
manifest, err = manSvc.Get(ctx, "", distribution.WithTag(tagged.Tag()))
if err != nil {
return false, allowV1Fallback(err)
}
tagOrDigest = tagged.Tag()
} else if digested, isDigested := ref.(reference.Canonical); isDigested {
manifest, err = manSvc.Get(ctx, digested.Digest())
if err != nil {
return false, err
}
tagOrDigest = digested.Digest().String()
} else {
return false, fmt.Errorf("internal error: reference has neither a tag nor a digest: %s", ref.String())
}
if manifest == nil {
return false, fmt.Errorf("image manifest does not exist for tag or digest %q", tagOrDigest)
}
// If manSvc.Get succeeded, we can be confident that the registry on
// the other side speaks the v2 protocol.
p.confirmedV2 = true
logrus.Debugf("Pulling ref from V2 registry: %s", ref.String())
progress.Message(p.config.ProgressOutput, tagOrDigest, "Pulling from "+p.repo.Named().Name())
var (
imageID image.ID
manifestDigest digest.Digest
)
switch v := manifest.(type) {
case *schema1.SignedManifest:
imageID, manifestDigest, err = p.pullSchema1(ctx, ref, v)
if err != nil {
return false, err
}
case *schema2.DeserializedManifest:
imageID, manifestDigest, err = p.pullSchema2(ctx, ref, v)
if err != nil {
return false, err
}
case *manifestlist.DeserializedManifestList:
imageID, manifestDigest, err = p.pullManifestList(ctx, ref, v)
if err != nil {
return false, err
}
default:
return false, errors.New("unsupported manifest format")
}
progress.Message(p.config.ProgressOutput, "", "Digest: "+manifestDigest.String())
oldTagImageID, err := p.config.ReferenceStore.Get(ref)
if err == nil {
if oldTagImageID == imageID {
return false, addDigestReference(p.config.ReferenceStore, ref, manifestDigest, imageID)
}
} else if err != reference.ErrDoesNotExist {
return false, err
}
if canonical, ok := ref.(reference.Canonical); ok {
if err = p.config.ReferenceStore.AddDigest(canonical, imageID, true); err != nil {
return false, err
}
} else {
if err = addDigestReference(p.config.ReferenceStore, ref, manifestDigest, imageID); err != nil {
return false, err
}
if err = p.config.ReferenceStore.AddTag(ref, imageID, true); err != nil {
return false, err
}
}
return true, nil
}
func (p *v2Puller) pullSchema1(ctx context.Context, ref reference.Named, unverifiedManifest *schema1.SignedManifest) (imageID image.ID, manifestDigest digest.Digest, err error) {
var verifiedManifest *schema1.Manifest
verifiedManifest, err = verifySchema1Manifest(unverifiedManifest, ref)
if err != nil {
return "", "", err
}
rootFS := image.NewRootFS()
// remove duplicate layers and check parent chain validity
err = fixManifestLayers(verifiedManifest)
if err != nil {
return "", "", err
}
var descriptors []xfer.DownloadDescriptor
// Image history converted to the new format
var history []image.History
// Note that the order of this loop is in the direction of bottom-most
// to top-most, so that the downloads slice gets ordered correctly.
for i := len(verifiedManifest.FSLayers) - 1; i >= 0; i-- {
blobSum := verifiedManifest.FSLayers[i].BlobSum
var throwAway struct {
ThrowAway bool `json:"throwaway,omitempty"`
}
if err := json.Unmarshal([]byte(verifiedManifest.History[i].V1Compatibility), &throwAway); err != nil {
return "", "", err
}
h, err := v1.HistoryFromConfig([]byte(verifiedManifest.History[i].V1Compatibility), throwAway.ThrowAway)
if err != nil {
return "", "", err
}
history = append(history, h)
if throwAway.ThrowAway {
continue
}
layerDescriptor := &v2LayerDescriptor{
digest: blobSum,
repoInfo: p.repoInfo,
repo: p.repo,
V2MetadataService: p.V2MetadataService,
}
descriptors = append(descriptors, layerDescriptor)
}
resultRootFS, release, err := p.config.DownloadManager.Download(ctx, *rootFS, descriptors, p.config.ProgressOutput)
if err != nil {
return "", "", err
}
defer release()
config, err := v1.MakeConfigFromV1Config([]byte(verifiedManifest.History[0].V1Compatibility), &resultRootFS, history)
if err != nil {
return "", "", err
}
imageID, err = p.config.ImageStore.Create(config)
if err != nil {
return "", "", err
}
manifestDigest = digest.FromBytes(unverifiedManifest.Canonical)
return imageID, manifestDigest, nil
}
func (p *v2Puller) pullSchema2(ctx context.Context, ref reference.Named, mfst *schema2.DeserializedManifest) (imageID image.ID, manifestDigest digest.Digest, err error) {
manifestDigest, err = schema2ManifestDigest(ref, mfst)
if err != nil {
return "", "", err
}
target := mfst.Target()
imageID = image.ID(target.Digest)
if _, err := p.config.ImageStore.Get(imageID); err == nil {
// If the image already exists locally, no need to pull
// anything.
return imageID, manifestDigest, nil
}
var descriptors []xfer.DownloadDescriptor
// Note that the order of this loop is in the direction of bottom-most
// to top-most, so that the downloads slice gets ordered correctly.
for _, d := range mfst.Layers {
layerDescriptor := &v2LayerDescriptor{
digest: d.Digest,
repo: p.repo,
repoInfo: p.repoInfo,
V2MetadataService: p.V2MetadataService,
src: d,
}
descriptors = append(descriptors, layerDescriptor)
}
configChan := make(chan []byte, 1)
errChan := make(chan error, 1)
var cancel func()
ctx, cancel = context.WithCancel(ctx)
// Pull the image config
go func() {
configJSON, err := p.pullSchema2ImageConfig(ctx, target.Digest)
if err != nil {
errChan <- ImageConfigPullError{Err: err}
cancel()
return
}
configChan <- configJSON
}()
var (
configJSON []byte // raw serialized image config
unmarshalledConfig image.Image // deserialized image config
downloadRootFS image.RootFS // rootFS to use for registering layers.
)
// https://github.com/docker/docker/issues/24766 - Err on the side of caution,
// explicitly blocking images intended for linux from the Windows daemon
if runtime.GOOS == "windows" && unmarshalledConfig.OS == "linux" {
return "", "", fmt.Errorf("image operating system %q cannot be used on this platform", unmarshalledConfig.OS)
}
downloadRootFS = *image.NewRootFS()
rootFS, release, err := p.config.DownloadManager.Download(ctx, downloadRootFS, descriptors, p.config.ProgressOutput)
if err != nil {
if configJSON != nil {
// Already received the config
return "", "", err
}
select {
case err = <-errChan:
return "", "", err
default:
cancel()
select {
case <-configChan:
case <-errChan:
}
return "", "", err
}
}
defer release()
if configJSON == nil {
configJSON, unmarshalledConfig, err = receiveConfig(configChan, errChan)
if err != nil {
return "", "", err
}
}
// The DiffIDs returned in rootFS MUST match those in the config.
// Otherwise the image config could be referencing layers that aren't
// included in the manifest.
if len(rootFS.DiffIDs) != len(unmarshalledConfig.RootFS.DiffIDs) {
return "", "", errRootFSMismatch
}
for i := range rootFS.DiffIDs {
if rootFS.DiffIDs[i] != unmarshalledConfig.RootFS.DiffIDs[i] {
return "", "", errRootFSMismatch
}
}
imageID, err = p.config.ImageStore.Create(configJSON)
if err != nil {
return "", "", err
}
return imageID, manifestDigest, nil
}
func receiveConfig(configChan <-chan []byte, errChan <-chan error) ([]byte, image.Image, error) {
select {
case configJSON := <-configChan:
var unmarshalledConfig image.Image
if err := json.Unmarshal(configJSON, &unmarshalledConfig); err != nil {
return nil, image.Image{}, err
}
return configJSON, unmarshalledConfig, nil
case err := <-errChan:
return nil, image.Image{}, err
// Don't need a case for ctx.Done in the select because cancellation
// will trigger an error in p.pullSchema2ImageConfig.
}
}
// pullManifestList handles "manifest lists" which point to various
// platform-specifc manifests.
func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mfstList *manifestlist.DeserializedManifestList) (imageID image.ID, manifestListDigest digest.Digest, err error) {
manifestListDigest, err = schema2ManifestDigest(ref, mfstList)
if err != nil {
return "", "", err
}
var manifestDigest digest.Digest
for _, manifestDescriptor := range mfstList.Manifests {
// TODO(aaronl): The manifest list spec supports optional
// "features" and "variant" fields. These are not yet used.
// Once they are, their values should be interpreted here.
if manifestDescriptor.Platform.Architecture == runtime.GOARCH && manifestDescriptor.Platform.OS == runtime.GOOS {
manifestDigest = manifestDescriptor.Digest
break
}
}
if manifestDigest == "" {
return "", "", errors.New("no supported platform found in manifest list")
}
manSvc, err := p.repo.Manifests(ctx)
if err != nil {
return "", "", err
}
manifest, err := manSvc.Get(ctx, manifestDigest)
if err != nil {
return "", "", err
}
manifestRef, err := reference.WithDigest(ref, manifestDigest)
if err != nil {
return "", "", err
}
switch v := manifest.(type) {
case *schema1.SignedManifest:
imageID, _, err = p.pullSchema1(ctx, manifestRef, v)
if err != nil {
return "", "", err
}
case *schema2.DeserializedManifest:
imageID, _, err = p.pullSchema2(ctx, manifestRef, v)
if err != nil {
return "", "", err
}
default:
return "", "", errors.New("unsupported manifest format")
}
return imageID, manifestListDigest, err
}
func (p *v2Puller) pullSchema2ImageConfig(ctx context.Context, dgst digest.Digest) (configJSON []byte, err error) {
blobs := p.repo.Blobs(ctx)
configJSON, err = blobs.Get(ctx, dgst)
if err != nil {
return nil, err
}
// Verify image config digest
verifier, err := digest.NewDigestVerifier(dgst)
if err != nil {
return nil, err
}
if _, err := verifier.Write(configJSON); err != nil {
return nil, err
}
if !verifier.Verified() {
err := fmt.Errorf("image config verification failed for digest %s", dgst)
logrus.Error(err)
return nil, err
}
return configJSON, nil
}
// schema2ManifestDigest computes the manifest digest, and, if pulling by
// digest, ensures that it matches the requested digest.
func schema2ManifestDigest(ref reference.Named, mfst distribution.Manifest) (digest.Digest, error) {
_, canonical, err := mfst.Payload()
if err != nil {
return "", err
}
// If pull by digest, then verify the manifest digest.
if digested, isDigested := ref.(reference.Canonical); isDigested {
verifier, err := digest.NewDigestVerifier(digested.Digest())
if err != nil {
return "", err
}
if _, err := verifier.Write(canonical); err != nil {
return "", err
}
if !verifier.Verified() {
err := fmt.Errorf("manifest verification failed for digest %s", digested.Digest())
logrus.Error(err)
return "", err
}
return digested.Digest(), nil
}
return digest.FromBytes(canonical), nil
}
// allowV1Fallback checks if the error is a possible reason to fallback to v1
// (even if confirmedV2 has been set already), and if so, wraps the error in
// a fallbackError with confirmedV2 set to false. Otherwise, it returns the
// error unmodified.
func allowV1Fallback(err error) error {
switch v := err.(type) {
case errcode.Errors:
if len(v) != 0 {
if v0, ok := v[0].(errcode.Error); ok && shouldV2Fallback(v0) {
return fallbackError{
err: err,
confirmedV2: false,
transportOK: true,
}
}
}
case errcode.Error:
if shouldV2Fallback(v) {
return fallbackError{
err: err,
confirmedV2: false,
transportOK: true,
}
}
case *url.Error:
if v.Err == auth.ErrNoBasicAuthCredentials {
return fallbackError{err: err, confirmedV2: false}
}
}
return err
}
func verifySchema1Manifest(signedManifest *schema1.SignedManifest, ref reference.Named) (m *schema1.Manifest, err error) {
// If pull by digest, then verify the manifest digest. NOTE: It is
// important to do this first, before any other content validation. If the
// digest cannot be verified, don't even bother with those other things.
if digested, isCanonical := ref.(reference.Canonical); isCanonical {
verifier, err := digest.NewDigestVerifier(digested.Digest())
if err != nil {
return nil, err
}
if _, err := verifier.Write(signedManifest.Canonical); err != nil {
return nil, err
}
if !verifier.Verified() {
err := fmt.Errorf("image verification failed for digest %s", digested.Digest())
logrus.Error(err)
return nil, err
}
}
m = &signedManifest.Manifest
if m.SchemaVersion != 1 {
return nil, fmt.Errorf("unsupported schema version %d for %q", m.SchemaVersion, ref.String())
}
if len(m.FSLayers) != len(m.History) {
return nil, fmt.Errorf("length of history not equal to number of layers for %q", ref.String())
}
if len(m.FSLayers) == 0 {
return nil, fmt.Errorf("no FSLayers in manifest for %q", ref.String())
}
return m, nil
}
// fixManifestLayers removes repeated layers from the manifest and checks the
// correctness of the parent chain.
func fixManifestLayers(m *schema1.Manifest) error {
imgs := make([]*image.V1Image, len(m.FSLayers))
for i := range m.FSLayers {
img := &image.V1Image{}
if err := json.Unmarshal([]byte(m.History[i].V1Compatibility), img); err != nil {
return err
}
imgs[i] = img
if err := v1.ValidateID(img.ID); err != nil {
return err
}
}
if imgs[len(imgs)-1].Parent != "" && runtime.GOOS != "windows" {
// Windows base layer can point to a base layer parent that is not in manifest.
return errors.New("Invalid parent ID in the base layer of the image.")
}
// check general duplicates to error instead of a deadlock
idmap := make(map[string]struct{})
var lastID string
for _, img := range imgs {
// skip IDs that appear after each other, we handle those later
if _, exists := idmap[img.ID]; img.ID != lastID && exists {
return fmt.Errorf("ID %+v appears multiple times in manifest", img.ID)
}
lastID = img.ID
idmap[lastID] = struct{}{}
}
// backwards loop so that we keep the remaining indexes after removing items
for i := len(imgs) - 2; i >= 0; i-- {
if imgs[i].ID == imgs[i+1].ID { // repeated ID. remove and continue
m.FSLayers = append(m.FSLayers[:i], m.FSLayers[i+1:]...)
m.History = append(m.History[:i], m.History[i+1:]...)
} else if imgs[i].Parent != imgs[i+1].ID {
return fmt.Errorf("Invalid parent ID. Expected %v, got %v.", imgs[i+1].ID, imgs[i].Parent)
}
}
return nil
}
func createDownloadFile() (*os.File, error) {
return ioutil.TempFile("", "GetImageBlob")
}