c8d/push: Retry with a single manifest if no platform requested

When no platform was requested and pushing whole index failed, fallback
to pushing a platform-specific manifest with a best candidate (if it's
possible to choose one).

Signed-off-by: Paweł Gronowski <[email protected]>

daemon/containerd/image_push.go

@@ -104,9 +104,12 @@ func (i *ImageService) pushRef(ctx context.Context, targetRef reference.Named, p
  return errdefs.NotFound(fmt.Errorf("tag does not exist: %s", reference.FamiliarString(targetRef)))
  }
 
- target, err := i.getPushDescriptor(ctx, img, platform)
- if err != nil {
- return err
+ target := img.Target
+ if platform != nil {
+ target, err = i.getPushDescriptor(ctx, img, platform)
+ if err != nil {
+ return err
+ }
  }
 
  store := i.content
@@ -163,8 +166,19 @@ func (i *ImageService) pushRef(ctx context.Context, targetRef reference.Named, p
  }
 
  err = remotes.PushContent(ctx, pusher, target, store, limiter, platforms.All, handlerWrapper)
- if err != nil {
- if containerdimages.IsIndexType(target.MediaType) && cerrdefs.IsNotFound(err) {
+ if err != nil && containerdimages.IsIndexType(target.MediaType) {
+ if cerrdefs.IsNotFound(err) && platform == nil {
+ // If push failed because of a missing content, no specific platform was requested
+ // and the target is an index, select a platform-specific manifest to push instead.
+ target, err = i.getPushDescriptor(ctx, img, nil)
+ if err != nil {
+ return err
+ }
+
+ err = remotes.PushContent(ctx, pusher, target, store, limiter, platforms.All, handlerWrapper)
+ }
+
+ if err != nil && cerrdefs.IsNotFound(err) {
  return errdefs.NotFound(fmt.Errorf(
  "missing content: %w\n"+
  "Note: You're trying to push a manifest list/index which "+