Add platform filtering on children handler

Fixes pulling of multi-arch images by limiting the expansion
of the index by filtering to the current default platform.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

client.go

@@ -23,6 +23,7 @@ import (
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/images"
+	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/containerd/plugin"
 	"github.com/containerd/containerd/reference"
 	"github.com/containerd/containerd/remotes"
@@ -226,7 +227,7 @@ func (c *Client) Pull(ctx context.Context, ref string, opts ...RemoteOpts) (Imag
 	} else {
 		handler = images.Handlers(append(pullCtx.BaseHandlers,
 			remotes.FetchHandler(store, fetcher),
-			images.ChildrenHandler(store))...,
+			images.ChildrenHandler(store, platforms.Default()))...,
 		)
 	}
 
@@ -307,7 +308,7 @@ func (c *Client) Push(ctx context.Context, ref string, desc ocispec.Descriptor,
 	pushHandler := remotes.PushHandler(cs, pusher)
 
 	handlers := append(pushCtx.BaseHandlers,
-		images.ChildrenHandler(cs),
+		images.ChildrenHandler(cs, platforms.Default()),
 		filterHandler,
 		pushHandler,
 	)

cmd/ctr/images.go

@@ -58,7 +58,7 @@ var imagesListCommand = cli.Command{
 		tw := tabwriter.NewWriter(os.Stdout, 1, 8, 1, ' ', 0)
 		fmt.Fprintln(tw, "REF\tTYPE\tDIGEST\tSIZE\tPLATFORM\tLABELS\t")
 		for _, image := range imageList {
-			size, err := image.Size(ctx, cs)
+			size, err := image.Size(ctx, cs, platforms.Default())
 			if err != nil {
 				log.G(ctx).WithError(err).Errorf("failed calculating size for image %s", image.Name)
 			}

export.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/images"
+	"github.com/containerd/containerd/platforms"
 	ocispecs "github.com/opencontainers/image-spec/specs-go"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
@@ -32,7 +33,7 @@ func (c *Client) exportToOCITar(ctx context.Context, desc ocispec.Descriptor, wr
 	}
 
 	handlers := images.Handlers(
-		images.ChildrenHandler(cs),
+		images.ChildrenHandler(cs, platforms.Default()),
 		images.HandlerFunc(exportHandler),
 	)
 

image.go

@@ -50,7 +50,7 @@ func (i *image) RootFS(ctx context.Context) ([]digest.Digest, error) {
 
 func (i *image) Size(ctx context.Context) (int64, error) {
 	provider := i.client.ContentStore()
-	return i.i.Size(ctx, provider)
+	return i.i.Size(ctx, provider, platforms.Default())
 }
 
 func (i *image) Config(ctx context.Context) (ocispec.Descriptor, error) {

images/handlers.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/log"
+	"github.com/containerd/containerd/platforms"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"golang.org/x/sync/errgroup"
@@ -127,7 +128,7 @@ func Dispatch(ctx context.Context, handler Handler, descs ...ocispec.Descriptor)
 //
 // One can also replace this with another implementation to allow descending of
 // arbitrary types.
-func ChildrenHandler(provider content.Provider) HandlerFunc {
+func ChildrenHandler(provider content.Provider, platform string) HandlerFunc {
 	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
 		var descs []ocispec.Descriptor
 		switch desc.MediaType {
@@ -157,7 +158,21 @@ func ChildrenHandler(provider content.Provider) HandlerFunc {
 				return nil, err
 			}
 
+			if platform != "" {
+				matcher, err := platforms.Parse(platform)
+				if err != nil {
+					return nil, err
+				}
+
+				for _, d := range index.Manifests {
+					if d.Platform == nil || matcher.Match(*d.Platform) {
+						descs = append(descs, d)
+					}
+				}
+			} else {
 				descs = append(descs, index.Manifests...)
+			}
+
 		case MediaTypeDockerSchema2Layer, MediaTypeDockerSchema2LayerGzip,
 			MediaTypeDockerSchema2Config, ocispec.MediaTypeImageConfig,
 			ocispec.MediaTypeImageLayer, ocispec.MediaTypeImageLayerGzip:

images/image.go

@@ -58,7 +58,7 @@ func (image *Image) RootFS(ctx context.Context, provider content.Provider, platf
 }
 
 // Size returns the total size of an image's packed resources.
-func (image *Image) Size(ctx context.Context, provider content.Provider) (int64, error) {
+func (image *Image) Size(ctx context.Context, provider content.Provider, platform string) (int64, error) {
 	var size int64
 	return size, Walk(ctx, Handlers(HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
 		if desc.Size < 0 {
@@ -66,7 +66,7 @@ func (image *Image) Size(ctx context.Context, provider content.Provider) (int64,
 		}
 		size += desc.Size
 		return nil, nil
-	}), ChildrenHandler(provider)), image.Target)
+	}), ChildrenHandler(provider, platform)), image.Target)
 }
 
 func Manifest(ctx context.Context, provider content.Provider, image ocispec.Descriptor, platform string) (ocispec.Manifest, error) {
@@ -196,7 +196,7 @@ func Platforms(ctx context.Context, provider content.Provider, image ocispec.Des
 				platforms.Normalize(ocispec.Platform{OS: image.OS, Architecture: image.Architecture}))
 		}
 		return nil, nil
-	}), ChildrenHandler(provider)), image)
+	}), ChildrenHandler(provider, "")), image)
 }
 
 // RootFS returns the unpacked diffids that make up and images rootfs.