@@ -15,12 +15,17 @@ import (

 	"strings"

 	"testing"

+	"github.com/containerd/containerd/images"

+	"github.com/containerd/containerd/remotes/docker"

 	"github.com/docker/docker/api/types"

+	"github.com/docker/docker/pkg/jsonmessage"

 	"github.com/docker/docker/testutil/daemon"

 	"github.com/docker/docker/testutil/fixtures/plugin"

 	"github.com/docker/docker/testutil/registry"

 	"github.com/docker/docker/testutil/request"

+	v1 "github.com/opencontainers/image-spec/specs-go/v1"

 	"gotest.tools/v3/assert"

+	"gotest.tools/v3/assert/cmp"

 	is "gotest.tools/v3/assert/cmp"

 	"gotest.tools/v3/skip"

 )

@@ -223,3 +228,61 @@ func TestPluginsWithRuntimes(t *testing.T) {

 		assert.NilError(t, err)

 	})

 }

+

+func TestPluginBackCompatMediaTypes(t *testing.T) {

+	skip.If(t, testEnv.IsRemoteDaemon, "cannot run daemon when remote daemon")

+	skip.If(t, testEnv.OSType == "windows")

+	skip.If(t, testEnv.IsRootless, "Rootless has a different view of localhost (needed for test registry access)")

+

+	defer setupTest(t)()

+

+	reg := registry.NewV2(t)

+	defer reg.Close()

+	reg.WaitReady(t)

+

+	repo := path.Join(registry.DefaultURL, strings.ToLower(t.Name())+":latest")

+

+	client := testEnv.APIClient()

+

+	ctx := context.Background()

+	assert.NilError(t, plugin.Create(ctx, client, repo))

+

+	rdr, err := client.PluginPush(ctx, repo, "")

+	assert.NilError(t, err)

+	defer rdr.Close()

+

+	buf := &strings.Builder{}

+	assert.NilError(t, jsonmessage.DisplayJSONMessagesStream(rdr, buf, 0, false, nil), buf)

+

+	// Use custom header here because older versions of the registry do not

+	// parse the accept header correctly and does not like the accept header

+	// that the default resolver code uses. "Older registries" here would be

+	// like the one currently included in the test suite.

+	headers := http.Header{}

+	headers.Add("Accept", images.MediaTypeDockerSchema2Manifest)

+

+	resolver := docker.NewResolver(docker.ResolverOptions{

+		Headers: headers,

+	})

+	assert.NilError(t, err)

+

+	n, desc, err := resolver.Resolve(ctx, repo)

+	assert.NilError(t, err, repo)

+

+	fetcher, err := resolver.Fetcher(ctx, n)

+	assert.NilError(t, err)

+

+	rdr, err = fetcher.Fetch(ctx, desc)

+	assert.NilError(t, err)

+	defer rdr.Close()

+

+	type manifest struct {

+		MediaType string

+		v1.Manifest

+	}

+	var m manifest

+	assert.NilError(t, json.NewDecoder(rdr).Decode(&m))

+	assert.Check(t, cmp.Equal(m.MediaType, images.MediaTypeDockerSchema2Manifest))

+	assert.Check(t, cmp.Len(m.Layers, 1))

+	assert.Check(t, cmp.Equal(m.Layers[0].MediaType, images.MediaTypeDockerSchema2LayerGzip))

+}

@@ -492,7 +492,7 @@ func buildManifest(ctx context.Context, s content.Manager, config digest.Digest,

 			return m, errors.Wrapf(err, "error fetching info for content digest %s", l)

 		}

 		m.Layers = append(m.Layers, specs.Descriptor{

-			MediaType: specs.MediaTypeImageLayerGzip, // TODO: This is assuming everything is a gzip compressed layer, but that may not be true.

+			MediaType: images.MediaTypeDockerSchema2LayerGzip, // TODO: This is assuming everything is a gzip compressed layer, but that may not be true.

 			Digest:    l,

 			Size:      info.Size,

 		})