@@ -1,11 +1,17 @@

 package httputils

 import (

+	"encoding/json"

+	"fmt"

 	"io"

 	"mime"

 	"net/http"

+	"runtime"

 	"strings"

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

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

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

 	"github.com/pkg/errors"

 	"github.com/sirupsen/logrus"

 	"golang.org/x/net/context"

@@ -109,3 +115,27 @@ func matchesContentType(contentType, expectedType string) bool {

 	}

 	return err == nil && mimetype == expectedType

 }

+

+// GetRequestedPlatform extracts an optional platform structure from an HTTP request header

+func GetRequestedPlatform(ctx context.Context, r *http.Request) (*specs.Platform, error) {

+	platform := &specs.Platform{}

+	version := VersionFromContext(ctx)

+	if versions.GreaterThanOrEqualTo(version, "1.32") {

+		requestedPlatform := r.Header.Get("X-Requested-Platform")

+		if requestedPlatform != "" {

+			if err := json.Unmarshal([]byte(requestedPlatform), platform); err != nil {

+				return nil, fmt.Errorf("invalid X-Requested-Platform header: %s", err)

+			}

+		}

+		if err := system.ValidatePlatform(platform); err != nil {

+			return nil, err

+		}

+	}

+	if platform.OS == "" {

+		platform.OS = runtime.GOOS

+	}

+	if platform.Architecture == "" {

+		platform.Architecture = runtime.GOARCH

+	}

+	return platform, nil

+}

@@ -87,6 +87,12 @@ func newImageBuildOptions(ctx context.Context, r *http.Request) (*types.ImageBui

 		return nil, validationError{fmt.Errorf("The daemon on this platform does not support setting security options on build")}

 	}

+	platform, err := httputils.GetRequestedPlatform(ctx, r)

+	if err != nil {

+		return nil, err

+	}

+	options.Platform = *platform

+

 	var buildUlimits = []*units.Ulimit{}

 	ulimitsJSON := r.FormValue("ulimits")

 	if ulimitsJSON != "" {

@@ -5,7 +5,6 @@ import (

 	"encoding/json"

 	"io"

 	"net/http"

-	"runtime"

 	"strconv"

 	"strings"

@@ -17,8 +16,8 @@ import (

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

 	"github.com/docker/docker/pkg/ioutils"

 	"github.com/docker/docker/pkg/streamformatter"

-	"github.com/docker/docker/pkg/system"

 	"github.com/docker/docker/registry"

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

 	"github.com/pkg/errors"

 	"golang.org/x/net/context"

 )

@@ -76,78 +75,46 @@ func (s *imageRouter) postImagesCreate(ctx context.Context, w http.ResponseWrite

 	}

 	var (

-		image   = r.Form.Get("fromImage")

-		repo    = r.Form.Get("repo")

-		tag     = r.Form.Get("tag")

-		message = r.Form.Get("message")

-		err     error

-		output  = ioutils.NewWriteFlusher(w)

+		image    = r.Form.Get("fromImage")

+		repo     = r.Form.Get("repo")

+		tag      = r.Form.Get("tag")

+		message  = r.Form.Get("message")

+		err      error

+		output   = ioutils.NewWriteFlusher(w)

+		platform = &specs.Platform{}

 	)

 	defer output.Close()

-	// TODO @jhowardmsft LCOW Support: Eventually we will need an API change

-	// so that platform comes from (for example) r.Form.Get("platform"). For

-	// the initial implementation, we assume that the platform is the

-	// runtime OS of the host. It will also need a validation function such

-	// as below which should be called after getting it from the API.

-	//

-	// Ensures the requested platform is valid and normalized

-	//func validatePlatform(req string) (string, error) {

-	//	req = strings.ToLower(req)

-	//	if req == "" {

-	//		req = runtime.GOOS // default to host platform

-	//	}

-	//	valid := []string{runtime.GOOS}

-	//

-	//	if system.LCOWSupported() {

-	//		valid = append(valid, "linux")

-	//	}

-	//

-	//	for _, item := range valid {

-	//		if req == item {

-	//			return req, nil

-	//		}

-	//	}

-	//	return "", fmt.Errorf("invalid platform requested: %s", req)

-	//}

-	//

-	// And in the call-site:

-	//	if platform, err = validatePlatform(platform); err != nil {

-	//		return err

-	//	}

-	platform := runtime.GOOS

-	if system.LCOWSupported() {

-		platform = "linux"

-	}

-

 	w.Header().Set("Content-Type", "application/json")

-	if image != "" { //pull

-		metaHeaders := map[string][]string{}

-		for k, v := range r.Header {

-			if strings.HasPrefix(k, "X-Meta-") {

-				metaHeaders[k] = v

+	platform, err = httputils.GetRequestedPlatform(ctx, r)

+	if err == nil {

+		if image != "" { //pull

+			metaHeaders := map[string][]string{}

+			for k, v := range r.Header {

+				if strings.HasPrefix(k, "X-Meta-") {

+					metaHeaders[k] = v

+				}

 			}

-		}

-		authEncoded := r.Header.Get("X-Registry-Auth")

-		authConfig := &types.AuthConfig{}

-		if authEncoded != "" {

-			authJSON := base64.NewDecoder(base64.URLEncoding, strings.NewReader(authEncoded))

-			if err := json.NewDecoder(authJSON).Decode(authConfig); err != nil {

-				// for a pull it is not an error if no auth was given

-				// to increase compatibility with the existing api it is defaulting to be empty

-				authConfig = &types.AuthConfig{}

+			authEncoded := r.Header.Get("X-Registry-Auth")

+			authConfig := &types.AuthConfig{}

+			if authEncoded != "" {

+				authJSON := base64.NewDecoder(base64.URLEncoding, strings.NewReader(authEncoded))

+				if err := json.NewDecoder(authJSON).Decode(authConfig); err != nil {

+					// for a pull it is not an error if no auth was given

+					// to increase compatibility with the existing api it is defaulting to be empty

+					authConfig = &types.AuthConfig{}

+				}

 			}

+			err = s.backend.PullImage(ctx, image, tag, platform.OS, metaHeaders, authConfig, output)

+		} else { //import

+			src := r.Form.Get("fromSrc")

+			// 'err' MUST NOT be defined within this block, we need any error

+			// generated from the download to be available to the output

+			// stream processing below

+			err = s.backend.ImportImage(src, repo, platform.OS, tag, message, r.Body, output, r.Form["changes"])

 		}

-

-		err = s.backend.PullImage(ctx, image, tag, platform, metaHeaders, authConfig, output)

-	} else { //import

-		src := r.Form.Get("fromSrc")

-		// 'err' MUST NOT be defined within this block, we need any error

-		// generated from the download to be available to the output

-		// stream processing below

-		err = s.backend.ImportImage(src, repo, platform, tag, message, r.Body, output, r.Form["changes"])

 	}

 	if err != nil {

 		if !output.Flushed() {

@@ -6181,6 +6181,19 @@ paths:

             Only the registry domain name (and port if not the default 443) are required. However, for legacy reasons, the Docker Hub registry must be specified with both a `https://` prefix and a `/v1/` suffix even though Docker will prefer to use the v2 registry API.

           type: "string"

+        - name: "X-Requested-Platform"

+          in: "header"

+          description: |

+            This is a JSON object representing an OCI image-spec `Platform` object. It is used to request a platform in the case that the engine supports multiple platforms. For example:

+

+            ```

+            {

+              "architecture": "amd64",

+              "os": "linux"

+            }

+            ```

+          type: "string"

+          default: ""

       responses:

         200:

           description: "no error"

@@ -6262,6 +6275,19 @@ paths:

           in: "header"

           description: "A base64-encoded auth configuration. [See the authentication section for details.](#section/Authentication)"

           type: "string"

+        - name: "X-Requested-Platform"

+          in: "header"

+          description: |

+            This is a JSON object representing an OCI image-spec `Platform` object. It is used to request a platform in the case that the engine supports multiple platforms. For example:

+

+            ```

+            {

+              "architecture": "amd64",

+              "os": "linux"

+            }

+            ```

+          type: "string"

+          default: ""

       tags: ["Image"]

   /images/{name}/json:

     get:

@@ -40,5 +40,5 @@ type GetImageAndLayerOptions struct {

 	PullOption PullOption

 	AuthConfig map[string]types.AuthConfig

 	Output     io.Writer

-	Platform   string

+	OS         string

 }

@@ -8,6 +8,7 @@ import (

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

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

 	units "github.com/docker/go-units"

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

 )

 // CheckpointCreateOptions holds parameters to create a checkpoint from a container

@@ -179,10 +180,7 @@ type ImageBuildOptions struct {

 	ExtraHosts  []string // List of extra hosts

 	Target      string

 	SessionID   string

-

-	// TODO @jhowardmsft LCOW Support: This will require extending to include

-	// `Platform string`, but is omitted for now as it's hard-coded temporarily

-	// to avoid API changes.

+	Platform    specs.Platform

 }

 // ImageBuildResponse holds information

@@ -195,7 +193,8 @@ type ImageBuildResponse struct {

 // ImageCreateOptions holds information to create images.

 type ImageCreateOptions struct {

-	RegistryAuth string // RegistryAuth is the base64 encoded credentials for the registry

+	RegistryAuth string         // RegistryAuth is the base64 encoded credentials for the registry.

+	Platform     specs.Platform // Platform is the target platform of the image if it needs to be pulled from the registry.

 }

 // ImageImportSource holds source information for ImageImport

@@ -229,6 +228,7 @@ type ImagePullOptions struct {

 	All           bool

 	RegistryAuth  string // RegistryAuth is the base64 encoded credentials for the registry

 	PrivilegeFunc RequestPrivilegeFunc

+	Platform      specs.Platform

 }

 // RequestPrivilegeFunc is a function interface that

@@ -16,7 +16,6 @@ type ContainerCreateConfig struct {

 	HostConfig       *container.HostConfig

 	NetworkingConfig *network.NetworkingConfig

 	AdjustCPUShares  bool

-	Platform         string

 }

 // ContainerRmConfig holds arguments for the container remove

@@ -327,7 +327,7 @@ type ContainerJSONBase struct {

 	Name            string

 	RestartCount    int

 	Driver          string

-	Platform        string

+	OS              string

 	MountLabel      string

 	ProcessLabel    string

 	AppArmorProfile string

@@ -95,6 +95,7 @@ type Image interface {

 	ImageID() string

 	RunConfig() *container.Config

 	MarshalJSON() ([]byte, error)

+	OperatingSystem() string

 }

 // ReleaseableLayer is an image layer that can be mounted and released

@@ -20,7 +20,6 @@ import (

 	"github.com/docker/docker/pkg/idtools"

 	"github.com/docker/docker/pkg/streamformatter"

 	"github.com/docker/docker/pkg/stringid"

-	"github.com/docker/docker/pkg/system"

 	"github.com/moby/buildkit/session"

 	"github.com/pkg/errors"

 	"github.com/sirupsen/logrus"

@@ -93,15 +92,6 @@ func (bm *BuildManager) Build(ctx context.Context, config backend.BuildConfig) (

 		}

 	}()

-	// TODO @jhowardmsft LCOW support - this will require rework to allow both linux and Windows simultaneously.

-	// This is an interim solution to hardcode to linux if LCOW is turned on.

-	if dockerfile.Platform == "" {

-		dockerfile.Platform = runtime.GOOS

-		if dockerfile.Platform == "windows" && system.LCOWSupported() {

-			dockerfile.Platform = "linux"

-		}

-	}

-

 	ctx, cancel := context.WithCancel(ctx)

 	defer cancel()

@@ -111,16 +101,26 @@ func (bm *BuildManager) Build(ctx context.Context, config backend.BuildConfig) (

 		source = src

 	}

+	os := runtime.GOOS

+	if dockerfile.OS != "" {

+		if config.Options.Platform.OS != "" && config.Options.Platform.OS != dockerfile.OS {

+			return nil, fmt.Errorf("invalid platform")

+		}

+		os = dockerfile.OS

+	} else if config.Options.Platform.OS != "" {

+		os = config.Options.Platform.OS

+	}

+	config.Options.Platform.OS = os

+	dockerfile.OS = os

+

 	builderOptions := builderOptions{

 		Options:        config.Options,

 		ProgressWriter: config.ProgressWriter,

 		Backend:        bm.backend,

 		PathCache:      bm.pathCache,

 		IDMappings:     bm.idMappings,

-		Platform:       dockerfile.Platform,

 	}

-

-	return newBuilder(ctx, builderOptions).build(source, dockerfile)

+	return newBuilder(ctx, builderOptions, os).build(source, dockerfile)

 }

 func (bm *BuildManager) initializeClientSession(ctx context.Context, cancel func(), options *types.ImageBuildOptions) (builder.Source, error) {

@@ -163,7 +163,6 @@ type builderOptions struct {

 	ProgressWriter backend.ProgressWriter

 	PathCache      pathCache

 	IDMappings     *idtools.IDMappings

-	Platform       string

 }

 // Builder is a Dockerfile builder

@@ -185,32 +184,15 @@ type Builder struct {

 	pathCache        pathCache

 	containerManager *containerManager

 	imageProber      ImageProber

-

-	// TODO @jhowardmft LCOW Support. This will be moved to options at a later

-	// stage, however that cannot be done now as it affects the public API

-	// if it were.

-	platform string

 }

 // newBuilder creates a new Dockerfile builder from an optional dockerfile and a Options.

-// TODO @jhowardmsft LCOW support: Eventually platform can be moved into the builder

-// options, however, that would be an API change as it shares types.ImageBuildOptions.

-func newBuilder(clientCtx context.Context, options builderOptions) *Builder {

+func newBuilder(clientCtx context.Context, options builderOptions, os string) *Builder {

 	config := options.Options

 	if config == nil {

 		config = new(types.ImageBuildOptions)

 	}

-	// @jhowardmsft LCOW Support. For the time being, this is interim. Eventually

-	// will be moved to types.ImageBuildOptions, but it can't for now as that would

-	// be an API change.

-	if options.Platform == "" {

-		options.Platform = runtime.GOOS

-	}

-	if options.Platform == "windows" && system.LCOWSupported() {

-		options.Platform = "linux"

-	}

-

 	b := &Builder{

 		clientCtx:        clientCtx,

 		options:          config,

@@ -222,9 +204,8 @@ func newBuilder(clientCtx context.Context, options builderOptions) *Builder {

 		idMappings:       options.IDMappings,

 		imageSources:     newImageSources(clientCtx, options),

 		pathCache:        options.PathCache,

-		imageProber:      newImageProber(options.Backend, config.CacheFrom, options.Platform, config.NoCache),

+		imageProber:      newImageProber(options.Backend, config.CacheFrom, os, config.NoCache),

 		containerManager: newContainerManager(options.Backend),

-		platform:         options.Platform,

 	}

 	return b

@@ -382,25 +363,19 @@ func BuildFromConfig(config *container.Config, changes []string) (*container.Con

 		return config, nil

 	}

-	b := newBuilder(context.Background(), builderOptions{

-		Options: &types.ImageBuildOptions{NoCache: true},

-	})

-

 	dockerfile, err := parser.Parse(bytes.NewBufferString(strings.Join(changes, "\n")))

 	if err != nil {

 		return nil, validationError{err}

 	}

-	// TODO @jhowardmsft LCOW support. For now, if LCOW enabled, switch to linux.

-	// Also explicitly set the platform. Ultimately this will be in the builder

-	// options, but we can't do that yet as it would change the API.

-	if dockerfile.Platform == "" {

-		dockerfile.Platform = runtime.GOOS

+	os := runtime.GOOS

+	if dockerfile.OS != "" {

+		os = dockerfile.OS

 	}

-	if dockerfile.Platform == "windows" && system.LCOWSupported() {

-		dockerfile.Platform = "linux"

-	}

-	b.platform = dockerfile.Platform

+

+	b := newBuilder(context.Background(), builderOptions{

+		Options: &types.ImageBuildOptions{NoCache: true},

+	}, os)

 	// ensure that the commands are valid

 	for _, n := range dockerfile.AST.Children {

@@ -2,6 +2,6 @@

 package dockerfile

-func defaultShellForPlatform(platform string) []string {

+func defaultShellForOS(os string) []string {

 	return []string{"/bin/sh", "-c"}

 }

@@ -1,7 +1,7 @@

 package dockerfile

-func defaultShellForPlatform(platform string) []string {

-	if platform == "linux" {

+func defaultShellForOS(os string) []string {

+	if os == "linux" {

 		return []string{"/bin/sh", "-c"}

 	}

 	return []string{"cmd", "/S", "/C"}

@@ -32,7 +32,6 @@ func (c *containerManager) Create(runConfig *container.Config, hostConfig *conta

 	container, err := c.backend.ContainerCreate(types.ContainerCreateConfig{

 		Config:     runConfig,

 		HostConfig: hostConfig,

-		Platform:   platform,

 	})

 	if err != nil {

 		return container, err

@@ -82,7 +82,7 @@ func copierFromDispatchRequest(req dispatchRequest, download sourceDownloader, i

 		pathCache:   req.builder.pathCache,

 		download:    download,

 		imageSource: imageSource,

-		platform:    req.builder.platform,

+		platform:    req.builder.options.Platform.OS,

 	}

 }

@@ -220,12 +220,22 @@ func (d *dispatchRequest) getImageOrStage(name string) (builder.Image, error) {

 	// Windows cannot support a container with no base image unless it is LCOW.

 	if name == api.NoBaseImageSpecifier {

+		imageImage := &image.Image{}

+		imageImage.OS = runtime.GOOS

 		if runtime.GOOS == "windows" {

-			if d.builder.platform == "windows" || (d.builder.platform != "windows" && !system.LCOWSupported()) {

+			switch d.builder.options.Platform.OS {

+			case "windows":

 				return nil, errors.New("Windows does not support FROM scratch")

+			case "linux":

+				if !system.LCOWSupported() {

+					return nil, errors.New("Linux containers are not supported on this system")

+				}

+				imageImage.OS = "linux"

+			default:

+				return nil, errors.Errorf("operating system %q is not supported", d.builder.options.Platform.OS)

 			}

 		}

-		return scratchImage, nil

+		return builder.Image(imageImage), nil

 	}

 	imageMount, err := d.builder.imageSources.Get(name, localOnly)

 	if err != nil {

@@ -254,7 +264,7 @@ func dispatchOnbuild(d dispatchRequest, c *instructions.OnbuildCommand) error {

 func dispatchWorkdir(d dispatchRequest, c *instructions.WorkdirCommand) error {

 	runConfig := d.state.runConfig

 	var err error

-	runConfig.WorkingDir, err = normalizeWorkdir(d.builder.platform, runConfig.WorkingDir, c.Path)

+	runConfig.WorkingDir, err = normalizeWorkdir(d.builder.options.Platform.OS, runConfig.WorkingDir, c.Path)

 	if err != nil {

 		return err

 	}

@@ -270,7 +280,7 @@ func dispatchWorkdir(d dispatchRequest, c *instructions.WorkdirCommand) error {

 	}

 	comment := "WORKDIR " + runConfig.WorkingDir

-	runConfigWithCommentCmd := copyRunConfig(runConfig, withCmdCommentString(comment, d.builder.platform))

+	runConfigWithCommentCmd := copyRunConfig(runConfig, withCmdCommentString(comment, d.builder.options.Platform.OS))

 	containerID, err := d.builder.probeAndCreate(d.state, runConfigWithCommentCmd)

 	if err != nil || containerID == "" {

 		return err

@@ -303,7 +313,7 @@ func resolveCmdLine(cmd instructions.ShellDependantCmdLine, runConfig *container

 func dispatchRun(d dispatchRequest, c *instructions.RunCommand) error {

 	stateRunConfig := d.state.runConfig

-	cmdFromArgs := resolveCmdLine(c.ShellDependantCmdLine, stateRunConfig, d.builder.platform)

+	cmdFromArgs := resolveCmdLine(c.ShellDependantCmdLine, stateRunConfig, d.builder.options.Platform.OS)

 	buildArgs := d.state.buildArgs.FilterAllowed(stateRunConfig.Env)

 	saveCmd := cmdFromArgs

@@ -380,7 +390,7 @@ func prependEnvOnCmd(buildArgs *buildArgs, buildArgVars []string, cmd strslice.S

 //

 func dispatchCmd(d dispatchRequest, c *instructions.CmdCommand) error {

 	runConfig := d.state.runConfig

-	cmd := resolveCmdLine(c.ShellDependantCmdLine, runConfig, d.builder.platform)

+	cmd := resolveCmdLine(c.ShellDependantCmdLine, runConfig, d.builder.options.Platform.OS)

 	runConfig.Cmd = cmd

 	// set config as already being escaped, this prevents double escaping on windows

 	runConfig.ArgsEscaped = true

@@ -423,7 +433,7 @@ func dispatchHealthcheck(d dispatchRequest, c *instructions.HealthCheckCommand)

 //

 func dispatchEntrypoint(d dispatchRequest, c *instructions.EntrypointCommand) error {

 	runConfig := d.state.runConfig

-	cmd := resolveCmdLine(c.ShellDependantCmdLine, runConfig, d.builder.platform)

+	cmd := resolveCmdLine(c.ShellDependantCmdLine, runConfig, d.builder.options.Platform.OS)

 	runConfig.Entrypoint = cmd

 	if !d.state.cmdSet {

 		runConfig.Cmd = nil

@@ -14,6 +14,7 @@ import (

 	"github.com/docker/docker/builder/dockerfile/instructions"

 	"github.com/docker/docker/pkg/system"

 	"github.com/docker/go-connections/nat"

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

 	"github.com/stretchr/testify/assert"

 	"github.com/stretchr/testify/require"

 )

@@ -22,13 +23,13 @@ func newBuilderWithMockBackend() *Builder {

 	mockBackend := &MockBackend{}

 	ctx := context.Background()

 	b := &Builder{

-		options:       &types.ImageBuildOptions{},

+		options:       &types.ImageBuildOptions{Platform: specs.Platform{OS: runtime.GOOS}},

 		docker:        mockBackend,

 		Stdout:        new(bytes.Buffer),

 		clientCtx:     ctx,

 		disableCommit: true,

 		imageSources: newImageSources(ctx, builderOptions{

-			Options: &types.ImageBuildOptions{},

+			Options: &types.ImageBuildOptions{Platform: specs.Platform{OS: runtime.GOOS}},

 			Backend: mockBackend,

 		}),

 		imageProber:      newImageProber(mockBackend, nil, runtime.GOOS, false),

@@ -118,11 +119,7 @@ func TestFromScratch(t *testing.T) {

 	require.NoError(t, err)

 	assert.True(t, sb.state.hasFromImage())

 	assert.Equal(t, "", sb.state.imageID)

-	// Windows does not set the default path. TODO @jhowardmsft LCOW support. This will need revisiting as we get further into the implementation

 	expected := "PATH=" + system.DefaultPathEnv(runtime.GOOS)

-	if runtime.GOOS == "windows" {

-		expected = ""

-	}

 	assert.Equal(t, []string{expected}, sb.state.runConfig.Env)

 }

@@ -21,7 +21,6 @@ package dockerfile

 import (

 	"reflect"

-	"runtime"

 	"strconv"

 	"strings"

@@ -35,7 +34,7 @@ import (

 func dispatch(d dispatchRequest, cmd instructions.Command) error {

 	if c, ok := cmd.(instructions.PlatformSpecific); ok {

-		err := c.CheckPlatform(d.builder.platform)

+		err := c.CheckPlatform(d.builder.options.Platform.OS)

 		if err != nil {

 			return validationError{err}

 		}

@@ -218,19 +217,15 @@ func (s *dispatchState) beginStage(stageName string, image builder.Image) {

 	s.runConfig.StdinOnce = false

 }

-// Add the default PATH to runConfig.ENV if one exists for the platform and there

+// Add the default PATH to runConfig.ENV if one exists for the operating system and there

 // is no PATH set. Note that Windows containers on Windows won't have one as it's set by HCS

 func (s *dispatchState) setDefaultPath() {

-	// TODO @jhowardmsft LCOW Support - This will need revisiting later

-	platform := runtime.GOOS

-	if system.LCOWSupported() {

-		platform = "linux"

-	}

-	if system.DefaultPathEnv(platform) == "" {

+	defaultPath := system.DefaultPathEnv(s.baseImage.OperatingSystem())

+	if defaultPath == "" {

 		return

 	}

 	envMap := opts.ConvertKVStringsToMap(s.runConfig.Env)

 	if _, ok := envMap["PATH"]; !ok {

-		s.runConfig.Env = append(s.runConfig.Env, "PATH="+system.DefaultPathEnv(platform))

+		s.runConfig.Env = append(s.runConfig.Env, "PATH="+defaultPath)

 	}

 }

@@ -20,8 +20,6 @@ type imageSources struct {

 	getImage  getAndMountFunc

 }

-// TODO @jhowardmsft LCOW Support: Eventually, platform can be moved to options.Options.Platform,

-// and removed from builderOptions, but that can't be done yet as it would affect the API.

 func newImageSources(ctx context.Context, options builderOptions) *imageSources {

 	getAndMount := func(idOrRef string, localOnly bool) (builder.Image, builder.ReleaseableLayer, error) {

 		pullOption := backend.PullOptionNoPull

@@ -36,7 +34,7 @@ func newImageSources(ctx context.Context, options builderOptions) *imageSources

 			PullOption: pullOption,

 			AuthConfig: options.Options.AuthConfigs,

 			Output:     options.ProgressWriter.Output,

-			Platform:   options.Platform,

+			OS:         options.Options.Platform.OS,

 		})

 	}

@@ -83,7 +83,7 @@ func (b *Builder) commit(dispatchState *dispatchState, comment string) error {

 		return errors.New("Please provide a source image with `from` prior to commit")

 	}

-	runConfigWithCommentCmd := copyRunConfig(dispatchState.runConfig, withCmdComment(comment, b.platform))

+	runConfigWithCommentCmd := copyRunConfig(dispatchState.runConfig, withCmdComment(comment, b.options.Platform.OS))

 	hit, err := b.probeCache(dispatchState, runConfigWithCommentCmd)

 	if err != nil || hit {

 		return err

@@ -122,7 +122,7 @@ func (b *Builder) commitContainer(dispatchState *dispatchState, id string, conta

 }

 func (b *Builder) exportImage(state *dispatchState, imageMount *imageMount, runConfig *container.Config) error {

-	newLayer, err := imageMount.Layer().Commit(b.platform)

+	newLayer, err := imageMount.Layer().Commit(b.options.Platform.OS)

 	if err != nil {

 		return err

 	}

@@ -172,7 +172,7 @@ func (b *Builder) performCopy(state *dispatchState, inst copyInstruction) error

 	// TODO: should this have been using origPaths instead of srcHash in the comment?

 	runConfigWithCommentCmd := copyRunConfig(

 		state.runConfig,

-		withCmdCommentString(commentStr, b.platform))

+		withCmdCommentString(commentStr, b.options.Platform.OS))

 	hit, err := b.probeCache(state, runConfigWithCommentCmd)

 	if err != nil || hit {

 		return err

@@ -183,7 +183,7 @@ func (b *Builder) performCopy(state *dispatchState, inst copyInstruction) error

 		return errors.Wrapf(err, "failed to get destination image %q", state.imageID)

 	}

-	destInfo, err := createDestInfo(state.runConfig.WorkingDir, inst, imageMount, b.platform)

+	destInfo, err := createDestInfo(state.runConfig.WorkingDir, inst, imageMount, b.options.Platform.OS)

 	if err != nil {

 		return err

 	}

@@ -437,9 +437,9 @@ func withEntrypointOverride(cmd []string, entrypoint []string) runConfigModifier

 // getShell is a helper function which gets the right shell for prefixing the

 // shell-form of RUN, ENTRYPOINT and CMD instructions

-func getShell(c *container.Config, platform string) []string {

+func getShell(c *container.Config, os string) []string {

 	if 0 == len(c.Shell) {

-		return append([]string{}, defaultShellForPlatform(platform)[:]...)

+		return append([]string{}, defaultShellForOS(os)[:]...)

 	}

 	return append([]string{}, c.Shell[:]...)

 }

@@ -463,13 +463,13 @@ func (b *Builder) probeAndCreate(dispatchState *dispatchState, runConfig *contai

 	}

 	// Set a log config to override any default value set on the daemon

 	hostConfig := &container.HostConfig{LogConfig: defaultLogConfig}

-	container, err := b.containerManager.Create(runConfig, hostConfig, b.platform)

+	container, err := b.containerManager.Create(runConfig, hostConfig, b.options.Platform.OS)

 	return container.ID, err

 }

 func (b *Builder) create(runConfig *container.Config) (string, error) {

 	hostConfig := hostConfigFromOptions(b.options)

-	container, err := b.containerManager.Create(runConfig, hostConfig, b.platform)

+	container, err := b.containerManager.Create(runConfig, hostConfig, b.options.Platform.OS)

 	if err != nil {

 		return "", err

 	}

@@ -103,7 +103,7 @@ func TestCopyRunConfig(t *testing.T) {

 			doc:       "Set the command to a comment",

 			modifiers: []runConfigModifier{withCmdComment("comment", runtime.GOOS)},

 			expected: &container.Config{

-				Cmd: append(defaultShellForPlatform(runtime.GOOS), "#(nop) ", "comment"),

+				Cmd: append(defaultShellForOS(runtime.GOOS), "#(nop) ", "comment"),

 				Env: defaultEnv,

 			},

 		},

@@ -3,6 +3,7 @@ package dockerfile

 import (

 	"encoding/json"

 	"io"

+	"runtime"

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

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

@@ -96,6 +97,10 @@ func (i *mockImage) RunConfig() *container.Config {

 	return i.config

 }

+func (i *mockImage) OperatingSystem() string {

+	return runtime.GOOS

+}

+

 func (i *mockImage) MarshalJSON() ([]byte, error) {

 	type rawImage mockImage

 	return json.Marshal(rawImage(*i))

@@ -91,9 +91,6 @@ var (

 // DefaultEscapeToken is the default escape token

 const DefaultEscapeToken = '\\'

-// defaultPlatformToken is the platform assumed for the build if not explicitly provided

-var defaultPlatformToken = runtime.GOOS

-

 // Directive is the structure used during a build run to hold the state of

 // parsing directives.

 type Directive struct {

@@ -152,8 +149,7 @@ func (d *Directive) possibleParserDirective(line string) error {

 		}

 	}

-	// TODO @jhowardmsft LCOW Support: Eventually this check can be removed,

-	// but only recognise a platform token if running in LCOW mode.

+	// Only recognise a platform token if LCOW is supported

 	if system.LCOWSupported() {

 		tpcMatch := tokenPlatformCommand.FindStringSubmatch(strings.ToLower(line))

 		if len(tpcMatch) != 0 {

@@ -177,7 +173,6 @@ func (d *Directive) possibleParserDirective(line string) error {

 func NewDefaultDirective() *Directive {

 	directive := Directive{}

 	directive.setEscapeToken(string(DefaultEscapeToken))

-	directive.setPlatformToken(defaultPlatformToken)

 	return &directive

 }

@@ -242,8 +237,10 @@ func newNodeFromLine(line string, directive *Directive) (*Node, error) {

 type Result struct {

 	AST         *Node

 	EscapeToken rune

-	Platform    string

-	Warnings    []string

+	// TODO @jhowardmsft - see https://github.com/moby/moby/issues/34617

+	// This next field will be removed in a future update for LCOW support.

+	OS       string

+	Warnings []string

 }

 // PrintWarnings to the writer

@@ -323,7 +320,7 @@ func Parse(rwc io.Reader) (*Result, error) {

 		AST:         root,

 		Warnings:    warnings,

 		EscapeToken: d.escapeToken,

-		Platform:    d.platformToken,

+		OS:          d.platformToken,

 	}, nil

 }

@@ -12,6 +12,7 @@ import (

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

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

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

 )

 // ImageBuild sends request to the daemon to build images.

@@ -29,6 +30,20 @@ func (cli *Client) ImageBuild(ctx context.Context, buildContext io.Reader, optio

 		return types.ImageBuildResponse{}, err

 	}

 	headers.Add("X-Registry-Config", base64.URLEncoding.EncodeToString(buf))

+

+	// TODO @jhowardmsft: system.IsPlatformEmpty is a temporary function. We need to move

+	// (in the reasonably short future) to a package which supports all the platform

+	// validation such as is proposed in https://github.com/containerd/containerd/pull/1403

+	if !system.IsPlatformEmpty(options.Platform) {

+		if err := cli.NewVersionError("1.32", "platform"); err != nil {

+			return types.ImageBuildResponse{}, err

+		}

+		platformJSON, err := json.Marshal(options.Platform)

+		if err != nil {

+			return types.ImageBuildResponse{}, err

+		}

+		headers.Add("X-Requested-Platform", string(platformJSON[:]))

+	}

 	headers.Set("Content-Type", "application/x-tar")

 	serverResp, err := cli.postRaw(ctx, "/build", query, buildContext, headers)

@@ -123,6 +138,5 @@ func (cli *Client) imageBuildOptionsToQuery(options types.ImageBuildOptions) (ur

 	if options.SessionID != "" {

 		query.Set("session", options.SessionID)

 	}

-

 	return query, nil

 }

@@ -1,6 +1,7 @@

 package client

 import (

+	"encoding/json"

 	"io"

 	"net/url"

@@ -8,6 +9,8 @@ import (

 	"github.com/docker/distribution/reference"

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

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

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

 )

 // ImageCreate creates a new image based in the parent options.

@@ -21,14 +24,25 @@ func (cli *Client) ImageCreate(ctx context.Context, parentReference string, opti

 	query := url.Values{}

 	query.Set("fromImage", reference.FamiliarName(ref))

 	query.Set("tag", getAPITagFromNamedRef(ref))

-	resp, err := cli.tryImageCreate(ctx, query, options.RegistryAuth)