@@ -40,7 +40,7 @@ type importExportBackend interface {

 }

 type registryBackend interface {

-	PullImage(ctx context.Context, image, tag string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

+	PullImage(ctx context.Context, image, tag, platform string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

 	PushImage(ctx context.Context, image, tag string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

 	SearchRegistryForImages(ctx context.Context, filtersArgs string, term string, limit int, authConfig *types.AuthConfig, metaHeaders map[string][]string) (*registry.SearchResults, error)

 }

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

 	"fmt"

 	"io"

 	"net/http"

+	"runtime"

 	"strconv"

 	"strings"

@@ -17,6 +18,7 @@ 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"

 	"golang.org/x/net/context"

 )

@@ -85,6 +87,41 @@ func (s *imageRouter) postImagesCreate(ctx context.Context, w http.ResponseWrite

 	)

 	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 runtime.GOOS == "windows" && 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 platform == "windows" && system.LCOWSupported() {

+		platform = "linux"

+	}

+

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

 	if image != "" { //pull

@@ -106,12 +143,13 @@ func (s *imageRouter) postImagesCreate(ctx context.Context, w http.ResponseWrite

 			}

 		}

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

+		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

+		// TODO @jhowardmsft LCOW Support: This will need extending for the platform too.

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

 	}

 	if err != nil {

@@ -129,7 +129,12 @@ func (daemon *Daemon) pullForBuilder(ctx context.Context, name string, authConfi

 		pullRegistryAuth = &resolvedConfig

 	}

-	if err := daemon.pullImageWithReference(ctx, ref, nil, pullRegistryAuth, output); err != nil {

+	// TODO @jhowardmsft LCOW Support: For now, use the runtime operating system of the host.

+	// When it gets to the builder part, this will need revisiting. There would have to be

+	// some indication from the user either through CLI flag to build, or through an explicit

+	// mechanism in a dockerfile such as a parser directive extension or an addition to

+	// the FROM statement syntax.

+	if err := daemon.pullImageWithReference(ctx, ref, runtime.GOOS, nil, pullRegistryAuth, output); err != nil {

 		return nil, err

 	}

 	return daemon.GetImage(name)

@@ -30,7 +30,7 @@ type Backend interface {

 	FindNetwork(idName string) (libnetwork.Network, error)

 	SetupIngress(clustertypes.NetworkCreateRequest, string) (<-chan struct{}, error)

 	ReleaseIngress() (<-chan struct{}, error)

-	PullImage(ctx context.Context, image, tag string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

+	PullImage(ctx context.Context, image, tag, platform string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

 	CreateManagedContainer(config types.ContainerCreateConfig) (container.ContainerCreateCreatedBody, error)

 	ContainerStart(name string, hostConfig *container.HostConfig, checkpoint string, checkpointDir string) error

 	ContainerStop(name string, seconds *int) error

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

 	"fmt"

 	"io"

 	"os"

+	"runtime"

 	"strings"

 	"syscall"

 	"time"

@@ -20,6 +21,7 @@ import (

 	containerpkg "github.com/docker/docker/container"

 	"github.com/docker/docker/daemon/cluster/convert"

 	executorpkg "github.com/docker/docker/daemon/cluster/executor"

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

 	"github.com/docker/libnetwork"

 	"github.com/docker/swarmkit/agent/exec"

 	"github.com/docker/swarmkit/api"

@@ -88,7 +90,13 @@ func (c *containerAdapter) pullImage(ctx context.Context) error {

 	pr, pw := io.Pipe()

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

 	go func() {

-		err := c.backend.PullImage(ctx, c.container.image(), "", metaHeaders, authConfig, pw)

+		// TODO @jhowardmsft LCOW Support: This will need revisiting as

+		// the stack is built up to include LCOW support for swarm.

+		platform := runtime.GOOS

+		if platform == "windows" && system.LCOWSupported() {

+			platform = "linux"

+		}

+		err := c.backend.PullImage(ctx, c.container.image(), "", platform, metaHeaders, authConfig, pw)

 		pw.CloseWithError(err)

 	}()

@@ -18,7 +18,7 @@ import (

 // PullImage initiates a pull operation. image is the repository name to pull, and

 // tag may be either empty, or indicate a specific tag to pull.

-func (daemon *Daemon) PullImage(ctx context.Context, image, tag string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

+func (daemon *Daemon) PullImage(ctx context.Context, image, tag, platform string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

 	// Special case: "pull -a" may send an image name with a

 	// trailing :. This is ugly, but let's not break API

 	// compatibility.

@@ -43,10 +43,10 @@ func (daemon *Daemon) PullImage(ctx context.Context, image, tag string, metaHead

 		}

 	}

-	return daemon.pullImageWithReference(ctx, ref, metaHeaders, authConfig, outStream)

+	return daemon.pullImageWithReference(ctx, ref, platform, metaHeaders, authConfig, outStream)

 }

-func (daemon *Daemon) pullImageWithReference(ctx context.Context, ref reference.Named, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

+func (daemon *Daemon) pullImageWithReference(ctx context.Context, ref reference.Named, platform string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

 	// Include a buffer so that slow client connections don't affect

 	// transfer performance.

 	progressChan := make(chan progress.Progress, 100)

@@ -60,11 +60,10 @@ func (daemon *Daemon) pullImageWithReference(ctx context.Context, ref reference.

 		close(writesDone)

 	}()

-	// ------------------------------------------------------------------------------

-	// TODO @jhowardmsft LCOW. For now, use just the store for the host OS. This will

-	// need some work to complete - we won't know the platform until after metadata

-	// is pulled from the repository. This affects plugin as well to complete.

-	// ------------------------------------------------------------------------------

+	// Default to the host OS platform in case it hasn't been populated with an explicit value.

+	if platform == "" {

+		platform = runtime.GOOS

+	}

 	imagePullConfig := &distribution.ImagePullConfig{

 		Config: distribution.Config{

@@ -73,12 +72,13 @@ func (daemon *Daemon) pullImageWithReference(ctx context.Context, ref reference.

 			ProgressOutput:   progress.ChanOutput(progressChan),

 			RegistryService:  daemon.RegistryService,

 			ImageEventLogger: daemon.LogImageEvent,

-			MetadataStore:    daemon.stores[runtime.GOOS].distributionMetadataStore,

-			ImageStore:       distribution.NewImageConfigStoreFromStore(daemon.stores[runtime.GOOS].imageStore),

-			ReferenceStore:   daemon.stores[runtime.GOOS].referenceStore,

+			MetadataStore:    daemon.stores[platform].distributionMetadataStore,

+			ImageStore:       distribution.NewImageConfigStoreFromStore(daemon.stores[platform].imageStore),

+			ReferenceStore:   daemon.stores[platform].referenceStore,

 		},

 		DownloadManager: daemon.downloadManager,

 		Schema2Types:    distribution.ImageTypes,

+		Platform:        platform,

 	}

 	err := distribution.Pull(ctx, ref, imagePullConfig)

@@ -59,6 +59,9 @@ type ImagePullConfig struct {

 	// Schema2Types is the valid schema2 configuration types allowed

 	// by the pull operation.

 	Schema2Types []string

+	// Platform is the requested platform of the image being pulled to ensure it can be validated

+	// when the host platform supports multiple image operating systems.

+	Platform string

 }

 // ImagePushConfig stores push configuration.