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

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

 	"github.com/pkg/errors"

 	"golang.org/x/sync/errgroup"

+	"google.golang.org/grpc"

 )

 // ImageComponent provides an interface for working with images

@@ -40,6 +41,13 @@ func NewBackend(components ImageComponent, builder Builder, fsCache *fscache.FSC

 	return &Backend{imageComponent: components, builder: builder, fsCache: fsCache, buildkit: buildkit}, nil

 }

+// RegisterGRPC registers buildkit controller to the grpc server.

+func (b *Backend) RegisterGRPC(s *grpc.Server) {

+	if b.buildkit != nil {

+		b.buildkit.RegisterGRPC(s)

+	}

+}

+

 // Build builds an image from a Source

 func (b *Backend) Build(ctx context.Context, config backend.BuildConfig) (string, error) {

 	options := config.Options

new file mode 100644

@@ -0,0 +1,8 @@

+package grpc // import "github.com/docker/docker/api/server/router/grpc"

+

+import "google.golang.org/grpc"

+

+// Backend abstracts a registerable GRPC service.

+type Backend interface {

+	RegisterGRPC(*grpc.Server)

+}

new file mode 100644

@@ -0,0 +1,37 @@

+package grpc // import "github.com/docker/docker/api/server/router/grpc"

+

+import (

+	"github.com/docker/docker/api/server/router"

+	"golang.org/x/net/http2"

+	"google.golang.org/grpc"

+)

+

+type grpcRouter struct {

+	routes     []router.Route

+	grpcServer *grpc.Server

+	h2Server   *http2.Server

+}

+

+// NewRouter initializes a new grpc http router

+func NewRouter(backends ...Backend) router.Router {

+	r := &grpcRouter{

+		h2Server:   &http2.Server{},

+		grpcServer: grpc.NewServer(),

+	}

+	for _, b := range backends {

+		b.RegisterGRPC(r.grpcServer)

+	}

+	r.initRoutes()

+	return r

+}

+

+// Routes returns the available routers to the session controller

+func (r *grpcRouter) Routes() []router.Route {

+	return r.routes

+}

+

+func (r *grpcRouter) initRoutes() {

+	r.routes = []router.Route{

+		router.NewPostRoute("/grpc", r.serveGRPC),

+	}

+}

new file mode 100644

@@ -0,0 +1,45 @@

+package grpc // import "github.com/docker/docker/api/server/router/grpc"

+

+import (

+	"context"

+	"net/http"

+

+	"github.com/pkg/errors"

+	"golang.org/x/net/http2"

+)

+

+func (gr *grpcRouter) serveGRPC(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {

+	h, ok := w.(http.Hijacker)

+	if !ok {

+		return errors.New("handler does not support hijack")

+	}

+	proto := r.Header.Get("Upgrade")

+	if proto == "" {

+		return errors.New("no upgrade proto in request")

+	}

+	if proto != "h2c" {

+		return errors.Errorf("protocol %s not supported", proto)

+	}

+

+	conn, _, err := h.Hijack()

+	if err != nil {

+		return err

+	}

+	resp := &http.Response{

+		StatusCode: http.StatusSwitchingProtocols,

+		ProtoMajor: 1,

+		ProtoMinor: 1,

+		Header:     http.Header{},

+	}

+	resp.Header.Set("Connection", "Upgrade")

+	resp.Header.Set("Upgrade", proto)

+

+	// set raw mode

+	conn.Write([]byte{})

+	resp.Write(conn)

+

+	// https://godoc.org/golang.org/x/net/http2#Server.ServeConn

+	// TODO: is it a problem that conn has already been written to?

+	gr.h2Server.ServeConn(conn, &http2.ServeConnOpts{Handler: gr.grpcServer})

+	return nil

+}

@@ -31,6 +31,7 @@ import (

 	"github.com/moby/buildkit/util/tracing"

 	"github.com/pkg/errors"

 	"golang.org/x/sync/errgroup"

+	"google.golang.org/grpc"

 	grpcmetadata "google.golang.org/grpc/metadata"

 )

@@ -104,6 +105,11 @@ func New(opt Opt) (*Builder, error) {

 	return b, nil

 }

+// RegisterGRPC registers controller to the grpc server.

+func (b *Builder) RegisterGRPC(s *grpc.Server) {

+	b.controller.Register(s)

+}

+

 // Cancel cancels a build using ID

 func (b *Builder) Cancel(ctx context.Context, id string) error {

 	b.mu.Lock()

@@ -38,6 +38,17 @@ func (cli *Client) postHijacked(ctx context.Context, path string, query url.Valu

 	return types.HijackedResponse{Conn: conn, Reader: bufio.NewReader(conn)}, err

 }

+// DialHijack returns a hijacked connection with negotiated protocol proto.

+func (cli *Client) DialHijack(ctx context.Context, url, proto string, meta map[string][]string) (net.Conn, error) {

+	req, err := http.NewRequest("POST", url, nil)

+	if err != nil {

+		return nil, err

+	}

+	req = cli.addHeaders(req, meta)

+

+	return cli.setupHijackConn(ctx, req, proto)

+}

+

 // fallbackDial is used when WithDialer() was not called.

 // See cli.Dialer().

 func fallbackDial(proto, addr string, tlsConfig *tls.Config) (net.Conn, error) {

@@ -38,7 +38,7 @@ type CommonAPIClient interface {

 	ServerVersion(ctx context.Context) (types.Version, error)

 	NegotiateAPIVersion(ctx context.Context)

 	NegotiateAPIVersionPing(types.Ping)

-	DialSession(ctx context.Context, proto string, meta map[string][]string) (net.Conn, error)

+	DialHijack(ctx context.Context, url, proto string, meta map[string][]string) (net.Conn, error)

 	Dialer() func(context.Context) (net.Conn, error)

 	Close() error

 }

deleted file mode 100644

@@ -1,18 +0,0 @@

-package client // import "github.com/docker/docker/client"

-

-import (

-	"context"

-	"net"

-	"net/http"

-)

-

-// DialSession returns a connection that can be used communication with daemon

-func (cli *Client) DialSession(ctx context.Context, proto string, meta map[string][]string) (net.Conn, error) {

-	req, err := http.NewRequest("POST", "/session", nil)

-	if err != nil {

-		return nil, err

-	}

-	req = cli.addHeaders(req, meta)

-

-	return cli.setupHijackConn(ctx, req, proto)

-}

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

 	checkpointrouter "github.com/docker/docker/api/server/router/checkpoint"

 	"github.com/docker/docker/api/server/router/container"

 	distributionrouter "github.com/docker/docker/api/server/router/distribution"

+	grpcrouter "github.com/docker/docker/api/server/router/grpc"

 	"github.com/docker/docker/api/server/router/image"

 	"github.com/docker/docker/api/server/router/network"

 	pluginrouter "github.com/docker/docker/api/server/router/plugin"

@@ -481,6 +482,16 @@ func initRouter(opts routerOptions) {

 		distributionrouter.NewRouter(opts.daemon.ImageService()),

 	}

+	grpcBackends := []grpcrouter.Backend{}

+	for _, b := range []interface{}{opts.daemon, opts.buildBackend} {

+		if b, ok := b.(grpcrouter.Backend); ok {

+			grpcBackends = append(grpcBackends, b)

+		}

+	}

+	if len(grpcBackends) > 0 {

+		routers = append(routers, grpcrouter.NewRouter(grpcBackends...))

+	}

+

 	if opts.daemon.NetworkControllerEnabled() {

 		routers = append(routers, network.NewRouter(opts.daemon, opts.cluster))

 	}

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

 import (

 	"context"

 	"io/ioutil"

+	"net"

 	"net/http"

 	"strings"

 	"testing"

@@ -109,7 +110,9 @@ func testBuildWithSession(t *testing.T, client dclient.APIClient, daemonHost str

 	g, ctx := errgroup.WithContext(ctx)

 	g.Go(func() error {

-		return sess.Run(ctx, client.DialSession)

+		return sess.Run(ctx, func(ctx context.Context, proto string, meta map[string][]string) (net.Conn, error) {

+			return client.DialHijack(ctx, "/session", "h2c", meta)

+		})

 	})

 	g.Go(func() error {