@@ -32,17 +32,17 @@ type copyBackend interface {

 // stateBackend includes functions to implement to provide container state lifecycle functionality.

 type stateBackend interface {

-	ContainerCreate(config types.ContainerCreateConfig, validateHostname bool) (container.ContainerCreateCreatedBody, error)

+	ContainerCreate(config types.ContainerCreateConfig) (container.ContainerCreateCreatedBody, error)

 	ContainerKill(name string, sig uint64) error

 	ContainerPause(name string) error

 	ContainerRename(oldName, newName string) error

 	ContainerResize(name string, height, width int) error

 	ContainerRestart(name string, seconds *int) error

 	ContainerRm(name string, config *types.ContainerRmConfig) error

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

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

 	ContainerStop(name string, seconds *int) error

 	ContainerUnpause(name string) error

-	ContainerUpdate(name string, hostConfig *container.HostConfig, validateHostname bool) (container.ContainerUpdateOKBody, error)

+	ContainerUpdate(name string, hostConfig *container.HostConfig) (container.ContainerUpdateOKBody, error)

 	ContainerWait(name string, timeout time.Duration) (int, error)

 }

@@ -156,8 +156,7 @@ func (s *containerRouter) postContainersStart(ctx context.Context, w http.Respon

 	checkpoint := r.Form.Get("checkpoint")

 	checkpointDir := r.Form.Get("checkpoint-dir")

-	validateHostname := versions.GreaterThanOrEqualTo(version, "1.24")

-	if err := s.backend.ContainerStart(vars["name"], hostConfig, validateHostname, checkpoint, checkpointDir); err != nil {

+	if err := s.backend.ContainerStart(vars["name"], hostConfig, checkpoint, checkpointDir); err != nil {

 		return err

 	}

@@ -332,7 +331,6 @@ func (s *containerRouter) postContainerUpdate(ctx context.Context, w http.Respon

 		return err

 	}

-	version := httputils.VersionFromContext(ctx)

 	var updateConfig container.UpdateConfig

 	decoder := json.NewDecoder(r.Body)

@@ -346,8 +344,7 @@ func (s *containerRouter) postContainerUpdate(ctx context.Context, w http.Respon

 	}

 	name := vars["name"]

-	validateHostname := versions.GreaterThanOrEqualTo(version, "1.24")

-	resp, err := s.backend.ContainerUpdate(name, hostConfig, validateHostname)

+	resp, err := s.backend.ContainerUpdate(name, hostConfig)

 	if err != nil {

 		return err

 	}

@@ -372,14 +369,13 @@ func (s *containerRouter) postContainersCreate(ctx context.Context, w http.Respo

 	version := httputils.VersionFromContext(ctx)

 	adjustCPUShares := versions.LessThan(version, "1.19")

-	validateHostname := versions.GreaterThanOrEqualTo(version, "1.24")

 	ccr, err := s.backend.ContainerCreate(types.ContainerCreateConfig{

 		Name:             name,

 		Config:           config,

 		HostConfig:       hostConfig,

 		NetworkingConfig: networkingConfig,

 		AdjustCPUShares:  adjustCPUShares,

-	}, validateHostname)

+	})

 	if err != nil {

 		return err

 	}

@@ -116,7 +116,7 @@ type Backend interface {

 	// ContainerAttachRaw attaches to container.

 	ContainerAttachRaw(cID string, stdin io.ReadCloser, stdout, stderr io.Writer, stream bool) error

 	// ContainerCreate creates a new Docker container and returns potential warnings

-	ContainerCreate(config types.ContainerCreateConfig, validateHostname bool) (container.ContainerCreateCreatedBody, error)

+	ContainerCreate(config types.ContainerCreateConfig) (container.ContainerCreateCreatedBody, error)

 	// ContainerRm removes a container specified by `id`.

 	ContainerRm(name string, config *types.ContainerRmConfig) error

 	// Commit creates a new Docker image from an existing Docker container.

@@ -124,7 +124,7 @@ type Backend interface {

 	// ContainerKill stops the container execution abruptly.

 	ContainerKill(containerID string, sig uint64) error

 	// ContainerStart starts a new container

-	ContainerStart(containerID string, hostConfig *container.HostConfig, validateHostname bool, checkpoint string, checkpointDir string) error

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

 	// ContainerWait stops processing until the given container is stopped.

 	ContainerWait(containerID string, timeout time.Duration) (int, error)

 	// ContainerUpdateCmdOnBuild updates container.Path and container.Args

@@ -301,7 +301,7 @@ func workdir(b *Builder, args []string, attributes map[string]bool, original str

 		return nil

 	}

-	container, err := b.docker.ContainerCreate(types.ContainerCreateConfig{Config: b.runConfig}, true)

+	container, err := b.docker.ContainerCreate(types.ContainerCreateConfig{Config: b.runConfig})

 	if err != nil {

 		return err

 	}

@@ -180,7 +180,7 @@ func (b *Builder) runContextCommand(args []string, allowRemote bool, allowLocalD

 		return nil

 	}

-	container, err := b.docker.ContainerCreate(types.ContainerCreateConfig{Config: b.runConfig}, true)

+	container, err := b.docker.ContainerCreate(types.ContainerCreateConfig{Config: b.runConfig})

 	if err != nil {

 		return err

 	}

@@ -496,7 +496,7 @@ func (b *Builder) create() (string, error) {

 	c, err := b.docker.ContainerCreate(types.ContainerCreateConfig{

 		Config:     b.runConfig,

 		HostConfig: hostConfig,

-	}, true)

+	})

 	if err != nil {

 		return "", err

 	}

@@ -537,7 +537,7 @@ func (b *Builder) run(cID string) (err error) {

 		}

 	}()

-	if err := b.docker.ContainerStart(cID, nil, true, "", ""); err != nil {

+	if err := b.docker.ContainerStart(cID, nil, "", ""); err != nil {

 		close(finished)

 		if cancelErr := <-cancelErrCh; cancelErr != nil {

 			logrus.Debugf("Build cancelled (%v) and got an error from ContainerStart: %v",

@@ -28,8 +28,8 @@ type Backend interface {

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

 	SetupIngress(req clustertypes.NetworkCreateRequest, nodeIP string) error

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

-	CreateManagedContainer(config types.ContainerCreateConfig, validateHostname bool) (container.ContainerCreateCreatedBody, error)

-	ContainerStart(name string, hostConfig *container.HostConfig, validateHostname bool, checkpoint string, checkpointDir string) 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

 	ContainerLogs(context.Context, string, *backend.ContainerLogsConfig, chan struct{}) error

 	ConnectContainerToNetwork(containerName, networkName string, endpointConfig *network.EndpointSettings) error

@@ -11,12 +11,10 @@ import (

 	"github.com/Sirupsen/logrus"

 	"github.com/docker/distribution/digest"

-	"github.com/docker/docker/api/server/httputils"

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

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

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

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

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

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

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

 	"github.com/docker/docker/reference"

@@ -215,8 +213,6 @@ func (c *containerAdapter) waitForDetach(ctx context.Context) error {

 func (c *containerAdapter) create(ctx context.Context) error {

 	var cr containertypes.ContainerCreateCreatedBody

 	var err error

-	version := httputils.VersionFromContext(ctx)

-	validateHostname := versions.GreaterThanOrEqualTo(version, "1.24")

 	if cr, err = c.backend.CreateManagedContainer(types.ContainerCreateConfig{

 		Name:       c.container.name(),

@@ -224,7 +220,7 @@ func (c *containerAdapter) create(ctx context.Context) error {

 		HostConfig: c.container.hostConfig(),

 		// Use the first network in container create

 		NetworkingConfig: c.container.createNetworkingConfig(),

-	}, validateHostname); err != nil {

+	}); err != nil {

 		return err

 	}

@@ -263,9 +259,7 @@ func (c *containerAdapter) create(ctx context.Context) error {

 }

 func (c *containerAdapter) start(ctx context.Context) error {

-	version := httputils.VersionFromContext(ctx)

-	validateHostname := versions.GreaterThanOrEqualTo(version, "1.24")

-	return c.backend.ContainerStart(c.container.name(), nil, validateHostname, "", "")

+	return c.backend.ContainerStart(c.container.name(), nil, "", "")

 }

 func (c *containerAdapter) inspect(ctx context.Context) (types.ContainerJSON, error) {

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

 import (

 	"fmt"

 	"path/filepath"

-	"regexp"

 	"time"

 	"github.com/docker/docker/api/errors"

@@ -204,7 +203,7 @@ func (daemon *Daemon) setHostConfig(container *container.Container, hostConfig *

 // verifyContainerSettings performs validation of the hostconfig and config

 // structures.

-func (daemon *Daemon) verifyContainerSettings(hostConfig *containertypes.HostConfig, config *containertypes.Config, update bool, validateHostname bool) ([]string, error) {

+func (daemon *Daemon) verifyContainerSettings(hostConfig *containertypes.HostConfig, config *containertypes.Config, update bool) ([]string, error) {

 	// First perform verification of settings common across all platforms.

 	if config != nil {

@@ -222,18 +221,6 @@ func (daemon *Daemon) verifyContainerSettings(hostConfig *containertypes.HostCon

 			}

 		}

-		// Validate if the given hostname is RFC 1123 (https://tools.ietf.org/html/rfc1123) compliant.

-		if validateHostname && len(config.Hostname) > 0 {

-			// RFC1123 specifies that 63 bytes is the maximium length

-			// Windows has the limitation of 63 bytes in length

-			// Linux hostname is limited to HOST_NAME_MAX=64, not including the terminating null byte.

-			// We limit the length to 63 bytes here to match RFC1035 and RFC1123.

-			matched, _ := regexp.MatchString("^(([[:alnum:]]|[[:alnum:]][[:alnum:]\\-]*[[:alnum:]])\\.)*([[:alnum:]]|[[:alnum:]][[:alnum:]\\-]*[[:alnum:]])$", config.Hostname)

-			if len(config.Hostname) > 63 || !matched {

-				return nil, fmt.Errorf("invalid hostname format: %s", config.Hostname)

-			}

-		}

-

 		// Validate if Env contains empty variable or not (e.g., ``, `=foo`)

 		for _, env := range config.Env {

 			if _, err := opts.ValidateEnv(env); err != nil {

@@ -25,22 +25,22 @@ import (

 )

 // CreateManagedContainer creates a container that is managed by a Service

-func (daemon *Daemon) CreateManagedContainer(params types.ContainerCreateConfig, validateHostname bool) (containertypes.ContainerCreateCreatedBody, error) {

-	return daemon.containerCreate(params, true, validateHostname)

+func (daemon *Daemon) CreateManagedContainer(params types.ContainerCreateConfig) (containertypes.ContainerCreateCreatedBody, error) {

+	return daemon.containerCreate(params, true)

 }

 // ContainerCreate creates a regular container

-func (daemon *Daemon) ContainerCreate(params types.ContainerCreateConfig, validateHostname bool) (containertypes.ContainerCreateCreatedBody, error) {

-	return daemon.containerCreate(params, false, validateHostname)

+func (daemon *Daemon) ContainerCreate(params types.ContainerCreateConfig) (containertypes.ContainerCreateCreatedBody, error) {

+	return daemon.containerCreate(params, false)

 }

-func (daemon *Daemon) containerCreate(params types.ContainerCreateConfig, managed bool, validateHostname bool) (containertypes.ContainerCreateCreatedBody, error) {

+func (daemon *Daemon) containerCreate(params types.ContainerCreateConfig, managed bool) (containertypes.ContainerCreateCreatedBody, error) {

 	start := time.Now()

 	if params.Config == nil {

 		return containertypes.ContainerCreateCreatedBody{}, fmt.Errorf("Config cannot be empty in order to create a container")

 	}

-	warnings, err := daemon.verifyContainerSettings(params.HostConfig, params.Config, false, validateHostname)

+	warnings, err := daemon.verifyContainerSettings(params.HostConfig, params.Config, false)

 	if err != nil {

 		return containertypes.ContainerCreateCreatedBody{Warnings: warnings}, err

 	}

@@ -19,7 +19,7 @@ import (

 )

 // ContainerStart starts a container.

-func (daemon *Daemon) ContainerStart(name string, hostConfig *containertypes.HostConfig, validateHostname bool, checkpoint string, checkpointDir string) error {

+func (daemon *Daemon) ContainerStart(name string, hostConfig *containertypes.HostConfig, checkpoint string, checkpointDir string) error {

 	if checkpoint != "" && !daemon.HasExperimental() {

 		return apierrors.NewBadRequestError(fmt.Errorf("checkpoint is only supported in experimental mode"))

 	}

@@ -73,7 +73,7 @@ func (daemon *Daemon) ContainerStart(name string, hostConfig *containertypes.Hos

 	// check if hostConfig is in line with the current system settings.

 	// It may happen cgroups are umounted or the like.

-	if _, err = daemon.verifyContainerSettings(container.HostConfig, nil, false, validateHostname); err != nil {

+	if _, err = daemon.verifyContainerSettings(container.HostConfig, nil, false); err != nil {

 		return err

 	}

 	// Adapt for old containers in case we have updates in this function and

@@ -7,10 +7,10 @@ import (

 )

 // ContainerUpdate updates configuration of the container

-func (daemon *Daemon) ContainerUpdate(name string, hostConfig *container.HostConfig, validateHostname bool) (container.ContainerUpdateOKBody, error) {

+func (daemon *Daemon) ContainerUpdate(name string, hostConfig *container.HostConfig) (container.ContainerUpdateOKBody, error) {

 	var warnings []string

-	warnings, err := daemon.verifyContainerSettings(hostConfig, nil, true, validateHostname)

+	warnings, err := daemon.verifyContainerSettings(hostConfig, nil, true)

 	if err != nil {

 		return container.ContainerUpdateOKBody{Warnings: warnings}, err

 	}

@@ -4354,42 +4354,6 @@ func (s *DockerSuite) TestRunVolumeCopyFlag(c *check.C) {

 	c.Assert(err, checker.NotNil, check.Commentf(out))

 }

-func (s *DockerSuite) TestRunTooLongHostname(c *check.C) {

-	// Test case in #21445

-	hostname1 := "this-is-a-way-too-long-hostname-but-it-should-give-a-nice-error.local"

-	out, _, err := dockerCmdWithError("run", "--hostname", hostname1, "busybox", "echo", "test")

-	c.Assert(err, checker.NotNil, check.Commentf("Expected docker run to fail!"))

-	c.Assert(out, checker.Contains, "invalid hostname format:", check.Commentf("Expected to have 'invalid hostname format:' in the output, get: %s!", out))

-

-	// Additional test cases

-	validHostnames := map[string]string{

-		"hostname":    "hostname",

-		"host-name":   "host-name",

-		"hostname123": "hostname123",

-		"123hostname": "123hostname",

-		"hostname-of-63-bytes-long-should-be-valid-and-without-any-error": "hostname-of-63-bytes-long-should-be-valid-and-without-any-error",

-	}

-	for hostname := range validHostnames {

-		dockerCmd(c, "run", "--hostname", hostname, "busybox", "echo", "test")

-	}

-

-	invalidHostnames := map[string]string{

-		"^hostname": "invalid hostname format: ^hostname",

-		"hostname%": "invalid hostname format: hostname%",

-		"host&name": "invalid hostname format: host&name",

-		"-hostname": "invalid hostname format: -hostname",

-		"host_name": "invalid hostname format: host_name",

-		"hostname-of-64-bytes-long-should-be-invalid-and-be-with-an-error": "invalid hostname format: hostname-of-64-bytes-long-should-be-invalid-and-be-with-an-error",

-	}

-

-	for hostname, expectedError := range invalidHostnames {

-		out, _, err = dockerCmdWithError("run", "--hostname", hostname, "busybox", "echo", "test")

-		c.Assert(err, checker.NotNil, check.Commentf("Expected docker run to fail!"))

-		c.Assert(out, checker.Contains, expectedError, check.Commentf("Expected to have '%s' in the output, get: %s!", expectedError, out))

-

-	}

-}

-

 // Test case for #21976

 func (s *DockerSuite) TestRunDNSInHostMode(c *check.C) {

 	testRequires(c, DaemonIsLinux, NotUserNamespace)