@@ -110,11 +110,6 @@ type Controller struct {

 	mu               sync.Mutex

 }

-type initializer struct {

-	fn    func(driverapi.Registerer, map[string]interface{}) error

-	ntype string

-}

-

 // New creates a new instance of network controller.

 func New(cfgOptions ...config.Option) (*Controller, error) {

 	c := &Controller{

@@ -141,10 +136,8 @@ func New(cfgOptions ...config.Option) (*Controller, error) {

 		return nil, err

 	}

-	for _, i := range getInitializers() {

-		if err := i.fn(&c.drvRegistry, c.makeDriverConfig(i.ntype)); err != nil {

-			return nil, err

-		}

+	if err := registerNetworkDrivers(&c.drvRegistry, c.makeDriverConfig); err != nil {

+		return nil, err

 	}

 	if err := initIPAMDrivers(&c.ipamRegistry, c.cfg.PluginGetter, c.cfg.DefaultAddressPool); err != nil {

@@ -28,7 +28,7 @@ import (

 )

 const (

-	networkType                = "bridge"

+	NetworkType                = "bridge"

 	vethPrefix                 = "veth"

 	vethLen                    = len(vethPrefix) + 7

 	defaultContainerVethPrefix = "eth"

@@ -174,7 +174,7 @@ func Register(r driverapi.Registerer, config map[string]interface{}) error {

 	if err := d.configure(config); err != nil {

 		return err

 	}

-	return r.RegisterDriver(networkType, d, driverapi.Capability{

+	return r.RegisterDriver(NetworkType, d, driverapi.Capability{

 		DataScope:         datastore.LocalScope,

 		ConnectivityScope: datastore.LocalScope,

 	})

@@ -1433,7 +1433,7 @@ func (d *driver) link(network *bridgeNetwork, endpoint *bridgeEndpoint, enable b

 }

 func (d *driver) Type() string {

-	return networkType

+	return NetworkType

 }

 func (d *driver) IsBuiltIn() bool {

@@ -9,7 +9,7 @@ import (

 	"github.com/docker/docker/libnetwork/types"

 )

-const networkType = "host"

+const NetworkType = "host"

 type driver struct {

 	network string

@@ -24,7 +24,7 @@ func Init(dc driverapi.DriverCallback, _ map[string]interface{}) error {

 }

 func Register(r driverapi.Registerer, _ map[string]interface{}) error {

-	return r.RegisterDriver(networkType, &driver{}, driverapi.Capability{

+	return r.RegisterDriver(NetworkType, &driver{}, driverapi.Capability{

 		DataScope:         datastore.LocalScope,

 		ConnectivityScope: datastore.LocalScope,

 	})

@@ -50,7 +50,7 @@ func (d *driver) CreateNetwork(id string, option map[string]interface{}, nInfo d

 	defer d.Unlock()

 	if d.network != "" {

-		return types.ForbiddenErrorf("only one instance of \"%s\" network is allowed", networkType)

+		return types.ForbiddenErrorf("only one instance of \"%s\" network is allowed", NetworkType)

 	}

 	d.network = id

@@ -59,7 +59,7 @@ func (d *driver) CreateNetwork(id string, option map[string]interface{}, nInfo d

 }

 func (d *driver) DeleteNetwork(nid string) error {

-	return types.ForbiddenErrorf("network of type \"%s\" cannot be deleted", networkType)

+	return types.ForbiddenErrorf("network of type \"%s\" cannot be deleted", NetworkType)

 }

 func (d *driver) CreateEndpoint(nid, eid string, ifInfo driverapi.InterfaceInfo, epOptions map[string]interface{}) error {

@@ -93,7 +93,7 @@ func (d *driver) RevokeExternalConnectivity(nid, eid string) error {

 }

 func (d *driver) Type() string {

-	return networkType

+	return NetworkType

 }

 func (d *driver) IsBuiltIn() bool {

@@ -9,7 +9,7 @@ import (

 func TestDriver(t *testing.T) {

 	d := &driver{}

-	if d.Type() != networkType {

+	if d.Type() != NetworkType {

 		t.Fatal("Unexpected network type returned by driver")

 	}

@@ -18,7 +18,7 @@ const (

 	vethPrefix          = "veth"

 	vethLen             = len(vethPrefix) + 7

-	driverName    = "ipvlan"      // driver type name

+	NetworkType   = "ipvlan"      // driver type name

 	parentOpt     = "parent"      // parent interface -o parent

 	driverModeOpt = "ipvlan_mode" // mode -o ipvlan_mode

 	driverFlagOpt = "ipvlan_flag" // flag -o ipvlan_flag

@@ -70,7 +70,7 @@ func Register(r driverapi.Registerer, config map[string]interface{}) error {

 	if err := d.initStore(config); err != nil {

 		return err

 	}

-	return r.RegisterDriver(driverName, d, driverapi.Capability{

+	return r.RegisterDriver(NetworkType, d, driverapi.Capability{

 		DataScope:         datastore.LocalScope,

 		ConnectivityScope: datastore.GlobalScope,

 	})

@@ -89,7 +89,7 @@ func (d *driver) EndpointOperInfo(nid, eid string) (map[string]interface{}, erro

 }

 func (d *driver) Type() string {

-	return driverName

+	return NetworkType

 }

 func (d *driver) IsBuiltIn() bool {

@@ -17,7 +17,7 @@ const (

 	containerVethPrefix = "eth"

 	vethPrefix          = "veth"

 	vethLen             = len(vethPrefix) + 7

-	driverName          = "macvlan"      // driver type name

+	NetworkType         = "macvlan"      // driver type name

 	modePrivate         = "private"      // macvlan mode private

 	modeVepa            = "vepa"         // macvlan mode vepa

 	modeBridge          = "bridge"       // macvlan mode bridge

@@ -64,7 +64,7 @@ func Register(r driverapi.Registerer, config map[string]interface{}) error {

 	if err := d.initStore(config); err != nil {

 		return err

 	}

-	return r.RegisterDriver(driverName, d, driverapi.Capability{

+	return r.RegisterDriver(NetworkType, d, driverapi.Capability{

 		DataScope:         datastore.LocalScope,

 		ConnectivityScope: datastore.GlobalScope,

 	})

@@ -83,7 +83,7 @@ func (d *driver) EndpointOperInfo(nid, eid string) (map[string]interface{}, erro

 }

 func (d *driver) Type() string {

-	return driverName

+	return NetworkType

 }

 func (d *driver) IsBuiltIn() bool {

@@ -9,7 +9,7 @@ import (

 	"github.com/docker/docker/libnetwork/types"

 )

-const networkType = "null"

+const NetworkType = "null"

 type driver struct {

 	network string

@@ -18,7 +18,7 @@ type driver struct {

 // Register registers a new instance of the null driver.

 func Register(r driverapi.Registerer, _ map[string]interface{}) error {

-	return r.RegisterDriver(networkType, &driver{}, driverapi.Capability{

+	return r.RegisterDriver(NetworkType, &driver{}, driverapi.Capability{

 		DataScope: datastore.LocalScope,

 	})

 }

@@ -43,7 +43,7 @@ func (d *driver) CreateNetwork(id string, option map[string]interface{}, nInfo d

 	defer d.Unlock()

 	if d.network != "" {

-		return types.ForbiddenErrorf("only one instance of \"%s\" network is allowed", networkType)

+		return types.ForbiddenErrorf("only one instance of \"%s\" network is allowed", NetworkType)

 	}

 	d.network = id

@@ -52,7 +52,7 @@ func (d *driver) CreateNetwork(id string, option map[string]interface{}, nInfo d

 }

 func (d *driver) DeleteNetwork(nid string) error {

-	return types.ForbiddenErrorf("network of type \"%s\" cannot be deleted", networkType)

+	return types.ForbiddenErrorf("network of type \"%s\" cannot be deleted", NetworkType)

 }

 func (d *driver) CreateEndpoint(nid, eid string, ifInfo driverapi.InterfaceInfo, epOptions map[string]interface{}) error {

@@ -86,7 +86,7 @@ func (d *driver) RevokeExternalConnectivity(nid, eid string) error {

 }

 func (d *driver) Type() string {

-	return networkType

+	return NetworkType

 }

 func (d *driver) IsBuiltIn() bool {

@@ -9,7 +9,7 @@ import (

 func TestDriver(t *testing.T) {

 	d := &driver{}

-	if d.Type() != networkType {

+	if d.Type() != NetworkType {

 		t.Fatalf("Unexpected network type returned by driver")

 	}

@@ -16,7 +16,7 @@ import (

 )

 const (

-	networkType  = "overlay"

+	NetworkType  = "overlay"

 	vethPrefix   = "veth"

 	vethLen      = len(vethPrefix) + 7

 	vxlanEncap   = 50

@@ -47,7 +47,7 @@ func Register(r driverapi.Registerer, config map[string]interface{}) error {

 		secMap: &encrMap{nodes: map[string][]*spi{}},

 		config: config,

 	}

-	return r.RegisterDriver(networkType, d, driverapi.Capability{

+	return r.RegisterDriver(NetworkType, d, driverapi.Capability{

 		DataScope:         datastore.GlobalScope,

 		ConnectivityScope: datastore.GlobalScope,

 	})

@@ -61,7 +61,7 @@ func (d *driver) configure() error {

 }

 func (d *driver) Type() string {

-	return networkType

+	return NetworkType

 }

 func (d *driver) IsBuiltIn() bool {

@@ -17,7 +17,7 @@ import (

 )

 const (

-	networkType = "overlay"

+	NetworkType = "overlay"

 )

 type driver struct {

@@ -33,7 +33,7 @@ func Register(r driverapi.Registerer, _ map[string]interface{}) error {

 	d.restoreHNSNetworks()

-	return r.RegisterDriver(networkType, d, driverapi.Capability{

+	return r.RegisterDriver(NetworkType, d, driverapi.Capability{

 		DataScope:         datastore.GlobalScope,

 		ConnectivityScope: datastore.GlobalScope,

 	})

@@ -48,7 +48,7 @@ func (d *driver) restoreHNSNetworks() error {

 	}

 	for _, v := range hnsresponse {

-		if v.Type != networkType {

+		if v.Type != NetworkType {

 			continue

 		}

@@ -105,7 +105,7 @@ func (d *driver) convertToOverlayNetwork(v *hcsshim.HNSNetwork) *network {

 }

 func (d *driver) Type() string {

-	return networkType

+	return NetworkType

 }

 func (d *driver) IsBuiltIn() bool {

@@ -109,16 +109,20 @@ const (

 	errNotFound = "HNS failed with error : The object identifier does not represent a valid object. "

 )

+var builtinLocalDrivers = map[string]struct{}{

+	"transparent": {},

+	"l2bridge":    {},

+	"l2tunnel":    {},

+	"nat":         {},

+	"internal":    {},

+	"private":     {},

+	"ics":         {},

+}

+

 // IsBuiltinLocalDriver validates if network-type is a builtin local-scoped driver

 func IsBuiltinLocalDriver(networkType string) bool {

-	if "l2bridge" == networkType || "l2tunnel" == networkType ||

-		"nat" == networkType || "ics" == networkType ||

-		"transparent" == networkType || "internal" == networkType ||

-		"private" == networkType {

-		return true

-	}

-

-	return false

+	_, ok := builtinLocalDrivers[networkType]

+	return ok

 }

 // New constructs a new bridge driver

@@ -127,24 +131,23 @@ func newDriver(networkType string) *driver {

 }

 // GetInit returns an initializer for the given network type

-func GetInit(networkType string) func(dc driverapi.Registerer, config map[string]interface{}) error {

-	return func(dc driverapi.Registerer, config map[string]interface{}) error {

-		if !IsBuiltinLocalDriver(networkType) {

-			return types.BadRequestErrorf("Network type not supported: %s", networkType)

-		}

-

+func RegisterBuiltinLocalDrivers(r driverapi.Registerer, driverConfig func(string) map[string]interface{}) error {

+	for networkType := range builtinLocalDrivers {

 		d := newDriver(networkType)

-

-		err := d.initStore(config)

+		err := d.initStore(driverConfig(networkType))

 		if err != nil {

-			return err

+			return fmt.Errorf("failed to initialize %q driver: %w", networkType, err)

 		}

-		return dc.RegisterDriver(networkType, d, driverapi.Capability{

+		err = r.RegisterDriver(networkType, d, driverapi.Capability{

 			DataScope:         datastore.LocalScope,

 			ConnectivityScope: datastore.LocalScope,

 		})

+		if err != nil {

+			return fmt.Errorf("failed to register %q driver: %w", networkType, err)

+		}

 	}

+	return nil

 }

 func (d *driver) getNetwork(id string) (*hnsNetwork, error) {

@@ -4,8 +4,6 @@ import (

 	"github.com/docker/docker/libnetwork/drivers/null"

 )

-func getInitializers() []initializer {

-	return []initializer{

-		{null.Register, "null"},

-	}

+func registerNetworkDrivers(r driverapi.Registerer, driverConfig func(string) map[string]interface{}) error {

+	return null.Register(r, driverConfig(null.NetworkType))

 }

@@ -1,6 +1,9 @@

 package libnetwork

 import (

+	"fmt"

+

+	"github.com/docker/docker/libnetwork/driverapi"

 	"github.com/docker/docker/libnetwork/drivers/bridge"

 	"github.com/docker/docker/libnetwork/drivers/host"

 	"github.com/docker/docker/libnetwork/drivers/ipvlan"

@@ -9,14 +12,22 @@ import (

 	"github.com/docker/docker/libnetwork/drivers/overlay"

 )

-func getInitializers() []initializer {

-	in := []initializer{

-		{bridge.Register, "bridge"},

-		{host.Register, "host"},

-		{ipvlan.Register, "ipvlan"},

-		{macvlan.Register, "macvlan"},

-		{null.Register, "null"},

-		{overlay.Register, "overlay"},

+func registerNetworkDrivers(r driverapi.Registerer, driverConfig func(string) map[string]interface{}) error {

+	for _, nr := range []struct {

+		ntype    string

+		register func(driverapi.Registerer, map[string]interface{}) error

+	}{

+		{ntype: bridge.NetworkType, register: bridge.Register},

+		{ntype: host.NetworkType, register: host.Register},

+		{ntype: ipvlan.NetworkType, register: ipvlan.Register},

+		{ntype: macvlan.NetworkType, register: macvlan.Register},

+		{ntype: null.NetworkType, register: null.Register},

+		{ntype: overlay.NetworkType, register: overlay.Register},

+	} {

+		if err := nr.register(r, driverConfig(nr.ntype)); err != nil {

+			return fmt.Errorf("failed to register %q driver: %w", nr.ntype, err)

+		}

 	}

-	return in

+

+	return nil

 }

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

 package libnetwork

-func getInitializers() []initializer {

+func registerNetworkDrivers(r driverapi.Registerer, driverConfig func(string) map[string]interface{}) error {

 	return nil

 }

@@ -1,21 +1,26 @@

 package libnetwork

 import (

+	"fmt"

+

+	"github.com/docker/docker/libnetwork/driverapi"

 	"github.com/docker/docker/libnetwork/drivers/null"

 	"github.com/docker/docker/libnetwork/drivers/windows"

 	"github.com/docker/docker/libnetwork/drivers/windows/overlay"

 )

-func getInitializers() []initializer {

-	return []initializer{

-		{null.Register, "null"},

-		{overlay.Register, "overlay"},

-		{windows.GetInit("transparent"), "transparent"},

-		{windows.GetInit("l2bridge"), "l2bridge"},

-		{windows.GetInit("l2tunnel"), "l2tunnel"},

-		{windows.GetInit("nat"), "nat"},

-		{windows.GetInit("internal"), "internal"},

-		{windows.GetInit("private"), "private"},

-		{windows.GetInit("ics"), "ics"},

+func registerNetworkDrivers(r driverapi.Registerer, driverConfig func(string) map[string]interface{}) error {

+	for _, nr := range []struct {

+		ntype    string

+		register func(driverapi.Registerer, map[string]interface{}) error

+	}{

+		{ntype: null.NetworkType, register: null.Register},

+		{ntype: overlay.NetworkType, register: overlay.Register},

+	} {

+		if err := nr.register(r, driverConfig(nr.ntype)); err != nil {

+			return fmt.Errorf("failed to register %q driver: %w", nr.ntype, err)

+		}

 	}

+

+	return windows.RegisterBuiltinLocalDrivers(r, driverConfig)

 }