dhcpv6: proper DUID types

Signed-off-by: Chris Koch <chrisko@google.com>

17 files changed, 419 insertions, 326 deletions

diff --git a/dhcpv6/dhcpv6_test.go b/dhcpv6/dhcpv6_test.go
index b1f952d..210f19d 100644
--- a/dhcpv6/dhcpv6_test.go
+++ b/dhcpv6/dhcpv6_test.go
@@ -165,9 +165,9 @@ func TestNewAdvertiseFromSolicit(t *testing.T) {
 		MessageType:   MessageTypeSolicit,
 		TransactionID: TransactionID{0xa, 0xb, 0xc},
 	}
-	s.AddOption(OptClientID(Duid{}))
+	s.AddOption(OptClientID(&DUIDLLT{}))
 
-	a, err := NewAdvertiseFromSolicit(&s, WithServerID(Duid{}))
+	a, err := NewAdvertiseFromSolicit(&s, WithServerID(&DUIDLLT{}))
 	require.NoError(t, err)
 	require.Equal(t, a.TransactionID, s.TransactionID)
 	require.Equal(t, a.Type(), MessageTypeAdvertise)
@@ -178,35 +178,35 @@ func TestNewReplyFromMessage(t *testing.T) {
 		TransactionID: TransactionID{0xa, 0xb, 0xc},
 		MessageType:   MessageTypeConfirm,
 	}
-	var duid Duid
-	msg.AddOption(OptClientID(duid))
-	msg.AddOption(OptServerID(duid))
+	var duid DUIDLLT
+	msg.AddOption(OptClientID(&duid))
+	msg.AddOption(OptServerID(&duid))
 
-	rep, err := NewReplyFromMessage(&msg, WithServerID(duid))
+	rep, err := NewReplyFromMessage(&msg, WithServerID(&duid))
 	require.NoError(t, err)
 	require.Equal(t, rep.TransactionID, msg.TransactionID)
 	require.Equal(t, rep.Type(), MessageTypeReply)
 
 	msg.MessageType = MessageTypeRenew
-	rep, err = NewReplyFromMessage(&msg, WithServerID(duid))
+	rep, err = NewReplyFromMessage(&msg, WithServerID(&duid))
 	require.NoError(t, err)
 	require.Equal(t, rep.TransactionID, msg.TransactionID)
 	require.Equal(t, rep.Type(), MessageTypeReply)
 
 	msg.MessageType = MessageTypeRebind
-	rep, err = NewReplyFromMessage(&msg, WithServerID(duid))
+	rep, err = NewReplyFromMessage(&msg, WithServerID(&duid))
 	require.NoError(t, err)
 	require.Equal(t, rep.TransactionID, msg.TransactionID)
 	require.Equal(t, rep.Type(), MessageTypeReply)
 
 	msg.MessageType = MessageTypeRelease
-	rep, err = NewReplyFromMessage(&msg, WithServerID(duid))
+	rep, err = NewReplyFromMessage(&msg, WithServerID(&duid))
 	require.NoError(t, err)
 	require.Equal(t, rep.TransactionID, msg.TransactionID)
 	require.Equal(t, rep.Type(), MessageTypeReply)
 
 	msg.MessageType = MessageTypeInformationRequest
-	rep, err = NewReplyFromMessage(&msg, WithServerID(duid))
+	rep, err = NewReplyFromMessage(&msg, WithServerID(&duid))
 	require.NoError(t, err)
 	require.Equal(t, rep.TransactionID, msg.TransactionID)
 	require.Equal(t, rep.Type(), MessageTypeReply)
@@ -226,9 +226,8 @@ func TestNewMessageTypeSolicit(t *testing.T) {
 	hwAddr, err := net.ParseMAC("24:0A:9E:9F:EB:2B")
 	require.NoError(t, err)
 
-	duid := Duid{
-		Type:          DUID_LL,
-		HwType:        iana.HWTypeEthernet,
+	duid := &DUIDLL{
+		HWType:        iana.HWTypeEthernet,
 		LinkLayerAddr: hwAddr,
 	}
 
@@ -239,7 +238,7 @@ func TestNewMessageTypeSolicit(t *testing.T) {
 	// Check CID
 	cduid := s.Options.ClientID()
 	require.NotNil(t, cduid)
-	require.Equal(t, cduid, &duid)
+	require.Equal(t, cduid, duid)
 
 	// Check ORO
 	oro := s.Options.RequestedOptions()
diff --git a/dhcpv6/dhcpv6message.go b/dhcpv6/dhcpv6message.go
index 17f371a..8886c6c 100644
--- a/dhcpv6/dhcpv6message.go
+++ b/dhcpv6/dhcpv6message.go
@@ -32,21 +32,21 @@ func (mo MessageOptions) ArchTypes() iana.Archs {
 }
 
 // ClientID returns the client identifier option.
-func (mo MessageOptions) ClientID() *Duid {
+func (mo MessageOptions) ClientID() DUID {
 	opt := mo.GetOne(OptionClientID)
 	if opt == nil {
 		return nil
 	}
-	return &opt.(*optClientID).Duid
+	return opt.(*optClientID).DUID
 }
 
 // ServerID returns the server identifier option.
-func (mo MessageOptions) ServerID() *Duid {
+func (mo MessageOptions) ServerID() DUID {
 	opt := mo.GetOne(OptionServerID)
 	if opt == nil {
 		return nil
 	}
-	return &opt.(*optServerID).Duid
+	return opt.(*optServerID).DUID
 }
 
 // IANA returns all Identity Association for Non-temporary Address options.
@@ -347,9 +347,8 @@ func GetTime() uint32 {
 // NewSolicit creates a new SOLICIT message, using the given hardware address to
 // derive the IAID in the IA_NA option.
 func NewSolicit(hwaddr net.HardwareAddr, modifiers ...Modifier) (*Message, error) {
-	duid := Duid{
-		Type:          DUID_LLT,
-		HwType:        iana.HWTypeEthernet,
+	duid := &DUIDLLT{
+		HWType:        iana.HWTypeEthernet,
 		Time:          GetTime(),
 		LinkLayerAddr: hwaddr,
 	}
diff --git a/dhcpv6/dhcpv6relay_test.go b/dhcpv6/dhcpv6relay_test.go
index 113842c..1d38855 100644
--- a/dhcpv6/dhcpv6relay_test.go
+++ b/dhcpv6/dhcpv6relay_test.go
@@ -96,7 +96,7 @@ func TestNewRelayRepFromRelayForw(t *testing.T) {
 	// create the inner message
 	s, err := NewMessage()
 	require.NoError(t, err)
-	s.AddOption(OptClientID(Duid{}))
+	s.AddOption(OptClientID(&DUIDLL{}))
 	rf.AddOption(OptRelayMessage(s))
 
 	a, err := NewAdvertiseFromSolicit(s)
diff --git a/dhcpv6/duid.go b/dhcpv6/duid.go
index 2ae8e60..fcd785d 100644
--- a/dhcpv6/duid.go
+++ b/dhcpv6/duid.go
@@ -1,157 +1,242 @@
 package dhcpv6
 
 import (
-	"bytes"
-	"encoding/binary"
 	"fmt"
 	"net"
 
 	"github.com/insomniacslk/dhcp/iana"
+	"github.com/u-root/uio/uio"
 )
 
-// DuidType is the DUID type as defined in rfc3315.
-type DuidType uint16
+// DUID is the interface that all DUIDs adhere to.
+type DUID interface {
+	fmt.Stringer
+
+	ToBytes() []byte
+	FromBytes(p []byte) error
+	DUIDType() DUIDType
+}
+
+// DUIDLLT is a DUID based on link-layer address plus time (RFC 8415 Section 11.2).
+type DUIDLLT struct {
+	HWType        iana.HWType
+	Time          uint32
+	LinkLayerAddr net.HardwareAddr
+}
+
+// String pretty-prints DUIDLLT information.
+func (d DUIDLLT) String() string {
+	return fmt.Sprintf("DUID-LLT{HWType=%s HWAddr=%s Time=%d}", d.HWType, d.LinkLayerAddr, d.Time)
+}
+
+// DUIDType returns the DUID_LLT type.
+func (d DUIDLLT) DUIDType() DUIDType {
+	return DUID_LLT
+}
+
+// ToBytes serializes the option out to bytes.
+func (d DUIDLLT) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(uint16(d.DUIDType()))
+	buf.Write16(uint16(d.HWType))
+	buf.Write32(d.Time)
+	buf.WriteBytes(d.LinkLayerAddr)
+	return buf.Data()
+}
+
+// FromBytes reads the option.
+func (d *DUIDLLT) FromBytes(p []byte) error {
+	buf := uio.NewBigEndianBuffer(p)
+	d.HWType = iana.HWType(buf.Read16())
+	d.Time = buf.Read32()
+	d.LinkLayerAddr = buf.ReadAll()
+	return buf.FinError()
+}
+
+// DUIDLL is a DUID based on link-layer (RFC 8415 Section 11.4).
+type DUIDLL struct {
+	HWType        iana.HWType
+	LinkLayerAddr net.HardwareAddr
+}
+
+// String pretty-prints DUIDLL information.
+func (d DUIDLL) String() string {
+	return fmt.Sprintf("DUID-LL{HWType=%s HWAddr=%s}", d.HWType, d.LinkLayerAddr)
+}
+
+// DUIDType returns the DUID_LL type.
+func (d DUIDLL) DUIDType() DUIDType {
+	return DUID_LL
+}
+
+// ToBytes serializes the option out to bytes.
+func (d DUIDLL) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(uint16(d.DUIDType()))
+	buf.Write16(uint16(d.HWType))
+	buf.WriteBytes(d.LinkLayerAddr)
+	return buf.Data()
+}
+
+// FromBytes reads the option.
+func (d *DUIDLL) FromBytes(p []byte) error {
+	buf := uio.NewBigEndianBuffer(p)
+	d.HWType = iana.HWType(buf.Read16())
+	d.LinkLayerAddr = buf.ReadAll()
+	return buf.FinError()
+}
+
+// DUIDEN is a DUID based on enterprise number (RFC 8415 Section 11.3).
+type DUIDEN struct {
+	EnterpriseNumber     uint32
+	EnterpriseIdentifier []byte
+}
+
+// String pretty-prints DUIDEN information.
+func (d DUIDEN) String() string {
+	return fmt.Sprintf("DUID-EN{EnterpriseNumber=%d EnterpriseIdentifier=%s}", d.EnterpriseNumber, d.EnterpriseIdentifier)
+}
+
+// DUIDType returns the DUID_EN type.
+func (d DUIDEN) DUIDType() DUIDType {
+	return DUID_EN
+}
+
+// ToBytes serializes the option out to bytes.
+func (d DUIDEN) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(uint16(d.DUIDType()))
+	buf.Write32(d.EnterpriseNumber)
+	buf.WriteBytes(d.EnterpriseIdentifier)
+	return buf.Data()
+}
+
+// FromBytes reads the option.
+func (d *DUIDEN) FromBytes(p []byte) error {
+	buf := uio.NewBigEndianBuffer(p)
+	d.EnterpriseNumber = buf.Read32()
+	d.EnterpriseIdentifier = buf.ReadAll()
+	return buf.FinError()
+}
+
+// DUIDUUID is a DUID based on UUID (RFC 8415 Section 11.5).
+type DUIDUUID struct {
+	// Defined by RFC 6355.
+	UUID [16]byte
+}
+
+// String pretty-prints DUIDUUID information.
+func (d DUIDUUID) String() string {
+	return fmt.Sprintf("DUID-UUID{%#x}", d.UUID[:])
+}
+
+// DUIDType returns the DUID_UUID type.
+func (d DUIDUUID) DUIDType() DUIDType {
+	return DUID_UUID
+}
+
+// ToBytes serializes the option out to bytes.
+func (d DUIDUUID) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(uint16(d.DUIDType()))
+	buf.WriteData(d.UUID[:])
+	return buf.Data()
+}
+
+// FromBytes reads the option.
+func (d *DUIDUUID) FromBytes(p []byte) error {
+	if len(p) != 16 {
+		return fmt.Errorf("buffer is length %d, DUID-UUID must be exactly 16 bytes", len(p))
+	}
+	copy(d.UUID[:], p)
+	return nil
+}
+
+// Equal returns true if e is a DUID-UUID with the same values as d.
+func (d *DUIDUUID) Equal(e DUID) bool {
+	euuid, ok := e.(*DUIDUUID)
+	if !ok {
+		return false
+	}
+	return d.UUID == euuid.UUID
+}
+
+// DUIDOpaque is a DUID of unknown type.
+type DUIDOpaque struct {
+	Type DUIDType
+	Data []byte
+}
+
+// String pretty-prints opaque DUID information.
+func (d DUIDOpaque) String() string {
+	return fmt.Sprintf("DUID-Opaque{Type=%d Data=%#x}", d.Type, d.Data)
+}
+
+// DUIDType returns the opaque DUID type.
+func (d DUIDOpaque) DUIDType() DUIDType {
+	return d.Type
+}
+
+// ToBytes serializes the option out to bytes.
+func (d DUIDOpaque) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(uint16(d.Type))
+	buf.WriteData(d.Data)
+	return buf.Data()
+}
+
+// FromBytes reads the option.
+func (d *DUIDOpaque) FromBytes(p []byte) error {
+	d.Data = append([]byte(nil), p...)
+	return nil
+}
+
+// DUIDType is the DUID type as defined in RFC 3315.
+type DUIDType uint16
 
 // DUID types
 const (
-	DUID_LLT  DuidType = 1
-	DUID_EN   DuidType = 2
-	DUID_LL   DuidType = 3
-	DUID_UUID DuidType = 4
+	DUID_LLT  DUIDType = 1
+	DUID_EN   DUIDType = 2
+	DUID_LL   DUIDType = 3
+	DUID_UUID DUIDType = 4
 )
 
-// DuidTypeToString maps a DuidType to a name.
-var DuidTypeToString = map[DuidType]string{
+// duidTypeToString maps a DUIDType to a name.
+var duidTypeToString = map[DUIDType]string{
 	DUID_LL:   "DUID-LL",
 	DUID_LLT:  "DUID-LLT",
 	DUID_EN:   "DUID-EN",
 	DUID_UUID: "DUID-UUID",
 }
 
-func (d DuidType) String() string {
-	if dtype, ok := DuidTypeToString[d]; ok {
+func (d DUIDType) String() string {
+	if dtype, ok := duidTypeToString[d]; ok {
 		return dtype
 	}
-	return "Unknown"
-}
-
-// Duid is a DHCP Unique Identifier.
-type Duid struct {
-	Type                 DuidType
-	HwType               iana.HWType // for DUID-LLT and DUID-LL. Ignored otherwise. RFC 826
-	Time                 uint32      // for DUID-LLT. Ignored otherwise
-	LinkLayerAddr        net.HardwareAddr
-	EnterpriseNumber     uint32 // for DUID-EN. Ignored otherwise
-	EnterpriseIdentifier []byte // for DUID-EN. Ignored otherwise
-	Uuid                 []byte // for DUID-UUID. Ignored otherwise
-	Opaque               []byte // for unknown DUIDs
-}
-
-// Length returns the DUID length in bytes.
-func (d *Duid) Length() int {
-	if d.Type == DUID_LLT {
-		return 8 + len(d.LinkLayerAddr)
-	} else if d.Type == DUID_LL {
-		return 4 + len(d.LinkLayerAddr)
-	} else if d.Type == DUID_EN {
-		return 6 + len(d.EnterpriseIdentifier)
-	} else if d.Type == DUID_UUID {
-		return 18
-	} else {
-		return 2 + len(d.Opaque)
-	}
-}
-
-// Equal compares two Duid objects.
-func (d Duid) Equal(o Duid) bool {
-	if d.Type != o.Type ||
-		d.HwType != o.HwType ||
-		d.Time != o.Time ||
-		!bytes.Equal(d.LinkLayerAddr, o.LinkLayerAddr) ||
-		d.EnterpriseNumber != o.EnterpriseNumber ||
-		!bytes.Equal(d.EnterpriseIdentifier, o.EnterpriseIdentifier) ||
-		!bytes.Equal(d.Uuid, o.Uuid) ||
-		!bytes.Equal(d.Opaque, o.Opaque) {
-		return false
-	}
-	return true
-}
-
-// ToBytes serializes a Duid object.
-func (d *Duid) ToBytes() []byte {
-	if d.Type == DUID_LLT {
-		buf := make([]byte, 8)
-		binary.BigEndian.PutUint16(buf[0:2], uint16(d.Type))
-		binary.BigEndian.PutUint16(buf[2:4], uint16(d.HwType))
-		binary.BigEndian.PutUint32(buf[4:8], d.Time)
-		return append(buf, d.LinkLayerAddr...)
-	} else if d.Type == DUID_LL {
-		buf := make([]byte, 4)
-		binary.BigEndian.PutUint16(buf[0:2], uint16(d.Type))
-		binary.BigEndian.PutUint16(buf[2:4], uint16(d.HwType))
-		return append(buf, d.LinkLayerAddr...)
-	} else if d.Type == DUID_EN {
-		buf := make([]byte, 6)
-		binary.BigEndian.PutUint16(buf[0:2], uint16(d.Type))
-		binary.BigEndian.PutUint32(buf[2:6], d.EnterpriseNumber)
-		return append(buf, d.EnterpriseIdentifier...)
-	} else if d.Type == DUID_UUID {
-		buf := make([]byte, 2)
-		binary.BigEndian.PutUint16(buf[0:2], uint16(d.Type))
-		return append(buf, d.Uuid...)
-	} else {
-		buf := make([]byte, 2)
-		binary.BigEndian.PutUint16(buf[0:2], uint16(d.Type))
-		return append(buf, d.Opaque...)
-	}
+	return "unknown"
 }
 
-func (d *Duid) String() string {
-	var hwaddr string
-	if d.HwType == iana.HWTypeEthernet {
-		for _, b := range d.LinkLayerAddr {
-			hwaddr += fmt.Sprintf("%02x:", b)
-		}
-		if len(hwaddr) > 0 && hwaddr[len(hwaddr)-1] == ':' {
-			hwaddr = hwaddr[:len(hwaddr)-1]
-		}
+// DUIDFromBytes parses a DUID from a byte slice.
+func DUIDFromBytes(data []byte) (DUID, error) {
+	buf := uio.NewBigEndianBuffer(data)
+	if !buf.Has(2) {
+		return nil, fmt.Errorf("buffer too short: have %d bytes, want 2 bytes", buf.Len())
 	}
-	return fmt.Sprintf("DUID{type=%v hwtype=%v hwaddr=%v}", d.Type.String(), d.HwType.String(), hwaddr)
-}
 
-// DuidFromBytes parses a Duid from a byte slice.
-func DuidFromBytes(data []byte) (*Duid, error) {
-	if len(data) < 2 {
-		return nil, fmt.Errorf("Invalid DUID: shorter than 2 bytes")
-	}
-	d := Duid{}
-	d.Type = DuidType(binary.BigEndian.Uint16(data[0:2]))
-	if d.Type == DUID_LLT {
-		if len(data) < 8 {
-			return nil, fmt.Errorf("Invalid DUID-LLT: shorter than 8 bytes")
-		}
-		d.HwType = iana.HWType(binary.BigEndian.Uint16(data[2:4]))
-		d.Time = binary.BigEndian.Uint32(data[4:8])
-		d.LinkLayerAddr = data[8:]
-	} else if d.Type == DUID_LL {
-		if len(data) < 4 {
-			return nil, fmt.Errorf("Invalid DUID-LL: shorter than 4 bytes")
-		}
-		d.HwType = iana.HWType(binary.BigEndian.Uint16(data[2:4]))
-		d.LinkLayerAddr = data[4:]
-	} else if d.Type == DUID_EN {
-		if len(data) < 6 {
-			return nil, fmt.Errorf("Invalid DUID-EN: shorter than 6 bytes")
-		}
-		d.EnterpriseNumber = binary.BigEndian.Uint32(data[2:6])
-		d.EnterpriseIdentifier = data[6:]
-	} else if d.Type == DUID_UUID {
-		if len(data) != 18 {
-			return nil, fmt.Errorf("Invalid DUID-UUID length. Expected 18, got %v", len(data))
-		}
-		d.Uuid = data[2:18]
-	} else {
-		d.Opaque = data[2:]
+	typ := DUIDType(buf.Read16())
+	var d DUID
+	switch typ {
+	case DUID_LLT:
+		d = &DUIDLLT{}
+	case DUID_LL:
+		d = &DUIDLL{}
+	case DUID_EN:
+		d = &DUIDEN{}
+	case DUID_UUID:
+		d = &DUIDUUID{}
+	default:
+		d = &DUIDOpaque{Type: typ}
 	}
-	return &d, nil
+	return d, d.FromBytes(buf.Data())
 }
diff --git a/dhcpv6/duid_test.go b/dhcpv6/duid_test.go
index 5efa0e1..d035474 100644
--- a/dhcpv6/duid_test.go
+++ b/dhcpv6/duid_test.go
@@ -3,6 +3,7 @@ package dhcpv6
 import (
 	"bytes"
 	"net"
+	"reflect"
 	"testing"
 
 	"github.com/insomniacslk/dhcp/iana"
@@ -11,138 +12,127 @@ import (
 
 func TestDuidInvalidTooShort(t *testing.T) {
 	// too short DUID at all (must be at least 2 bytes)
-	_, err := DuidFromBytes([]byte{0})
+	_, err := DUIDFromBytes([]byte{0})
 	require.Error(t, err)
 
 	// too short DUID_LL (must be at least 4 bytes)
-	_, err = DuidFromBytes([]byte{0, 3, 0xa})
+	_, err = DUIDFromBytes([]byte{0, 3, 0xa})
 	require.Error(t, err)
 
 	// too short DUID_EN (must be at least 6 bytes)
-	_, err = DuidFromBytes([]byte{0, 2, 0xa, 0xb, 0xc})
+	_, err = DUIDFromBytes([]byte{0, 2, 0xa, 0xb, 0xc})
 	require.Error(t, err)
 
 	// too short DUID_LLT (must be at least 8 bytes)
-	_, err = DuidFromBytes([]byte{0, 1, 0xa, 0xb, 0xc, 0xd, 0xe})
+	_, err = DUIDFromBytes([]byte{0, 1, 0xa, 0xb, 0xc, 0xd, 0xe})
 	require.Error(t, err)
 
 	// too short DUID_UUID (must be at least 18 bytes)
-	_, err = DuidFromBytes([]byte{0, 4, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf})
+	_, err = DUIDFromBytes([]byte{0, 4, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf})
 	require.Error(t, err)
 }
 
-func TestDuidLLTFromBytes(t *testing.T) {
-	buf := []byte{
-		0, 1, // DUID_LLT
-		0, 1, // HwTypeEthernet
-		0x01, 0x02, 0x03, 0x04, // time
-		0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, // link-layer addr
-	}
-	duid, err := DuidFromBytes(buf)
-	require.NoError(t, err)
-	require.Equal(t, 14, duid.Length())
-	require.Equal(t, DUID_LLT, duid.Type)
-	require.Equal(t, uint32(0x01020304), duid.Time)
-	require.Equal(t, iana.HWTypeEthernet, duid.HwType)
-	require.Equal(t, net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}, duid.LinkLayerAddr)
-}
+func TestFromBytes(t *testing.T) {
+	for _, tt := range []struct {
+		name     string
+		buf      []byte
+		want     DUID
+		stringer string
+	}{
+		{
+			name: "DUID-LLT",
+			buf: []byte{
+				0, 1, // DUID_LLT
+				0, 1, // HwTypeEthernet
+				0x01, 0x02, 0x03, 0x04, // time
+				0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, // link-layer addr
+			},
+			want: &DUIDLLT{
+				Time:          0x01020304,
+				HWType:        iana.HWTypeEthernet,
+				LinkLayerAddr: net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
+			},
+			stringer: "DUID-LLT{HWType=Ethernet HWAddr=aa:bb:cc:dd:ee:ff Time=16909060}",
+		},
+		{
+			name: "DUID-LL",
+			buf: []byte{
+				0, 3, // DUID_LL
+				0, 1, // HwTypeEthernet
+				0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, // link-layer addr
+			},
+			want: &DUIDLL{
+				HWType:        iana.HWTypeEthernet,
+				LinkLayerAddr: net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
+			},
+			stringer: "DUID-LL{HWType=Ethernet HWAddr=aa:bb:cc:dd:ee:ff}",
+		},
+		{
+			name: "DUID-EN",
+			buf: []byte{
+				0, 2, // DUID_EN
+				0, 0, 0, 1, // EnterpriseNumber
+				0x66, 0x6f, 0x6f, // "foo"
+			},
+			want: &DUIDEN{
+				EnterpriseNumber:     0x1,
+				EnterpriseIdentifier: []byte("foo"),
+			},
+			stringer: "DUID-EN{EnterpriseNumber=1 EnterpriseIdentifier=foo}",
+		},
+		{
+			name: "DUID-UUID",
+			buf: []byte{
+				0x00, 0x04, // DUID_UUID
+				0x01, 0x02, 0x03, 0x04, // UUID
+				0x01, 0x02, 0x03, 0x04, // UUID
+				0x01, 0x02, 0x03, 0x04, // UUID
+				0x01, 0x02, 0x03, 0x04, // UUID
+			},
+			want: &DUIDUUID{
+				UUID: [16]byte{
+					0x01, 0x02, 0x03, 0x04,
+					0x01, 0x02, 0x03, 0x04,
+					0x01, 0x02, 0x03, 0x04,
+					0x01, 0x02, 0x03, 0x04,
+				},
+			},
+			stringer: "DUID-UUID{0x01020304010203040102030401020304}",
+		},
+		{
+			name: "DUIDOpaque",
+			buf: []byte{
+				0x00, 0x05, // unknown DUID
+				0x01, 0x02, 0x03, // Opaque
+			},
+			want: &DUIDOpaque{
+				Type: 0x5,
+				Data: []byte{0x01, 0x02, 0x03},
+			},
+			stringer: "DUID-Opaque{Type=5 Data=0x010203}",
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			// FromBytes
+			got, err := DUIDFromBytes(tt.buf)
+			if err != nil {
+				t.Errorf("DUIDFromBytes = %v", err)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("DUIDFromBytes = %v, want %v", got, tt.want)
+			}
 
-func TestDuidLLFromBytes(t *testing.T) {
-	buf := []byte{
-		0, 3, // DUID_LL
-		0, 1, // HwTypeEthernet
-		0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, // link-layer addr
-	}
-	duid, err := DuidFromBytes(buf)
-	require.NoError(t, err)
-	require.Equal(t, 10, duid.Length())
-	require.Equal(t, DUID_LL, duid.Type)
-	require.Equal(t, iana.HWTypeEthernet, duid.HwType)
-	require.Equal(t, net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}, duid.LinkLayerAddr)
-}
-
-func TestDuidUuidFromBytes(t *testing.T) {
-	buf := []byte{
-		0x00, 0x04, // DUID_UUID
-	}
-	uuid := []byte{0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04, 0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08}
-	buf = append(buf, uuid...)
-	duid, err := DuidFromBytes(buf)
-	require.NoError(t, err)
-	require.Equal(t, 18, duid.Length())
-	require.Equal(t, DUID_UUID, duid.Type)
-	require.Equal(t, uuid, duid.Uuid)
-}
+			// ToBytes
+			buf := tt.want.ToBytes()
+			if !bytes.Equal(buf, tt.buf) {
+				t.Errorf("ToBytes() = %#x, want %#x", buf, tt.buf)
+			}
 
-func TestDuidLLTToBytes(t *testing.T) {
-	expected := []byte{
-		0, 1, // DUID_LLT
-		0, 1, // HwTypeEthernet
-		0x01, 0x02, 0x03, 0x04, // time
-		0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, // link-layer addr
-	}
-	duid := Duid{
-		Type:          DUID_LLT,
-		HwType:        iana.HWTypeEthernet,
-		Time:          uint32(0x01020304),
-		LinkLayerAddr: []byte{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
-	}
-	toBytes := duid.ToBytes()
-	require.Equal(t, expected, toBytes)
-}
-
-func TestDuidUuidToBytes(t *testing.T) {
-	uuid := []byte{0x00, 0x02, 0x00, 0x03, 0x00, 0x04, 0x00, 0x05, 0x00, 0x06, 0x00, 0x07, 0x00, 0x08, 0x00, 0x09}
-	expected := []byte{00, 04}
-	expected = append(expected, uuid...)
-	duid := Duid{
-		Type: DUID_UUID,
-		Uuid: uuid,
-	}
-	toBytes := duid.ToBytes()
-	if !bytes.Equal(toBytes, expected) {
-		t.Fatalf("Invalid ToBytes result. Expected %v, got %v", expected, toBytes)
-	}
-}
-
-func TestOpaqueDuid(t *testing.T) {
-	duid := []byte("\x00\x0a\x00\x03\x00\x01\x4c\x5e\x0c\x43\xbf\x39")
-	d, err := DuidFromBytes(duid)
-	if err != nil {
-		t.Fatalf("DuidFromBytes: unexpected error: %v", err)
-	}
-	if got, want := d.Length(), len(duid); got != want {
-		t.Errorf("Length: unexpected result: got %d, want %d", got, want)
-	}
-	if got, want := d.ToBytes(), duid; !bytes.Equal(got, want) {
-		t.Fatalf("ToBytes: unexpected result: got %x, want %x", got, want)
-	}
-}
-
-func TestDuidEqual(t *testing.T) {
-	d := Duid{
-		Type:          DUID_LL,
-		HwType:        iana.HWTypeEthernet,
-		LinkLayerAddr: net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
-	}
-	o := Duid{
-		Type:          DUID_LL,
-		HwType:        iana.HWTypeEthernet,
-		LinkLayerAddr: net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
-	}
-	require.True(t, d.Equal(o))
-}
-
-func TestDuidEqualNotEqual(t *testing.T) {
-	d := Duid{
-		Type:          DUID_LL,
-		HwType:        iana.HWTypeEthernet,
-		LinkLayerAddr: net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
-	}
-	o := Duid{
-		Type:          DUID_LL,
-		HwType:        iana.HWTypeEthernet,
-		LinkLayerAddr: net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0x00},
+			// Stringer
+			s := tt.want.String()
+			if s != tt.stringer {
+				t.Errorf("String() = %s, want %s", s, tt.stringer)
+			}
+		})
 	}
-	require.False(t, d.Equal(o))
 }
diff --git a/dhcpv6/iputils.go b/dhcpv6/iputils.go
index d2cac47..c4926e1 100644
--- a/dhcpv6/iputils.go
+++ b/dhcpv6/iputils.go
@@ -90,8 +90,15 @@ func ExtractMAC(packet DHCPv6) (net.HardwareAddr, error) {
 	if duid == nil {
 		return nil, fmt.Errorf("client ID not found in packet")
 	}
-	if duid.LinkLayerAddr == nil {
-		return nil, fmt.Errorf("failed to extract MAC")
+	switch d := duid.(type) {
+	case *DUIDLL:
+		if d.LinkLayerAddr != nil {
+			return d.LinkLayerAddr, nil
+		}
+	case *DUIDLLT:
+		if d.LinkLayerAddr != nil {
+			return d.LinkLayerAddr, nil
+		}
 	}
-	return duid.LinkLayerAddr, nil
+	return nil, fmt.Errorf("failed to extract MAC")
 }
diff --git a/dhcpv6/iputils_test.go b/dhcpv6/iputils_test.go
index e206aa1..601e96e 100644
--- a/dhcpv6/iputils_test.go
+++ b/dhcpv6/iputils_test.go
@@ -131,10 +131,9 @@ func Test_ExtractMAC(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, mac.String(), "24:8a:07:56:dc:a4")
 
-	// MAC extracted from DUID
-	duid := Duid{
-		Type:          DUID_LL,
-		HwType:        iana.HWTypeEthernet,
+	// MAC extracted from DUID-LL
+	duid := &DUIDLL{
+		HWType:        iana.HWTypeEthernet,
 		LinkLayerAddr: []byte{0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa},
 	}
 	solicit, err := NewMessage(WithClientID(duid))
@@ -145,6 +144,18 @@ func Test_ExtractMAC(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, mac.String(), "aa:aa:aa:aa:aa:aa")
 
+	// MAC extracted from DUID-LLT
+	solicit, err = NewMessage(WithClientID(&DUIDLLT{
+		HWType:        iana.HWTypeEthernet,
+		LinkLayerAddr: []byte{0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa},
+	}))
+	require.NoError(t, err)
+	relay, err = EncapsulateRelay(solicit, MessageTypeRelayForward, net.IPv6zero, net.IPv6zero)
+	require.NoError(t, err)
+	mac, err = ExtractMAC(relay)
+	require.NoError(t, err)
+	require.Equal(t, mac.String(), "aa:aa:aa:aa:aa:aa")
+
 	// no client ID
 	solicit, err = NewMessage()
 	require.NoError(t, err)
@@ -152,8 +163,8 @@ func Test_ExtractMAC(t *testing.T) {
 	require.Error(t, err)
 
 	// DUID is not DuidLL or DuidLLT
-	duid = Duid{}
-	solicit, err = NewMessage(WithClientID(duid))
+	duiden := &DUIDEN{}
+	solicit, err = NewMessage(WithClientID(duiden))
 	require.NoError(t, err)
 	_, err = ExtractMAC(solicit)
 	require.Error(t, err)
diff --git a/dhcpv6/modifiers.go b/dhcpv6/modifiers.go
index 1d8c49f..b0d22c5 100644
--- a/dhcpv6/modifiers.go
+++ b/dhcpv6/modifiers.go
@@ -16,12 +16,12 @@ func WithOption(o Option) Modifier {
 }
 
 // WithClientID adds a client ID option to a DHCPv6 packet
-func WithClientID(duid Duid) Modifier {
+func WithClientID(duid DUID) Modifier {
 	return WithOption(OptClientID(duid))
 }
 
 // WithServerID adds a client ID option to a DHCPv6 packet
-func WithServerID(duid Duid) Modifier {
+func WithServerID(duid DUID) Modifier {
 	return WithOption(OptServerID(duid))
 }
 
diff --git a/dhcpv6/modifiers_test.go b/dhcpv6/modifiers_test.go
index c0b8139..322d4e3 100644
--- a/dhcpv6/modifiers_test.go
+++ b/dhcpv6/modifiers_test.go
@@ -10,27 +10,25 @@ import (
 )
 
 func TestWithClientID(t *testing.T) {
-	duid := Duid{
-		Type:          DUID_LL,
-		HwType:        iana.HWTypeEthernet,
+	duid := &DUIDLL{
+		HWType:        iana.HWTypeEthernet,
 		LinkLayerAddr: net.HardwareAddr([]byte{0xfa, 0xce, 0xb0, 0x00, 0x00, 0x0c}),
 	}
 	m, err := NewMessage(WithClientID(duid))
 	require.NoError(t, err)
 	cid := m.Options.ClientID()
-	require.Equal(t, cid, &duid)
+	require.Equal(t, cid, duid)
 }
 
 func TestWithServerID(t *testing.T) {
-	duid := Duid{
-		Type:          DUID_LL,
-		HwType:        iana.HWTypeEthernet,
+	duid := &DUIDLL{
+		HWType:        iana.HWTypeEthernet,
 		LinkLayerAddr: net.HardwareAddr([]byte{0xfa, 0xce, 0xb0, 0x00, 0x00, 0x0c}),
 	}
 	m, err := NewMessage(WithServerID(duid))
 	require.NoError(t, err)
 	sid := m.Options.ServerID()
-	require.Equal(t, sid, &duid)
+	require.Equal(t, sid, duid)
 }
 
 func TestWithRequestedOptions(t *testing.T) {
diff --git a/dhcpv6/option_clientid.go b/dhcpv6/option_clientid.go
index d08f6d3..d07c4d5 100644
--- a/dhcpv6/option_clientid.go
+++ b/dhcpv6/option_clientid.go
@@ -6,12 +6,12 @@ import (
 
 // OptClientID represents a Client Identifier option as defined by RFC 3315
 // Section 22.2.
-func OptClientID(d Duid) Option {
+func OptClientID(d DUID) Option {
 	return &optClientID{d}
 }
 
 type optClientID struct {
-	Duid
+	DUID
 }
 
 func (*optClientID) Code() OptionCode {
@@ -19,16 +19,16 @@ func (*optClientID) Code() OptionCode {
 }
 
 func (op *optClientID) String() string {
-	return fmt.Sprintf("%s: %s", op.Code(), op.Duid.String())
+	return fmt.Sprintf("%s: %s", op.Code(), op.DUID)
 }
 
 // parseOptClientID builds an OptClientId structure from a sequence
 // of bytes. The input data does not include option code and length
 // bytes.
 func parseOptClientID(data []byte) (*optClientID, error) {
-	cid, err := DuidFromBytes(data)
+	cid, err := DUIDFromBytes(data)
 	if err != nil {
 		return nil, err
 	}
-	return &optClientID{*cid}, nil
+	return &optClientID{cid}, nil
 }
diff --git a/dhcpv6/option_clientid_test.go b/dhcpv6/option_clientid_test.go
index f60356e..0bac410 100644
--- a/dhcpv6/option_clientid_test.go
+++ b/dhcpv6/option_clientid_test.go
@@ -16,16 +16,19 @@ func TestParseOptClientID(t *testing.T) {
 	}
 	opt, err := parseOptClientID(data)
 	require.NoError(t, err)
-	require.Equal(t, DUID_LL, opt.Type)
-	require.Equal(t, iana.HWTypeEthernet, opt.HwType)
-	require.Equal(t, net.HardwareAddr([]byte{0, 1, 2, 3, 4, 5}), opt.LinkLayerAddr)
+	want := OptClientID(
+		&DUIDLL{
+			HWType:        iana.HWTypeEthernet,
+			LinkLayerAddr: net.HardwareAddr([]byte{0, 1, 2, 3, 4, 5}),
+		},
+	)
+	require.Equal(t, want, opt)
 }
 
 func TestOptClientIdToBytes(t *testing.T) {
 	opt := OptClientID(
-		Duid{
-			Type:          DUID_LL,
-			HwType:        iana.HWTypeEthernet,
+		&DUIDLL{
+			HWType:        iana.HWTypeEthernet,
 			LinkLayerAddr: net.HardwareAddr([]byte{5, 4, 3, 2, 1, 0}),
 		},
 	)
@@ -50,9 +53,8 @@ func TestOptClientIdDecodeEncode(t *testing.T) {
 
 func TestOptionClientId(t *testing.T) {
 	opt := OptClientID(
-		Duid{
-			Type:          DUID_LL,
-			HwType:        iana.HWTypeEthernet,
+		&DUIDLL{
+			HWType:        iana.HWTypeEthernet,
 			LinkLayerAddr: net.HardwareAddr([]byte{0xde, 0xad, 0, 0, 0xbe, 0xef}),
 		},
 	)
@@ -60,7 +62,7 @@ func TestOptionClientId(t *testing.T) {
 	require.Contains(
 		t,
 		opt.String(),
-		"Client ID: DUID{type=DUID-LL hwtype=Ethernet hwaddr=de:ad:00:00:be:ef}",
+		"Client ID: DUID-LL{HWType=Ethernet HWAddr=de:ad:00:00:be:ef}",
 		"String() should contain the correct cid output",
 	)
 }
diff --git a/dhcpv6/option_serverid.go b/dhcpv6/option_serverid.go
index b461e8d..bdfc290 100644
--- a/dhcpv6/option_serverid.go
+++ b/dhcpv6/option_serverid.go
@@ -6,12 +6,12 @@ import (
 
 // OptServerID represents a Server Identifier option as defined by RFC 3315
 // Section 22.1.
-func OptServerID(d Duid) Option {
+func OptServerID(d DUID) Option {
 	return &optServerID{d}
 }
 
 type optServerID struct {
-	Duid
+	DUID
 }
 
 func (*optServerID) Code() OptionCode {
@@ -19,15 +19,15 @@ func (*optServerID) Code() OptionCode {
 }
 
 func (op *optServerID) String() string {
-	return fmt.Sprintf("%s: %v", op.Code(), op.Duid.String())
+	return fmt.Sprintf("%s: %v", op.Code(), op.DUID)
 }
 
 // parseOptServerID builds an optServerID structure from a sequence of bytes.
 // The input data does not include option code and length bytes.
 func parseOptServerID(data []byte) (*optServerID, error) {
-	sid, err := DuidFromBytes(data)
+	sid, err := DUIDFromBytes(data)
 	if err != nil {
 		return nil, err
 	}
-	return &optServerID{*sid}, nil
+	return &optServerID{sid}, nil
 }
diff --git a/dhcpv6/option_serverid_test.go b/dhcpv6/option_serverid_test.go
index 0e5cb2f..556f515 100644
--- a/dhcpv6/option_serverid_test.go
+++ b/dhcpv6/option_serverid_test.go
@@ -16,16 +16,19 @@ func TestParseOptServerID(t *testing.T) {
 	}
 	opt, err := parseOptServerID(data)
 	require.NoError(t, err)
-	require.Equal(t, DUID_LL, opt.Type)
-	require.Equal(t, iana.HWTypeEthernet, opt.HwType)
-	require.Equal(t, net.HardwareAddr{0, 1, 2, 3, 4, 5}, opt.LinkLayerAddr)
+	want := OptServerID(
+		&DUIDLL{
+			HWType:        iana.HWTypeEthernet,
+			LinkLayerAddr: net.HardwareAddr{0, 1, 2, 3, 4, 5},
+		},
+	)
+	require.Equal(t, opt, want)
 }
 
 func TestOptServerIdToBytes(t *testing.T) {
 	opt := OptServerID(
-		Duid{
-			Type:          DUID_LL,
-			HwType:        iana.HWTypeEthernet,
+		&DUIDLL{
+			HWType:        iana.HWTypeEthernet,
 			LinkLayerAddr: net.HardwareAddr{5, 4, 3, 2, 1, 0},
 		},
 	)
@@ -50,9 +53,8 @@ func TestOptServerIdDecodeEncode(t *testing.T) {
 
 func TestOptionServerId(t *testing.T) {
 	opt := OptServerID(
-		Duid{
-			Type:          DUID_LL,
-			HwType:        iana.HWTypeEthernet,
+		&DUIDLL{
+			HWType:        iana.HWTypeEthernet,
 			LinkLayerAddr: net.HardwareAddr{0xde, 0xad, 0, 0, 0xbe, 0xef},
 		},
 	)
@@ -60,7 +62,7 @@ func TestOptionServerId(t *testing.T) {
 	require.Contains(
 		t,
 		opt.String(),
-		"Server ID: DUID{type=DUID-LL hwtype=Ethernet hwaddr=de:ad:00:00:be:ef}",
+		"Server ID: DUID-LL{HWType=Ethernet HWAddr=de:ad:00:00:be:ef}",
 		"String() should contain the correct sid output",
 	)
 }
diff --git a/dhcpv6/prettyprint_test.go b/dhcpv6/prettyprint_test.go
index 7b839ef..def212c 100644
--- a/dhcpv6/prettyprint_test.go
+++ b/dhcpv6/prettyprint_test.go
@@ -73,7 +73,7 @@ func TestPrint(t *testing.T) {
 		WithOption(OptRelayPort(1026)),
 		WithOption(&OptRemoteID{EnterpriseNumber: 300, RemoteID: []byte{0xde, 0xad, 0xbe, 0xed}}),
 		WithOption(OptRequestedOption(OptionBootfileURL, OptionBootfileParam)),
-		WithOption(OptServerID(Duid{Type: DUID_LL, HwType: iana.HWTypeEthernet, LinkLayerAddr: net.HardwareAddr{0x1, 0x2, 0x3, 0x4, 0x5, 0x6}})),
+		WithOption(OptServerID(&DUIDLL{HWType: iana.HWTypeEthernet, LinkLayerAddr: net.HardwareAddr{0x1, 0x2, 0x3, 0x4, 0x5, 0x6}})),
 		WithOption(&OptUserClass{[][]byte{[]byte("foo"), []byte("bar")}}),
 		WithOption(oneiana),
 		WithOption(oneiata),
diff --git a/dhcpv6/ztpv6/parse_vendor_options.go b/dhcpv6/ztpv6/parse_vendor_options.go
index b3ce55b..f1508fd 100644
--- a/dhcpv6/ztpv6/parse_vendor_options.go
+++ b/dhcpv6/ztpv6/parse_vendor_options.go
@@ -81,10 +81,12 @@ func ParseVendorData(packet dhcpv6.DHCPv6) (*VendorData, error) {
 			if len(v) < 3 {
 				return nil, errVendorOptionMalformed
 			}
-			duid := packet.(*dhcpv6.Message).Options.ClientID()
 			vd.VendorName = iana.EnterpriseIDCienaCorporation.String()
 			vd.Model = v[1] + "-" + v[2]
-			vd.Serial = string(duid.EnterpriseIdentifier)
+			duid := packet.(*dhcpv6.Message).Options.ClientID()
+			if enterpriseDUID, ok := duid.(*dhcpv6.DUIDEN); ok {
+				vd.Serial = string(enterpriseDUID.EnterpriseIdentifier)
+			}
 			return &vd, nil
 		}
 	}
diff --git a/dhcpv6/ztpv6/parse_vendor_options_test.go b/dhcpv6/ztpv6/parse_vendor_options_test.go
index 03ff8cf..cfbfdde 100644
--- a/dhcpv6/ztpv6/parse_vendor_options_test.go
+++ b/dhcpv6/ztpv6/parse_vendor_options_test.go
@@ -64,7 +64,7 @@ func TestParseVendorDataWithVendorClass(t *testing.T) {
 	tt := []struct {
 		name     string
 		vc       string
-		clientId *dhcpv6.Duid
+		clientId dhcpv6.DUID
 		want     *VendorData
 		fail     bool
 	}{
@@ -84,8 +84,7 @@ func TestParseVendorDataWithVendorClass(t *testing.T) {
 		{
 			name: "Ciena",
 			vc:   "1271-23422Z11-123",
-			clientId: &dhcpv6.Duid{
-				Type:                 dhcpv6.DUID_EN,
+			clientId: &dhcpv6.DUIDEN{
 				EnterpriseIdentifier: []byte("001234567"),
 			},
 			want: &VendorData{VendorName: iana.EnterpriseIDCienaCorporation.String(), Model: "23422Z11-123", Serial: "001234567"},
@@ -102,7 +101,7 @@ func TestParseVendorDataWithVendorClass(t *testing.T) {
 			packet.AddOption(&dhcpv6.OptVendorClass{
 				EnterpriseNumber: 0000, Data: [][]byte{[]byte(tc.vc)}})
 			if tc.clientId != nil {
-				packet.AddOption(dhcpv6.OptClientID(*tc.clientId))
+				packet.AddOption(dhcpv6.OptClientID(tc.clientId))
 			}
 			vd, err := ParseVendorData(packet)
 			if err != nil && !tc.fail {
diff --git a/examples/packetcrafting6/main.go b/examples/packetcrafting6/main.go
index f2c1855..13e1c22 100644
--- a/examples/packetcrafting6/main.go
+++ b/examples/packetcrafting6/main.go
@@ -41,9 +41,8 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
-	duid := dhcpv6.Duid{
-		Type:          dhcpv6.DUID_LLT,
-		HwType:        iana.HWTypeEthernet,
+	duid := &dhcpv6.DUIDLLT{
+		HWType:        iana.HWTypeEthernet,
 		Time:          dhcpv6.GetTime(),
 		LinkLayerAddr: mac,
 	}