Refactor expr for obj reimplementation (#265)

Added marshalData func to expressions
Prepare parseexprfunc for obj implementation refactor

related to #253

expr/bitwise.go

@@ -31,6 +31,17 @@ type Bitwise struct {
 }
 
 func (e *Bitwise) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("bitwise\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Bitwise) marshalData(fam byte) ([]byte, error) {
 	mask, err := netlink.MarshalAttributes([]netlink.Attribute{
 		{Type: unix.NFTA_DATA_VALUE, Data: e.Mask},
 	})
@@ -44,20 +55,13 @@ func (e *Bitwise) marshal(fam byte) ([]byte, error) {
 		return nil, err
 	}
 
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	return netlink.MarshalAttributes([]netlink.Attribute{
 		{Type: unix.NFTA_BITWISE_SREG, Data: binaryutil.BigEndian.PutUint32(e.SourceRegister)},
 		{Type: unix.NFTA_BITWISE_DREG, Data: binaryutil.BigEndian.PutUint32(e.DestRegister)},
 		{Type: unix.NFTA_BITWISE_LEN, Data: binaryutil.BigEndian.PutUint32(e.Len)},
 		{Type: unix.NLA_F_NESTED | unix.NFTA_BITWISE_MASK, Data: mask},
 		{Type: unix.NLA_F_NESTED | unix.NFTA_BITWISE_XOR, Data: xor},
 	})
-	if err != nil {
-		return nil, err
-	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("bitwise\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Bitwise) unmarshal(fam byte, data []byte) error {

expr/byteorder.go

@@ -38,13 +38,7 @@ type Byteorder struct {
 }
 
 func (e *Byteorder) marshal(fam byte) ([]byte, error) {
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	data, err := e.marshalData(fam)
-		{Type: unix.NFTA_BYTEORDER_SREG, Data: binaryutil.BigEndian.PutUint32(e.SourceRegister)},
-		{Type: unix.NFTA_BYTEORDER_DREG, Data: binaryutil.BigEndian.PutUint32(e.DestRegister)},
-		{Type: unix.NFTA_BYTEORDER_OP, Data: binaryutil.BigEndian.PutUint32(uint32(e.Op))},
-		{Type: unix.NFTA_BYTEORDER_LEN, Data: binaryutil.BigEndian.PutUint32(e.Len)},
-		{Type: unix.NFTA_BYTEORDER_SIZE, Data: binaryutil.BigEndian.PutUint32(e.Size)},
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -54,6 +48,16 @@ func (e *Byteorder) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Byteorder) marshalData(fam byte) ([]byte, error) {
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_BYTEORDER_SREG, Data: binaryutil.BigEndian.PutUint32(e.SourceRegister)},
+		{Type: unix.NFTA_BYTEORDER_DREG, Data: binaryutil.BigEndian.PutUint32(e.DestRegister)},
+		{Type: unix.NFTA_BYTEORDER_OP, Data: binaryutil.BigEndian.PutUint32(uint32(e.Op))},
+		{Type: unix.NFTA_BYTEORDER_LEN, Data: binaryutil.BigEndian.PutUint32(e.Len)},
+		{Type: unix.NFTA_BYTEORDER_SIZE, Data: binaryutil.BigEndian.PutUint32(e.Size)},
+	})
+}
+
 func (e *Byteorder) unmarshal(fam byte, data []byte) error {
 	return fmt.Errorf("not yet implemented")
 }

expr/connlimit.go

@@ -37,10 +37,7 @@ type Connlimit struct {
 }
 
 func (e *Connlimit) marshal(fam byte) ([]byte, error) {
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	data, err := e.marshalData(fam)
-		{Type: NFTA_CONNLIMIT_COUNT, Data: binaryutil.BigEndian.PutUint32(e.Count)},
-		{Type: NFTA_CONNLIMIT_FLAGS, Data: binaryutil.BigEndian.PutUint32(e.Flags)},
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -51,6 +48,13 @@ func (e *Connlimit) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Connlimit) marshalData(fam byte) ([]byte, error) {
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: NFTA_CONNLIMIT_COUNT, Data: binaryutil.BigEndian.PutUint32(e.Count)},
+		{Type: NFTA_CONNLIMIT_FLAGS, Data: binaryutil.BigEndian.PutUint32(e.Flags)},
+	})
+}
+
 func (e *Connlimit) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {

expr/counter.go

@@ -28,10 +28,7 @@ type Counter struct {
 }
 
 func (e *Counter) marshal(fam byte) ([]byte, error) {
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	data, err := e.marshalData(fam)
-		{Type: unix.NFTA_COUNTER_BYTES, Data: binaryutil.BigEndian.PutUint64(e.Bytes)},
-		{Type: unix.NFTA_COUNTER_PACKETS, Data: binaryutil.BigEndian.PutUint64(e.Packets)},
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -42,6 +39,13 @@ func (e *Counter) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Counter) marshalData(fam byte) ([]byte, error) {
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_COUNTER_BYTES, Data: binaryutil.BigEndian.PutUint64(e.Bytes)},
+		{Type: unix.NFTA_COUNTER_PACKETS, Data: binaryutil.BigEndian.PutUint64(e.Packets)},
+	})
+}
+
 func (e *Counter) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {

expr/ct.go

@@ -64,7 +64,19 @@ type Ct struct {
 }
 
 func (e *Ct) marshal(fam byte) ([]byte, error) {
-	regData := []byte{}
+	exprData, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("ct\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: exprData},
+	})
+}
+
+func (e *Ct) marshalData(fam byte) ([]byte, error) {
+	var regData []byte
 	exprData, err := netlink.MarshalAttributes(
 		[]netlink.Attribute{
 			{Type: unix.NFTA_CT_KEY, Data: binaryutil.BigEndian.PutUint32(uint32(e.Key))},
@@ -90,11 +102,7 @@ func (e *Ct) marshal(fam byte) ([]byte, error) {
 		return nil, err
 	}
 	exprData = append(exprData, regData...)
-
+	return exprData, nil
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("ct\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: exprData},
-	})
 }
 
 func (e *Ct) unmarshal(fam byte, data []byte) error {

expr/dup.go

@@ -29,16 +29,7 @@ type Dup struct {
 }
 
 func (e *Dup) marshal(fam byte) ([]byte, error) {
-	attrs := []netlink.Attribute{
+	data, err := e.marshalData(fam)
-		{Type: unix.NFTA_DUP_SREG_ADDR, Data: binaryutil.BigEndian.PutUint32(e.RegAddr)},
-	}
-
-	if e.IsRegDevSet {
-		attrs = append(attrs, netlink.Attribute{Type: unix.NFTA_DUP_SREG_DEV, Data: binaryutil.BigEndian.PutUint32(e.RegDev)})
-	}
-
-	data, err := netlink.MarshalAttributes(attrs)
-
 	if err != nil {
 		return nil, err
 	}
@@ -49,6 +40,18 @@ func (e *Dup) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Dup) marshalData(fam byte) ([]byte, error) {
+	attrs := []netlink.Attribute{
+		{Type: unix.NFTA_DUP_SREG_ADDR, Data: binaryutil.BigEndian.PutUint32(e.RegAddr)},
+	}
+
+	if e.IsRegDevSet {
+		attrs = append(attrs, netlink.Attribute{Type: unix.NFTA_DUP_SREG_DEV, Data: binaryutil.BigEndian.PutUint32(e.RegDev)})
+	}
+
+	return netlink.MarshalAttributes(attrs)
+}
+
 func (e *Dup) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {

expr/dynset.go

@@ -44,6 +44,18 @@ type Dynset struct {
 }
 
 func (e *Dynset) marshal(fam byte) ([]byte, error) {
+	opData, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("dynset\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: opData},
+	})
+}
+
+func (e *Dynset) marshalData(fam byte) ([]byte, error) {
 	// See: https://git.netfilter.org/libnftnl/tree/src/expr/dynset.c
 	var opAttrs []netlink.Attribute
 	opAttrs = append(opAttrs, netlink.Attribute{Type: unix.NFTA_DYNSET_SREG_KEY, Data: binaryutil.BigEndian.PutUint32(e.SrcRegKey)})
@@ -89,17 +101,9 @@ func (e *Dynset) marshal(fam byte) ([]byte, error) {
 			opAttrs = append(opAttrs, netlink.Attribute{Type: NFTA_DYNSET_EXPRESSIONS, Data: elemData})
 		}
 	}
+
 	opAttrs = append(opAttrs, netlink.Attribute{Type: unix.NFTA_DYNSET_FLAGS, Data: binaryutil.BigEndian.PutUint32(flags)})
-
+	return netlink.MarshalAttributes(opAttrs)
-	opData, err := netlink.MarshalAttributes(opAttrs)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("dynset\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: opData},
-	})
 }
 
 func (e *Dynset) unmarshal(fam byte, data []byte) error {
@@ -125,7 +129,7 @@ func (e *Dynset) unmarshal(fam byte, data []byte) error {
 		case unix.NFTA_DYNSET_FLAGS:
 			e.Invert = (ad.Uint32() & unix.NFT_DYNSET_F_INV) != 0
 		case unix.NFTA_DYNSET_EXPR:
-			exprs, err := parseexprfunc.ParseExprBytesFunc(fam, ad, ad.Bytes())
+			exprs, err := parseexprfunc.ParseExprBytesFunc(fam, ad)
 			if err != nil {
 				return err
 			}

expr/expr.go

@@ -25,8 +25,8 @@ import (
 )
 
 func init() {
-	parseexprfunc.ParseExprBytesFunc = func(fam byte, ad *netlink.AttributeDecoder, b []byte) ([]interface{}, error) {
+	parseExprBytesCommonFunc := func(exprsFromBytesFunc func() ([]Any, error)) ([]interface{}, error) {
-		exprs, err := exprsFromBytes(fam, ad, b)
+		exprs, err := exprsFromBytesFunc()
 		if err != nil {
 			return nil, err
 		}
@@ -36,6 +36,17 @@ func init() {
 		}
 		return result, nil
 	}
+
+	parseexprfunc.ParseExprBytesFromNameFunc = func(fam byte, ad *netlink.AttributeDecoder, exprName string) ([]interface{}, error) {
+		return parseExprBytesCommonFunc(func() ([]Any, error) {
+			return exprsBytesFromName(fam, ad, exprName)
+		})
+	}
+	parseexprfunc.ParseExprBytesFunc = func(fam byte, ad *netlink.AttributeDecoder) ([]interface{}, error) {
+		return parseExprBytesCommonFunc(func() ([]Any, error) {
+			return exprsFromBytes(fam, ad)
+		})
+	}
 	parseexprfunc.ParseExprMsgFunc = func(fam byte, b []byte) ([]interface{}, error) {
 		ad, err := netlink.NewAttributeDecoder(b)
 		if err != nil {
@@ -44,7 +55,7 @@ func init() {
 		ad.ByteOrder = binary.BigEndian
 		var exprs []interface{}
 		for ad.Next() {
-			e, err := parseexprfunc.ParseExprBytesFunc(fam, ad, b)
+			e, err := parseexprfunc.ParseExprBytesFunc(fam, ad)
 			if err != nil {
 				return e, err
 			}
@@ -59,15 +70,35 @@ func Marshal(fam byte, e Any) ([]byte, error) {
 	return e.marshal(fam)
 }
 
+func MarshalExprData(fam byte, e Any) ([]byte, error) {
+	return e.marshalData(fam)
+}
+
 // Unmarshal fills an expression from the specified byte slice.
 func Unmarshal(fam byte, data []byte, e Any) error {
 	return e.unmarshal(fam, data)
 }
 
+// exprsBytesFromName parses raw expressions bytes
+// based on provided expr name
+func exprsBytesFromName(fam byte, ad *netlink.AttributeDecoder, name string) ([]Any, error) {
+	var exprs []Any
+	e := exprFromName(name)
+	ad.Do(func(b []byte) error {
+		if err := Unmarshal(fam, b, e); err != nil {
+			return err
+		}
+		exprs = append(exprs, e)
+		return nil
+	})
+	return exprs, ad.Err()
+}
+
 // exprsFromBytes parses nested raw expressions bytes
 // to construct nftables expressions
-func exprsFromBytes(fam byte, ad *netlink.AttributeDecoder, b []byte) ([]Any, error) {
+func exprsFromBytes(fam byte, ad *netlink.AttributeDecoder) ([]Any, error) {
 	var exprs []Any
+
 	ad.Do(func(b []byte) error {
 		ad, err := netlink.NewAttributeDecoder(b)
 		if err != nil {
@@ -84,65 +115,12 @@ func exprsFromBytes(fam byte, ad *netlink.AttributeDecoder, b []byte) ([]Any, er
 					exprs = append(exprs, e)
 				}
 			case unix.NFTA_EXPR_DATA:
-				var e Any
+				e := exprFromName(name)
-				switch name {
-				case "ct":
-					e = &Ct{}
-				case "range":
-					e = &Range{}
-				case "meta":
-					e = &Meta{}
-				case "cmp":
-					e = &Cmp{}
-				case "counter":
-					e = &Counter{}
-				case "objref":
-					e = &Objref{}
-				case "payload":
-					e = &Payload{}
-				case "lookup":
-					e = &Lookup{}
-				case "immediate":
-					e = &Immediate{}
-				case "bitwise":
-					e = &Bitwise{}
-				case "redir":
-					e = &Redir{}
-				case "nat":
-					e = &NAT{}
-				case "limit":
-					e = &Limit{}
-				case "quota":
-					e = &Quota{}
-				case "dynset":
-					e = &Dynset{}
-				case "log":
-					e = &Log{}
-				case "exthdr":
-					e = &Exthdr{}
-				case "match":
-					e = &Match{}
-				case "target":
-					e = &Target{}
-				case "connlimit":
-					e = &Connlimit{}
-				case "queue":
-					e = &Queue{}
-				case "flow_offload":
-					e = &FlowOffload{}
-				case "reject":
-					e = &Reject{}
-				case "masq":
-					e = &Masq{}
-				case "hash":
-					e = &Hash{}
-				}
 				if e == nil {
 					// TODO: introduce an opaque expression type so that users know
 					// something is here.
 					continue // unsupported expression type
 				}
-
 				ad.Do(func(b []byte) error {
 					if err := Unmarshal(fam, b, e); err != nil {
 						return err
@@ -166,9 +144,67 @@ func exprsFromBytes(fam byte, ad *netlink.AttributeDecoder, b []byte) ([]Any, er
 	return exprs, ad.Err()
 }
 
+func exprFromName(name string) Any {
+	var e Any
+	switch name {
+	case "ct":
+		e = &Ct{}
+	case "range":
+		e = &Range{}
+	case "meta":
+		e = &Meta{}
+	case "cmp":
+		e = &Cmp{}
+	case "counter":
+		e = &Counter{}
+	case "objref":
+		e = &Objref{}
+	case "payload":
+		e = &Payload{}
+	case "lookup":
+		e = &Lookup{}
+	case "immediate":
+		e = &Immediate{}
+	case "bitwise":
+		e = &Bitwise{}
+	case "redir":
+		e = &Redir{}
+	case "nat":
+		e = &NAT{}
+	case "limit":
+		e = &Limit{}
+	case "quota":
+		e = &Quota{}
+	case "dynset":
+		e = &Dynset{}
+	case "log":
+		e = &Log{}
+	case "exthdr":
+		e = &Exthdr{}
+	case "match":
+		e = &Match{}
+	case "target":
+		e = &Target{}
+	case "connlimit":
+		e = &Connlimit{}
+	case "queue":
+		e = &Queue{}
+	case "flow_offload":
+		e = &FlowOffload{}
+	case "reject":
+		e = &Reject{}
+	case "masq":
+		e = &Masq{}
+	case "hash":
+		e = &Hash{}
+	}
+	return e
+}
+
 // Any is an interface implemented by any expression type.
 type Any interface {
 	marshal(fam byte) ([]byte, error)
+	marshalData(fam byte) ([]byte, error)
 	unmarshal(fam byte, data []byte) error
 }
 
@@ -214,7 +250,19 @@ type Meta struct {
 }
 
 func (e *Meta) marshal(fam byte) ([]byte, error) {
-	regData := []byte{}
+	exprData, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("meta\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: exprData},
+	})
+}
+
+func (e *Meta) marshalData(fam byte) ([]byte, error) {
+	var regData []byte
 	exprData, err := netlink.MarshalAttributes(
 		[]netlink.Attribute{
 			{Type: unix.NFTA_META_KEY, Data: binaryutil.BigEndian.PutUint32(uint32(e.Key))},
@@ -240,11 +288,7 @@ func (e *Meta) marshal(fam byte) ([]byte, error) {
 		return nil, err
 	}
 	exprData = append(exprData, regData...)
-
+	return exprData, nil
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("meta\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: exprData},
-	})
 }
 
 func (e *Meta) unmarshal(fam byte, data []byte) error {
@@ -291,6 +335,17 @@ const (
 )
 
 func (e *Masq) marshal(fam byte) ([]byte, error) {
+	msgData, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("masq\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: msgData},
+	})
+}
+
+func (e *Masq) marshalData(fam byte) ([]byte, error) {
 	msgData := []byte{}
 	if !e.ToPorts {
 		flags := uint32(0)
@@ -327,10 +382,7 @@ func (e *Masq) marshal(fam byte) ([]byte, error) {
 			msgData = append(msgData, regsData...)
 		}
 	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
+	return msgData, nil
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("masq\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: msgData},
-	})
 }
 
 func (e *Masq) unmarshal(fam byte, data []byte) error {
@@ -377,17 +429,7 @@ type Cmp struct {
 }
 
 func (e *Cmp) marshal(fam byte) ([]byte, error) {
-	cmpData, err := netlink.MarshalAttributes([]netlink.Attribute{
+	exprData, err := e.marshalData(fam)
-		{Type: unix.NFTA_DATA_VALUE, Data: e.Data},
-	})
-	if err != nil {
-		return nil, err
-	}
-	exprData, err := netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_CMP_SREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
-		{Type: unix.NFTA_CMP_OP, Data: binaryutil.BigEndian.PutUint32(uint32(e.Op))},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_CMP_DATA, Data: cmpData},
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -397,6 +439,20 @@ func (e *Cmp) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Cmp) marshalData(fam byte) ([]byte, error) {
+	cmpData, err := netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_DATA_VALUE, Data: e.Data},
+	})
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_CMP_SREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
+		{Type: unix.NFTA_CMP_OP, Data: binaryutil.BigEndian.PutUint32(uint32(e.Op))},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_CMP_DATA, Data: cmpData},
+	})
+}
+
 func (e *Cmp) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {

expr/exthdr.go

@@ -40,6 +40,17 @@ type Exthdr struct {
 }
 
 func (e *Exthdr) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("exthdr\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Exthdr) marshalData(fam byte) ([]byte, error) {
 	var attr []netlink.Attribute
 
 	// Operations are differentiated by the Op and whether the SourceRegister
@@ -64,14 +75,7 @@ func (e *Exthdr) marshal(fam byte) ([]byte, error) {
 			netlink.Attribute{Type: unix.NFTA_EXTHDR_FLAGS, Data: binaryutil.BigEndian.PutUint32(e.Flags)})
 	}
 
-	data, err := netlink.MarshalAttributes(attr)
+	return netlink.MarshalAttributes(attr)
-	if err != nil {
-		return nil, err
-	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("exthdr\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Exthdr) unmarshal(fam byte, data []byte) error {

expr/fib.go

@@ -37,6 +37,17 @@ type Fib struct {
 }
 
 func (e *Fib) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("fib\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Fib) marshalData(fam byte) ([]byte, error) {
 	data := []byte{}
 	reg, err := netlink.MarshalAttributes([]netlink.Attribute{
 		{Type: unix.NFTA_FIB_DREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
@@ -92,11 +103,7 @@ func (e *Fib) marshal(fam byte) ([]byte, error) {
 		}
 		data = append(data, rslt...)
 	}
-
+	return data, nil
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("fib\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Fib) unmarshal(fam byte, data []byte) error {

expr/flow_offload.go

@@ -28,9 +28,7 @@ type FlowOffload struct {
 }
 
 func (e *FlowOffload) marshal(fam byte) ([]byte, error) {
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	data, err := e.marshalData(fam)
-		{Type: NFTNL_EXPR_FLOW_TABLE_NAME, Data: []byte(e.Name)},
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -41,6 +39,12 @@ func (e *FlowOffload) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *FlowOffload) marshalData(fam byte) ([]byte, error) {
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: NFTNL_EXPR_FLOW_TABLE_NAME, Data: []byte(e.Name)},
+	})
+}
+
 func (e *FlowOffload) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {

expr/hash.go

@@ -41,6 +41,17 @@ type Hash struct {
 }
 
 func (e *Hash) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("hash\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Hash) marshalData(fam byte) ([]byte, error) {
 	hashAttrs := []netlink.Attribute{
 		{Type: unix.NFTA_HASH_SREG, Data: binaryutil.BigEndian.PutUint32(uint32(e.SourceRegister))},
 		{Type: unix.NFTA_HASH_DREG, Data: binaryutil.BigEndian.PutUint32(uint32(e.DestRegister))},
@@ -56,14 +67,7 @@ func (e *Hash) marshal(fam byte) ([]byte, error) {
 		{Type: unix.NFTA_HASH_OFFSET, Data: binaryutil.BigEndian.PutUint32(uint32(e.Offset))},
 		{Type: unix.NFTA_HASH_TYPE, Data: binaryutil.BigEndian.PutUint32(uint32(e.Type))},
 	}...)
-	data, err := netlink.MarshalAttributes(hashAttrs)
+	return netlink.MarshalAttributes(hashAttrs)
-	if err != nil {
-		return nil, err
-	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("hash\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Hash) unmarshal(fam byte, data []byte) error {

expr/immediate.go

@@ -29,6 +29,17 @@ type Immediate struct {
 }
 
 func (e *Immediate) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("immediate\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Immediate) marshalData(fam byte) ([]byte, error) {
 	immData, err := netlink.MarshalAttributes([]netlink.Attribute{
 		{Type: unix.NFTA_DATA_VALUE, Data: e.Data},
 	})
@@ -36,17 +47,10 @@ func (e *Immediate) marshal(fam byte) ([]byte, error) {
 		return nil, err
 	}
 
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	return netlink.MarshalAttributes([]netlink.Attribute{
 		{Type: unix.NFTA_IMMEDIATE_DREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
 		{Type: unix.NLA_F_NESTED | unix.NFTA_IMMEDIATE_DATA, Data: immData},
 	})
-	if err != nil {
-		return nil, err
-	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("immediate\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Immediate) unmarshal(fam byte, data []byte) error {

expr/limit.go

@@ -72,6 +72,18 @@ type Limit struct {
 }
 
 func (l *Limit) marshal(fam byte) ([]byte, error) {
+	data, err := l.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("limit\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (l *Limit) marshalData(fam byte) ([]byte, error) {
 	var flags uint32
 	if l.Over {
 		flags = unix.NFT_LIMIT_F_INV
@@ -84,15 +96,7 @@ func (l *Limit) marshal(fam byte) ([]byte, error) {
 		{Type: unix.NFTA_LIMIT_FLAGS, Data: binaryutil.BigEndian.PutUint32(flags)},
 	}
 
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("limit\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (l *Limit) unmarshal(fam byte, data []byte) error {

expr/log.go

@@ -69,6 +69,18 @@ type Log struct {
 }
 
 func (e *Log) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("log\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Log) marshalData(fam byte) ([]byte, error) {
 	// Per https://git.netfilter.org/libnftnl/tree/src/expr/log.c?id=09456c720e9c00eecc08e41ac6b7c291b3821ee5#n129
 	attrs := make([]netlink.Attribute, 0)
 	if e.Key&(1<<unix.NFTA_LOG_GROUP) != 0 {
@@ -109,15 +121,7 @@ func (e *Log) marshal(fam byte) ([]byte, error) {
 		})
 	}
 
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("log\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Log) unmarshal(fam byte, data []byte) error {

expr/lookup.go

@@ -34,6 +34,18 @@ type Lookup struct {
 }
 
 func (e *Lookup) marshal(fam byte) ([]byte, error) {
+	opData, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("lookup\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: opData},
+	})
+}
+
+func (e *Lookup) marshalData(fam byte) ([]byte, error) {
 	// See: https://git.netfilter.org/libnftnl/tree/src/expr/lookup.c?id=6dc1c3d8bb64077da7f3f28c7368fb087d10a492#n115
 	var opAttrs []netlink.Attribute
 	if e.SourceRegister != 0 {
@@ -49,15 +61,7 @@ func (e *Lookup) marshal(fam byte) ([]byte, error) {
 		netlink.Attribute{Type: unix.NFTA_LOOKUP_SET, Data: []byte(e.SetName + "\x00")},
 		netlink.Attribute{Type: unix.NFTA_LOOKUP_SET_ID, Data: binaryutil.BigEndian.PutUint32(e.SetID)},
 	)
-	opData, err := netlink.MarshalAttributes(opAttrs)
+	return netlink.MarshalAttributes(opAttrs)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("lookup\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: opData},
-	})
 }
 
 func (e *Lookup) unmarshal(fam byte, data []byte) error {

expr/match.go

@@ -18,6 +18,17 @@ type Match struct {
 }
 
 func (e *Match) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("match\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Match) marshalData(fam byte) ([]byte, error) {
 	// Per https://git.netfilter.org/libnftnl/tree/src/expr/match.c?id=09456c720e9c00eecc08e41ac6b7c291b3821ee5#n38
 	name := e.Name
 	// limit the extension name as (some) user-space tools do and leave room for
@@ -36,15 +47,7 @@ func (e *Match) marshal(fam byte) ([]byte, error) {
 		{Type: unix.NFTA_MATCH_REV, Data: binaryutil.BigEndian.PutUint32(e.Rev)},
 		{Type: unix.NFTA_MATCH_INFO, Data: info},
 	}
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("match\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Match) unmarshal(fam byte, data []byte) error {

expr/nat.go

@@ -57,6 +57,17 @@ type NAT struct {
 // | 00 00 00 02  |	|      data      |  reg 2
 
 func (e *NAT) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("nat\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *NAT) marshalData(fam byte) ([]byte, error) {
 	attrs := []netlink.Attribute{
 		{Type: unix.NFTA_NAT_TYPE, Data: binaryutil.BigEndian.PutUint32(uint32(e.Type))},
 		{Type: unix.NFTA_NAT_FAMILY, Data: binaryutil.BigEndian.PutUint32(e.Family)},
@@ -90,14 +101,7 @@ func (e *NAT) marshal(fam byte) ([]byte, error) {
 		attrs = append(attrs, netlink.Attribute{Type: unix.NFTA_NAT_FLAGS, Data: binaryutil.BigEndian.PutUint32(flags)})
 	}
 
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-	if err != nil {
-		return nil, err
-	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("nat\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *NAT) unmarshal(fam byte, data []byte) error {

expr/notrack.go

@@ -27,6 +27,10 @@ func (e *Notrack) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Notrack) marshalData(fam byte) ([]byte, error) {
+	return []byte("notrack\x00"), nil
+}
+
 func (e *Notrack) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 

expr/numgen.go

@@ -32,6 +32,18 @@ type Numgen struct {
 }
 
 func (e *Numgen) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("numgen\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Numgen) marshalData(fam byte) ([]byte, error) {
 	// Currently only two types are supported, failing if Type is not of two known types
 	switch e.Type {
 	case unix.NFT_NG_INCREMENTAL:
@@ -40,20 +52,12 @@ func (e *Numgen) marshal(fam byte) ([]byte, error) {
 		return nil, fmt.Errorf("unsupported numgen type %d", e.Type)
 	}
 
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	return netlink.MarshalAttributes([]netlink.Attribute{
 		{Type: unix.NFTA_NG_DREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
 		{Type: unix.NFTA_NG_MODULUS, Data: binaryutil.BigEndian.PutUint32(e.Modulus)},
 		{Type: unix.NFTA_NG_TYPE, Data: binaryutil.BigEndian.PutUint32(e.Type)},
 		{Type: unix.NFTA_NG_OFFSET, Data: binaryutil.BigEndian.PutUint32(e.Offset)},
 	})
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("numgen\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Numgen) unmarshal(fam byte, data []byte) error {

expr/objref.go

@@ -28,10 +28,7 @@ type Objref struct {
 }
 
 func (e *Objref) marshal(fam byte) ([]byte, error) {
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	data, err := e.marshalData(fam)
-		{Type: unix.NFTA_OBJREF_IMM_TYPE, Data: binaryutil.BigEndian.PutUint32(uint32(e.Type))},
-		{Type: unix.NFTA_OBJREF_IMM_NAME, Data: []byte(e.Name)}, // NOT \x00-terminated?!
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -42,6 +39,13 @@ func (e *Objref) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Objref) marshalData(fam byte) ([]byte, error) {
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_OBJREF_IMM_TYPE, Data: binaryutil.BigEndian.PutUint32(uint32(e.Type))},
+		{Type: unix.NFTA_OBJREF_IMM_NAME, Data: []byte(e.Name)}, // NOT \x00-terminated?!
+	})
+}
+
 func (e *Objref) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {

expr/payload.go

@@ -58,7 +58,18 @@ type Payload struct {
 }
 
 func (e *Payload) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
 
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("payload\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Payload) marshalData(fam byte) ([]byte, error) {
 	var attrs []netlink.Attribute
 
 	if e.OperationType == PayloadWrite {
@@ -89,15 +100,7 @@ func (e *Payload) marshal(fam byte) ([]byte, error) {
 		}
 	}
 
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-
-	if err != nil {
-		return nil, err
-	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("payload\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Payload) unmarshal(fam byte, data []byte) error {

expr/queue.go

@@ -44,14 +44,7 @@ type Queue struct {
 }
 
 func (e *Queue) marshal(fam byte) ([]byte, error) {
-	if e.Total == 0 {
+	data, err := e.marshalData(fam)
-		e.Total = 1 // The total default value is 1
-	}
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_QUEUE_NUM, Data: binaryutil.BigEndian.PutUint16(e.Num)},
-		{Type: unix.NFTA_QUEUE_TOTAL, Data: binaryutil.BigEndian.PutUint16(e.Total)},
-		{Type: unix.NFTA_QUEUE_FLAGS, Data: binaryutil.BigEndian.PutUint16(uint16(e.Flag))},
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -61,6 +54,17 @@ func (e *Queue) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Queue) marshalData(fam byte) ([]byte, error) {
+	if e.Total == 0 {
+		e.Total = 1 // The total default value is 1
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_QUEUE_NUM, Data: binaryutil.BigEndian.PutUint16(e.Num)},
+		{Type: unix.NFTA_QUEUE_TOTAL, Data: binaryutil.BigEndian.PutUint16(e.Total)},
+		{Type: unix.NFTA_QUEUE_FLAGS, Data: binaryutil.BigEndian.PutUint16(uint16(e.Flag))},
+	})
+}
+
 func (e *Queue) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {

expr/quota.go

@@ -30,6 +30,18 @@ type Quota struct {
 }
 
 func (q *Quota) marshal(fam byte) ([]byte, error) {
+	data, err := q.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("quota\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (q *Quota) marshalData(fam byte) ([]byte, error) {
 	attrs := []netlink.Attribute{
 		{Type: unix.NFTA_QUOTA_BYTES, Data: binaryutil.BigEndian.PutUint64(q.Bytes)},
 		{Type: unix.NFTA_QUOTA_CONSUMED, Data: binaryutil.BigEndian.PutUint64(q.Consumed)},
@@ -44,15 +56,7 @@ func (q *Quota) marshal(fam byte) ([]byte, error) {
 		Data: binaryutil.BigEndian.PutUint32(flags),
 	})
 
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("quota\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (q *Quota) unmarshal(fam byte, data []byte) error {

expr/range.go

@@ -31,6 +31,18 @@ type Range struct {
 }
 
 func (e *Range) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("range\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Range) marshalData(fam byte) ([]byte, error) {
 	var attrs []netlink.Attribute
 	var err error
 	var rangeFromData, rangeToData []byte
@@ -57,11 +69,7 @@ func (e *Range) marshal(fam byte) ([]byte, error) {
 	}
 	data = append(data, rangeFromData...)
 	data = append(data, rangeToData...)
-
+	return data, nil
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("range\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Range) unmarshal(fam byte, data []byte) error {

expr/redirect.go

@@ -29,6 +29,18 @@ type Redir struct {
 }
 
 func (e *Redir) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("redir\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Redir) marshalData(fam byte) ([]byte, error) {
 	var attrs []netlink.Attribute
 	if e.RegisterProtoMin > 0 {
 		attrs = append(attrs, netlink.Attribute{Type: unix.NFTA_REDIR_REG_PROTO_MIN, Data: binaryutil.BigEndian.PutUint32(e.RegisterProtoMin)})
@@ -40,15 +52,7 @@ func (e *Redir) marshal(fam byte) ([]byte, error) {
 		attrs = append(attrs, netlink.Attribute{Type: unix.NFTA_REDIR_FLAGS, Data: binaryutil.BigEndian.PutUint32(e.Flags)})
 	}
 
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("redir\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Redir) unmarshal(fam byte, data []byte) error {

expr/reject.go

@@ -28,10 +28,7 @@ type Reject struct {
 }
 
 func (e *Reject) marshal(fam byte) ([]byte, error) {
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	data, err := e.marshalData(fam)
-		{Type: unix.NFTA_REJECT_TYPE, Data: binaryutil.BigEndian.PutUint32(e.Type)},
-		{Type: unix.NFTA_REJECT_ICMP_CODE, Data: []byte{e.Code}},
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -41,6 +38,13 @@ func (e *Reject) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Reject) marshalData(fam byte) ([]byte, error) {
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_REJECT_TYPE, Data: binaryutil.BigEndian.PutUint32(e.Type)},
+		{Type: unix.NFTA_REJECT_ICMP_CODE, Data: []byte{e.Code}},
+	})
+}
+
 func (e *Reject) unmarshal(fam byte, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {

expr/rt.go

@@ -37,10 +37,7 @@ type Rt struct {
 }
 
 func (e *Rt) marshal(fam byte) ([]byte, error) {
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	data, err := e.marshalData(fam)
-		{Type: unix.NFTA_RT_KEY, Data: binaryutil.BigEndian.PutUint32(uint32(e.Key))},
-		{Type: unix.NFTA_RT_DREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
-	})
 	if err != nil {
 		return nil, err
 	}
@@ -50,6 +47,13 @@ func (e *Rt) marshal(fam byte) ([]byte, error) {
 	})
 }
 
+func (e *Rt) marshalData(fam byte) ([]byte, error) {
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_RT_KEY, Data: binaryutil.BigEndian.PutUint32(uint32(e.Key))},
+		{Type: unix.NFTA_RT_DREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
+	})
+}
+
 func (e *Rt) unmarshal(fam byte, data []byte) error {
 	return fmt.Errorf("not yet implemented")
 }

expr/socket.go

@@ -49,23 +49,26 @@ const (
 )
 
 func (e *Socket) marshal(fam byte) ([]byte, error) {
+	exprData, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("socket\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: exprData},
+	})
+}
+
+func (e *Socket) marshalData(fam byte) ([]byte, error) {
 	// NOTE: Socket.Level is only used when Socket.Key == SocketKeyCgroupv2. But `nft` always encoding it. Check link below:
 	// http://git.netfilter.org/nftables/tree/src/netlink_linearize.c?id=0583bac241ea18c9d7f61cb20ca04faa1e043b78#n319
-	exprData, err := netlink.MarshalAttributes(
+	return netlink.MarshalAttributes(
 		[]netlink.Attribute{
 			{Type: NFTA_SOCKET_DREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
 			{Type: NFTA_SOCKET_KEY, Data: binaryutil.BigEndian.PutUint32(uint32(e.Key))},
 			{Type: NFTA_SOCKET_LEVEL, Data: binaryutil.BigEndian.PutUint32(uint32(e.Level))},
 		},
 	)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("socket\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: exprData},
-	})
 }
 
 func (e *Socket) unmarshal(fam byte, data []byte) error {

expr/target.go

@@ -21,6 +21,17 @@ type Target struct {
 }
 
 func (e *Target) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("target\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Target) marshalData(fam byte) ([]byte, error) {
 	// Per https://git.netfilter.org/libnftnl/tree/src/expr/target.c?id=09456c720e9c00eecc08e41ac6b7c291b3821ee5#n38
 	name := e.Name
 	// limit the extension name as (some) user-space tools do and leave room for
@@ -40,15 +51,7 @@ func (e *Target) marshal(fam byte) ([]byte, error) {
 		{Type: unix.NFTA_TARGET_INFO, Data: info},
 	}
 
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-	if err != nil {
-		return nil, err
-	}
-
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("target\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Target) unmarshal(fam byte, data []byte) error {

expr/tproxy.go

@@ -40,6 +40,17 @@ type TProxy struct {
 }
 
 func (e *TProxy) marshal(fam byte) ([]byte, error) {
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("tproxy\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *TProxy) marshalData(fam byte) ([]byte, error) {
 	attrs := []netlink.Attribute{
 		{Type: NFTA_TPROXY_FAMILY, Data: binaryutil.BigEndian.PutUint32(uint32(e.Family))},
 		{Type: NFTA_TPROXY_REG_PORT, Data: binaryutil.BigEndian.PutUint32(e.RegPort)},
@@ -52,14 +63,7 @@ func (e *TProxy) marshal(fam byte) ([]byte, error) {
 		})
 	}
 
-	data, err := netlink.MarshalAttributes(attrs)
+	return netlink.MarshalAttributes(attrs)
-	if err != nil {
-		return nil, err
-	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("tproxy\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *TProxy) unmarshal(fam byte, data []byte) error {

expr/verdict.go

@@ -64,7 +64,17 @@ func (e *Verdict) marshal(fam byte) ([]byte, error) {
 	//     }
 	//   }
 	// }
+	data, err := e.marshalData(fam)
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("immediate\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
 
+func (e *Verdict) marshalData(fam byte) ([]byte, error) {
 	attrs := []netlink.Attribute{
 		{Type: unix.NFTA_VERDICT_CODE, Data: binaryutil.BigEndian.PutUint32(uint32(e.Kind))},
 	}
@@ -83,17 +93,10 @@ func (e *Verdict) marshal(fam byte) ([]byte, error) {
 		return nil, err
 	}
 
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	return netlink.MarshalAttributes([]netlink.Attribute{
 		{Type: unix.NFTA_IMMEDIATE_DREG, Data: binaryutil.BigEndian.PutUint32(unix.NFT_REG_VERDICT)},
 		{Type: unix.NLA_F_NESTED | unix.NFTA_IMMEDIATE_DATA, Data: immData},
 	})
-	if err != nil {
-		return nil, err
-	}
-	return netlink.MarshalAttributes([]netlink.Attribute{
-		{Type: unix.NFTA_EXPR_NAME, Data: []byte("immediate\x00")},
-		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
-	})
 }
 
 func (e *Verdict) unmarshal(fam byte, data []byte) error {

internal/parseexprfunc/parseexprfunc.go

@@ -5,6 +5,7 @@ import (
 )
 
 var (
-	ParseExprBytesFunc func(fam byte, ad *netlink.AttributeDecoder, b []byte) ([]interface{}, error)
+	ParseExprBytesFromNameFunc func(fam byte, ad *netlink.AttributeDecoder, exprName string) ([]interface{}, error)
-	ParseExprMsgFunc   func(fam byte, b []byte) ([]interface{}, error)
+	ParseExprBytesFunc         func(fam byte, ad *netlink.AttributeDecoder) ([]interface{}, error)
+	ParseExprMsgFunc           func(fam byte, b []byte) ([]interface{}, error)
 )

set.go

@@ -321,7 +321,7 @@ func (s *SetElement) decode(fam byte) func(b []byte) error {
 			case unix.NFTA_SET_ELEM_EXPIRATION:
 				s.Expires = time.Millisecond * time.Duration(ad.Uint64())
 			case unix.NFTA_SET_ELEM_EXPR:
-				elems, err := parseexprfunc.ParseExprBytesFunc(fam, ad, ad.Bytes())
+				elems, err := parseexprfunc.ParseExprBytesFunc(fam, ad)
 				if err != nil {
 					return err
 				}