Objects implementation refactor

Refactored obj.go to a more generic approach
Added object support for already implemented expressions
Added test for limit object
Fixes https://github.com/google/nftables/issues/253

expr/expr.go

@@ -25,8 +25,8 @@ import (
 )
 
 func init() {
-	parseexprfunc.ParseExprBytesFunc = func(fam byte, ad *netlink.AttributeDecoder, args ...string) ([]interface{}, error) {
+	parseExprBytesCommonFunc := func(exprsFromBytesFunc func() ([]Any, error)) ([]interface{}, error) {
-		exprs, err := exprsFromBytes(fam, ad, args...)
+		exprs, err := exprsFromBytesFunc()
 		if err != nil {
 			return nil, err
 		}
@@ -36,7 +36,18 @@ func init() {
 		}
 		return result, nil
 	}
-	parseexprfunc.ParseExprMsgFunc = func(fam byte, b []byte, args ...string) ([]interface{}, error) {
+
+	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 {
 			return nil, err
@@ -44,7 +55,7 @@ func init() {
 		ad.ByteOrder = binary.BigEndian
 		var exprs []interface{}
 		for ad.Next() {
-			e, err := parseexprfunc.ParseExprBytesFunc(fam, ad, args...)
+			e, err := parseexprfunc.ParseExprBytesFunc(fam, ad)
 			if err != nil {
 				return e, err
 			}
@@ -68,21 +79,25 @@ 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, args ...string) ([]Any, error) {
+func exprsFromBytes(fam byte, ad *netlink.AttributeDecoder) ([]Any, error) {
 	var exprs []Any
-	if len(args) > 0 {
-		e := exprFromName(args[0])
-		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()
-	}
 
 	ad.Do(func(b []byte) error {
 		ad, err := netlink.NewAttributeDecoder(b)

internal/parseexprfunc/parseexprfunc.go

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

obj.go

@@ -256,7 +256,7 @@ func objFromMsg(msg netlink.Message, returnLegacyType bool) (Obj, error) {
 				Type:  ObjType(objectType),
 			}
 
-			objs, err := parseexprfunc.ParseExprBytesFunc(byte(o.family()), ad, objByObjTypeMagic[o.Type])
+			objs, err := parseexprfunc.ParseExprBytesFromNameFunc(byte(o.family()), ad, objByObjTypeMagic[o.Type])
 			if err != nil {
 				return nil, err
 			}