Merge e9249a316d into 5e242ec578

Signed-off-by: thediveo <thediveo@gmx.eu>

xt/comment.go

@@ -5,7 +5,8 @@ import (
 	"fmt"
 )
 
-// CommentSize is the fixed size of a comment info xt blob.
+// CommentSize is the fixed size of a comment info xt blob, see:
+// https://elixir.bootlin.com/linux/v6.8.7/source/include/uapi/linux/netfilter/xt_comment.h#L5
 const CommentSize = 256
 
 // Comment gets marshalled and unmarshalled as a fixed-sized char array, filled
@@ -15,7 +16,8 @@ type Comment string
 
 func (c *Comment) marshal(fam TableFamily, rev uint32) ([]byte, error) {
 	if len(*c) >= CommentSize {
-		return nil, fmt.Errorf("Comment must be less than %d bytes", CommentSize)
+		return nil, fmt.Errorf("comment must be less than %d bytes, got %d bytes",
+			CommentSize, len(*c))
 	}
 	data := make([]byte, CommentSize)
 	copy(data, []byte(*c))
@@ -24,7 +26,8 @@ func (c *Comment) marshal(fam TableFamily, rev uint32) ([]byte, error) {
 
 func (c *Comment) unmarshal(fam TableFamily, rev uint32, data []byte) error {
 	if len(data) != CommentSize {
-		return fmt.Errorf("Comment takes exactly %d bytes", CommentSize)
+		return fmt.Errorf("malformed comment: got %d bytes, expected exactly %d bytes",
+			len(data), CommentSize)
 	}
 	*c = Comment(bytes.TrimRight(data, "\x00"))
 	return nil

xt/comment_test.go

@@ -1,7 +1,6 @@
 package xt
 
 import (
-	"fmt"
 	"reflect"
 	"strings"
 	"testing"
@@ -23,7 +22,7 @@ func TestComment(t *testing.T) {
 		{
 			name:   "marshal oversized Comment",
 			info:   &oversized,
-			errmsg: "Comment must be less than 256 bytes",
+			errmsg: "comment must be less than 256 bytes, got 600 bytes",
 		},
 	}
 
@@ -57,8 +56,7 @@ func TestComment(t *testing.T) {
 
 	oversizeddata := []byte(oversized)
 	var comment Comment
-	if err := (&comment).unmarshal(0, 0, oversizeddata); err == nil || err.Error() != fmt.Sprintf("Comment takes exactly %d bytes", CommentSize) {
-		t.Fatalf("unmarshal: expected error: %v", err)
-
+	if err := (&comment).unmarshal(0, 0, oversizeddata); err == nil {
+		t.Fatalf("unmarshal: expected error, but got nil")
 	}
 }