use own Logger interface

attribute.go

@@ -4,15 +4,14 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
-	"log"
 	"time"
 
 	"github.com/florianl/go-nflog/v2/internal/unix"
 
 	"github.com/mdlayher/netlink"
 )
 
-func extractAttribute(a *Attribute, logger *log.Logger, data []byte) error {
+func extractAttribute(a *Attribute, logger Logger, data []byte) error {
 	ad, err := netlink.NewAttributeDecoder(data)
 	if err != nil {
 		return err
@@ -129,7 +128,7 @@ func extractAttribute(a *Attribute, logger *log.Logger, data []byte) error {
 			a.VLAN = info
 			ad.ByteOrder = nativeEndian
 		default:
-			logger.Printf("Unknown attribute: %d %v\n", ad.Type(), ad.Bytes())
+			logger.Debugf("Unknown attribute: %d %v\n", ad.Type(), ad.Bytes())
 		}
 	}
 
@@ -143,7 +142,7 @@ func checkHeader(data []byte) int {
 	return 0
 }
 
-func extractAttributes(logger *log.Logger, msg []byte) (Attribute, error) {
+func extractAttributes(logger Logger, msg []byte) (Attribute, error) {
 	attrs := Attribute{}
 
 	offset := checkHeader(msg[:2])

nflog.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"encoding/binary"
 	"fmt"
-	"log"
 	"sync"
 	"time"
 	"unsafe"
@@ -19,7 +18,7 @@ type Nflog struct {
 	// Con is the pure representation of a netlink socket
 	Con *netlink.Conn
 
-	logger *log.Logger
+	logger Logger
 
 	wg sync.WaitGroup
 
@@ -32,12 +31,13 @@ type Nflog struct {
 	settings uint16
 }
 
-// devNull satisfies io.Writer, in case *log.Logger is not provided
+var _ Logger = (*devNull)(nil)
+
+// devNull satisfies the Logger interface.
 type devNull struct{}
 
-func (devNull) Write(p []byte) (int, error) {
-	return 0, nil
-}
+func (dn *devNull) Debugf(format string, args ...interface{}) {}
+func (dn *devNull) Errorf(format string, args ...interface{}) {}
 
 // for detailes see https://github.com/tensorflow/tensorflow/blob/master/tensorflow/go/tensor.go#L488-L505
 var nativeEndian binary.ByteOrder
@@ -79,7 +79,7 @@ func Open(config *Config) (*Nflog, error) {
 	nflog.Con = con
 
 	if config.Logger == nil {
-		nflog.logger = log.New(new(devNull), "", 0)
+		nflog.logger = new(devNull)
 	} else {
 		nflog.logger = config.Logger
 	}
@@ -133,7 +133,7 @@ func (nflog *Nflog) Register(ctx context.Context, fn HookFunc) error {
 				return 0
 			}
 		}
-		nflog.logger.Printf("Could not receive message: %v\n", err)
+		nflog.logger.Errorf("Could not receive message: %v\n", err)
 		return 1
 	})
 }
@@ -218,7 +218,7 @@ func (nflog *Nflog) RegisterWithErrorFunc(ctx context.Context, fn HookFunc, errf
 				{Type: nfUlACfgCmd, Data: []byte{nfUlnlCfgCmdUnbind}},
 			})
 			if err != nil {
-				nflog.logger.Printf("Could not unbind socket from configuration: %v", err)
+				nflog.logger.Errorf("Could not unbind socket from configuration: %v", err)
 				return
 			}
 		}()
@@ -234,7 +234,7 @@ func (nflog *Nflog) RegisterWithErrorFunc(ctx context.Context, fn HookFunc, errf
 		}()
 		for {
 			if err := ctx.Err(); err != nil {
-				nflog.logger.Printf("Stop receiving nflog messages: %v", err)
+				nflog.logger.Errorf("Error and stopping receiving nflog messages: %v", err)
 				return
 			}
 			reply, err := nflog.Con.Receive()
@@ -253,7 +253,7 @@ func (nflog *Nflog) RegisterWithErrorFunc(ctx context.Context, fn HookFunc, errf
 				}
 				attrs, err := parseMsg(nflog.logger, msg)
 				if err != nil {
-					nflog.logger.Printf("Could not parse message: %v", err)
+					nflog.logger.Debugf("Could not parse message: %v", err)
 					continue
 				}
 				if ret := fn(attrs); ret != 0 {
@@ -317,7 +317,7 @@ func (nflog *Nflog) execute(req netlink.Message) (uint32, error) {
 	return seq, nil
 }
 
-func parseMsg(logger *log.Logger, msg netlink.Message) (Attribute, error) {
+func parseMsg(logger Logger, msg netlink.Message) (Attribute, error) {
 	a, err := extractAttributes(logger, msg.Data)
 	if err != nil {
 		return Attribute{}, err

types.go

@@ -2,7 +2,6 @@ package nflog
 
 import (
 	"errors"
-	"log"
 	"time"
 )
 
@@ -120,6 +119,12 @@ type VLAN struct {
 	TCI   uint16
 }
 
+// Logger provides logging functionality.
+type Logger interface {
+	Debugf(format string, args ...interface{})
+	Errorf(format string, args ...interface{})
+}
+
 // Config contains options for a Conn.
 type Config struct {
 	// Network namespace the Nflog needs to operate in. If set to 0 (default),
@@ -159,7 +164,7 @@ type Config struct {
 	ReadTimeout time.Duration
 
 	// Interface to log internals.
-	Logger *log.Logger
+	Logger Logger
 }
 
 // ErrorFunc is a function that receives all errors that happen while reading