Add ntp protocol sniffing

common/sniff/ntp_test.go

@@ -0,0 +1,33 @@
+package sniff_test
+
+import (
+	"context"
+	"encoding/hex"
+	"os"
+	"testing"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing-box/common/sniff"
+	C "github.com/sagernet/sing-box/constant"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSniffNTP(t *testing.T) {
+	t.Parallel()
+	packet, err := hex.DecodeString("1b0006000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")
+	require.NoError(t, err)
+	var metadata adapter.InboundContext
+	err = sniff.NTP(context.Background(), &metadata, packet)
+	require.NoError(t, err)
+	require.Equal(t, metadata.Protocol, C.ProtocolNTP)
+}
+
+func TestSniffNTPFailed(t *testing.T) {
+	t.Parallel()
+	packet, err := hex.DecodeString("400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")
+	require.NoError(t, err)
+	var metadata adapter.InboundContext
+	err = sniff.NTP(context.Background(), &metadata, packet)
+	require.ErrorIs(t, err, os.ErrInvalid)
+}