header-custom finalmask: Add UDP standalone handshake mode (#5945)

175502d807

common/serial/typed_message_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	. "github.com/xtls/xray-core/common/serial"
+	"github.com/xtls/xray-core/transport/internet/finalmask/header/custom"
 )
 
 func TestGetInstance(t *testing.T) {
@@ -22,3 +23,31 @@ func TestConvertingNilMessage(t *testing.T) {
 		t.Error("expect nil, but actually not")
 	}
 }
+
+func TestTypedMessageRoundTripPreservesFinalmaskCustomUDPMode(t *testing.T) {
+	msg := &custom.UDPConfig{
+		Mode: "standalone",
+		Client: []*custom.UDPItem{
+			{Rand: 12, Save: "txid"},
+		},
+	}
+
+	tm := ToTypedMessage(msg)
+	if tm == nil {
+		t.Fatal("expected typed message")
+	}
+
+	roundTrip, err := tm.GetInstance()
+	if err != nil {
+		t.Fatalf("GetInstance() failed: %v", err)
+	}
+
+	udp, ok := roundTrip.(*custom.UDPConfig)
+	if !ok {
+		t.Fatalf("unexpected round-trip type: %T", roundTrip)
+	}
+
+	if udp.GetMode() != "standalone" {
+		t.Fatalf("mode lost during typed message round-trip: got %q", udp.GetMode())
+	}
+}