Fix inconsistent URLTest results

adapter/outbound.go

@@ -27,6 +27,11 @@ type OutboundWithPreferredRoutes interface {
 	PreferredAddress(address netip.Addr) bool
 }
 
+type OutboundWithMultiplex interface {
+	Outbound
+	MultiplexEnabled() bool
+}
+
 type DirectRouteOutbound interface {
 	Outbound
 	NewDirectRouteConnection(metadata InboundContext, routeContext tun.DirectRouteContext, timeout time.Duration) (tun.DirectRouteDestination, error)

common/urltest/urltest.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/sagernet/sing-box/adapter"
 	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing/common"
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/ntp"
@@ -72,7 +73,18 @@ func (s *HistoryStorage) Close() error {
 	return nil
 }
 
-func URLTest(ctx context.Context, link string, detour N.Dialer) (t uint16, err error) {
+func URLTest(ctx context.Context, link string, detour N.Dialer) (uint16, error) {
+	multiplexOutbound, isMultiplexOutbound := common.Cast[adapter.OutboundWithMultiplex](detour)
+	if isMultiplexOutbound && multiplexOutbound.MultiplexEnabled() {
+		_, err := urlTest(ctx, link, detour)
+		if err != nil {
+			return 0, err
+		}
+	}
+	return urlTest(ctx, link, detour)
+}
+
+func urlTest(ctx context.Context, link string, detour N.Dialer) (t uint16, err error) {
 	if link == "" {
 		link = "https://www.gstatic.com/generate_204"
 	}

protocol/shadowsocks/outbound.go

@@ -26,6 +26,8 @@ func RegisterOutbound(registry *outbound.Registry) {
 	outbound.Register[option.ShadowsocksOutboundOptions](registry, C.TypeShadowsocks, NewOutbound)
 }
 
+var _ adapter.OutboundWithMultiplex = (*Outbound)(nil)
+
 type Outbound struct {
 	outbound.Adapter
 	logger          logger.ContextLogger
@@ -124,6 +126,10 @@ func (h *Outbound) ListenPacket(ctx context.Context, destination M.Socksaddr) (n
 	}
 }
 
+func (h *Outbound) MultiplexEnabled() bool {
+	return h.multiplexDialer != nil
+}
+
 func (h *Outbound) InterfaceUpdated() {
 	if h.multiplexDialer != nil {
 		h.multiplexDialer.Reset()

protocol/trojan/outbound.go

@@ -26,6 +26,8 @@ func RegisterOutbound(registry *outbound.Registry) {
 	outbound.Register[option.TrojanOutboundOptions](registry, C.TypeTrojan, NewOutbound)
 }
 
+var _ adapter.OutboundWithMultiplex = (*Outbound)(nil)
+
 type Outbound struct {
 	outbound.Adapter
 	logger          logger.ContextLogger
@@ -107,6 +109,10 @@ func (h *Outbound) ListenPacket(ctx context.Context, destination M.Socksaddr) (n
 	}
 }
 
+func (h *Outbound) MultiplexEnabled() bool {
+	return h.multiplexDialer != nil
+}
+
 func (h *Outbound) InterfaceUpdated() {
 	if h.transport != nil {
 		h.transport.Close()

protocol/vless/outbound.go

@@ -27,6 +27,8 @@ func RegisterOutbound(registry *outbound.Registry) {
 	outbound.Register[option.VLESSOutboundOptions](registry, C.TypeVLESS, NewOutbound)
 }
 
+var _ adapter.OutboundWithMultiplex = (*Outbound)(nil)
+
 type Outbound struct {
 	outbound.Adapter
 	logger          logger.ContextLogger
@@ -127,6 +129,10 @@ func (h *Outbound) ListenPacket(ctx context.Context, destination M.Socksaddr) (n
 	}
 }
 
+func (h *Outbound) MultiplexEnabled() bool {
+	return h.multiplexDialer != nil
+}
+
 func (h *Outbound) InterfaceUpdated() {
 	if h.transport != nil {
 		h.transport.Close()

protocol/vmess/outbound.go

@@ -27,6 +27,8 @@ func RegisterOutbound(registry *outbound.Registry) {
 	outbound.Register[option.VMessOutboundOptions](registry, C.TypeVMess, NewOutbound)
 }
 
+var _ adapter.OutboundWithMultiplex = (*Outbound)(nil)
+
 type Outbound struct {
 	outbound.Adapter
 	logger          logger.ContextLogger
@@ -105,6 +107,10 @@ func NewOutbound(ctx context.Context, router adapter.Router, logger log.ContextL
 	return outbound, nil
 }
 
+func (h *Outbound) MultiplexEnabled() bool {
+	return h.multiplexDialer != nil
+}
+
 func (h *Outbound) InterfaceUpdated() {
 	if h.transport != nil {
 		h.transport.Close()