Fix crash when interface monitor is unavailable

dns/transport/dhcp/dhcp.go

@@ -109,7 +109,11 @@ func (t *Transport) Start(stage adapter.StartStage) error {
 		return nil
 	}
 	if t.interfaceName == "" {
-		t.interfaceCallback = t.networkManager.InterfaceMonitor().RegisterCallback(t.interfaceUpdated)
+		interfaceMonitor := t.networkManager.InterfaceMonitor()
+		if interfaceMonitor == nil {
+			return E.New("missing monitor for auto DHCP, set route.auto_detect_interface")
+		}
+		t.interfaceCallback = interfaceMonitor.RegisterCallback(t.interfaceUpdated)
 	}
 	go func() {
 		err := t.fetch()

protocol/direct/outbound.go

@@ -99,7 +99,11 @@ func (h *Outbound) Start(stage adapter.StartStage) error {
 }
 
 func (h *Outbound) fetchMyAddresses() {
-	myInterfaceNames := h.network.InterfaceMonitor().MyInterfaces()
+	interfaceMonitor := h.network.InterfaceMonitor()
+	if interfaceMonitor == nil {
+		return
+	}
+	myInterfaceNames := interfaceMonitor.MyInterfaces()
 	if len(myInterfaceNames) == 0 {
 		return
 	}

route/rule/rule_default_interface_address.go

@@ -29,6 +29,9 @@ func NewDefaultInterfaceAddressItem(networkManager adapter.NetworkManager, inter
 }
 
 func (r *DefaultInterfaceAddressItem) Match(metadata *adapter.InboundContext) bool {
+	if r.interfaceMonitor == nil {
+		return false
+	}
 	defaultInterface := r.interfaceMonitor.DefaultInterface()
 	if defaultInterface == nil {
 		return false

route/rule/rule_network_interface_address.go

@@ -40,7 +40,11 @@ func NewNetworkInterfaceAddressItem(networkManager adapter.NetworkManager, inter
 
 func (r *NetworkInterfaceAddressItem) Match(metadata *adapter.InboundContext) bool {
 	interfaces := r.networkManager.NetworkInterfaces()
-	myInterfaces := r.networkManager.InterfaceMonitor().MyInterfaces()
+	var myInterfaces []string
+	interfaceMonitor := r.networkManager.InterfaceMonitor()
+	if interfaceMonitor != nil {
+		myInterfaces = interfaceMonitor.MyInterfaces()
+	}
 match:
 	for ifType, addresses := range r.interfaceAddresses {
 		for _, networkInterface := range interfaces {