2 files changed, 34 insertions, 0 deletions
diff --git a/tun/wintun/setupapi/setupapi_windows.go b/tun/wintun/setupapi/setupapi_windows.go
index 71732a4..5f9e05c 100644
--- a/tun/wintun/setupapi/setupapi_windows.go
+++ b/tun/wintun/setupapi/setupapi_windows.go
@@ -7,12 +7,14 @@ package setupapi
 
 import (
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"syscall"
 	"unsafe"
 
 	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/registry"
+	"golang.zx2c4.com/wireguard/tun/wintun/guid"
 )
 
 //sys	setupDiCreateDeviceInfoListEx(classGUID *windows.GUID, hwndParent uintptr, machineName *uint16, reserved uintptr) (handle DevInfo, err error) [failretval==DevInfo(windows.InvalidHandle)] = setupapi.SetupDiCreateDeviceInfoListExW
@@ -234,6 +236,33 @@ func (deviceInfoSet DevInfo) OpenDevRegKey(DeviceInfoData *DevInfoData, Scope DI
 	return SetupDiOpenDevRegKey(deviceInfoSet, DeviceInfoData, Scope, HwProfile, KeyType, samDesired)
 }
 
+// GetInterfaceID method returns network interface ID.
+func (deviceInfoSet DevInfo) GetInterfaceID(deviceInfoData *DevInfoData) (*windows.GUID, error) {
+	// Open HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\<class>\<id> registry key.
+	key, err := deviceInfoSet.OpenDevRegKey(deviceInfoData, DICS_FLAG_GLOBAL, 0, DIREG_DRV, registry.READ)
+	if err != nil {
+		return nil, errors.New("Device-specific registry key open failed: " + err.Error())
+	}
+	defer key.Close()
+
+	// Read the NetCfgInstanceId value.
+	value, valueType, err := key.GetStringValue("NetCfgInstanceId")
+	if err != nil {
+		return nil, errors.New("RegQueryStringValue(\"NetCfgInstanceId\") failed: " + err.Error())
+	}
+	if valueType != registry.SZ {
+		return nil, fmt.Errorf("NetCfgInstanceId registry value is not REG_SZ (expected: %v, provided: %v)", registry.SZ, valueType)
+	}
+
+	// Convert to windows.GUID.
+	ifid, err := guid.FromString(value)
+	if err != nil {
+		return nil, fmt.Errorf("NetCfgInstanceId registry value is not a GUID (expected: \"{...}\", provided: \"%v\")", value)
+	}
+
+	return ifid, nil
+}
+
 //sys	setupDiGetDeviceRegistryProperty(deviceInfoSet DevInfo, deviceInfoData *DevInfoData, property SPDRP, propertyRegDataType *uint32, propertyBuffer *byte, propertyBufferSize uint32, requiredSize *uint32) (err error) = setupapi.SetupDiGetDeviceRegistryPropertyW
 
 // SetupDiGetDeviceRegistryProperty function retrieves a specified Plug and Play device property.
diff --git a/tun/wintun/setupapi/setupapi_windows_test.go b/tun/wintun/setupapi/setupapi_windows_test.go
index 30f3692..c6f4a15 100644
--- a/tun/wintun/setupapi/setupapi_windows_test.go
+++ b/tun/wintun/setupapi/setupapi_windows_test.go
@@ -291,6 +291,11 @@ func TestSetupDiOpenDevRegKey(t *testing.T) {
 			t.Errorf("Error calling SetupDiOpenDevRegKey: %s", err.Error())
 		}
 		defer key.Close()
+
+		_, err = devInfoList.GetInterfaceID(data)
+		if err != nil {
+			t.Errorf("Error calling GetInterfaceID: %s", err.Error())
+		}
 	}
 }