wintun: wait for interface registry key on device creation

By using RegNotifyChangeKeyValue(). Also disable dead gateway detection.

Signed-off-by: Simon Rozman <simon@rozman.si>

1 files changed, 240 insertions, 0 deletions

diff --git a/tun/wintun/registry/registry_windows.go b/tun/wintun/registry/registry_windows.go
new file mode 100644
index 0000000..65da6bf
--- /dev/null
+++ b/tun/wintun/registry/registry_windows.go
@@ -0,0 +1,240 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package registry
+
+import (
+	"errors"
+	"fmt"
+	"runtime"
+	"strings"
+	"time"
+
+	"golang.org/x/sys/windows"
+	"golang.org/x/sys/windows/registry"
+)
+
+const (
+	KEY_NOTIFY uint32 = 0x0010 // should be defined upstream as registry.KEY_NOTIFY
+)
+
+const (
+	// REG_NOTIFY_CHANGE_NAME notifies the caller if a subkey is added or deleted.
+	REG_NOTIFY_CHANGE_NAME uint32 = 0x00000001
+
+	// REG_NOTIFY_CHANGE_ATTRIBUTES notifies the caller of changes to the attributes of the key, such as the security descriptor information.
+	REG_NOTIFY_CHANGE_ATTRIBUTES uint32 = 0x00000002
+
+	// REG_NOTIFY_CHANGE_LAST_SET notifies the caller of changes to a value of the key. This can include adding or deleting a value, or changing an existing value.
+	REG_NOTIFY_CHANGE_LAST_SET uint32 = 0x00000004
+
+	// REG_NOTIFY_CHANGE_SECURITY notifies the caller of changes to the security descriptor of the key.
+	REG_NOTIFY_CHANGE_SECURITY uint32 = 0x00000008
+
+	// REG_NOTIFY_THREAD_AGNOSTIC indicates that the lifetime of the registration must not be tied to the lifetime of the thread issuing the RegNotifyChangeKeyValue call. Note: This flag value is only supported in Windows 8 and later.
+	REG_NOTIFY_THREAD_AGNOSTIC uint32 = 0x10000000
+)
+
+//sys	regNotifyChangeKeyValue(key windows.Handle, watchSubtree bool, notifyFilter uint32, event windows.Handle, asynchronous bool) (regerrno error) = advapi32.RegNotifyChangeKeyValue
+
+func OpenKeyWait(k registry.Key, path string, access uint32, timeout time.Duration) (registry.Key, error) {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	deadline := time.Now().Add(timeout)
+	pathSpl := strings.Split(path, "\\")
+	for i := 0; ; i++ {
+		keyName := pathSpl[i]
+		isLast := i+1 == len(pathSpl)
+
+		event, err := windows.CreateEvent(nil, 0, 0, nil)
+		if err != nil {
+			return 0, fmt.Errorf("Error creating event: %v", err)
+		}
+		defer windows.CloseHandle(event)
+
+		var key registry.Key
+		for {
+			err = regNotifyChangeKeyValue(windows.Handle(k), false, REG_NOTIFY_CHANGE_NAME, windows.Handle(event), true)
+			if err != nil {
+				return 0, fmt.Errorf("Setting up change notification on registry key failed: %v", err)
+			}
+
+			var accessFlags uint32
+			if isLast {
+				accessFlags = access
+			} else {
+				accessFlags = KEY_NOTIFY
+			}
+			key, err = registry.OpenKey(k, keyName, accessFlags)
+			if err == windows.ERROR_FILE_NOT_FOUND || err == windows.ERROR_PATH_NOT_FOUND {
+				timeout := time.Until(deadline) / time.Millisecond
+				if timeout < 0 {
+					timeout = 0
+				}
+				s, err := windows.WaitForSingleObject(event, uint32(timeout))
+				if err != nil {
+					return 0, fmt.Errorf("Unable to wait on registry key: %v", err)
+				}
+				if s == uint32(windows.WAIT_TIMEOUT) { // windows.WAIT_TIMEOUT status const is misclassified as error in golang.org/x/sys/windows
+					return 0, errors.New("Timeout waiting for registry key")
+				}
+			} else if err != nil {
+				return 0, fmt.Errorf("Error opening registry key %v: %v", path, err)
+			} else {
+				if isLast {
+					return key, nil
+				}
+				defer key.Close()
+				break
+			}
+		}
+
+		k = key
+	}
+}
+
+func WaitForKey(k registry.Key, path string, timeout time.Duration) error {
+	key, err := OpenKeyWait(k, path, KEY_NOTIFY, timeout)
+	if err != nil {
+		return err
+	}
+	key.Close()
+	return nil
+}
+
+//
+// getStringValueRetry function reads a string value from registry. It waits for
+// the registry value to become available or returns error on timeout.
+//
+// Key must be opened with at least QUERY_VALUE|KEY_NOTIFY access.
+//
+func getStringValueRetry(key registry.Key, name string, timeout time.Duration) (string, uint32, error) {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	event, err := windows.CreateEvent(nil, 0, 0, nil)
+	if err != nil {
+		return "", 0, fmt.Errorf("Error creating event: %v", err)
+	}
+	defer windows.CloseHandle(event)
+
+	deadline := time.Now().Add(timeout)
+	for {
+		err := regNotifyChangeKeyValue(windows.Handle(key), false, REG_NOTIFY_CHANGE_LAST_SET, windows.Handle(event), true)
+		if err != nil {
+			return "", 0, fmt.Errorf("Setting up change notification on registry value failed: %v", err)
+		}
+
+		value, valueType, err := key.GetStringValue(name)
+		if err == windows.ERROR_FILE_NOT_FOUND || err == windows.ERROR_PATH_NOT_FOUND {
+			timeout := time.Until(deadline) / time.Millisecond
+			if timeout < 0 {
+				timeout = 0
+			}
+			s, err := windows.WaitForSingleObject(event, uint32(timeout))
+			if err != nil {
+				return "", 0, fmt.Errorf("Unable to wait on registry value: %v", err)
+			}
+			if s == uint32(windows.WAIT_TIMEOUT) { // windows.WAIT_TIMEOUT status const is misclassified as error in golang.org/x/sys/windows
+				return "", 0, errors.New("Timeout waiting for registry value")
+			}
+		} else if err != nil {
+			return "", 0, fmt.Errorf("Error reading registry value %v: %v", name, err)
+		} else {
+			return value, valueType, nil
+		}
+	}
+}
+
+func expandString(value string, valueType uint32, err error) (string, error) {
+	if err != nil {
+		return "", err
+	}
+
+	if valueType != registry.EXPAND_SZ {
+		// Value does not require expansion.
+		return value, nil
+	}
+
+	valueExp, err := registry.ExpandString(value)
+	if err != nil {
+		// Expanding failed: return original sting value.
+		return value, nil
+	}
+
+	// Return expanded value.
+	return valueExp, nil
+}
+
+//
+// GetStringValueWait function reads a string value from registry. It waits
+// for the registry value to become available or returns error on timeout.
+//
+// Key must be opened with at least QUERY_VALUE|KEY_NOTIFY access.
+//
+// If the value type is REG_EXPAND_SZ the environment variables are expanded.
+// Should expanding fail, original string value and nil error are returned.
+//
+func GetStringValueWait(key registry.Key, name string, timeout time.Duration) (string, error) {
+	return expandString(getStringValueRetry(key, name, timeout))
+}
+
+//
+// GetStringValue function reads a string value from registry.
+//
+// Key must be opened with at least QUERY_VALUE access.
+//
+// If the value type is REG_EXPAND_SZ the environment variables are expanded.
+// Should expanding fail, original string value and nil error are returned.
+//
+func GetStringValue(key registry.Key, name string) (string, error) {
+	return expandString(key.GetStringValue(name))
+}
+
+//
+// GetIntegerValueWait function reads a DWORD32 or QWORD value from registry.
+// It waits for the registry value to become available or returns error on
+// timeout.
+//
+// Key must be opened with at least QUERY_VALUE|KEY_NOTIFY access.
+//
+func GetIntegerValueWait(key registry.Key, name string, timeout time.Duration) (uint64, error) {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	event, err := windows.CreateEvent(nil, 0, 0, nil)
+	if err != nil {
+		return 0, fmt.Errorf("Error creating event: %v", err)
+	}
+	defer windows.CloseHandle(event)
+
+	deadline := time.Now().Add(timeout)
+	for {
+		err := regNotifyChangeKeyValue(windows.Handle(key), false, REG_NOTIFY_CHANGE_LAST_SET, windows.Handle(event), true)
+		if err != nil {
+			return 0, fmt.Errorf("Setting up change notification on registry value failed: %v", err)
+		}
+
+		value, _, err := key.GetIntegerValue(name)
+		if err == windows.ERROR_FILE_NOT_FOUND || err == windows.ERROR_PATH_NOT_FOUND {
+			timeout := time.Until(deadline) / time.Millisecond
+			if timeout < 0 {
+				timeout = 0
+			}
+			s, err := windows.WaitForSingleObject(event, uint32(timeout))
+			if err != nil {
+				return 0, fmt.Errorf("Unable to wait on registry value: %v", err)
+			}
+			if s == uint32(windows.WAIT_TIMEOUT) { // windows.WAIT_TIMEOUT status const is misclassified as error in golang.org/x/sys/windows
+				return 0, errors.New("Timeout waiting for registry value")
+			}
+		} else if err != nil {
+			return 0, fmt.Errorf("Error reading registry value %v: %v", name, err)
+		} else {
+			return value, nil
+		}
+	}
+}