When disabling the Windows device, wait for pending reads to complete.

[tinc] / src / mingw / device.c

diff --git a/src/mingw/device.c b/src/mingw/device.c
index 19719a7..73da2f1 100644 (file)
--- a/src/mingw/device.c
+++ b/src/mingw/device.c
@@ -210,10 +210,18 @@ static void disable_device(void) {
 
        io_del(&device_read_io);
        CancelIo(device_handle);
+
+       /* According to MSDN, CancelIo() does not necessarily wait for the operation to complete.
+          To prevent race conditions, make sure the operation is complete
+          before we close the event it's referencing. */
+
+       DWORD len;
+       if(!GetOverlappedResult(device_handle, &device_read_overlapped, &len, TRUE) && GetLastError() != ERROR_OPERATION_ABORTED)
+               logger(DEBUG_ALWAYS, LOG_ERR, "Could not wait for %s %s read to cancel: %s", device_info, device, winerror(GetLastError()));
+
        CloseHandle(device_read_overlapped.hEvent);
 
        ULONG status = 0;
-       DWORD len;
        DeviceIoControl(device_handle, TAP_IOCTL_SET_MEDIA_STATUS, &status, sizeof status, &status, sizeof status, &len, NULL);
 }