Windows NDIS Driver: Concurrent Read/Write on a single device (IRP_MJ_READ/WRITE)

Question

Starting with the ndisprot sample from Microsoft I try to write a NDIS protocol driver. From User space I try to read and write to the device simultaneous (out of two thread

Answer 1

By default, you can only have one outstanding I/O request per usermode handle. Either open multiple handles, or open your one handle with FILE_FLAG_OVERLAPPED. (Once you use FILE_FLAG_OVERLAPPED, you also generally need to use OVERLAPPED structures - make sure you've got the gist of it by skimming this and this.)