Format of packet driver IOCB:
Offset	Size	Description	)
 00h	DWORD	pointer to buffer
 04h	WORD	length of buffer
 06h	BYTE	flags
		bit 0: packet driver is finished with IOCB
		bit 1: application requests upcall when driver completes
 07h	DWORD	function address for upcall (see #03313)
 0Bh  4 BYTEs	future gather write
 0Fh	BYTE	???
 10h  8 BYTEs	private driver workspace