Modifications to NETBT.SYS to Support Layered Drivers

• Microsoft Windows NT Workstation version 3.51
• Microsoft Windows NT Server version 3.51

SYMPTOMS

Under Windows NT, when a device driver creates an I/O Request Packet (IRP) to pass to an underlying driver, it creates the IRP with a fixed number of I/O stack locations, one for each driver in the chain of layered drivers for which the request is bound. Each stack location contains the parameters, function codes, and context used by the corresponding driver to determine what it is supposed to be doing with the request.

In Windows NT 3.51, I/O Request Packets built by the NETBT.SYS driver always have a stack frame size of 1. This presents a problem should device driver developers wish to "layer" an additional driver between NETBT.SYS and TCPIP.SYS because there are not enough stack frames in the IRP for the vertical driver to use.

For certain operations, NetBT also incorrectly passes IRPs directly to TCP/IP, thereby skipping any intermediate drivers in the driver chain.

RESOLUTION

To resolve this problem, install the fix mentioned below.

To correct this problem, apply the fix mentioned below.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 3.51. This problem was corrected in the latest U.S. Service Pack for Windows NT Workstation or Server version 3.51. For information on obtaining this update, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K