Microsoft KB Archive/183794

= Smart IPX Device Driver Interface to Srv.sys =

Article ID: 183794

Article Last Modified on 10/31/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Server 4.0 Enterprise Edition

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This article was previously published under Q183794



SUMMARY
This document defines the Smart IPX interface. This interface is provided by the Windows NT CIFS/SMB file server driver (Srv.sys) to facilitate the offload of bulk transmit requests to IPX-based intelligent LAN subsystems.

WARNING: This interface exists in Windows NT version 4.0; however, the interface is not guaranteed to exist in versions of Windows NT beyond 5.0.

The interface allows independent software vendors (ISVs) or independent hardware vendors (IHVs) to provide drivers that provides a bulk transmit capability to Srv.sys. These ISV-provided drivers will be called SmartIO drivers, or simply SmartIO. This Smart IPX interface is available as a Windows NT kernel-mode driver interface, and is not available to user-mode applications.

NOTE: Although the term "Smart Card" is used in this interface, it should not be confused with the normal use of "Smart Cards"; "Smart Card" in this context is used to refer to IPX-based cards with the ability to deal with large amounts of I/O.

Traditionally, Srv.sys initiates data transmissions to requesting clients by breaking bulk data down into network-sized packets and individually submitting those packets to the lower networking layers (TDI/NDIS) for transmission. This process can be very CPU-intense and may consume a large portion of a server's CPU cycles. Bulk transmit requests, however, enable Srv.sys to efficiently pass large blocks of raw data to intelligent LAN subsystems for network packetization and transmission. The purpose of bulk transmit requests is to offload the CPU-intense network processing that normally occurs in Srv.sys, NwLinkIpx, NDIS wrapper, and NDIS drivers.

The Smart IPX Device Driver Interface (DDI) enables SmartIO drivers to interface directly with Srv.sys. SmartIO drivers must, in turn, interface with intelligent LAN subsystems to submit bulk transmit operations. This lower level interface is deemed to be ISV-specific and is not included in the scope of this specification.

The Smart IPX interface is a call/callback between Srv.sys and a SmartIO driver. The following calls are currently defined: Open, Read, ReadComplete, Close, and Deregister.

The call/callback addresses are initially exchanged as a result of an internal device IOCTL sent by the SmartIO driver to Srv.sys. Direct calls are made between the two drivers after this initial IOCTL.



MORE INFORMATION
The following sections define the Smart IPX call/callback interface. It is assumed that the reader has the Windows NT Device Driver Kit (DDK) and understands how to write kernel-mode drivers.

Registration IOCTL
SmartIO registers and exchanges call/callback addresses with Srv.sys during it's initialization. This registration is accomplished by sending an IOCTL to Srv.Sys of the following type:

#define FSCTL_SRV_IPX_SMART_CARD_START \ _SRV_CONTROL_CODE (21, METHOD_NEITHER)

Prior to sending the internal request, update the SystemBuffer field of the internal request packet (IRP) to point to the following data structure, which is provided by the SmartIO driver.

typedef struct { BOOLEAN (*Open)(          IN PVOID SmbHeader           IN PFILE_OBJECT FileObject,           IN PUNICODE_STRING FileName,           IN PTDI_ADDRESS_IPX IpxAddress,           IN ULONG Flags,           OUT PVOID *SmartCardContext); VOID (*Close)(          PVOID SmartCardContext); BOOLEAN (*Read) (          IN PVOID SmbHeader,           IN PVOID SmartCardContext,           IN LONG Key,           IN VOID SrvContext); VOID (*ReadComplete)(          IN PVOID SrvContext,           IN PFILE_OBJECT FileObject,           IN PMDL Mdl,           IN ULONG Length); VOID (*DeRegister)(          VOID); } SRV_IPX_SMART_CARD, *PSRV_IPX_SMART_CARD;

The server fills in the ReadComplete field with its own routine address, which is used in the ReadComplete callback (see the ReadComplete section below).

Open
BOOLEAN Open(      IN PVOID SmbHeader       IN PFILE_OBJECT FileObject,       IN PUNICODE_STRING FileName,       IN PTDI_ADDRESS_IPX IpxAddress,       IN ULONG Flags,       OUT PVOID *SmartCardContext);

This is a call from Srv.Sys to SmartIO. It will occur for an OpenFile SMB from the client -- after Srv.Sys has validated the SMB and performed the file open, but before the SMB response is sent back to the client. Its parameters are:

SmbHeader -- Pointer to the SMB header for this request.

FileObject -- File object pointer for the file just opened on behalf of

the client.

FileName -- Name of the file just opened; this is for future use in case

we want do special processing based on the file extension.

IpxAddress -- Pointer to a structure defining the network address.

Flags -- Various file related flags; THUN_CACHE_SUPPORTED is the only

flag currently defined.

SmartCardContext -- Pointer to a location where SmartIO will place its

ID for this file. If a zero is returned, SmartIO should not be called

for reads of this file.

SmartIO returns TRUE if reads of this file can be accelerated; otherwise, it returns FALSE.

Return Values:

TRUE -- SmartIO should be called for reads of this file.

FALSE -- SmartIO should not be called for reads of this file.

Read
BOOLEAN Read(      IN PVOID SmbHeader,       IN PVOID SmartCardContext,       IN LONG Key,       IN VOID SrvContext);

This is a call from Srv.sys to SmartIO. It will occur for Read and Read Multiplexed SMBs from the client, after the Server has validated the SMB. Its parameters are:

SmbHeader -- Pointer to the SMB header for this request.

SmartCardContext -- Value returned on Open.

Key -- Parameter required to read the file.

SrvContext -- Value that will be returned by SmartIO on a ReadComplete call.

SmartIO will send the read responses to the client as required and when complete will call the server's ReadComplete function. This routine must be called at PASSIVE level.

If SmartIO can handle the read request, it will return TRUE; otherwise, it will return FALSE.

Return Values:

TRUE -- SmartIO will perform the read of this file.

FALSE -- SmartIO cannot perform the read of this file.

ReadComplete
VOID ReadComplete(      IN PVOID SrvContext,       IN PFILE_OBJECT FileObject,       IN PMDL Mdl,       IN ULONG Length);

This is a call from SmartIO to Srv.sys. It occurs in response to a Read call. Its parameters are:

SrvContext -- Value that was passed in on the Read call.

FileObject -- File object from Open call.

Mdl -- Mdl chain for just completed read operation.

Length -- Length of data for just-completed read operation.

Srv.sys will mark this read as complete and do any required cleanup processing. This routine can be called at DISPATCH level.

Return Values:

None

Close
VOID Close(      PVOID SmartCardContext);

This is a call from Srv.sys to SmartIO. It will occur for a CloseFile SMB from the client, after the server has validated the SMB. It has one parameter:

SmartCardContext -- Value returned on Open call.

SmartIO will free any resources it allocated as a result of the Open call and will return.

Return Values:

None

Deregister
VOID Deregister(      VOID);

This is a call from Srv.sys to SmartIO. It will occur if Srv.sys is being unloaded.

Return Values:

None

Additional query words: Srv SmartIO IPX FSCTL_SRV_IPX_SMART_CARD_START

Keywords: kbinfo KB183794

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