请问sfilter.dll是做什么的？

在DDK中的PASSTHRU中，请问sfilter.dll是做什么的？

SUMMARY
This sample demonstrates how to write an .inf file and a notify object for installing and configuring an NDIS intermediate driver as a filter. Note that writing a notify object is optional, and is not required for proper installation of a filter.

A notify object should only be used if one needs to provide custom property sheet pages or if one needs non-default binding behavior. Note that in almost all cases, the default binding behavior afforded through the .inf is sufficient. The .inf supplied has ample documentation lines that clearly specify the parts of the .inf general to any networking component and the parts that are essential for installing a filter.

The notify object code shows how to:

Write a basic notify object to configure a filter.
Defer registry operations until the "ApplyRegistryChanges" method is called, so that a "Cancel" operation will not result in unnecessary changes to the registry.
Receive notifications when other components are added, removed, bound, or unbound.
Provide a custom property sheet page that will be used by the Connections UI to configure your component.
The sample compiles properly for 64-bit, builds properly with Microsoft? Visual C? 6.0, and supports Plug and Play.

BUILDING THE SAMPLE
To build the sample, type build. Once built, the sample will produce two binaries: Sfilter.dll and Snetcfg.exe. Sfilter.dll is the sample notify object for filter components, and Snetcfg.exe is a sample executable that shows how to use various INetCfg interfaces.


INSTALLING THE SAMPLE
Following are installation instructions for the Filter sample through the connection folder.

1. Create a local directory on the machine (for instance, d:\sample).
2. Copy Sfilter.dll, Sfiltern.tlb, Netsf.inf, Netsf_m.inf, Passthru.sys to the directory.

3. Open the connection folder.

4. Raise the properties for a LAN connection, click the Install button, select Service, and click Add.

5. Click Have Disk, and then specify the path to the local directory you just created.

6. Select Sample Filter, and then click OK in the Select Network Service dialog box.


Here's an alternate way to install the sample by using Snetcfg.exe as the sample client. To install, type snetcfg -l d:\sample\netsf.inf -c s -i ms_sfilter. To uninstall, type snetcfg -u ms_sfilter

KNOWN BUGS
In Sfilter, INetCfgPropertyUi::SetContext sets m_guidDevice to GUID_NULL, which is temporary and won't really allow the sample user to store per-adapter information correctly.

The components list displayed for the current connection may become empty when installing the filter for the first time. To fix this, close the connection properties (without adding anything else) and then reopen them.

New values for the filter sample's parameters are not saved when closing the properties by clicking OK. To fix this problem, the notify object should send a PSM_CHANGED message to the parent property sheet, on the OnInitDialog function of its property page.
CODE TOUR
File Manifest
File Description

Filter Directory for the Filter notify object sample
Dllmain.cpp File containing implementations of DLL entry point and exports
Implinc.cpp File including source code for ATL utilities
Netsf.inf Sample Filter .inf file
Netsf_m.inf Sample Filter Miniport .inf file
Pch.h Pre-compiled header file
Netcfg.htm The documentation for the Filter sample
Resource.h The resource header
Sfilter.cpp Notify object's implementation for the sample filter
Sfilter.def Filter sample's def file
Sfilter.h The header file for Sfilter.cpp
Sfilter.rc The resource file for the filter notify object's sample
Sfilter.rgs Script-based registry support for the filter notify object
Sfiltern.idl Filter notify object's .idl file

Netcfg Directory for the NetCfg sample
Idls.idl This file includes Netcfgx.idl
Implinc.cpp File including guids definitions for the com stuff used by the Netcfg sample
Main.cpp File containing implementations of main and usage functions
Pch.h Pre-compiled header file
Snetcfg.cpp The actual sample source for Netcfg APIs
Snetcfg.h The header file for Sfilter.h
Snetcfg.rc The resource file for the Netcfg sample