Microsoft Internet Security and
Acceleration Server 2000
Whenever a notification event for which the filter has
registered (in GetFilterVersion) occurs, the ISA Web proxy
service calls HttpFilterProc. The Web proxy service uses
this function to pass information and control to the Web (ISAPI)
filter. The declaration of HttpFilterProc is:
Points to the HTTP_FILTER_CONTEXT data structure that
is associated with the current, active HTTP transaction.
Points to a bitmask that indicates the type of notification
event that is being processed. See Event Notifications for a list of
The notification-specific structure that contains more
information about the current context of the request.
pvNotification Points To …
Note SF_NOTIFY_SEND_RESPONSE is
not used when the ISA Web proxy service sends a response. However,
it is called when a filter generates a response itself by using
Returns one of the following values that indicate how the
application handled the event.
The filter has handled the HTTP request. The server should
disconnect the session.
Treated the same as SF_STATUS_REQ_FINISHED. After this
notification is received, the connection is closed.
The next filter in the notification chain should be
This filter handled the notification. No other handlers should
be called for this particular notification type.
An error occurred. The server should call GetLastError
and indicate the error to the client. The HTTP request will
generally be aborted when this status is returned. The client
should call SetLastError with the nature of the
The filter is an opaque stream filter (encrypted/compressed
HTTP requests) and the session parameters are being negotiated.
This is valid only for raw-read notification. This value indicates
that the full request has not yet been received; the Web server
should issue another read and notify the filter with the additional
This function usually serves as the dispatch for a Web (ISAPI)
filter. Separate functions are often created to serve as handlers
for the separate notifications, especially if the handling code is