return of ingoingFilter

Hi Paul,

ingoingFilter can return null or a Reply or NoOngoingFilter. Anything else? If ingoingFilter return a Reply, to whom this Reply will be forward? How about the Reply generated by the FilteredResource then? If ingoingFilter generates a Reply,
can I stop its hooked resource to perform that original Request, and use ingoingFilter's Reply as
the perform()'s result?

Thanks,
Qiang