> However I'm unable to make my input filter function to be called before my > handler.
Input filters are normally called during the handler, when the handler tries to read the request body through the filter chain. In your case, the body is probably not read until the core of Apache sees it needs to discard the body the handler didn't read towards the end of the request. You'll need to read the body (see e.g. mod_cgi.c near r->input_filters)
