An Architecture for Smart Filtering
The key to a generic smart filter is that it must operate
late in the processing chain, so that the response headers are available
for context-sensitive dispatching. We must therefore drop the filter_init
handler from the structure, and defer some configuration-based decisions.
Dropping the filter_init is of course trivial: filters that use it can
preserve the function, and simply call it from the main filter callback
when f->ctx is unset.
To deal with late dispatching, we propose an updated architecture, to
be implemented as a generic mod_filter. The purpose of mod_filter is
to handle smart configuration on behalf of filter modules in general.
