The input filter API function signature is the following:
apr_status_t func(
ap_filter_t *f,
apr_bucket_brigade *b,
ap_input_mode_t mode,
apr_read_type_e block,
apr_off_t readbytes);
Problems:
1) This gives the caller of the API control over weither they can
block via the apr_read_type_e block.
2) The caller also suggests how much data 'should' be read by passing
of readbytes, however many modules just pull in whatever they can, or
they have to put in extra logic to keep a backlog buffer.
3) Currently we have these modes:
AP_MODE_READBYTES,
AP_MODE_GETLINE,
AP_MODE_EATCRLF,
AP_MODE_SPECULATIVE,
AP_MODE_EXHAUSTIVE,
AP_MODE_INIT
This means every input filter, must implement all of these different
modes. This significantly complicates modules like mod_ssl and
reqtimeout. Every module to support things like speculative must
support buffering internally.
I would like to change the function signature for connection level
input filters to:
apr_status_t func(
ap_filter_t *f,
apr_bucket_brigade *b);
The function always be allowed to return EAGAIN. It would not be
responsible for polling or blocking.
This would massively simplify how most input filters work, and would
enable more creative methods of network IO inside the MPMs.
Most of the work would be in ap_rgetline_core, and figuring out how to
make it work without pushing complexity into the protocol parsers.
It would however reduce the total lines of code I believe, because we
would be centralizing all input buffering and different mode needs
into one place.
I believe we would need to add a new method to the MPMs,
ap_mpm_poll_connection() as a transitionary API. This could be called
by ap_rgetline_core or ap_get_brigade, and in the the traditional IO
MPMs like Worker, and Prefork, select/poll on the socket until it is
available. I'm unsure about how to best fix ap_get_brigade, it is also
used within mod_proxy for client IO.
Thoughts?
Thanks,
Paul
