Looking again at the st_mode compare: I'm pretty sure the old code worked somewhere, at some time. Maybe somewhere it still does, and expecting a different fstat():st_mode will break that. Unless something changed in OpenLDAP itself?

Anyway, after re-reading ITS#4893 I'd be very wary about tweaking this code. Looks like at least I just gave up at the end, but followup#9 suggests using Solaris "doors". IIRC I did look at at the supposedly more general STREAMS pipes and found myself wading into portability issues or kernel tuning params or whateveer.