For large number (1M+) of connections (doing websockets or long polling) to replicate the functionality of a COMET server I've been playing with rolling my own

For large number (1M+) of connections (doing websockets or long polling) to replicate the functionality of a COMET server I've been playing with rolling my own TCP handling via libnetfilter_queue as I simple don't need the ~10kB of r/w buffers on each socket. Linux (as far as I'm aware) doesn't allow tuning of r/w buffer sizes on a per interface basis otherwise I'd have one interface for the COMET server with drastically reduced r/w buffer sizes and the remaining interfaces with 'normal' TCP r/w buffer sizes to ensure the other things running on that host run without problem.