Re: Patch: accept filters for NetBSD

[Thor Lancelot Simon <tls%rek.tjls.com@localhost>]

On Tue, Jan 29, 2008 at 12:36:27PM +0200, Elad Efrat wrote:
> 
> I'm sorry, but this whole thing looks very dodgy to me. :/ There's just
> something disturbing about putting string parsing in the kernel network
> stack.

Well, you don't have to use it; it is a per-socket option, after all.

> What's the motivation of adding the accept filters? I understand one may
> be performance -- are there any relevant benchmarks? Is it possible to
> hear more about why this is necessary, and what are planned future
> extensions, if any?

It is not necessary.  It provides an opportunity to optimize the processing
of certain application-layer protocols (the ones that like to make a lot
of connections at once) without moving the entire protocol into the kernel,
which you would presumably object to much more (talk about string parsing
in the kernel! :-)).

This is one of those features that has been in FreeBSD for about a decade
but was just never noticed by us over here on the NetBSD side of the fence.
Apache and a few other things can use it, but most of the code that uses
it heavily probably is proprietary code belonging to device vendors -- I
know mine is.

I think it is better for NetBSD to not diverge from FreeBSD in this sort
of area if we can arrange not to.

I don't have any benchmarks immediately available that I can release but
I'm adding support for this to inetd, which should provide a useful
demonstration and an opportunity to get some quick numbers.  I hope that's
helpful.

> FWIW, a quick search didn't come up with any benchmarks nor discussions
> in the FreeBSD archives. Maybe it was too quick? :)

Probably -- the feature is quite old.

Thor