Date: Tue, 19 Aug 2008 20:23:37 +0200 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Ian Smith <smithi@nimnet.asn.au> Cc: FreeBSD Net <freebsd-net@freebsd.org>, ipfw@freebsd.org, Julian Elischer <julian@elischer.org> Subject: Re: ipfw add skipto tablearg.... Message-ID: <20080819182337.GA25703@onelab2.iet.unipi.it> In-Reply-To: <20080820031409.V41971@sola.nimnet.asn.au> References: <48926C02.6030308@elischer.org> <Pine.BSF.3.96.1080819152451.21367A-100000@gaia.nimnet.asn.au> <20080819133101.GA23276@onelab2.iet.unipi.it> <20080820031409.V41971@sola.nimnet.asn.au>
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On Wed, Aug 20, 2008 at 04:06:05AM +1000, Ian Smith wrote: > On Tue, 19 Aug 2008, Luigi Rizzo wrote: > > On Tue, Aug 19, 2008 at 11:12:04PM +1000, Ian Smith wrote: ... > > > Until $someone adds a direct skipto target jump at the virtual machine > > > code level - big recalc hit when adding/deleting rules/sets I suppose - > > > it's still the fastest way to get from a to b, where b > a > > > > you mean with tables-based skipto targets ? Because the regular > > skipto has been a constant-time op forever, even in ipfw1 i believe, > > invalidating the target cache on a change and recomputing it the > > fly at the first request. > > Thanks; I'd completely missed the caching of skipto targets before, and > it's all so well commented too. blushing, but glad for the good news. > > But yes I was pondering Julian's patch, which has to lookup_next_rule > every time, and also Mike's bending of divert reentry rule number in > ipfw-classifyd with similar intent, which also has to hunt forward in > linear time for its target rule - or am I missing something else here? well, you can use a hash table to support that. It shouldn't be so bad to implement, flow tables already use hash tables so one can reuse the same code. > > > Speaking of which, should ipfw whinge when asked to skip backwards, > > > which it can't, confirmed on a recent browse re Mike's ipfw-classifyd > > > and a local test months ago. > > > > right... but the error can only be reliably detected in the kernel, > > as the rule number is not always known when the rule is added. > > Yes I meant at run-time. On second thoughts, it'd be too easy a way to actually you can do it at insertion time, it's just that you cannot do it in userland as other checks before inserting the rule. cheers luigihome | help
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