Luigi Rizzo wrote:
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.
one COULD, but I know I use this feature only with a number (20 or less)
following rules, each of which is a skipto itself to some further awat
location...or a simple drop..
Shall we say we "leave it as an exercise for the reader" ?
> > 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
luigi
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