Date: Thu, 24 Aug 2006 17:35:42 -0700 From: Luigi Rizzo <rizzo@icir.org> To: Ian FREISLICH <if@hetzner.co.za> Cc: freebsd-ipfw@freebsd.org Subject: Re: ipfw performance and random musings. Message-ID: <20060824173542.A95870@xorpc.icir.org> In-Reply-To: <E1GGENQ-0008mi-2A@hetzner.co.za>; from if@hetzner.co.za on Thu, Aug 24, 2006 at 02:32:04PM %2B0200 References: <if@hetzner.co.za> <E1GGENQ-0008mi-2A@hetzner.co.za>
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On Thu, Aug 24, 2006 at 02:32:04PM +0200, Ian FREISLICH wrote:
> Ian FREISLICH wrote:
> > Luigi Rizzo wrote:
> > > On Wed, Aug 02, 2006 at 01:42:51PM +0200, Ian FREISLICH wrote:
> > > > You're thinking somewhere on the lines of:
> > > >
> > > > skipto base hash-if <name pattern> from <number> to <number> delta <delta
> > [offset <number>]
>
> This is the syntax I've pretty much settled upon:
>
> skipto 1000 ip from any to any ifhash vlan[1000-1264] offset -1000 delta 100
>
> Which for matching interfaces calculates the skipto target as:
>
> 1000 + (iface# + offset) * delta
>
> If you're happy with this format, I'll update the ipfw manual page
> and submit a patch for review and commit.
I would suggest a modification to the syntax as follows:
skipto @ ... recv|xmit|via foo[A-B] base X delta D
where @ is a keyword (meaning "the jump target is computed elsewhere")
and "foo[A-B] base X delta D" is an extension of the interface-name
option already available in ipfw.
The motivations are the following:
1. "ifhash" is misleading, as it isn't really hashing anything.
The real hashing, if you implemented it, is in the
rule_number --> rule_ptr lookup table, which is a general mechanism
and not a specific one.
2. the "foo[A-B]" in your example as a double purpose: match
interface names within a range, and compute the jump target.
- The former part is just an extension of the interface name
syntax, so it is nicer if you implement it in a way that can
be used wherever the 'foo' or 'fooN' can be.
Also this part can be useful even if you add a 'starting rule'
to interface descriptors. The "base X delta D" part could be
optional, and if not specified it means that @ cannot be
used as a jump target (or it just defaults to the next rule,
or some other documented behaviour e.g. use D=1 and X = current_rule+1)
- For the latter part (computing "X + (iface# - A) * D"),
the 'offset' parameter that you propose is completely redundant,
and i think the whole rule is a lot more readable if you put
all the arguments in one place, rather than spreading them
between the 'skipto' and the interface specifier.
I have no idea how you wrote your current implementation but i
believe that by using the above syntax even the internal implementation
could be quite straightforward.
cheers
luigi
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