On 2023-03-25, at 11:35:47 +0100, Phil Sutter wrote:
> On Fri, Mar 24, 2023 at 11:59:04PM +0100, Florian Westphal wrote:
> > Jeremy Sowden <jeremy@azazel.net> wrote:
> > > +ip daddr 10.0.0.1 tcp dport 55900-55910 dnat ip to 192.168.127.1:5900-5910/55900;ok
> > > +ip6 daddr 10::1 tcp dport 55900-55910 dnat ip6 to [::c0:a8:7f:1]:5900-5910/55900;ok
> >
> > This syntax is horrible (yes, I know, xtables fault).
> >
> > Do you think this series could be changed to grab the offset register from the
> > left edge of the range rather than requiring the user to specify it a
> > second time?  Something like:
> >
> > ip daddr 10.0.0.1 tcp dport 55900-55910 dnat ip to 192.168.127.1:5900-5910
> >
> > I'm open to other suggestions of course.
>
> Initially, a map came to mind. Something like:
>
> | dnat to : tcp dport map { 1000-2000 : 5000-6000 }
>
> To my surprise, nft accepts the syntax (listing is broken, though). But
> IIUC, it means "return 5000-6000 for any port in [1000;2000]" and dnat
> does round-robin?

That does ring a bell.  IIRC, when I initially looked into this, I did
have a look at maps to see if they might already offer analogous func-
tionality.

> At least it's not what one would expect. Maybe one could control the
> lookup behaviour somehow via a flag?

Thanks for the suggestion.

J.