Re: [PATCH nftables 8/8] test: py: add tests for shifted nat port-ranges

[Pablo Neira Ayuso <pablo@netfilter.org>]

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.

Not only syntax, main problema is that this port shift support has to
work with NAT maps, otherwise this needs N rules for different
mappings which takes us back to linear rule inspection.

Jeremy, may I suggest you pick up on the bitwise _SREG2 support?
I will post a v4 with small updates for ("mark statement support for
non-constant expression") tomorrow. Probably you don't need the new
AND and OR operations for this? Only the a new _SREG2 to specify that
input comes from non-constant?