Re: [iptables PATCH] extensions: libxt_statistic: Complete nft translator

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

On Tue, Mar 14, 2017 at 03:11:12PM +0100, Phil Sutter wrote:
> On Mon, Mar 13, 2017 at 05:53:53PM +0100, Pablo Neira Ayuso wrote:
> > On Mon, Mar 13, 2017 at 05:01:53PM +0100, Phil Sutter wrote:
> > [...]
> > > The nftables numgen expression works differently:
> > 
> > Phil, if you think we need a 1:1 mapping so iptables users moving to
> > nftables don't get confused, I'll be fine to take an update to
> > nft_numgen so we accomodate a new NFT_NG_PROBABILISTIC mode or so.
> 
> Well, implementing the translator wasn't exactly trivial, but in general
> I don't think numgen is particularly hard to use. Of course an explicit
> probability mode might make things easier, but then I guess it wouldn't
> fit into the LHS/RHS scheme anymore.

Right, we would need a specific statement for this.

Question is how useful this can be as statement. The usecases I found
for this are:

1) Load balancing, which is already covered by numgen via maps.
2) Simulate packet loss.

With a statement we could combine this probability thing with flow
tables, but still I wonder how useful can be to match packets using
probability at a per-flow level, a.k.a. hashprobability.

Florian already sent a patch to add an alias for this [1], problem is
that this break symmetry between what we add to the kernel and what we
may get, and that is going to break the rule deletion by description.

Just a brain dump on this in case anyone want to spend jiffies on
this.

[1] https://patchwork.ozlabs.org/patch/591534/