Re: [nf-next] netfilter: acct: add support to accounters in nftables

[Patrick McHardy <kaber@trash.net>]

On 12.01, Patrick McHardy wrote:
> On 12.01, Pablo Neira Ayuso wrote:
> > On Mon, Jan 12, 2015 at 11:45:39AM +0000, Patrick McHardy wrote:
> > > > NFT_ACCT_MAXNAMELEN needs to be limited to 16 bytes, so we can easily
> > > > use acct objects from mappings.
> > > 
> > > Not saying that we need more than 16 bytes, but we'd hopefully use
> > > references instead of runtime resolved lookups in mappings :)
> > 
> > I just noticed Ana have to replace NFTA_ACCT_EXPR_NAME by
> > NFTA_ACCT_EXPR_SREG to support mappings.
> > 
> > What's your idea behind the references? Use some unique id to identify
> > the object instead of the name?
> 
> Similar to verdicts we'd include another data type which refers to
> accounting objects. Those are resolved when the data is created and
> we'd return them from the map lookup. Resolving can use the name,
> just as we do for chains.
> 
> At runtime the map would either load the reference to a register and
> pass it to the counter expression (might need a special register
> similar to NFT_REG_VERDICT) or we just add a special type of the
> counter expression that invokes the lookup itself.

Thinking a bit more about this, I think this is very much similar
to what we've discussed about having some generic state provider
for limit, quota etc.

In all these cases we need to provide some persistent storage to
the expressions to be used instead of their private data. For
hashlimit or hashquota it would probably be based on some generic
state provider that dynamically instantiates this, but its still
very similar to looking up an accounting object in a set and
passing that on.

So strike that "special type of counter expression", I think what
we need is either a special register to pass state between modules
or just some better validation for the existing registers so passing
pointers is safe.