Pablo Neira Ayuso <[email protected]> wrote:
> On Wed, Feb 14, 2018 at 07:02:32PM +0200, Mantas Mikulėnas wrote:
> > Hello,
> >
> > As of nftables 0.8.1, it seems I can no longer write anonymous sets
> > which contain overlapping networks (CIDR masks).
> >
> > For example, I want to write the following ruleset:
> >
> > #!/usr/bin/nft -f
> > define users = { 10.0.0.0/8, 193.219.181.192/26 }
> > define admins = { 10.123.0.0/24, 31.220.42.129 }
> > define allowed = { $users, $admins }
> > table inet filter {
> > chain foobar {
> > ip saddr $allowed accept
> > }
> > }
> >
> > results in an error message:
> >
> > Error: interval overlaps with previous one
> >
> > I noticed a few nftables.git commits related to disabling auto-merge
> > for interval sets... but mine don't have the 'interval' flag, and
> > there doesn't seem to be any way to specify 'auto-merge' for anonymous
> > sets, either.
>
> I would like not to enable this by default since typo in rulesets
> could go through unnoticed.
nft add rule filter input ip protocol '{6 ,tcp }'
works just fine, eliminating duplicate set elements.
So I don't see how that is different from removing the redundant parts
of an anon set.
Especially with 'define' things I believe that automerge by default
is desireable.
> So the two alternatives I see are:
>
> 1) add per-table configuration options, this would allow us to
> enable auto-merge explicitly for all anonymous sets. This is also
> required if we want to allow user to select "policy memory;" for
> anonymous sets. Only problem with this approach is that this needs
> a kernel patch, so it will take a while to restore the behaviour you
> want since we need a new NFTA_TABLE_USERDATA attribute to store user
> preferences on this.
Right.
> 2) We add a -m option that we can combine with -f for this, which
> globally enables auto-merge for every set, including anonymous and
> named sets.
What about doing automerge by default again for anon sets?
I know you don't like it but it restores old behaviour.
We could have a debug option that tells users which addresse(s) were
autoremoved.
The typo argument -- not sure its a valid:
Consider '10.0.0.01' (instead of .10), we don't try to be 'smart'
and thats a good thing.
For named sets, the no automerge makes sense because it seems like
we can't make any reasonable default choice when users try to delete
a no-longer existing (i.e. merged) element.
But that problem doesn't exist with constant (anon or not) sets.
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