Re: Overlapping IP networks no longer allowed?

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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.

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.

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.

Let me know.
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