Re: [PATCH] segtree: bail out on concatenations

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

On Fri, Apr 03, 2020 at 02:27:05PM +0200, Stefano Brivio wrote:
> On Fri, 3 Apr 2020 14:03:51 +0200
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> 
> > On Thu, Apr 02, 2020 at 11:49:41PM +0200, Pablo Neira Ayuso wrote:
> > > This patch adds a lazy check to validate that the first element is not a
> > > concatenation. The segtree code does not support for concatenations,
> > > bail out with EOPNOTSUPP.
> > >
> > >  # nft add element x y { 10.0.0.0/8 . 192.168.1.3-192.168.1.9 . 1024-65535 }
> > >  Error: Could not process rule: Operation not supported
> > >  add element x y { 10.0.0.0/8 . 192.168.1.3-192.168.1.9 . 1024-65535 }
> > >  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > >
> > > Otherwise, the segtree code barfs with:
> > >
> > >  BUG: invalid range expression type concat  
> > 
> > Hm.
> > 
> > I'm afraid this patch is not enough, the following ruleset crashes
> > in old kernels with recent nft:
> > 
> > flush ruleset
> > 
> > table inet filter {
> >         set test {
> >                 type ipv4_addr . ipv4_addr . inet_service
> >                 flags interval,timeout
> >                 elements = { 1.1.1.1 . 2.2.2.2 . 30 ,
> >                              2.2.2.2 . 3.3.3.3 . 40 ,
> >                              3.3.3.3 . 4.4.4.4 . 50 }
> >         }
> > 
> >         chain output {
> >                 type filter hook output priority 0; policy accept;
> >                 ip saddr . ip daddr . tcp dport @test counter
> >         }
> > }
> 
> First off, sorry, it didn't occur to me to run new tests on older
> kernels. :/
> 
> I can't quickly run that on some older kernel right now. For my
> understanding, where is it crashing?

When listing via

        nft list ruleset

The segtree does not know how to handle this concatenation.

The only way I found to prevent this error is to bail out when adding
the set, ie. old kernel checks that NFT_SET_CONCAT is not supported,
hence it bails out.

I'm going to prepare patches to submit this to nf.git.