Re: [iptables PATCH v2 00/17] Eliminate dedicated arptables-nft parser

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On Fri, Oct 15, 2021 at 01:01:24PM +0200, Phil Sutter wrote:
> Hi Pablo,
> 
> On Thu, Oct 14, 2021 at 10:56:09PM +0200, Pablo Neira Ayuso wrote:
> > On Thu, Sep 30, 2021 at 04:04:02PM +0200, Phil Sutter wrote:
> > > Commandline parsing was widely identical with iptables and ip6tables.
> > > This series adds the necessary code-changes to unify the parsers into a
> > > common one.
> > > 
> > > Changes since v1:
> > > - Fix patch 12, the parser has to check existence of proto_parse
> > >   callback before dereferencing it. Otherwise arptables-nft segfaults if
> > >   '-p' option is given.
> > 
> > LGTM.
> 
> Thanks for your review!
> 
> > > - Patches 13-17 add all the arptables quirks to restore compatibility
> > >   with arptables-legacy. I didn't consider them important enough to push
> > >   them unless someone complains. Yet breaking existing scripts is bad
> > >   indeed. Please consider them RFC: If you consider (one of) them not
> > >   important, please NACk and I will drop them before pushing.
> > 
> > For patch 13-16, you could display a warning for people to fix their
> > scripts, so this particular (strange) behaviour in some cases can be
> > dropped (at least, 13-15 look like left-over/bugs). For the
> > check_inverse logic, I'd suggest to display a warning too, this is
> > what it was done in iptables time ago to address this inconsistency.
> 
> I wonder how likely it is for someone to rely upon the behaviour. I can
> imagine a script passing an empty interface name and expecting the
> argument to be ignored (patch 13). Though what are the odds someone
> actually calls arptables with '-m something' (patch 14) or a bogus table
> name (patch 15)?

I think this is a leftover/bug that has been there for long time.

> > I'd probably keep back patch 17/17, the max chain name length was
> > reduced by when the revision field was introduced and this resulted in
> > no issue being reported.
> 
> If that's OK with you, I would turn the empty interface name error into
> a warning for arptables-nft, reintroduce the warning for intrapositioned
> negations and drop the remaining quirks as they are likely hiding a bug.

Agreed.



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