From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Florian Westphal <fw@strlen.de>
Cc: Jan Engelhardt <jengelh@inai.de>, netfilter-devel@vger.kernel.org
Subject: Re: [PATCH iptabes-nft] iptables-nft: allow removal of empty builtin chains
Date: Sun, 15 Aug 2021 15:49:22 +0200 [thread overview]
Message-ID: <20210815134922.GA10659@salvia> (raw)
In-Reply-To: <20210815132733.GI607@breakpoint.cc>
On Sun, Aug 15, 2021 at 03:27:33PM +0200, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > On Sat, Aug 14, 2021 at 10:53:14PM +0200, Florian Westphal wrote:
> > > Indeed. Since this removes the base chain, it implicitly reverts
> > > a DROP policy too.
> >
> > User still has to iptables -F on that given chain before deleting,
> > right?
>
> Yes, -X fails if the chain has rules.
>
> > If NLM_F_NONREC is used, the EBUSY is reported when trying to delete
> > a chain with rules.
>
> Yes.
But we really do not need NLM_F_NONREC for this new feature, right? I
mean, a quick shortcut to remove the basechain and its content should
be fine.
> > My assumption is that the user will perform:
> >
> > iptables-nft -F -t filter
> > iptables-nft -D -t filter
>
> Yes, assuminy you meant -X instead of -D.
Oh well, embarrasing, yes.
> This behaves just like before, it deletes all rules (-F) and all user-defined
> chains (-X).
>
> > I mean, by when the user has an empty basechain with default policy to
> > DROP, if they remove the chain, then they are really meaning to remove
> > the chain and this default policy to DROP.
>
> ATM iptables -X $BUILTIN will always fail.
> In -legecy there is no kernel API to allow for its removal,
> for -nft there is an extra check that throws an error.
>
> > Or am I missing anything else?
>
> No, I don't think so. I would prefer if
> iptables-nft -F -t filter
> iptables-nft -X -t filter
>
> ... would result in an empty "filter" table.
Your concern is that this would change the default behaviour?
> I could also add a patch that requests removal
> of the table as well for the -X case; but unlike base chain the
> presence of the table alone has no impact on dataplane.
Then, probably add a new command for this?
iptables-nft -K INPUT -t filter => to remove the INPUT/filter basechain.
Then:
iptables-nft -N INPUT -t filter
to bring it back (if it was removed).
next prev parent reply other threads:[~2021-08-15 13:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-14 17:46 [PATCH iptabes-nft] iptables-nft: allow removal of empty builtin chains Florian Westphal
2021-08-14 20:18 ` Jan Engelhardt
2021-08-14 20:53 ` Florian Westphal
2021-08-15 13:12 ` Pablo Neira Ayuso
2021-08-15 13:27 ` Florian Westphal
2021-08-15 13:49 ` Pablo Neira Ayuso [this message]
2021-08-15 14:14 ` Florian Westphal
2021-08-15 14:27 ` Pablo Neira Ayuso
2021-08-15 14:36 ` Florian Westphal
2021-09-13 15:46 ` Phil Sutter
2021-09-13 16:02 ` Florian Westphal
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