From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Phil Sutter <phil@nwl.cc>,
Arturo Borrero Gonzalez <arturo@netfilter.org>,
netfilter-devel@vger.kernel.org
Subject: Re: [iptables PATCH] iptables-nft: fix basechain policy configuration
Date: Fri, 2 Oct 2020 14:47:41 +0200 [thread overview]
Message-ID: <20201002124741.GA2232@salvia> (raw)
In-Reply-To: <20201002122852.GC29050@orbyte.nwl.cc>
On Fri, Oct 02, 2020 at 02:28:52PM +0200, Phil Sutter wrote:
> On Fri, Oct 02, 2020 at 02:15:58PM +0200, Pablo Neira Ayuso wrote:
> > On Fri, Oct 02, 2020 at 02:07:32PM +0200, Phil Sutter wrote:
> > > Hi,
> > >
> > > On Fri, Oct 02, 2020 at 01:44:36PM +0200, Arturo Borrero Gonzalez wrote:
> > > > Previous to this patch, the basechain policy could not be properly configured if it wasn't
> > > > explictly set when loading the ruleset, leading to iptables-nft-restore (and ip6tables-nft-restore)
> > > > trying to send an invalid ruleset to the kernel.
> > >
> > > I fear this is not sufficient: iptables-legacy-restore leaves the
> > > previous chain policy in place if '-' is given in dump file. Please try
> > > this snippet from a testcase I wrote:
> > >
> > > $XT_MULTI iptables -P FORWARD DROP
> > >
> > > diff -u -Z <($XT_MULTI iptables-save | grep '^:FORWARD') \
> > > <(echo ":FORWARD DROP [0:0]")
> > >
> > > $XT_MULTI iptables-restore -c <<< "$TEST_RULESET"
> > > diff -u -Z <($XT_MULTI iptables-save | grep '^:FORWARD') \
> > > <(echo ":FORWARD DROP [0:0]")
> >
> > Hm, this is how it works in this patch right?
> >
> > I mean, if '-' is given, chain policy attribute in the netlink message
> > is not set, and the kernel sets chain policy to
> > NFT_CHAIN_POLICY_UNSET.
> >
> > Or am I missing anything?
>
> This is *flushing* iptables-restore. We're dropping the chain first and
> then reinstall it.
OK, so this fix only works with --noflush.
If --noflush is not specified, then it should be possible to extend
the cache to dump the chains, get the existing policy and use it.
There is now a phase to evaluate the cache requirements, so you can
fetch this. Then, from the netlink phase, look up for the existing
policy in the cache and use it.
> Another quirk is that iptables-legacy-restore ignores the counters if
> policy is '-' even if --counters flag was given. (:
OK, so this needs two more fixed on top of this one.
next prev parent reply other threads:[~2020-10-02 12:48 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-02 11:44 [iptables PATCH] iptables-nft: fix basechain policy configuration Arturo Borrero Gonzalez
2020-10-02 12:07 ` Phil Sutter
2020-10-02 12:15 ` Pablo Neira Ayuso
2020-10-02 12:28 ` Phil Sutter
2020-10-02 12:47 ` Pablo Neira Ayuso [this message]
2020-10-02 13:31 ` Phil Sutter
2020-10-02 14:39 ` Pablo Neira Ayuso
2020-10-08 17:31 ` Pablo Neira Ayuso
2020-10-09 8:29 ` Phil Sutter
2020-10-09 8:50 ` Pablo Neira Ayuso
2020-10-09 9:37 ` Phil Sutter
2020-10-09 10:07 ` Reindl Harald
2020-10-09 10:14 ` Phil Sutter
2020-10-09 10:28 ` Reindl Harald
2020-10-09 10:37 ` Jozsef Kadlecsik
2020-10-09 12:04 ` Phil Sutter
2020-10-09 19:05 ` Jozsef Kadlecsik
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