From: Florian Westphal <fw@strlen.de>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Dan Williams <dcbw@redhat.com>, netfilter-devel@vger.kernel.org
Subject: Re: [PATCH v3] libiptc: don't set_changed() when checking rules with module jumps
Date: Tue, 28 Feb 2017 13:03:07 +0100 [thread overview]
Message-ID: <20170228120307.GA6834@breakpoint.cc> (raw)
In-Reply-To: <20170228113312.GA19580@salvia>
Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> On Sat, Feb 25, 2017 at 10:02:03PM -0600, Dan Williams wrote:
> > Checking a rule that includes a jump to a module-based target currently
> > sets the "changed" flag on the handle, which then causes TC_COMMIT() to
> > run through the whole SO_SET_REPLACE/SO_SET_ADD_COUNTERS path. This
> > seems wrong for simply checking rules, an operation which is documented
> > as "...does not alter the existing iptables configuration..." but yet
> > it clearly could do so.
> >
> > Fix that by ensuring that rule check operations for module targets
> > don't set the changed flag, and thus exit early from TC_COMMIT().
>
> Thanks for explaining. How are you hitting this problem? I'm curious
> to see if I can reproduce it.
Its easy to reproduce.
iptables -t nat -o lo -A POSTROUTING -s 10.2.3.4 -j MASQUERADE
iptables -t nat -o lo -C POSTROUTING -s 10.2.3.4 -j MASQUERADE
you should see (via strace) that 2nd command also issues the iptables
setsockopt calls.
next prev parent reply other threads:[~2017-02-28 12:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-24 18:15 [PATCH] libiptc: don't set_changed() when checking rules with module jumps Dan Williams
2017-02-24 18:25 ` [PATCH v2] " Dan Williams
2017-02-25 10:59 ` Pablo Neira Ayuso
2017-02-26 4:02 ` [PATCH v3] " Dan Williams
2017-02-28 11:33 ` Pablo Neira Ayuso
2017-02-28 12:03 ` Florian Westphal [this message]
2017-02-28 12:18 ` Pablo Neira Ayuso
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