From: Florian Westphal <fw@strlen.de>
To: Jozsef Kadlecsik <kadlec@netfilter.org>
Cc: Florian Westphal <fw@strlen.de>,
Francesco Ruggeri <fruggeri@arista.com>,
open list <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
coreteam@netfilter.org, netfilter-devel@vger.kernel.org,
Jakub Kicinski <kuba@kernel.org>,
David Miller <davem@davemloft.net>,
Pablo Neira Ayuso <pablo@netfilter.org>
Subject: Re: [PATCH nf v2] netfilter: conntrack: connection timeout after re-register
Date: Fri, 9 Oct 2020 22:05:48 +0200 [thread overview]
Message-ID: <20201009200548.GG5723@breakpoint.cc> (raw)
In-Reply-To: <alpine.DEB.2.23.453.2010092132220.19307@blackhole.kfki.hu>
Jozsef Kadlecsik <kadlec@netfilter.org> wrote:
> > The "delay unregister" remark was wrt. the "all rules were deleted"
> > case, i.e. add a "grace period" rather than acting right away when
> > conntrack use count did hit 0.
>
> Now I understand it, thanks really. The hooks are removed, so conntrack
> cannot "see" the packets and the entries become stale.
Yes.
> What is the rationale behind "remove the conntrack hooks when there are no
> rule left referring to conntrack"? Performance optimization? But then the
> content of the whole conntrack table could be deleted too... ;-)
Yes, this isn't the case at the moment -- only hooks are removed,
entries will eventually time out.
> > Conntrack entries are not removed, only the base hooks get unregistered.
> > This is a problem for tcp window tracking.
> >
> > When re-register occurs, kernel is supposed to switch the existing
> > entries to "loose" mode so window tracking won't flag packets as
> > invalid, but apparently this isn't enough to handle keepalive case.
>
> "loose" (nf_ct_tcp_loose) mode doesn't disable window tracking, it
> enables/disables picking up already established connections.
>
> nf_ct_tcp_be_liberal would disable TCP window checking (but not tracking)
> for non RST packets.
You are right, mixup on my part.
> But both seems to be modified only via the proc entries.
Yes, we iterate table on re-register and modify the existing entries.
next prev parent reply other threads:[~2020-10-09 20:08 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-07 19:32 [PATCH nf v2] netfilter: conntrack: connection timeout after re-register Francesco Ruggeri
2020-10-08 23:41 ` Francesco Ruggeri
2020-10-09 6:52 ` Jozsef Kadlecsik
2020-10-09 11:03 ` Florian Westphal
2020-10-09 18:48 ` Jozsef Kadlecsik
2020-10-09 18:55 ` Florian Westphal
2020-10-09 19:49 ` Jozsef Kadlecsik
2020-10-09 20:00 ` Francesco Ruggeri
2020-10-09 20:05 ` Florian Westphal [this message]
2020-10-14 0:06 ` Pablo Neira Ayuso
2020-10-14 8:11 ` Pablo Neira Ayuso
2020-10-14 8:23 ` Florian Westphal
2020-10-14 18:42 ` Francesco Ruggeri
2020-10-14 19:35 ` Florian Westphal
2020-10-20 15:21 ` Pablo Neira Ayuso
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