From: Florian Westphal <fw@strlen.de>
To: Leonardo Bras <leonardo@linux.ibm.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>,
Florian Westphal <fw@strlen.de>,
"David S. Miller" <davem@davemloft.net>,
netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Jozsef Kadlecsik <kadlec@netfilter.org>,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Subject: Re: [PATCH v2 1/1] netfilter: nf_tables: fib: Drop IPV6 packages if IPv6 is disabled on boot
Date: Thu, 29 Aug 2019 22:58:32 +0200 [thread overview]
Message-ID: <20190829205832.GM20113@breakpoint.cc> (raw)
In-Reply-To: <b6585989069fd832a65b73d1c4f4319a10714165.camel@linux.ibm.com>
Leonardo Bras <leonardo@linux.ibm.com> wrote:
> On Thu, 2019-08-29 at 17:04 -0300, Leonardo Bras wrote:
> > > Thats a good point -- Leonardo, is the
> > > "net.bridge.bridge-nf-call-ip6tables" sysctl on?
> >
> > Running
> > # sudo sysctl -a
> > I can see:
> > net.bridge.bridge-nf-call-ip6tables = 1
>
> Also, doing
> # echo 0 > /proc/sys/net/bridge/bridge-nf-call-ip6tables
> And then trying to boot the guest will not crash the host.
>
> Which would make sense, since host iptables is not dealing with guest
> IPv6 packets.
Yes.
> So, the real cause of this bug is the bridge making host ip6tables deal
> with guest IPv6 packets ?
> If so, would it be ok if write a patch testing ipv6_mod_enabled()
> before passing guest ipv6 packets to host ip6tables?
I'm not sure. This switch is very old, it was added 10 years ago
in v2.6.31-rc1.
Even if we disable call-ip6tables in br_netfilter we will at least
in addition need a patch for nft_fib_netdev.c.
From a "avoid calls to ipv6 stack when its disabled" standpoint,
the safest fix is to disable call-ip6tables functionality if ipv6
module is off *and* fix nft_fib_netdev.c to BREAK in ipv6 is off case.
I started to place a list of suspicous modules here, but that got out
of hand quickly.
So, given I don't want to plaster ipv6_mod_enabled() everywhere, I
would suggest this course of action:
1. add a patch to BREAK in nft_fib_netdev.c for !ipv6_mod_enabled()
2. change net/bridge/br_netfilter_hooks.c, br_nf_pre_routing() to
make sure ipv6_mod_enabled() is true before doing the ipv6 stack
"emulation".
Makes sense?
Thanks,
Florian
next prev parent reply other threads:[~2019-08-29 20:58 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 14:15 [PATCH v2 1/1] netfilter: nf_tables: fib: Drop IPV6 packages if IPv6 is disabled on boot Leonardo Bras
2019-08-27 10:35 ` Pablo Neira Ayuso
2019-08-27 17:34 ` Leonardo Bras
2019-08-27 18:51 ` Pablo Neira Ayuso
2019-08-27 18:55 ` Leonardo Bras
2019-08-27 21:19 ` David Miller
2019-08-27 21:58 ` Florian Westphal
2019-08-28 8:19 ` Pablo Neira Ayuso
2019-08-28 10:17 ` Florian Westphal
2019-08-29 20:04 ` Leonardo Bras
2019-08-29 20:29 ` Leonardo Bras
2019-08-29 20:58 ` Florian Westphal [this message]
2019-08-30 14:15 ` Leonardo Bras
2019-08-30 15:48 ` Leonardo Bras
2019-08-30 15:58 ` Florian Westphal
2019-08-30 18:16 ` Leonardo Bras
2019-08-29 20:29 ` Florian Westphal
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