netdev - Re: [PATCH v4 1/2] netfilter: Terminate rule eval if protocol=IPv6 and ipv6 module is disabled

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Date:   Tue, 3 Sep 2019 22:19:04 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Florian Westphal <fw@...len.de>
Cc:     Leonardo Bras <leonardo@...ux.ibm.com>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v4 1/2] netfilter: Terminate rule eval if protocol=IPv6
 and ipv6 module is disabled

On Tue, Sep 03, 2019 at 09:48:09PM +0200, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@...filter.org> wrote:
> > > > I was expecting we could find a way to handle this from br_netfilter
> > > > alone itself.
> > > 
> > > We can't because we support ipv6 fib lookups from the netdev family
> > > as well.
> > > 
> > > Alternative is to auto-accept ipv6 packets from the nf_tables eval loop,
> > > but I think its worse.
> > 
> > Could we add a restriction for nf_tables + br_netfilter + !ipv6. I
> > mean, if this is an IPv6 packet, nf_tables is on and IPv6 module if
> > off, then drop this packet?
> 
> We could do that from nft_do_chain_netdev().

Indeed, this is all about the netdev case.

Probably add something similar to nf_ip6_route() to deal with
ip6_route_lookup() case? This is the one trigering the problem, right?

BTW, how does nft_fib_ipv6 module kicks in if ipv6 module is not
loaded? The symbol dependency would pull in the IPv6 module anyway.