netdev - Re: [PATCH nf-next v3 0/3] Netfilter egress hook

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Date:   Fri, 28 Aug 2020 09:14:00 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Lukas Wunner <lukas@...ner.de>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>
Cc:     netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Thomas Graf <tgraf@...g.ch>, Laura Garcia <nevola@...il.com>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH nf-next v3 0/3] Netfilter egress hook

Hi Lukas,

On 8/27/20 10:55 AM, Lukas Wunner wrote:
> Introduce a netfilter egress hook to allow filtering outbound AF_PACKETs
> such as DHCP and to prepare for in-kernel NAT64/NAT46.

Thinking more about this, how will this allow to sufficiently filter AF_PACKET?
It won't. Any AF_PACKET application can freely set PACKET_QDISC_BYPASS without
additional privileges and then dev_queue_xmit() is being bypassed in the host ns.
This is therefore ineffective and not sufficient. (From container side these can
be caught w/ host veth on ingress, but not in host ns, of course, so hook won't
be invoked.)

Thanks,
Daniel