netdev - Re: [PATCH nf-next,RFC 0/5] Netfilter egress hook

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Date:   Thu, 7 Nov 2019 23:51:49 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, Martin Mares <mj@....cz>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH nf-next,RFC 0/5] Netfilter egress hook

Hi,

On Thu, Oct 31, 2019 at 02:41:00PM +0100, Lukas Wunner wrote:
> Introduce a netfilter egress hook to complement the existing ingress hook.
> 
> User space support for nft is submitted in a separate patch.
> 
> The need for this arose because I had to filter egress packets which do
> not match a specific ethertype.  The most common solution appears to be
> to enslave the interface to a bridge and use ebtables, but that's
> cumbersome to configure and comes with a (small) performance penalty.
> An alternative approach is tc, but that doesn't afford equivalent
> matching options as netfilter.  A bit of googling reveals that more
> people have expressed a desire for egress filtering in the past:
> 
> https://www.spinics.net/lists/netfilter/msg50038.html
> https://unix.stackexchange.com/questions/512371
> 
> I am first performing traffic control with sch_handle_egress() before
> performing filtering with nf_egress().  That order is identical to
> ingress processing.  I'm wondering whether an inverse order would be
> more logical or more beneficial.  Among other things it would allow
> marking packets with netfilter on egress before performing traffic
> control based on that mark.  Thoughts?

Would you provide some numbers on the performance impact for this new
hook?

Thanks.