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

From: Lukas Wunner <lukas@wunner.de>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Jozsef Kadlecsik <kadlec@netfilter.org>,
	Florian Westphal <fw@strlen.de>,
	netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
	netdev@vger.kernel.org, Martin Mares <mj@ucw.cz>,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH nf-next,RFC 0/5] Netfilter egress hook
Date: Wed, 4 Mar 2020 10:50:32 +0100	[thread overview]
Message-ID: <20200304095032.s6ypvmo45d75wkr7@wunner.de> (raw)
In-Reply-To: <20191107225149.5t4sg35b5gwuwawa@salvia>

On Thu, Nov 07, 2019 at 11:51:49PM +0100, Pablo Neira Ayuso wrote:
> 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?

Just a gentle ping for this series.  I'd still be very interested to
get it upstream.  When posting the above-quoted RFC, Daniel NAK'ed it
saying that "weak justification" was provided "for something that sits
in critical fastpath".

However I followed up with numbers showing that the series actually
results in a speedup rather than a slowdown if the feature isn't used:

https://lore.kernel.org/netfilter-devel/20191123131108.dlnrbutabh5i55ix@wunner.de/

So what's the consensus?  Shall I post a non-RFC version, rebased on
current nf-next/master?

Thanks!

Lukas