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From: Lukas Wunner <lukas@wunner.de>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>,
	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>
Subject: Re: [PATCH nf-next,RFC 5/5] netfilter: Introduce egress hook
Date: Sat, 23 Nov 2019 15:23:05 +0100
Message-ID: <20191123142305.g2kkaudhhyui22fq@wunner.de> (raw)
In-Reply-To: <d5876ef3-bcee-e0b2-273e-e0405fe17b79@iogearbox.net>

On Thu, Oct 31, 2019 at 11:39:58PM +0100, Daniel Borkmann wrote:
> On 10/31/19 2:41 PM, Lukas Wunner wrote:
> > Commit e687ad60af09 ("netfilter: add netfilter ingress hook after
> > handle_ing() under unique static key") introduced the ability to
> > classify packets on ingress.
> > 
> > Allow the same on egress.
> > 
> > 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.
> 
> Hmm, have you tried tc BPF on the egress hook (via sch_cls_act -> cls_bpf)?

There's another reason I chose netfilter over tc:  I need to activate the
filter from a kernel module, hence need an in-kernel (rather than user space)
API.

netfilter provides that via nf_register_net_hook(), I couldn't find
anything similar for tc.  And an egress netfilter hook seemed like
an obvious missing feature given the presence of an ingress hook.

The module I need this for is out-of-tree:
https://github.com/RevolutionPi/piControl/commit/da199ccd2099

In my experience the argument that a feature is needed for an out-of-tree
module holds zero value upstream.  If there's no in-tree user, the feature
isn't merged, I've seen this more than enough.  Which is why I didn't mention
it in the first place.

For our use case I wouldn't even need the nft user space support which I
posted separately, I just implemented it for completeness and to increase
acceptability of the present series.

Thanks,

Lukas

  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-31 13:41 [PATCH nf-next,RFC 0/5] Netfilter " Lukas Wunner
2019-10-31 13:41 ` [PATCH nf-next,RFC 1/5] netfilter: Clean up unnecessary #ifdef Lukas Wunner
2019-10-31 13:41 ` [PATCH nf-next,RFC 2/5] netfilter: Document ingress hook Lukas Wunner
2019-10-31 13:41 ` [PATCH nf-next,RFC 3/5] netfilter: Rename ingress hook include file Lukas Wunner
2019-10-31 13:41 ` [PATCH nf-next,RFC 4/5] netfilter: Generalize ingress hook Lukas Wunner
2019-10-31 13:41 ` [PATCH nf-next,RFC 5/5] netfilter: Introduce egress hook Lukas Wunner
2019-10-31 22:39   ` Daniel Borkmann
2019-11-23 14:23     ` Lukas Wunner [this message]
2019-11-07 22:51 ` [PATCH nf-next,RFC 0/5] Netfilter " Pablo Neira Ayuso
2019-11-23 13:11   ` Lukas Wunner

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