Re: [PATCH nf-next 3/3] netfilter: Introduce egress hook

From: Daniel Borkmann <daniel@iogearbox.net>
To: Lukas Wunner <lukas@wunner.de>, Laura Garcia <nevola@gmail.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>,
	Jozsef Kadlecsik <kadlec@netfilter.org>,
	Florian Westphal <fw@strlen.de>,
	Netfilter Development Mailing list 
	<netfilter-devel@vger.kernel.org>,
	coreteam@netfilter.org, netdev@vger.kernel.org,
	Martin Mares <mj@ucw.cz>, Dmitry Safonov <0x7f454c46@gmail.com>,
	Thomas Graf <tgraf@suug.ch>, Alexei Starovoitov <ast@kernel.org>,
	David Miller <davem@davemloft.net>
Subject: Re: [PATCH nf-next 3/3] netfilter: Introduce egress hook
Date: Tue, 28 Apr 2020 22:11:19 +0200	[thread overview]
Message-ID: <1a27351b-78a8-febc-45d7-6ee2e8ebda9e@iogearbox.net> (raw)
In-Reply-To: <20200423160542.d3f6yef4av2gqvur@wunner.de>

Hey Lukas,

On 4/23/20 6:05 PM, Lukas Wunner wrote:
> On Thu, Apr 23, 2020 at 04:44:44PM +0200, Laura Garcia wrote:
>> On Sun, Mar 15, 2020 at 2:29 PM Pablo Neira Ayuso <pablo@netfilter.org> wrote:
>>> On Sat, Mar 14, 2020 at 01:12:02AM +0100, Daniel Borkmann wrote:
>>>> On 3/13/20 3:55 PM, Pablo Neira Ayuso wrote:
>>>>> We have plans to support for NAT64 and NAT46, this is the right spot
>>>>> to do this mangling. There is already support for the tunneling
>>>>
>>>> But why is existing local-out or post-routing hook _not_ sufficient for
>>>> NAT64 given it being IP based?
>>>
>>> Those hooks are not coming at the end of the IP processing. There is
>>> very relevant IP code after those hooks that cannot be bypassed such
>>> as fragmentation, tunneling and neighbour output. Such transformation
>>> needs to happen after the IP processing, exactly from where Lukas is
>>> proposing.
>>>
>>> [...]
>>>>> infrastructure in netfilter from ingress, this spot from egress will
>>>>> allow us to perform the tunneling from here. There is also no way to
>>>>> drop traffic generated by dhclient, this also allow for filtering such
>>>>> locally generated traffic. And many more.
>>
>> Any chance to continue with this approach? I'm afraid outbound
>> af_packets also could not be filtered without this hook.
> 
> Thanks Laura, good to hear there's interest in the functionality.
> 
> Daniel submitted a revert of this series but didn't cc me:
> 
> https://lore.kernel.org/netdev/bbdee6355234e730ef686f9321bd072bcf4bb232.1584523237.git.daniel@iogearbox.net/
> 
> In the ensuing discussion it turned out that the performance argument
> may be addressed by a rearrangement of sch_handle_egress() and
> nf_egress() invocations.  I could look into amending the series
> accordingly and resubmitting, though I'm currently swamped with
> other work.

The rework of these hooks is still on my todo list, too swamped with
other stuff as well right now, but I'll see to have a prototype this
net-next development cycle.

Thanks,
Daniel