netdev - Re: [PATCH nf-next v3 3/3] netfilter: Introduce egress hook

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Date:   Fri, 4 Sep 2020 10:54:58 +0200
From:   Laura García Liébana <nevola@...il.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Lukas Wunner <lukas@...ner.de>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Netfilter Development Mailing list 
        <netfilter-devel@...r.kernel.org>, coreteam@...filter.org,
        netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Thomas Graf <tgraf@...g.ch>, David Miller <davem@...emloft.net>
Subject: Re: [PATCH nf-next v3 3/3] netfilter: Introduce egress hook

Hi,

On Thu, Sep 3, 2020 at 7:00 AM John Fastabend <john.fastabend@...il.com> wrote:
>
[...]
>
> I don't think it actualy improves performance at least I didn't observe
> that. From the code its not clear why this would be the case either. As
> a nit I would prefer that line removed from the commit message.
>

It hasn't been proven to be untrue either.


[...]
>
> Do you have plans to address the performance degradation? Otherwise
> if I was building some new components its unclear why we would
> choose the slower option over the tc hook. The two suggested
> use cases security policy and DSR sound like new features, any
> reason to not just use existing infrastructure?
>

Unfortunately, tc is not an option as it is required to interact with
nft objects (sets, maps, chains, etc), more complex than just a drop.
Also, when building new features we try to maintain the application
stack as simple as possible, not trying to do ugly integrations.

I understand that you measure performance with a drop, but using this
hook we reduce the datapath consistently for these use cases and
hence, improving traffic performance.

Thank you for your time!