netdev - Re: [PATCH bpf-next 2/3] bpf: Add support for writing to nf

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Message-Id: <7556b140-7d73-4411-86c5-f827cfb9f2ae@www.fastmail.com>
Date:   Mon, 15 Aug 2022 16:41:11 -0600
From:   "Daniel Xu" <dxu@...uu.xyz>
To:     Toke Høiland-Jørgensen <toke@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "Alexei Starovoitov" <ast@...nel.org>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        "Andrii Nakryiko" <andrii@...nel.org>,
        "Kumar Kartikeya Dwivedi" <memxor@...il.com>
Cc:     pablo@...filter.org, fw@...len.de, netfilter-devel@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 2/3] bpf: Add support for writing to nf_conn:mark

Hi Toke,

On Mon, Aug 15, 2022, at 4:25 PM, Toke Høiland-Jørgensen wrote:
> Daniel Xu <dxu@...uu.xyz> writes:
>
>> Support direct writes to nf_conn:mark from TC and XDP prog types. This
>> is useful when applications want to store per-connection metadata. This
>> is also particularly useful for applications that run both bpf and
>> iptables/nftables because the latter can trivially access this metadata.
>>
>> One example use case would be if a bpf prog is responsible for advanced
>> packet classification and iptables/nftables is later used for routing
>> due to pre-existing/legacy code.
>>
>> Signed-off-by: Daniel Xu <dxu@...uu.xyz>
>
> Didn't we agree the last time around that all field access should be
> using helper kfuncs instead of allowing direct writes to struct nf_conn?

Sorry, I was not aware of those discussions. Do you have a link handy?

I received the suggestion to enable direct writes here:
https://lore.kernel.org/bpf/CAP01T74aWUW-iyPCV_VfASO6YqfAZmnkYQMN2B4L8ngMMgnAcw@mail.gmail.com/ .

Thanks,
Daniel