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Date:   Tue, 16 Aug 2022 00:40:11 +0200
From:   Florian Westphal <fw@strlen.de>
To:     Toke =?iso-8859-15?Q?H=F8iland-J=F8rgensen?= <toke@kernel.org>
Cc:     Daniel Xu <dxu@dxuuu.xyz>, bpf@vger.kernel.org, ast@kernel.org,
        daniel@iogearbox.net, andrii@kernel.org, memxor@gmail.com,
        pablo@netfilter.org, fw@strlen.de, netfilter-devel@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next 2/3] bpf: Add support for writing to nf_conn:mark
Message-ID: <20220815224011.GA9821@breakpoint.cc>
References: <cover.1660592020.git.dxu@dxuuu.xyz>
 <f850bb7e20950736d9175c61d7e0691098e06182.1660592020.git.dxu@dxuuu.xyz>
 <871qth87r1.fsf@toke.dk>
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Toke H?iland-J?rgensen <toke@kernel.org> wrote:
> > 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@dxuuu.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?

I don't see why ct->mark needs special handling.

It might be possible we need to change accesses on nf/tc side to use
READ/WRITE_ONCE though.