netdev - Re: [PATCH v2 bpf-next 3/4] net: netfilter: add bpf_ct_set_nat

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Message-ID: <CAADnVQJ4XtFpsEsPRC-cepfQvXr-hN7e_3L5SchieeGHH40_4A@mail.gmail.com>
Date:   Tue, 6 Sep 2022 21:27:33 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>,
        netfilter-devel <netfilter-devel@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>
Subject: Re: [PATCH v2 bpf-next 3/4] net: netfilter: add bpf_ct_set_nat_info
 kfunc helper

On Mon, Sep 5, 2022 at 6:14 AM Lorenzo Bianconi <lorenzo@...nel.org> wrote:
> +int bpf_ct_set_nat_info(struct nf_conn___init *nfct__ref,
> +                       union nf_inet_addr *addr, __be16 *port,
> +                       enum nf_nat_manip_type manip)
> +{
...
> @@ -437,6 +483,7 @@ BTF_ID_FLAGS(func, bpf_ct_set_timeout, KF_TRUSTED_ARGS)
>  BTF_ID_FLAGS(func, bpf_ct_change_timeout, KF_TRUSTED_ARGS)
>  BTF_ID_FLAGS(func, bpf_ct_set_status, KF_TRUSTED_ARGS)
>  BTF_ID_FLAGS(func, bpf_ct_change_status, KF_TRUSTED_ARGS)
> +BTF_ID_FLAGS(func, bpf_ct_set_nat_info)
>  BTF_SET8_END(nf_ct_kfunc_set)

Instead of __ref and patch 1 and 2 it would be better to
change the meaning of "trusted_args".
In this case "addr" and "port" are just as "trusted".
They're not refcounted per verifier definition,
but they need to be "trusted" by the helper.
At the end the "trusted_args" flags would mean
"this helper can assume that all pointers can be safely
accessed without worrying about lifetime".