netdev - Re: [PATCH RFC bpf-next 2/2] bpf: Enable bpf_skc_to_* sock casting helper to networking prog type

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Message-ID: <20200915053556.jvunz3rvlnlu46jp@kafai-mbp.dhcp.thefacebook.com>
Date:   Mon, 14 Sep 2020 22:36:47 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Lorenz Bauer <lmb@...udflare.com>
CC:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>,
        Networking <netdev@...r.kernel.org>, Yonghong Song <yhs@...com>
Subject: Re: [PATCH RFC bpf-next 2/2] bpf: Enable bpf_skc_to_* sock casting
 helper to networking prog type

On Mon, Sep 14, 2020 at 12:43:04PM -0700, Martin KaFai Lau wrote:
> For other ARG_PTR_TO_SOCK_COMMON helpers, they are not available to
> the tracing prog type.  Hence, they are fine to accept PTR_TO_BTF_ID
> as ARG_PTR_TO_SOCK_COMMON since the only way for non tracing prog to
> get a PTR_TO_BTF_ID is from casting helpers bpf_skc_to_* and
> the NULL check on return value must be done first.
After looking more, it may not work well.  For example, reading
request_sock->sk.

Need to think a bit.  May try out another idea tomorrow or consider adding
the OR_NULL arg as you mentioned.