netdev - Re: [PATCH bpf-next v4 1/4] bpf: add BPF_CGROUP_INET_SOCK

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Message-ID: <CAEf4Bzb=vHUC2dgxNEE2fvCZrk9+crmZAp+6kb5U1wLF293cHQ@mail.gmail.com>
Date:   Mon, 6 Jul 2020 16:42:27 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next v4 1/4] bpf: add BPF_CGROUP_INET_SOCK_RELEASE hook

On Mon, Jul 6, 2020 at 4:02 PM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> Implement BPF_CGROUP_INET_SOCK_RELEASE hook that triggers
> on inet socket release. It triggers only for userspace
> sockets, the same semantics as existing BPF_CGROUP_INET_SOCK_CREATE.
>
> The only questionable part here is the sock->sk check
> in the inet_release. Looking at the places where we
> do 'sock->sk = NULL', I don't understand how it can race
> with inet_release and why the check is there (it's been
> there since the initial git import). Otherwise, the
> change itself is pretty simple, we add a BPF hook
> to the inet_release and avoid calling it for kernel
> sockets.
>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
>  include/linux/bpf-cgroup.h | 4 ++++
>  include/uapi/linux/bpf.h   | 1 +
>  kernel/bpf/syscall.c       | 3 +++
>  net/core/filter.c          | 1 +
>  net/ipv4/af_inet.c         | 3 +++
>  5 files changed, 12 insertions(+)
>

Looks good overall, but I have no idea about sock->sk NULL case.

Acked-by: Andrii Nakryiko <andriin@...com>

> diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
> index c66c545e161a..2c6f26670acc 100644
> --- a/include/linux/bpf-cgroup.h
> +++ b/include/linux/bpf-cgroup.h

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