netdev - Re: [PATCH bpf-next 0/5] add bpf cgroup hooks that trigger on socket close

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Date:   Thu, 17 Jan 2019 17:58:46 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Netdev <netdev@...r.kernel.org>, davem@...emloft.net,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next 0/5] add bpf cgroup hooks that trigger on socket close

On Thu, Jan 17, 2019 at 5:02 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
>
>
> On 01/17/2019 04:41 PM, Stanislav Fomichev wrote:
> > Currently, we have BPF_CGROUP_INET_SOCK_CREATE hook that triggers on
> > socket creation and there is no way to know when the socket is being
> > closed. Add new set of hooks BPF_CGROUP_INET{4,6}_SOCK_RELEASE
> > that trigger when the socket is closed.
> >
>
> Are these hooks enough to capture a disconnect() operation ?
>
> A socket can be reused (different flows) without inet_release() being ever called.
I didn't know about reuse, let me spend some time looking into this.

I mostly thought about the following usecase, where user manually calls close():
sys_close() -> sock_close() -> __sock_release -> inet[6]_release

(I also expected stack to call the release whenever process exits)
>
>
> > Initial intended usecase is to cleanup statistics after POST{4,6}_BIND.
> > Hooks have read-only access to all fields of struct bpf_sock.
> >
> > First patch adds hooks, the rest of the patches add uapi and tests to make
> > sure these hooks work.
> >