MIME-Version: 1.0
References: <20211229113256.299024-1-imagedong@tencent.com>
In-Reply-To: <20211229113256.299024-1-imagedong@tencent.com>
From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Wed, 29 Dec 2021 08:46:01 -0800
Message-ID: <CAADnVQLY2i+2YTj+Oi7+70e98sRC-t6rr536sc=3WYghpki+ug@mail.gmail.com>
Subject: Re: [PATCH net-next] net: bpf: add hook for close of tcp timewait sock
To:     menglong8.dong@gmail.com
Cc:     Daniel Borkmann <daniel@iogearbox.net>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        Network Development <netdev@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Menglong Dong <imagedong@tencent.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Dec 29, 2021 at 3:33 AM <menglong8.dong@gmail.com> wrote:
>
> From: Menglong Dong <imagedong@tencent.com>
>
> The cgroup eBPF attach type 'CGROUP_SOCK_OPS' is able to monitor the
> state change of a tcp connect with 'BPF_SOCK_OPS_STATE_CB' ops.
>
> However, it can't trace the whole state change of a tcp connect. While
> a connect becomes 'TCP_TIME_WAIT' state, this sock will be release and
> a tw sock will be created. While tcp sock release, 'TCP_CLOSE' state
> change will be passed to eBPF program. Howeven, the real state of this
> connect is 'TCP_TIME_WAIT'.
>
> To make eBPF get the real state change of a tcp connect, add
> 'CGROUP_TWSK_CLOSE' cgroup attach type, which will be called when
> tw sock release and tcp connect become CLOSE.

The use case is not explained.
Why bpf tracing cannot be used to achieve the same?

Also there are no selftests.