Re: [PATCH net-next] net: bpf: add hook for close of tcp timewait sock

[Alexei Starovoitov]

On Wed, Dec 29, 2021 at 3:33 AM <menglong8.dong@xxxxxxxxx> wrote:
>
> From: Menglong Dong <imagedong@xxxxxxxxxxx>
>
> 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.