linux-kernel - Re: [PATCH] tcp: Add skb addr and sock addr to arguments of tracepoint tcp

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Date: Thu, 29 Feb 2024 15:29:56 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: edumazet@...gle.com, rostedt@...dmis.org, mhiramat@...nel.org, 
	mathieu.desnoyers@...icios.com, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	fuyuanli@...iglobal.com
Subject: Re: [PATCH] tcp: Add skb addr and sock addr to arguments of
 tracepoint tcp_probe.

On Thu, Feb 29, 2024 at 1:33 PM fuyuanli <fuyuanli@...iglobal.com> wrote:
>
> It is useful to expose skb addr and sock addr to user in tracepoint
> tcp_probe, so that we can get more information while monitoring
> receiving of tcp data, by ebpf or other ways.
>
> For example, we need to identify a packet by seq and end_seq when
> calculate transmit latency between lay 2 and lay 4 by ebpf, but which is
> not available in tcp_probe, so we can only use kprobe hooking
> tcp_rcv_esatblised to get them. But we can use tcp_probe directly if skb
> addr and sock addr are available, which is more efficient.
>
> Signed-off-by: fuyuanli <fuyuanli@...iglobal.com>

Please target 'net-next' in the title of your v2 patch.

> ---
>  include/trace/events/tcp.h | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
> index 7b1ddffa3dfc..096c15f64b92 100644
> --- a/include/trace/events/tcp.h
> +++ b/include/trace/events/tcp.h
> @@ -258,6 +258,8 @@ TRACE_EVENT(tcp_probe,
>                 __field(__u32, srtt)
>                 __field(__u32, rcv_wnd)
>                 __field(__u64, sock_cookie)
> +               __field(const void *, skbaddr)
> +               __field(const void *, skaddr)
>         ),
>
>         TP_fast_assign(
> @@ -285,6 +287,9 @@ TRACE_EVENT(tcp_probe,
>                 __entry->ssthresh = tcp_current_ssthresh(sk);
>                 __entry->srtt = tp->srtt_us >> 3;
>                 __entry->sock_cookie = sock_gen_cookie(sk);
> +
> +               __entry->skbaddr = skb;
> +               __entry->skaddr = sk;
>         ),
>
>         TP_printk("family=%s src=%pISpc dest=%pISpc mark=%#x data_len=%d snd_nxt=%#x snd_una=%#x snd_cwnd=%u ssthresh=%u snd_wnd=%u srtt=%u rcv_wnd=%u sock_cookie=%llx",

If they are useful, at least you should printk those two addresses
like what trace_kfree_skb() does.

May I ask how it could be useful if there is no more function printing
such information in the receive path?

Thanks,
Jason
> --
> 2.17.1
>
>