netdev - Fwd: [PATCH] tcp: Add skb addr and sock addr to arguments of tracepoint tcp

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Date: Thu, 29 Feb 2024 18:26:35 +0800
From: yuanli fu <fuyuanli0722@...il.com>
To: netdev@...r.kernel.org
Subject: Fwd: [PATCH] tcp: Add skb addr and sock addr to arguments of
 tracepoint tcp_probe.

---------- Forwarded message ---------
发件人： yuanli fu <fuyuanli0722@...il.com>
Date: 2024年2月29日周四 16:27
Subject: Re: [PATCH] tcp: Add skb addr and sock addr to arguments of
tracepoint tcp_probe.
To: Jason Xing <kerneljasonxing@...il.com>


Jason Xing <kerneljasonxing@...il.com> 于2024年2月29日周四 15:30写道：
>
> 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.
Got it, thanks.
>
> > ---
> >  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.
>
Got it, I will add to printk
> May I ask how it could be useful if there is no more function printing
> such information in the receive path?
We can get seq and end_seq by skbaddr in netif_receive_skb, so latency
between l2->l4 can be calculated.
>
> Thanks,
> Jason
> > --
> > 2.17.1
> >
> >
>
thanks
fuyuanli