netdev - Re: [RFC PATCH net-next v6 11/13] net-timestamp: add a new callback in tcp_tx

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Message-ID: <CAL+tcoDT7KpTSgon-QORLZazgXoCJQHBuwADmV8URH272M2EdA@mail.gmail.com>
Date: Sat, 25 Jan 2025 09:21:35 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, willemdebruijn.kernel@...il.com, 
	willemb@...gle.com, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, horms@...nel.org, bpf@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next v6 11/13] net-timestamp: add a new callback
 in tcp_tx_timestamp()

On Sat, Jan 25, 2025 at 8:50 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 1/20/25 5:28 PM, Jason Xing wrote:
> > Introduce the callback to correlate tcp_sendmsg timestamp with other
> > three points (SND/SW/ACK). We can let bpf trace the beginning of
> > tcp_sendmsg_locked() and fetch the socket addr, so that in
> > tcp_tx_timestamp() we can correlate the tskey with the socket addr.
> > It is accurate since they are under the protect of socket lock.
> > More details can be found in the selftest.
> >
> > Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> > ---
> >   include/uapi/linux/bpf.h       | 3 +++
> >   net/ipv4/tcp.c                 | 1 +
> >   tools/include/uapi/linux/bpf.h | 3 +++
> >   3 files changed, 7 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 3b9bfc88345c..55c74fa18163 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -7042,6 +7042,9 @@ enum {
> >                                        * feature is on. It indicates the
> >                                        * recorded timestamp.
> >                                        */
> > +     BPF_SOCK_OPS_TS_TCP_SND_CB,     /* Called when every tcp_sendmsg
> > +                                      * syscall is triggered
> > +                                      */
>
> I recall we agreed in v5 to adjust the "TCP_" naming part because it will be
> used in UDP also. Like completely remove the "TCP_" from the name?

Right. The thing is that, after that discussion, I altered my thoughts
because I'm not so sure if I need this for UDP (I need more time to
think about the UDP case) which can be trace by fentry, sorry.

I will follow your instructions to remove "TCP_".

Thanks,
Jaosn

>
> >   };
> >
> >   /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
> > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > index 0a41006b10d1..49e489c346ea 100644
> > --- a/net/ipv4/tcp.c
> > +++ b/net/ipv4/tcp.c
> > @@ -500,6 +500,7 @@ static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc)
> >               tcb->txstamp_ack_bpf = 1;
> >               shinfo->tx_flags |= SKBTX_BPF;
> >               shinfo->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;
> > +             bpf_skops_tx_timestamping(sk, skb, BPF_SOCK_OPS_TS_TCP_SND_CB);
> >       }
> >   }
> >
> > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> > index b463aa9c27da..38fc04a7ac20 100644
> > --- a/tools/include/uapi/linux/bpf.h
> > +++ b/tools/include/uapi/linux/bpf.h
> > @@ -7035,6 +7035,9 @@ enum {
> >                                        * feature is on. It indicates the
> >                                        * recorded timestamp.
> >                                        */
> > +     BPF_SOCK_OPS_TS_TCP_SND_CB,     /* Called when every tcp_sendmsg
> > +                                      * syscall is triggered
> > +                                      */
> >   };
> >
> >   /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
>