netdev - Re: [PATCH net-next v3 02/14] net-timestamp: allow two features to work parallelly

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Message-ID: <CAL+tcoDB8UvNMfTwmvTJb1JvCGDb3ESaJMszh4-Qa=ey0Yn3Vg@mail.gmail.com>
Date: Wed, 30 Oct 2024 09:23:20 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: willemb@...gle.com, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, dsahern@...nel.org, 
	willemdebruijn.kernel@...il.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, shuah@...nel.org, 
	ykolal@...com, bpf@...r.kernel.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v3 02/14] net-timestamp: allow two features to
 work parallelly

On Wed, Oct 30, 2024 at 7:00 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 10/28/24 4:05 AM, Jason Xing wrote:
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > This patch has introduced a separate sk_tsflags_bpf for bpf
> > extension, which helps us let two feature work nearly at the
> > same time.
> >
> > Each feature will finally take effect on skb_shinfo(skb)->tx_flags,
> > say, tcp_tx_timestamp() for TCP or skb_setup_tx_timestamp() for
> > other types, so in __skb_tstamp_tx() we are unable to know which
> > feature is turned on, unless we check each feature's own socket
> > flag field.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> >   include/net/sock.h |  1 +
> >   net/core/skbuff.c  | 39 +++++++++++++++++++++++++++++++++++++++
> >   2 files changed, 40 insertions(+)
> >
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 7464e9f9f47c..5384f1e49f5c 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -445,6 +445,7 @@ struct sock {
> >       u32                     sk_reserved_mem;
> >       int                     sk_forward_alloc;
> >       u32                     sk_tsflags;
> > +     u32                     sk_tsflags_bpf;
> >       __cacheline_group_end(sock_write_rxtx);
> >
> >       __cacheline_group_begin(sock_write_tx);
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 1cf8416f4123..39309f75e105 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -5539,6 +5539,32 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
> >   }
> >   EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
> >
> > +/* This function is used to test if application SO_TIMESTAMPING feature
> > + * or bpf SO_TIMESTAMPING feature is loaded by checking its own socket flags.
> > + */
> > +static bool sk_tstamp_tx_flags(struct sock *sk, u32 tsflags, int tstype)
> > +{
> > +     u32 testflag;
> > +
> > +     switch (tstype) {
> > +     case SCM_TSTAMP_SCHED:
> > +             testflag = SOF_TIMESTAMPING_TX_SCHED;
> > +             break;
> > +     case SCM_TSTAMP_SND:
> > +             testflag = SOF_TIMESTAMPING_TX_SOFTWARE;
> > +             break;
> > +     case SCM_TSTAMP_ACK:
> > +             testflag = SOF_TIMESTAMPING_TX_ACK;
> > +             break;
> > +     default:
> > +             return false;
> > +     }
> > +     if (tsflags & testflag)
> > +             return true;
> > +
> > +     return false;
> > +}
> > +
> >   static void skb_tstamp_tx_output(struct sk_buff *orig_skb,
> >                                const struct sk_buff *ack_skb,
> >                                struct skb_shared_hwtstamps *hwtstamps,
> > @@ -5549,6 +5575,9 @@ static void skb_tstamp_tx_output(struct sk_buff *orig_skb,
> >       u32 tsflags;
> >
> >       tsflags = READ_ONCE(sk->sk_tsflags);
> > +     if (!sk_tstamp_tx_flags(sk, tsflags, tstype))
>
> I still don't get this part since v2. How does it work with cmsg only
> SOF_TIMESTAMPING_TX_*?
>
> I tried with "./txtimestamp -6 -c 1 -C -N -L ::1" and it does not return any tx
> time stamp after this patch.
>
> I am likely missing something
> or v2 concluded that this behavior change is acceptable?

Sorry, I submitted this series accidentally removing one important
thing which is similar to what Vadim Fedorenko mentioned in the v1
[1]:
adding another member like sk_flags_bpf to handle the cmsg case.

Willem, would it be acceptable to add another field in struct sock to
help us recognise the case where BPF and cmsg works parallelly?

[1]: https://lore.kernel.org/all/662873cb-a897-464e-bdb3-edf01363c3b2@linux.dev/

Thanks,
Jason