netdev - Re: [PATCH bpf-next v9 02/12] bpf: prepare for timestamping callbacks use

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Message-ID: <CAL+tcoC9-tWb_ogoP--T60WJTniVtA9r=6NMC18iJiNuaKJWxA@mail.gmail.com>
Date: Tue, 11 Feb 2025 10:25:47 +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: [PATCH bpf-next v9 02/12] bpf: prepare for timestamping callbacks use

On Tue, Feb 11, 2025 at 9:32 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 2/8/25 2:32 AM, Jason Xing wrote:
> > Later, four callback points to report information to user space
> > based on this patch will be introduced.
> >
> > As to skb initialization here, users can follow these three steps
> > as below to fetch the shared info from the exported skb in the bpf
> > prog:
> > 1. skops_kern = bpf_cast_to_kern_ctx(skops);
> > 2. skb = skops_kern->skb;
> > 3. shinfo = bpf_core_cast(skb->head + skb->end, struct skb_shared_info);
> >
> > More details can be seen in the last selftest patch of the series.
>
> This BPF program example is not useful in this commit message. It is not how
> this change will be used in the kernel. People will naturally be required to
> look at the selftest to see how the bpf prog can get to the skb and tskey, etc.
>
> The commit message should focus on explaining "what" has changed and "why" it is
> necessary. The "why" part ("four callback points to report...") is mostly
> present but could be clearer.
>
> Subject: bpf: Prepare the sock_ops ctx and call bpf prog for TX timestamping
>
> (What)
> This patch introduces a new bpf_skops_tx_timestamping() function that prepares
> the "struct bpf_sock_ops" ctx and then executes the sockops BPF program.
>
> (Why)
> The subsequent patch will utilize bpf_skops_tx_timestamping() at the existing TX
> timestamping kernel callbacks (__sk_tstamp_tx specifically) to call the sockops
> BPF program.

Thanks, Will update it.

>
>
> >
> > Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> > ---
> >   include/net/sock.h |  7 +++++++
> >   net/core/sock.c    | 15 +++++++++++++++
> >   2 files changed, 22 insertions(+)
> >
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 7916982343c6..6f4d54faba92 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -2923,6 +2923,13 @@ int sock_set_timestamping(struct sock *sk, int optname,
> >                         struct so_timestamping timestamping);
> >
> >   void sock_enable_timestamps(struct sock *sk);
> > +#if defined(CONFIG_CGROUP_BPF)
> > +void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op);
> > +#else
> > +static inline void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op)
> > +{
> > +}
> > +#endif
> >   void sock_no_linger(struct sock *sk);
> >   void sock_set_keepalive(struct sock *sk);
> >   void sock_set_priority(struct sock *sk, u32 priority);
> > diff --git a/net/core/sock.c b/net/core/sock.c
> > index eae2ae70a2e0..41db6407e360 100644
> > --- a/net/core/sock.c
> > +++ b/net/core/sock.c
> > @@ -948,6 +948,21 @@ int sock_set_timestamping(struct sock *sk, int optname,
> >       return 0;
> >   }
> >
> > +#if defined(CONFIG_CGROUP_BPF)
> > +void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op)
> > +{
> > +     struct bpf_sock_ops_kern sock_ops;
> > +
> > +     memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
> > +     sock_ops.op = op;
> > +     sock_ops.is_fullsock = 1;
> > +     sock_ops.sk = sk;
> > +     bpf_skops_init_skb(&sock_ops, skb, 0);
> > +     /* Timestamping bpf extension supports only TCP and UDP full socket */
>
> nit: After our earlier discussions, it's clear that the above is_fullsock = 1;
> is always true for all sk here. This comment has become redundant. Let's remove it.

Will do it.

Thanks,
Jason

>
> > +     __cgroup_bpf_run_filter_sock_ops(sk, &sock_ops, CGROUP_SOCK_OPS);
> > +}
> > +#endif
> > +
> >   void sock_set_keepalive(struct sock *sk)
> >   {
> >       lock_sock(sk);
>