netdev - Re: [PATCH net-next 1/9] net-timestamp: add bpf infrastructure to allow exposing more information later

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Message-ID: <67057db07a8c6_1a4199294b6@willemb.c.googlers.com.notmuch>
Date: Tue, 08 Oct 2024 14:45:04 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jason Xing <kerneljasonxing@...il.com>, 
 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, 
 martin.lau@...ux.dev, 
 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
Cc: bpf@...r.kernel.org, 
 netdev@...r.kernel.org, 
 Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next 1/9] net-timestamp: add bpf infrastructure to
 allow exposing more information later

Jason Xing wrote:
> From: Jason Xing <kernelxing@...cent.com>
> 
> Implement basic codes so that we later can easily add each tx points.
> Introducing BPF_SOCK_OPS_ALL_CB_FLAGS used as a test statement can help use
> control whether to output or not.
> 
> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> ---
>  include/uapi/linux/bpf.h       |  5 ++++-
>  net/core/skbuff.c              | 18 ++++++++++++++++++
>  tools/include/uapi/linux/bpf.h |  5 ++++-
>  3 files changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index c6cd7c7aeeee..157e139ed6fc 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6900,8 +6900,11 @@ enum {
>  	 * options first before the BPF program does.
>  	 */
>  	BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG = (1<<6),
> +	/* Call bpf when the kernel is generating tx timestamps.
> +	 */
> +	BPF_SOCK_OPS_TX_TIMESTAMPING_OPT_CB_FLAG = (1<<7),
>  /* Mask of all currently supported cb flags */
> -	BPF_SOCK_OPS_ALL_CB_FLAGS       = 0x7F,
> +	BPF_SOCK_OPS_ALL_CB_FLAGS       = 0xFF,
>  };
>  
>  /* List of known BPF sock_ops operators.
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 74149dc4ee31..5ff1a91c1204 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -5539,6 +5539,21 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
>  }
>  EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
>  
> +static bool bpf_skb_tstamp_tx(struct sock *sk, u32 scm_flag,
> +			      struct skb_shared_hwtstamps *hwtstamps)
> +{
> +	struct tcp_sock *tp;
> +
> +	if (!sk_is_tcp(sk))
> +		return false;
> +
> +	tp = tcp_sk(sk);
> +	if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_TX_TIMESTAMPING_OPT_CB_FLAG))
> +		return true;
> +
> +	return false;
> +}
> +
>  void __skb_tstamp_tx(struct sk_buff *orig_skb,
>  		     const struct sk_buff *ack_skb,
>  		     struct skb_shared_hwtstamps *hwtstamps,
> @@ -5551,6 +5566,9 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
>  	if (!sk)
>  		return;
>  
> +	if (bpf_skb_tstamp_tx(sk, tstype, hwtstamps))
> +		return;
> +

Eventually, this whole feature could probably be behind a
static_branch.