Subject: Re: [PATCH net-next 7/9] net-timestamp: open gate for bpf_setsockopt

From: Martin KaFai Lau <[email-masked]>
Date: Wed, 9 Oct 2024 00:19:10 -0700

On 10/8/24 2:51 AM, Jason Xing wrote:
> From: Jason Xing <[email-masked]>
> 
> Now we allow users to set tsflags through bpf_setsockopt. What I
> want to do is passing SOF_TIMESTAMPING_RX_SOFTWARE flag, so that
> we can generate rx timestamps the moment the skb traverses through
> driver.
> 
> Here is an example:
> 
> case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
> case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
> 	sock_opt = SOF_TIMESTAMPING_RX_SOFTWARE;
> 	bpf_setsockopt(skops, SOL_SOCKET, SO_TIMESTAMPING,
> 		       &sock_opt, sizeof(sock_opt));
> 	break;
> 
> In this way, we can use bpf program that help us generate and report
> rx timestamp.
> 
> Signed-off-by: Jason Xing <[email-masked]>
> ---
>   net/core/filter.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index bd0d08bf76bb..9ce99d320571 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5225,6 +5225,9 @@ static int sol_socket_sockopt(struct sock *sk, int optname,
>   		break;
>   	case SO_BINDTODEVICE:
>   		break;
> +	case SO_TIMESTAMPING_NEW:
> +	case SO_TIMESTAMPING_OLD:

I believe this change was proposed before. It will change the user expectation 
on the sk_error_queue. It needs some bits/fields/knobs for bpf. I think this 
point is similar to other's earlier comments in this thread.

I only have a chance to briefly look at it. I think it is useful. This 
bpf/timestamp feature request has come up before.

A high level comment. The current timestamp should work for non tcp sock? The 
bpf/timestamp solution should be able to also.

sockops is tcp centric. From looking at patch 9 that needs to initialize 4 args, 
this interface feels old and not sure we want to extend to other sock types.
This needs some thoughts.

> +		break;
>   	default:
>   		return -EINVAL;
>   	}