netdev - Re: [PATCH net-next 2/5] tcp: bpf: support bpf_getsockopt for TCP_BPF_DELACK

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Message-ID: <4c5e97c4-2311-4a4f-9340-5e4a1c7d0e2b@linux.dev>
Date: Mon, 10 Mar 2025 18:21:45 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, dsahern@...nel.org, 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,
 kuniyu@...zon.com, ncardwell@...gle.com, bpf@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/5] tcp: bpf: support bpf_getsockopt for
 TCP_BPF_DELACK_MAX

On 3/9/25 5:30 AM, Jason Xing wrote:
> Support bpf_getsockopt if application tries to know what the delayed ack
> max time is.
> 
> Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> ---
>   net/core/filter.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 31aef259e104..5564917e0c6d 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5415,6 +5415,17 @@ static int sol_tcp_sockopt(struct sock *sk, int optname,
>   		if (*optlen < 1)
>   			return -EINVAL;
>   		break;
> +	case TCP_BPF_DELACK_MAX:
> +		if (*optlen != sizeof(int))
> +			return -EINVAL;
> +		if (getopt) {
> +			int delack_max = inet_csk(sk)->icsk_delack_max;
> +			int delack_max_us = jiffies_to_usecs(delack_max);
> +
> +			memcpy(optval, &delack_max_us, *optlen);
> +			return 0;
> +		}
> +		return bpf_sol_tcp_setsockopt(sk, optname, optval, *optlen);

There are three TCP_BPF_* specific optnames supported by bpf_getsockopt now.
Please take this chance to create a bpf_sol_tcp_getsockopt and refactor the 
existing bpf_getsockopt(TCP_BPF_SOCK_OPS_CB_FLAGS) support into it also. The new 
bpf_sol_tcp_getsockopt can reject the TCP_BPF_IW and TCP_BPF_SNDCWND_CLAMP.