netdev - Re: [PATCH net-next 2/3] bpf: add TCP_BPF_RTO_MAX for bpf

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Message-ID: <Z66DL7uda3fwNQfH@mini-arch>
Date: Thu, 13 Feb 2025 15:41:35 -0800
From: Stanislav Fomichev <stfomichev@...il.com>
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, 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, horms@...nel.org,
	ncardwell@...gle.com, kuniyu@...zon.com, bpf@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] bpf: add TCP_BPF_RTO_MAX for bpf_setsockopt

On 02/13, Jason Xing wrote:
> Support bpf_setsockopt() to set the maximum value of RTO for
> BPF program.
> 
> Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> ---
>  Documentation/networking/ip-sysctl.rst | 3 ++-
>  include/uapi/linux/bpf.h               | 2 ++
>  net/core/filter.c                      | 6 ++++++
>  tools/include/uapi/linux/bpf.h         | 2 ++
>  4 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
> index 054561f8dcae..78eb0959438a 100644
> --- a/Documentation/networking/ip-sysctl.rst
> +++ b/Documentation/networking/ip-sysctl.rst
> @@ -1241,7 +1241,8 @@ tcp_rto_min_us - INTEGER
>  
>  tcp_rto_max_ms - INTEGER
>  	Maximal TCP retransmission timeout (in ms).
> -	Note that TCP_RTO_MAX_MS socket option has higher precedence.
> +	Note that TCP_BPF_RTO_MAX and TCP_RTO_MAX_MS socket option have the
> +	higher precedence for configuring this setting.
 
The cover letter needs more explanation about the motivation. And
the precedence as well.

WRT precedence, can you install setsockopt cgroup program and filter out
calls to TCP_RTO_MAX_MS?