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

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Message-ID: <86453e67-d5dc-4565-bdd6-6383273ed819@linux.dev>
Date: Thu, 13 Feb 2025 21:41:33 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: Stanislav Fomichev <stfomichev@...il.com>, 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, 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 2/13/25 7:09 PM, Jason Xing wrote:
> On Fri, Feb 14, 2025 at 10:14 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>>
>> On 2/13/25 3:57 PM, Jason Xing wrote:
>>> On Fri, Feb 14, 2025 at 7:41 AM Stanislav Fomichev<stfomichev@...il.com> wrote:
>>>> 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.
>>
>> +1
>>
>> I haven't looked at the patches. The cover letter has no word on the use case.

The question was your _use case_ in bpf. Not what the TCP_RTO_MAX_MS does. Your 
current use case is to have bpf setting it after reading the tcp header option, 
like the selftest in patch 3?

> 
> I will add and copy some words from Eric's patch series :)


>>> I am targeting the net-next tree because of recent changes[1] made by
>>> Eric. It probably hasn't merged into the bpf-next tree.
>>
>> There is the bpf-next/net tree. It should have the needed changes.
> 
> [1] was recently merged in the net-next tree, so the only one branch I
> can target is net-next.
> 
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=ae9b3c0e79bc
> 
> Am I missing something?

There is a net branch:
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git