linux-kernel - Re: [PATCH] tcp: tcp_drop adds `SNMP` and `reason` parameter for tracing

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Date:   Mon, 20 Sep 2021 10:20:33 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Zhongya Yan <yan2228598786@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Brendan Gregg <brendan.d.gregg@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        David Miller <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, Yonghong Song <yhs@...com>,
        Zhongya Yan <2228598786@...com>
Subject: Re: [PATCH] tcp: tcp_drop adds `SNMP` and `reason` parameter for tracing

On Mon, Sep 20, 2021 at 10:15 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Mon, 20 Sep 2021 09:54:02 -0700
> Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> > Also, kernel does not have to explain it in strings, those SNMP
> > counters are already available for user-space, so kernel could
> > just use SNMP enums and let user-space interpret them. In many
> > cases, you are just adding strings for those SNMP enums.
>
> The strings were requested by the networking maintainers.
>
>   https://lore.kernel.org/all/CANn89iJO8jzjFWvJ610TPmKDE8WKi8ojTr_HWXLz5g=4pdQHEA@mail.gmail.com/

I think you misunderstand my point. Eric's point is hex address
vs. string, which I never disagree. With SNMP enum, user-space
can easily interpret it to string too, so at the end you still get strings
but not from kernel. This would at least save a handful of strings
from vmlinux, especially if we expand it beyond TCP.

Thanks.