netdev - 答复: [PATCH bpf-next] bpf/xdp: Can't detach BPF XDP prog if not exist

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Date:   Thu, 5 May 2022 08:21:15 +0000
From:   shaozhengchao <shaozhengchao@...wei.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>
CC:     "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "hawk@...nel.org" <hawk@...nel.org>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "kafai@...com" <kafai@...com>,
        "songliubraving@...com" <songliubraving@...com>,
        "yhs@...com" <yhs@...com>,
        "kpsingh@...nel.org" <kpsingh@...nel.org>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "imagedong@...cent.com" <imagedong@...cent.com>,
        "petrm@...dia.com" <petrm@...dia.com>,
        "memxor@...il.com" <memxor@...il.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "weiyongjun (A)" <weiyongjun1@...wei.com>,
        yuehaibing <yuehaibing@...wei.com>
Subject: 答复: [PATCH bpf-next] bpf/xdp: Can't detach BPF XDP prog if not exist


-----邮件原件-----
发件人: Toke Høiland-Jørgensen [mailto:toke@...hat.com] 
发送时间: 2022年5月4日 19:20
收件人: shaozhengchao <shaozhengchao@...wei.com>; netdev@...r.kernel.org; linux-kernel@...r.kernel.org; bpf@...r.kernel.org; davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org; pabeni@...hat.com
抄送: ast@...nel.org; daniel@...earbox.net; hawk@...nel.org; john.fastabend@...il.com; andrii@...nel.org; kafai@...com; songliubraving@...com; yhs@...com; kpsingh@...nel.org; bigeasy@...utronix.de; imagedong@...cent.com; petrm@...dia.com; memxor@...il.com; arnd@...db.de; weiyongjun (A) <weiyongjun1@...wei.com>; shaozhengchao <shaozhengchao@...wei.com>; yuehaibing <yuehaibing@...wei.com>
主题: Re: [PATCH bpf-next] bpf/xdp: Can't detach BPF XDP prog if not exist

Zhengchao Shao <shaozhengchao@...wei.com> writes:

> if user sets nonexistent xdp_flags to detach xdp prog, kernel should 
> return err and tell user that detach failed with detail info.
>
> Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>

I kinda see your point, but this will change user-visible behaviour that applications might be relying on, so I don't think we can make this change at this stage. Why can't your application just query the link for whether a program is attached?

-Toke


Thank you for your reply. I wiil change sample application firstly. But if kernel does nothing and return 0, maybe user will think setup is OK, actually It failed. Is this acceptable?