netdev - Re: [PATCH bpf-next 02/11] bpfilter: Add logging facility

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Message-ID: <20210521064645.xhligmlrremyva4q@amnesia>
Date:   Fri, 21 May 2021 10:46:45 +0400
From:   Dmitrii Banshchikov <me@...que.spb.ru>
To:     Song Liu <songliubraving@...com>
Cc:     Song Liu <song@...nel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, Andrey Ignatov <rdna@...com>
Subject: Re: [PATCH bpf-next 02/11] bpfilter: Add logging facility

On Thu, May 20, 2021 at 04:35:45PM +0000, Song Liu wrote:
> 
> 
> > On May 20, 2021, at 12:08 AM, Dmitrii Banshchikov <me@...que.spb.ru> wrote:
> > 
> > On Wed, May 19, 2021 at 10:32:25AM -0700, Song Liu wrote:
> >> On Tue, May 18, 2021 at 11:05 PM Dmitrii Banshchikov <me@...que.spb.ru> wrote:
> >>> 
> >>> There are three logging levels for messages: FATAL, NOTICE and DEBUG.
> >>> When a message is logged with FATAL level it results in bpfilter
> >>> usermode helper termination.
> >> 
> >> Could you please explain why we choose to have 3 levels? Will we need
> >> more levels,
> >> like WARNING, ERROR, etc.?
> > 
> > 
> > I found that I need one level for development - to trace what
> > goes rignt and wrong. At the same time as those messages go to
> > dmesg this level is too verbose to be used under normal
> > circumstances. That is why another level is introduced. And the
> > last one exists to verify invariants or error condintions from
> > which there is no right way to recover and they result in
> > bpfilter termination.
> 
> /dev/kmsg supports specifying priority of the message. Like:
> 
>    echo '<4> This message have priority of 4' > /dev/kmsg
> 
> Therefore, with proper priority settings, we can have more levels safely.
> Does this make sense?

Yes, it makes.
BPFILTER_FATAL should be renamed to BPFILTER_EMERG to match
printk() counterpart. All bpfilter log levels should match
printk() levels. All bpfilter log messages should include log
level. And BPFILTER_DEBUG should be easily turned on/off during
compilation to enable tracing/debug.


> 
> Thanks,
> Song
> 
> [...]
> 

-- 

Dmitrii Banshchikov