netdev - Re: [PATCH net-next] sched: cls: enable verbose logging

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Date:   Mon, 14 May 2018 22:31:46 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jakub Kicinski <kubakici@...pl>,
        David Ahern <dsahern@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Jiri Pirko <jiri@...nulli.us>,
        Alexander Aring <aring@...atatu.com>,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH net-next] sched: cls: enable verbose logging

On Mon, May 14, 2018 at 1:47 PM, Marcelo Ricardo Leitner
<marcelo.leitner@...il.com> wrote:
> On Mon, May 14, 2018 at 01:30:53PM -0700, Cong Wang wrote:
>> On Sun, May 13, 2018 at 1:44 PM, Marcelo Ricardo Leitner
>> <marcelo.leitner@...il.com> wrote:
>> > Currently, when the rule is not to be exclusively executed by the
>> > hardware, extack is not passed along and offloading failures don't
>> > get logged. The idea was that hardware failures are okay because the
>> > rule will get executed in software then and this way it doesn't confuse
>> > unware users.
>> >
>> > But this is not helpful in case one needs to understand why a certain
>> > rule failed to get offloaded. Considering it may have been a temporary
>> > failure, like resources exceeded or so, reproducing it later and knowing
>> > that it is triggering the same reason may be challenging.
>>
>> I fail to understand why you need a flag here, IOW, why not just pass
>> extack unconditionally?
>
> Because (as discussed in the RFC[1], should have linked it here) it
> could confuse users that are not aware of offloading and, in other
> cases, it can be just noise (like it would be right now for ebpf,
> which is mostly used in sw-path).
>
> 1.https://www.mail-archive.com/netdev@vger.kernel.org/msg223016.html

My point is that a TC filter flag should be used for a filter attribute,
logging is apparently not a part of filter. At least, put it into HW offloading,
not in TC filter.

I know DaveM hates module parameters, but a module parameter here
is more suitable than a TC filter flag.