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SubjectRe: [PATCH 5.10 038/146] mptcp: do not warn on bad input from the network
On Wed, 23 Jun 2021, Paolo Abeni wrote:

> Hello,
>
> On Wed, 2021-06-23 at 16:22 +0200, Pavel Machek wrote:
>> Hi!
>>
>>> From: Paolo Abeni <pabeni@redhat.com>
>>>
>>> [ Upstream commit 61e710227e97172355d5f150d5c78c64175d9fb2 ]
>>>
>>> warn_bad_map() produces a kernel WARN on bad input coming
>>> from the network. Use pr_debug() to avoid spamming the system
>>> log.
>>
>> So... we switched from WARN _ONCE_ to pr_debug, as many times as we
>> detect the problem.
>>
>> Should this be pr_debug_once?
>
> Thank you for double checking this!
>
> In the MPTCP code, we use pr_debug() statements as a debug tool, e.g.
> when enabled, it could print per-packet info with no restriction.
>
> There are (a few) similar use in the plain TCP code.
>
> pr_debug() is not supposed to be enabled on any production system,
> while the WARN_ONCE could trigger automated tools for irrelevant
> network noise.
>
> I thing pr_debug() is fine here.
>

Hi Pavel -

I agree with Paolo. This is not a frequently encountered condition, even
when turning on this specific pr_debug(). I'd say the previous use of the
_ONCE() variant was mostly because the effects were not optional (not
because of frequency).

For protocol development, pr_debug() is both off by default and more
useful when it _is_ enabled. I'd prefer to keep this patch as-is.

Thanks,


--
Mat Martineau
Intel

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