linux-kernel - Re: [PATCH 5.10 038/146] mptcp: do not warn on bad input from the network

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Message-ID: <254a0b83518083416abdae4cd27659bc10760773.camel@redhat.com>
Date:   Wed, 23 Jun 2021 18:36:12 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 038/146] mptcp: do not warn on bad input from the
 network

Hello,

On Wed, 2021-06-23 at 16:22 +0200, Pavel Machek wrote:
> Hi!
> 
> > From: Paolo Abeni <pabeni@...hat.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.

Cheers,

Paolo