linux-kernel - Re: [PATCH] net/tcp: Only produce AO/MD5 logs if there are any keys

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Date: Thu, 4 Jan 2024 16:42:05 +0000
From: Dmitry Safonov <dima@...sta.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Eric Dumazet <edumazet@...gle.com>, "David S. Miller"
 <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>,
 Christian Kujau <lists@...dbynature.de>,
 Salam Noureddine <noureddine@...sta.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, Dmitry Safonov <0x7f454c46@...il.com>
Subject: Re: [PATCH] net/tcp: Only produce AO/MD5 logs if there are any keys

Hi Jakub,

On 1/4/24 15:57, Jakub Kicinski wrote:
> On Thu,  4 Jan 2024 13:42:39 +0000 Dmitry Safonov wrote:
>> User won't care about inproper hash options in the TCP header if they
>> don't use neither TCP-AO nor TCP-MD5. Yet, those logs can add up in
>> syslog, while not being a real concern to the host admin:
>>> kernel: TCP: TCP segment has incorrect auth options set for XX.20.239.12.54681->XX.XX.90.103.80 [S]  
>>
>> Keep silent and avoid logging when there aren't any keys in the system.
>>
>> Side-note: I also defined static_branch_tcp_*() helpers to avoid more
>> ifdeffery, going to remove more ifdeffery further with their help.
> 
> Wouldn't we be better off converting the prints to trace points. 
> The chances for hitting them due to malicious packets feels much
> higher than dealing with a buggy implementation in the wild.

Do you mean a proper stuff like in net/core/net-traces.c or just
lowering the loglevel to net_dbg_ratelimited() [like Christian
originally proposed], which in turns becomes runtime enabled/disabled?

Both seem fine to me, albeit I was a bit reluctant to change it without
a good reason as even pre- 2717b5adea9e TCP-MD5 messages were logged and
some userspace may expect them. I guess we can try and see if anyone
notices/complains over changes to these messages changes or not.

Thanks,
             Dmitry