netdev - syslog spam: TCP segment has incorrect auth options set

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Message-ID: <f6b59324-1417-566f-a976-ff2402718a8d@nerdbynature.de>
Date: Thu, 4 Jan 2024 11:55:44 +0100 (CET)
From: Christian Kujau <lists@...dbynature.de>
To: linux-kernel@...r.kernel.org
cc: netdev@...r.kernel.org, Dmitry Safonov <0x7f454c46@...il.com>, 
    Francesco Ruggeri <fruggeri@...sta.com>, 
    Salam Noureddine <noureddine@...sta.com>, Dmitry Safonov <dima@...sta.com>, 
    David Ahern <dsahern@...nel.org>
Subject: syslog spam: TCP segment has incorrect auth options set

Ever since commit 2717b5adea9e ("net/tcp: Add tcp_hash_fail() ratelimited 
logs") the following is printed, in waves of small floods, to syslog:

 kernel: TCP: TCP segment has incorrect auth options set for XX.20.239.12.54681->XX.XX.90.103.80 [S]

This host is connected to the open internet and serves as a small HTTP and 
SSH login server, not much traffic is happening here. So I'd assume these 
messages to be the result of random internet scans and/or fingerprinting 
attempts or the like. While not really a concern, these messages are 
flooding the dmesg buffer over time :-(

Is there a way to adjust the severity of these messages?

* In include/net/tcp.h this gets logged with tcp_hash_fail(), which is
* defined in include/net/tcp_ao.h and calls net_info_ratelimited(), which
* is in turn defined in include/linux/net.h and calls pr_info().

Can e.g. net_dbg_ratelimited be used instead?

Thanks,
Christian.
-- 
BOFH excuse #78:

Yes, yes, its called a design limitation