netdev - Re: [RFC PATCH] tcp: Replace possible syn attack msg by counters

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Message-ID: <1313044387.3066.8.camel@edumazet-laptop>
Date:	Thu, 11 Aug 2011 08:33:07 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	therbert@...gle.com, netdev@...r.kernel.org
Subject: Re: [RFC PATCH] tcp: Replace possible syn attack msg by counters

Le mercredi 10 août 2011 à 23:13 -0700, David Miller a écrit :
> From: Tom Herbert <therbert@...gle.com>
> Date: Wed, 10 Aug 2011 22:38:02 -0700 (PDT)
> 
> > Rather than printing the message to the log, use a mib counter to keep
> > track of the count of occurences of syn cookies being used or syn
> > being dropped when request queue is full.
> > 
> > Rationale is these messages can fill up /var/log/messages on server
> > which is simply under heavy load... I'm not sure how much more useful
> > they would be in identifying a server DOS attack (compared to
> > counters).
> > 
> > Signed-off-by: Tom Herbert <therbert@...gle.com>
> 
> Print the message once, and also do the counters.
> 
> Say something like "Possible SYN flooding, see SNMP counters." or
> similar.
> 
> Because if people are grepping for that message in their logs, they
> will now have a false sense of confidence seeing it not being there
> any more.

An alternative would be to guard the message by net_msg_warn
(/proc/sys/net/core/warnings)

LIMIT_NETDEBUG(KERN_INFO "TCP: Possible SYN flooding on port %d. %s.\n" 
	...)



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