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From: Lowell Gilbert <freebsd-security-local@be-well.ilk.org>
To: "Ronald F. Guilmette" <rfg@tristatelogic.com>
Cc: freebsd-security@freebsd.org
Subject: Re: Logging TCP anomalies
References: <43372.1430159842@server1.tristatelogic.com>
Date: Mon, 27 Apr 2015 15:49:11 -0400
In-Reply-To: <43372.1430159842@server1.tristatelogic.com> (Ronald
 F. Guilmette's message of "Mon, 27 Apr 2015 11:37:22 -0700")
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"Ronald F. Guilmette" <rfg@tristatelogic.com> writes:

> I am prompted to ask here whether or not FreeBSD performs any sort of
> logging of instances when "duplicate TCP packets but with different
> payloads" occurs, and/or whether FreeBSD provides any options which,
> for example, might automagically trigger a close of the relevant TCP
> connection when and if such an event is detected.  (Connection close
> seems to me to be one possible mitigation strategy, even if it might
> be viewed as rather ham-fisted by some.)

As far as I can see, no. This would be a non-trivial application of
resources, so I wouldn't expect to see it be a standard part of the TCP
stack. Such a check would be better implemented as an optional
application of an API like BPF.