Date: Fri, 3 Apr 2015 18:14:44 +0300 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Hans Petter Selasky <hselasky@FreeBSD.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r281024 - head/share/man/man4 Message-ID: <20150403151444.GC64665@FreeBSD.org> In-Reply-To: <201504031400.t33E094r076234@svn.freebsd.org> References: <201504031400.t33E094r076234@svn.freebsd.org>
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Hans, On Fri, Apr 03, 2015 at 02:00:09PM +0000, Hans Petter Selasky wrote: H> Author: hselasky H> Date: Fri Apr 3 14:00:08 2015 H> New Revision: 281024 H> URL: https://svnweb.freebsd.org/changeset/base/281024 H> H> Log: H> Add more documentation about the "net.inet.ip.random_id" sysctl knob H> and how it can affect information flow between observers. What the hell? At Fri, 3 Apr 2015 15:41:21 +0300 (MSK) you ask: > Will you mind if I rephrase that paragraph in the "inet.4" ... And at Fri, 3 Apr 2015 17:00:14 +0300 (MSK) you commit. You gave 1 hour and 19 minutes for review! Is this acceptable at all? H> MFC after: 1 week Now this sounds like a threat. Please back out this very questionable change, and then it will be discussed. H> Modified: H> head/share/man/man4/inet.4 H> H> Modified: head/share/man/man4/inet.4 H> ============================================================================== H> --- head/share/man/man4/inet.4 Fri Apr 3 13:57:14 2015 (r281023) H> +++ head/share/man/man4/inet.4 Fri Apr 3 14:00:08 2015 (r281024) H> @@ -28,7 +28,7 @@ H> .\" From: @(#)inet.4 8.1 (Berkeley) 6/5/93 H> .\" $FreeBSD$ H> .\" H> -.Dd April 2, 2015 H> +.Dd April 3, 2015 H> .Dt INET 4 H> .Os H> .Sh NAME H> @@ -244,10 +244,22 @@ IP datagrams (or all IP datagrams, if H> .Va ip.rfc6864 H> is disabled) to be randomized instead of incremented by 1 with each packet H> generated. H> -This closes a minor information leak which allows remote observers to H> +This prevents information exchange between any combination of two or H> +more inside and/or outside observers using packet frequency H> +modulation, PFM. H> +An outside observer can ping the outside facing port at a fixed rate H> +sampling the returned counter. H> +An inside observer can ping the inside facing port sampling the same H> +counter. H> +Even though packets don't flow directly between any of the observers H> +any single observer can influence the data rate the other observer(s) H> +is or are sampling. H> +This is done by sending more or less ping packets towards the gateway H> +per measured interval. H> +Setting this sysctl also prevents the remote and internal observers to H> determine the rate of packet generation on the machine by watching the H> counter. H> -In the same time, on high-speed links, it can decrease the ID reuse H> +At the same time, on high-speed links, it can decrease the ID reuse H> cycle greatly. H> Default is 0 (sequential IP IDs). H> IPv6 flow IDs and fragment IDs are always random. H> -- Totus tuus, Glebius.
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