any experience with "flakeways"?

Thu Dec 13 17:50:52 PST 2001

>Date: Thu, 13 Dec 2001 14:23:13 -0800
>From: Trevor Pirman <tpirman at mirapoint.com>

>I need to set up a machine that will act as a "flakeway", the term I
>have heard used for an application that randomly drops packets or causes
>timeouts for services such as DNS and routing.

OK.

>I studied up on the net about this, and people talk about it, but no one
>offers where to find any out of the box software.  Maybe they are
>building their own "flakeway"?

>What I want to do is configure a DNS server that causes requests to the
>server to time out.  I set up ipfw on one machine to swallow all tcp and
>udp packets to port 53, and them made this host my DNS server.  This
>worked for some tests I did, but not others.  I need a more robust
>solution.

>Can anyone offer any advice or pointers on how to do this?   Any info
>would be great.

Caveat:  I have not actually done certain parts of this at all, so it
qualifies as "book learning" -- just to tie this in to another thread
recently.  :-}

That said:  were I tasked to do this, my first inclination would be to
set up a (multi-homed, probably) FreeBSD box to accomplish it.

On the box, I would set it up to use "ipfw" (a FreeBSD-specific, vs.
(say) ipfilter) packet-filter.  In addition (and this is where I'd be
venturing in an area where I have no direct experience), I'd set up
something called "dummynet".

This is some code (written originally by Luigi Rizzo) that (quoting from
the dummynet man page):

     dummynet is a system facility that permits the control of traffic going
     through the various network interfaces, by applying bandwidth and queue
     size limitations, and simulating delays and losses.

Since it is fairly usual to set up ipfw rules to pay attention to
protocol types & port numbers (in its role as a packet filter), and
since ipfw rules are used to select packets for dummynet processing, it
should be possible to do a rather good job of simulating just the kind
of lossy network connection you want.  (Indeed; it is my recollection
that the desire to do this sort of thing was precisely the catalyst for
Luigi's work in the first place.)

Cheers,
david (resume at http://www.catwhisker.org/~david/resume.ps)
-- 
David H. Wolfskill				david at catwhisker.org
I believe it would be irresponsible (and thus, unethical) for me to advise,
recommend, or support the use of any product that is or depends on any
Microsoft product for any purpose other than personal amusement.