[Freedombox-discuss] [tor-relays] Running Obfsproxy on a Raspberry Pi

Eugen Leitl eugen at leitl.org
Sun Jun 2 09:56:12 UTC 2013

----- Forwarded message from torsion at ftml.net -----

Date: Sat, 01 Jun 2013 13:56:02 -0700
From: torsion at ftml.net
To: tor-relays at lists.torproject.org
Subject: Re: [tor-relays] Running Obfsproxy on a Raspberry Pi
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Reply-To: tor-relays at lists.torproject.org

On Sat, Jun 1, 2013, at 12:43 PM, Richard Budd wrote:

Don't know how common this is but I've had a Pi running for 35 days 6
hours (so far). With over 80GB transferred on my half assed
comcast cable connection.
Not bad for $25 a credit card sized board sitting in a cardboard box in
my broom closet.
I think I'm going to give one to everyone of my family members
preloaded with Tor. Plug it into their cable router and let it run.
That would be another 4 bridges added to the total. If we could get
another 100 people to do this it it might be a good way to add capacity
with very little cost or power use.

Be warned, I've found that if you run a Pi as a relay and give it
enough bandwidth, bursts of circuit creation can cause it to crash or
freeze.  This was dedicating about 1Mbps to it.  As a bridge it'd
likely be just fine, and this was something I considered as well.  If
your relatives can't service it though you might consider rigging
something that would powercycle it once a day in case it locks up.  I
use electromechanical timers with 15-min increments for this purpose
with an ancient laser printer and dodgy (but free) WAP.

I've found a number of optimizations to config files (mainly in kernel
networking settings) that vastly reduce the number of lockups on a Pi
that's relaying 1Mbps, but so far haven't eliminated them, they're
mostly caused by huge bursts of circuit creation.  Unfortunately I've
had no time to work on this in recent weeks and am just about to travel
for a week, but I was considering trying to write some kind of iptables
"clamping" script, or otherwise figure out the right combination of
.torrc and iptables limits to keep the Pi from crashing when this kind
of network activity occurs.

I see these circuit creation storms on my much bigger relays, too, but
since they're running on much bigger machines, they've never caused a
crash.  The Pi is quite a bit more limited.  Nobody on the list has
made a stab at explaining this behavior yet.

tor-relays mailing list
tor-relays at lists.torproject.org

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