[tor-relays] A bit more evidence on circuit creation storms

[Gordon Morehouse <gordon@xxxxxxxxxxxx>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

So, I started having "tubes clogged" problems this evening and
realized, finally, that my Raspberry Pi powered relay had been
weathering a circuit creation storm since about 18:11 my time.

tl;dr main dev-related questions at bottom


Aug 29 18:11:03.000 [warn] Your computer is too slow to handle this
many circuit creation requests! Please consider using the
MaxAdvertisedBandwidth config option or choosing a
more restricted exit policy.
Aug 29 18:12:02.000 [warn] Your computer is too slow to handle this
many circuit creation requests! Please consider using the
MaxAdvertisedBandwidth config option or choosing a
more restricted exit policy. [2692 similar message(s) suppressed in
last 60 seconds]


First off, I'm happy to note that the Pi is far, FAR more able to
weather these storms running 0.2.4.x, even without the perfectly
optimal OpenSSL (all jokes aside about that particular combination of
three words)...

Secondly, the number of messages escalated.  Here is the worst:


Aug 29 18:38:04.000 [warn] Your computer is too slow to handle this
many circuit creation requests! Please consider using the
MaxAdvertisedBandwidth config option or choosing a more restricted
exit policy. [18258 similar message(s) suppressed in last 60 seconds]


What on earth is causing so many circuit creation requests in such a
short timespan?

Again, a Pi-specific note - on 0.2.3.x, the Pi would have crashed or
Tor been killed before this number ever reached five digits, so
0.2.4.x is better!  I has a metric!

However, note that whatever is going on starts plugging up the works
in Tor itself:


Aug 29 18:18:36.000 [notice] Tried for 129 seconds to get a connection
to [scrubbed]:993. Giving up. (waiting for circuit)
Aug 29 18:19:04.000 [warn] Your computer is too slow to handle this
many circuit creation requests! Please consider using the
MaxAdvertisedBandwidth config option or choosing a
more restricted exit policy. [7190 similar message(s) suppressed in
last 60 seconds]
Aug 29 18:19:14.000 [notice] Your network connection speed appears to
have changed. Resetting timeout to 60s after 18 timeouts and 172
buildtimes.


I assure you, my network connection speed didn't change.  I still
don't know how in the Tor protocol a circuit creation request is made,
but maybe it was them gobbling bandwidth.  Probably not, though?
There was an increase in average TX/RX bandwidth during this incident,
but not to levels that are in any way out of the ordinary for how I
use my Internet connection.

However, it's still causing trouble with my router (which is running
Tomato).  Check this out:


Aug 29 18:56:14.000 [warn] Your computer is too slow to handle this
many circuit creation requests! Please consider using the
MaxAdvertisedBandwidth config option or choosing a more restricted
exit policy. [13867 similar message(s) suppressed in last 60 seconds]
Aug 29 18:56:40.000 [warn] eventdns: All nameservers have failed

[snipped similar "too slow to handle" messages]

Aug 29 19:05:19.000 [notice] eventdns: Nameserver 192.168.1.1:53 is
back up


My main question:  How do circuit creation requests on one's Tor relay
cause load on one's network infrastructure?  Is it DNS requests?  Is
it TCP connection state entries?  It's not bandwidth, we observed that
above, and my router can handle far faster pipes than the one it's on
currently.  The DNS failing is a sign that the router is under severe
stress.  Back in the 0.2.3.x days, I often had to reboot the *router*
after one of these storms, not just the Tor relay.

And again - do we really know what is causing this?  Something seems
seriously wrong with the kind of numbers I'm seeing coming in to a
node with MaxAdvertisedBandwidth 250KB.

I think a bug should be opened about this, if there isn't one already.

Regards,
- -Gordon M.
-----BEGIN PGP SIGNATURE-----

iQEcBAEBCgAGBQJSIAT1AAoJED/jpRoe7/ujuK4H/06MxbDHlN2uHjae6XurDib1
3yxXhHAUXC5pcP8smLQgqqtazTweeQDfIOT78QS9I0MB5z7ZnAYYsjs1/tJ1AKhb
GkHtYXnlaZCxuP/oHlZYVsEhKXGGRSrXQM+y9f4uoukCn7KyVlCPF9oz2wBtSLqE
qCENCZydn7nPUL6mRxveCoUvVXcGfBvm9uk17SmfuV2e6eDr5NMM4x2IxsZAYzLq
hfYOUs8xLMqldsFqIaIV5J8sKwurI040P+TpZNVe7anB1ZF7uNRPfiyGrG7/JgTq
aiGTyPArEdLnqYcRwGW+HbXBhQBjqF5yLt5Jj+kXXG5qBvaLQ3h/7IT7CJFr8GI=
=eaXx
-----END PGP SIGNATURE-----
_______________________________________________
tor-relays mailing list
tor-relays@xxxxxxxxxxxxxxxxxxxx
https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays