[tor-relays] Recent wave of abuse on Tor guards

[fcornu@xxxxxxxxxxxxx]

Hi

I'm the happy maintainer of wardsback : 
B143D439B72D239A419F8DCE07B8A8EB1B486FA7

As many of us have noticed, many guard nodes are beeing abused by 
extremely high numbers of connection attempts.
Thanks to some of you guys, I manged to put some mitigation in place [0] 
and I assume many of us did as well.

I now sit back with questions and concerns arising :

 1) Why didn't we see this abuse wave coming ? We kept replying to 
reporters of the dreaded "Failing because we have XXX connections 
already. Please read doc/TUNING for guidance" about how they could amend 
their config to accept more connections. Although the 'global scale' of 
those events should have been detected, without most of use assuming it 
was due to nodes' bad config.

 2) We can see on Metrics [1] that guards count is dropping rapidly for 
a couple weeks now. Presumably because many guard maintainers gave up on 
restarting their crushed node. (I never will. Even though my Metrics 
graph shows I've also been in trouble)

 3) What could we do to better detect those 'attacks' and spread the 
word to fellow maintainers about how to mitigate / correct the situation 
?

I must admit I don't have a valuable clue about how things can 
technically be improved, but I humbly wanted to share a few thought 
here.

Peace

[0] : 
https://lists.torproject.org/pipermail/tor-relays/2017-December/013846.html
[1] : 
https://metrics.torproject.org/relayflags.html?start=2017-09-21&end=2017-12-20&flag=Guard

--
Frédéric CORNU
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