Hi Ibex There's some discussion about this issue on #tor-relays. First of all, I actually don't think there's any problem with your Exit node. IMO 1.5% is expected and the current threshold is just too low (or the timeout too low).
We're hosting some fairly high capacity exit nodes (around 100mbit/s each), generating about 100 DNS queries/sec in total. We're also seeing around 1.5% failed DNS queries. Here's what I think is going on: For some queries (1.5%?), the authoritative DNS servers for the requested domain are not responding. Recursive DNS resolvers are by default more patient than the Tor software. Eventually the recursive resolver will return a 'SERVFAIL' to Tor, but by then, Tor has already given up, and counts it as a timeout. One example of a domain that is currently (2021-11-08T23:40+01:00) failing to resolve because of its authoritative DNS servers being down is mzfgbh.com. Try running `dig +trace +additional mzfgbh.com` (for some reason, dig ignores the 'additional' section of one of the answers. Essentially the problem is that this query (and a few others) times out: `dig mzfgbh.com @ 1.1.1.20`). On a related note, when this metric was introduced, we were seeing around 5-6% failed queries. The recursive DNS resolver we were using was hosted on the same IP as a guard node. Apparently many authoritative DNS servers block traffic from all Tor relays! The most extreme example of this I found, is that the authoritative DNS servers for the entire .by ccTLD (Belarus) are blocking DNS requests from guard and exit nodes. This resulted in all <domain>.by queries timing out! By moving our recursive DNS resolver to an IP not used by any Tor relays, the DNS timeouts fraction reported by Tor dropped from 5-6% to 1.5%. The Tor relay guide should recommend running your recursive resolver (unbound) on a different IP than your exit: https://community.torproject.org/relay/setup/exit/ - Anders Trier Olesen On Sat, Nov 6, 2021 at 5:53 PM Intrepid Ibex via tor-relays < tor-relays@lists.torproject.org> wrote: > Hi everybody, > > I am new to tor (as server operator) and try to support the network by > operating an exit node. > > Machine is running Ubuntu 20.04 - Tor 0.4.6.8. > > nyx is giving me a notive every 10 minutes or so: [NOTICE] General > overload -> DNS timeouts (6) fraction 1.4742% is above threshold of 1.0000% > > DNS on this machine however works perfectly. I told my tor browser to use > my specific exit node, everything works fine. > > Node is running since 4 days now. Load is as expected. > > Thanks in advance for any help! > > Ibex > > > -- > Sent using MsgSafe.io > <https:/www.msgsafe.io/?utm_source=msgsafe&utm_medium=email&utm_campaign=freemailsignature>'s > Free Plan > Private, encrypted, online communication > For everyone. www.msgsafe.io > <https:/www.msgsafe.io/?utm_source=msgsafe&utm_medium=email&utm_campaign=freemailsignature> > _______________________________________________ > tor-relays mailing list > tor-relays@lists.torproject.org > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays >
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