tor-relays June 2022

tor-relays@lists.torproject.org

30 participants
27 discussions

How to reduce tor CPU load on a single bridge?
by David Fifield 19 Dec '22

19 Dec '22

The main Snowflake bridge (https://metrics.torproject.org/rs.html#details/5481936581E23D2D178105D44DB6…) is starting to become overloaded, because of a recent substantial increase in users. I think the host has sufficient CPU and memory headroom, and pluggable transport process (that receies WebSocket connections and forwards them to tor) is scaling across multiple cores. But the tor process is constantly using 100% of one CPU core, and I suspect that the tor process has become a bottleneck. Here are issues about a recent CPU upgrade on the bridge, and observations about the proportion of CPU used by different processes: https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowfl… https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowfl… I have the impression that tor cannot use more than one CPU core—is that correct? If so, what can be done to permit a bridge to scale beyond 1×100% CPU? We can fairly easily scale the Snowflake-specific components around the tor process, but ultimately, a tor client process expects to connect to a bridge having a certain fingerprint, and that is the part I don't know how to easily scale. * Surely it's not possible to run multiple instances of tor with the same fingerprint? Or is it? Does the answer change if all instances are on the same IP address? If the OR ports are never used? * OnionBalance does not help with this, correct? * Are there configuration options we could set to increase parallelism? * Is migrating to a host with better single-core performance the only immediate option for scaling the tor process? Separate from the topic of scaling a single bridge, here is a past issue with thoughts on scaling beyond one bridge. it looks as though there are not ways to do it that do not require changes to the way tor handles its Bridge lines. https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowfl… * Using multiple snowflake Bridge lines does not work well, despite that we could arrange to have the Snowflake proxy connect the user to the expected bridge, because tor will try to connect to all of them, not choose one at random. * Removing the fingerprint from the snowflake Bridge line in Tor Browser would permit the Snowflake proxies to round-robin clients over several bridges, but then the first hop would be unauthenticated (at the Tor layer). It would be nice if it were possible to specify a small set of permitted bridge fingerprints.

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relayor v22.0.0-rc is released
by nusenu 03 Dec '22

03 Dec '22

Hi, relayor v22.0.0-rc is released. relayor is an ansible role that helps you with running tor relays with minimal effort (automate everything). https://github.com/nusenu/ansible-relayor#main-benefits-for-a-tor-relay-ope… Changes since relayor v21.2.0-rc: * MetricsPort support improvements: * generate nginx reverse server config for remote prometheus scraping on the relay (we do not install nginx) * generate htpasswd file for HTTP basic auth of MetricsPort on the relay * debian/ubuntu: support new alpha repos (branch name is no longer included in the repo name). * FreeBSD 12.3 is supported kind regards, nusenu -- https://nusenu.github.io

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[New Initiative] Tor Weather: Improving the Tor Weather
by Sarthik Gupta 18 Aug '22

18 Aug '22

Hello everyone, As we all know, nodes are the building blocks of the tor-network. More often than not these nodes require some maintenance, which could be in the form of software upgrades, troubleshooting issues, rebooting the relays in case of failures, etc. As of today, if any relay disappears from the tor-network, no one will know. Tor-Weather aims at solving this by creating a notification service which relay operators can subscribe to in order to get various types of updates for their relays. The tor-weather service will offer a plethora of notifications options for the relays. These include, the node being down, running on EOL/Outdated version, losing a flag, ranking in top 20/50/100, etc. These notifications can be subscribed & customized by the relay operators to fit their needs using a web-frontend. Folks interested in the project can refer this <https://lists.torproject.org/pipermail/tor-dev/2022-May/014734.html> thread in the tor-dev mailing list for regular updates. Suggestions are always welcomed! Please reach out to us in irc (#tor-dev) for any ideas, questions, or suggestions you might have. Thanks, Sarthik Gupta

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We're trying out guard-n-primary-guards-to-use=2
by Roger Dingledine 11 Jul '22

11 Jul '22

Hi folks, As part of the hackweek projects ( https://gitlab.torproject.org/tpo/community/hackweek/ ), some of us are thinking about simple tweaks we can do to tune the network to better handle this month's traffic overload. The long term answer is to try out proposal 327: https://gitweb.torproject.org/torspec.git/tree/proposals/327-pow-over-intro… because we think a lot of the overload has to do with people sending way too many intro cells to some onion services, and giving the onion services ways to defend themselves is the only real answer. But while we're thinking about implementing that proposal, one of our earlier steps is to set the guard-n-primary-guards-to-use consensus parameter from 1 to 2. Now that it's taken effect (you can watch the votes at https://consensus-health.torproject.org/#consensusparams ), this change means that clients will now choose between two guard relays by default (rather than just one) when building circuits. This is potentially a big deal, since it puts us into a different point in the performance vs safety tradeoff space. Here is some reading for why we originally moved down to 1 guard by default: https://blog.torproject.org/improving-tors-anonymity-changing-guard-paramet… https://www-users.cse.umn.edu/~hoppernj/single_guard.pdf But on the theory that some guards are way overloaded right now and some aren't, giving clients two bites at the apple might make a dramatic improvement in terms of reliable and consistent performance. There is also some argument in favor of using two guards anyway. One reason (explained more in proposal 291) is that there are already some edge cases where clients use their second guard. And also, in the glorious future, we will want to be using multiple guards because we have switched to the multi-path Conflux design (proposal 329) -- though we're not there yet. So: I am giving you all here some early warning, in case you see anything odd on the network when we make this change. Let us know if you do. :) --Roger

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[Event] Tor relay operator meetup - June 25th @ 1900 UTC
by gus 27 Jun '22

27 Jun '22

Hello, The next Tor relay operator meetup will happen on Saturday, June 25 @ 1900 UTC. Where: BigBlueButton - https://tor.meet.coop/gus-og0-x74-dzn No need for a registration or anything else, just use the room-link above. We will open the room 10 minutes before so you can test your mic setup. Everyone is free to bring up additional questions or topics at the meeting itself. Please share with your friends, social media and other mailing lists! cheers, Gus -- The Tor Project Community Team Lead

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Relay "unmeasured" after update to 0.4.7.8
by Martin 27 Jun '22

27 Jun '22

Hi all! After updatering to the latest version, my relay consensus went down to 20 and was marked unmeasured. However it still serves a couple of thousand connections (capped at 10 MB/s) and all flags are still there, but when I try to use it to build a circuit manually it won't let me... Cheers

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Metrics shows my relay down. But it's not.
by Eddie 25 Jun '22

25 Jun '22

The metrics is showing one of my relays (40D13096BBD11AF198CE61DEE4EAECCE5472F2E7) as down for around the last 3 hours. Logging in to it, I see everything running normally. This server has also lost a bunch of flags for no apparent reason, so I'm not sure if they're connected. Cheers.

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FreeBSD 13.1: clock_gettime(CLOCK_MONOTONIC_FAST) ~ 50 % performance gain
by Andreas Kempe 22 Jun '22

22 Jun '22

Hello everyone, I was doing some profiling on my two relays running on FreeBSD 13.1 and noticed that they were spending a lot of time in clock_gettime() which prompted me to have a look at the implementation. Time implementation =================== The time implementation is abstracted in src/lib/time/compat_time.c where different mechanisms are used for different operating systems. On Linux CLOCK_MONOTONIC_COARSE is a clock that gives worse precision than CLOCK_MONOTONIC, but is faster and the abstraction layer checks for its presense and provides more performat less precise time where applicable. On FreeBSD, there is also a fast monotonic time source available called CLOCK_MONOTONIC_FAST. In the header file src/lib/time/compat_time.h, a comment references this clock, but it is not used. I thought it might be worth a shot seeing what difference it would make if I enable the use of CLOCK_MONOTONIC_FAST on FreeBSD and on the VM where I run my two FreeBSD relays, the difference was stunning. I made did a quick patch simply replacing CLOCK_MONOTONIC_COARSE with CLOCK_MONOTONIC_FAST, see patches attached, compiled and tested. Tracing system calls to make sure the correct call was being used, which it was. Results ======= This lead to reducing the CPU usage of the patched relay by about 50 % compared to the unpatched relay. I was a bit shocked so I wrote a small benchmark program and ran it on my VM giving the following results: CLOCK_MONOTONIC: 4.776675 s CLOCK_MONOTONIC_FAST: 0.260002 s Showing that on my VM the performance of CLOCK_MONOTONIC_FAST is about 20 times better than CLOCK_MONOTONIC. I have tested on a few different systems and I think that the performance increase of CLOCK_MONOTONIC_FAST is thanks to commit 60b0ad10dd0fc7ff6892ecc7ba3458482fcc064c - "vdso: lower precision of vdso implementation of CLOCK_MONOTONIC_FAST and CLOCK_UPTIME_FAST" that was cherry-picked to 13.1. Try it yourself and report your results ======================================= If you want to benchmark your server to see whether switching clock could benefit you, you can compile and run my attached test program by doing user>clang -o bench.c -o bench user>./bench In case the program terminates too quickly or slowly for your liking, adjust const unsigned long iterations = 1000000; up or down to change the execution time. My supplied patches appear to work fine on my system, but aren't really upstream appropriate since a solution that works for both FreeBSD and Linux is needed. If you want to test them and you're building Tor from the ports tree, drop them in /usr/ports/security/tor/files and build and install. I'm very interested in seeing some performance data from other people to see whether I think it worth either pestering some Tor devs to have a look at this or putting in some effort myself to write an upstreamable patch. Thank you for reading! Cordially, Andreas Kempe

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From [tor-announce] Tor stable release 0.4.7.8 - Security Fix
by Felix 20 Jun '22

20 Jun '22

> We have released tor 0.4.7.8 earlier today, a new stable version for > the 0.4.7.x series containing an important High severity security > fix. The affected tor are only those of the 0.4.7.x series as in from > tor-0.4.7.1-alpha to tor-0.4.7.7. Jun 18 10:08:46.000 [notice] This version of Tor (0.4.7.8) is newer than any recommended version, according to the directory authorities. -- Cheers Felix

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EXPKEYSIG when running 'apt update'
by Imre Jonk 17 Jun '22

17 Jun '22

Hi tor-relays, I'm getting this error when running 'apt update': Err:4 https://deb.torproject.org/torproject.org bullseye InRelease The following signatures were invalid: EXPKEYSIG 74A941BA219EC810 deb.torproject.org archive signing key The signing key in /etc/apt/trusted.gpg.d/deb.torproject.org-keyring.gpg does not appear to be expired, so I guess some repository metadata signature has expired. Does anyone else encounter this issue? Thanks, Imre

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tor-relays June 2022