[tor-bugs] #24010 [Core Tor/Torflow]: Make bandwidth authorities use DNS, not IP addresses

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#24010: Make bandwidth authorities use DNS, not IP addresses
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 Reporter:  teor              |          Owner:  aagbsn
     Type:  defect            |         Status:  new
 Priority:  High              |      Milestone:
Component:  Core Tor/Torflow  |        Version:
 Severity:  Normal            |     Resolution:
 Keywords:                    |  Actual Points:
Parent ID:  #21394            |         Points:  1
 Reviewer:                    |        Sponsor:
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Comment (by micah):

 This strikes me as adding a potentially fragile layer to an already
 teetering edifice.

 The domain name that I would have used for this was recently 'blocked' by
 1/3rd of all of home cable users in Chile because they made a mistake in
 attributing wannacry as coming from our exit node, or maybe even directory
 authority. It took months to track this down, along with in-person
 meetings with the ISP.

 DNS is also frequently the easiest thing for overzealous countries to
 block. If we depend on it for bandwidth scanning, I feel like we are
 adding a layer to the system that enables the entire stack to easily fall
 down when pushed at the top. Don't like tor running in your country? Just
 block these domain names from resolving and it will cause all relays in
 your country to get penalized by tor's bandwidth scanners so much that
 they are useless. If we were to do this, then I would say that bandwidth
 scanner web servers should be reached over different domain names, so that
 if one is blocked, the other is not also impacted.

 DNS can also be a bit funny, caching and inability to look up certain
 information, but no problems with other information. Having a server
 lookup one hostname every pass of the bandwidth scanner is likely just
 going to result in testing that the DNS can resolve once properly, and
 then cache that result for an unpredictable amount of time (depending on
 the DNS SOA record for the domain in question, the local resolver settings
 and the leaf resovlers up).

 I get the point of doing this, but I am not convinced that this should be
 the role of bandwidth scanners. Bandwidth scanners should be simply
 testing the speed of the network, and nothing else. Its already overly
 complicated, even for that one task. I think DNS reachability tests are
 important, and the problem does need to be fixed, but I wonder if this
 should be done some other way. Perhaps in the client itself? I am unsure.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24010#comment:5>
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