[tor-bugs] #32938 [Circumvention/Snowflake]: Have a way to test throughput of snowflake proxy

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#32938: Have a way to test throughput of snowflake proxy
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 Reporter:  cohosh                               |          Owner:  cohosh
     Type:  enhancement                          |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:
Component:  Circumvention/Snowflake              |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  snowflake-webextension, ux-team,     |  Actual Points:  3
  anti-censorship-roadmap-2020Q1                 |
Parent ID:  #31109                               |         Points:  5
 Reviewer:                                       |        Sponsor:
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Comment (by cohosh):

 I've been reflecting on this ticket a bit as I continue implementing it.
 Right now this seems to be taking the form of a usability improvement that
 may eventually lead to performance improvements. I'm wondering how useful
 it will be in the long run. Some insights:
 - This feature does nothing to prevent an adversary from swamping the
 broker with malicious proxies. Having the broker tell a proxy how often to
 poll is an entirely trust-based mechanic to improve network health.
 Similarly, this test makes it easy for a proxy to distinguish between the
 throughput test and actual clients. They can perform well for the test and
 then poorly for client traffic if they want to cause trouble.
  Maybe this is okay, and this is just a tool for users to see if their
 proxy works (similar to how bridgestrap was designed to be used for
 #31874).

 - If we want to make this throughput test more rigorous against
 adversarial proxies, we're going to have to do things like introduce
 persistent identifiers for snowflake proxies (#29260), and make some
 modifications to the broker to track proxy performance and periodically
 scan proxies for malicious behaviour. Doing so makes snowflake proxies
 more and more similar to Tor relays and I'm not sure this fits the model
 we have in mind for proxies to be simple, lightweight, and ephemeral.

 - Ultimately, this may be more trouble than it's worth if it means we have
 to maintain a separate deployed probe point. Rolling this functionality
 into the broker would be better for this reason since we need a broker
 deployment already for the whole system to work.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32938#comment:11>
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