[tor-bugs] #32657 [Circumvention/Snowflake]: Investigate Snowflake blocking in China

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#32657: Investigate Snowflake blocking in China
-------------------------------------+---------------------------
 Reporter:  cohosh                   |          Owner:  cohosh
     Type:  defect                   |         Status:  assigned
 Priority:  High                     |      Milestone:
Component:  Circumvention/Snowflake  |        Version:
 Severity:  Normal                   |     Resolution:
 Keywords:  blocking, china          |  Actual Points:
Parent ID:                           |         Points:
 Reviewer:                           |        Sponsor:  Sponsor28
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Comment (by cohosh):

 Even though all the file downloads failed, there is still some data
 getting through (at least for a while). I took a look at the logs and
 noticed some Tor connections through snowflake are fully bootstrapping
 from the VPS:

 {{{
 [1] "Number of failed downloads: 100"
 [1] "Average throughput (KB/s): NaN"
 [1] "Standard deviation: NA"
 [1] "Number of failed snowflakes: 42"
 [1] "Number of full bootstraps: 49"
 [1] "Average bootstrap progress: 56.95"
 }}}

 If a snowflake doesn't bootstrap past 10% I counted it as failed. It looks
 like about half of boostraps succeeded. This is much lower than the > 90%
 success rate we get from a VPS in North America, and the fact that
 '''all''' file downloads fail is also concerning. These connections are
 over UDP, so they can't be blocked by sending a RST packet. It's possible
 that the GFW is more actively monitoring and blocking snowflake IP
 addresses, or that there is some forced packet loss happening that
 snowflake can't handle well.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32657#comment:1>
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