Investigate Snowflake blocking in China
We've been receiving updates from amiableclarity2011 about snowflake issues in China for a while now (they first reported the blocking of our default STUN servers a while back).
Recently they have not been able to bootstrap a connection at all. I wrote a script for monitoring snowflake health (legacy/trac#32545 (moved)) to check to see if this is due to the faulty snowflake problem we've been having, and ran these tests from a VPS in China and a VPS in North America. I was expecting to see about half of the snowflake connection attempts to succeed and set a 3 minute time out on circuit construction. However, what I saw was a 90% success rate from North America and a 0% success rate in China.
This almost certainly due to blocking, and as ambleclarity recently confirmed in legacy/trac#32597 (moved), not due to the blocking of STUN servers.