Test Baidu reachability from exit nodes.
This bug describes a test to attempt to establish whether China is blocking our exit nodes simplex (incoming traffic to the node receives injected TCP reset packets) or duplex (all traffic to the node is blocked, in or out). Knowing this would be useful, because it will affect our bridge strategy -- if a bridge is blocked duplex and it knows it (by conducting a similar test), it could mark itself as blocked and be removed from the bridgedb.
The test consists of:
- from each exit relay:
- try to access a website in China
- a duplex-blocked node will fail
- a simplex-blocked node will succeed
The deliverable from the test should be a count of exit nodes that are blocked simplex vs. duplex.
Two possible methods are .exit notation or a SoaT test. SoaT is preferred.