I’ve done so much experimentation with GFW pre pandemic while staying in China for extended period of times. I was always amazed at how quickly they would catch up on my shadowsocks, random ssh tunnels…etc. 48 hours top before I had to rotate IPs. This report seems to indicate this is now instant?
Fwiw My most reliable trick ended up piggie-backing off of a physical line going into Hong Kong from Shenzhen, and when roaming around China, using a vpn to get to that shenzhen gateway. As far as I can recall, that always worked. This led me to believe that most of the vpn traffic analysis (and blocking)was done at the edge of the GFW and not inside of it. Again, this could be outdated by now.
I tried to setup a shadowsocks server to bypass the GFW about 2 weeks ago. Server was hosted on my local network in Australia (with public IP), client was connecting from China (using the server IP).
It was blocked immediately and the client could not connect. I had several unknown IPs try to connect prior to the attempted connection.
I was stunned at how water tight the GFW is, it's really unfortunate as I would love to work/travel through China but cannot due to needing an active internet connection.