https://www.whonix.org/wiki/Dev/Control_Port_Filter_Proxy
says:
onion-grater listens on 0.0.0.0 port 9052, filters (white list) incoming control port messages and forwards them to the real Tor Control Port listening in 127.0.0.1:9051
Looking at the netstat output suggests that the above documentation is no longer up to date and needs an update.
after the latest edit:
https://www.whonix.org/w/index.php?title=Dev%2FControl_Port_Filter_Proxy&type=revision&diff=39840&oldid=39799
the documentation says:
onion-grater listens on Whonix internal network interface, port 9052, filters (white list) incoming control port messages and forwards them to the real Tor Control Port listening in 127.0.0.1:9051.
which is still not correct?
onion-grater port: 9052 vs. 9051
and
tor control port: 127.0.0.1:9051 vs. control socket