What is the point of the docker-proxy process? Why is a userspace tcp proxy needed?
Solution 1:
Apparently there are some edge cases without a better workaround (for now):
- localhost<->localhost routing
- docker instance calling into itself via its published port
- and possibly more
https://github.com/docker/docker/issues/8356
UPDATE: Since 1.7.0 (2015-06-16) the userland proxy can be disabled in favor of hairpin NAT using the daemon’s --userland-proxy=false flag.