Figure out why docker maps external incoming IPs to a single local address

[cgorenflo]

Tendermint does an IP duplication check as a DOS prevention measure. For some reason, when running a network inside docker containers on multiple hosts, incoming connections are mapped to the same IP and therefore rejected. For now we solved it by setting the allow_duplicate_ips flag to true, but this needs to be solved properly before going live.

[sergeynog]

seems like a known behavior in docker. perhaps setting net interface to host and leaving the allow_duplicate_ips flag to false is all we need to do. moby/libnetwork#1994

[cgorenflo]

but then we can only run docker containers on linux

[sergeynog]

not sure. maybe it works on a mac by now? should try.

[cgorenflo]

https://deavid.wordpress.com/tag/userland-proxy/
This seems to be the fix:
In /etc/docker/daemon.json add:

{
     "userland-proxy": false
}

Then, restart Docker:
sudo service docker restart