IPV6-Problems: [registerService] Failed to contact master at [server:11311]. Retrying...

edit

Heyho, somehow using

export ROS_IPV6=on

in Docker doesn't work and gives the error message in the title: [registerService] Failed to contact master at [server:11311]. Retrying...

ROS-Version: Melodic Host System: Ubuntu 20.04.3 LTS Docker-Version: 20.10.12

Steps to reproduce:

docker pull osrf/ros:melodic-desktop-full
docker run -it --rm --net=host osrf/ros:melodic-desktop-full /bin/bash
export ROS_IPV6=on
roscore

Output:

... logging to /root/.ros/log/2bae647e-7251-11ec-85b6-b42e99464746/roslaunch-server-35.log
Checking log directory for disk usage. This may take a while.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://server:46123/
ros_comm version 1.14.11


SUMMARY
========

PARAMETERS
 * /rosdistro: melodic
 * /rosversion: 1.14.11

NODES

auto-starting new master
process[master]: started with pid [45]
ROS_MASTER_URI=http://server:11311/

setting /run_id to 2bae647e-7251-11ec-85b6-b42e99464746
process[rosout-1]: started with pid [56]
started core service [/rosout]
[ERROR] [1641845350.101209283]: [registerService] Failed to contact master at [server:11311].  Retrying...

Any pointers?