Feature request: support docker execution with an IPv6 network

[zalegrala]

With the following /etc/docker/daemon.json file, I'm able to get the output below indicating that an IPv6 address is available.

/etc/docker/daemon.json

{
  "ipv6": true,
  "fixed-cidr-v6": "2001:db8:1::/64"
}

❯ docker run -it archlinux:latest ip addr | grep inet
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
    inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0
    inet6 2001:db8:1::242:ac11:2/64 scope global nodad 
    inet6 fe80::42:acff:fe11:2/64 scope link tentative 

However, if I run a test which implements this project, executing ip addr in the container does not yield an IPv6 address.

❯ docker exec -it ffb07eaee33b ip addr | grep inet
    inet 127.0.0.1/8 scope host lo
    inet 172.23.0.5/16 brd 172.23.255.255 scope global eth0

Perhaps there is a flag we can add to indicate that docker should execute with an IPv6 address.

[zalegrala]

Also have no fear, alpine is also reporting IPv6 addresses.

❯ docker run -it alpine:latest ip addr | grep inet
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
    inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0
    inet6 2001:db8:1::242:ac11:2/64 scope global flags 02 
    inet6 fe80::42:acff:fe11:2/64 scope link tentative