I'm a bit confused here, there's not much information about using mongodb with ipv6 the only one I read in the doc seems to be wrong, here is what the doc (https://docs.mongodb.com/manual/reference/configuration-options/) says:

net.ipv6
Type: boolean

Default: False

Removed in version 3.0.

Enable or disable IPv6 support and allows mongos or mongod to connect to the MongoDB instance using an IPv6 network. Prior to MongoDB 3.0, you had to specify net.ipv6 to use IPv6. In MongoDB 3.0 and later, IPv6 is always enabled.

So as I'm using 3.2.9, I understand this option no longer exists and ipv6 is enabled by default. But ipv6 is not working for me, and when I tried setting this options after hours of debugging, I actually found it to be working ☹:

$ mongod --version
db version v3.2.9
git version: 22ec9e93b40c85fc7cae7d56e7d6a02fd811088c
OpenSSL version: OpenSSL 1.0.2g-fips  1 Mar 2016
allocator: tcmalloc
modules: none
build environment:
    distmod: ubuntu1604
    distarch: x86_64
    target_arch: x86_64

without the option

$ tail -3 /etc/mongod.conf
net:
  port: 27017

$ sudo service mongodb restart
$ netstat -an | grep tcp | grep 27017
tcp        0      0 0.0.0.0:27017           0.0.0.0:*               LISTEN
$ nc -vz 127.0.0.1 27017
Connection to 127.0.0.1 27017 port [tcp/*] succeeded!
$ nc -vz ::1 27017
nc: connect to ::1 port 27017 (tcp) failed: Connection refused

with the option

$ tail -4 /etc/mongod.conf
net:
  port: 27017
  ipv6: true

$ sudo service mongodb restart
$ netstat -an | grep tcp | grep 27017
tcp        0      0 0.0.0.0:27017           0.0.0.0:*               LISTEN
tcp6       0      0 :::27017                :::*                    LISTEN
$ nc -vz 127.0.0.1 27017
Connection to 127.0.0.1 27017 port [tcp/*] succeeded!
$ nc -vz ::1 27017
Connection to ::1 27017 port [tcp/*] succeeded!

So what's the problem, did I misunderstood something ? is it a bug ? is the doc wrong or the code wrong ? I'll of course use this option in the meanwhile but I would like to save the next persons to have this issue a few hours of their life

And I would also make sure that If I start using this option it won't break my config at some upgrade once it's removed for real.