openvpn.conf working on the CLI and with systemd but not with NM: wrong IPv6 setting when configuring the tun interface?

[Samuel Le Thiec <sltrash posteo net>]

Note: sorry for the potential duplicate email, I sent it before & after having registered to the list!

Hello all,

I have a working openvpn config (see below) which I can't get to fully work with Network

Manager: the private IPv6 network is not accessible when connecting to the VPN with NM(*).

Here is what I get for tun0 when connecting with NM:

--------

$ ip a l tun0

17: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN

group default qlen 500

    link/none

    inet 10.66.6.4/24 brd 10.66.6.255 scope global noprefixroute tun0

       valid_lft forever preferred_lft forever

    inet6 2001:bc8:3d1d:1337::1002 peer 2001:bc8:3d1d:1337::1/64 scope global

noprefixroute

       valid_lft forever preferred_lft forever

--------

When connecting with systemd or via the command line (sudo openvpn --config vpn.conf) :

--------

$ ip a l tun0                                                                           

14: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN

group default qlen 500

    link/none                                                                           

    inet 10.66.6.4/24 scope global tun0                                                 

       valid_lft forever preferred_lft forever                                          

    inet6 2001:bc8:3d1d:1337::1002/64 scope global

       valid_lft forever preferred_lft forever

    inet6 fe80::24b7:bb72:a319:252d/64 scope link stable-privacy

       valid_lft forever preferred_lft forever

--------

→ Note the scope global inet6 differences above: peer vs subnet

(*) In order to avoid having all my trafic routed through the vpn, I did check "Use this

connection only for resources on its network" for IPv4 & IPv6.

Is there a way to make Network Manager behave like openvpn --config vpn.conf?

Here is additionnal informations:

--------

$ nmcli device show tun0

GENERAL.DEVICE:                         tun0

GENERAL.TYPE:                           tun

GENERAL.HWADDR:                         (unknown)

GENERAL.MTU:                            1500

GENERAL.STATE:                          100 (connected (externally))

GENERAL.CONNECTION:                     tun0

GENERAL.CON-PATH:                     

/org/freedesktop/NetworkManager/ActiveConnection/27

IP4.ADDRESS[1]:                         10.66.6.4/24

IP4.GATEWAY:                            --

IP4.ROUTE[1]:                           dst = 10.66.6.0/24, nh = 0.0.0.0, mt = 50

IP6.ADDRESS[1]:                         2001:bc8:3d1d:1337::1002/64

IP6.GATEWAY:                            --

IP6.ROUTE[1]:                           dst = 2001:bc8:3d1d:1337::1/128, nh = ::, mt = 256

IP6.ROUTE[2]:                           dst = 2001:bc8:3d1d:1337::1002/128, nh = ::, mt =

50

IP6.ROUTE[3]:                           dst = 2001:bc8:3d1d:1337::1/128, nh = ::, mt = 50

--------

And the openvpn client config I imported from NM (minus the certs&keys):

   | client

   | dev tun

   | # try standard port first

   | remote hub.nsoc.fr

   | remote hub.nsoc.fr 53

   | ping 25

   | ping-restart 120

   | persist-key

   | persist-tun

   | tls-version-min 1.3

   | remote-cert-tls server

   | mute-replay-warnings

   |

   | askpass

   | verb 3

   |

   | <ca></ca>

   | <cert></cert>

   | <key></key>

   | <tls-crypt-v2></tls-crypt-v2>

Thank you in advance!

Samuel