Ubuntu – vpnc works but network-manager-vpnc fails


I am trying to connect to a vpnc vpn.

I first created a conf file /etc/vpnc/clientvpn.conf looking like this:

## generated by pcf2vpnc
IPSec ID mygroupid
IPSec gateway some.ip.add.ress
IPSec secret mygrouppassword

Xauth username myusername
Xauth password myuserpassword
IKE Authmode psk

and using sudo vpnc clientvpn works fine.

Now I want to use network-manager vpnc plugin.
I created a new vpn setting, and set the different values:

nm vpnc settings

I left the advanced settings to their default values. Trying to connect from NetworkManager fails, with the following logs:

NetworkManager[1155]: <info> Starting VPN service 'vpnc'...
NetworkManager[1155]: <info> VPN service 'vpnc' started (org.freedesktop.NetworkManager.vpnc), PID 5888
NetworkManager[1155]: <info> VPN service 'vpnc' appeared; activating connections
NetworkManager[1155]: <info> VPN plugin state changed: starting (3)
NetworkManager[1155]: <info> VPN connection 'clientvpn' (Connect) reply received.
NetworkManager[1155]:    SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/tun0, iface: tun0)
NetworkManager[1155]:    SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/tun0, iface: tun0): no ifupdown configuration found.
NetworkManager[1155]: <warn> /sys/devices/virtual/net/tun0: couldn't determine device driver; ignoring...
NetworkManager[1155]:    SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/tun0, iface: tun0)
NetworkManager[1155]: <warn> VPN plugin failed: 1
NetworkManager[1155]: <info> VPN plugin state changed: stopped (6)
NetworkManager[1155]: <info> VPN plugin state change reason: 0
NetworkManager[1155]: <info> Policy set 'Connexion filaire 1' (eth0) as default for IPv4 routing and DNS.
NetworkManager[1155]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.

I am not sure if /sys/devices/virtual/net/tun0: couldn't determine device driver; ignoring... is a meaningful message.

Why does the nm plugin fail, while vpnc works just fine ?

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