No bytecount updates in management interface

[maddsua]

Describe the bug
When this topology is configured DCO is enabled (which happened automatically on package install), no traffic would be reported to the management interface, except for around 2Kb of handshake data.

No amount of waiting results in getting any more data reported.

Enabling/disabling DCO doesn't seem to change anything.

To Reproduce

1. Set the topology config option to subnet Install the openvpn package using apt
2. Connect to a management interface with telnet/NC
3. Set bytecount 1
4. Observe the absence of traffic reports

Expected behavior
Traffic should be reported normally

Version information (please complete the following information):

• OS: Ubuntu 24.04.2 LTS
• OpenVPN version: 2.6.14

Additional context
The issue was updated as it seems that the behavior is indeed triggered by DCO. This flew under the radar initially as the system wasn't rebooted after uninstalling the DCO module

UPD: Weirdly enough, the openvpn-dco-dkms package is marked as suggested, and yet it was installed automatically

[cron2]

I assume this is on the server side? (Counters for client side and p2mp server side follow very different code paths inside OpenVPN).

I'm not sure if 2.6 is expected to have full counter support with DCO on both client and server side (would need to look into the source and test ) - but what I can say is that we've done quite a bit of work to make sure everything works correctly in 2.7 + DCO on Linux and Windows. There is a 2.7_beta3 out today which you could test, or wait for a few more weeks for the 2.7.0 release (estimated "in November").