[bug] Defining OpenVPN Server in a template complains about validation and does not allow saving

[nemesifier]

Steps:

• create a new template
• add openvpn conf
• select server routed
• prepare a sample config
• try saving

Expected result: can save.

Actual result: validation error doesn't allow saving.

[kosli]

Would be great if this could be fixed for the next release so that I could deploy routed openvpn servers straight via the UI. Thanks.

[anshhh713]

I tested this with a completely fresh setup:

• Forked the repository on a new account

• Fresh clone

• docker compose build

• docker compose up

• No existing data (new DB / volumes)

Following the same steps described in this issue, I was not able to reproduce the validation error — saving the template succeeded.

However, in a previous local setup (older fork / existing data), performing similar steps resulted in the generic validation error (“Please correct the error below”), even when following the same flow.

This suggests the issue may be state-dependent (e.g. related to existing OpenVPN configs, templates, or prior data), rather than strictly tied to the creation order.

I no longer have screenshots from the previous setup, but I can try to reproduce it again by reintroducing existing data if that would help.

Additional observation:
In the previous setup, saving the template initially worked without any issues.
Later, without changing the steps, saving started failing with the same generic validation error.
This occurred irrespective of creation order or server mode (bridged / routed / manual), and once the error started occurring, it persisted for subsequent attempts in that environment.

Further clarification / precise reproduction:

• Adding a VPN configuration to a template (either from within the template or created outside and then added) saves successfully for all modes (bridged / routed / manual).

• Before saving the template, the VPN configuration cannot be edited and defaults to client mode.

• After saving the template, editing the VPN configuration and changing the mode shows different behavior:

• Changing client → bridged or client → routed triggers the validation error.

• Keeping client, or changing client → manual, saves successfully.

This indicates the validation error occurs specifically when switching a template VPN configuration from client mode to server modes on edit, rather than during initial creation.

Additional detail:

• Routed and bridged modes require server network values (e.g. 10.8.0.0 255.255.255.0).
  Even when these fields are filled in the UI after switching from client mode, saving still fails, suggesting the values may not be included in the submitted configuration when editing a template VPN config.

[Viscous106]

Hi @nemesifier,

I’ve successfully reproduced this issue locally and would like to work on it.

Reproduction steps:

1. Create a new Template (Type: Generic, Backend: OpenWRT)
2. Add an OpenVPN configuration via the menu
3. Switch Mode to “Server (routed)”
4. Save → a generic “Please correct all validation errors below” message appears, but no field is highlighted
5. 

Hypothesis:
It looks like a ValidationError is raised during the model’s clean() phase, but the error key doesn’t correspond to any visible field in the admin form. As a result, Django shows the generic error banner without attaching the message to a specific field or non_field_errors.

Proposed approach:

• Debug the clean() logic in the relevant VPN/Template models to identify the failing validation
• Ensure the ValidationError is either:
  • attached to a concrete, visible field, or
  • raised as a non-field error so it is rendered explicitly at the top of the form
• Add/adjust tests if needed to prevent regressions

If this approach sounds good to you, I’ll proceed with the fix.
Thanks!