VPN: OpenVPN: Instances - improve keepalive validation, mentioned in https://github.com/opnsense/core/pull/10174

(cherry picked from commit 43dc040cfb)

src/opnsense/mvc/app/models/OPNsense/OpenVPN/OpenVPN.php

@@ -189,6 +189,11 @@ class OpenVPN extends BaseModel
                     gettext('Timeout must be at least twice the interval value.'),
                     $key . ".keepalive_timeout"
                 ));
+            } elseif ($instance->keepalive_interval->isEmpty() xor $instance->keepalive_timeout->isEmpty()) {
+                $messages->appendMessage(new Message(
+                    gettext('To configure keepalive, both interval and timout need to be specified.'),
+                    $key . ".keepalive_timeout"
+                ));
             }
 
             if ($instance->dev_type == 'ovpn' && strpos($instance->proto, 'udp') === false) {

src/opnsense/mvc/app/models/OPNsense/OpenVPN/OpenVPN.xml

@@ -359,7 +359,7 @@
                     <MinimumValue>0</MinimumValue>
                 </keepalive_interval>
                 <keepalive_timeout type="IntegerField">
-                    <MinimumValue>0</MinimumValue>
+                    <MinimumValue>1</MinimumValue>
                 </keepalive_timeout>
                 <reneg-sec type="IntegerField">
                     <MinimumValue>0</MinimumValue>