Virtual IP changes: run a custom script when a change is detected

[nqb]

Is your feature request related to a problem? Please describe.
When you are in a cloud environment, assigning a dynamic virtual IP address using VRRP is not always supported as-is. Manual actions can be necessary.

In order to perform these actions, it would be nice to let users execute a script when a VRRP change occured.

We already have a script called pfupdate executed through keepalived configuration but you have to patch that script to perform your actions.

Describe the solution you'd like
pfupdate will run a custom script if present. We can pass $mode as an argument and also virtual IP address to assign.

[nqb]

Thing to have in mind: when you restart keepalived to apply some changes like a routed network, it triggers a VRRP change.