feat: Reduce kea decline-probation-period value

[stoo-davies]

Is this a new feature, an enhancement, or a change to existing functionality?

Change

How would you describe the priority of this feature request

Low (would be nice)

Please provide a clear description of problem this feature solves

We recently had a DPU which was unable to get an IP address, we could see on the DPU console that it was going through the sequence DISCOVER/OFFER/REQUEST/NAK.

Looking at the nico side we saw that Kea was getting the correct IP from the callout, but was then sending a NAK.

Eventually we traced it back to the client sending back a DECLINE for an earlier request, causing kea to mark that IP address as bad for a whole day....

2026-06-10 18:57:54.603 INFO  [kea-dhcp4.leases/8.135561560011264] DHCP4_DECLINE_LEASE Received DHCPDECLINE for addr 10.1.2.3 from client [hwtype=1 xx:xx:xx:xx:xx:xx], cid=[no info], tid=0xd504e47. The lease will be unavailable for 86400 seconds.

Unfortunately I don't know for certain why the original DECLINE was sent. Presumably the client had detected that the IP address was already in use, but that was not the situation later on. Maybe 5 or 15 minutes would be a better timeout than a whole day?

Feature Description

Faster cleanup of blocked IP addresses than a day.

Describe your ideal solution

5-15 minute timer.

Describe any alternatives you have considered

No response

Additional context

No response

Code of Conduct

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