Kea does not send a subnet mask in its inform response when requested by a client that isn't requesting an address allocation

I am reporting this bug here, because people from pfSense told me, that this is an upstream (kea) bug (pfsense entry: https://redmine.pfsense.org/issues/15466#change-73231)

my bug:

I am using a mac with macos 14.4.1 and pfsense 2.7.2.

When using DHCP on my mac, everything works fine. I do get the correct settings (IP, subnet, router, dns, ...). When I switch to "Using DHCP with Manual Address", everything works fine as well except of the subnet mask. It should be 255.255.255.0, but instead it is 255.255.255.255.

This issue only exists with KEA DHCP server, not with ISC DHCP server. As soon as I switch back to ISC DHCP without touching any configuration, all is fine again.

Response from pfsense was:

As far as I can see this may be a bug in Kea itself you may need to report upstream. The configuration appears to be correct. The client requests the subnet mask attribute but Kea does not send it in the response message. The client then assumes the wrong mask because it didn't get the information it requested.

Honestly, however, that client setting is problematic in general. If you want static assignment, create a static mapping in the Kea GUI, do not hardcode the address on a client.