Tom Gundersen authored May 21, 2019 and Beniamino Galvani committed Jul 05, 2019

The DHCP client is not meant to use the assigned address before DAD
has completed successfully, if enabled. And if DAD fails, the server
should be notified with a DECLINE, in order to potentially blacklist
the address.

Currently, none of the clients support this, but add the required
callbacks, and allow clients to opt in if they want.