During DISCOVER, each address which hasn’t been offered to the client before
OR has has passed the expired, declined and released address timers, dhcpsd
will send an ICMP ECHO to the address.
If an ICMP ECHOREPLY is received from the address with the same ID as the ECHO
within 3 seconds then the address is marked as DECLINED for 30 seconds and dhcpsd
will try another address with the same rules until we find a free address
to make an OFFER with.
Until this process completes, any futher DISCOVER messages from the client are discarded.
It is NOT recommended to use this plugin if your DHCP clients use
Duplicate Address Discovery as recommended in RFC 2131 as they can do a better job of
detecting an in-use address and sending a DECLINE message.