[Dnsmasq-discuss] [PATCH] Nack requests for unknown leases.

[Alin Năstac]

On Sun, Apr 23, 2017 at 5:46 PM, Simon Kelley <simon at thekelleys.org.uk> wrote:
> On 20/04/17 10:34, Alin Nastac wrote:
>> Hosts that migrate from one network to another could request their
>> old IP address which might be already in use by another statically
>> configured host. Currently non-authoritative dnsmasq servers will
>> ignore such requests, but ISC DHCP client will send discovery packets
>> next carrying the same requested IP address and dnsmasq will end up
>> allocating a new lease for it without checking first if is already
>> used by another host.
>
>
> When the client sends the discovery packet, dnsmasq will notice that the
> requested address is in use by another client, and offer a different
> address instead.

You did not understood the scenario. The host that already use the
requested IP address is statically configured to use it (in other
words dnsmasq does not have a lease for the given IP address).

While at it, you might consider fixing the scenario in which a client
fills a DHCP discovery message with an option-50 containing an IP
address that is already used by another statically configured host.