Add new "Ignore client identifiers" DHCP feature

Exposes the underlying dhcpd configuration option "ignore-client-uids"
in the pfSense "Services / DHCP Server" GUI by adding an "Ignore client
identifiers" checkbox.

As of ISC dhcpd version 4.3.0+, there is a new configuration statement
available, "ignore-client-uids".  According to the ISC's documentation,
"If the 'ignore-client-uids' statement is present and has a value of
'true' or 'on', the UID for clients will not be recorded."

While this behavior does not strictly adhere to the DHCP specification,
it can be very useful in environments where devices on the network
dual boot or PXE boot.  Normally, if the network stacks in a single
device's different operating systems (including PXE firmware) make DHCP
requests with differing client identifiers, the server will treat each
request with a unique identifier as having come from a unique client,
even when they come from the same device.  Thus, different operating
systems on the same device and NIC might hold different leases with
different IP addresses.

Once activated, the "ignore-client-uids" option tells the DHCP server
not to record client identifiers in new DHCP leases, which forces the
server to fall back on hardware (MAC) addresses to uniquely identify
clients.  Now different operating systems on the same device and NIC
will hold the same lease (based on MAC address), which should keep
a device's IP address consistent regardless of its currently running
operating system.

Same as with most other general and pool-specific DHCP server options
in pfSense, note that turning on this option only affects new leases.
Any leases that existed prior to enabling this option will still
contain their respective client identifiers.  Manually deleting older
leases or flushing the entire lease table can expedite a full
migration to the new server behavior, if desired.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/etc/inc/services.inc b/src/etc/inc/services.inc
index cfda822..dded825 100644
--- a/src/etc/inc/services.inc
+++ b/src/etc/inc/services.inc
@@ -885,6 +885,11 @@ EOPP;
 				$dhcpdconf .= "		ignore bootp;\n";
 			}
 
+			// ignore-client-uids
+			if (isset($poolconf['ignoreclientuids'])) {
+				$dhcpdconf .= "		ignore-client-uids true;\n";
+			}
+
 			// netbios-name*
 			if (is_array($poolconf['winsserver']) && $poolconf['winsserver'][0] && ($poolconf['winsserver'][0] != $dhcpifconf['winsserver'][0])) {
 				$dhcpdconf .= "		option netbios-name-servers " . join(",", $poolconf['winsserver']) . ";\n";