From 91776d3388e3b0d8082d7e5acaa18e7116080d7c Mon Sep 17 00:00:00 2001
From: Christian Hesse <mail@eworm.de>
Date: Tue, 12 Nov 2019 12:49:28 +0100
Subject: dhcp-to-dns: handle duplicate mac-address and host-name

* several leases for one mac address (changed client id, different net):
   -> take address from last lease
  Most likely this is the same devices which booted different OS or
  changed to different network.

* several leases for one host name:
   -> take address from first lease
  We see either different devices with same name or one device with
  several network interfaces. Keep the first name to mitigate stealing
  dns name.
---
 dhcp-to-dns | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/dhcp-to-dns b/dhcp-to-dns
index 7cd7fa0..e403881 100644
--- a/dhcp-to-dns
+++ b/dhcp-to-dns
@@ -44,9 +44,14 @@
   :if ([ :len $DnsRecord ] > 0) do={
     :local DnsIp [ / ip dns static get $DnsRecord address ];
 
-    :local HostLeases [ / ip dhcp-server lease find where mac-address=($LeaseVal->"mac-address") dynamic=yes ];
-    :if ([ :len $HostLeases ] > 1) do={
-      :set ($LeaseVal->"address") [ / ip dhcp-server lease get ($HostLeases->([ :len $HostLeases ] - 1)) address ];
+    :local DupMacLeases [ / ip dhcp-server lease find where mac-address=($LeaseVal->"mac-address") dynamic=yes ];
+    :if ([ :len $DupMacLeases ] > 1) do={
+      :set ($LeaseVal->"address") [ / ip dhcp-server lease get ($DupMacLeases->([ :len $DupMacLeases ] - 1)) address ];
+    }
+
+    :local DupHostLeases [ / ip dhcp-server lease find where host-name=($LeaseVal->"host-name") dynamic=yes ];
+    :if ([ :len $DupHostLeases ] > 1) do={
+      :set ($LeaseVal->"address") [ / ip dhcp-server lease get ($DupHostLeases->0) address ];
     }
 
     :if ($DnsIp = $LeaseVal->"address") do={
-- 
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