1 files changed, 97 insertions, 0 deletions
diff --git a/dhcp-to-dns.rsc b/dhcp-to-dns.rsc
new file mode 100644
index 0000000..48f96b2
--- /dev/null
+++ b/dhcp-to-dns.rsc
@@ -0,0 +1,97 @@
+#!rsc by RouterOS
+# RouterOS script: dhcp-to-dns
+# Copyright (c) 2013-2023 Christian Hesse <mail@eworm.de>
+# https://git.eworm.de/cgit/routeros-scripts/about/COPYING.md
+#
+# provides: lease-script, order=20
+#
+# check DHCP leases and add/remove/update DNS entries
+# https://git.eworm.de/cgit/routeros-scripts/about/doc/dhcp-to-dns.md
+
+:local 0 "dhcp-to-dns";
+:global GlobalFunctionsReady;
+:while ($GlobalFunctionsReady != true) do={ :delay 500ms; }
+
+:global Domain;
+:global HostNameInZone;
+:global Identity;
+:global PrefixInZone;
+:global ServerNameInZone;
+
+:global CharacterReplace;
+:global IfThenElse;
+:global LogPrintExit2;
+:global ScriptLock;
+
+$ScriptLock $0 false 10;
+
+:local Zone \
+  ([ $IfThenElse ($PrefixInZone = true) "dhcp." ] . \
+   [ $IfThenElse ($HostNameInZone = true) ($Identity . ".") ] . $Domain);
+:local Ttl 5m;
+:local CommentPrefix ("managed by " . $0 . " for ");
+:local CommentString ("--- " . $0 . " above ---");
+
+:if ([ :len [ /ip/dns/static/find where comment=$CommentString name=- type=NXDOMAIN disabled ] ] = 0) do={
+  /ip/dns/static/add comment=$CommentString name=- type=NXDOMAIN disabled=yes;
+  $LogPrintExit2 warning $0 ("Added disabled static dns record with comment '" . $CommentString . "'.") false;
+}
+:local PlaceBefore ([ /ip/dns/static/find where comment=$CommentString name=- type=NXDOMAIN disabled ]->0);
+
+:foreach DnsRecord in=[ /ip/dns/static/find where comment ~ $CommentPrefix ] do={
+  :local DnsRecordVal [ /ip/dns/static/get $DnsRecord ];
+  :local MacAddress [ $CharacterReplace ($DnsRecordVal->"comment") $CommentPrefix "" ];
+  :if ([ :len [ /ip/dhcp-server/lease/find where mac-address=$MacAddress address=($DnsRecordVal->"address") status=bound ] ] > 0) do={
+    $LogPrintExit2 debug $0 ("Lease for " . $MacAddress . " (" . $DnsRecordVal->"name" . ") still exists. Not deleting DNS entry.") false;
+  } else={
+    :local Found false;
+    $LogPrintExit2 info $0 ("Lease expired for " . $MacAddress . " (" . $DnsRecordVal->"name" . "), deleting DNS entry.") false;
+    /ip/dns/static/remove $DnsRecord;
+  }
+}
+
+:foreach Lease in=[ /ip/dhcp-server/lease/find where status=bound ] do={
+  :local LeaseVal;
+  :do {
+    :set LeaseVal [ /ip/dhcp-server/lease/get $Lease ];
+  } on-error={
+    $LogPrintExit2 debug $0 ("A lease just vanished, ignoring.") false;
+  }
+
+  :if ([ :len ($LeaseVal->"address") ] > 0) do={
+    :local Comment ($CommentPrefix . $LeaseVal->"mac-address");
+    :local HostName [ $IfThenElse ([ :len ($LeaseVal->"host-name") ] = 0) \
+      [ $CharacterReplace ($LeaseVal->"mac-address") ":" "-" ] \
+      [ $CharacterReplace ($LeaseVal->"host-name") " " "" ] ];
+
+    :local Fqdn ($HostName . "." . [ $IfThenElse ($ServerNameInZone = true) ($LeaseVal->"server" . ".") ] . $Zone);
+    :local DnsRecord [ /ip/dns/static/find where name=$Fqdn ];
+    :if ([ :len $DnsRecord ] > 0) do={
+      :local DnsIp [ /ip/dns/static/get $DnsRecord address ];
+
+      :local DupMacLeases [ /ip/dhcp-server/lease/find where mac-address=($LeaseVal->"mac-address") status=bound ];
+      :if ([ :len $DupMacLeases ] > 1) do={
+        :set ($LeaseVal->"address") [ /ip/dhcp-server/lease/get ($DupMacLeases->([ :len $DupMacLeases ] - 1)) address ];
+      }
+
+      :if ([ :len ($LeaseVal->"host-name") ] > 0) do={
+        :local HostNameLeases [ /ip/dhcp-server/lease/find where host-name=($LeaseVal->"host-name") status=bound ];
+        :if ([ :len $HostNameLeases ] > 1) do={
+          :set ($LeaseVal->"address") [ /ip/dhcp-server/lease/get ($HostNameLeases->0) address ];
+        }
+      }
+
+      :if ($DnsIp = $LeaseVal->"address") do={
+        $LogPrintExit2 debug $0 ("DNS entry for " . $Fqdn . " does not need updating.") false;
+      } else={
+        $LogPrintExit2 info $0 ("Replacing DNS entry for " . $Fqdn . ", new address is " . $LeaseVal->"address" . ".") false;
+        /ip/dns/static/set name=$Fqdn address=($LeaseVal->"address") ttl=$Ttl comment=$Comment $DnsRecord;
+      }
+    } else={
+      $LogPrintExit2 info $0 ("Adding new DNS entry for " . $Fqdn . ", address is " . $LeaseVal->"address" . ".") false;
+      /ip/dns/static/add name=$Fqdn address=($LeaseVal->"address") ttl=$Ttl comment=$Comment place-before=$PlaceBefore;
+    }
+  } else={
+    $LogPrintExit2 debug $0 ("No address available... Ignoring.") false;
+  }
+}