MikroTik (RouterOS) script for automatically setting DNS records for clients when they obtain a DHCP lease

dhcp-leases-to-dns.rsc

# MikroTik (RouterOS) script for automatically setting DNS records
# for clients when they obtain a DHCP lease.
#
# author SmartFinn <https://gist.github.com/SmartFinn>
# based on https://github.com/karrots/ROS-DDNS

:local domain;
:local fqdn;
:local hostname;
:local safeHostname;
:local token "$leaseServerName-$leaseActMAC";
:local ttl [/ip dhcp-server get $leaseServerName lease-time];

# Getting the domain name from DHCP server. If a domain name is not
# specified will use hostname only
/ip dhcp-server network {
  :do {
    :set domain [get [find where ($leaseActIP in address)] domain];
#   Add a dot before domain name
    :set domain ("." . $domain);
  } on-error={
    :set domain "";
  };
};

:if ($leaseBound = 1) do={
  :log debug "$leaseServerName: Processing bound lease $leaseActMAC ($leaseActIP)";
  /ip dhcp-server lease {
    :set hostname [get [find active-mac-address=$leaseActMAC] host-name];
  };

# Delete unallowed chars from the hostname
  :for i from=0 to=([:len $hostname]-1) do={
    :local char [:pick $hostname $i];
    :if ($char~"[a-zA-Z0-9-]") do={
      :set safeHostname ($safeHostname . $char);
    };
  };

  :if ([:len $safeHostname] > 0) do={
    :set fqdn ($safeHostname . $domain);

    /ip dns static {
      :local itemId [find name=$fqdn];

      :if ($itemId != "") do={
#       This DNS entry already exists
        :if ([get $itemId comment] = $token) do={
          :if ([get $itemId address] != $leaseActIP) do={
            set $itemId address=$leaseActIP ttl=$ttl;
            :log info "Update DNS entry: $fqdn -> $leaseActIP ($leaseActMAC)";
          };
        } else={
          :log warning "Cannot to add DNS entry. $fqdn already exists";
        };
      } else={
#       Add DNS entry if it does not exist
        add name=$fqdn address=$leaseActIP ttl=$ttl comment=$token;
        :log info "Add DNS entry: $fqdn -> $leaseActIP ($leaseActMAC)";
      };
    };
  };
} else={
# Remove entry when lease expires ($leaseBound=0)
  :log debug "$leaseServerName: Processing deassigned lease $leaseActMAC ($leaseActIP)";
  /ip dns static {
    :local itemId [find comment=$token];
    :if ($itemId != "") do={
      :set fqdn ([get $itemId name]);
      remove $itemId;
      :log info "Remove DNS entry: $fqdn -> $leaseActIP ($leaseActMAC)";
    };
  };
};