Convert OPNHome ISC DHCP mappings to Dnsmasq CSV import

convert_opnhome_isc_to_dnsmasq_csv.py

import xml.etree.ElementTree as ET
import csv
import sys

csv_writer = csv.writer(sys.stdout)

# Write header
csv_writer.writerow([
    "host", "domain", "ip", "client_id", "hwaddr",
    "lease_time", "ignore", "set_tag", "descr", "aliases"
])

# Read entire XML config from stdin
xml_data = sys.stdin.read()
root = ET.fromstring(xml_data)

dhcpd = root.find('dhcpd')
if dhcpd is None:
    sys.exit("No <dhcpd> section found in config.xml")

for iface in dhcpd:
    for staticmap in iface.findall('staticmap'):
        mac = staticmap.findtext('mac', '').strip()
        ip = staticmap.findtext('ipaddr', '').strip()
        hostname = staticmap.findtext('hostname', '').strip()

        if mac and ip:
            csv_writer.writerow([
                "",    # host
                "",    # domain
                ip,
                "",    # client_id
                mac,
                "", "", "", 
                hostname,  # descr
                ""     # aliases
            ])

This extracts the ISC static DHCP mappings and converts them into CSV file, which you can then import in OPNSense (starting with 25.1.6).

Note: The script downgrades the mapping's hostname field into the description field. In my previous experience with ISC, clients were not able to report their hostnames correctly — they would end up with no hostname at all, which is why I was enforcing (overriding) the hostname. This is not needed with Dnsmasq anymore, as it picks up client's own hostname just fine, hence the hostname -> description mapping.

However, If you actually prefer to keep your hostname overrides, you can do so by moving the hostname variable in writerow() method to the first column, i.e. csv_writer.writerow([hostname, ...

You can run the script easily by downloading it to your desktop and executing with:

ssh user@opnsense 'cat /conf/config.xml' | python3 your_download_folder/convert_opnhome_isc_to_dnsmasq_csv.py > dhcp-mappings.csv

It connects to your opnsense host via SSH and pipes its config.xml file (which contains the DHCP mappings) onto the convert_opnhome_isc_to_dnsmasq_csv.py python script, which runs on your desktop and saves the mappings into dhcp-mappings.csv file.

hi, what folder is /conf/config.xml located?

hi, what folder is /conf/config.xml located?

On opnsense. I downloaded it right to the firewall using fetch and then ran the command that way.

fetch https://gist.githubusercontent.com/wrobelda/403fe4e7ff542ce14a4bba9a06e40777/raw/a55012cd669e1f0b20e26fb65193b7e009ca52d4/convert_opnhome_isc_to_dnsmasq_csv.py

cat /conf/config.xml | python3 convert_opnhome_isc_to_dnsmasq_csv.py > dhcp-mappings.csv