Script that can automatically configure DNS domain resolvers for systemd-resolved on QEMU network adapters

libvirt-network-dns.py

#!/usr/bin/python

import os.path
import subprocess
import sys
import xml.etree.ElementTree as ET

def main():
    iface = sys.argv[1]
    hook_case = sys.argv[2]
    if hook_case != "started":
        return

    libvirt_dir = os.path.abspath(os.path.join(
        os.path.relpath(__file__), "..", ".."))
    iface_def = ET.parse(os.path.join(libvirt_dir, "qemu", "networks", f"{iface}.xml"))

    bridge_info = iface_def.find("bridge")
    if bridge_info is None or "name" not in bridge_info.attrib:
        return
    bridge = bridge_info.attrib["name"]

    domain_info = iface_def.find("domain")
    if domain_info is None or "name" not in domain_info.attrib:
        return
    domain = domain_info.attrib["name"]

    ip_info = iface_def.find("ip")
    if ip_info is None or "address" not in ip_info.attrib:
        return
    host_ip = ip_info.attrib["address"]
    dns_ip = host_ip.split(".")
    dns_ip[-1] = "10"

    subprocess.check_call(["resolvectl", "dns", bridge, ".".join(dns_ip)])
    subprocess.check_call(["resolvectl", "domain", bridge, f"~{domain}"])

if __name__ == '__main__':
    main()