Poll Livebox and refresh OVH DynDNS

dyndns_refresh.py

#! /usr/bin/env python3

# Most internet box support DynDNS... but not my Livebox !
# Well it's more complicated than that: only a (very) limited
# number of DynDNS services are supported, and OVH is not among
# them... After all, why would the biggest French internet provider
# support the biggest French hosting service ? (╬ ಠ益ಠ)
#
# Anyway, this script poll the Livebox to retrieve it current IP address,
# then (if it has changed) update the OVH DynDNS service accordingly.

import urllib.request
from pathlib import Path
import re
import json
from base64 import b64encode

BASEDIR = Path(__file__).parent
# The last know IP is stored in this file, to avoid updating OVH DynDNS if the IP didn't change
CURRENT_IP_FILE = BASEDIR / "current_ip.txt"

TARGET_HOSTNAME = "<TODO>"  # Fill me !
OVH_DYNDNS_AUTH_USER = "<TODO>"  # Fill me !
OVH_DYNDNS_AUTH_PASSWORD = "<TODO>"  # Fill me !
LIVEBOX_API_ENDPOINT = "http://192.168.1.1/ws"

current_ip = CURRENT_IP_FILE.read_text().strip()
assert re.match(r"^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$", current_ip)

# 1) Retreive current IP from the Livebox

req = urllib.request.Request(
    url=LIVEBOX_API_ENDPOINT,
    method="POST",
    headers={
        "Content-Type": "application/x-sah-ws-1-call+json",
    },
    data=b'{"service":"NMC","method":"getWANStatus","parameters":{}}'
)
rep = urllib.request.urlopen(req)
assert rep.status == 200
new_ip = json.loads(rep.read().decode("utf8"))['result']['data']['IPAddress'].strip()
assert re.match(r"^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$", new_ip)

if new_ip == current_ip:
    print("IP didn't change, nothing to update")
    raise SystemExit(0)

print(f"IP has changed: {current_ip} -> {new_ip}")

# 2) Update OVH DynDNS with the new IP

req = urllib.request.Request(
    url=f"https://www.ovh.com/nic/update?system=dyndns&hostname={TARGET_HOSTNAME}&myip={new_ip}",
    method="GET",
    headers={
        "Authorization": "Basic {}".format(b64encode(f"{OVH_DYNDNS_AUTH_USER}:{OVH_DYNDNS_AUTH_PASSWORD}".encode("utf8")).decode()),
    },
)
rep = urllib.request.urlopen(req)
assert rep.status == 200
rep_status = rep.read().decode("utf8")
if rep_status.startswith("nochg"):
    print("OVH DynDNS updated, but already using this IP !")
elif rep_status.startswith("good"):
    print("OVH DynDNS updated !")
else:
    raise SystemExit("OVH DynDNS rejected the IP update: {}".format(rep_status))

# 3) Finally update the current IP file

CURRENT_IP_FILE.write_text(new_ip)