Script to update now-dns.com IPv4/v6 address

dynupdate.py

#!/usr/bin/env python3

# Script to update now-dns.com IPv4/v6 address
# Based on https://now-dns.com/client/dynupdate.pl
# Depends on python3 and python3-requests installed in the system

import os
import re

import requests
from requests.auth import HTTPBasicAuth

# https://gist.github.com/dfee/6ed3a4b05cfe7a6faf40a2102408d5d8
IPV4SEG  = r'(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9])'
IPV4ADDR = r'(?:(?:' + IPV4SEG + r'\.){3,3}' + IPV4SEG + r')'
IPV6SEG  = r'(?:(?:[0-9a-fA-F]){1,4})'
IPV6GROUPS = (
    r'(?:' + IPV6SEG + r':){7,7}' + IPV6SEG,                  # 1:2:3:4:5:6:7:8
    r'(?:' + IPV6SEG + r':){1,7}:',                           # 1::                                 1:2:3:4:5:6:7::
    r'(?:' + IPV6SEG + r':){1,6}:' + IPV6SEG,                 # 1::8               1:2:3:4:5:6::8   1:2:3:4:5:6::8
    r'(?:' + IPV6SEG + r':){1,5}(?::' + IPV6SEG + r'){1,2}',  # 1::7:8             1:2:3:4:5::7:8   1:2:3:4:5::8
    r'(?:' + IPV6SEG + r':){1,4}(?::' + IPV6SEG + r'){1,3}',  # 1::6:7:8           1:2:3:4::6:7:8   1:2:3:4::8
    r'(?:' + IPV6SEG + r':){1,3}(?::' + IPV6SEG + r'){1,4}',  # 1::5:6:7:8         1:2:3::5:6:7:8   1:2:3::8
    r'(?:' + IPV6SEG + r':){1,2}(?::' + IPV6SEG + r'){1,5}',  # 1::4:5:6:7:8       1:2::4:5:6:7:8   1:2::8
    IPV6SEG + r':(?:(?::' + IPV6SEG + r'){1,6})',             # 1::3:4:5:6:7:8     1::3:4:5:6:7:8   1::8
    r':(?:(?::' + IPV6SEG + r'){1,7}|:)',                     # ::2:3:4:5:6:7:8    ::2:3:4:5:6:7:8  ::8       ::
    r'fe80:(?::' + IPV6SEG + r'){0,4}%[0-9a-zA-Z]{1,}',       # fe80::7:8%eth0     fe80::7:8%1  (link-local IPv6 addresses with zone index)
    r'::(?:ffff(?::0{1,4}){0,1}:){0,1}[^\s:]' + IPV4ADDR,     # ::255.255.255.255  ::ffff:255.255.255.255  ::ffff:0:255.255.255.255 (IPv4-mapped IPv6 addresses and IPv4-translated addresses)
    r'(?:' + IPV6SEG + r':){1,4}:[^\s:]' + IPV4ADDR,          # 2001:db8:3:4::192.0.2.33  64:ff9b::192.0.2.33 (IPv4-Embedded IPv6 Address)
)
IPV6ADDR = '|'.join(['(?:{})'.format(g) for g in IPV6GROUPS[::-1]])  # Reverse rows for greedy match

# Configuration
USERNAME   = os.environ.get("NOW_DNS_USERNAME")
PASSWORD   = os.environ.get("NOW_DNS_PASSWORD")
HOSTNAME   = os.environ.get("NOW_DNS_HOSTNAME")
UPDATE_URL = os.environ.get("NOW_DNS_UPDATE_URL", "https://now-dns.com/update")
TEST_IPV4  = os.environ.get("TEST_IPV4_URL", "http://checkip.dyndns.org/")
TEST_IPV6  = os.environ.get("TEST_IPV6_URL", "http://checkipv6.dyndns.org/")
IP_VERSION = os.environ.get("IP_VERSION", "4")
TIMEOUT    = int(os.environ.get("REQUEST_TIMEOUT", "10"))

# Now-DNS response codes
RESPONSE_CODES = {
                   "good": "OK",
                   "nochg": "OK",
                   "nohost": "ERROR",
                   "notfqdn": "ERROR",
                   "badauth": "ERROR",
                 }

# Get IP
if IP_VERSION == "4":
    ip_regex = IPV4ADDR
    test_url = TEST_IPV4
else:
    ip_regex = IPV6ADDR
    test_url = TEST_IPV6

response = requests.get(test_url)
ip = re.findall(ip_regex, response.text)[0]

# Create request
auth = HTTPBasicAuth(USERNAME, PASSWORD)
request = "{url}?hostname={hostname}&myip={ip}".format(
        url=UPDATE_URL, hostname=HOSTNAME, ip=ip)

# Run request
response = requests.get(request, auth=auth, timeout=TIMEOUT)

body = response.text

print("[{status}] Server returned message '{body}' for URL: {url}".format(
    status=RESPONSE_CODES.get(body, "UNKNOWN"), body=body, url=request))

dynupdate.service

[Unit]
Description=Run dynupdate.py script
After=network.target

[Service]
User=nobody
Type=oneshot
[email protected]
Environment=NOW_DNS_PASSWORD=password
Environment=NOW_DNS_HOSTNAME=mydns.now-dns.org
Environment=IP_VERSION=4
ExecStart=/usr/bin/python3 /opt/scripts/dynupdate.py

[Install]
WantedBy=multi-user.target

dynupdate.timer

[Unit]
Description=Run dynupdate.service each 10 minutes

[Timer]
OnCalendar=*:0/10
Persistent=true

[Install]
WantedBy=timers.target