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nourselim0/cloudflare_ddns.py

Created October 4, 2025 02:22
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Cloudflare Dynamic DNS
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cloudflare_ddns.py
import json
import os
import sys
import tempfile
from typing import cast
import requests
from requests.models import Response
CLOUDFLARE_API_TOKEN = "YOUR_API_TOKEN"
ZONE_NAME = "example.com" # Your root domain
RECORD_NAME = "dynamic.example.com" # The subdomain to update
REQ_HEADERS = {
"Authorization": f"Bearer {CLOUDFLARE_API_TOKEN}",
"Content-Type": "application/json",
}
STATE_FILE = os.path.join(tempfile.gettempdir(), "cloudflare_ddns.json")
def load_state() -> dict:
if not os.path.exists(STATE_FILE):
return {}
try:
with open(STATE_FILE, mode="r", encoding="utf-8") as f:
return json.load(f)
except Exception:
return {}
def save_state(state: dict):
try:
with open(STATE_FILE, "w", encoding="utf-8") as f:
json.dump(state, f)
except Exception as e:
print(f"Warning, failed to write state file: {e}")
def handle_response(
resp: Response, http_err_msg: str, api_err_msg: str = None
) -> dict | str:
if resp.headers.get("Content-Type", "").startswith("application/json"):
data = cast(dict, resp.json())
err_text = json.dumps(data, indent=2)
else:
data = resp.text
err_text = data
if not resp.ok:
print(f"{http_err_msg} ({resp.status_code})\n{err_text}")
sys.exit(1)
if isinstance(data, str):
return data
if not data.get("success") or not data.get("result"):
print(f"{api_err_msg}\n{err_text}")
sys.exit(1)
return data
def get_external_ip() -> str:
resp = requests.get("https://api.ipify.org", timeout=10)
text = handle_response(resp, "Failed to fetch external IP")
return text.strip()
def get_zone_id() -> str:
url = f"https://api.cloudflare.com/client/v4/zones?name={ZONE_NAME}"
resp = requests.get(url, headers=REQ_HEADERS, timeout=10)
data = handle_response(
resp, "Failed to fetch zone info", f"Could not find zone: {ZONE_NAME}"
)
return data["result"][0]["id"]
def get_record_id(zone_id: str) -> tuple[str, str]:
url = f"https://api.cloudflare.com/client/v4/zones/{zone_id}/dns_records?type=A&name={RECORD_NAME}"
resp = requests.get(url, headers=REQ_HEADERS, timeout=10)
data = handle_response(
resp, "Failed to fetch DNS record", f"Could not find record: {RECORD_NAME}"
)
rec = data["result"][0]
return rec["id"], rec["content"]
def update_dns_record(zone_id: str, record_id: str, new_ip: str):
resp = requests.patch(
f"https://api.cloudflare.com/client/v4/zones/{zone_id}/dns_records/{record_id}",
json={
"type": "A",
"content": new_ip,
"ttl": 1, # 1 means "auto" (usually 5 min)
"proxied": False, # Dynamic DNS should not be proxied
},
headers=REQ_HEADERS,
timeout=10,
)
handle_response(
resp,
"Failed to update DNS record",
"Failed to update DNS record",
)
def main():
state = load_state()
current_ip = get_external_ip()
print(f"Current external IP: {current_ip}")
if state.get("last_external_ip") == current_ip:
print(f"No update needed, external IP is unchanged: {current_ip}")
sys.exit(0)
state["last_external_ip"] = current_ip
zone_id = state.get("zone_id") or get_zone_id()
state["zone_id"] = zone_id
record_id, old_ip = get_record_id(zone_id)
if old_ip == current_ip:
print(f"No update needed, DNS record is already set to {current_ip}")
else:
update_dns_record(zone_id, record_id, current_ip)
print(f"DNS record updated from {old_ip} to {current_ip}")
save_state(state)
if __name__ == "__main__":
main()
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nourselim0 commented Oct 4, 2025 •
edited
Loading

If you want this script to run on windows whenever any network interface connects or disconnects, you can use the Task Scheduler and add a trigger "on an event" then choose "Custom" and paste this XML:

<QueryList>
  <Query Id="0" Path="Microsoft-Windows-NetworkProfile/Operational">
    <Select Path="Microsoft-Windows-NetworkProfile/Operational">*[System[Provider[@Name='Microsoft-Windows-NetworkProfile'] and (EventID=10000 or EventID=10001)]]</Select>
  </Query>
</QueryList>

this basically means it tracks the events you see in the Event Viewer under Applications and Services Logs > Microsoft > Windows > NetworkProfile > Operational and filters by Event ID 10000 (connected) and 10001 (disconnected).

If anybody knows how to do something similar on any Linux distro, share it in a comment here ✨

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