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#+date: <2022-02-10>
#+title: Dynamic DNS with Njalla API
#+description:
* Njalla's API
As noted in my recent post about
[[file:///blog/ditching-cloudflare/][switching to Njalla from
Cloudflare]], I was searching for a way to replace my very easy-to-use
bash script to [[file:///blog/cloudflare-dns-api/][update Cloudflare's
DNS via their API]].
To reiterate what I said in those posts, this is a common necessity for
those of us who have non-static IP addresses that can change at any
moment due to ISP policy.
In order to keep a home server running smoothly, the server admin needs
to have a process to constantly monitor their public IP address and
update their domain's DNS records if it changes.
This post explains how to use Python to update Njalla's DNS records
whenever a machine's public IP address changes.
** Creating a Token
To use Njalla's API, you will first need to create a token that will be
used to authenticate you every time you call the API. Luckily, this is
very easy to do if you have an account with Njalla.
Simply go the [[https://njal.la/settings/api/][API Settings]] page and
click the =Add Token= button. Next, enter a name for the token and click
=Add=.
Finally, click the =Manage= button next to your newly created token and
copy the =API Token= field.
** Finding the Correct API Request
Once you have a token, you're ready to call the Njalla API for any
number of requests. For a full listing of available requests, see the
[[https://njal.la/api/][Njalla API Documentation]].
For this demo, we are using the =list-records= and =edit-record=
requests.
The =list-records= request requires the following payload to be sent
when calling the API:
#+begin_src txt
params: {
domain: string
}
#+end_src
The =edit-record= request requires the following payload to be sent when
calling the API:
#+begin_src txt
params: {
domain: string
id: int
content: string
}
#+end_src
* Server Set-Up
To create this script, we will be using Python. By default, I use Python
3 on my servers, so please note that I did not test this in Python 2,
and I do not know if Python 2 will work for this.
** Creating the Script
First, find a suitable place to create your script. Personally, I just
create a directory called =ddns= in my home directory:
#+begin_src sh
mkdir ~/ddns
#+end_src
Next, create a Python script file:
#+begin_src sh
nano ~/ddns/ddns.py
#+end_src
The following code snippet is quite long, so I won't go into depth on
each part. However, I suggest you read through the entire script before
running it; it is quite simple and contains comments to help explain
each code block.
:warning: *Note*: You will need to update the following variables for
this to work:
- =token=: This is the Njalla API token you created earlier.
- =user_domain=: This is the top-level domain you want to modify.
- =include_subdomains=: Set this to =True= if you also want to modify
subdomains found under the TLD.
- =subdomains=: If =include_subdomains= = =True=, you can include your
list of subdomains to be modified here.
#+begin_src python
#!/usr/bin/python
# -*- coding: utf-8 -*-
# Import Python modules
from requests import get
import requests
import json
# Set global variables
url = 'https://njal.la/api/1/'
token = '<your-api-token>'
user_domain = 'example.com'
include_subdomains = True
subdomains = ['one', 'two']
# Main API call function
def njalla(method, **params):
headers = {'Authorization': 'Njalla ' + token}
response = requests.post(url, json={'method': method,
'params': params}, headers=headers).json()
if 'result' not in response:
raise Exception('API Error', response)
return response['result']
# Gather all DNS records for a domain
def get_records(domain):
return njalla('list-records', domain=user_domain)
# Update a DNS record for a domain
def update_record(domain, record_id, record_content):
return njalla('edit-record', domain=domain, id=record_id,
content=record_content)
# Get public IP addresses
ipv4 = get('https://api.ipify.org').text
print('IPv4: {}'.format(ipv4))
ipv6 = get('https://api64.ipify.org').text
print('IPv6: {}'.format(ipv6))
# Call API to get all DNS records
data = get_records(user_domain)
# Loop through records and check if each one is IPv4 (A) or IPv6 (AAAA)
# Update only if DNS is different from server IP
for record in data['records']:
if record['name'] == '@' or (include_subdomains and record['name'] \
in subdomains):
if record['type'] == 'A':
if record['content'] == ipv4:
print(record['type'], 'record for', record['name'],
'already matches public IPv4 address. Skipping...'
)
else:
print('IPv4 of', ipv4,
'does not match Njalla's value of',
record['content'], '. Updating...')
update_record(user_domain, record['id'], ipv4)
elif record['type'] == 'AAAA':
if record['content'] == ipv6:
print(record['type'], 'record for', record['name'],
'already matches public IPv6 address. Skipping...'
)
else:
print('IPv6 of', ipv6,
'does not match Njalla's value of',
record['content'], '. Updating...')
update_record(user_domain, record['id'], ipv6)
#+end_src
** Running the Script
Once you've created the script and are ready to test it, run the
following command:
#+begin_src sh
python3 ~/ddns/ddns.py
#+end_src
** Setting the Script to Run Automatically
To make sure the scripts run automatically, add it to the =cron= file so
that it will run on a schedule. To do this, open the =cron= file:
#+begin_src sh
crontab -e
#+end_src
In the cron file, paste the following at the bottom of the editor in
order to check the IP every five minutes:
#+begin_src sh
,*/5 ** ** ** ** python3 /home/<your_username>/ddns/ddns.py
#+end_src
|
