add ipaddress validation

README.md

@@ -5,3 +5,7 @@ http://doc.livedns.gandi.net/
 The config-template.txt file should be renamed to config.txt, and modified with your gandi.net API key, domain name, and A-record (@, dev, home, pi, etc).
 
 Every time the script runs, it will query an external service to retrieve the external IP of the machine, compare it to the current record (if any) in the zone at gandi.net, and then add a new record (if none currently exists), or delete then add a new record (if a record already exists).
+
+Requirements:
+  - Python 2.7
+  - ipaddress module (pip install ipaddress)

gandi-ddns.py

@@ -3,6 +3,7 @@ import sys
 import os
 import requests
 import json
+import ipaddress
 
 config_file = "config.txt"
 
@@ -20,7 +21,12 @@ def get_ip():
           print('Failed to retrieve external IP. Server responded with status_code: %d' % result.status_code)
           sys.exit(2)
 
-        return r.text
+        ip = r.text.rstrip() # strip \n and any trailing whitespace
+
+	if not(ipaddress.IPv4Address(ip)): # check if valid IPv4 address
+          sys.exit(2)
+
+        return ip
 
 def read_config(config_path):
         #Read configuration file
@@ -79,7 +85,7 @@ def main():
     url = '%sdomains/%s/records/%s/A' % (config.get(section, "api"), config.get(section, "domain"), config.get(section, "a_name"))
     print(url)
     #Discover External IP
-    external_ip = get_ip()[0:-1]
+    external_ip = get_ip()
     print("external IP is: %s" % external_ip)
 
     #Prepare record