Find own ipv6 address and loop updates

Dockerfile

@@ -3,5 +3,9 @@ RUN pip install --no-cache-dir --upgrade pip
 
 WORKDIR /app
 COPY src/ ./
-RUN pip install --no-cache-dir --requirement requirements.txt
+
+ARG APK_BUILD_DEPS=".build-deps gcc musl-dev linux-headers"
+RUN apk add --no-cache --virtual $APK_BUILD_DEPS\
+  && pip install --no-cache-dir --requirement requirements.txt \
+  && apk del $APK_BUILD_DEPS
 CMD [ "python", "ddns_update.py" ]

docker-compose.yml

@@ -5,4 +5,8 @@ services:
         container_name: strato-ddns
         build: 
             context: .
+        network_mode: host
         restart: always
+        environment:
+          - DDNS_HOST=my.host.name
+          - DDNS_KEY=secret

src/ddns_update.py

@@ -5,15 +5,54 @@ import requests
 from requests.exceptions import RequestException
 import click
 from os import environ
+from netifaces import interfaces, ifaddresses, AF_INET6
+from ipaddress import ip_address
+from time import sleep
 
 logging.basicConfig(level=logging.DEBUG)
 log = logging.getLogger("ddns updater")
 
 
+def get_global_address(address_family):
+    for interface in interfaces():
+        if_addresses = ifaddresses(interface)
+        if address_family in if_addresses:
+            for address in if_addresses[address_family]:
+                addr = ip_address(address["addr"].split("%")[0])
+                if addr.is_global:
+                    return addr
+    return None
+
+
+def get_global_ipv6():
+    return get_global_address(AF_INET6)
+
+
 def response_successful(response_text):
     return response_text.startswith("good") or response_text.startswith("nochg")
 
 
+def ddns_update(host, key, ip):
+    url = f"https://dyndns.strato.com/nic/update?hostname={host}&myip={ip}"
+
+    try:
+        response = requests.get(url, auth=(host, key), timeout=3)
+        response.raise_for_status()
+
+        if not response_successful(response.text):
+            raise RequestException("update failed")
+
+    except RequestException as error:
+        log.debug(response.text.strip())
+        log.error(error)
+        return False
+
+    log.debug(response.text.strip())
+    log.info("update successful")
+
+    return True
+
+
 @click.command()
 @click.option(
     "--host",
@@ -27,30 +66,17 @@ def response_successful(response_text):
     default=lambda: environ.get("DDNS_KEY", None),
     help="The ddns authorization key",
 )
-@click.option(
-    "--ip",
-    required=True,
-    default=lambda: environ.get("DDNS_IP", None),
-    help="The hosts new ip address in ipv4 or ipv6 format",
-)
-def ddns_update(host, key, ip):
-    url = f"https://dyndns.strato.com/nic/update?hostname={host}&myip={ip}"
-
-    try:
-        response = requests.get(url, auth=(host, key), timeout=3)
-        response.raise_for_status()
-
-        if not response_successful(response.text):
-            raise RequestException("update failed")
-
-    except RequestException as error:
-        log.debug(response.text.strip())
-        log.error(error)
-        return
-
-    log.debug(response.text.strip())
-    log.info("update successful")
+def loop_ddns_update(host, key):
+    last_ip = None
+    while True:
+        current_ip = get_global_ipv6()
+        if current_ip != last_ip:
+            if ddns_update(host, key, current_ip):
+                last_ip = current_ip
+        else:
+            log.debug("skipped update, ip address unchanged")
+        sleep(5)
 
 
 if __name__ == "__main__":
-    ddns_update()
+    loop_ddns_update()

src/requirements.txt

@@ -1,2 +1,4 @@
 Click==7.0
 requests==2.23.0
+netifaces==0.10.9
+ipaddress==1.0.23