dns/ddclient: Add support for altering IPv6 addresses in ddclient plugin

dns/ddclient/src/opnsense/mvc/app/controllers/OPNsense/DynDNS/forms/dialogAccount.xml

@@ -91,6 +91,13 @@
         <label>Interface to monitor</label>
         <type>dropdown</type>
     </field>
+    <field>
+        <id>account.dynipv6host</id>
+        <label>Dynamic ipv6 host</label>
+        <type>text</type>
+        <advanced>true</advanced>
+        <help>Swap the interface identifier of the ipv6 address with the given partial ipv6 address (the least significant 64 bits of the address)</help>
+    </field>
     <field>
         <id>account.checkip_timeout</id>
         <label>Check ip timeout</label>

dns/ddclient/src/opnsense/mvc/app/models/OPNsense/DynDNS/DynDNS.xml

@@ -165,6 +165,11 @@
                         </check001>
                     </Constraints>
                 </checkip>
+                <dynipv6host type="TextField">
+                    <Required>N</Required>
+                    <mask>/^::(([0-9a-fA-F]{1,4}:){0,3}[0-9a-fA-F]{1,4})?$/u</mask>
+                    <ValidationMessage>Entry is not a valid partial ipv6 address definition (e.g. ::1000).</ValidationMessage>
+                </dynipv6host>
                 <checkip_timeout type="IntegerField">
                     <Default>10</Default>
                     <Required>Y</Required>

dns/ddclient/src/opnsense/scripts/ddclient/lib/account/__init__.py

@@ -118,7 +118,8 @@ def execute(self):
             service = self.settings.get('checkip'),
             proto = 'https' if self.settings.get('force_ssl', False) else 'http',
             timeout = str(self.settings.get('checkip_timeout', '10')),
-            interface = self.settings['interface'] if self.settings.get('interface' ,'').strip() != '' else None
+            interface = self.settings['interface'] if self.settings.get('interface' ,'').strip() != '' else None,
+            dynipv6host = self.settings['dynipv6host'] if self.settings.get('dynipv6host' ,'').strip() != '' else None
         )
 
         if self._current_address == None:

dns/ddclient/src/opnsense/scripts/ddclient/lib/address.py

@@ -1,5 +1,5 @@
 """
-    Copyright (c) 2022-2023 Ad Schellevis <ad@opnsense.org>
+    Copyright (c) 2022-2025 Ad Schellevis <ad@opnsense.org>
     All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
@@ -67,11 +67,29 @@ def extract_address(host, txt):
     return ""
 
 
-def checkip(service, proto='https', timeout='10', interface=None):
+def transform_ip(ip, ipv6host=None):
+    """ Changes ipv6 addresses if interface identifier is given
+        :param ip: ip address
+        :param ipv6host: 64 bit interface identifier
+        :return ipaddress.IPv4Address|ipaddress.IPv6Address
+        :raises ValueError: If the input can not be converted to an IPaddress
+    """
+    if ipv6host and ip.find(':') > 0:
+        # extract 64 bit long prefix and add ipv6host [64]bits
+        return ipaddress.ip_address(
+            ipaddress.ip_network("%s/64" % ip, strict=False).network_address.exploded[0:19] +
+            ipaddress.ip_address(ipv6host).exploded[19:]
+        )
+    else:
+        return ipaddress.ip_address(ip)
+
+
+def checkip(service, proto='https', timeout='10', interface=None, dynipv6host=None):
     """ find ip address using external services defined in checkip_service_list
         :param proto: protocol
         :param timeout: timeout in seconds
         :param interface: bind to interface
+        :param dynipv6host: optional partial ipv6 address
         :return: str
     """
     if service.startswith('web_'):
@@ -84,8 +102,13 @@ def checkip(service, proto='https', timeout='10', interface=None):
             params.append(interface)
         url = checkip_service_list[service] % proto
         params.append(url)
-        return extract_address(urlparse(url).hostname,
+        extracted_address = extract_address(urlparse(url).hostname,
             subprocess.run(params, capture_output=True, text=True).stdout)
+        try:
+            return str(transform_ip(extracted_address, dynipv6host))
+        except ValueError:
+            # invalid address
+            return ""
     elif service in ['if', 'if6'] and interface is not None:
         # return first non private IPv[4|6] interface address
         ifcfg = subprocess.run(['/sbin/ifconfig', interface], capture_output=True, text=True).stdout
@@ -94,7 +117,7 @@ def checkip(service, proto='https', timeout='10', interface=None):
                 parts = line.split()
                 if (parts[0] == 'inet' and service == 'if') or (parts[0] == 'inet6' and service == 'if6'):
                     try:
-                        address = ipaddress.ip_address(parts[1])
+                        address = transform_ip(parts[1], dynipv6host)
                         if address.is_global:
                             return str(address)
                     except ValueError:

dns/ddclient/src/opnsense/service/templates/OPNsense/ddclient/ddclient.json

@@ -22,6 +22,7 @@
             "zone": "{{ account.zone }}",
             "checkip": "{{ account.checkip }}",
             "interface": "{% if account.interface %}{{physical_interface(account.interface)}}{% endif %}",
+            "dynipv6host": "{{ account.dynipv6host }}",
             "checkip_timeout": {{ account.checkip_timeout }},
             "force_ssl": {{ "true" if account.force_ssl == '1' else "false"}},
             "ttl": "{{ account.ttl }}",