T6948: kea: Add helpers to interact with runtime

- `kea_add_lease` to add a lease to the running kea server
- `kea_get_domain_from_subnet_id` to get the domain name from subnet id

Author: indrajitr

python/vyos/kea.py

@@ -1,4 +1,4 @@
-# Copyright 2023-2024 VyOS maintainers and contributors <maintainers@vyos.io>
+# Copyright 2023-2025 VyOS maintainers and contributors <maintainers@vyos.io>
 #
 # This library is free software; you can redistribute it and/or
 # modify it under the terms of the GNU Lesser General Public
@@ -329,6 +329,32 @@ def kea_get_leases(inet):
 
     return leases['arguments']['leases']
 
+def kea_add_lease(inet, ip_address, host_name=None, mac_address=None, iaid=None, duid=None, subnet_id=None):
+    args = {'ip-address': ip_address}
+
+    if host_name:
+        args['hostname'] = host_name
+
+    if subnet_id:
+        args['subnet-id'] = subnet_id
+
+    # IPv4 requires MAC address, IPv6 requires either MAC address or DUID
+    if mac_address:
+        args['hw-address'] = mac_address
+    if duid:
+        args['duid'] = duid
+
+    # IPv6 requires IAID
+    if inet == '6' and iaid:
+        args['iaid'] = iaid
+
+    result = _ctrl_socket_command(inet, f'lease{inet}-add', args)
+
+    if result and 'result' in result:
+        return result['result'] == 0
+
+    return False
+
 def kea_delete_lease(inet, ip_address):
     args = {'ip-address': ip_address}
 
@@ -362,3 +388,26 @@ def kea_get_pool_from_subnet_id(config, inet, subnet_id):
                 return network['name']
 
     return None
+
+def kea_get_domain_from_subnet_id(config, inet, subnet_id):
+    shared_networks = dict_search_args(config, 'arguments', f'Dhcp{inet}', 'shared-networks')
+
+    if not shared_networks:
+        return None
+
+    for network in shared_networks:
+        if f'subnet{inet}' not in network:
+            continue
+
+        for subnet in network[f'subnet{inet}']:
+            if 'id' in subnet and int(subnet['id']) == int(subnet_id):
+                for option in subnet['option-data']:
+                    if option['name'] == 'domain-name':
+                        return option['data']
+
+            # domain-name is not found in subnet, fallback to shared-network pool option
+            for option in network['option-data']:
+                if option['name'] == 'domain-name':
+                    return option['data']
+
+    return None