bundles/powerdns: add support for zone transfers

bundles/powerdns/metadata.py

@@ -1,3 +1,5 @@
+from bundlewrap.exceptions import NoSuchGroup
+
 defaults = {
     'apt': {
         'packages': {
@@ -23,3 +25,56 @@ defaults = {
         },
     },
 }
+
+
+@metadata_reactor
+def get_ips_of_secondary_nameservers(metadata):
+    # Secondary Nameservers can't be a primary nameserver at the same
+    # time. Return early if this is a secondary server.
+    if metadata.get('powerdns/is_secondary', False):
+        return {}
+
+    try:
+        nameservers = repo.nodes_in_group(metadata.get('powerdns/secondary_nameservers', ''))
+    except NoSuchGroup:
+        # This probably is no primary nameserver, either. Should be fine.
+        return {}
+
+    nodes = set()
+    for rnode in nameservers:
+        if rnode.name == node.name:
+            # We can't be primary and secondary at the same time
+            continue
+
+        nodes.add(rnode.name)
+
+    return {
+        'powerdns': {
+            'my_secondary_servers': nodes,
+        },
+    }
+
+
+@metadata_reactor
+def get_ips_of_primary_nameserver(metadata):
+    if not metadata.get('powerdns/is_secondary', False):
+        return {}
+
+    ips = set()
+    for rnode in repo.nodes:
+        if not node.has_bundle('powerdns'):
+            continue
+
+        if node.name in rnode.metadata.get('powerdns/my_secondary_servers', set()):
+            return {
+                'powerdns': {
+                    'my_primary_server': {
+                        'ips': {
+                            str(ip) for ip in repo.libs.tools.resolve_identifier(repo, rnode.name)
+                        },
+                        'node': rnode.name,
+                    },
+                },
+            }
+
+    return {}