swann: enable ndppd/radvd

ops/nixos/swann/default.nix

@@ -238,5 +238,28 @@ in {
     ];
   };
 
+  # This is cursed.
+  services.ndppd = {
+    enable = true;
+    proxies.ens-virginmedia.rules."2a02:88fd:f:d::/64" = {
+      method = "iface";
+      interface = "br-int";
+    };
+  };
+  services.radvd = {
+    enable = true;
+    config = ''
+      interface br-int {
+        AdvSendAdvert on;
+        MaxRtrAdvInterval 60;
+        AdvDefaultLifetime 180;
+        prefix 2a02:88fd:f:d::/64 {
+          AdvValidLifetime 7200;
+          AdvPreferredLifetime 3600;
+        };
+      };
+    '';
+  };
+
   system.stateVersion = "21.03";
 }