Currently there is no implementation of NetworkChangeNotifier on Fuchsia. Also GetNetworkList() is broken: the POSIX implementation uses getifaddrs() which is not implemented on Fuchsia, see https://fuchsia.atlassian.net/browse/ZX-766 .

netstack implements FIDL interface that allows to get list of network interfaces, see Netstack::GetInterfaces() in garnet/public/lib/netstack/fidl/netstack.fidl . It can be used to implement GetNetworkList(). NetworkChangeNotifier could be implemented using the same API as well (polling it on a timer), but it would be better to extend Netstack interface to monitor for network changes. Filed https://fuchsia.atlassian.net/browse/NET-189 to track that issue.