Called when network interface metadata changes.

    Args:
      result: dict, the metadata response with the network interfaces.

def HandleNetworkInterfaces(self, result):
    """Called when network interface metadata changes.

    Args:
      result: dict, the metadata response with the network interfaces.
    """
    network_interfaces = self._ExtractInterfaceMetadata(result)

    if self.network_setup_enabled:
      self.network_setup.EnableNetworkInterfaces(
          [interface.name for interface in network_interfaces[1:]])

    for interface in network_interfaces:
      if self.ip_forwarding_enabled:
        self.ip_forwarding.HandleForwardedIps(
            interface.name, interface.forwarded_ips, interface.ip)