code: func (n *NIC) AddAddressWithOptions(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address, peb PrimaryEndpointBehavior) *tcpip.Error {
  	// Add the endpoint.
  	n.mu.Lock()
  	_, err := n.addAddressLocked(protocol, addr, peb, false)
  	n.mu.Unlock()
  
  	return err
  }
docs: // AddAddressWithOptions is the same as AddAddress, but allows you to specify
  // whether the new endpoint can be primary or not.