code: func (c *controller) getConfigNetwork(name string) (*network, error) {
  	var n Network
  
  	s := func(current Network) bool {
  		if current.Info().ConfigOnly() && current.Name() == name {
  			n = current
  			return true
  		}
  		return false
  	}
  
  	c.WalkNetworks(s)
  
  	if n == nil {
  		return nil, types.NotFoundErrorf("configuration network %q not found", name)
  	}
  
  	return n.(*network), nil
  }
docs: // config-only network is looked up by name