code: func (client *cniClient) add(runtimeConfig libcni.RuntimeConf,
  	cfg *Config,
  	pluginConfigFunc func(*Config) (string, *libcni.NetworkConfig, error)) (cnitypes.Result, error) {
  
  	deviceName, networkConfig, err := pluginConfigFunc(cfg)
  	if err != nil {
  		return nil, err
  	}
  	runtimeConfig.IfName = deviceName
  
  	return client.libcni.AddNetwork(networkConfig, &runtimeConfig)
  }
docs: // add invokes the ADD command of the given plugin