code: func checkBridgeNetFiltering(config *networkConfiguration, i *bridgeInterface) error {
  	ipVer := getIPVersion(config)
  	iface := config.BridgeName
  	doEnable := func(ipVer ipVersion) error {
  		var ipVerName string
  		if ipVer == ipv4 {
  			ipVerName = "IPv4"
  		} else {
  			ipVerName = "IPv6"
  		}
  		enabled, err := isPacketForwardingEnabled(ipVer, iface)
  		if err != nil {
  			logrus.Warnf("failed to check %s forwarding: %v", ipVerName, err)
  		} else if enabled {
  			enabled, err := getKernelBoolParam(getBridgeNFKernelParam(ipVer))
  			if err != nil || enabled {
  				return err
  			}
  			return setKernelBoolParam(getBridgeNFKernelParam(ipVer), true)
  		}
  		return nil
  	}
  
  	switch ipVer {
  	case ipv4, ipv6:
  		return doEnable(ipVer)
  	case ipvboth:
  		v4err := doEnable(ipv4)
  		v6err := doEnable(ipv6)
  		if v4err == nil {
  			return v6err
  		}
  		return v4err
  	default:
  		return nil
  	}
  }
docs: //Enable bridge net filtering if ip forwarding is enabled. See github issue #11404