Function defaultNetworkBackend

libnetwork/network/interface.go:103–162

(store storage.Store, conf *config.Config)

}

func defaultNetworkBackend(store storage.Store, conf *config.Config) (backend types.NetworkBackend, err error) {
	// read defaultNetworkBackend file
	file := filepath.Join(store.GraphRoot(), defaultNetworkBackendFileName)
	b, err := ioutil.ReadFile(file)
	if err == nil {
		val := string(b)
		if val == string(types.Netavark) {
			return types.Netavark, nil
		}
		if val == string(types.CNI) {
			return types.CNI, nil
		}
		return "", fmt.Errorf("unknown network backend value %q in %q", val, file)
	}
	// fail for all errors except ENOENT
	if !errors.Is(err, os.ErrNotExist) {
		return "", fmt.Errorf("could not read network backend value: %w", err)
	}

	// cache the network backend to make sure always the same one will be used
	defer func() {
		// only write when there is no error
		if err == nil {
			// nolint:gocritic
			if err := ioutils.AtomicWriteFile(file, []byte(backend), 0644); err != nil {
				logrus.Errorf("could not write network backend to file: %v", err)
			}
		}
	}()

	_, err = conf.FindHelperBinary("netavark", false)
	if err != nil {
		// if we cannot find netavark use CNI
		return types.CNI, nil
	}

	// now check if there are already containers, images and CNI networks (new install?)
	cons, err := store.Containers()
	if err != nil {
		return "", err
	}
	if len(cons) == 0 {
		imgs, err := store.Images()
		if err != nil {
			return "", err
		}
		if len(imgs) == 0 {
			cniInterface, err := getCniInterface(conf)
			if err == nil {
				nets, err := cniInterface.NetworkList()
				// there is always a default network so check <= 1
				if err == nil && len(nets) <= 1 {
					// we have a fresh system so use netavark
					return types.Netavark, nil
				}
			}
		}
	}