// registerLinks writes the links to a file.
func (daemon *Daemon) registerLinks(container *container.Container, hostConfig *containertypes.HostConfig) error {
	if hostConfig == nil || hostConfig.NetworkMode.IsUserDefined() {
		return nil
	}

	for _, l := range hostConfig.Links {
		name, alias, err := runconfigopts.ParseLink(l)
		if err != nil {
			return err
		}
		child, err := daemon.GetContainer(name)
		if err != nil {
			//An error from daemon.GetContainer() means this name could not be found
			return fmt.Errorf("Could not get container for %s", name)
		}
		for child.HostConfig.NetworkMode.IsContainer() {
			parts := strings.SplitN(string(child.HostConfig.NetworkMode), ":", 2)
			child, err = daemon.GetContainer(parts[1])
			if err != nil {
				return fmt.Errorf("Could not get container for %s", parts[1])
			}
		}
		if child.HostConfig.NetworkMode.IsHost() {
			return runconfig.ErrConflictHostNetworkAndLinks
		}
		if err := daemon.registerLink(container, child, alias); err != nil {
			return err
		}
	}

	// After we load all the links into the daemon
	// set them to nil on the hostconfig
	return container.WriteHostConfig()
}

// BuildJoinOptions builds endpoint Join options from a given network.
func (container *Container) BuildJoinOptions(n libnetwork.Network) ([]libnetwork.EndpointOption, error) {
	var joinOptions []libnetwork.EndpointOption
	if epConfig, ok := container.NetworkSettings.Networks[n.Name()]; ok {
		for _, str := range epConfig.Links {
			name, alias, err := runconfigopts.ParseLink(str)
			if err != nil {
				return nil, err
			}
			joinOptions = append(joinOptions, libnetwork.CreateOptionAlias(name, alias))
		}
	}
	return joinOptions, nil
}