C 语言中结构体相互嵌套有什么优点吗

最近看 wpa_supplicant 的代码,发现有许多的结构体都相互嵌套

什么情况下我们会选择这种相互嵌套的结构？

例如下面的 wpa_supplicant 和 wpa_global

exp:

struct wpa_supplicant {
    struct wpa_global *global;
    struct wpa_radio *radio; /* shared radio context */
    struct dl_list radio_list; /* list head: struct wpa_radio::ifaces */
    struct wpa_supplicant *parent;
    struct wpa_supplicant *p2pdev;
    struct wpa_supplicant *next;
    struct l2_packet_data *l2;
    struct l2_packet_data *l2_br;
    unsigned char own_addr[ETH_ALEN];
    unsigned char perm_addr[ETH_ALEN];
    char ifname[100];
...

struct wpa_global {
    struct wpa_supplicant *ifaces;
    struct wpa_params params;
    struct ctrl_iface_global_priv *ctrl_iface;
    struct wpas_dbus_priv *dbus;
    struct wpas_binder_priv *binder;
    void **drv_priv;
    size_t drv_count;
    struct os_time suspend_time;
    struct p2p_data *p2p;
    struct wpa_supplicant *p2p_init_wpa_s;
    struct wpa_supplicant *p2p_group_formation;
    struct wpa_supplicant *p2p_invite_group;
...