android_get_control_socket() 是什麼用途啊?

看見ctrl_iface_unix.c的函式wpa_supplicant_global_ctrl_iface_init()有一段寫到
而ctrl為 wpa_wlan0

		/*		 * Backwards compatibility - try to open an Android control		 * socket and if that fails, assume this was a UNIX domain		 * socket instead.		 */		priv->sock = android_get_control_socket(ctrl);		if (priv->sock >= 0) {			wpa_printf(MSG_INFO,				   "Using Android control socket '%s'",				   ctrl);			goto havesock;		}

这个android_get_control_socket函数有什么作用呢？
android_get_control_socket函数定义在/system/core/include/cutils/sockets.h:

#define ANDROID_SOCKET_ENV_PREFIX   "ANDROID_SOCKET_"#define ANDROID_SOCKET_DIR      "/dev/socket"#ifdef __cplusplusextern "C" {#endif/* * android_get_control_socket - simple helper function to get the file * descriptor of our init-managed Unix domain socket. `name' is the name of the * socket, as given in init.rc. Returns -1 on error.翻成中文就是android_get_control_socket - 簡單的輔助功能，讓我們的初始化管理Unix domain socket的文件描述符(file descriptor)。 參數`name'是socket的名字，可在init.rc類型檔案被找到. 如果Return -1表示錯誤。 * * This is inline and not in libcutils proper because we want to use this in * third-party daemons with minimal modification. */static inline int android_get_control_socket(const char *name){    char key[64] = ANDROID_SOCKET_ENV_PREFIX;    const char *val;    int fd;    /* build our environment variable, counting cycles like a wolf ... */#if HAVE_STRLCPY    strlcpy(key + sizeof(ANDROID_SOCKET_ENV_PREFIX) - 1,        name,        sizeof(key) - sizeof(ANDROID_SOCKET_ENV_PREFIX));#else   /* for the host, which may lack the almightly strncpy ... */    strncpy(key + sizeof(ANDROID_SOCKET_ENV_PREFIX) - 1,        name,        sizeof(key) - sizeof(ANDROID_SOCKET_ENV_PREFIX));    key[sizeof(key)-1] = '\0';#endif    val = getenv(key); // socket名字和对应的socket文件的文件描述符以键值对的形式存储在环境变量中，     if (!val)        return -1;    errno = 0;    fd = strtol(val, NULL, 10);    if (errno)        return -1;    return fd;}

也就是說…

//这一步很关键，就是获取init.rc中配置的名为 “SOCKET_NAME定義的字串” 的socket
fdListen = android_get_control_socket(SOCKET_NAME);