关于Android WIFI扫猫周期

Wifi scan period:

1) 如果当前Android OS并不存在已建立WIFI连接，则使用在编译时生成的build.prop中的"wifi.supplicant_scan_interval"属性的值（以秒为单位）

2) 如果Android OS已经建立一个活跃的WIFI连接，扫描周期将与1)中不同

3) 如果Android OS进入IDLE状态（early suspend），扫描周期会变为10min.

同时以上规则会被以下可变化的因素所部分改变：

a) 部分vendor会覆盖系统默认属性，比如：

254PRODUCT_PROPERTY_OVERRIDES += \
255	wifi.interface=wlan0 \
256	wifi.supplicant_scan_interval=15
257

b) 在Android4.2.2中，wpa_supplicant_6，wpa_supplicant_8中默认值为5s：

1725static struct wpa_supplicant * wpa_supplicant_alloc(void)
1726{
1727	struct wpa_supplicant *wpa_s;
1728
1729	wpa_s = os_zalloc(sizeof(*wpa_s));
1730	if (wpa_s == NULL)
1731		return NULL;
1732	wpa_s->scan_req = 1;
1733#ifdef ANDROID
1734	wpa_s->scan_interval = 5;
1735#endif
1736	return wpa_s;
1737}

而在wpa_supplicant_6, wpa_supplicant_8中同时都存在运行时设置(wpa_cli.c)该参数(一般release版Android，不root没法设置)的方式：

4827			reply_len = -1;
4828	} else if (os_strncmp(buf, "SCAN_INTERVAL ", 14) == 0) {
4829		if (wpa_supplicant_ctrl_iface_scan_interval(wpa_s, buf + 14))
4830			reply_len = -1;
4831	} else if (os_strcmp(buf, "INTERFACE_LIST") == 0) {
4832		reply_len = wpa_supplicant_global_iface_list(

 

2960static int wpa_supplicant_ctrl_iface_scan_interval(
2961	struct wpa_supplicant *wpa_s, char *cmd)
2962{
2963	int scan_int = atoi(cmd);
2964	return wpa_supplicant_set_scan_interval(wpa_s, scan_int);
2965}

1997int wpa_supplicant_set_scan_interval(struct wpa_supplicant *wpa_s,
1998				     int scan_interval)
1999{
2000	if (scan_interval < 0) {
2001		wpa_msg(wpa_s, MSG_ERROR, "Invalid scan interval %d",
2002			scan_interval);
2003		return -1;
2004	}
2005	wpa_msg(wpa_s, MSG_DEBUG, "Setting scan interval: %d sec",
2006		scan_interval);
2007	wpa_s->scan_interval = scan_interval;
2008
2009	return 0;
2010}