1/*
2 * WPA Supplicant - background scan and roaming module: simple
3 * Copyright (c) 2009-2010, Jouni Malinen <j@w1.fi>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9#include "includes.h"
10
11#include "common.h"
12#include "eloop.h"
13#include "drivers/driver.h"
14#include "config_ssid.h"
15#include "wpa_supplicant_i.h"
16#include "driver_i.h"
17#include "scan.h"
18#include "bgscan.h"
19
20struct bgscan_simple_data {
21	struct wpa_supplicant *wpa_s;
22	const struct wpa_ssid *ssid;
23	int scan_interval;
24	int signal_threshold;
25	int short_scan_count; /* counter for scans using short scan interval */
26	int max_short_scans; /* maximum times we short-scan before back-off */
27	int short_interval; /* use if signal < threshold */
28	int long_interval; /* use if signal > threshold */
29	struct os_reltime last_bgscan;
30};
31
32
33static void bgscan_simple_timeout(void *eloop_ctx, void *timeout_ctx)
34{
35	struct bgscan_simple_data *data = eloop_ctx;
36	struct wpa_supplicant *wpa_s = data->wpa_s;
37	struct wpa_driver_scan_params params;
38
39	os_memset(&params, 0, sizeof(params));
40	params.num_ssids = 1;
41	params.ssids[0].ssid = data->ssid->ssid;
42	params.ssids[0].ssid_len = data->ssid->ssid_len;
43	params.freqs = data->ssid->scan_freq;
44
45	/*
46	 * A more advanced bgscan module would learn about most like channels
47	 * over time and request scans only for some channels (probing others
48	 * every now and then) to reduce effect on the data connection.
49	 */
50
51	wpa_printf(MSG_DEBUG, "bgscan simple: Request a background scan");
52	if (wpa_supplicant_trigger_scan(wpa_s, &params)) {
53		wpa_printf(MSG_DEBUG, "bgscan simple: Failed to trigger scan");
54		eloop_register_timeout(data->scan_interval, 0,
55				       bgscan_simple_timeout, data, NULL);
56	} else {
57		if (data->scan_interval == data->short_interval) {
58			data->short_scan_count++;
59			if (data->short_scan_count >= data->max_short_scans) {
60				data->scan_interval = data->long_interval;
61				wpa_printf(MSG_DEBUG, "bgscan simple: Backing "
62					   "off to long scan interval");
63			}
64		} else if (data->short_scan_count > 0) {
65			/*
66			 * If we lasted a long scan interval without any
67			 * CQM triggers, decrease the short-scan count,
68			 * which allows 1 more short-scan interval to
69			 * occur in the future when CQM triggers.
70			 */
71			data->short_scan_count--;
72		}
73		os_get_reltime(&data->last_bgscan);
74	}
75}
76
77
78static int bgscan_simple_get_params(struct bgscan_simple_data *data,
79				    const char *params)
80{
81	const char *pos;
82
83	data->short_interval = atoi(params);
84
85	pos = os_strchr(params, ':');
86	if (pos == NULL)
87		return 0;
88	pos++;
89	data->signal_threshold = atoi(pos);
90	pos = os_strchr(pos, ':');
91	if (pos == NULL) {
92		wpa_printf(MSG_ERROR, "bgscan simple: Missing scan interval "
93			   "for high signal");
94		return -1;
95	}
96	pos++;
97	data->long_interval = atoi(pos);
98
99	return 0;
100}
101
102
103static void * bgscan_simple_init(struct wpa_supplicant *wpa_s,
104				 const char *params,
105				 const struct wpa_ssid *ssid)
106{
107	struct bgscan_simple_data *data;
108
109	data = os_zalloc(sizeof(*data));
110	if (data == NULL)
111		return NULL;
112	data->wpa_s = wpa_s;
113	data->ssid = ssid;
114	if (bgscan_simple_get_params(data, params) < 0) {
115		os_free(data);
116		return NULL;
117	}
118	if (data->short_interval <= 0)
119		data->short_interval = 30;
120	if (data->long_interval <= 0)
121		data->long_interval = 30;
122
123	wpa_printf(MSG_DEBUG, "bgscan simple: Signal strength threshold %d  "
124		   "Short bgscan interval %d  Long bgscan interval %d",
125		   data->signal_threshold, data->short_interval,
126		   data->long_interval);
127
128	if (data->signal_threshold &&
129	    wpa_drv_signal_monitor(wpa_s, data->signal_threshold, 4) < 0) {
130		wpa_printf(MSG_ERROR, "bgscan simple: Failed to enable "
131			   "signal strength monitoring");
132	}
133
134	data->scan_interval = data->short_interval;
135	data->max_short_scans = data->long_interval / data->short_interval + 1;
136	if (data->signal_threshold) {
137		/* Poll for signal info to set initial scan interval */
138		struct wpa_signal_info siginfo;
139		if (wpa_drv_signal_poll(wpa_s, &siginfo) == 0 &&
140		    siginfo.current_signal >= data->signal_threshold)
141			data->scan_interval = data->long_interval;
142	}
143	wpa_printf(MSG_DEBUG, "bgscan simple: Init scan interval: %d",
144		   data->scan_interval);
145	eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
146			       data, NULL);
147
148	/*
149	 * This function is called immediately after an association, so it is
150	 * reasonable to assume that a scan was completed recently. This makes
151	 * us skip an immediate new scan in cases where the current signal
152	 * level is below the bgscan threshold.
153	 */
154	os_get_reltime(&data->last_bgscan);
155
156	return data;
157}
158
159
160static void bgscan_simple_deinit(void *priv)
161{
162	struct bgscan_simple_data *data = priv;
163	eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
164	if (data->signal_threshold)
165		wpa_drv_signal_monitor(data->wpa_s, 0, 0);
166	os_free(data);
167}
168
169
170static int bgscan_simple_notify_scan(void *priv,
171				     struct wpa_scan_results *scan_res)
172{
173	struct bgscan_simple_data *data = priv;
174
175	wpa_printf(MSG_DEBUG, "bgscan simple: scan result notification");
176
177	eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
178	eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
179			       data, NULL);
180
181	/*
182	 * A more advanced bgscan could process scan results internally, select
183	 * the BSS and request roam if needed. This sample uses the existing
184	 * BSS/ESS selection routine. Change this to return 1 if selection is
185	 * done inside the bgscan module.
186	 */
187
188	return 0;
189}
190
191
192static void bgscan_simple_notify_beacon_loss(void *priv)
193{
194	wpa_printf(MSG_DEBUG, "bgscan simple: beacon loss");
195	/* TODO: speed up background scanning */
196}
197
198
199static void bgscan_simple_notify_signal_change(void *priv, int above,
200					       int current_signal,
201					       int current_noise,
202					       int current_txrate)
203{
204	struct bgscan_simple_data *data = priv;
205	int scan = 0;
206	struct os_reltime now;
207
208	if (data->short_interval == data->long_interval ||
209	    data->signal_threshold == 0)
210		return;
211
212	wpa_printf(MSG_DEBUG, "bgscan simple: signal level changed "
213		   "(above=%d current_signal=%d current_noise=%d "
214		   "current_txrate=%d))", above, current_signal,
215		   current_noise, current_txrate);
216	if (data->scan_interval == data->long_interval && !above) {
217		wpa_printf(MSG_DEBUG, "bgscan simple: Start using short "
218			   "bgscan interval");
219		data->scan_interval = data->short_interval;
220		os_get_reltime(&now);
221		if (now.sec > data->last_bgscan.sec + 1 &&
222		    data->short_scan_count <= data->max_short_scans)
223			/*
224			 * If we haven't just previously (<1 second ago)
225			 * performed a scan, and we haven't depleted our
226			 * budget for short-scans, perform a scan
227			 * immediately.
228			 */
229			scan = 1;
230		else if (data->last_bgscan.sec + data->long_interval >
231			 now.sec + data->scan_interval) {
232			/*
233			 * Restart scan interval timer if currently scheduled
234			 * scan is too far in the future.
235			 */
236			eloop_cancel_timeout(bgscan_simple_timeout, data,
237					     NULL);
238			eloop_register_timeout(data->scan_interval, 0,
239					       bgscan_simple_timeout, data,
240					       NULL);
241		}
242	} else if (data->scan_interval == data->short_interval && above) {
243		wpa_printf(MSG_DEBUG, "bgscan simple: Start using long bgscan "
244			   "interval");
245		data->scan_interval = data->long_interval;
246		eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
247		eloop_register_timeout(data->scan_interval, 0,
248				       bgscan_simple_timeout, data, NULL);
249	} else if (!above) {
250		/*
251		 * Signal dropped further 4 dB. Request a new scan if we have
252		 * not yet scanned in a while.
253		 */
254		os_get_reltime(&now);
255		if (now.sec > data->last_bgscan.sec + 10)
256			scan = 1;
257	}
258
259	if (scan) {
260		wpa_printf(MSG_DEBUG, "bgscan simple: Trigger immediate scan");
261		eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
262		eloop_register_timeout(0, 0, bgscan_simple_timeout, data,
263				       NULL);
264	}
265}
266
267
268const struct bgscan_ops bgscan_simple_ops = {
269	.name = "simple",
270	.init = bgscan_simple_init,
271	.deinit = bgscan_simple_deinit,
272	.notify_scan = bgscan_simple_notify_scan,
273	.notify_beacon_loss = bgscan_simple_notify_beacon_loss,
274	.notify_signal_change = bgscan_simple_notify_signal_change,
275};
276