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
20 struct 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
bgscan_simple_timeout(void * eloop_ctx,void * timeout_ctx)33 static 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(¶ms, 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, ¶ms)) {
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 /*
60 * Spend at most the duration of a long scan interval
61 * scanning at the short scan interval. After that,
62 * revert to the long scan interval.
63 */
64 if (data->short_scan_count > data->max_short_scans) {
65 data->scan_interval = data->long_interval;
66 wpa_printf(MSG_DEBUG, "bgscan simple: Backing "
67 "off to long scan interval");
68 }
69 } else if (data->short_scan_count > 0) {
70 /*
71 * If we lasted a long scan interval without any
72 * CQM triggers, decrease the short-scan count,
73 * which allows 1 more short-scan interval to
74 * occur in the future when CQM triggers.
75 */
76 data->short_scan_count--;
77 }
78 os_get_reltime(&data->last_bgscan);
79 }
80 }
81
82
bgscan_simple_get_params(struct bgscan_simple_data * data,const char * params)83 static int bgscan_simple_get_params(struct bgscan_simple_data *data,
84 const char *params)
85 {
86 const char *pos;
87
88 if (params == NULL)
89 return 0;
90
91 data->short_interval = atoi(params);
92
93 pos = os_strchr(params, ':');
94 if (pos == NULL)
95 return 0;
96 pos++;
97 data->signal_threshold = atoi(pos);
98 pos = os_strchr(pos, ':');
99 if (pos == NULL) {
100 wpa_printf(MSG_ERROR, "bgscan simple: Missing scan interval "
101 "for high signal");
102 return -1;
103 }
104 pos++;
105 data->long_interval = atoi(pos);
106
107 return 0;
108 }
109
110
bgscan_simple_init(struct wpa_supplicant * wpa_s,const char * params,const struct wpa_ssid * ssid)111 static void * bgscan_simple_init(struct wpa_supplicant *wpa_s,
112 const char *params,
113 const struct wpa_ssid *ssid)
114 {
115 struct bgscan_simple_data *data;
116
117 data = os_zalloc(sizeof(*data));
118 if (data == NULL)
119 return NULL;
120 data->wpa_s = wpa_s;
121 data->ssid = ssid;
122 if (bgscan_simple_get_params(data, params) < 0) {
123 os_free(data);
124 return NULL;
125 }
126 if (data->short_interval <= 0)
127 data->short_interval = 30;
128 if (data->long_interval <= 0)
129 data->long_interval = 30;
130
131 wpa_printf(MSG_DEBUG, "bgscan simple: Signal strength threshold %d "
132 "Short bgscan interval %d Long bgscan interval %d",
133 data->signal_threshold, data->short_interval,
134 data->long_interval);
135
136 if (data->signal_threshold &&
137 wpa_drv_signal_monitor(wpa_s, data->signal_threshold, 4) < 0) {
138 wpa_printf(MSG_ERROR, "bgscan simple: Failed to enable "
139 "signal strength monitoring");
140 }
141
142 data->scan_interval = data->short_interval;
143 data->max_short_scans = data->long_interval / data->short_interval + 1;
144 if (data->signal_threshold) {
145 /* Poll for signal info to set initial scan interval */
146 struct wpa_signal_info siginfo;
147 if (wpa_drv_signal_poll(wpa_s, &siginfo) == 0 &&
148 siginfo.current_signal >= data->signal_threshold)
149 data->scan_interval = data->long_interval;
150 }
151 wpa_printf(MSG_DEBUG, "bgscan simple: Init scan interval: %d",
152 data->scan_interval);
153 eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
154 data, NULL);
155
156 /*
157 * This function is called immediately after an association, so it is
158 * reasonable to assume that a scan was completed recently. This makes
159 * us skip an immediate new scan in cases where the current signal
160 * level is below the bgscan threshold.
161 */
162 os_get_reltime(&data->last_bgscan);
163
164 return data;
165 }
166
167
bgscan_simple_deinit(void * priv)168 static void bgscan_simple_deinit(void *priv)
169 {
170 struct bgscan_simple_data *data = priv;
171 eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
172 if (data->signal_threshold)
173 wpa_drv_signal_monitor(data->wpa_s, 0, 0);
174 os_free(data);
175 }
176
177
bgscan_simple_notify_scan(void * priv,struct wpa_scan_results * scan_res)178 static int bgscan_simple_notify_scan(void *priv,
179 struct wpa_scan_results *scan_res)
180 {
181 struct bgscan_simple_data *data = priv;
182
183 wpa_printf(MSG_DEBUG, "bgscan simple: scan result notification");
184
185 eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
186 eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
187 data, NULL);
188
189 /*
190 * A more advanced bgscan could process scan results internally, select
191 * the BSS and request roam if needed. This sample uses the existing
192 * BSS/ESS selection routine. Change this to return 1 if selection is
193 * done inside the bgscan module.
194 */
195
196 return 0;
197 }
198
199
bgscan_simple_notify_beacon_loss(void * priv)200 static void bgscan_simple_notify_beacon_loss(void *priv)
201 {
202 wpa_printf(MSG_DEBUG, "bgscan simple: beacon loss");
203 /* TODO: speed up background scanning */
204 }
205
206
bgscan_simple_notify_signal_change(void * priv,int above,int current_signal,int current_noise,int current_txrate)207 static void bgscan_simple_notify_signal_change(void *priv, int above,
208 int current_signal,
209 int current_noise,
210 int current_txrate)
211 {
212 struct bgscan_simple_data *data = priv;
213 int scan = 0;
214 struct os_reltime now;
215
216 if (data->short_interval == data->long_interval ||
217 data->signal_threshold == 0)
218 return;
219
220 wpa_printf(MSG_DEBUG, "bgscan simple: signal level changed "
221 "(above=%d current_signal=%d current_noise=%d "
222 "current_txrate=%d))", above, current_signal,
223 current_noise, current_txrate);
224 if (data->scan_interval == data->long_interval && !above) {
225 wpa_printf(MSG_DEBUG, "bgscan simple: Start using short "
226 "bgscan interval");
227 data->scan_interval = data->short_interval;
228 os_get_reltime(&now);
229 if (now.sec > data->last_bgscan.sec + 1 &&
230 data->short_scan_count <= data->max_short_scans)
231 /*
232 * If we haven't just previously (<1 second ago)
233 * performed a scan, and we haven't depleted our
234 * budget for short-scans, perform a scan
235 * immediately.
236 */
237 scan = 1;
238 else if (data->last_bgscan.sec + data->long_interval >
239 now.sec + data->scan_interval) {
240 /*
241 * Restart scan interval timer if currently scheduled
242 * scan is too far in the future.
243 */
244 eloop_cancel_timeout(bgscan_simple_timeout, data,
245 NULL);
246 eloop_register_timeout(data->scan_interval, 0,
247 bgscan_simple_timeout, data,
248 NULL);
249 }
250 } else if (data->scan_interval == data->short_interval && above) {
251 wpa_printf(MSG_DEBUG, "bgscan simple: Start using long bgscan "
252 "interval");
253 data->scan_interval = data->long_interval;
254 eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
255 eloop_register_timeout(data->scan_interval, 0,
256 bgscan_simple_timeout, data, NULL);
257 } else if (!above) {
258 /*
259 * Signal dropped further 4 dB. Request a new scan if we have
260 * not yet scanned in a while.
261 */
262 os_get_reltime(&now);
263 if (now.sec > data->last_bgscan.sec + 10)
264 scan = 1;
265 }
266
267 if (scan) {
268 wpa_printf(MSG_DEBUG, "bgscan simple: Trigger immediate scan");
269 eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
270 eloop_register_timeout(0, 0, bgscan_simple_timeout, data,
271 NULL);
272 }
273 }
274
275
276 const struct bgscan_ops bgscan_simple_ops = {
277 .name = "simple",
278 .init = bgscan_simple_init,
279 .deinit = bgscan_simple_deinit,
280 .notify_scan = bgscan_simple_notify_scan,
281 .notify_beacon_loss = bgscan_simple_notify_beacon_loss,
282 .notify_signal_change = bgscan_simple_notify_signal_change,
283 };
284