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 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
bgscan_simple_get_params(struct bgscan_simple_data * data,const char * params)78 static 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
bgscan_simple_init(struct wpa_supplicant * wpa_s,const char * params,const struct wpa_ssid * ssid)103 static 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
bgscan_simple_deinit(void * priv)160 static 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
bgscan_simple_notify_scan(void * priv,struct wpa_scan_results * scan_res)170 static 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
bgscan_simple_notify_beacon_loss(void * priv)192 static 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
bgscan_simple_notify_signal_change(void * priv,int above,int current_signal,int current_noise,int current_txrate)199 static 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
268 const 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