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 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 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 } 101 102 103 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 } 158 159 160 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 } 168 169 170 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 } 190 191 192 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 } 197 198 199 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