contrib/wpa/wpa_supplicant/bgscan_simple.c

   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(&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
  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 };