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                         /*
  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
  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
 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
 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
 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
 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
 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 };