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 program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Alternatively, this software may be distributed under the terms of BSD
  10  * license.
  11  *
  12  * See README and COPYING for more details.
  13  */
  14
  15 #include "includes.h"
  16
  17 #include "common.h"
  18 #include "eloop.h"
  19 #include "drivers/driver.h"
  20 #include "config_ssid.h"
  21 #include "wpa_supplicant_i.h"
  22 #include "driver_i.h"
  23 #include "scan.h"
  24 #include "bgscan.h"
  25
  26 struct bgscan_simple_data {
  27         struct wpa_supplicant *wpa_s;
  28         const struct wpa_ssid *ssid;
  29         int scan_interval;
  30         int signal_threshold;
  31         int short_interval; /* use if signal < threshold */
  32         int long_interval; /* use if signal > threshold */
  33         struct os_time last_bgscan;
  34 };
  35
  36
  37 static void bgscan_simple_timeout(void *eloop_ctx, void *timeout_ctx)
  38 {
  39         struct bgscan_simple_data *data = eloop_ctx;
  40         struct wpa_supplicant *wpa_s = data->wpa_s;
  41         struct wpa_driver_scan_params params;
  42
  43         os_memset(&params, 0, sizeof(params));
  44         params.num_ssids = 1;
  45         params.ssids[0].ssid = data->ssid->ssid;
  46         params.ssids[0].ssid_len = data->ssid->ssid_len;
  47         params.freqs = data->ssid->scan_freq;
  48
  49         /*
  50          * A more advanced bgscan module would learn about most like channels
  51          * over time and request scans only for some channels (probing others
  52          * every now and then) to reduce effect on the data connection.
  53          */
  54
  55         wpa_printf(MSG_DEBUG, "bgscan simple: Request a background scan");
  56         if (wpa_supplicant_trigger_scan(wpa_s, &params)) {
  57                 wpa_printf(MSG_DEBUG, "bgscan simple: Failed to trigger scan");
  58                 eloop_register_timeout(data->scan_interval, 0,
  59                                        bgscan_simple_timeout, data, NULL);
  60         } else
  61                 os_get_time(&data->last_bgscan);
  62 }
  63
  64
  65 static int bgscan_simple_get_params(struct bgscan_simple_data *data,
  66                                     const char *params)
  67 {
  68         const char *pos;
  69
  70         if (params == NULL)
  71                 return 0;
  72
  73         data->short_interval = atoi(params);
  74
  75         pos = os_strchr(params, ':');
  76         if (pos == NULL)
  77                 return 0;
  78         pos++;
  79         data->signal_threshold = atoi(pos);
  80         pos = os_strchr(pos, ':');
  81         if (pos == NULL) {
  82                 wpa_printf(MSG_ERROR, "bgscan simple: Missing scan interval "
  83                            "for high signal");
  84                 return -1;
  85         }
  86         pos++;
  87         data->long_interval = atoi(pos);
  88
  89         return 0;
  90 }
  91
  92
  93 static void * bgscan_simple_init(struct wpa_supplicant *wpa_s,
  94                                  const char *params,
  95                                  const struct wpa_ssid *ssid)
  96 {
  97         struct bgscan_simple_data *data;
  98
  99         data = os_zalloc(sizeof(*data));
 100         if (data == NULL)
 101                 return NULL;
 102         data->wpa_s = wpa_s;
 103         data->ssid = ssid;
 104         if (bgscan_simple_get_params(data, params) < 0) {
 105                 os_free(data);
 106                 return NULL;
 107         }
 108         if (data->short_interval <= 0)
 109                 data->short_interval = 30;
 110         if (data->long_interval <= 0)
 111                 data->long_interval = 30;
 112
 113         wpa_printf(MSG_DEBUG, "bgscan simple: Signal strength threshold %d  "
 114                    "Short bgscan interval %d  Long bgscan interval %d",
 115                    data->signal_threshold, data->short_interval,
 116                    data->long_interval);
 117
 118         if (data->signal_threshold &&
 119             wpa_drv_signal_monitor(wpa_s, data->signal_threshold, 4) < 0) {
 120                 wpa_printf(MSG_ERROR, "bgscan simple: Failed to enable "
 121                            "signal strength monitoring");
 122         }
 123
 124         data->scan_interval = data->short_interval;
 125         if (data->signal_threshold) {
 126                 /* Poll for signal info to set initial scan interval */
 127                 struct wpa_signal_info siginfo;
 128                 if (wpa_drv_signal_poll(wpa_s, &siginfo) == 0 &&
 129                     siginfo.current_signal >= data->signal_threshold)
 130                         data->scan_interval = data->long_interval;
 131         }
 132         wpa_printf(MSG_DEBUG, "bgscan simple: Init scan interval: %d",
 133                    data->scan_interval);
 134         eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
 135                                data, NULL);
 136
 137         /*
 138          * This function is called immediately after an association, so it is
 139          * reasonable to assume that a scan was completed recently. This makes
 140          * us skip an immediate new scan in cases where the current signal
 141          * level is below the bgscan threshold.
 142          */
 143         os_get_time(&data->last_bgscan);
 144
 145         return data;
 146 }
 147
 148
 149 static void bgscan_simple_deinit(void *priv)
 150 {
 151         struct bgscan_simple_data *data = priv;
 152         eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
 153         if (data->signal_threshold)
 154                 wpa_drv_signal_monitor(data->wpa_s, 0, 0);
 155         os_free(data);
 156 }
 157
 158
 159 static int bgscan_simple_notify_scan(void *priv,
 160                                      struct wpa_scan_results *scan_res)
 161 {
 162         struct bgscan_simple_data *data = priv;
 163
 164         wpa_printf(MSG_DEBUG, "bgscan simple: scan result notification");
 165
 166         eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
 167         eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
 168                                data, NULL);
 169
 170         /*
 171          * A more advanced bgscan could process scan results internally, select
 172          * the BSS and request roam if needed. This sample uses the existing
 173          * BSS/ESS selection routine. Change this to return 1 if selection is
 174          * done inside the bgscan module.
 175          */
 176
 177         return 0;
 178 }
 179
 180
 181 static void bgscan_simple_notify_beacon_loss(void *priv)
 182 {
 183         wpa_printf(MSG_DEBUG, "bgscan simple: beacon loss");
 184         /* TODO: speed up background scanning */
 185 }
 186
 187
 188 static void bgscan_simple_notify_signal_change(void *priv, int above,
 189                                                int current_signal,
 190                                                int current_noise,
 191                                                int current_txrate)
 192 {
 193         struct bgscan_simple_data *data = priv;
 194         int scan = 0;
 195         struct os_time now;
 196
 197         if (data->short_interval == data->long_interval ||
 198             data->signal_threshold == 0)
 199                 return;
 200
 201         wpa_printf(MSG_DEBUG, "bgscan simple: signal level changed "
 202                    "(above=%d current_signal=%d current_noise=%d "
 203                    "current_txrate=%d))", above, current_signal,
 204                    current_noise, current_txrate);
 205         if (data->scan_interval == data->long_interval && !above) {
 206                 wpa_printf(MSG_DEBUG, "bgscan simple: Start using short "
 207                            "bgscan interval");
 208                 data->scan_interval = data->short_interval;
 209                 os_get_time(&now);
 210                 if (now.sec > data->last_bgscan.sec + 1)
 211                         scan = 1;
 212         } else if (data->scan_interval == data->short_interval && above) {
 213                 wpa_printf(MSG_DEBUG, "bgscan simple: Start using long bgscan "
 214                            "interval");
 215                 data->scan_interval = data->long_interval;
 216                 eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
 217                 eloop_register_timeout(data->scan_interval, 0,
 218                                        bgscan_simple_timeout, data, NULL);
 219         } else if (!above) {
 220                 /*
 221                  * Signal dropped further 4 dB. Request a new scan if we have
 222                  * not yet scanned in a while.
 223                  */
 224                 os_get_time(&now);
 225                 if (now.sec > data->last_bgscan.sec + 10)
 226                         scan = 1;
 227         }
 228
 229         if (scan) {
 230                 wpa_printf(MSG_DEBUG, "bgscan simple: Trigger immediate scan");
 231                 eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
 232                 eloop_register_timeout(0, 0, bgscan_simple_timeout, data,
 233                                        NULL);
 234         }
 235 }
 236
 237
 238 const struct bgscan_ops bgscan_simple_ops = {
 239         .name = "simple",
 240         .init = bgscan_simple_init,
 241         .deinit = bgscan_simple_deinit,
 242         .notify_scan = bgscan_simple_notify_scan,
 243         .notify_beacon_loss = bgscan_simple_notify_beacon_loss,
 244         .notify_signal_change = bgscan_simple_notify_signal_change,
 245 };