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         eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
 126                                data, NULL);
 127         return data;
 128 }
 129
 130
 131 static void bgscan_simple_deinit(void *priv)
 132 {
 133         struct bgscan_simple_data *data = priv;
 134         eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
 135         if (data->signal_threshold)
 136                 wpa_drv_signal_monitor(data->wpa_s, 0, 0);
 137         os_free(data);
 138 }
 139
 140
 141 static int bgscan_simple_notify_scan(void *priv)
 142 {
 143         struct bgscan_simple_data *data = priv;
 144
 145         wpa_printf(MSG_DEBUG, "bgscan simple: scan result notification");
 146
 147         eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
 148         eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
 149                                data, NULL);
 150
 151         /*
 152          * A more advanced bgscan could process scan results internally, select
 153          * the BSS and request roam if needed. This sample uses the existing
 154          * BSS/ESS selection routine. Change this to return 1 if selection is
 155          * done inside the bgscan module.
 156          */
 157
 158         return 0;
 159 }
 160
 161
 162 static void bgscan_simple_notify_beacon_loss(void *priv)
 163 {
 164         wpa_printf(MSG_DEBUG, "bgscan simple: beacon loss");
 165         /* TODO: speed up background scanning */
 166 }
 167
 168
 169 static void bgscan_simple_notify_signal_change(void *priv, int above)
 170 {
 171         struct bgscan_simple_data *data = priv;
 172
 173         if (data->short_interval == data->long_interval ||
 174             data->signal_threshold == 0)
 175                 return;
 176
 177         wpa_printf(MSG_DEBUG, "bgscan simple: signal level changed "
 178                    "(above=%d)", above);
 179         if (data->scan_interval == data->long_interval && !above) {
 180                 wpa_printf(MSG_DEBUG, "bgscan simple: Trigger immediate scan "
 181                            "and start using short bgscan interval");
 182                 data->scan_interval = data->short_interval;
 183                 eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
 184                 eloop_register_timeout(0, 0, bgscan_simple_timeout, data,
 185                                        NULL);
 186         } else if (data->scan_interval == data->short_interval && above) {
 187                 wpa_printf(MSG_DEBUG, "bgscan simple: Start using long bgscan "
 188                            "interval");
 189                 data->scan_interval = data->long_interval;
 190                 eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
 191                 eloop_register_timeout(data->scan_interval, 0,
 192                                        bgscan_simple_timeout, data, NULL);
 193         } else if (!above) {
 194                 struct os_time now;
 195                 /*
 196                  * Signal dropped further 4 dB. Request a new scan if we have
 197                  * not yet scanned in a while.
 198                  */
 199                 os_get_time(&now);
 200                 if (now.sec > data->last_bgscan.sec + 10) {
 201                         wpa_printf(MSG_DEBUG, "bgscan simple: Trigger "
 202                                    "immediate scan");
 203                         eloop_cancel_timeout(bgscan_simple_timeout, data,
 204                                              NULL);
 205                         eloop_register_timeout(0, 0, bgscan_simple_timeout,
 206                                                data, NULL);
 207                 }
 208         }
 209 }
 210
 211
 212 const struct bgscan_ops bgscan_simple_ops = {
 213         .name = "simple",
 214         .init = bgscan_simple_init,
 215         .deinit = bgscan_simple_deinit,
 216         .notify_scan = bgscan_simple_notify_scan,
 217         .notify_beacon_loss = bgscan_simple_notify_beacon_loss,
 218         .notify_signal_change = bgscan_simple_notify_signal_change,
 219 };