/*
* WPA Supplicant - background scan and roaming module: simple
* Copyright (c) 2009-2010, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "eloop.h"
#include "drivers/driver.h"
#include "config_ssid.h"
#include "wpa_supplicant_i.h"
#include "driver_i.h"
#include "scan.h"
#include "bgscan.h"
struct bgscan_simple_data {
struct wpa_supplicant *wpa_s;
const struct wpa_ssid *ssid;
int scan_interval;
int signal_threshold;
int short_scan_count; /* counter for scans using short scan interval */
int max_short_scans; /* maximum times we short-scan before back-off */
int short_interval; /* use if signal < threshold */
int long_interval; /* use if signal > threshold */
struct os_reltime last_bgscan;
};
static void bgscan_simple_timeout(void *eloop_ctx, void *timeout_ctx)
{
struct bgscan_simple_data *data = eloop_ctx;
struct wpa_supplicant *wpa_s = data->wpa_s;
struct wpa_driver_scan_params params;
os_memset(¶ms, 0, sizeof(params));
params.num_ssids = 1;
params.ssids[0].ssid = data->ssid->ssid;
params.ssids[0].ssid_len = data->ssid->ssid_len;
params.freqs = data->ssid->scan_freq;
/*
* A more advanced bgscan module would learn about most like channels
* over time and request scans only for some channels (probing others
* every now and then) to reduce effect on the data connection.
*/
wpa_printf(MSG_DEBUG, "bgscan simple: Request a background scan");
if (wpa_supplicant_trigger_scan(wpa_s, ¶ms)) {
wpa_printf(MSG_DEBUG, "bgscan simple: Failed to trigger scan");
eloop_register_timeout(data->scan_interval, 0,
bgscan_simple_timeout, data, NULL);
} else {
if (data->scan_interval == data->short_interval) {
data->short_scan_count++;
/*
* Spend at most the duration of a long scan interval
* scanning at the short scan interval. After that,
* revert to the long scan interval.
*/
if (data->short_scan_count > data->max_short_scans) {
data->scan_interval = data->long_interval;
wpa_printf(MSG_DEBUG, "bgscan simple: Backing "
"off to long scan interval");
}
} else if (data->short_scan_count > 0) {
/*
* If we lasted a long scan interval without any
* CQM triggers, decrease the short-scan count,
* which allows 1 more short-scan interval to
* occur in the future when CQM triggers.
*/
data->short_scan_count--;
}
os_get_reltime(&data->last_bgscan);
}
}
static int bgscan_simple_get_params(struct bgscan_simple_data *data,
const char *params)
{
const char *pos;
if (params == NULL)
return 0;
data->short_interval = atoi(params);
pos = os_strchr(params, ':');
if (pos == NULL)
return 0;
pos++;
data->signal_threshold = atoi(pos);
pos = os_strchr(pos, ':');
if (pos == NULL) {
wpa_printf(MSG_ERROR, "bgscan simple: Missing scan interval "
"for high signal");
return -1;
}
pos++;
data->long_interval = atoi(pos);
return 0;
}
static void * bgscan_simple_init(struct wpa_supplicant *wpa_s,
const char *params,
const struct wpa_ssid *ssid)
{
struct bgscan_simple_data *data;
data = os_zalloc(sizeof(*data));
if (data == NULL)
return NULL;
data->wpa_s = wpa_s;
data->ssid = ssid;
if (bgscan_simple_get_params(data, params) < 0) {
os_free(data);
return NULL;
}
if (data->short_interval <= 0)
data->short_interval = 30;
if (data->long_interval <= 0)
data->long_interval = 30;
wpa_printf(MSG_DEBUG, "bgscan simple: Signal strength threshold %d "
"Short bgscan interval %d Long bgscan interval %d",
data->signal_threshold, data->short_interval,
data->long_interval);
if (data->signal_threshold &&
wpa_drv_signal_monitor(wpa_s, data->signal_threshold, 4) < 0) {
wpa_printf(MSG_ERROR, "bgscan simple: Failed to enable "
"signal strength monitoring");
}
data->scan_interval = data->short_interval;
data->max_short_scans = data->long_interval / data->short_interval + 1;
if (data->signal_threshold) {
/* Poll for signal info to set initial scan interval */
struct wpa_signal_info siginfo;
if (wpa_drv_signal_poll(wpa_s, &siginfo) == 0 &&
siginfo.current_signal >= data->signal_threshold)
data->scan_interval = data->long_interval;
}
wpa_printf(MSG_DEBUG, "bgscan simple: Init scan interval: %d",
data->scan_interval);
eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
data, NULL);
/*
* This function is called immediately after an association, so it is
* reasonable to assume that a scan was completed recently. This makes
* us skip an immediate new scan in cases where the current signal
* level is below the bgscan threshold.
*/
os_get_reltime(&data->last_bgscan);
return data;
}
static void bgscan_simple_deinit(void *priv)
{
struct bgscan_simple_data *data = priv;
eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
if (data->signal_threshold)
wpa_drv_signal_monitor(data->wpa_s, 0, 0);
os_free(data);
}
static int bgscan_simple_notify_scan(void *priv,
struct wpa_scan_results *scan_res)
{
struct bgscan_simple_data *data = priv;
wpa_printf(MSG_DEBUG, "bgscan simple: scan result notification");
eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
eloop_register_timeout(data->scan_interval, 0, bgscan_simple_timeout,
data, NULL);
/*
* A more advanced bgscan could process scan results internally, select
* the BSS and request roam if needed. This sample uses the existing
* BSS/ESS selection routine. Change this to return 1 if selection is
* done inside the bgscan module.
*/
return 0;
}
static void bgscan_simple_notify_beacon_loss(void *priv)
{
wpa_printf(MSG_DEBUG, "bgscan simple: beacon loss");
/* TODO: speed up background scanning */
}
static void bgscan_simple_notify_signal_change(void *priv, int above,
int current_signal,
int current_noise,
int current_txrate)
{
struct bgscan_simple_data *data = priv;
int scan = 0;
struct os_reltime now;
if (data->short_interval == data->long_interval ||
data->signal_threshold == 0)
return;
wpa_printf(MSG_DEBUG, "bgscan simple: signal level changed "
"(above=%d current_signal=%d current_noise=%d "
"current_txrate=%d))", above, current_signal,
current_noise, current_txrate);
if (data->scan_interval == data->long_interval && !above) {
wpa_printf(MSG_DEBUG, "bgscan simple: Start using short "
"bgscan interval");
data->scan_interval = data->short_interval;
os_get_reltime(&now);
if (now.sec > data->last_bgscan.sec + 1 &&
data->short_scan_count <= data->max_short_scans)
/*
* If we haven't just previously (<1 second ago)
* performed a scan, and we haven't depleted our
* budget for short-scans, perform a scan
* immediately.
*/
scan = 1;
else if (data->last_bgscan.sec + data->long_interval >
now.sec + data->scan_interval) {
/*
* Restart scan interval timer if currently scheduled
* scan is too far in the future.
*/
eloop_cancel_timeout(bgscan_simple_timeout, data,
NULL);
eloop_register_timeout(data->scan_interval, 0,
bgscan_simple_timeout, data,
NULL);
}
} else if (data->scan_interval == data->short_interval && above) {
wpa_printf(MSG_DEBUG, "bgscan simple: Start using long bgscan "
"interval");
data->scan_interval = data->long_interval;
eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
eloop_register_timeout(data->scan_interval, 0,
bgscan_simple_timeout, data, NULL);
} else if (!above) {
/*
* Signal dropped further 4 dB. Request a new scan if we have
* not yet scanned in a while.
*/
os_get_reltime(&now);
if (now.sec > data->last_bgscan.sec + 10)
scan = 1;
}
if (scan) {
wpa_printf(MSG_DEBUG, "bgscan simple: Trigger immediate scan");
eloop_cancel_timeout(bgscan_simple_timeout, data, NULL);
eloop_register_timeout(0, 0, bgscan_simple_timeout, data,
NULL);
}
}
const struct bgscan_ops bgscan_simple_ops = {
.name = "simple",
.init = bgscan_simple_init,
.deinit = bgscan_simple_deinit,
.notify_scan = bgscan_simple_notify_scan,
.notify_beacon_loss = bgscan_simple_notify_beacon_loss,
.notify_signal_change = bgscan_simple_notify_signal_change,
};