bgscan: Add starting point for more advanced bgscan module: learn

This is based on the bgscan "simple" module and this initial commit
does not add any new functionality.

wpa_supplicant/Makefile

@@ -1184,6 +1184,12 @@ OBJS += bgscan_simple.o
 NEED_BGSCAN=y
 endif
 
+ifdef CONFIG_BGSCAN_LEARN
+CFLAGS += -DCONFIG_BGSCAN_LEARN
+OBJS += bgscan_learn.o
+NEED_BGSCAN=y
+endif
+
 ifdef NEED_BGSCAN
 CFLAGS += -DCONFIG_BGSCAN
 OBJS += bgscan.o

wpa_supplicant/bgscan.c

@@ -22,11 +22,17 @@
 #ifdef CONFIG_BGSCAN_SIMPLE
 extern const struct bgscan_ops bgscan_simple_ops;
 #endif /* CONFIG_BGSCAN_SIMPLE */
+#ifdef CONFIG_BGSCAN_LEARN
+extern const struct bgscan_ops bgscan_learn_ops;
+#endif /* CONFIG_BGSCAN_LEARN */
 
 static const struct bgscan_ops * bgscan_modules[] = {
 #ifdef CONFIG_BGSCAN_SIMPLE
 	&bgscan_simple_ops,
 #endif /* CONFIG_BGSCAN_SIMPLE */
+#ifdef CONFIG_BGSCAN_LEARN
+	&bgscan_learn_ops,
+#endif /* CONFIG_BGSCAN_LEARN */
 	NULL
 };
 

wpa_supplicant/bgscan_learn.c

@@ -0,0 +1,220 @@
+/*
+ * WPA Supplicant - background scan and roaming module: learn
+ * Copyright (c) 2009-2010, Jouni Malinen <j@w1.fi>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Alternatively, this software may be distributed under the terms of BSD
+ * license.
+ *
+ * See README and COPYING 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_learn_data {
+	struct wpa_supplicant *wpa_s;
+	const struct wpa_ssid *ssid;
+	int scan_interval;
+	int signal_threshold;
+	int short_interval; /* use if signal < threshold */
+	int long_interval; /* use if signal > threshold */
+	struct os_time last_bgscan;
+};
+
+
+static void bgscan_learn_timeout(void *eloop_ctx, void *timeout_ctx)
+{
+	struct bgscan_learn_data *data = eloop_ctx;
+	struct wpa_supplicant *wpa_s = data->wpa_s;
+	struct wpa_driver_scan_params params;
+
+	os_memset(&params, 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 learn: Request a background scan");
+	if (wpa_supplicant_trigger_scan(wpa_s, &params)) {
+		wpa_printf(MSG_DEBUG, "bgscan learn: Failed to trigger scan");
+		eloop_register_timeout(data->scan_interval, 0,
+				       bgscan_learn_timeout, data, NULL);
+	} else
+		os_get_time(&data->last_bgscan);
+}
+
+
+static int bgscan_learn_get_params(struct bgscan_learn_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 learn: Missing scan interval "
+			   "for high signal");
+		return -1;
+	}
+	pos++;
+	data->long_interval = atoi(pos);
+
+	return 0;
+}
+
+
+static void * bgscan_learn_init(struct wpa_supplicant *wpa_s,
+				const char *params,
+				const struct wpa_ssid *ssid)
+{
+	struct bgscan_learn_data *data;
+
+	data = os_zalloc(sizeof(*data));
+	if (data == NULL)
+		return NULL;
+	data->wpa_s = wpa_s;
+	data->ssid = ssid;
+	if (bgscan_learn_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 learn: 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 learn: Failed to enable "
+			   "signal strength monitoring");
+	}
+
+	data->scan_interval = data->short_interval;
+	eloop_register_timeout(data->scan_interval, 0, bgscan_learn_timeout,
+			       data, NULL);
+	return data;
+}
+
+
+static void bgscan_learn_deinit(void *priv)
+{
+	struct bgscan_learn_data *data = priv;
+	eloop_cancel_timeout(bgscan_learn_timeout, data, NULL);
+	if (data->signal_threshold)
+		wpa_drv_signal_monitor(data->wpa_s, 0, 0);
+	os_free(data);
+}
+
+
+static int bgscan_learn_notify_scan(void *priv,
+				    struct wpa_scan_results *scan_res)
+{
+	struct bgscan_learn_data *data = priv;
+
+	wpa_printf(MSG_DEBUG, "bgscan learn: scan result notification");
+
+	eloop_cancel_timeout(bgscan_learn_timeout, data, NULL);
+	eloop_register_timeout(data->scan_interval, 0, bgscan_learn_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_learn_notify_beacon_loss(void *priv)
+{
+	wpa_printf(MSG_DEBUG, "bgscan learn: beacon loss");
+	/* TODO: speed up background scanning */
+}
+
+
+static void bgscan_learn_notify_signal_change(void *priv, int above)
+{
+	struct bgscan_learn_data *data = priv;
+
+	if (data->short_interval == data->long_interval ||
+	    data->signal_threshold == 0)
+		return;
+
+	wpa_printf(MSG_DEBUG, "bgscan learn: signal level changed "
+		   "(above=%d)", above);
+	if (data->scan_interval == data->long_interval && !above) {
+		wpa_printf(MSG_DEBUG, "bgscan learn: Trigger immediate scan "
+			   "and start using short bgscan interval");
+		data->scan_interval = data->short_interval;
+		eloop_cancel_timeout(bgscan_learn_timeout, data, NULL);
+		eloop_register_timeout(0, 0, bgscan_learn_timeout, data,
+				       NULL);
+	} else if (data->scan_interval == data->short_interval && above) {
+		wpa_printf(MSG_DEBUG, "bgscan learn: Start using long bgscan "
+			   "interval");
+		data->scan_interval = data->long_interval;
+		eloop_cancel_timeout(bgscan_learn_timeout, data, NULL);
+		eloop_register_timeout(data->scan_interval, 0,
+				       bgscan_learn_timeout, data, NULL);
+	} else if (!above) {
+		struct os_time now;
+		/*
+		 * Signal dropped further 4 dB. Request a new scan if we have
+		 * not yet scanned in a while.
+		 */
+		os_get_time(&now);
+		if (now.sec > data->last_bgscan.sec + 10) {
+			wpa_printf(MSG_DEBUG, "bgscan learn: Trigger "
+				   "immediate scan");
+			eloop_cancel_timeout(bgscan_learn_timeout, data,
+					     NULL);
+			eloop_register_timeout(0, 0, bgscan_learn_timeout,
+					       data, NULL);
+		}
+	}
+}
+
+
+const struct bgscan_ops bgscan_learn_ops = {
+	.name = "learn",
+	.init = bgscan_learn_init,
+	.deinit = bgscan_learn_deinit,
+	.notify_scan = bgscan_learn_notify_scan,
+	.notify_beacon_loss = bgscan_learn_notify_beacon_loss,
+	.notify_signal_change = bgscan_learn_notify_signal_change,
+};