Add BSS table to track scan results without dropping information

Collect information from scan results into a BSS table that will not
expire information as quickly as scan results where every new scan,
no matter for how limited set of channels/SSIDs, clears all old
information.

For now, this is only used for D-Bus BSS added/removed notifications,
but this will likely be extended to be used internally instead of the
scan results to better support partial scans.

wpa_supplicant/Makefile

@@ -1162,6 +1162,11 @@ OBJS += $(SHA1OBJS) $(DESOBJS)
 
 OBJS_p += $(SHA1OBJS)
 
+ifdef CONFIG_BSS_TABLE
+CFLAGS += -DCONFIG_BSS_TABLE
+OBJS += bss.o
+endif
+
 ifdef CONFIG_BGSCAN_SIMPLE
 CFLAGS += -DCONFIG_BGSCAN_SIMPLE
 OBJS += bgscan_simple.o

wpa_supplicant/bss.c

@@ -0,0 +1,262 @@
+/*
+ * BSS table
+ * Copyright (c) 2009, 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 "utils/includes.h"
+
+#include "utils/common.h"
+#include "utils/eloop.h"
+#include "common/ieee802_11_defs.h"
+#include "drivers/driver.h"
+#include "wpa_supplicant_i.h"
+#include "notify.h"
+#include "bss.h"
+
+
+#ifndef WPA_BSS_MAX_COUNT
+#define WPA_BSS_MAX_COUNT 200
+#endif /* WPA_BSS_MAX_COUNT */
+
+/**
+ * WPA_BSS_EXPIRATION_PERIOD - Period of expiration run in seconds
+ */
+#define WPA_BSS_EXPIRATION_PERIOD 10
+
+/**
+ * WPA_BSS_EXPIRATION_AGE - BSS entry age after which it can be expired
+ *
+ * This value control the time in seconds after which a BSS entry gets removed
+ * if it has not been updated or is not in use.
+ */
+#define WPA_BSS_EXPIRATION_AGE 180
+
+/**
+ * WPA_BSS_EXPIRATION_SCAN_COUNT - Expire BSS after number of scans
+ *
+ * If the BSS entry has not been seen in this many scans, it will be removed.
+ * Value 1 means that the entry is removed after the first scan without the
+ * BSSID being seen. Larger values can be used to avoid BSS entries
+ * disappearing if they are not visible in every scan (e.g., low signal quality
+ * or interference).
+ */
+#define WPA_BSS_EXPIRATION_SCAN_COUNT 2
+
+
+static void wpa_bss_remove(struct wpa_supplicant *wpa_s, struct wpa_bss *bss)
+{
+	dl_list_del(&bss->list);
+	wpa_s->num_bss--;
+	wpa_printf(MSG_DEBUG, "BSS: Remove id %u BSSID " MACSTR " SSID '%s'",
+		   bss->id, MAC2STR(bss->bssid),
+		   wpa_ssid_txt(bss->ssid, bss->ssid_len));
+	wpas_notify_bss_removed(wpa_s, bss->bssid);
+	os_free(bss);
+}
+
+
+static struct wpa_bss * wpa_bss_get(struct wpa_supplicant *wpa_s,
+				    const u8 *bssid, const u8 *ssid,
+				    size_t ssid_len)
+{
+	struct wpa_bss *bss;
+	dl_list_for_each(bss, &wpa_s->bss, struct wpa_bss, list) {
+		if (os_memcmp(bss->bssid, bssid, ETH_ALEN) == 0 &&
+		    bss->ssid_len == ssid_len &&
+		    os_memcmp(bss->ssid, ssid, ssid_len) == 0)
+			return bss;
+	}
+	return NULL;
+}
+
+
+static void wpa_bss_copy_res(struct wpa_bss *dst, struct wpa_scan_res *src)
+{
+	os_time_t usec;
+
+	dst->flags = src->flags;
+	os_memcpy(dst->bssid, src->bssid, ETH_ALEN);
+	dst->freq = src->freq;
+	dst->beacon_int = src->beacon_int;
+	dst->caps = src->caps;
+	dst->qual = src->qual;
+	dst->noise = src->noise;
+	dst->level = src->level;
+	dst->tsf = src->tsf;
+
+	os_get_time(&dst->last_update);
+	dst->last_update.sec -= src->age / 1000;
+	usec = (src->age % 1000) * 1000;
+	if (dst->last_update.usec < usec) {
+		dst->last_update.sec--;
+		dst->last_update.usec += 1000000;
+	}
+	dst->last_update.usec -= usec;
+}
+
+
+static void wpa_bss_add(struct wpa_supplicant *wpa_s,
+			const u8 *ssid, size_t ssid_len,
+			struct wpa_scan_res *res)
+{
+	struct wpa_bss *bss;
+
+	bss = os_zalloc(sizeof(*bss) + res->ie_len);
+	if (bss == NULL)
+		return;
+	bss->id = wpa_s->bss_next_id++;
+	bss->last_update_idx = wpa_s->bss_update_idx;
+	wpa_bss_copy_res(bss, res);
+	os_memcpy(bss->ssid, ssid, ssid_len);
+	bss->ssid_len = ssid_len;
+	bss->ie_len = res->ie_len;
+	os_memcpy(bss + 1, res + 1, res->ie_len);
+
+	dl_list_add_tail(&wpa_s->bss, &bss->list);
+	wpa_s->num_bss++;
+	wpa_printf(MSG_DEBUG, "BSS: Add new id %u BSSID " MACSTR " SSID '%s'",
+		   bss->id, MAC2STR(bss->bssid), wpa_ssid_txt(ssid, ssid_len));
+	wpas_notify_bss_added(wpa_s, res->bssid);
+	if (wpa_s->num_bss > WPA_BSS_MAX_COUNT) {
+		/* Remove the oldest entry */
+		wpa_bss_remove(wpa_s, dl_list_first(&wpa_s->bss,
+						    struct wpa_bss, list));
+	}
+}
+
+
+static void wpa_bss_update(struct wpa_supplicant *wpa_s, struct wpa_bss *bss,
+			   struct wpa_scan_res *res)
+{
+	bss->scan_miss_count = 0;
+	bss->last_update_idx = wpa_s->bss_update_idx;
+	wpa_bss_copy_res(bss, res);
+	/* Move the entry to the end of the list */
+	dl_list_del(&bss->list);
+	if (bss->ie_len >= res->ie_len) {
+		os_memcpy(bss + 1, res + 1, res->ie_len);
+		bss->ie_len = res->ie_len;
+	} else {
+		struct wpa_bss *nbss;
+		nbss = os_realloc(bss, sizeof(*bss) + res->ie_len);
+		if (nbss) {
+			bss = nbss;
+			os_memcpy(bss + 1, res + 1, res->ie_len);
+			bss->ie_len = res->ie_len;
+		}
+	}
+	dl_list_add_tail(&wpa_s->bss, &bss->list);
+}
+
+
+void wpa_bss_update_start(struct wpa_supplicant *wpa_s)
+{
+	wpa_s->bss_update_idx++;
+	wpa_printf(MSG_DEBUG, "BSS: Start scan result update %u",
+		   wpa_s->bss_update_idx);
+}
+
+
+void wpa_bss_update_scan_res(struct wpa_supplicant *wpa_s,
+			     struct wpa_scan_res *res)
+{
+	const u8 *ssid;
+	struct wpa_bss *bss;
+
+	ssid = wpa_scan_get_ie(res, WLAN_EID_SSID);
+	if (ssid == NULL) {
+		wpa_printf(MSG_DEBUG, "BSS: No SSID IE included for " MACSTR,
+			   MAC2STR(res->bssid));
+		return;
+	}
+	if (ssid[1] > 32) {
+		wpa_printf(MSG_DEBUG, "BSS: Too long SSID IE included for "
+			   MACSTR, MAC2STR(res->bssid));
+		return;
+	}
+
+	/* TODO: add option for ignoring BSSes we are not interested in
+	 * (to save memory) */
+	bss = wpa_bss_get(wpa_s, res->bssid, ssid + 2, ssid[1]);
+	if (bss == NULL)
+		wpa_bss_add(wpa_s, ssid + 2, ssid[1], res);
+	else
+		wpa_bss_update(wpa_s, bss, res);
+}
+
+
+void wpa_bss_update_end(struct wpa_supplicant *wpa_s)
+{
+	struct wpa_bss *bss, *n;
+
+	/* TODO: expire only entries that were on the scanned frequencies/SSIDs
+	 * list; need to get info from driver about scanned frequencies and
+	 * SSIDs to be able to figure out which entries should be expired based
+	 * on this */
+
+	dl_list_for_each_safe(bss, n, &wpa_s->bss, struct wpa_bss, list) {
+		if (bss->last_update_idx < wpa_s->bss_update_idx)
+			bss->scan_miss_count++;
+		if (bss->scan_miss_count >= WPA_BSS_EXPIRATION_SCAN_COUNT) {
+			wpa_printf(MSG_DEBUG, "BSS: Expire BSS %u due to no "
+				   "match in scan", bss->id);
+			wpa_bss_remove(wpa_s, bss);
+		}
+	}
+}
+
+
+static void wpa_bss_timeout(void *eloop_ctx, void *timeout_ctx)
+{
+	struct wpa_supplicant *wpa_s = eloop_ctx;
+	struct wpa_bss *bss, *n;
+	struct os_time t;
+
+	if (dl_list_empty(&wpa_s->bss))
+		return;
+
+	os_get_time(&t);
+	t.sec -= WPA_BSS_EXPIRATION_AGE;
+
+	dl_list_for_each_safe(bss, n, &wpa_s->bss, struct wpa_bss, list) {
+		if (os_memcmp(bss->bssid, wpa_s->bssid, ETH_ALEN) == 0 ||
+		    os_memcmp(bss->bssid, wpa_s->pending_bssid, ETH_ALEN) == 0)
+			continue; /* do not expire BSSes that are in use */
+
+		if (os_time_before(&bss->last_update, &t)) {
+			wpa_printf(MSG_DEBUG, "BSS: Expire BSS %u due to age",
+				   bss->id);
+			wpa_bss_remove(wpa_s, bss);
+		} else
+			break;
+	}
+	eloop_register_timeout(WPA_BSS_EXPIRATION_PERIOD, 0,
+			       wpa_bss_timeout, wpa_s, NULL);
+}
+
+
+int wpa_bss_init(struct wpa_supplicant *wpa_s)
+{
+	dl_list_init(&wpa_s->bss);
+	eloop_register_timeout(WPA_BSS_EXPIRATION_PERIOD, 0,
+			       wpa_bss_timeout, wpa_s, NULL);
+	return 0;
+}
+
+
+void wpa_bss_deinit(struct wpa_supplicant *wpa_s)
+{
+	struct wpa_bss *bss, *n;
+	eloop_cancel_timeout(wpa_bss_timeout, wpa_s, NULL);
+	dl_list_for_each_safe(bss, n, &wpa_s->bss, struct wpa_bss, list)
+		wpa_bss_remove(wpa_s, bss);
+}

wpa_supplicant/bss.h

@@ -0,0 +1,74 @@
+/*
+ * BSS table
+ * Copyright (c) 2009, 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.
+ */
+
+#ifndef BSS_H
+#define BSS_H
+
+#define WPA_BSS_QUAL_INVALID		BIT(0)
+#define WPA_BSS_NOISE_INVALID		BIT(1)
+#define WPA_BSS_LEVEL_INVALID		BIT(2)
+#define WPA_BSS_LEVEL_DBM		BIT(3)
+#define WPA_BSS_AUTHENTICATED		BIT(4)
+#define WPA_BSS_ASSOCIATED		BIT(5)
+
+/**
+ * struct wpa_bss - BSS table
+ * @list: List entry for struct wpa_supplicant::bss
+ * @id: Unique identifier for this BSS entry
+ * @scan_miss_count: Number of counts without seeing this BSS
+ * @flags: information flags about the BSS/IBSS (WPA_BSS_*)
+ * @last_update_idx: Index of the last scan update
+ * @bssid: BSSID
+ * @freq: frequency of the channel in MHz (e.g., 2412 = channel 1)
+ * @beacon_int: beacon interval in TUs (host byte order)
+ * @caps: capability information field in host byte order
+ * @qual: signal quality
+ * @noise: noise level
+ * @level: signal level
+ * @tsf: Timestamp of last Beacon/Probe Response frame
+ * @last_update: Time of the last update (i.e., Beacon or Probe Response RX) 
+ * @ie_len: length of the following IE field in octets
+ *
+ * This structure is used to store information about neighboring BSSes in
+ * generic format. It is mainly updated based on scan results from the driver.
+ */
+struct wpa_bss {
+	struct dl_list list;
+	unsigned int id;
+	unsigned int scan_miss_count;
+	unsigned int last_update_idx;
+	unsigned int flags;
+	u8 bssid[ETH_ALEN];
+	u8 ssid[32];
+	size_t ssid_len;
+	int freq;
+	u16 beacon_int;
+	u16 caps;
+	int qual;
+	int noise;
+	int level;
+	u64 tsf;
+	struct os_time last_update;
+	size_t ie_len;
+	/* followed by ie_len octets of IEs */
+};
+
+void wpa_bss_update_start(struct wpa_supplicant *wpa_s);
+void wpa_bss_update_scan_res(struct wpa_supplicant *wpa_s,
+			     struct wpa_scan_res *res);
+void wpa_bss_update_end(struct wpa_supplicant *wpa_s);
+int wpa_bss_init(struct wpa_supplicant *wpa_s);
+void wpa_bss_deinit(struct wpa_supplicant *wpa_s);
+
+#endif /* BSS_H */

wpa_supplicant/defconfig

@@ -344,6 +344,8 @@ CONFIG_PEERKEY=y
 
 # Add support for new DBus control interface
 # (fi.w1.hostap.wpa_supplicant1)
+# Note: You will also need to enable CONFIG_BSS_TABLE if you want to have full
+# support for the documented D-Bus signals.
 #CONFIG_CTRL_IFACE_DBUS_NEW=y
 
 # Add introspection support for new DBus control interface (requires libxml2)
@@ -392,3 +394,6 @@ CONFIG_PEERKEY=y
 # This enables use of libbfd to get more detailed symbols for the backtraces
 # generated by CONFIG_WPA_TRACE=y.
 #CONFIG_WPA_TRACE_BFD=y
+
+# Maintain a local BSS table to track neighboring BSSes.
+CONFIG_BSS_TABLE=y

wpa_supplicant/wpa_supplicant.c

@@ -44,6 +44,7 @@
 #include "ap.h"
 #include "notify.h"
 #include "bgscan.h"
+#include "bss.h"
 
 const char *wpa_supplicant_version =
 "wpa_supplicant v" VERSION_STR "\n"
@@ -398,6 +399,9 @@ static void wpa_supplicant_cleanup(struct wpa_supplicant *wpa_s)
 
 	wpa_scan_results_free(wpa_s->scan_res);
 	wpa_s->scan_res = NULL;
+#ifdef CONFIG_BSS_TABLE
+	wpa_bss_deinit(wpa_s);
+#endif /* CONFIG_BSS_TABLE */
 
 	wpa_supplicant_cancel_scan(wpa_s);
 	wpa_supplicant_cancel_auth_timeout(wpa_s);
@@ -1559,64 +1563,16 @@ int wpa_supplicant_set_debug_params(struct wpa_global *global, int debug_level,
 }
 
 
-static void notify_bss_changes(struct wpa_supplicant *wpa_s,
-			       u8 (*prev_bssids)[ETH_ALEN], int prev_num,
-			       struct wpa_scan_results *new)
-{
-	int new_num, i, j;
-
-	new_num = new != NULL ? new->num : 0;
-	if (prev_bssids == NULL)
-		prev_num = 0;
-
-	for (i = 0; i < prev_num; i++) {
-		for (j = 0; j < new_num; j++) {
-			if (!os_memcmp(prev_bssids[i], new->res[j]->bssid,
-				       ETH_ALEN))
-				break;
-		}
-		if (j == new_num)
-			wpas_notify_bss_removed(wpa_s, prev_bssids[i]);
-	}
-	for (i = 0; i < new_num; i++) {
-		for (j = 0; j < prev_num; j++) {
-			if (!os_memcmp(new->res[i]->bssid, prev_bssids[j],
-				       ETH_ALEN))
-				break;
-		}
-		if (j == prev_num)
-			wpas_notify_bss_added(wpa_s, new->res[i]->bssid);
-	}
-}
-
-
 /**
  * wpa_supplicant_get_scan_results - Get scan results
  * @wpa_s: Pointer to wpa_supplicant data
  * Returns: 0 on success, -1 on failure
  *
- * This function is request the current scan results from the driver and stores
- * a local copy of the results in wpa_s->scan_res.
+ * This function request the current scan results from the driver and updates
+ * the local BSS list wpa_s->bss.
  */
 int wpa_supplicant_get_scan_results(struct wpa_supplicant *wpa_s)
 {
-	int ret, i, prev_scan_res_num;
-	u8 (*prev_scan_bssids)[ETH_ALEN];
-
-	prev_scan_res_num = wpa_s->scan_res ? wpa_s->scan_res->num : 0;
-	prev_scan_bssids = os_malloc(prev_scan_res_num * ETH_ALEN);
-
-	if (prev_scan_bssids) {
-		for (i = 0; i < prev_scan_res_num; i++) {
-			os_memcpy(prev_scan_bssids[i],
-				  wpa_s->scan_res->res[i]->bssid, ETH_ALEN);
-		}
-	} else {
-		wpa_printf(MSG_WARNING, "Not enough memory for old scan "
-			   "results list");
-		prev_scan_res_num = 0;
-	}
-
 	wpa_scan_results_free(wpa_s->scan_res);
 	if (wpa_s->drv_flags & WPA_DRIVER_FLAGS_USER_SPACE_MLME)
 		wpa_s->scan_res = ieee80211_sta_get_scan_results(wpa_s);
@@ -1624,17 +1580,23 @@ int wpa_supplicant_get_scan_results(struct wpa_supplicant *wpa_s)
 		wpa_s->scan_res = wpa_drv_get_scan_results2(wpa_s);
 	if (wpa_s->scan_res == NULL) {
 		wpa_printf(MSG_DEBUG, "Failed to get scan results");
-		ret = -1;
-	} else {
-		ret = 0;
-		wpa_scan_sort_results(wpa_s->scan_res);
+		return -1;
 	}
 
-	notify_bss_changes(wpa_s, prev_scan_bssids, prev_scan_res_num,
-			   wpa_s->scan_res);
-	os_free(prev_scan_bssids);
+	wpa_scan_sort_results(wpa_s->scan_res);
 
-	return ret;
+#ifdef CONFIG_BSS_TABLE
+	{
+		size_t i;
+		wpa_bss_update_start(wpa_s);
+		for (i = 0; i < wpa_s->scan_res->num; i++)
+			wpa_bss_update_scan_res(wpa_s,
+						wpa_s->scan_res->res[i]);
+		wpa_bss_update_end(wpa_s);
+	}
+#endif /* CONFIG_BSS_TABLE */
+
+	return 0;
 }
 
 
@@ -2137,6 +2099,11 @@ next_driver:
 	}
 #endif /* CONFIG_IBSS_RSN */
 
+#ifdef CONFIG_BSS_TABLE
+	if (wpa_bss_init(wpa_s) < 0)
+		return -1;
+#endif /* CONFIG_BSS_TABLE */
+
 	return 0;
 }
 

wpa_supplicant/wpa_supplicant_i.h

@@ -1,6 +1,6 @@
 /*
  * wpa_supplicant - Internal definitions
- * Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
+ * Copyright (c) 2003-2009, 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
@@ -15,6 +15,7 @@
 #ifndef WPA_SUPPLICANT_I_H
 #define WPA_SUPPLICANT_I_H
 
+#include "utils/list.h"
 #include "common/defs.h"
 
 extern const char *wpa_supplicant_version;
@@ -344,6 +345,10 @@ struct wpa_supplicant {
 #define WILDCARD_SSID_SCAN ((struct wpa_ssid *) 1)
 
 	struct wpa_scan_results *scan_res;
+	struct dl_list bss; /* struct wpa_bss::list */
+	size_t num_bss;
+	unsigned int bss_update_idx;
+	unsigned int bss_next_id;
 
 	struct wpa_driver_ops *driver;
 	int interface_removed; /* whether the network interface has been