X-Git-Url: http://www.project-moonshot.org/gitweb/?p=mech_eap.git;a=blobdiff_plain;f=libeap%2Fwpa_supplicant%2Fbgscan_simple.c;fp=libeap%2Fwpa_supplicant%2Fbgscan_simple.c;h=a467cc5b927195c79cfea7fd19b37f8f54bd3abe;hp=409d9ceaead008d6fee6bf5ba7fadf42d814533a;hb=f3746d009c6d7f50025af1f58a85e5fee9680be6;hpb=244f18d04aaf29e68495b5ffeb40ef5cca50942f

diff --git a/libeap/wpa_supplicant/bgscan_simple.c b/libeap/wpa_supplicant/bgscan_simple.c
index 409d9ce..a467cc5 100644
--- a/libeap/wpa_supplicant/bgscan_simple.c
+++ b/libeap/wpa_supplicant/bgscan_simple.c
@@ -2,14 +2,8 @@
  * WPA Supplicant - background scan and roaming module: simple
  * 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.
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
  */
 
 #include "includes.h"
@@ -28,9 +22,11 @@ struct bgscan_simple_data {
 	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_time last_bgscan;
+	struct os_reltime last_bgscan;
 };
 
 
@@ -57,8 +53,30 @@ static void bgscan_simple_timeout(void *eloop_ctx, void *timeout_ctx)
 		wpa_printf(MSG_DEBUG, "bgscan simple: Failed to trigger scan");
 		eloop_register_timeout(data->scan_interval, 0,
 				       bgscan_simple_timeout, data, NULL);
-	} else
-		os_get_time(&data->last_bgscan);
+	} 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);
+	}
 }
 
 
@@ -122,6 +140,16 @@ static void * bgscan_simple_init(struct wpa_supplicant *wpa_s,
 	}
 
 	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);
 
@@ -131,7 +159,7 @@ static void * bgscan_simple_init(struct wpa_supplicant *wpa_s,
 	 * us skip an immediate new scan in cases where the current signal
 	 * level is below the bgscan threshold.
 	 */
-	os_get_time(&data->last_bgscan);
+	os_get_reltime(&data->last_bgscan);
 
 	return data;
 }
@@ -183,7 +211,7 @@ static void bgscan_simple_notify_signal_change(void *priv, int above,
 {
 	struct bgscan_simple_data *data = priv;
 	int scan = 0;
-	struct os_time now;
+	struct os_reltime now;
 
 	if (data->short_interval == data->long_interval ||
 	    data->signal_threshold == 0)
@@ -197,9 +225,28 @@ static void bgscan_simple_notify_signal_change(void *priv, int above,
 		wpa_printf(MSG_DEBUG, "bgscan simple: Start using short "
 			   "bgscan interval");
 		data->scan_interval = data->short_interval;
-		os_get_time(&now);
-		if (now.sec > data->last_bgscan.sec + 1)
+		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");
@@ -212,7 +259,7 @@ static void bgscan_simple_notify_signal_change(void *priv, int above,
 		 * Signal dropped further 4 dB. Request a new scan if we have
 		 * not yet scanned in a while.
 		 */
-		os_get_time(&now);
+		os_get_reltime(&now);
 		if (now.sec > data->last_bgscan.sec + 10)
 			scan = 1;
 	}