[pkg-wpa-devel] [PATCH] add event hysteresis

[Kel Modderman]

Jason, how does the following patch look to you?

Note, I used date instead of touch, simply because I'm aiming to use 
only /bin:/sbin if possible. It assumes that wpa_lock crap has already been 
removed.

Thanks, Kel.

Index: functions.sh
===================================================================
--- functions.sh	(revision 721)
+++ functions.sh	(working copy)
@@ -27,6 +27,7 @@
 WPA_CLI_PNAME="wpa_cli"
 WPA_CLI_PIDFILE="/var/run/wpa_action.$IFACE.pid"
 WPA_CLI_LOGFILE="/var/log/wpa_action.log"
+WPA_CLI_TIMESTAMP="/var/run/wpa_action.$IFACE.timestamp"
 
 # default ctrl_interface socket directory
 if [ -z "$WPA_CTRL_DIR" ]; then
@@ -661,6 +662,35 @@
 }
 
 #####################################################################
+## hysteresis checking
+# Networking tools such as dhcp clients used with ifupdown can
+# synthesize artificial ACTION events, particuarly just after a 
+# DISCONNECTED event is encountered immediately after a CONNECTED
+# event. This can lead to infinite event loops, and in extreme cases
+# has the potential to cause system instability.
+#
+wpa_hysteresis_event () {
+	echo "$(date +%s)" > "$WPA_CLI_TIMESTAMP"
+}
+
+wpa_hysteresis_check () {
+	if [ -f "$WPA_CLI_TIMESTAMP" ]; then
+		local TIME="$(date +%s)" TIMESTAMP TIMEWAIT
+		# current time minus 4 second event buffer
+		TIMEWAIT=$(($TIME-4))
+		# get time of last event
+		TIMESTAMP=$(cat $WPA_CLI_TIMESTAMP)
+		# compare values, allowing new action to be processed 
+		# only if last action was more than 4 seconds ago
+		if [ "$TIMEWAIT" -le "$TIMESTAMP" ]; then
+			echo "Ignoring $WPA_ACTION event, too soon after previous event"
+			return 1
+		fi
+	fi
+	return 0
+}
+
+#####################################################################
 ## identify ifupdown files
 # Identify ifupdown core files, so that state of the interface can be
 # checked. This is the weakest part of the wpa_action roaming scheme,
Index: wpa_action.sh
===================================================================
--- wpa_action.sh	(revision 721)
+++ wpa_action.sh	(working copy)
@@ -38,16 +38,19 @@
 case "$WPA_ACTION" in
 	"CONNECTED")
 		wpa_log_init
+		wpa_hysteresis_check || exit 1
 		wpa_log_action
 		wpa_log_environment
 		if ifupdown_check; then
 			ifup
 		fi
+		wpa_hysteresis_event
 		wpa_cli status
 		;;
 
 	"DISCONNECTED")
 		wpa_log_init
+		wpa_hysteresis_check || exit 1
 		wpa_log_action
 		wpa_log_environment
 		if ifupdown_check; then