sqm-scripts: make run.sh ignore spurious incomplete hotplug ifups

During system start up pppoe devices seem to receice ifup events
before the interface actually exists. This commit makes sqm's
run.sh script test whether the sys files for an interface
exist before actually trying to start an SQM instance on an
interface. This seems to nicely avoid starting on an not
fully established pppoe interface and avoids a number of
error messages during startup.

Signed-off-by: Sebastian Moeller <moeller0@gmx.de>

net/sqm-scripts/files/usr/lib/sqm/run.sh

@@ -23,7 +23,7 @@ case ${1} in
         ;;
     interface)
 	START_ON_IF=$2	# only process this interface
-	logger -t SQM -s "Re/starting sqm on interface ${START_ON_IF}"
+	logger -t SQM -s "Trying to re-start SQM on interface ${START_ON_IF}"
 	# TODO if $2 is empty just bail...
 	if [ -z ${START_ON_IF} ] ;
 	then
@@ -108,6 +108,14 @@ run_simple_qos() {
 	     logger -t SQM -s "${0} SQM qdiscs on ${IFACE} removed"
 	     return 0
 	fi
+	# in case of spurious hotplug events, try double check whether the interface is really up
+	if [ ! -d /sys/class/net/${IFACE} ] ;
+	then
+	    echo "${IFACE} does currently not exist, not even trying starting SQM on nothing." > /dev/kmsg
+	    logger -t SQM -s "${IFACE} does currently not exist, not even trying starting SQM on nothing."
+	    return 0
+	fi
+
 	logger -t SQM -s "${0} Queue Setup Script: ${SCRIPT}"
 	[ -x "$SCRIPT" ] && { $SCRIPT ; touch ${ACTIVE_STATE_FILE_FQN}; }
 }