nodewatcher: Prevent multiple instances at the same time

This is based on the configurehood-Patch from Tim Niemeyer.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Reviewed-by: Robert Langhammer <rlanghammer@web.de>
Reviewed-by: Fabian Bläse <fabian@blaese.de>

src/packages/fff/fff-nodewatcher/Makefile

@@ -1,7 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=fff-nodewatcher
-PKG_VERSION:=48
+PKG_VERSION:=49
 PKG_RELEASE:=1
 
 PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)

src/packages/fff/fff-nodewatcher/files/usr/sbin/nodewatcher

@@ -2,10 +2,18 @@
 # Netmon Nodewatcher (C) 2010-2012 Freifunk Oldenburg
 # License; GPL v3
 
-SCRIPT_VERSION="48"
-
 test -f /tmp/started || exit
 
+# Allow only one instance
+lockfile="/var/lock/${0##*/}.lock"
+if ! lock -n "$lockfile"; then
+        echo "Only one instance of $0 allowed."
+        exit 1
+fi
+trap "lock -u \"$lockfile\"" INT TERM EXIT
+
+SCRIPT_VERSION="49"
+
 #Get the configuration from the uci configuration file
 #If it does not exists, then get it from a normal bash file with variables.
 if [ -f /etc/config/nodewatcher ];then