configurehood: Prevent multiple instances at the same time

This is based on a similar 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-hoods/Makefile

@@ -1,7 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=fff-hoods
-PKG_VERSION:=3
+PKG_VERSION:=4
 PKG_RELEASE:=1
 
 PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)

src/packages/fff/fff-hoods/files/usr/sbin/configurehood

@@ -1,5 +1,13 @@
 #!/bin/sh
 
+# 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
+
 . /usr/share/libubox/jshn.sh
 . /lib/functions/fff/keyxchange
 . /lib/functions/fff/network