squid-probe

#!/bin/sh

# proxy, proxy0, proxy1
IPV4="192.0.2.1 192.0.2.2 192.0.2.3"
IPV6="2001:db8:ffff:a000:fce9:4633:2f26:4a5b 2001:db8:ffff:a000:3b30:4100:d401:2a97 2001:db8:ffff:a000:a0d3:5619:9943:8390"

add () {
	[ "$IPV4" ] && [ -z "$(ip addr show dev lo scope global | grep " inet ")" ] \
			&& echo -n $IPV4 | xargs -d' ' -I{} ip addr add {}/32 dev lo
	[ "$IPV6" ] && [ -z "$(ip addr show dev lo scope global | grep " inet6 ")" ] \
			&& echo -n $IPV6 | xargs -d' ' -I{} ip addr add {}/128 dev lo

	return 0
}

del () {
	[ "$IPV4" ] && [ -n "$(ip addr show dev lo scope global | grep " inet ")" ] \
			&& echo -n $IPV4 | xargs -d' ' -I{} ip addr del {}/32 dev lo
	[ "$IPV6" ] && [ -n "$(ip addr show dev lo scope global | grep " inet6 ")" ] \
			&& echo -n $IPV6 | xargs -d' ' -I{} ip addr del {}/128 dev lo

	return 0
}

stop () {
	del

	kill -STOP $(pgrep -f $SELF)
}

quit () {
	del

	exit 0
}

check () {
	# we only test the IPv4 side
	wget -q --no-proxy --timeout=2 --spider http://localhost:3128/squid-internal-static/icons/anthony-unknown.gif

	[ $? -eq 0 ] && add || del
}

go () {
	trap quit TERM
	trap stop TSTP

	while true; do
		check

		sleep 1
	done
}

SELF=$(basename "$0")
PROCS=$(pgrep -f "^/bin/sh $0\$")
RC=$?
if [ $RC -gt 0 ]; then
	echo "unexpected pgrep results (ret=$RC)" > /dev/stderr
	exit 70
fi
if [ "$PROCS" != "$$" ]; then
	echo "'$SELF' is already running" > /dev/stderr
	exit 69
fi

0<&- 1<&- 2<&- go &

exit 0