Add/Remove null routes with permanent configuration (FreeBSD)

nullroute.sh

#!/bin/sh
#
# Copyright (c) 2015 Babak Farrokhi.  All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# this script nullroutes a give CIDR
#
#

ROUTE="/sbin/route"
NETSTAT="/usr/bin/netstat"
GREP="/usr/bin/grep"
AWK="/usr/bin/awk"
CFG="/usr/local/etc/nullroute.conf"

nullroute() {
	local ADDR=${1}; shift;

	${ROUTE} add -net ${ADDR} 127.0.0.1 -blackhole
}

delroute() {
	local ADDR=${1}; shift;
	
	${ROUTE} delete ${ADDR}
}

showroute() {
	${NETSTAT} -rn | ${GREP} "SB " | ${AWK} '{print $1}'
}

loadroutes() {
	if [ ! -f ${CFG} ]; then
		echo "Cannot open ${CFG}"
		exit 1
	fi
	
	for R in `cat ${CFG} | ${GREP} -E -v '^[[:space:]]*$'`; do
		nullroute ${R}	
	done
}

saveroutes() {
	showroute > ${CFG} && echo "configuration saved to ${CFG}"
}

flush() {
	for R in `${NETSTAT} -rn | ${GREP} "SB " | ${AWK} '{print $1}'`; do
		delroute ${R}
	done	
}

help() {
	echo "$0 [ add <host> | del <host> | show | load | save | flush ]"
}

if [ $# -lt 1 ]; then
	help
	exit 1
fi

case ${1} in
	add)
		if [ x${2} == x ]; then
			help
			exit 1
		fi
		nullroute ${2}
		;;
	del)
		if [ x${2} == x ]; then
			help
			exit 1
		fi
		delroute ${2}
		;;
	show)
		showroute
		;;
	load)
		loadroutes
		;;
	save)
		saveroutes
		;;
	flush)
		flush
		;;
	*)
		help
		;;
esac