99-static.sh

#!/bin/bash

#
# Info:
#     Add static route on interface up.
#     Suitable for CentOS 7.
#     $DHCP4_ROUTERS is dispatcher environment variable.
#     Others can be found by switching DEBUG mode.
#
# Install:
#     ~# cp 99-static.sh /etc/NetworkManager/dispatcher.d/
#     ~# chmod +x /etc/NetworkManager/dispatcher.d/99-static.sh
#

set -euo pipefail

PATH=/bin:/usr/bin:/sbin
LOG='/var/log/nm_dispatcher.log'

INTERFACE=$1
STATUS=$2
DST_HOST="8.8.8.8"
GW="${DHCP4_ROUTERS%% *}"  # get first gateway

DEBUG="false"

if [[ "$DEBUG" == "true" ]]; then
	set -x  # debug mode

	echo "================" > /tmp/variables.txt
	echo "Environment Variables" >> /tmp/variables.txt
	printenv >> /tmp/variables.txt
	echo "===============" >> /tmp/variables.txt
	echo "Shell Variables" >> /tmp/variables.txt
	set >> /tmp/variables.txt

	echo "[$(date +"%F %T")] Called with ($*)" >> ${LOG}
fi

[[ "$INTERFACE" == "eth0" ]] || exit

if [[ "$STATUS" == "up" ]]; then
	ip route add $DST_HOST via $GW dev "$INTERFACE"
fi

if [[ "$STATUS" == "down" ]]; then
	ip route del $DST_HOST
fi