#!/bin/sh
#
# Parses DHCP options from openvpn to update resolv.conf
# To use set as 'up' and 'down' script in your openvpn *.conf:
# up /etc/openvpn/update-resolv-conf
# down /etc/openvpn/update-resolv-conf
#
# Used snippets of resolvconf script by Thomas Hood <jdthood@yahoo.co.uk>
# and Chris Hanson
# Licensed under the GNU GPL.	See /usr/share/common-licenses/GPL.
# 07/2013 colin@daedrum.net Fixed intet name
# 05/2006 chlauber@bnc.ch
#
# Example envs set from openvpn:
# foreign_option_1='dhcp-option DNS 193.43.27.132'
# foreign_option_2='dhcp-option DNS 193.43.27.133'
# foreign_option_3='dhcp-option DOMAIN be.bnc.ch'
# foreign_option_4='dhcp-option DOMAIN-SEARCH bnc.local'

## The 'type' builtins will look for file in $PATH variable, so we set the
## PATH below. You might need to directly set the path to 'resolvconf'
## manually if it still doesn't work, i.e.
## RESOLVCONF=/usr/sbin/resolvconf
## export PATH=$PATH:/sbin:/usr/sbin:/bin:/usr/bin
## RESOLVCONF=$(type -p resolvconf)
RESOLVCONF=/tmp/resolv.conf.d/resolv.conf.ovpn

case $script_type in

up)
	temp_file=$(mktemp)
	env | grep '^foreign_option_' | while IFS='=' read -r name value; do echo "$value"; done > "$temp_file"
	while IFS= read -r option; do
		part1=$(echo "$option" | cut -d " " -f 1)
		if [ "$part1" == "dhcp-option" ] ; then
			part2=$(echo "$option" | cut -d " " -f 2)
			part3=$(echo "$option" | cut -d " " -f 3)
			if [ "$part2" == "DNS" ] ; then
				IF_DNS_NAMESERVERS="$IF_DNS_NAMESERVERS $part3"
			fi
			if [[ "$part2" == "DOMAIN" || "$part2" == "DOMAIN-SEARCH" ]] ; then
				IF_DNS_SEARCH="$IF_DNS_SEARCH $part3"
			fi
		fi
	done < "$temp_file"
	rm "$temp_file"
	R=""
	if [ "$IF_DNS_SEARCH" ]; then
		R="search "
		for DS in $IF_DNS_SEARCH ; do
			R="${R} $DS"
		done
	R="${R}
"
	fi

	for NS in $IF_DNS_NAMESERVERS ; do
		R="${R}nameserver $NS
"
	done

	[ -n "$R" ] || R="nameserver 1.1.1.1"
	echo "$R" > $RESOLVCONF
	;;
down)
	[ -e $RESOLVCONF ] && {
		rm -f $RESOLVCONF
	}
	;;
esac

# Workaround / jm@epiclabs.io 
# force exit with no errors. Due to an apparent conflict with the Network Manager
# $RESOLVCONF sometimes exits with error code 6 even though it has performed the
# action correctly and OpenVPN shuts down.
exit 0
