#!/bin/sh
# env
# Written in 2019 by Lucas
# CC0 1.0 Universal/Public domain - No rights reserved
#
# To the extent possible under law, the author(s) have dedicated all
# copyright and related and neighboring rights to this software to the
# public domain worldwide. This software is distributed without any
# warranty. You should have received a copy of the CC0 Public Domain
# Dedication along with this software. If not, see
# <http://creativecommons.org/publicdomain/zero/1.0/>.

usage() {
	cat - <<. >&2
Usage:
	${0##*/} attach TRUNK_DEV URNDIS_DEV
	${0##*/} detach TRUNK_DEV URNDIS_DEV
.
	exit 1
}

renew_dhcp_if_needed() {
	iface=$1
	hostname_if=/etc/hostname."$iface"
	[ ! -r "$hostname_if" ] && return
	while read -r line; do
		[ "$line" = dhcp ] && dhclient "$iface" && break
	done <"$hostname_if"
}

if [ $# -ne 3 ] || [ -z "$1" ] || [ -z "$2" ] || [ -z "$3" ]; then
	usage
fi
cmd=$1
trunk=$2
urndis=$3

case $cmd in
attach) ifconfig "$urndis" up
	ifconfig "$trunk" trunkport "$urndis"
	renew_dhcp_if_needed "$trunk"
	;;
detach)	# $urndis could be already removed
	ifconfig "$trunk" -trunkport "$urndis" 2>/dev/null || true
	renew_dhcp_if_needed "$trunk"
	;;
*)	usage
	;;
esac