#!/bin/sh
set -eu

# guessing parameters
case "$IFACE" in
	*#*) exit 0 ;;
	*:*) exit 0 ;;
	vlan*.*) exit 0 ;;
	vlan*) GUESSED_VLAN_ID="${IFACE#vlan}" ;;
	*.*)
		GUESSED_RAW_DEVICE="${IFACE%.*}"
		GUESSED_VLAN_ID="${IFACE##*.}"
		;;
	*) [ -n "${IF_VLAN_ID:-}" -o -n "${IF_VLAN_RAW_DEVICE:-}" ] || exit 0 ;;
esac

RAW_DEVICE="${IF_VLAN_RAW_DEVICE:-${GUESSED_RAW_DEVICE:-}}"
VLAN_ID="$(expr ${IF_VLAN_ID:-${GUESSED_VLAN_ID:-0}} + 0 || :)"

if ! [ "$VLAN_ID" -gt 0 ]; then
	echo "VLAN_ID for $IFACE is not set"
	exit 1
fi

if [ -z "$RAW_DEVICE" ]; then
	echo "RAW_DEVICE for $IFACE is not set"
	exit 1
fi

if ! ip link show "$RAW_DEVICE" >/dev/null; then
	echo "Device $RAW_DEVICE for $IFACE does not exist"
	exit 1
fi

if ! [ -d /proc/net/vlan ]; then
	modprobe 8021q
fi

if ! [ -e /sys/class/net/$IFACE ]; then
	ip link set dev "$RAW_DEVICE" up
	ip link add link "$RAW_DEVICE" name "$IFACE" type vlan id "$VLAN_ID"
fi

if ! ip link show "$IFACE" >/dev/null; then
	echo "Failed to create vlan device $IFACE on device $RAW_DEVICE with tag $VLAN_ID"
	exit 1
fi
