source: freewrt/package/busybox/files/vlan.pre-up@ 9bb72d2

#!/bin/sh

case "$IFACE" in
        vlan0*)
                vconfig set_name_type VLAN_PLUS_VID
                VLANID=`echo $IFACE|sed "s/vlan0*//"`
                ;;
        vlan*)
                vconfig set_name_type VLAN_PLUS_VID_NO_PAD
                VLANID=`echo $IFACE|sed "s/vlan*//"`
                ;;
        eth*.0?*)
                vconfig set_name_type DEV_PLUS_VID
                VLANID=`echo $IFACE|sed "s/eth[0-9][0-9]*\.0*//g"`
                IF_VLAN_RAW_DEVICE=`echo $IFACE|sed "s/\(eth[0-9][0-9]*\)\..*/\1/"`
                ;;
        eth*.*)
                vconfig set_name_type DEV_PLUS_VID_NO_PAD
                VLANID=`echo $IFACE|sed "s/eth[0-9][0-9]*\.*//g"`
                IF_VLAN_RAW_DEVICE=`echo $IFACE|sed "s/\(eth[0-9][0-9]*\)\..*/\1/"`
                ;;
        *)      exit 0
                ;;
esac

if [ -n "$IF_VLAN_RAW_DEVICE" ]
then
        [ -x /sbin/vconfig ] || exit 0
        if ! grep -q "$IF_VLAN_RAW_DEVICE" /proc/net/dev
        then
                echo "$IF_VLAN_RAW_DEVICE does not exist, unable to create $IFACE"
                exit 1
        fi

        # enable vlan 
        if [ -d /proc/switch/$IF_VLAN_RAW_DEVICE ]
        then
                echo 1 > /proc/switch/$IF_VLAN_RAW_DEVICE/enable_vlan
        fi
        ip link set up dev $IF_VLAN_RAW_DEVICE
        vconfig add $IF_VLAN_RAW_DEVICE $VLANID
        # change mac link layer address
        if [ -n $IF_MAC_ADDRESS ]
        then
                ip link set $IF_VLAN_RAW_DEVICE.$VLANID address $IF_MAC_ADDRESS
        fi
        ip link set up dev $IF_VLAN_RAW_DEVICE.$VLANID

        # configure switch ports
        if [ -n "$IF_SWITCH_PORTS" ]
        then
                echo "$IF_SWITCH_PORTS" > /proc/switch/$IF_VLAN_RAW_DEVICE/vlan/$VLANID/ports
        fi
fi