#!/bin/bash

#
# Create/delete macvtap interfaces
#

usage () {
    echo -e "Usage:\t$0 -m <MAC ADDRESS> -i <INTERFACE> [ -u <OWNER> ]"
    echo -e "\t\t-d -m <MAC ADDRESS>"
    echo -e "\t\t-d -t <DEVINDEX>"
    exit 1
}

justincasedel () {
    local tname=$1
    [ -z "$tname" ] && exit 1
    ip link del dev $tname 2>&1 >/dev/null
    exit 15
}

createmacvtap () {
    local iface=$1
    local macaddr=$2
    local tname=$( echo "$(date)$$" | md5sum )
    tname="vm${tname:0:6}"

    [ -z "$iface" -o -z "$macaddr" ] && exit 10
    [[ "$macaddr" =~ ^([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}$ ]] || exit 11
    ip link add link $iface name $tname type macvtap
    [ $? -ne 0 ] && justincasedel $tname
    ip link set addr $macaddr dev $tname
    [ $? -ne 0 ] && justincasedel $tname
    ip link set up dev $tname 
    [ $? -ne 0 ] && justincasedel $tname
    echo $tname
}

deletemacvtap () {
    local tname=$1
    [ -z "$tname" ] && exit 10
    ip link del dev $tname
    [ $? -ne 0 ] && exit 15
    return 0
}

getindexbyname () {
    local tname=$1
    [ -z "$tname" ] && exit 20
    ip link show | grep $tname | sed "s/^\([0-9]*\): $tname.*/\1/"
}

getnamebyindex () {
    local tidx=$1
    [ -z "$tidx" ] && exit 20
    ip link show | grep -e "^$tidx:" | sed "s/^$tidx: \(.\{1,8\}\)@.*/\1/"
}

getnamebyaddr () {
    local macaddr=$1
    [[ "$macaddr" =~ ^([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}$ ]] || exit 20
    ip li sh | grep -B1 $macaddr | head -n1 | sed "s/^[0-9]*: \(.\{1,8\}\)@.*/\1/"
}

chowndev () {
    local tidx=$1 
    local user=$2
    [ -z "$tidx" -o -z "$user" ] && exit 20
    sleep 1
    chown $user /dev/tap$tidx
#    for i in {1..5}; do
#      [ -n "$( find /dev -user $user -name tap$tidx )" ] && break
#      chown $user /dev/tap$tidx
#      sleep 1
#    done
}

[ $# -eq 0 ] && usage

# parse options
while getopts ":dm:i:u:t:" opt; do
  case $opt in
    d)
      delmacvtap=1
      ;;
    m)
      macaddr="$OPTARG"
      ;;
    i)
      iface="$OPTARG"
      ;;
    u)
      owner="$OPTARG"
      ;;
    t)
      devindex="$OPTARG"
      ;;
    \?)
      usage
      ;;
    :)
      echo "Option -$OPTARG requires an argument." >&2
      usage
      ;;
  esac
done

# request processing
if [ "x$delmacvtap" = "x1" ]; then 
    if [ -n "$devindex" ]; then
        devname=$( getnamebyindex "$devindex" ) || exit $?
    elif [ -n "$macaddr" ]; then 
        devname=$( getnamebyaddr "$macaddr" ) || exit $?
    else
        exit 30
    fi
    deletemacvtap "$devname"
else
    devname=$( createmacvtap "$iface" "$macaddr" ) || exit $?
    devidx=$( getindexbyname "$devname" ) || exit $?
    [ -n "$owner" ] && chowndev "$devidx" "$owner"
    echo "/dev/tap$devidx"
fi