#!/bin/bash -e
#
# tapdisk Xen block device hotplug script
#
# Author George Dunlap <george.dunlap@eu.citrix.com>
#
# Based on block-iscsi by Roger Pau Monné <roger.pau@citrix.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation; version 2.1 only. with the special
# exception on linking described in file LICENSE.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# Usage:
#
# Target should be specified using the following syntax:
#
# script=block-tap,vdev=xvda,target=<type>:<file>
#
# Type is either "aio" (for raw files), or "vhd"

dir=$(dirname "$0")
. "$dir/block-common.sh"

remove_label()
{
    echo $1 | sed "s/^\("$2"\)//"
}

check_tools()
{
    if ! command -v tap-ctl > /dev/null 2>&1; then
        fatal "Unable to find tap-ctl tool"
    fi
    modprobe blktap
    if ! tap-ctl check >& /dev/null ; then
	fatal "Blocktap kernel module not available"
    fi
}

# Sets the following global variables based on the params field passed in as
# a parameter: type file
parse_target()
{
    params=($(echo "$1" | tr ":" "\n"))

    type=${params[0]}
    file=${params[1]}
    if [ -z "$type" ] || [ -z "$file" ]; then
        fatal "Cannot parse required parameters"
    fi
}

# Sets $pid and $minor to point to the device associated with the target
find_device()
{
    local info
    local param

    if [ -z "$type" ] || [ -z "$file" ]; then
        fatal "required parameters not set"
    fi

    info=$(tap-ctl list -t $type -f $file)

    for param in $(echo "$info" | tr "," "\n")
    do
        case $param in
        pid=*)
            pid=$(remove_label $param "pid=")
            ;;
        minor=*)
            minor=$(remove_label $param "minor=")
            ;;
        esac
    done

    if [ -z "$pid" ] || [ -z "$minor" ]; then
        fatal "cannot find required parameters"
    fi
}

# Attaches the device and writes xenstore backend entries to connect
# the device
add()
{
    dev=$(tap-ctl create -a $target)
    write_dev $dev
}

# Disconnects the device
remove()
{
    find_device
    do_or_die tap-ctl destroy -p ${pid} -m ${minor} > /dev/null
}

command=$1
target=$(xenstore-read $XENBUS_PATH/params || true)
if [ -z "$target" ]; then
    fatal "No information about the target"
fi

parse_target "$target"

check_tools || exit 1

case $command in
add)
    add
    ;;
remove)
    remove
    ;;
*)
    exit 1
    ;;
esac