#!/bin/bash
#
# Create a "bank" of tap network devices that can be used by the
# runqemu script. This script needs to be run as root, and will
# use the tunctl binary from the build system sysroot. Note: many Linux 
# distros these days still use an older version of tunctl which does not
# support the group permissions option, hence the need to use the build
# system provided version.
#
# Copyright (C) 2010 Intel Corp.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

usage() {
	echo "Usage: sudo $0 <uid> <gid> <num> <native-sysroot-basedir>"
        echo "Where <uid> is the numeric user id the tap devices will be owned by"
	echo "Where <gid> is the numeric group id the tap devices will be owned by"
	echo "<num> is the number of tap devices to create (0 to remove all)"
	echo "<native-sysroot-basedir> is the path to the build system's native sysroot"
	exit 1
}

if [ $EUID -ne 0 ]; then
	echo "Error: This script must be run with root privileges"
	exit
fi

if [ $# -ne 4 ]; then
	echo "Error: Incorrect number of arguments"
	usage
fi

TUID=$1
GID=$2
COUNT=$3
SYSROOT=$4

TUNCTL=$SYSROOT/usr/bin/tunctl
if [[ ! -x "$TUNCTL" || -d "$TUNCTL" ]]; then
	echo "Error: $TUNCTL is not an executable"
	usage
fi

SCRIPT_DIR=`dirname $0`
RUNQEMU_IFUP="$SCRIPT_DIR/runqemu-ifup"
if [ ! -x "$RUNQEMU_IFUP" ]; then
	echo "Error: Unable to find the runqemu-ifup script in $SCRIPT_DIR"
	exit 1
fi

IFCONFIG=`which ifconfig 2> /dev/null`
if [ -z "$IFCONFIG" ]; then
	# Is it ever anywhere else?
	IFCONFIG=/sbin/ifconfig
fi
if [ ! -x "$IFCONFIG" ]; then
       echo "$IFCONFIG cannot be executed"
       exit 1
fi

# Ensure we start with a clean slate
for tap in `$IFCONFIG | grep ^tap | awk '{ print \$1 }' | sed s/://`; do
	echo "Note: Destroying pre-existing tap interface $tap..."
	$TUNCTL -d $tap
done

echo "Creating $COUNT tap devices for UID: $TUID GID: $GID..."
for ((index=0; index < $COUNT; index++)); do
	echo "Creating tap$index"
	ifup=`$RUNQEMU_IFUP $TUID $GID $SYSROOT 2>&1`
	if [ $? -ne 0 ]; then
		echo "Error running tunctl: $ifup"
		exit 1
	fi
done

# The runqemu script will check for this file, and if it exists,
# will use the existing bank of tap devices without creating
# additional ones via sudo.
touch /etc/runqemu-nosudo