#!/bin/bash
#
# QEMU network interface configuration script. This utility needs to
# be run as root, and will use the tunctl binary from a Poky 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 Poky's version.
#
# If this script is being run standalone in order to set up a bank of tap
# devices for later qemu use, then a group id must be the first argument.
# The resulting tap device will be group-owned by this group, and qemu
# users must be members of this group.
#
# If the kernel is too old to support TUNSETGROUP, then a user must be passed
# in as the second argument, the tap device will be owned by that user, and
# only that user will be able to use it.
#
# Copyright (c) 2006-2010 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 "$0 <gid> {uid} <native-sysroot-basedir>"
	echo "Where uid is *only* included if this script complains when it's missing"
}

if [[ $# -lt 2 || $# -gt 3 ]]; then
	usage
	exit 1
fi

USER=""
GROUP="-g $1"
if [ $# -eq 2 ]; then
	NATIVE_SYSROOT_DIR=$2
else
	USER=$2
	NATIVE_SYSROOT_DIR=$3
fi

TUNCTL=$NATIVE_SYSROOT_DIR/usr/bin/tunctl
if [ ! -e "$TUNCTL" ]; then
	echo "Error: Unable to find tunctl binary in '$NATIVE_SYSROOT_DIR/usr/bin'"

	if [[ "$NATIVE_SYSROOT_DIR" =~ ^\/opt\/poky ]]; then
		echo "This shouldn't happen - something is wrong with your toolchain installation"
	else
		echo "Have you run 'bitbake qemu-helper-native'?"
	fi
	
	exit 1
fi

TAP=`$TUNCTL -b $GROUP 2>&1`
STATUS=$?
if [[ "$TAP" =~ "TUNSETGROUP" ]]; then
	# TUNSETGROUP failed because of permissions or the kernel being too old
	# Retry, falling back to a specific user
	if [ "$USER" = "" ]; then
	echo "TUNSETGROUP failed - add a username to the command line in order"
	echo "to have the tap device owned by that user"
	exit 1
	fi
	TAP=`$TUNCTL -b -u $USER 2>&1`
	STATUS=$?
	# Force this to appear on stderr in order that the user sees it if this
	# is running from poky-qemu-internal and in order to avoid having this
	# output confuse it.
	echo "Only user $USER will be able to use $TAP - upgrade the kernel to " 1>&2
	echo "2.6.23 or later in order to allow group access to tap devices" 1>&2
fi
if [ $STATUS -ne 0 ]; then
	echo "tunctl failed:"
	echo $TAP
	exit 1
fi

IFCONFIG=`which ifconfig`
if [ "x$IFCONFIG" = "x" ]; then
	# better than nothing...
	IFCONFIG=/sbin/ifconfig
fi

n=$[ `echo $TAP | sed 's/tap//'` + 1 ]
$IFCONFIG $TAP 192.168.7.$n

# setup NAT for tap0 interface to have internet access in QEMU
IPTABLES=`which iptables`
if [ "x$IPTABLES" = "x" ]; then
	IPTABLES=/sbin/iptables
fi

$IPTABLES -A POSTROUTING -t nat -j MASQUERADE -s 192.168.7.0/24
echo 1 > /proc/sys/net/ipv4/ip_forward
$IPTABLES -P FORWARD ACCEPT

echo $TAP
