#!/bin/bash
#
# QEMU network interface configuration script. This utility needs to
# be run as root, and will use the ip utility
#
# If you find yourself calling this script a lot, you can add the
# the following to your /etc/sudoers file to be able to run this
# command without entering your password each time:
#
# <my-username> ALL=NOPASSWD: /path/to/runqemu-ifup
# <my-username> ALL=NOPASSWD: /path/to/runqemu-ifdown
#
# If you'd like to create a bank of tap devices at once, you should use
# the runqemu-gen-tapdevs script instead. If tap devices are set up using
# that script, the runqemu script will never end up calling this
# script.
#
# Copyright (c) 2006-2011 Linux Foundation
#
# SPDX-License-Identifier: GPL-2.0-only
#

usage() {
	echo "sudo $(basename $0) <gid>"
}

if [ $EUID -ne 0 ]; then
	echo "Error: This script (runqemu-ifup) must be run with root privileges"
	exit 1
fi

if [ $# -eq 2 ]; then
	echo "Warning: uid parameter is ignored. It is no longer needed." >&2
	GROUP="$2"
elif [ $# -eq 1 ]; then
	GROUP="$1"
else
	usage
	exit 1
fi


if [ -z "$OE_TAP_NAME" ]; then
	OE_TAP_NAME=tap
fi

if taps=$(ip tuntap list 2>/dev/null); then
	tap_no_last=$(echo "$taps" |cut -f 1 -d ":" |grep -E "^$OE_TAP_NAME.*" |sed "s/$OE_TAP_NAME//g" | sort -rn | head -n 1)
	if [ -z "$tap_no_last" ]; then
		tap_no=0
	else
		tap_no=$(("$tap_no_last" + 1))
	fi
	ip tuntap add "$OE_TAP_NAME$tap_no" mode tap group "$GROUP" && TAP=$OE_TAP_NAME$tap_no
fi

if [ -z "$TAP" ]; then
	echo "Error: Unable to find a tap device to use"
	exit 1
fi

IPTOOL=`which ip 2> /dev/null`
if [ "x$IPTOOL" = "x" ]; then
	# better than nothing...
	IPTOOL=/sbin/ip
fi
if [ ! -x "$IPTOOL" ]; then
	echo "$IPTOOL cannot be executed"
	exit 1
fi

IPTABLES=`which iptables 2> /dev/null`
if [ "x$IPTABLES" = "x" ]; then
	IPTABLES=/sbin/iptables
fi
if [ ! -x "$IPTABLES" ]; then
	echo "$IPTABLES cannot be executed"
	exit 1
fi

n=$[ (`echo $TAP | sed "s/$OE_TAP_NAME//"` * 2) + 1 ]
$IPTOOL addr add 192.168.7.$n/32 broadcast 192.168.7.255 dev $TAP
STATUS=$?
if [ $STATUS -ne 0 ]; then
    echo "Failed to set up IP addressing on $TAP"
    exit 1
fi
$IPTOOL link set dev $TAP up
STATUS=$?
if [ $STATUS -ne 0 ]; then
    echo "Failed to bring up $TAP"
    exit 1
fi

dest=$[ (`echo $TAP | sed "s/$OE_TAP_NAME//"` * 2) + 2 ]
$IPTOOL route add to 192.168.7.$dest dev $TAP
STATUS=$?
if [ $STATUS -ne 0 ]; then
    echo "Failed to add route to 192.168.7.$dest using $TAP"
    exit 1
fi

# setup NAT for tap0 interface to have internet access in QEMU
$IPTABLES -A POSTROUTING -t nat -j MASQUERADE -s 192.168.7.$n/32
$IPTABLES -A POSTROUTING -t nat -j MASQUERADE -s 192.168.7.$dest/32
echo 1 > /proc/sys/net/ipv4/ip_forward
echo 1 > /proc/sys/net/ipv4/conf/$TAP/proxy_arp
$IPTABLES -P FORWARD ACCEPT

echo $TAP