#!/bin/bash
# Generate interface files for a common topology
#
# Example usage:
#    vn-generateinterfaces --topology cs --hosts 10
# creates a client/server topology with 10 clients, 1 router and 1 server
#
#    vn-generateinterfaces --topology dumbbell --hosts 5
# creates a dumbbell topology with 5 hosts, 1 router, 5 hosts
#
# Assumptions:
#
# Topologies:
#   lan: n hosts
#   cs: n hosts --- 1 router --- 1 server
#   dumbbell: n hosts --- 1 router --- n hosts

# Default values
topname="lan"
topnum="99"
numhosts=1
outdir="./"

# Script parameters
# Base IP addresses for each subnet
# Currently only 2 subnets supported and must be /24
# Assumes roouter interfaces are both .1
neta_networkbase="192.168.1."
neta_hostbase=10
netb_networkbase="192.168.2."
netb_hostbase=20
netmask="255.255.255.0"

# Read input parameters
while [ "$1" != "" ]; do
        case $1 in
                -t | --topology )   shift;
                                topname=$1;
                                ;;
                -h | --hosts )  shift;
                                numhosts=$1;
                                ;;
                -n | --number )  shift;
                                topnum=$1;
                                ;;
                -o | --out )    shift;
                                outdir=$1;
                                ;;
                * )             usage
                                exit 1
        esac
        shift
done

# Node number for router

# Client server
if [ "${topname}" = "cs" ];
then
	nodemax=$(( ${numhosts} + 2 ));
	routernode=$(( ${numhosts} + 1 ));
# Dumbbell
elif [ "${topname}" = "dumbbell" ];
then
	nodemax=$(( ${numhosts} * 2  + 1 ));
	routernode=$(( ${numhosts} + 1 ));
# LAN
else
	nodemax=${numhosts};
	routernode=0; # No router
fi

side="left"
netaddress="${neta_networkbase}0"
bcaddress="${neta_networkbase}255"
hostbase=${neta_hostbase};
networkbase=${neta_networkbase}
vboxnet="neta"
# Create left and right side nodes
for (( node=1; node<=${nodemax}; node++ ));
do
	noden=${node}
	if [ ${noden} -lt 10 ];
	then
		noden="0${noden}";
	fi
	nodeiffile="${outdir}/interfaces-topology-${topnum}-node-${noden}"

	iphostaddr=$(( ${hostbase} + ${node} ));
	ipaddress="${networkbase}${iphostaddr}"

	if [ ${node} -eq ${routernode} ];
	then
		ipaddress="${neta_networkbase}1"
	fi

	echo "# Interface file auto-generated by vn-generateinterfaces" > ${nodeiffile}
	echo "auto lo" >> ${nodeiffile}
	echo "iface lo inet loopback" >> ${nodeiffile}
	echo " " >> ${nodeiffile}
	echo "auto eth0" >> ${nodeiffile}
	echo "iface eth0 inet dhcp" >> ${nodeiffile}
	echo " " >> ${nodeiffile}
	echo "# VBoxNetwork: ${vboxnet}" >> ${nodeiffile}
	echo "auto eth1" >> ${nodeiffile}
	echo "iface eth1 inet static" >> ${nodeiffile}
	echo -e "\taddress ${ipaddress}" >> ${nodeiffile}
	echo -e "\tnetmask ${netmask}" >> ${nodeiffile}
	echo -e "\tnetwork ${netaddress}" >> ${nodeiffile}
	echo -e "\tbroadcast ${bcaddress}" >> ${nodeiffile}
	# Router node
	if [ ${node} -eq ${routernode} ];
	then
		netaddress="${netb_networkbase}0"
		bcaddress="${netb_networkbase}255"
		hostbase=$(( ${netb_hostbase} - ${numhosts} - 1 ));
		networkbase=${netb_networkbase}
		vboxnet="netb"
		ipaddress="${netb_networkbase}1"
		side="right"
		echo " " >> ${nodeiffile}
		echo "# VBoxNetwork: ${vboxnet}" >> ${nodeiffile}
		echo "auto eth2" >> ${nodeiffile}
		echo "iface eth2 inet static" >> ${nodeiffile}
		echo -e "\taddress ${ipaddress}" >> ${nodeiffile}
		echo -e "\tnetmask ${netmask}" >> ${nodeiffile}
		echo -e "\tnetwork ${netaddress}" >> ${nodeiffile}
		echo -e "\tbroadcast ${bcaddress}" >> ${nodeiffile}
	else
		echo -e "\tpost-up route add -net 192.168.0.0 netmask 255.255.0.0 gw ${networkbase}1 dev eth1" >> ${nodeiffile}
		echo -e "\tpre-down route del -net 192.168.0.0 netmask 255.255.0.0 gw ${networkbase}1 dev eth1" >> ${nodeiffile}
	fi
done