#!/bin/bash
# Generate interface files for a common topology
#

# Default values
topname="lan"
topnum="100"
numhosts=1
numrouters=0
outdir="./"

# Read input parameters
while [ "$1" != "" ]; do
        case $1 in
                -l | --lefthosts )   shift;
                                lefthosts=$1;
                                ;;
                -r | --righthosts )  shift;
                                righthosts=$1;
                                ;;
                -R | --routers )  shift;
                                routers=$1;
                                ;;
                -n | --number )  shift;
                                topnum=$1;
                                ;;
                -o | --out )    shift;
                                outdir=$1;
                                ;;
                * )             usage
                                exit 1
        esac
        shift
done

# Topology parameters
numnetworks=$(( ${routers} + 1));
totalnodes=$(( ${lefthosts} + ${routers} + ${righthosts} ));
firstrouter=$(( ${lefthosts} + 1 ));
lastrouter=$(( ${lefthosts} + ${routers} ));
netnumber=1

# Address structure
# Ip addresses are split into parts:
# commonnetwork - subnet - hostbase - hostspecific
# where
# commonnetwork is the same for all networks, e.g. 192.168.
commonnetwork="192.168."
# subnet is an integer, incremented for each subnet
subnet=1
# hostbase is 1 for left hosts
lefthostbase=1
# and 2 or higher for right hosts
righthostbase=2
# hostspecific is an integer, increment for each host in the subnet
hostspecific=1
#
# The result is address such as:
# lefthosts: 192.168.1.11, 192.168.1.12, 192.168.1.13, ... , 192.168.1.20, ...
# righthosts: 192.168.x.21, 192.168.x.22, 192.168.x.23, ..., 192.168.x.30, ...
# router1: 192.168.1.1, 192.168.2.1
# router2: 192.168.2.2, 192.168.3.2
# router3: 192.168.3.3, 192.168.4.3
# routerN: 192.168.N.N, 192.168.(N+1).N
# Other addresses used:
netmask="255.255.255.0"
defaultnetwork="${commonnetwork}0.0"
defaultnetmask="255.255.0.0"

# Check the limits 
# Currently there is a limit on the number of networks/routers supported
# since the router addressing scheme will overlap with host addressing 
# scheme in the right network. This is limited by righthostbase. 
# To lift this limit, increase righthostbase parameter above.
limitrouters=$(( ${righthostbase} * 10 - 1 ));
if [ ${routers} -gt ${limitrouters} ];
then
    echo "vn: The number of routers you selected (${routers}) creates"
    echo "vn: too many networks such that there will be a conflict"
    echo "vn: in addresses assigned to hosts and routers. The"
    echo "vn: current limit is ${limitrouters}. Either reduce the"
    echo "vn: number of routers, or modify this script and increase"
    echo "vn: righthostbase."
    echo "vn: Error. Address conflict due to too many routers. Exiting."
    exit 1
fi


# Currently there is a limit on the number of networks/routers supported
# since networks are named a, b, c, d, ... .
# To lift this limit, need to modify the naming scheme, e.g. a, b, ... z, aa, ab, ...
limitnetworks=26
if [ ${numnetworks} -gt ${limitnetworks} ];
then
    echo "vn: The number of routers you selected (${routers}) creates"
    echo "vn: more than the supported number of networks (${limitnetworks})."
    echo "vn: Please try again with less routers (or change this script"
    echo "vn: to support more networks)".
    echo "vn: Error. Too many routers. Exiting."
    exit 1
fi


# Create the interfaces for each node
for (( node=1; node<=${totalnodes}; node++ ));
do
    
	# Node number in text format
	noden=${node}
	if [ ${noden} -lt 10 ];
	then
		noden="0${noden}";
	fi

	# Name of interface file
	nodeiffile="${outdir}/interfaces-topology-${topnum}-node-${noden}"

	# IP addresses
	# Left hosts
	if [ ${node} -lt ${firstrouter} ];
	then
	    nodetype="host"
	    hostaddress=$(( ${lefthostbase} * 10 + ${node} ));
	    ipaddress="${commonnetwork}${subnet}.${hostaddress}";
	    netaddress="${commonnetwork}${subnet}.0"
	    bcaddress="${commonnetwork}${subnet}.255"
	    defaultrouter="${commonnetwork}${subnet}.1"
	# Right hosts
	elif [ ${node} -gt ${lastrouter} ];
	then
	    nodetype="host"
	    hostaddress=$(( ${righthostbase} * 10 + ${node} - ${lefthosts} - ${routers} ));
	    ipaddress="${commonnetwork}${subnet}.${hostaddress}";
	    routerhostportion=$(( ${subnet} - 1 ));
	    defaultrouter="${commonnetwork}${subnet}.${routerhostportion}"
	# Routers
	else
	    nodetype="router"
	    routernum=$(( ${node} - ${lefthosts} ));
	    ipaddress="${commonnetwork}${subnet}.${routernum}"
	    subnet2=$(( ${subnet} + 1 ));
	    ipaddress2="${commonnetwork}${subnet2}.${routernum}"
            netaddress2="${commonnetwork}${subnet2}.0"
	    bcaddress2="${commonnetwork}${subnet2}.255"
	fi
        netaddress="${commonnetwork}${subnet}.0"
	bcaddress="${commonnetwork}${subnet}.255"

echo "${node} ${firstrouter} ${lastrouter} ${nodetype}"
	# Convert subnet number into name, e.g. "1" to "neta"
	subnetnum=$(( ${subnet} + 96 ));
	subnetletter=`printf "\x$(printf %x $subnetnum)"`;
	vboxnet="net${subnetletter}"
	if [ "${nodetype}" = "router" ];
	then
	    subnet2num=$(( ${subnet2} + 96 ));
	    subnet2letter=`printf "\x$(printf %x $subnet2num)"`;
	    vboxnet2="net${subnet2letter}"
	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}

	# Host node
	if [ "${nodetype}" = "host" ];
	then
		echo -e "\tpost-up route add -net ${defaultnetwork} netmask ${defaultnetmask} gw ${defaultrouter} dev eth1" >> ${nodeiffile}
		echo -e "\tpre-down route del -net ${defaultnetwork} netmask ${defaultnetmask} gw ${defaultrouter} dev eth1" >> ${nodeiffile}
	# Router node
	else
	    # In a chain such as:
	    # H1 - R1 - R2 - R3 - R4 - R5 - H2
	    # we will treat R1, R2 and R3 as left side routers, and R4 and R5 as right side
	    # Left side routers will have:
	    # - default route to rest of network on eth2 (right side of router)
	    # - specific routes to subnets on left of it on eth1
	    # Note that we don't need to add specific routes for directly attached networks
	    # as they are automatically created when the interface is brought up.
	    # For example R2 will have:
	    # - default route to 192.168.0.0 to gw R3 on eth2
	    # - specific router to 192.168.1.0 (H1-R1) to gw R1 on eth1
	    # Similar applies for right side routers, but in the opposite direction:
	    # - default route to rest of network on eth1 (left side of router)
	    # - specific routes to subnets on right of it on eth2

		firstrouternum=1
		midrouternum=$(( (${routers} + 1) / 2 ));
		lastrouternum=${routers}
		# Left side routers
		if [ ${routernum} -le ${midrouternum} ];
		then
		    # Add 'numsr' specific routes on 1st interface
		    numsr=$(( ${routernum} - ${firstrouternum} ));
		    for (( sr=1; sr<=${numsr}; sr++ ));
		    do
			destnetwork="${commonnetwork}${sr}.0"
			destmask=${netmask}
			destgw="${commonnetwork}${subnet}.$(( ${subnet} - 1 ))"
			destif="eth1"
			echo -e "\tpost-up route add -net ${destnetwork} netmask ${destmask} gw ${destgw} dev ${destif}" >> ${nodeiffile}
			echo -e "\tpre-down route add -net ${destnetwork} netmask ${destmask} gw ${destgw} dev ${destif}" >> ${nodeiffile}
		    done

	            # Create 2nd interface on router
		    echo " " >> ${nodeiffile}
		    echo "# VBoxNetwork: ${vboxnet2}" >> ${nodeiffile}
		    echo "auto eth2" >> ${nodeiffile}
		    echo "iface eth2 inet static" >> ${nodeiffile}
		    echo -e "\taddress ${ipaddress2}" >> ${nodeiffile}
		    echo -e "\tnetmask ${netmask}" >> ${nodeiffile}
		    echo -e "\tnetwork ${netaddress2}" >> ${nodeiffile}
		    echo -e "\tbroadcast ${bcaddress2}" >> ${nodeiffile}

		    # Add default route on 2nd interface
		    if [ ${routers} -gt 1 ];
		    then
			defaultgw="${commonnetwork}$(( ${subnet} + 1 )).$(( ${subnet} + 1 ))";
			defaultif="eth2"
			echo -e "\tpost-up route add -net ${defaultnetwork} netmask ${defaultnetmask} gw ${defaultgw} dev ${defaultif}" >> ${nodeiffile}
			echo -e "\tpre-down route add -net ${defaultnetwork} netmask ${defaultnetmask} gw ${defaultgw} dev ${defaultif}" >> ${nodeiffile}
			
		    fi

		# Right side routers
		else
		    # Add default route on 1st interface
		    defaultgw="${commonnetwork}${subnet}.$(( ${subnet} - 1 ))";
		    defaultif="eth1"
		    echo -e "\tpost-up route add -net ${defaultnetwork} netmask ${defaultnetmask} gw ${defaultgw} dev ${defaultif}" >> ${nodeiffile}
		    echo -e "\tpre-down route add -net ${defaultnetwork} netmask ${defaultnetmask} gw ${defaultgw} dev ${defaultif}" >> ${nodeiffile}
			
	            # Create 2nd interface on router
		    echo " " >> ${nodeiffile}
		    echo "# VBoxNetwork: ${vboxnet2}" >> ${nodeiffile}
		    echo "auto eth2" >> ${nodeiffile}
		    echo "iface eth2 inet static" >> ${nodeiffile}
		    echo -e "\taddress ${ipaddress2}" >> ${nodeiffile}
		    echo -e "\tnetmask ${netmask}" >> ${nodeiffile}
		    echo -e "\tnetwork ${netaddress2}" >> ${nodeiffile}
		    echo -e "\tbroadcast ${bcaddress2}" >> ${nodeiffile}

		    # Add 'numsr' specific routes on 2nd interface
		    numsr=$(( ${lastrouternum} - ${routernum} ));
		    for (( sr=${numsr}; sr>=1; sr-- ));
		    do
			destnetwork="${commonnetwork}$(( ${subnet} + 1 + ${sr} )).0"
			destmask=${netmask}
			destgw="${commonnetwork}$(( ${subnet} + 1 )).$(( ${subnet} + 1 ))"
			destif="eth1"
			echo -e "\tpost-up route add -net ${destnetwork} netmask ${destmask} gw ${destgw} dev ${destif}" >> ${nodeiffile}
			echo -e "\tpre-down route add -net ${destnetwork} netmask ${destmask} gw ${destgw} dev ${destif}" >> ${nodeiffile}
		    done

		fi
	fi

	# Increment subnet if necessary
	if [ "${nodetype}" = "router" ];
	then
	    subnet=$(( ${subnet} + 1 ));
	fi
done