#!/bin/bash
# Script creates bridge, tap  and adds tap and ethernet to the bridge


if [ "$1" == '2' ]; then
   br_ip='172.17.100.6/16'
   gw_ip='172.17.100.1'
   dns_ip='8.8.8.8'
   eth_int='enp4s0f2'
   br_int='br2'
   tap_int='tap2'
elif [ "$1" == '0' ]; then
   br_ip='192.168.0.3/24'
   gw_ip='none'
   dns_ip='8.8.8.8'
   eth_int='tap00'
   br_int='br0'
   tap_int='tap0'
else
   echo "Re-run the script with a bridge number either 0 or 2, e.g: '$0 0', exiting" && exit 1
fi

# Check if bridge and tap exist, if not create them
  for int in "$br_int" "$tap_int" "$eth_int"; do
     ifconfig "$int" &>/dev/null
     int_ret="$?"
     if [[ "$int_ret" != 0 && "$int" == "$br_int" ]]; then
        sudo ip link add "$int" type bridge
     elif [[ "$int_ret" != 0 && "$int" == "$tap_int" ]]; then
	sudo ip tuntap add dev "$int" mode tap user $(whoami)
     elif [[ "$int_ret" != 0 && "$int" == "eth_int" ]]; then
        echo "Sorry, I can't find Ethernet interface: '$eth_int', exiting" && exit 0
     fi

     # We need to bring every interface up and flush it 
     sudo ip link set dev "$int" up
     sudo ip addr flush dev "$int"

     # Add interface to "$br_int" if it isn't bridge. If it is bridge, assign IP address to bridge
     if [ "$int" != "$br_int" ]; then
       sudo ip link set "$int" master "$br_int" 
     elif [ "$int" == "$br_int" ]; then
       sudo ip addr add "$br_ip" dev "$br_int"
     fi
  done

  if [ "$gw_ip" != 'none' ]; then
     ip route show | grep -q "default via $gw_ip dev $br_int"
     [ "$?" != 0 ] && sudo ip route add default via "$gw_ip"
  fi

  # Configure Google DNS if we can't find it in /etc/resolv.conf
  grep -q "$dns_ip" /etc/resolv.conf
  [ "$?" != 0 ] && sudo bash -c "echo \"nameserver $dns_ip\" > /etc/resolv.conf"

 exit 0