#!/usr/bin/env bash

setup_bridge() {
  if [[ $# -lt 1 ]]; then
    echo "usage: start_bridge internet_interface"
  else
    echo "Setting up bridge with internet adapter $1"
  fi
  ip link add name virbr0 type bridge
  ip link set virbr0 up
  ip addr add 192.168.100.0/24 dev virbr0

  sysctl -w net.ipv4.ip_forward=1
  nft add table inet nat
  nft add chain inet nat postrouting '{ type nat hook postrouting priority 100 ; }'
  nft add rule inet nat postrouting oifname $1 masquerade
}

del_bridge() {
  echo "Deleting virtual bridge"
  ip link del virbr0
  nft delete table inet nat
}

add_interface() {
  echo "Adding interface $1"
  ip tuntap add $1 mode tap
  ip link set $1 master virbr0
  ip link set $1 up
}

del_interface() {
  echo "Deleteing inteface $1"
  ip link set $1 down
  ip link set $1 nomaster
  ip tuntap del $1 mode tap
}

if [[ $UID -ne 0 ]]; then
  echo "Networking script must be run as root user"
  exit 1
fi

CASE=$1
shift
case $CASE in
  start_bridge)
    setup_bridge $@
    ;;
  stop_bridge)
    del_bridge $@
    ;;
  add_tap)
    add_interface $@
    ;;
  del_tap)
    del_interface $@
    ;;
  *)
    echo "usage:" $0 "[start_bridge|stop_bridge|add_tap|del_tap] [options]"
    ;;
esac