#!/bin/sh -e
#
# ip-dhcp-host.sh - add or remove a mac address --> ipv4 mapping

action="$1"
network_name="$2"
mac_address="$3"
ipv4_address="$4"

[ "$action" != 'add' ] && [ "$action" != 'delete' ] && printf 'you must set $action to either add or delete (1st arg)\n' && exit 1
[ "$network_name" = '' ] && printf 'you must set $network_name (2nd arg)\n' && exit 1
[ "$mac_address" = '' ] && printf 'you must set $mac_address (3rd arg)\n' && exit 1
[ "$ipv4_address" = '' ] && printf 'you must set $ipv4_address (4th arg)\n' && exit 1

# for some reason libvirt appears to remember every dhcp lease even after it has expired.
# adding a new ip-dhcp-host will fail if there already is one with the same ip address. 
# so we will try to delete any that already exist with that IP address just in case!
if [ "$action" = 'add' ]; then
  printf "trying to delete any existing (probably expired) dhcp associations for $ipv4_address..."
  virsh net-update "$network_name" delete ip-dhcp-host "<host ip='$ipv4_address' />" --live --config || true

  printf "adding $mac_address --> $ipv4_address to $network_name"
  virsh net-update "$network_name" "$action" ip-dhcp-host "<host mac='$mac_address' ip='$ipv4_address' />" --live --config
else
  printf "removing $mac_address and $ipv4_address from $network_name if they exist"
  virsh net-update "$network_name" "$action" ip-dhcp-host "<host mac='$mac_address' />" --live --config || true
  virsh net-update "$network_name" "$action" ip-dhcp-host "<host ip='$ipv4_address' />" --live --config || true
fi