#!/bin/bash

# libvirt-usb-hotplug.bash

# This script can be used to hotplug USB devices to libvirt virtual
#  machines from udev rules with systemd services.

# References:
#  - https://github.com/olavmrk/usb-libvirt-hotplug
#  - http://kicherer.org/joomla/index.php/en/blog/48-automatic-hotplugging-of-usb-devices-for-libvirt-managed-vms
#  - https://blog.tjll.net/systemd-for-device-activation-and-media-archiving/


# Abort script execution on errors
set -e

readvars() {
	PROG="$(basename "$0")"
	ACTION=$1
	IFS='_' read DOMAIN ID_VENDOR_ID ID_MODEL_ID <<< "$2"

	if [ -z "${DOMAIN}" ]; then
	  echo "Missing libvirt domain parameter for ${PROG}." >&2
	  exit 1
	fi
}

findmatch() {
	# Iterate through devlist to find match
	for i in "${devlist[@]}"; do
		# If we find a match, return successfully
		[ "${ID_VENDOR_ID}:${ID_MODEL_ID}" = "$i" ] && return 0
		# If a match can't be found, keep looping
		continue
	done
	# If no match was found, return unsuccessfully
	return 1
}

case ${ACTION} in 
	add)
		readvars
		COMMAND='attach-device'
		;;
	remove)
		readvars
		COMMAND='detach-device'
		;;
	match)
		# This section is responsible for determining if the corresponding udev rule
		#  matches against the device in question. Udev watches exit code to determine
		#  if a match was made. 
		#
		# Ref: udev(7) manpage

		# Read the config file
		source /etc/libvirt-usb-hotplug.conf

		# If we should match against any usb device, just exit successfully
		[ "$matchall" = "true" ] && exit 0

		# If the devlist array is empty, no matches can be made
		[ ${#devlist[@]} = 0 ] && exit 1

		# If targetdomain is unset or empty, exit unsuccessfully
		[ ! -v targetdomain ] && exit 1
		[ "$targetdomain" = "" ] && exit 1
		# Print the targetdomain so it can be picked back up by the udev rule
		printf "%s" "$targetdomain"

		case $listmode in 
			whitelist)
				# findmatch() returns 0 if match found, and 1 if match not found
				findmatch
				exit $?
				;;
			blacklist)
				# Reverse the exit status of findmatch() for blacklist mode
				! findmatch
				exit $?
				;;
			*)
				# If listmode is unset, or set improperly, exit unsuccessfully
				exit 1
				;;
		esac
		;;
	*)
		echo "Invalid script ACTION: ${ACTION}" >&2
		exit 1
		;;
esac

# Run the appropriate virsh-command, and ask it to read the update XML from stdin.
echo "Running virsh ${COMMAND} ${DOMAIN} --persistent for USB vendor=0x${ID_VENDOR_ID} product=0x${ID_MODEL_ID}:" >&2
(virsh "${COMMAND}" "${DOMAIN}" /dev/stdin --persistent || true) <<END
<hostdev mode='subsystem' type='usb' managed='yes'>
  <source startupPolicy='optional'>
    <vendor id='0x${ID_VENDOR_ID}' />
    <product id='0x${ID_MODEL_ID}' />
  </source>
</hostdev>
END