#!/bin/bash

# Copyright (C) 2010-2023 Pädagogisches Landesinstitut Rheinland-Pfalz
# Copyright (C) 2022-2023 Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
# Copyright (C) 2022-2023 Daniel Teichmann <daniel.teichmann@das-netzwerkteam.de>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the
# Free Software Foundation, Inc.,
# 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.

set -e

. /usr/share/debconf/confmodule || exit 255

common_file="/usr/share/debian-edu-router/debian-edu-router.common"

# Load common functions, variables and stuff.
if [ -s "$common_file" ]; then
	source "$common_file"
else
	echo "Could not load common file at "$common_file"."
	# touch /tmp/debian-edu-router-config-counter
	exit 0;
fi

if [ -e /etc/debian-edu/router.conf ]; then
	source /etc/debian-edu/router.conf
fi
PRODUCTNAME="${PRODUCTNAME:-"Debian Edu Router"}"
PACKAGE_NAME="debian-edu-router-config"
db_title "${PRODUCTNAME}"

# # FIXME: Only every other config-try would open debconf questions.
# if ! [ -f "/tmp/debian-edu-router-config-counter" ]; then
# 	debug_log "Skip first execution of config script."
# 	touch /tmp/debian-edu-router-config-counter
# 	exit 0;
# fi
# rm /tmp/debian-edu-router-config-counter || true

# Returns $existing_uplink_iface.
function get_uplink_iface_in_interface_file() {
	# Tests internet connection (also needs working domain name resolution).
	has_internet_connection
	if [ $has_internet_connection != "true" ]; then
		notice_log "No working internet connection was found."
		return
	fi

	# Every interface defined in /etc/network/interfaces{.d/*}
	ifaces_in_interfaces_file=($(get_non_d_e_r_ifaces))
	# Every interface which has at least one default route.
	ifaces_with_default_route=($(ip route | grep -E "^default via" | awk '{print $5}' | tr '\n' ' '))

	# Interfaces which are defined in /etc/network/interfaces{.d/*} and have a default route.
	uplinks_in_interface_file=($(intersect_comma_separated_items "${ifaces_in_interfaces_file[*]}" "${ifaces_with_default_route[*]}"))

	if ! [ $(echo "${#uplinks_in_interface_file[@]}") -eq 1 ]; then
		if [ $(echo "${#uplinks_in_interface_file[@]}") -lt 1 ]; then
			debug_log "There is an internet connection available, but couldn't find source of it in /etc/network/interfaces."
			return
		fi

		if ! [ $(echo "${#uplinks_in_interface_file[@]}") -gt 1 ]; then
			notice_log "Multiple possible uplinks found. Network situation is too ambiguous to just randomly select one interface."
			return
		fi
	fi

	existing_uplink_iface="${uplinks_in_interface_file}" # Yes, no [@].
}

function get_existing_uplink_information() {
	if [[ "$existing_uplink_available" = "true" ]]; then
		# debug_log "Using cached existing uplink information:"
		# debug_log "\texisting_uplink_available   - $existing_uplink_available"
		# debug_log "\texisting_uplink_method      - $existing_uplink_method"
		# debug_log "\texisting_uplink_gateway     - $existing_uplink_gateway"
		# debug_log "\texisting_uplink_address     - $existing_uplink_address"
		# debug_log "\texisting_uplink_subnetmask  - $existing_uplink_subnetmask"
		# debug_log "\texisting_uplink_nameservers - $existing_uplink_nameservers"
		return
	else
		# Delete cache
		existing_uplink_available=""
		existing_uplink_method=""
		existing_uplink_gateway=""
		existing_uplink_address=""
		existing_uplink_subnetmask=""
		existing_uplink_nameservers=""
	fi

	get_uplink_iface_in_interface_file
	if [ -z "$existing_uplink_iface" ]; then
		notice_log "Could not find existing Uplink interface."
		return
	fi

	if [ -n "$(ip a | grep $existing_uplink_iface | grep dynamic)" ]; then
		existing_uplink_method="dhcp"
		existing_uplink_address="$(ip a | grep $existing_uplink_iface | grep inet | awk -F '/' '{ print $1 }' | awk  '{ print $2 }')"
		existing_uplink_subnetmask="$(ip a | grep $existing_uplink_iface | grep inet | awk -F '/' '{ print $2 }' | awk  '{ print $1 }')"
	else
		existing_uplink_method="static"
		existing_uplink_gateway=$(ip route | grep -E "^default via" | grep "${existing_uplink_iface}" | awk '{print $3}')
		existing_uplink_address="$(ip a | grep $existing_uplink_iface | grep inet | awk -F '/' '{ print $1 }' | awk  '{ print $2 }')"
		existing_uplink_subnetmask="$(ip a | grep $existing_uplink_iface | grep inet | awk -F '/' '{ print $2 }' | awk  '{ print $1 }')"
		existing_uplink_nameservers="$(cat /etc/resolv.conf | grep nameserver | awk '{print $2}' | tr '\n' ' ')"

		if !([ "$IPV4" == true ] && is_address_v4 "${existing_uplink_gateway}") &&
			!([ "$IPV6" == true ] && is_address_v6 "${existing_uplink_gateway}"); then
			notice_log "Could not find existing and working Uplink interface. No gateway."
			return
		fi

		if !([ "$IPV4" == true ] && is_netmask_v4 "${existing_uplink_subnetmask}") &&
			!([ "$IPV6" == true ] && is_netmask_v6 "${existing_uplink_subnetmask}"); then
			notice_log "Could not find existing and working Uplink interface. No subnetmask."
			return
		fi

		if [ -z "$existing_uplink_nameservers" ]; then
			notice_log "Could not find existing and working Uplink interface. No DNS servers."
			return
		fi
	fi

	if !([ "$IPV4" == true ] && is_address_v4 "${existing_uplink_address}") &&
		!([ "$IPV6" == true ] && is_address_v6 "${existing_uplink_address}"); then
		notice_log "Could not find existing and working Uplink interface. No uplink address."
		return
	fi

	if [ -z "$existing_uplink_method" ] || [ -z "$existing_uplink_subnetmask" ]; then
		notice_log "Could not find existing and working Uplink interface."
		return
	fi

	existing_uplink_available="true"

	debug_log "An existing Uplink interface was found. It got its IP '$existing_uplink_address/$existing_uplink_subnetmask' via $existing_uplink_method."
}

function get_non_d_e_r_ifaces() {
	ifaces_dir="/etc/network/interfaces.d"
	# Find all files *not* managed by d-e-r
	readarray -d '' not_d_e_r_files < <(find "$ifaces_dir" -type f -not -name "??_d-e-r_*" -print0)

	# Add /etc/network/interfaces (if its size is over 0 bytes)
	if [ -s "/etc/network/interfaces" ]; then
		not_d_e_r_files+=(/etc/network/interfaces)
	fi

	if [ -n "${not_d_e_r_files[*]}" ]; then
		# Find all interfaces configured in those files (except if commented out)
		echo `cat "${not_d_e_r_files[@]}" | grep -P '^(?=[\s]*+[^#])[^#]*(iface)' | grep -v "iface lo" | awk '{print $2}'`
	fi
}

# $1: The state you want. Options:
#   - 'online' or '1'
#   - 'offline' or '0'
# $@: All the ifaces in a space-separated list
# Returns $_return_ifaces: All interfaces with desired online status separated
#                          by spaces.
function filter_ifaces_by_online_status() {
	_ifaces_connected=(${@:2})

	if [ "$1" == "online" ]; then
		desired_state="1"
	elif [ "$1" == "offline" ]; then
		desired_state="0"
	elif [ "$1" == "1" ]; then
		desired_state="1"
	elif [ "$1" == "0" ]; then
		desired_state="0"
	else
		error_log "filter_ifaces_by_online_status(): Desired state '$1' is not" \
			"supported."
		exit 1
	fi

	for iface in ${_ifaces_connected[@]}; do
		if [[ -z "$(ip link show dev "$iface" up)" ]]; then
			ip link set dev "$iface" up
			was_down=true
			debug_log_stderr "$iface: Waiting for iface to get up."
			while [[ -z "$(ip link show dev "$iface" up)" ]]; do
				sleep 0.1s
			done
		fi

		carrier="$(cat /sys/class/net/"$iface"/carrier)"
		if [[ "$carrier" -eq "$desired_state" ]] ; then
			_return_ifaces+=("$iface")
		fi

		if [[ "$carrier" -eq 1 ]] ; then
			debug_log_stderr "O - Interface '$iface' has a network cable attached."
		else
			debug_log_stderr "X - Interface '$iface' doesn't have a network cable attached."
		fi

		if [ "$was_down" == true ]; then
			ip link set dev "$iface" down
			was_down=false
			debug_log_stderr "  - Also interface '$iface' is down.\n"
		fi
	done
}

#
# Input: none
# Output: none
#
function set_all_available_ifaces_up() {
	ifaces_manually_configured=($(get_non_d_e_r_ifaces))

	if [ -z "${TEST_MODE}" ]; then
		ifaces_connected=($(ip a | grep -E "^[0-9]+:.*" | awk '{ print $2 }' | sed -e "s/:.*//"  \
			| grep -v "@" | grep -v -E '(lo|tun[0-9]+|vnet[0-9]+|virbr[0-9]+|lxcbr[0-9]+|docker[0-9]+|br-[a-f0-9]{12})'  \
			| tr '\n' ' '))

		# Filter out manually configured ifaces.
		for i in "${ifaces_manually_configured[@]}"; do
			ifaces_connected=(${ifaces_connected[@]/$i/})
		done

		for iface in "${ifaces_connected[@]}"; do
			if [[ -z "$(ip link show dev "$iface" up)" ]]; then
				ip link set dev "$iface" up
				warning_log_stderr "Raising network interface '$iface'."
				while [[ -z "$(ip link show dev "$iface" up)" ]]; do
					sleep 0.1s
				done
			fi
		done
	fi
}

#
# Input: none
# Output: comma-separated list of all available interfaces (with a cable connected).
# TODO: Extract ifaces_connected part into own function in commons file.
#       Then update set_all_available_ifaces_up and available_network_interfaces_offline too.
#
function available_network_interfaces_online() {
	ifaces_manually_configured=($(get_non_d_e_r_ifaces))

	if [ -z "${TEST_MODE}" ]; then
		ifaces_connected=($(ip a | grep -E "^[0-9]+:.*" | awk '{ print $2 }' | sed -e "s/:.*//"  \
			| grep -v "@" | grep -v -E '(lo|tun[0-9]+|vnet[0-9]+|virbr[0-9]+|lxcbr[0-9]+|docker[0-9]+|br-[a-f0-9]{12})'  \
			| tr '\n' ' '))

		# Filter out manually configured ifaces.
		for i in "${ifaces_manually_configured[@]}"; do
			ifaces_connected=(${ifaces_connected[@]/$i/})
		done

		# Now filter out ifaces which are not ONLINE
		declare -a _return_ifaces
		filter_ifaces_by_online_status "online" "${ifaces_connected[@]}"
		ifaces_connected=(${_return_ifaces[@]}"")

		debug_log_stderr "Following ifaces are online right now: '${ifaces_connected[@]}'."

		echo "${ifaces_connected[@]}" | sed -e 's| $||' -e 's| |, |g'
	else
		echo "eth0, eth2, eth3, eth5, eth6, eth7, eth9"
	fi
}

function available_network_interfaces_offline() {
	ifaces_manually_configured=($(get_non_d_e_r_ifaces))

	if [ -z "${TEST_MODE}" ]; then
		ifaces_connected=($(ip a | grep -E "^[0-9]+:.*" | awk '{ print $2 }' | sed -e "s/:.*//"  | grep -v "@" \
			| grep -v -E '(lo|tun[0-9]+|vnet[0-9]+|virbr[0-9]+|lxcbr[0-9]+|docker[0-9]+|br-[a-f0-9]{12})'  \
			| tr '\n' ' '))

		# Filter out manually configured ifaces.
		for i in "${ifaces_manually_configured[@]}"; do
			ifaces_connected=(${ifaces_connected[@]/$i/})
		done

		echo "${ifaces_connected[@]}" | sed -e 's| $||' -e 's| |, |g'
	else
		echo "eth0, eth1, eth2, eth3, eth4, eth5, eth6, eth7, eth8, eth9"
	fi
}

function available_network_interfaces_description_extended() {
	field="ID_MODEL_FROM_DATABASE"

	ifaces_connected=$(echo ${@} | sed -e "s/, / /g")
	for iface in ${ifaces_connected}; do
		if [ -n "${TEST_MODE}" ]; then
			echo "${iface} - Network test adapter ${iface}"
		else
			if ! [ -e "/sys/class/net/${iface}" ]; then
				error_log "Interface '${iface}' does not exist!"
				debug_log "Currently in available_network_interfaces_description_extended($@) function."
				exit 1
				continue
			fi

			iface_description=`udevadm info /sys/class/net/${iface} | grep "${field}" | sed -rn -e "s/^E: $field=(.+)/\1/p" | sed -e "s/ /_/g" || true`
			iface_macaddress=`ip addr show ${iface} | grep "link/ether" | grep -o -E ..:..:..:..:..:.. | head -1`
			echo "${iface} (${iface_macaddress}) - ${iface_description}"
		fi
	done
}

# Calculates necessary stuff and then shows the
# 'debian-edu-router-config/warn-not-enough-ifaces-available' dialog to the user.
# Input: $supported_internal_networks
# Input: $supported_internal_networks_via_vlan
function prepare_dialog_warn_not_enough_ifaces_available () {
	need_own_ifaces="$(compare_comma_separated_items "$supported_internal_networks" "$supported_internal_networks_via_vlan")"
	num_need_own_ifaces="$(echo "$need_own_ifaces" | wc -w)"

	num_vlans="0"
	num_ifaces_vlan="0"
	if [[ -n "$supported_internal_networks_via_vlan" ]]; then
		# We don't support more than one VLAN trunks
		num_vlans="$(echo "$supported_internal_networks_via_vlan" | wc -w)"
		num_ifaces_vlan="1"
	fi

	# +1 because of Uplink
	num_total_ifaces_needed="$((num_ifaces_vlan + num_need_own_ifaces + 1))"

	if [[ "$num_total_ifaces_needed" -gt "$(echo "$IFACES_AVAILABLE" | wc -w)" ]]; then
		num_networks="$(echo $supported_internal_networks | wc -w)"
		db_subst debian-edu-router-config/warn-not-enough-ifaces-available num_networks "$num_networks"
		db_subst debian-edu-router-config/warn-not-enough-ifaces-available num_networks_via_vlan "$num_vlans"
		db_subst debian-edu-router-config/warn-not-enough-ifaces-available num_ifaces "$(echo "$IFACES_AVAILABLE" | wc -w)"
		db_subst debian-edu-router-config/warn-not-enough-ifaces-available num_total_ifaces "$num_total_ifaces_needed"
	fi
}

# prepare debconf
export DC_PRIO_LOW="medium"
export DC_PRIO_HIGH="high"

db_version 2.0
db_capb backup escape

# If we don't run this script for the first time, make sure we know what IP
# proto versions are enabled for non-network configuration steps, what internal
# networks are enabled and what internal networks have static IP address set.
#
# This is really important for cases where the sysadmin chooses to skip network
# settings. We can't populate the IPV4 and IPV6 variables from within the while
# loop, so let's preset these values in case networking set up gets skipped.
#
# Sets IPV4 and IPV6 bool variables.
parse_ip_versions

db_get debian-edu-router-config/net-int-supportednetworks
supported_internal_networks="${RET}"
db_get debian-edu-router-config/net-networks-staticip-v4
net_networks_staticip_v4="${RET}"
db_get debian-edu-router-config/net-networks-staticip-v6
net_networks_staticip_v6="${RET}"

if [ "${CONFIGURE_ONLY}" = "NETWORK_IFACE_ASSIGNMENTS" ]; then
	STATE=1
	QCOUNT=23
elif [ "${CONFIGURE_ONLY}" = "NETWORK_ADDRESS_ASSIGNMENTS" ]; then
	STATE=23
	QCOUNT=49
elif [ "${CONFIGURE_ONLY}" = "NETWORK_ALL" ]; then
	STATE=1
	QCOUNT=49
elif [ "${CONFIGURE_ONLY}" = "FIREWALL_ALL" ]; then
	STATE=50
	QCOUNT=55
elif [ "${CONFIGURE_ONLY}" = "SERVICES_ALL" ]; then
	STATE=56
	QCOUNT=66
elif [ "${CONFIGURE_ONLY}" = "SERVICE_SSH" ]; then
	STATE=56
	QCOUNT=56
elif [ "${CONFIGURE_ONLY}" = "SERVICE_DHCP" ]; then
	STATE=57
	QCOUNT=66
elif [ "${CONFIGURE_ONLY}" = "NOT_IMPLEMENTED" ]; then
	STATE=67
	QCOUNT=67
elif [ "${SKIP_DEBCONF_QUESTIONS_CONFIG}" == "1" ]; then
	STATE=999
	QCOUNT=999
else
	STATE=0 # Include IP forwarding consent question (excluded above)
	QCOUNT=66
fi

# Define a starting point that cannot be skipped by going back
BACKSTOP=${STATE}

debug_log "Picked up the following debconf-question state-machine settings for ${PACKAGE_NAME}.config:"
debug_log "  - SKIP_DEBCONF_QUESTIONS_CONFIG='${SKIP_DEBCONF_QUESTIONS_CONFIG}'."
debug_log "  - CONFIGURE_ONLY=               '${CONFIGURE_ONLY}'."
debug_log "  - STATE=                        '${STATE}'."
debug_log "  - QCOUNT=                       '${QCOUNT}'."
debug_log "  - BACKSTOP=                     '${BACKSTOP}'."
debug_log "  - Script arguments=             '${0} $@'."

# Failure counters: Some question don't allow empty input or similar.
# We can't re-ask questions endlessly, but need to bail out at some point.
FCOUNTER=0

# default behaviour should be that steps go UP rather than down.
# we have this variable to track in which direction we are currently going
# for example if the user wants to backup a step at step 17
# and step 16 should be skipped (for whatever reason) then we should move on
# to step *15* instead of step 17!
STATE_DIRECTION=1

# setup milestones
# when configuring a new milestone, please test if backing up from that
# milestone does work as expected!
NETWORK_SETUP_QUESTION=1
NETWORK_SETUP_FIRST=2
NETWORK_SETUP_LAST=49
NETWORK_SETUP_SKIP_VLAN=15 # One step after last VLAN question.

# set these flags to false at start
db_set debian-edu-router-config/skip-networking-if-not-enough-ifaces-available false
db_set debian-edu-router-config/skip-networking-if-not-enough-ifaces-non-configured false
db_set debian-edu-router-config/adopt-manual-uplink-settings false

function statemachine() {
	while [ ${STATE} -gt -1 ] && [ ${STATE} -le ${QCOUNT} ] && [ ${STATE} -ge ${BACKSTOP} ]; do
		debug_log "We are currently at step ${cyan}$STATE${normal}."

		# ask questions
		case "${STATE}" in
			0)
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/ip-forwarding-consent || true
				;;
			1)
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-setup-mode || true
				;;
			2)
				###
				### Network Interface Assignments
				###

				if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

					# Counts how many times the user has to click ok, while not
					# only Uplink is connected, to make d-e-r abort.
					NUM_TRIES_DISCONNECT_ALL_INTERFACES=3

					IFACES_AVAILABLE=""
					while [ -z "${IFACES_AVAILABLE}" ]; do
						if [ $NUM_TRIES_DISCONNECT_ALL_INTERFACES -le 0 ]; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-failed-to-disconnect-all-interfaces || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi

							IFACES_AVAILABLE=""
							break
						fi

						# Interfaces could be down.
						# For example because of power saving reasons.
						set_all_available_ifaces_up

						db_subst debian-edu-router-config/net-disconnect-all-interfaces num_tries $NUM_TRIES_DISCONNECT_ALL_INTERFACES
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-disconnect-all-interfaces || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi

						NUM_TRIES_DISCONNECT_ALL_INTERFACES=$(($NUM_TRIES_DISCONNECT_ALL_INTERFACES - 1))

						if [ -z "${TEST_MODE}" ]; then
							IFACES_AVAILABLE=$(available_network_interfaces_online)
							# Test if IFACES_AVAILABLE contains multiple ifaces.
							if [ -n "$(echo "$IFACES_AVAILABLE" | grep ",")" ]; then
								IFACES_AVAILABLE=""
							fi
						else
							IFACES_AVAILABLE="eth0"
						fi
					done

					# broken out of the while loop
					if [ -z "${IFACES_AVAILABLE}" ]; then
						# Reset current d-e-r configuration progress.
						db_set debian-edu-router-config/net-setup-mode ""
						STATE="$NETWORK_SETUP_QUESTION"
						continue
					fi
				fi

				if [ $STATE_DIRECTION -eq -1 ]; then
					# This means the user backed up to this step but we need
					# data provided by step 1.
					# So we just bypass the db_go if-clause down below for one time
					# and simulate coming from step 1 so that data can be prepared
					# for this step. Finally we'll jump back to this step again.
					now_state="${STATE}"
					STATE=1
					ORIGIN_STATE=${now_state}
					BYPASS_DB_GO=true

					debug_log "Simulating step ${cyan}${STATE}" \
					          "to get data needed by step ${cyan}${now_state}${green}."
				else
					db_get debian-edu-router-config/adopt-manual-uplink-settings
					if [ "${RET}" = true ]; then
						get_existing_uplink_information
						if [[ "$existing_uplink_available" = "true" ]]; then
							db_set debian-edu-router-config/net-ext-iface-uplink "$existing_uplink_iface"
						fi
					else
						db_subst debian-edu-router-config/net-ext-iface-uplink choices "${IFACES_AVAILABLE}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${IFACES_AVAILABLE}")
						db_subst debian-edu-router-config/net-ext-iface-uplink extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-iface-uplink || true
					fi
				fi
				;;
			3)
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-supportednetworks || true
				;;
			4)
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-with-vlans || true
				;;
			5)
				db_get debian-edu-router-config/net-int-with-vlans
				if [ "${RET}" = "false" ]; then
					db_set debian-edu-router-config/net-int-iface-vlan ""

					# Prevent asking this question if vlans shouldn't be configured.
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi

				# Make sure original $IFACES_AVAILABLE does not get lost.
				_IFACES_AVAILABLE="$IFACES_AVAILABLE"

				if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-vlan || true

					if ! db_go; then
						# Backing up a step.
						STATE_DIRECTION=-1
						STATE=$(($STATE + $STATE_DIRECTION))
						continue
					fi

					if [ -z "${TEST_MODE}" ]; then
						_IFACES_AVAILABLE=$(available_network_interfaces_online)
					else
						_IFACES_AVAILABLE="eth1"
					fi
				fi

				if [ $STATE_DIRECTION -eq -1 ]; then
					# This means the user backed up to this step but we need
					# data provided by step 1.
					# So we just bypass the db_go if-clause down below for one time
					# and simulate coming from step 1 so that data can be prepared
					# for this step. Finally we'll jump back to this step again.
					now_state="${STATE}"
					STATE=1
					ORIGIN_STATE=${now_state}
					BYPASS_DB_GO=true

					debug_log "Simulating step ${cyan}${STATE}" \
					          "to get data needed by step ${cyan}${now_state}${green}."
				else
					nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-asking 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-vlan ${FCOUNTER} 5

						# Re-Ask question
						continue
					fi
					FCOUNTER=0

					db_subst debian-edu-router-config/net-int-iface-vlan choices "${nic_choices}"
					nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
					db_subst debian-edu-router-config/net-int-iface-vlan extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-vlan || true
				fi
				;;
			6)
				db_get debian-edu-router-config/net-int-with-vlans
				if [ "${RET}" = "false" ]; then
					db_set debian-edu-router-config/net-int-iface-vlan ""

					# Prevent asking this question if vlans shouldn't be configured.
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi

				if [ $STATE_DIRECTION -eq -1 ]; then
					# This means the user backed up to this step but we need
					# data provided by step 3.
					# So we just bypass the db_go if-clause down below for one time
					# and simulate coming from step 3 so that data can be prepared
					# for this step. Finally we'll jump back to this step again.
					now_state="${STATE}"
					STATE=3
					ORIGIN_STATE=${now_state}
					BYPASS_DB_GO=true

					debug_log "Simulating step ${cyan}${STATE}" \
					          "to get data needed by step ${cyan}${now_state}${green}."
				else
					db_subst debian-edu-router-config/net-int-supportednetworks-via-vlan choices "${supported_internal_networks}"
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-supportednetworks-via-vlan || true
				fi
				;;
			7)
				if echo "${supported_internal_networks_via_vlan}" | grep -q "OpenLAN" ; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-vlanid-openlan || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			8)
				if echo "${supported_internal_networks_via_vlan}" | grep -q "Education" ; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-vlanid-education || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			9)
				if echo "${supported_internal_networks_via_vlan}" | grep -q "Mgmt" ; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-vlanid-mgmt || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			10)
				if echo "${supported_internal_networks_via_vlan}" | grep -q "School-Administration" ; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-vlanid-schooladministration || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			11)
				if echo "${supported_internal_networks_via_vlan}" | grep -q "WiFi-Students" ; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-vlanid-wifistudents || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			12)
				if echo "${supported_internal_networks_via_vlan}" | grep -q "WiFi-Teachers" ; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-vlanid-wifiteachers || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			13)
				if echo "${supported_internal_networks_via_vlan}" | grep -q "WiFi-Guests" ; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-vlanid-wifiguests || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			14)
				if echo "${supported_internal_networks_via_vlan}" | grep -q "Printers" ; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-vlanid-printers || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			15)
				if echo "${supported_internal_networks}" | grep -q "OpenLAN" && \
				! echo "${supported_internal_networks_via_vlan}" | grep -q "OpenLAN"; then

					# Make sure original $IFACES_AVAILABLE does not get lost.
					_IFACES_AVAILABLE="$IFACES_AVAILABLE"

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-openlan || true
						if ! db_go; then
							# Backing up a step.
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
							continue
						fi

						if [ -z "${TEST_MODE}" ]; then
							_IFACES_AVAILABLE=$(available_network_interfaces_online)
						else
							_IFACES_AVAILABLE="eth2"
						fi

					fi

					if [ $STATE_DIRECTION -eq -1 ]; then
						# This means the user backed up to this step but we need
						# data provided by step 1.
						# So we just bypass the db_go if-clause down below for one time
						# and simulate coming from step 1 so that data can be prepared
						# for this step. Finally we'll jump back to this step again.
						now_state="${STATE}"
						STATE=1
						ORIGIN_STATE=${now_state}
						BYPASS_DB_GO=true

						debug_log "Simulating step ${cyan}${STATE}" \
						          "to get data needed by step ${cyan}${now_state}${green}."
					else
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-vlan ${nic_choices})

						if [ -z "${nic_choices}" ]; then
							if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
								bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-openlan ${FCOUNTER} 5
								FCOUNTER="$((FCOUNTER+1))"
							else
								# An empty choice list is not acceptable here
								prepare_dialog_warn_not_enough_ifaces_available
								db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true

								warning_log "There are not enough network interfaces available! Going back to setup mode question."

								# Reset current d-e-r configuration progress.
								db_set debian-edu-router-config/net-setup-mode ""
								STATE="$NETWORK_SETUP_QUESTION"
							fi

							continue
						fi
						FCOUNTER=0

						db_subst debian-edu-router-config/net-int-iface-openlan choices "${nic_choices}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
						db_subst debian-edu-router-config/net-int-iface-openlan extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-openlan || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			16)
				if echo "${supported_internal_networks}" | grep -q "Education" && \
				! echo "${supported_internal_networks_via_vlan}" | grep -q "Education"; then

					# Make sure original $IFACES_AVAILABLE does not get lost.
					_IFACES_AVAILABLE="$IFACES_AVAILABLE"

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-education || true
						if ! db_go; then
							# Backing up a step.
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
							continue
						fi

						if [ -z "${TEST_MODE}" ]; then
							_IFACES_AVAILABLE=$(available_network_interfaces_online)
						else
							_IFACES_AVAILABLE="eth3"
						fi

					fi


					if [ $STATE_DIRECTION -eq -1 ]; then
						# This means the user backed up to this step but we need
						# data provided by step 1.
						# So we just bypass the db_go if-clause down below for one time
						# and simulate coming from step 1 so that data can be prepared
						# for this step. Finally we'll jump back to this step again.
						now_state="${STATE}"
						STATE=1
						ORIGIN_STATE=${now_state}
						BYPASS_DB_GO=true

						debug_log "Simulating step ${cyan}${STATE}" \
						          "to get data needed by step ${cyan}${now_state}${green}."
					else
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-vlan ${nic_choices})
						is_supported "openlan" && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-openlan ${nic_choices})

						if [ -z "${nic_choices}" ]; then
							if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
								bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-education ${FCOUNTER} 5
								FCOUNTER="$((FCOUNTER+1))"
							else
								# An empty choice list is not acceptable here
								prepare_dialog_warn_not_enough_ifaces_available
								db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true

								warning_log "There are not enough network interfaces available! Going back to setup mode question."

								# Reset current d-e-r configuration progress.
								db_set debian-edu-router-config/net-setup-mode ""
								STATE="$NETWORK_SETUP_QUESTION"
							fi

							continue
						fi
						FCOUNTER=0

						db_subst debian-edu-router-config/net-int-iface-education choices "${nic_choices}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
						db_subst debian-edu-router-config/net-int-iface-education extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-education || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			17)
				if echo "${supported_internal_networks}" | grep -q "Mgmt" && \
				! echo "${supported_internal_networks_via_vlan}" | grep -q "Mgmt"; then

					# Make sure original $IFACES_AVAILABLE does not get lost.
					_IFACES_AVAILABLE="$IFACES_AVAILABLE"

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-mgmt || true
						if ! db_go; then
							# Backing up a step.
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
							continue
						fi

						if [ -z "${TEST_MODE}" ]; then
							_IFACES_AVAILABLE=$(available_network_interfaces_online)
						else
							_IFACES_AVAILABLE="eth4"
						fi

					fi

					if [ $STATE_DIRECTION -eq -1 ]; then
						# This means the user backed up to this step but we need
						# data provided by step 1.
						# So we just bypass the db_go if-clause down below for one time
						# and simulate coming from step 1 so that data can be prepared
						# for this step. Finally we'll jump back to this step again.
						now_state="${STATE}"
						STATE=1
						ORIGIN_STATE=${now_state}
						BYPASS_DB_GO=true

						debug_log "Simulating step ${cyan}${STATE}" \
						          "to get data needed by step ${cyan}${now_state}${green}."
					else
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-vlan ${nic_choices})
						is_supported "openlan"   && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-openlan ${nic_choices})
						is_supported "education" && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-education ${nic_choices})

						if [ -z "${nic_choices}" ]; then
							if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
								bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-mgmt ${FCOUNTER} 5
								FCOUNTER="$((FCOUNTER+1))"
							else
								# An empty choice list is not acceptable here
								prepare_dialog_warn_not_enough_ifaces_available
								db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true

								warning_log "There are not enough network interfaces available! Going back to setup mode question."

								# Reset current d-e-r configuration progress.
								db_set debian-edu-router-config/net-setup-mode ""
								STATE="$NETWORK_SETUP_QUESTION"
							fi

							continue
						fi
						FCOUNTER=0

						db_subst debian-edu-router-config/net-int-iface-mgmt choices "${nic_choices}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
						db_subst debian-edu-router-config/net-int-iface-mgmt extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-mgmt || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			18)
				if echo "${supported_internal_networks}" | grep -q "School-Administration" && \
				! echo "${supported_internal_networks_via_vlan}" | grep -q "School-Administration"; then

					# Make sure original $IFACES_AVAILABLE does not get lost.
					_IFACES_AVAILABLE="$IFACES_AVAILABLE"

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-schooladministration || true
						if ! db_go; then
							# Backing up a step.
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
							continue
						fi

						if [ -z "${TEST_MODE}" ]; then
							_IFACES_AVAILABLE=$(available_network_interfaces_online)
						else
							_IFACES_AVAILABLE="eth4"
						fi

					fi

					if [ $STATE_DIRECTION -eq -1 ]; then
						# This means the user backed up to this step but we need
						# data provided by step 1.
						# So we just bypass the db_go if-clause down below for one time
						# and simulate coming from step 1 so that data can be prepared
						# for this step. Finally we'll jump back to this step again.
						now_state="${STATE}"
						STATE=1
						ORIGIN_STATE=${now_state}
						BYPASS_DB_GO=true

						debug_log "Simulating step ${cyan}${STATE}" \
						          "to get data needed by step ${cyan}${now_state}${green}."
					else
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-vlan ${nic_choices})
						is_supported "openlan"   && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-openlan ${nic_choices})
						is_supported "education" && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-education ${nic_choices})
						is_supported "mgmt"      && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-mgmt ${nic_choices})

						if [ -z "${nic_choices}" ]; then
							if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
								bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-schooladministration ${FCOUNTER} 5
								FCOUNTER="$((FCOUNTER+1))"
							else
								# An empty choice list is not acceptable here
								prepare_dialog_warn_not_enough_ifaces_available
								db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true

								warning_log "There are not enough network interfaces available! Going back to setup mode question."

								# Reset current d-e-r configuration progress.
								db_set debian-edu-router-config/net-setup-mode ""
								STATE="$NETWORK_SETUP_QUESTION"
							fi

							continue
						fi
						FCOUNTER=0

						db_subst debian-edu-router-config/net-int-iface-schooladministration choices "${nic_choices}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
						db_subst debian-edu-router-config/net-int-iface-schooladministration extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-schooladministration || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			19)
				if echo "${supported_internal_networks}" | grep -q "WiFi-Students" && \
				! echo "${supported_internal_networks_via_vlan}" | grep -q "WiFi-Students"; then

					# Make sure original $IFACES_AVAILABLE does not get lost.
					_IFACES_AVAILABLE="$IFACES_AVAILABLE"

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-wifistudents || true
						if ! db_go; then
							# Backing up a step.
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
							continue
						fi

						if [ -z "${TEST_MODE}" ]; then
							_IFACES_AVAILABLE=$(available_network_interfaces_online)
						else
							_IFACES_AVAILABLE="eth5"
						fi

					fi

					if [ $STATE_DIRECTION -eq -1 ]; then
						# This means the user backed up to this step but we need
						# data provided by step 1.
						# So we just bypass the db_go if-clause down below for one time
						# and simulate coming from step 1 so that data can be prepared
						# for this step. Finally we'll jump back to this step again.
						now_state="${STATE}"
						STATE=1
						ORIGIN_STATE=${now_state}
						BYPASS_DB_GO=true

						debug_log "Simulating step ${cyan}${STATE}" \
						          "to get data needed by step ${cyan}${now_state}${green}."
					else
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-vlan ${nic_choices})
						is_supported "openlan"              && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-openlan ${nic_choices})
						is_supported "education"            && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-education ${nic_choices})
						is_supported "mgmt"                 && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-mgmt ${nic_choices})
						is_supported "schooladministration" && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-schooladministration ${nic_choices})

						if [ -z "${nic_choices}" ]; then
							if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
								bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-wifistudents ${FCOUNTER} 5
								FCOUNTER="$((FCOUNTER+1))"
							else
								# An empty choice list is not acceptable here
								prepare_dialog_warn_not_enough_ifaces_available
								db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true

								warning_log "There are not enough network interfaces available! Going back to setup mode question."

								# Reset current d-e-r configuration progress.
								db_set debian-edu-router-config/net-setup-mode ""
								STATE="$NETWORK_SETUP_QUESTION"
							fi

							continue
						fi
						FCOUNTER=0

						db_subst debian-edu-router-config/net-int-iface-wifistudents choices "${nic_choices}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
						db_subst debian-edu-router-config/net-int-iface-wifistudents extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifistudents || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			20)
				if echo "${supported_internal_networks}" | grep -q "WiFi-Teachers" && \
				! echo "${supported_internal_networks_via_vlan}" | grep -q "WiFi-Teachers"; then

					# Make sure original $IFACES_AVAILABLE does not get lost.
					_IFACES_AVAILABLE="$IFACES_AVAILABLE"

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-wifiteachers || true
						if ! db_go; then
							# Backing up a step.
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
							continue
						fi

						if [ -z "${TEST_MODE}" ]; then
							_IFACES_AVAILABLE=$(available_network_interfaces_online)
						else
							_IFACES_AVAILABLE="eth6"
						fi

					fi

					if [ $STATE_DIRECTION -eq -1 ]; then
						# This means the user backed up to this step but we need
						# data provided by step 1.
						# So we just bypass the db_go if-clause down below for one time
						# and simulate coming from step 1 so that data can be prepared
						# for this step. Finally we'll jump back to this step again.
						now_state="${STATE}"
						STATE=1
						ORIGIN_STATE=${now_state}
						BYPASS_DB_GO=true

						debug_log "Simulating step ${cyan}${STATE}" \
						          "to get data needed by step ${cyan}${now_state}${green}."
					else
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-vlan ${nic_choices})
						is_supported "openlan"              && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-openlan ${nic_choices})
						is_supported "education"            && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-education ${nic_choices})
						is_supported "mgmt"                 && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-mgmt ${nic_choices})
						is_supported "schooladministration" && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-schooladministration ${nic_choices})
						is_supported "wifi-students"        && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-wifistudents ${nic_choices})

						if [ -z "${nic_choices}" ]; then
							if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
								bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-wifiteachers ${FCOUNTER} 5
								FCOUNTER="$((FCOUNTER+1))"
							else
								# An empty choice list is not acceptable here
								prepare_dialog_warn_not_enough_ifaces_available
								db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true

								warning_log "There are not enough network interfaces available! Going back to setup mode question."

								# Reset current d-e-r configuration progress.
								db_set debian-edu-router-config/net-setup-mode ""
								STATE="$NETWORK_SETUP_QUESTION"
							fi

							continue
						fi
						FCOUNTER=0

						db_subst debian-edu-router-config/net-int-iface-wifiteachers choices "${nic_choices}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
						db_subst debian-edu-router-config/net-int-iface-wifiteachers extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifiteachers || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			21)
				if echo "${supported_internal_networks}" | grep -q "WiFi-Guests" && \
				! echo "${supported_internal_networks_via_vlan}" | grep -q "WiFi-Guests"; then

					# Make sure original $IFACES_AVAILABLE does not get lost.
					_IFACES_AVAILABLE="$IFACES_AVAILABLE"

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-wifiguests || true
						if ! db_go; then
							# Backing up a step.
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
							continue
						fi

						if [ -z "${TEST_MODE}" ]; then
							_IFACES_AVAILABLE=$(available_network_interfaces_online)
						else
							_IFACES_AVAILABLE="eth7"
						fi

					fi

					if [ $STATE_DIRECTION -eq -1 ]; then
						# This means the user backed up to this step but we need
						# data provided by step 1.
						# So we just bypass the db_go if-clause down below for one time
						# and simulate coming from step 1 so that data can be prepared
						# for this step. Finally we'll jump back to this step again.
						now_state="${STATE}"
						STATE=1
						ORIGIN_STATE=${now_state}
						BYPASS_DB_GO=true

						debug_log "Simulating step ${cyan}${STATE}" \
						          "to get data needed by step ${cyan}${now_state}${green}."
					else
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-vlan ${nic_choices})
						is_supported "openlan"              && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-openlan ${nic_choices})
						is_supported "education"            && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-education ${nic_choices})
						is_supported "mgmt"                 && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-mgmt ${nic_choices})
						is_supported "schooladministration" && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-schooladministration ${nic_choices})
						is_supported "wifi-students"        && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-wifistudents ${nic_choices})
						is_supported "wifi-teachers"        && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-wifiteachers ${nic_choices})

						if [ -z "${nic_choices}" ]; then
							if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
								bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-wifiguests ${FCOUNTER} 5
								FCOUNTER="$((FCOUNTER+1))"
							else
								# An empty choice list is not acceptable here
								prepare_dialog_warn_not_enough_ifaces_available
								db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true

								warning_log "There are not enough network interfaces available! Going back to setup mode question."

								# Reset current d-e-r configuration progress.
								db_set debian-edu-router-config/net-setup-mode ""
								STATE="$NETWORK_SETUP_QUESTION"
							fi

							continue
						fi
						FCOUNTER=0

						db_subst debian-edu-router-config/net-int-iface-wifiguests choices "${nic_choices}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
						db_subst debian-edu-router-config/net-int-iface-wifiguests extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifiguests || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;
			22)
				if echo "${supported_internal_networks}" | grep -q "Printers" && \
				! echo "${supported_internal_networks_via_vlan}" | grep -q "Printers"; then

					# Make sure original $IFACES_AVAILABLE does not get lost.
					_IFACES_AVAILABLE="$IFACES_AVAILABLE"

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-printers || true
						if ! db_go; then
							# Backing up a step.
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
							continue
						fi

						if [ -z "${TEST_MODE}" ]; then
							_IFACES_AVAILABLE=$(available_network_interfaces_online)
						else
							_IFACES_AVAILABLE="eth8"
						fi

					fi

					if [ $STATE_DIRECTION -eq -1 ]; then
						# This means the user backed up to this step but we need
						# data provided by step 1.
						# So we just bypass the db_go if-clause down below for one time
						# and simulate coming from step 1 so that data can be prepared
						# for this step. Finally we'll jump back to this step again.
						now_state="${STATE}"
						STATE=1
						ORIGIN_STATE=${now_state}
						BYPASS_DB_GO=true

						debug_log "Simulating step ${cyan}${STATE}" \
								"to get data needed by step ${cyan}${now_state}${green}."
					else
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${_IFACES_AVAILABLE})
						nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-vlan ${nic_choices})
						is_supported "openlan"              && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-openlan ${nic_choices})
						is_supported "education"            && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-education ${nic_choices})
						is_supported "mgmt"                 && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-mgmt ${nic_choices})
						is_supported "schooladministration" && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-schooladministration ${nic_choices})
						is_supported "wifi-students"        && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-wifistudents ${nic_choices})
						is_supported "wifi-teachers"        && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-wifiteachers ${nic_choices})
						is_supported "wifi-guests"          && nic_choices=$(filter_debconf_item debian-edu-router-config/net-int-iface-wifiguests ${nic_choices})

						if [ -z "${nic_choices}" ]; then
							if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
								bailout_on_too_many_failures debian-edu-router-config/net-connect-int-iface-printers ${FCOUNTER} 5
								FCOUNTER="$((FCOUNTER+1))"
							else
								# An empty choice list is not acceptable here
								prepare_dialog_warn_not_enough_ifaces_available
								db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true

								warning_log "There are not enough network interfaces available! Going back to setup mode question."

								# Reset current d-e-r configuration progress.
								db_set debian-edu-router-config/net-setup-mode ""
								STATE="$NETWORK_SETUP_QUESTION"
							fi

							continue
						fi
						FCOUNTER=0

						db_subst debian-edu-router-config/net-int-iface-printers choices "${nic_choices}"
						nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
						db_subst debian-edu-router-config/net-int-iface-printers extended "$(echo -e "${nic_choices_description_extended}" | debconf-escape -e)"
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-printers || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			23)
				# This questions sets $IPV4 & $IPV6.
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ip-versions-enabled || true
				;;

			###
			### Network IPv4/IPv6 Addresses
			###

			24)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				db_get debian-edu-router-config/adopt-manual-uplink-settings
				if [ "${RET}" = true ]; then
					get_existing_uplink_information
					if [ "$existing_uplink_available" = "true" ]; then
						if [ "${existing_uplink_method}" = "static" ]; then
							db_get debian-edu-router-config/net-networks-staticip-v4
							db_set debian-edu-router-config/net-networks-staticip-v4 "$(unique_comma_separated_items "Uplink" "$RET")"
						else
							db_get debian-edu-router-config/net-networks-staticip-v4
							db_set debian-edu-router-config/net-networks-staticip-v4 "$(filter_item "Uplink" "$RET")"
						fi
					fi
				fi

				db_subst debian-edu-router-config/net-networks-staticip-v4 choices "Uplink, ${supported_internal_networks}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-networks-staticip-v4 || true
				;;

			25)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				db_get debian-edu-router-config/adopt-manual-uplink-settings
				if [ "${RET}" = true ]; then
					get_existing_uplink_information
					if [ "$existing_uplink_available" = "true" ]; then
						if [ "${existing_uplink_method}" = "dhcp" ]; then
							db_get debian-edu-router-config/net-networks-dhcpclient-v4
							db_set debian-edu-router-config/net-networks-dhcpclient-v4 "$(unique_comma_separated_items "Uplink" "$RET")"
						else
							db_get debian-edu-router-config/net-networks-dhcpclient-v4
							db_set debian-edu-router-config/net-networks-dhcpclient-v4 "$(filter_item "Uplink" "$RET")"
						fi
					fi
				fi

				db_subst debian-edu-router-config/net-networks-dhcpclient-v4 choices "${net_networks_dhcpclient_v4}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-networks-dhcpclient-v4 || true
				;;

			26)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				db_get debian-edu-router-config/adopt-manual-uplink-settings
				if [ "${RET}" = true ]; then
					get_existing_uplink_information
					if [ "$existing_uplink_available" = "true" ] && [ "${existing_uplink_method}" = "static" ]; then
						db_get debian-edu-router-config/net-networks-staticip-v6
						db_set debian-edu-router-config/net-networks-staticip-v6 "$(unique_comma_separated_items "Uplink" "$RET")"
					fi
				fi

				db_subst debian-edu-router-config/net-networks-staticip-v6 choices "Uplink, ${supported_internal_networks}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-networks-staticip-v6 || true
				;;

			27)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				db_subst debian-edu-router-config/net-networks-auto-v6 choices "${net_networks_auto_v6}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-networks-auto-v6 || true
				;;

			28)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				db_subst debian-edu-router-config/net-networks-dhcpclient-v6 choices "${net_networks_dhcpclient_v6}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-networks-dhcpclient-v6 || true
				;;

			29)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "Uplink"; then
					db_get debian-edu-router-config/adopt-manual-uplink-settings
					if [ "${RET}" = true ]; then
						get_existing_uplink_information
						if [ "$existing_uplink_available" = "true" ] && [ "${existing_uplink_method}" = "static" ]; then
							db_set debian-edu-router-config/net-ext-address-v4-uplink "$existing_uplink_address/$existing_uplink_subnetmask"
						fi
					else
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-address-v4-uplink || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			30)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "Uplink"; then
					db_get debian-edu-router-config/adopt-manual-uplink-settings
					if [ "${RET}" = true ]; then
						get_existing_uplink_information
						if [ "$existing_uplink_available" = "true" ] && [ "${existing_uplink_method}" = "static" ]; then
							db_set debian-edu-router-config/net-ext-address-v6-uplink "$existing_uplink_address/$existing_uplink_subnetmask"
						fi
					else
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-address-v6-uplink || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			31)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "Uplink"; then
					db_get debian-edu-router-config/adopt-manual-uplink-settings
					if [ "${RET}" = true ]; then
						get_existing_uplink_information
						if [ "$existing_uplink_available" = "true" ] && [ "${existing_uplink_method}" = "static" ]; then
							db_set debian-edu-router-config/net-ext-gateway-v4-uplink "$existing_uplink_gateway"
						fi
					else
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-gateway-v4-uplink || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			32)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "Uplink"; then
					db_get debian-edu-router-config/adopt-manual-uplink-settings
					if [ "${RET}" = true ]; then
						get_existing_uplink_information
						if [ "$existing_uplink_available" = "true" ] && [ "${existing_uplink_method}" = "static" ]; then
							db_set debian-edu-router-config/net-ext-gateway-v6-uplink "$existing_uplink_gateway"
						fi
					else
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-gateway-v6-uplink || true
					fi
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			33)
				db_get debian-edu-router-config/adopt-manual-uplink-settings
				if [ "${RET}" = true ]; then
					get_existing_uplink_information
					if [ "$existing_uplink_available" = "true" ] && [ "${existing_uplink_method}" = "static" ]; then
						db_set debian-edu-router-config/net-ext-nameservers-uplink "$existing_uplink_nameservers"
					fi
				else
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-nameservers-uplink || true
				fi
				;;

			34)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "OpenLAN"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v4-openlan || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			35)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "OpenLAN"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v6-openlan || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			36)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "Education"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v4-education || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			37)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "Education"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v6-education || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			38)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "Mgmt"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v4-mgmt || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			39)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "Mgmt"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v6-mgmt || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			40)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "School-Administration"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v4-schooladministration || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			41)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "School-Administration"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v6-schooladministration || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			42)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "WiFi-Students"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v4-wifistudents || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			43)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "WiFi-Students"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v6-wifistudents || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			44)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "WiFi-Teachers"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v4-wifiteachers || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			45)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "WiFi-Teachers"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v6-wifiteachers || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			46)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "WiFi-Guests"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v4-wifiguests || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			47)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "WiFi-Guests"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v6-wifiguests || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			48)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v4}" | grep -q "Printers"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v4-printers || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			49)
				# Special case: User backed up after skipping network setup.
				if [[ -n "$USER_SKIPPED_NETWORK_SETUP" ]]; then
					# We are going to $NETWORK_SETUP_QUESTION - 1 because
					# STATE control goes directly to $NETWORK_SETUP_QUESTION + 1
					# This causes a bug if one has failed STEP-BY-STEP setup,
					# was sent to the network-setup question again, skipped
					# network-setup and then backed up again.
					STATE="$(($NETWORK_SETUP_QUESTION - 1))";
					STATE_DIRECTION=1
				fi

				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${net_networks_staticip_v6}" | grep -q "Printers"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-address-v6-printers || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			### Firewall

			50)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				# start with all networks
				service_firewall_networks_nat="${supported_internal_networks}"
				db_subst debian-edu-router-config/service-firewall-networks-nat choices "${service_firewall_networks_nat}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-networks-nat || true
				;;

			51)
				db_subst debian-edu-router-config/service-firewall-networks-routed choices "${service_firewall_networks_routed}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-networks-routed || true
				;;

			52)
				service_firewall_networks_allow_internet="${supported_internal_networks}"
				db_subst debian-edu-router-config/service-firewall-networks-allow-internet choices "${service_firewall_networks_allow_internet}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-networks-allow-internet || true
				;;

			53)
				# Suitable for both IPv4 and IPv6
				db_get debian-edu-router-config/service-firewall-networks-allow-internet
				service_firewall_networks_allow_internet="${RET}"

				unequal_items="$(compare_comma_separated_items "${supported_internal_networks}" "${service_firewall_networks_allow_internet}")"
				if [ -z "${unequal_items}" ]; then
					# If all networks are allowed to have direct internet access
					# anyway, then don't bother to ask this question.
					STATE=$(($STATE + $STATE_DIRECTION));
					debug_log "All supported networks have direct internet access, skipping trustworthy IPs/networks step..."
					continue;
				fi

				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-trustworthy-ips || true
				;;

			54)
				# Reverse NAT: This question is IPv4 only
				if [ "$IPV4" != true ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-reverse-nat-configs || true
				;;

			55)
				# Incoming SSH connections
				db_subst debian-edu-router-config/service-firewall-ssh-incoming choices "$(unique_comma_separated_items Uplink ${supported_internal_networks})"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-ssh-incoming || true
				;;

			###
			### SERVICES:
			###

			#
			# Service: SSH
			#

			56)
				# Asking port for SSH services
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-ssh-custom-port || true
				;;

			#
			# Service: DHCP
			#

			57)
				if [ "$IPV4" != true ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				# start with networks that have a static IPv4 address on this host (except Uplink network)
				service_dhcp_networks_v4="$(echo ${net_networks_staticip_v4} | sed -e 's/Uplink, //g')"
				db_subst debian-edu-router-config/service-dhcp-networks-v4 choices "${service_dhcp_networks_v4}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-networks-v4 || true
				;;

			58)
				if [ "${IPV6}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				# start with networks that have a static IPv6 address on this host (except Uplink network)
				service_dhcp_networks_v6="$(echo ${net_networks_staticip_v6} | sed -e 's/Uplink, //g')"
				db_subst debian-edu-router-config/service-dhcp-networks-v6 choices "${service_dhcp_networks_v6}"
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-networks-v6 || true
				;;

			59)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${service_dhcp_networks_v4}" | grep -q "OpenLAN"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-range-v4-openlan || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			60)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${service_dhcp_networks_v4}" | grep -q "Education"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-range-v4-education || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			61)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${service_dhcp_networks_v4}" | grep -q "Mgmt"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-range-v4-mgmt || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			62)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${service_dhcp_networks_v4}" | grep -q "School-Administration"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-range-v4-schooladministration || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			63)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${service_dhcp_networks_v4}" | grep -q "WiFi-Students"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-range-v4-wifistudents || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			64)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${service_dhcp_networks_v4}" | grep -q "WiFi-Teachers"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-range-v4-wifiteachers || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			65)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${service_dhcp_networks_v4}" | grep -q "WiFi-Guests"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-range-v4-wifiguests || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			66)
				if [ "${IPV4}" != "true" ]; then STATE=$(($STATE + $STATE_DIRECTION)); continue; fi

				if echo "${service_dhcp_networks_v4}" | grep -q "Printers"; then
					db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-dhcp-range-v4-printers || true
				else
					STATE=$(($STATE + $STATE_DIRECTION))
					continue
				fi
				;;

			### END OF SERVICES

			# not implemented yet...
			67)
				db_input ${DC_PRIO_HIGH} debian-edu-router-config/not-implemented-yet || true
				;;

			# Used for skipping/aborting questions entirely.
			999)
				;;

			*)
				echo "Unknown state ${STATE}!";
				exit 255
				;;

		esac

		if db_go || [ "$BYPASS_DB_GO" == true ]; then
			# evaluate answers
			case "${STATE}" in
				0)
					db_get debian-edu-router-config/ip-forwarding-consent
					if [ "${RET}" != "Yes" ]; then
						echo "Aborting configuration of Debian Edu Router as requested."
						exit 1
					fi
					;;
				1)
					USER_SKIPPED_NETWORK_SETUP=""

					db_get debian-edu-router-config/net-setup-mode
					net_setup_mode=$(echo "${RET}" | cut -d" " -f1)
					if [ "${net_setup_mode}" == "" ] || \
					[ "${net_setup_mode}" == "SKIP-NETWORK-SETUP" ]; then
						STATE=$((${NETWORK_SETUP_LAST} + 1))
						USER_SKIPPED_NETWORK_SETUP="true"
						continue
					else
						# detect network interfaces
						if [ "${net_setup_mode}" = "OFFLINE-SETUP" ]; then
							IFACES_AVAILABLE=$(available_network_interfaces_offline)
						elif [ "${net_setup_mode}" = "ALL-CONNECTED" ]; then
							IFACES_AVAILABLE=$(available_network_interfaces_online)
						elif [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
							# delay checking number of online interfaces
							# be content with offline interfaces for now
							IFACES_AVAILABLE=$(available_network_interfaces_offline)
						fi
					fi

					# --- Adopt existing Uplink info from /etc/network/interfaces{.d/*} --- #
					# Force "delete" cache
					existing_uplink_available=""
					# FIXME: Only execute get_existing_uplink_information if uplink is not actually set. (First time run?)
					# if uplink_not_set; then
						get_existing_uplink_information
						existing_uplink_info="$existing_uplink_iface ($existing_uplink_method) - $existing_uplink_address/$existing_uplink_subnetmask"
					#fi

					if [[ "$existing_uplink_available" = "true" ]]; then
						# Always reset question.
						db_set debian-edu-router-config/adopt-manual-uplink-settings false
						db_subst debian-edu-router-config/adopt-manual-uplink-settings uplink_info "$(echo ${existing_uplink_info} | debconf-escape -e)"
						db_subst debian-edu-router-config/adopt-manual-uplink-settings uplink_iface "$(echo ${existing_uplink_iface} | debconf-escape -e)"
						db_input $DC_PRIO_HIGH debian-edu-router-config/adopt-manual-uplink-settings || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
							# db_get gets true, then.
						fi

						db_get debian-edu-router-config/adopt-manual-uplink-settings
						if [ "${RET}" = true ]; then
							IFACES_AVAILABLE="$(unique_comma_separated_items "$IFACES_AVAILABLE" "$existing_uplink_iface")"
						fi
					fi
					# ---

					# we need at least two network interfaces
					if ! echo "${IFACES_AVAILABLE}" | grep -q ", "; then
						db_set debian-edu-router-config/skip-networking-if-not-enough-ifaces-available true
						db_set debian-edu-router-config/skip-networking-if-not-enough-ifaces-non-configured true

						# skip network setup, not enough interfaces available
						non_d_e_r_ifaces=`get_non_d_e_r_ifaces`
						if [ -n "${non_d_e_r_ifaces}" ]; then
							db_subst debian-edu-router-config/skip-networking-if-not-enough-ifaces-non-configured non_d_e_r_ifaces "$(echo ${non_d_e_r_ifaces} | tr ' ' '\n' | debconf-escape -e)"
							db_input $DC_PRIO_HIGH debian-edu-router-config/skip-networking-if-not-enough-ifaces-non-configured || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
								# db_get gets true, then.
							fi
							db_get debian-edu-router-config/skip-networking-if-not-enough-ifaces-non-configured
						else
							db_input $DC_PRIO_HIGH debian-edu-router-config/skip-networking-if-not-enough-ifaces-available || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
								# db_get gets true, then.
							fi
							db_get debian-edu-router-config/skip-networking-if-not-enough-ifaces-available
						fi

						if [ "${RET}" = false ]; then
							STATE=1
							continue
						else
							STATE=999
						fi
					fi

					;;
				2)
					nic_choices=$(filter_debconf_item debian-edu-router-config/net-ext-iface-uplink ${IFACES_AVAILABLE})

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-ext-iface-uplink
						uplink_iface="${RET}"
						db_subst debian-edu-router-config/net-ext-iface-uplink-assigned iface "$uplink_iface" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-iface-uplink-assigned || true
						db_go || true
					fi

					;;
				3)
					db_get debian-edu-router-config/net-int-supportednetworks
					if [ -z "${RET}" ]; then
						# An empty choice is not acceptable here, tolerate re-asking 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-supportednetworks ${FCOUNTER} 5
						# Simply re-ask the question for supported internal network types
						continue
					fi
					supported_internal_networks="${RET}"

					# Possibly remove networks service-firewall-networks-allow-internet, in case they got removed from
					# net-int-supportednetworks.
					db_get debian-edu-router-config/service-firewall-networks-allow-internet || true
					firewall_networks_allow_internet="${RET}"
					firewall_networks_allow_internet=$(intersect_comma_separated_items "${supported_internal_networks}" "${firewall_networks_allow_internet}")
					db_set debian-edu-router-config/service-firewall-networks-allow-internet "${firewall_networks_allow_internet}"

					FCOUNTER=0
					;;
				4)
					db_get debian-edu-router-config/net-int-with-vlans
					if [ "${RET}" = "false" ]; then
						db_set debian-edu-router-config/net-int-iface-vlan ""
						STATE=$((${NETWORK_SETUP_SKIP_VLAN}-1))
					fi
					;;
				5)
					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-vlan || true
						db_subst debian-edu-router-config/net-int-iface-vlan-assigned iface "${RET}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-vlan-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				6)
					db_get debian-edu-router-config/net-int-supportednetworks-via-vlan
					if [ -z "${RET}" ]; then
						# An empty choice is not acceptable here, tolerate re-asking 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-supportednetworks-via-vlan ${FCOUNTER} 5
						# Simply re-ask the question for supported internal network
						# types via VLAN.
						continue
					fi
					supported_internal_networks_via_vlan="${RET}"

					if [ "${net_setup_mode}" != "STEP-BY-STEP" ]; then
						prepare_dialog_warn_not_enough_ifaces_available
						if [[ "$num_total_ifaces_needed" -gt "$(echo "$IFACES_AVAILABLE" | wc -w)" ]]; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/warn-not-enough-ifaces-available || true
							bailout_on_too_many_failures debian-edu-router-config/net-int-supportednetworks-via-vlan ${FCOUNTER} 5

							continue
						fi
					fi
					FCOUNTER=0

					;;
				7)
					db_get debian-edu-router-config/net-int-vlanid-openlan
					_vlanid=$(echo ${RET} | sed -e "s/\s//g")
					if ! is_vlanid ${_vlanid}; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-vlanid-openlan ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0
					;;
				8)
					db_get debian-edu-router-config/net-int-vlanid-education
					_vlanid=$(echo ${RET} | sed -e "s/\s//g")
					if ! is_vlanid ${_vlanid}; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-vlanid-education ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0
					;;
				9)
					db_get debian-edu-router-config/net-int-vlanid-mgmt
					_vlanid=$(echo ${RET} | sed -e "s/\s//g")
					if ! is_vlanid ${_vlanid}; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-vlanid-mgmt ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0
					;;
				10)
					db_get debian-edu-router-config/net-int-vlanid-schooladministration
					_vlanid=$(echo ${RET} | sed -e "s/\s//g")
					if ! is_vlanid ${_vlanid}; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-vlanid-schooladministration ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0
					;;
				11)
					db_get debian-edu-router-config/net-int-vlanid-wifistudents
					_vlanid=$(echo ${RET} | sed -e "s/\s//g")
					if ! is_vlanid ${_vlanid}; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-vlanid-wifistudents ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0
					;;
				12)
					db_get debian-edu-router-config/net-int-vlanid-wifiteachers
					_vlanid=$(echo ${RET} | sed -e "s/\s//g")
					if ! is_vlanid ${_vlanid}; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-vlanid-wifiteachers ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0
					;;
				13)
					db_get debian-edu-router-config/net-int-vlanid-wifiguests
					_vlanid=$(echo ${RET} | sed -e "s/\s//g")
					if ! is_vlanid ${_vlanid}; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-vlanid-wifiguests ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0
					;;
				14)
					db_get debian-edu-router-config/net-int-vlanid-printers
					_vlanid=$(echo ${RET} | sed -e "s/\s//g")
					if ! is_vlanid ${_vlanid}; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-int-vlanid-printers ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0
					;;
				15)

					# if we reach here, network setup is obviously possible, enough interfaces have been found
					db_set debian-edu-router-config/skip-networking-if-not-enough-ifaces-available false
					db_set debian-edu-router-config/skip-networking-if-not-enough-ifaces-non-configured false

					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-openlan
						openlan_iface="${RET}"
						db_subst debian-edu-router-config/net-int-iface-openlan-assigned iface "${openlan_iface}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-openlan-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				16)
					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-education
						education_iface="${RET}"
						db_subst debian-edu-router-config/net-int-iface-education-assigned iface "${education_iface}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-education-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				17)
					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-mgmt
						mgmt_iface="${RET}"
						db_subst debian-edu-router-config/net-int-iface-mgmt-assigned iface "${mgmt_iface}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-mgmt-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				18)
					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-schooladministration
						schooladministration_iface="${RET}"
						db_subst debian-edu-router-config/net-int-iface-schooladministration-assigned iface "${schooladministration_iface}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-schooladministration-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				19)
					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-wifistudents
						wifistudents_iface="${RET}"
						db_subst debian-edu-router-config/net-int-iface-wifistudents-assigned iface "${wifistudents_iface}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifistudents-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				20)
					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-wifiteachers
						wifiteachers_iface="${RET}"
						db_subst debian-edu-router-config/net-int-iface-wifiteachers-assigned iface "${wifiteachers_iface}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifiteachers-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				21)
					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-wifiguests
						wifiguests_iface="${RET}"
						db_subst debian-edu-router-config/net-int-iface-wifiguests-assigned iface "${wifiguests_iface}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifiguests-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				22)
					if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						db_get debian-edu-router-config/net-int-iface-printers
						printers_iface="${RET}"
						db_subst debian-edu-router-config/net-int-iface-printers-assigned iface "${printers_iface}" || true
						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-printers-assigned || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi
					fi
					;;
				23)
					db_get debian-edu-router-config/net-ip-versions-enabled
					if [ -z "${RET}" ]; then
						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-ip-versions-enabled ${FCOUNTER} 5
						continue
					fi
					FCOUNTER=0

					parse_ip_versions
					;;

				###
				### Network IPv4/IPv6 Addresses
				###

				24)
					db_get debian-edu-router-config/net-networks-staticip-v4
					net_networks_staticip_v4="${RET}"
					net_networks_dhcpclient_v4="Uplink, ${supported_internal_networks}"
					for network in $(echo "${net_networks_staticip_v4}" | sed -e 's/,//g'); do
						net_networks_dhcpclient_v4=`echo ${net_networks_dhcpclient_v4} | sed -Ee "s/(${network}, |, ${network}|${network})//g"`
					done
					;;

				25)
					db_get debian-edu-router-config/net-networks-dhcpclient-v4
					net_networks_dhcpclient_v4="${RET}"
					net_networks_manual_v4="Uplink, ${supported_internal_networks}"
					for network in $(echo "${net_networks_staticip_v4}, ${net_networks_dhcpclient_v4}" | sed -e 's/,//g'); do
						net_networks_manual_v4=`echo ${net_networks_manual_v4} | sed -Ee "s/(${network}, |, ${network}|${network})//g"`
					done
					db_subst debian-edu-router-config/net-networks-manual-v4 choices "${net_networks_manual_v4}"
					db_set debian-edu-router-config/net-networks-manual-v4 "${net_networks_manual_v4}"
					db_fset debian-edu-router-config/net-networks-manual-v4 seen true
					;;

				26)
					db_get debian-edu-router-config/net-networks-staticip-v6
					net_networks_staticip_v6="${RET}"
					net_networks_auto_v6="Uplink, ${supported_internal_networks}"
					for network in $(echo "${net_networks_staticip_v6}" | sed -e 's/,//g'); do
						net_networks_auto_v6=`echo ${net_networks_auto_v6} | sed -Ee "s/(${network}, |, ${network}|${network})//g"`
					done
					;;

				27)
					db_get debian-edu-router-config/net-networks-auto-v6
					net_networks_auto_v6="${RET}"
					net_networks_manual_v6="Uplink, ${supported_internal_networks}"
					for network in $(echo "${net_networks_staticip_v4}, ${net_networks_auto_v6}" | sed -e 's/,//g'); do
						net_networks_manual_v6=`echo ${net_networks_manual_v6} | sed -Ee "s/(${network}, |, ${network}|${network})//g"`
					done
					db_subst debian-edu-router-config/net-networks-manual-v6 choices "${net_networks_manual_v6}"
					db_set debian-edu-router-config/net-networks-manual-v6 "${net_networks_manual_v6}"
					db_fset debian-edu-router-config/net-networks-manual-v6 seen true

					# interfaces that are candidates for IPv6 router advertisement are also candidates for DHCPv6
					net_networks_dhcpclient_v6="${net_networks_auto_v6}"
					;;

				28)
					;;

				###
				### Service to Network Assignments
				###

				29)
					if echo "${net_networks_staticip_v4}" | grep -q "Uplink"; then
						db_get debian-edu-router-config/net-ext-address-v4-uplink || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/net-ext-address-v4-uplink ${FCOUNTER} 5
							continue
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0
					fi
					;;

				30)
					if echo "${net_networks_staticip_v6}" | grep -q "Uplink"; then
						db_get debian-edu-router-config/net-ext-address-v6-uplink || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				31)
					if echo "${net_networks_staticip_v4}" | grep -q "Uplink"; then
						db_get debian-edu-router-config/net-ext-gateway-v4-uplink || true
						if ! is_address_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				32)
					# Check whether an IPv6 network address has been configured for the 'Uplink' interface.
					# And only if so, ask for an IPv6 gateway adress.
					db_get debian-edu-router-config/net-ext-address-v6-uplink || true
					if echo "${net_networks_staticip_v6}" | grep -q "Uplink" && [ -n "${RET}" ]; then
						db_get debian-edu-router-config/net-ext-gateway-v6-uplink || true
						if ! is_address_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				33)
					db_get debian-edu-router-config/net-networks-staticip-v4
					networks_static_v4="${RET}"
					if [ "$IPV4" == true ] && [ -n "$(echo "${networks_static_v4}" | grep Uplink)" ]; then
						needs_ipv4_nameserver_address=true
						debug_log "An external IPv4 nameserver must be specified since Uplink NIC is configured statically."
					else
						needs_ipv4_nameserver_address=false
					fi

					db_get debian-edu-router-config/net-networks-staticip-v6
					networks_static_v6="${RET}"
					if [ "$IPV6" == true ] && [ -n "$(echo "${networks_static_v6}" | grep Uplink)" ]; then
						needs_ipv6_nameserver_address=true
						debug_log "An external IPv6 nameserver must be specified since Uplink NIC is configured statically."
					else
						needs_ipv6_nameserver_address=false
					fi

					db_get debian-edu-router-config/net-ext-nameservers-uplink || true
					dns_nameservers="$(echo ${RET} | sed -E -e "s/,/ /g" -e "s/\s+/ /g")"

					if [ -z "${dns_nameservers}" ]; then
						# Only absolutely require external nameservers, if 'Uplink' is configured statically,
						# IPv4 nameservers can answer queries for IPv6 addresses and vice versa. So, in theory,
						# it is sufficient to configure one nameserver IP.

						if [ "$needs_ipv4_nameserver_address" == true ] || [ "$needs_ipv6_nameserver_address" == true ]; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-nameservers-uplink-required || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi

							warning_log "An external nameserver must be specified since Uplink is configured statically!"

							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/net-ext-nameservers-uplink ${FCOUNTER} 5
							continue
						fi
					fi

					invalid_nameserver=false
					# Check for invalid entries
					for dns_addr in ${dns_nameservers}; do
						if [ "$IPV4" == true ] && is_address_v4 "${dns_addr}"; then
							# Alright, address looks good. Check next one.
							debug_log "IPv4 nameserver address '$dns_addr' could be verified."
							continue
						elif [ "$IPV6" == true ] && is_address_v6 "${dns_addr}"; then
							# Alright, address looks good. Check next one.
							debug_log "IPv6 nameserver address '$dns_addr' could be verified."
							continue
						fi

						warning_log "Nameserver address '$dns_addr' is *not* valid!"

						db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-nameserver || true
						if ! db_go; then
							debug_log "Ignoring backup/db_go-failure..."
						fi

						invalid_nameserver=true

						FCOUNTER=$((${FCOUNTER}+1))
						bailout_on_too_many_failures debian-edu-router-config/net-ext-nameservers-uplink ${FCOUNTER} 5
						break
					done

					# Let the user retry if invalid entry was found.
					if [ "${invalid_nameserver}" == true ]; then
						continue
					fi

					FCOUNTER=0
					;;

				34)
					if echo "${net_networks_staticip_v4}" | grep -q "OpenLAN"; then
						db_get debian-edu-router-config/net-int-address-v4-openlan || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				35)
					if echo "${net_networks_staticip_v6}" | grep -q "OpenLAN"; then
						db_get debian-edu-router-config/net-int-address-v6-openlan || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				36)
					if echo "${net_networks_staticip_v4}" | grep -q "Education"; then
						db_get debian-edu-router-config/net-int-address-v4-education || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				37)
					if echo "${net_networks_staticip_v6}" | grep -q "Education"; then
						db_get debian-edu-router-config/net-int-address-v6-education || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				38)
					if echo "${net_networks_staticip_v4}" | grep -q "Mgmt"; then
						db_get debian-edu-router-config/net-int-address-v4-mgmt || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				39)
					if echo "${net_networks_staticip_v6}" | grep -q "Mgmt"; then
						db_get debian-edu-router-config/net-int-address-v6-mgmt || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				40)
					if echo "${net_networks_staticip_v4}" | grep -q "School-Administration"; then
						db_get debian-edu-router-config/net-int-address-v4-schooladministration || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				41)
					if echo "${net_networks_staticip_v6}" | grep -q "School-Administration"; then
						db_get debian-edu-router-config/net-int-address-v6-schooladministration || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				42)
					if echo "${net_networks_staticip_v4}" | grep -q "WiFi-Students"; then
						db_get debian-edu-router-config/net-int-address-v4-wifistudents || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				43)
					if echo "${net_networks_staticip_v6}" | grep -q "WiFi-Students"; then
						db_get debian-edu-router-config/net-int-address-v6-wifistudents || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				44)
					if echo "${net_networks_staticip_v4}" | grep -q "WiFi-Teachers"; then
						db_get debian-edu-router-config/net-int-address-v4-wifiteachers || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				45)
					if echo "${net_networks_staticip_v6}" | grep -q "WiFi-Teachers"; then
						db_get debian-edu-router-config/net-int-address-v6-wifiteachers || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				46)
					if echo "${net_networks_staticip_v4}" | grep -q "WiFi-Guests"; then
						db_get debian-edu-router-config/net-int-address-v4-wifiguests || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				47)
					if echo "${net_networks_staticip_v6}" | grep -q "WiFi-Guests"; then
						db_get debian-edu-router-config/net-int-address-v6-wifiguests || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				48)
					if echo "${net_networks_staticip_v4}" | grep -q "Printers"; then
						db_get debian-edu-router-config/net-int-address-v4-printers || true
						if ! is_valid_ipconfig_v4 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv4 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				49)
					if echo "${net_networks_staticip_v6}" | grep -q "Printers"; then
						db_get debian-edu-router-config/net-int-address-v6-printers || true
						# an IPv6 address is optional, so it can be left empty
						if [ -n "${RET}" ] && ! is_valid_ipconfig_v6 "${RET}"; then
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-syntax-invalid-ipv6 || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
					fi
					;;

				### Firewall

				50)
					db_get debian-edu-router-config/service-firewall-networks-nat || true
					service_firewall_networks_nat="${RET}"
					service_firewall_networks_routed="${supported_internal_networks}"
					for network in $(echo "${service_firewall_networks_nat}" | sed -e 's/,//g'); do
						service_firewall_networks_routed=`echo ${service_firewall_networks_routed} | sed -Ee "s/(${network}, |, ${network}|${network})//g"`
					done
					;;

				51)
					db_get debian-edu-router-config/service-firewall-networks-routed || true
					service_firewall_networks_routed="${RET}"
					service_firewall_networks_hostonly="${supported_internal_networks}"
					for network in $(echo "${service_firewall_networks_nat}, ${service_firewall_networks_routed}" | sed -e 's/,//g'); do
						service_firewall_networks_hostonly=`echo ${service_firewall_networks_hostonly} | sed -Ee "s/(${network}, |, ${network}|${network})//g"`
					done
					db_subst debian-edu-router-config/service-firewall-networks-hostonly choices "${service_firewall_networks_hostonly}"
					db_set debian-edu-router-config/service-firewall-networks-hostonly "${service_firewall_networks_hostonly}"
					;;

				52)
					db_get debian-edu-router-config/service-firewall-networks-allow-internet || true
					service_firewall_networks_allow_internet="${RET}"
					service_firewall_networks_block_internet="${supported_internal_networks}"
					for network in $(echo "${service_firewall_networks_allow_internet}" | sed -e 's/,//g'); do
						service_firewall_networks_block_internet=`echo ${service_firewall_networks_block_internet} | sed -Ee "s/(${network}, |, ${network}|${network})//g"`
					done
					db_subst debian-edu-router-config/service-firewall-networks-block-internet choices "${service_firewall_networks_block_internet}"
					db_set debian-edu-router-config/service-firewall-networks-block-internet "${service_firewall_networks_block_internet}"
					;;

				53)
					# Check if debian-edu-router-config/service-firewall-trustworthy-ips
					# is valid
					db_get debian-edu-router-config/service-firewall-trustworthy-ips

					if [[ -n "${RET}" ]]; then
						declare -a trustworthy_ips=(${RET})

						# Collect all internal addresses/networks
						declare -A internal_networks
						get_internal_networks_v4
						# debug_log "Internal networks found for trustworthy " \
						# 		  "addresses/networks validation:"
						# for _i_n_name in "${!internal_networks[@]}"; do
						# 	debug_log "  - $_i_n_name:\t${internal_networks[$_i_n_name]}"
						# done

						failure_in_for_loop=""
						for item in "${trustworthy_ips[@]}"; do
							item_ip_version=""

							# Could be a network or an address. So let's figure out what
							# it is. We could generally say everything containing a '/'
							# should be consired as a network.
							if [[ "$item" == *"/"* ]]; then
								if [ "${IPV4}" == "true" ]; then
									is_valid_ipconfig_v4 "${item}" && item_ip_version="network_v4"
								fi
								if [ "${IPV6}" == "true" ]; then
									is_valid_ipconfig_v6 "${item}" && item_ip_version="network_v6"
								fi

								if ! [ "$item_ip_version" = "network_v4" ] && \
								! [ "$item_ip_version" = "network_v6" ]; then
									debug_log "${item}: Is *not* a valid IP network!"
									failure_in_for_loop="invalid_ip_network"
									break
								fi
							else
								if [ "${IPV4}" == "true" ]; then
									is_address_v4 "${item}" && item_ip_version="address_v4"
								fi
								if [ "${IPV6}" == "true" ]; then
									is_address_v6 "${item}" && item_ip_version="address_v6"
								fi

								if ! [ "$item_ip_version" = "address_v4" ] && \
								! [ "$item_ip_version" = "address_v6" ]; then
									debug_log "${item}: Is *not* a valid IP address!"
									failure_in_for_loop="invalid_ip_address"
									break
								fi
							fi

							matching_internal_network=""
							# For-loop in a for-loop is often not a good idea
							# but we don't have that many supported internal networks.
							for _i_n_name in "${!internal_networks[@]}"; do
								_internal_network="${internal_networks[$_i_n_name]}"

								if is_valid_ipconfig_v4 "$_internal_network"; then
									if [[ "$item_ip_version" =~ "_v4" ]]; then
										#debug_log "Checking if IPv4 address/network '$item' is in network '$_internal_network'..."
										if is_ip4config_in_network "$item" "$_internal_network"; then
											debug_log "IPv4 address/network $item is in network '$_internal_network'!"
											matching_internal_network="$_internal_network"
											break
										fi
									fi
								elif is_valid_ipconfig_v6 "$_internal_network"; then
									if [[ "$item_ip_version" =~ "_v6" ]]; then
										#debug_log "Checking if IPv6 address/network '$item' is in network '$_internal_network'..."
										# TODO: Create function is_ip6config_in_network
										debug_log "----- IPv6 matching is not yet implemented! -----"
										# if is_ip6config_in_network "$item" "$_internal_network"; then
										# 	debug_log "IPv6 address/network $item is in network '$_internal_network'!"
										# 	matching_internal_network="$_internal_network"
										#	break
										# fi
									fi
								else
									error_log "Found invalid internal network '$_internal_network'!"
									error_log "This definitely shouldn't be possible. Aborting configuration now."
									error_log "Run 'dpkg-configure debian-edu-router-config' from the"
									error_log "command line and fix your configuration."
									exit 1
								fi
							done

							if [[ -z "$matching_internal_network" ]]; then
								failure_in_for_loop="no_matching_internal_network"

								db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-invalid-trustworthy-ips || true
								if ! db_go; then
									debug_log "Ignoring backup/db_go-failure..."
								fi

								FCOUNTER=$((${FCOUNTER}+1))
								bailout_on_too_many_failures debian-edu-router-config/service-firewall-trustworthy-ips ${FCOUNTER} 5

								# Let the user try again
								STATE_DIRECTION=-1
								STATE=$(($STATE + $STATE_DIRECTION))
								break
							fi
							# Do not reset $FCOUNTER here. We want to reset it below.
						done

						# If an invalid IP address or network was specified.
						# Invalid means: Neither valid IPv4 nor valid IPv6
						if [[ "$failure_in_for_loop" = "invalid_ip_"* ]]; then
							debug_log "Reason for retry: $failure_in_for_loop."

							reason_text="Unknown reason."
							case $failure_in_for_loop in
								"invalid_ip_"*)
									reason_text="A malformed IP/network was specified."
								;;

								"no_matching_internal_network")
									reason_text="One of the specified IPs/networks is $(
									)not part of an internal network and can $(
									)therefore not be matched."
								;;
							esac
							db_subst debian-edu-router-config/service-firewall-invalid-trustworthy-ips reason "$reason_text"

							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-invalid-trustworthy-ips || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi

							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-firewall-trustworthy-ips ${FCOUNTER} 5

							# Let the user try again
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
						elif [[ "$failure_in_for_loop" != "no_matching_internal_network" ]]; then
							FCOUNTER=0
						fi
					fi
					;;

				54)
					db_get debian-edu-router-config/service-firewall-reverse-nat-configs

					if [[ -n "${RET}" ]]; then
						declare -a reverse_nat_configs=(${RET})

						db_get debian-edu-router-config/service-firewall-networks-nat || true
						service_firewall_networks_nat="${RET}"

						# Examples:
						# reverse_nat_configs=("tcp:200:10.0.2.2:22" "udp:25565:10.0.2.10:26000"
						# 	"udp:25565:10.0.2.10" "25565:10.0.2.10:26000" "25565:10.0.2.250")

						for item in "${reverse_nat_configs[@]}"; do
							parse_reverse_nat_config "$item"
							if [ -n "$failure_in_parsing" ]; then
								break
							else
								debug_log "Config item '$item' is valid." \
										"Following things could be extracted:"
								debug_log "  - Protocol:         $rn_protocol"
								debug_log "  - External port:    $rn_extern_port"
								debug_log "  - Host address:     $rn_host_address"
								debug_log "  - Host port:        $rn_host_port"
								debug_log "  - Internal network: $rn_matching_internal_network"
							fi
						done

						if [ -n "$failure_in_parsing" ]; then
							debug_log "Reason for retry: $failure_in_parsing."
							reason_text="Unknown reason."
							case $failure_in_parsing in
								"invalid_"*)
									reason_text="A malformed input was detected."
								;;

								"no_matching_internal_network")
									reason_text="One of the specified host addresses $(
									)is not part of an internal network or the network $(
									)is not configured to be hidden behind a NAT."
								;;
							esac
							db_subst debian-edu-router-config/service-firewall-invalid-reverse-nat-configs reason "$reason_text"

							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-invalid-reverse-nat-configs || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi

							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-firewall-reverse-nat-configs ${FCOUNTER} 5

							# Let the user try again
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
						else
							FCOUNTER=0
						fi
					fi
					;;

				55)
					# nothing to do for SSH incoming firewall policy
					;;

				###
				### SERVICES
				###

				#
				# Service: SSH
				#

				56)
					db_get debian-edu-router-config/service-ssh-custom-port || true
					service_ssh_custom_port="${RET}"

					if [ -n "$service_ssh_custom_port" ]; then
						re='^[0-9]+$'
						if ! [[ $service_ssh_custom_port =~ $re ]] ; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-ssh-custom-port ${FCOUNTER} 5

							# Let the user try again
							STATE_DIRECTION=-1
							STATE=$(($STATE + $STATE_DIRECTION))
						else
							FCOUNTER=0
						fi
					fi
					;;

				#
				# Service: DHCP
				#

				57)
					db_get debian-edu-router-config/service-dhcp-networks-v4 || true
					service_dhcp_networks_v4="${RET}"
					;;

				58)
					db_get debian-edu-router-config/service-dhcp-networks-v6 || true
					service_dhcp_networks_v6="${RET}"
					;;

				59)
					if echo "${service_dhcp_networks_v4}" | grep -q "OpenLAN"; then
						db_get debian-edu-router-config/service-dhcp-range-v4-openlan || true
						if ! is_valid_dhcp4_range "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-dhcp-range-v4-openlan ${FCOUNTER} 5
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-syntax-invalid-dhcp-v4-range || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0

						# FIXME: further checks possible...
						#        * start address lower than end address
						#        * both addresses in same subnet
						#        * check that both addresses are in iface's subnet
						#        * etc. (?)

					fi
					;;

				60)
					if echo "${service_dhcp_networks_v4}" | grep -q "Education"; then
						db_get debian-edu-router-config/service-dhcp-range-v4-education || true
						if ! is_valid_dhcp4_range "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-dhcp-range-v4-education ${FCOUNTER} 5
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-syntax-invalid-dhcp-v4-range || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0

						# FIXME: further checks possible...
						#        * start address lower than end address
						#        * both addresses in same subnet
						#        * check that both addresses are in iface's subnet
						#        * etc. (?)

					fi
					;;

				61)
					if echo "${service_dhcp_networks_v4}" | grep -q "Mgmt"; then
						db_get debian-edu-router-config/service-dhcp-range-v4-mgmt || true
						if ! is_valid_dhcp4_range "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-dhcp-range-v4-mgmt ${FCOUNTER} 5
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-syntax-invalid-dhcp-v4-range || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0

						# FIXME: further checks possible...
						#        * start address lower than end address
						#        * both addresses in same subnet
						#        * check that both addresses are in iface's subnet
						#        * etc. (?)

					fi
					;;

				62)
					if echo "${service_dhcp_networks_v4}" | grep -q "School-Administration"; then
						db_get debian-edu-router-config/service-dhcp-range-v4-schooladministration || true
						if ! is_valid_dhcp4_range "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-dhcp-range-v4-schooladministration ${FCOUNTER} 5
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-syntax-invalid-dhcp-v4-range || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0

						# FIXME: further checks possible...
						#        * start address lower than end address
						#        * both addresses in same subnet
						#        * check that both addresses are in iface's subnet
						#        * etc. (?)

					fi
					;;

				63)
					if echo "${service_dhcp_networks_v4}" | grep -q "WiFi-Students"; then
						db_get debian-edu-router-config/service-dhcp-range-v4-wifistudents || true
						if ! is_valid_dhcp4_range "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-dhcp-range-v4-wifistudents ${FCOUNTER} 5
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-syntax-invalid-dhcp-v4-range || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0

						# FIXME: further checks possible...
						#        * start address lower than end address
						#        * both addresses in same subnet
						#        * check that both addresses are in iface's subnet
						#        * etc. (?)

					fi
					;;

				64)
					if echo "${service_dhcp_networks_v4}" | grep -q "WiFi-Teachers"; then
						db_get debian-edu-router-config/service-dhcp-range-v4-wifiteachers || true
						if ! is_valid_dhcp4_range "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-dhcp-range-v4-wifiteachers ${FCOUNTER} 5
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-syntax-invalid-dhcp-v4-range || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0

						# FIXME: further checks possible...
						#        * start address lower than end address
						#        * both addresses in same subnet
						#        * check that both addresses are in iface's subnet
						#        * etc. (?)

					fi
					;;

				65)
					if echo "${service_dhcp_networks_v4}" | grep -q "WiFi-Guests"; then
						db_get debian-edu-router-config/service-dhcp-range-v4-wifiguests || true
						if ! is_valid_dhcp4_range "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-dhcp-range-v4-wifiguests ${FCOUNTER} 5
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-syntax-invalid-dhcp-v4-range || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0

						# FIXME: further checks possible...
						#        * start address lower than end address
						#        * both addresses in same subnet
						#        * check that both addresses are in iface's subnet
						#        * etc. (?)

					fi
					;;

				66)
					if echo "${service_dhcp_networks_v4}" | grep -q "Printers"; then
						db_get debian-edu-router-config/service-dhcp-range-v4-printers || true
						if ! is_valid_dhcp4_range "${RET}"; then
							FCOUNTER=$((${FCOUNTER}+1))
							bailout_on_too_many_failures debian-edu-router-config/service-dhcp-range-v4-printers ${FCOUNTER} 5
							db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-syntax-invalid-dhcp-v4-range || true
							if ! db_go; then
								debug_log "Ignoring backup/db_go-failure..."
							fi
							continue
						fi
						FCOUNTER=0

						# FIXME: further checks possible...
						#        * start address lower than end address
						#        * both addresses in same subnet
						#        * check that both addresses are in iface's subnet
						#        * etc. (?)

					fi
					;;

				### END OF SERVICES

				# not implemented yet...
				67)
					;;

				# Used for skipping/aborting questions entirely.
				999)
					;;

			esac

			# last question was ok, so go up.
			# except if we just simulated that step...
			if [ "$BYPASS_DB_GO" == true ]; then
				STATE_DIRECTION=1
				STATE=$ORIGIN_STATE
			else
				STATE_DIRECTION=1
				STATE=$(($STATE + $STATE_DIRECTION))
			fi

			# reset.
			BYPASS_DB_GO=false
		else
			# last question was not ok (user wants to backup), so go *DOWN* a step.
			# and if the next step should be skipped, go down another step.
			# and if that step should also be skipped, go down another step.
			# and so on and so on...
			STATE_DIRECTION=-1
			STATE=$(($STATE + $STATE_DIRECTION))
			debug_log "Backing up to step ${cyan}${STATE}${green}..."
		fi
	done

	if [ $STATE -lt $BACKSTOP ]; then
		# user went backwards from beyond BACKSTOP/entry point, abort package configuration.
		debug_log "User tried to backup beyond BACKSTOP/entry point... Exiting."
		exit 10
	fi
}

function main() {
	statemachine

	# Reset, to avoid duplicate questions and looping when in STEP-BY-STEP setup mode.
	db_set debian-edu-router-config/net-setup-mode ""
}

if [[ "$1" == "configure" ]] && [[ -n "$2" ]]; then
	main
# elif [[ "$1" == "configure" ]] && [[ "$2" == "debian-edu-router-reconfigured" ]]; then
# 	debug_log "config script was called via dpkg-trigger, specifically 'debian-edu-router-reconfigured' trigger."
# 	main
elif [[ "$1" == "reconfigure" ]]; then
	debug_log "config script was called via dpkg-reconfigure."
	main
else
	debug_log "config script was probably called to preconfigure package, skipping..."
	exit 0
fi

# dh_installdeb will replace this with shell code automatically
# generated by other debhelper scripts.



debug_log "Finished .config stage of ${PACKAGE_NAME}."

exit 0