#!/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

# Load common functions, variables and stuff.
if [ -s "/usr/share/debian-edu-router-config/debian-edu-router-config.common" ]; then
	source /usr/share/debian-edu-router-config/debian-edu-router-config.common
else
	exit 0;
fi

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
	not_d_e_r_files+=(/etc/network/interfaces)

	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 $_return_ifaces: All interfaces with desired online status seperated
#                          by spaces.
function filter_ifaces_by_online_status() {
	_ifaces_connected=(${@: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 ${iface}"
		else
			iface_description=`udevadm info /sys/class/net/${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
}

function bailout_on_too_many_failures() {
	if [ ${2} -ge ${3} ]; then
		error_log "Value for '${1}' has been answered insufficiently for too many (${3}) times."
		exit 1
	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.
#
# Without these two lines, firewall and service configuration will not work
# correctly and most debconf dialogs will be skipped.
ipv4_enabled && IPV4=true
ipv6_enabled && IPV6=true
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 [ "${CONFIGURE_ONLY}" = "SERVICES_ALL" ]; then
	STATE=56
	QCOUNT=67
elif [ "${CONFIGURE_ONLY}" = "SERVICE_DHCP" ]; then
	STATE=56
	QCOUNT=65
elif [ "${CONFIGURE_ONLY}" = "SERVICE_SSH" ]; then
	STATE=66
	QCOUNT=66
elif [ "${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}

if [ "$D_E_R_DEBUG" != "" ]; then
	echo -e "${green}debian-edu-router-config.config:${normal}"
	echo -e "${green}CONFIGURE_ONLY=${cyan}${CONFIGURE_ONLY}${normal}"
	echo -e "${green}STATE=         ${cyan}${STATE}${normal}"
	echo -e "${green}QCOUNT=        ${cyan}${QCOUNT}${normal}"
	echo -e "${green}BACKSTOP=      ${cyan}${BACKSTOP}${normal}"
fi

# 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 skip-networking flag 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

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

				nic_choices=""
				while [ -z "${nic_choices}" ]; 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

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

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

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

				debug_log "${green}Simulating step ${cyan}$STATE" \
						  "${green}to get data needed by step ${cyan}${now_state}${normal}"
			else
				db_subst debian-edu-router-config/net-ext-iface-uplink choices "${nic_choices}"
				nic_choices_description_extended=$(available_network_interfaces_description_extended "${nic_choices}")
				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
			;;
		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
				# Prevent asking this question if vlans shouldn't be configured.
				STATE=$(($STATE + $STATE_DIRECTION))
				continue
			fi

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

				db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-connect-int-iface-vlan || true
				db_go || true

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

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

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

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

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

				debug_log "${green}Simulating step ${cyan}$STATE" \
						  "${green}to get data needed by step ${cyan}${now_state}${normal}"
			else
				db_subst debian-edu-router-config/net-int-supportednetworks-via-vlan choices "${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

				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
						debug_log "Ignoring backup/db_go-failure…"
					fi

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

				fi

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

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

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-trying 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						if [ "$FCOUNTER" -ge 5 ]; then
							# Reset current d-e-r configuration progress.
							db_set debian-edu-router-config/net-setup-mode ""
							STATE="$NETWORK_SETUP_QUESTION"
							continue
						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

				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
						debug_log "Ignoring backup/db_go-failure…"
					fi

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

				fi


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

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

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-trying 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						if [ "$FCOUNTER" -ge 5 ]; then
							# Reset current d-e-r configuration progress.
							db_set debian-edu-router-config/net-setup-mode ""
							STATE="$NETWORK_SETUP_QUESTION"
							continue
						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

				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
						debug_log "Ignoring backup/db_go-failure…"
					fi

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

				fi

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

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

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-trying 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						if [ "$FCOUNTER" -ge 5 ]; then
							# Reset current d-e-r configuration progress.
							db_set debian-edu-router-config/net-setup-mode ""
							STATE="$NETWORK_SETUP_QUESTION"
							continue
						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

				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
						debug_log "Ignoring backup/db_go-failure…"
					fi

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

				fi

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

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

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-trying 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						if [ "$FCOUNTER" -ge 5 ]; then
							# Reset current d-e-r configuration progress.
							db_set debian-edu-router-config/net-setup-mode ""
							STATE="$NETWORK_SETUP_QUESTION"
							continue
						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

				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
						debug_log "Ignoring backup/db_go-failure…"
					fi

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

				fi

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

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

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-trying 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						if [ "$FCOUNTER" -ge 5 ]; then
							# Reset current d-e-r configuration progress.
							db_set debian-edu-router-config/net-setup-mode ""
							STATE="$NETWORK_SETUP_QUESTION"
							continue
						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

				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
						debug_log "Ignoring backup/db_go-failure…"
					fi

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

				fi

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

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

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-trying 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						if [ "$FCOUNTER" -ge 5 ]; then
							# Reset current d-e-r configuration progress.
							db_set debian-edu-router-config/net-setup-mode ""
							STATE="$NETWORK_SETUP_QUESTION"
							continue
						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

				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
						debug_log "Ignoring backup/db_go-failure…"
					fi

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

				fi

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

					debug_log "${green}Simulating step ${cyan}$STATE" \
							  "${green}to get data needed by step ${cyan}${now_state}${normal}"
				else
					nic_choices=$(filter_iface debian-edu-router-config/net-ext-iface-uplink ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-openlan ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-education ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-mgmt ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-schooladministration ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-wifistudents ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-wifiteachers ${nic_choices})

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-trying 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						if [ "$FCOUNTER" -ge 5 ]; then
							# Reset current d-e-r configuration progress.
							db_set debian-edu-router-config/net-setup-mode ""
							STATE="$NETWORK_SETUP_QUESTION"
							continue
						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

				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
						debug_log "Ignoring backup/db_go-failure…"
					fi

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

				fi

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

					debug_log "${green}Simulating step ${cyan}$STATE" \
							  "${green}to get data needed by step ${cyan}${now_state}${normal}"
				else
					nic_choices=$(filter_iface debian-edu-router-config/net-ext-iface-uplink ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-openlan ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-education ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-mgmt ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-schooladministration ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-wifistudents ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-wifiteachers ${nic_choices})
					nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-wifiguests ${nic_choices})

					if [ -z "${nic_choices}" ]; then
						# An empty choice is not acceptable here, tolerate re-trying 5 times
						FCOUNTER=$((${FCOUNTER}+1))
						if [ "$FCOUNTER" -ge 5 ]; then
							# Reset current d-e-r configuration progress.
							db_set debian-edu-router-config/net-setup-mode ""
							STATE="$NETWORK_SETUP_QUESTION"
							continue
						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_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 + $STATE_DIRECTION)); continue; fi
			db_subst debian-edu-router-config/net-networks-dhcpclient-v4 choices "${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_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_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-address-v4-uplink || true
			else
				STATE=$(($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_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-address-v6-uplink || true
			else
				STATE=$(($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_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-gateway-v4-uplink || true
			else
				STATE=$(($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_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-gateway-v6-uplink || true
			else
				STATE=$(($STATE + $STATE_DIRECTION))
				continue
			fi
			;;

		33)
			db_input ${DC_PRIO_HIGH} debian-edu-router-config/net-ext-nameservers-uplink || true
			;;

		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}"

			compare_comma_separated_items "${supported_internal_networks}" "${service_firewall_networks_allow_internet}"
			unequal_items="${RES}"

			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 "Uplink, ${supported_internal_networks}"
			db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-firewall-ssh-incoming || true
			;;

		###
		### SERVICES:
		###

		### Service: DHCP

		56)
			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
			;;

		57)
			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
			;;

		58)
			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
			;;

		59)
			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
			;;

		60)
			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
			;;

		61)
			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
			;;

		62)
			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
			;;

		63)
			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
			;;

		64)
			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
			;;

		65)
			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
			;;

		#
		# SSH
		#

		66)
			# Asking port for SSH services
			db_input ${DC_PRIO_HIGH} debian-edu-router-config/service-ssh-custom-port || true
			;;

		### END OF SERVICES

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

		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 [ "${net_setup_mode}" = "OFFLINE-SETUP" ]; then
						nic_choices=$(available_network_interfaces_offline)
					elif [ "${net_setup_mode}" = "ALL-CONNECTED" ]; then
						nic_choices=$(available_network_interfaces_online)
					elif [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
						# delay checking number of online interfaces
						# be content with offline interfaces for now
						nic_choices=$(available_network_interfaces_offline)
					fi
				fi

				# we need at least two network interfaces
				if ! echo "${nic_choices}" | 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…"
						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…"
						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_iface debian-edu-router-config/net-ext-iface-uplink ${nic_choices})

				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}"
				FCOUNTER=0
				;;
			4)
				db_get debian-edu-router-config/net-int-with-vlans
				if [ "${RET}" = "false" ]; then
					STATE=$((${NETWORK_SETUP_SKIP_VLAN}-1))
				fi
				;;
			5)
				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-vlan ${nic_choices})

				if [ "${net_setup_mode}" = "STEP-BY-STEP" ]; then
					db_subst debian-edu-router-config/net-int-iface-vlan-assigned iface "${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}"
				FCOUNTER=0

#				# FIXME: find a good if-clause condition for this
#				# FIXME: Update this with debian-edu-router-config/skip-networking-if-not-enough-ifaces-non-configured
#				if [ not enough network interfaces for the number of networks ]; then
#					db_set debian-edu-router-config/skip-networking-if-not-enough-ifaces-available true
#					# skip network setup, not enough interfaces available
#					db_input $DC_PRIO_HIGH debian-edu-router-config/skip-networking-if-not-enough-ifaces-available || true
#					db_go
#					db_get debian-edu-router-config/skip-networking-if-not-enough-ifaces-available
#					if [ "${RET}" = false ]; then
#						STATE=1
#						continue
#					else
#						STATE=999
#					fi
#				fi

				;;
			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

				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-openlan ${nic_choices})

				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 ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-openlan-assigned || true
					if ! db_go; then
						debug_log "Ignoring backup/db_go-failure…"
					fi
				fi
				;;
			16)
				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-education ${nic_choices})

				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 ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-education-assigned || true
					if ! db_go; then
						debug_log "Ignoring backup/db_go-failure…"
					fi
				fi
				;;
			17)
				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-mgmt ${nic_choices})

				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 ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-mgmt-assigned || true
					if ! db_go; then
						debug_log "Ignoring backup/db_go-failure…"
					fi
				fi
				;;
			18)
				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-schooladministration ${nic_choices})

				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 ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-schooladministration-assigned || true
					if ! db_go; then
						debug_log "Ignoring backup/db_go-failure…"
					fi
				fi
				;;
			19)
				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-wifistudents ${nic_choices})

				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 ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifistudents-assigned || true
					if ! db_go; then
						debug_log "Ignoring backup/db_go-failure…"
					fi
				fi
				;;
			20)
				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-wifiteachers ${nic_choices})

				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 ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifiteachers-assigned || true
					if ! db_go; then
						debug_log "Ignoring backup/db_go-failure…"
					fi
				fi
				;;
			21)
				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-wifiguests ${nic_choices})

				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 ${DC_PRIO_HIGH} debian-edu-router-config/net-int-iface-wifiguests-assigned || true
					if ! db_go; then
						debug_log "Ignoring backup/db_go-failure…"
					fi
				fi
				;;
			22)
				nic_choices=$(filter_iface debian-edu-router-config/net-int-iface-printers ${nic_choices})

				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

				IPV4=false
				IPV6=false
				for version in $(echo "${RET}" | sed -e 's/,//g'); do
					if [ "$version" == "IPv4" ]; then
						IPV4=true
					elif [ "$version" == "IPv6" ]; then
						IPV6=true
					else
						echo "debian-edu-router-config.config: IP version '$version' is not supported."
						exit 1
					fi
				done
				;;

			###
			### 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
						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
				;;

			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
					# 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="$_internal_network"
									#	break
									# fi
								fi
							else
								echo "Found invalid internal network '$_internal_network'!"
								echo "This definitely shouldn't be possible. Aborting configuration now."
								echo "Run 'dpkg-configure debian-edu-router-config' from the"
								echo "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: DHCP

			56)
				db_get debian-edu-router-config/service-dhcp-networks-v4 || true
				service_dhcp_networks_v4="${RET}"
				;;

			57)
				db_get debian-edu-router-config/service-dhcp-networks-v6 || true
				service_dhcp_networks_v6="${RET}"
				;;

			58)
				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
				;;

			59)
				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
				;;

			60)
				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
				;;

			61)
				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
				;;

			62)
				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
				;;

			63)
				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
				;;

			64)
				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
				;;

			65)
				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
				;;

			
			#
			# SSH
			#

			66)
				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
				;;

			### END OF SERVICES

			# not implemented yet...
			67)
				;;

		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

debug_log "Finishing debian-edu-router-config.config file…"

exit 0