pihole_dns4_sync

#!/bin/bash

###########################################################################

# pihole_dns4_sync

# In a dual Pi-hole setup, this script fetches the IPv6 of the remote Pi-hole
# at sets it as the custom DNS4 setting (using port 5353) on the local Pi-hole.
# This is useful in configurations where the Pi-holes use Unbound as a local
# resolver on a LAN with dynamic IPv6 addressing.

# REQUIREMENTS
# Two Pi-holes on the same LAN with functioning IPv6 addresses.
# Both Pi-holes running Unbound as a local DNS resolver on port 5353.
# SSH key-based authentication (login without password) configured so the
#    local Pi-hole server running this script can log into the remote Pi-hole
#    without a password. See:
#    https://www.raspberrypi.org/documentation/remote-access/ssh/passwordless.md

# Version 1.0 - Mar 24, 2019 - Steve Jenkins (stevejenkins.com)
# Original version of script

# USAGE
# You can run ./pihole_dns4_sync from the command line, or run it
# hourly by adding the following to your crontab:

# @hourly /usr/local/bin/pihole-utils/pihole_dns4_sync > /dev/null 2>&1 #Sync dual Pi-hole IPv6 DNS4 config

###########################################################################
# USER-CONTROLLED OPTIONS
LOCAL_PIHOLE_CONFIG=/etc/pihole/setupVars.conf
REMOTE_PIHOLE_USER=root
REMOTE_PIHOLE_HOST=192.168.1.106
UNBOUND_PORT=5353
# REMEMBER TO SET UP SSH KEYS SO THIS HOST CAN SSH TO OTHER PIHOLE WITHOUT PASSWORD!
###########################################################################

# Only used for debugging
# set -x

# Copy remote Pi-hole's setupVars.conf to temp folder
printf "Fetching remote Pi-hole setupVars.conf...\n"
scp "$REMOTE_PIHOLE_USER"@"$REMOTE_PIHOLE_HOST":/etc/pihole/setupVars.conf /tmp/setupVars.remote

printf "\nComparing remote IPv6 address to local custom DNS4 entry...\n"

# Check remote IPv6 address configured in Pi-hole
pihole_ipv6_remote=$(grep IPV6_ADDRESS < /tmp/setupVars.remote | awk -F '=' '{print $2}')
printf "Remote Pi-hole IPv6 address: %s\n" "$pihole_ipv6_remote"

# Check local IPv6 address configured in Pi-hole
dns4_ipv6_local=$(grep PIHOLE_DNS_4 < ${LOCAL_PIHOLE_CONFIG} | awk -F '=' '{print $2}' | awk -F '#' '{print $1}')
printf "Local Pi-hole custom DNS4:   %s\n" "$dns4_ipv6_local"

if [ "$pihole_ipv6_remote" = "$dns4_ipv6_local" ]; then
	printf "\nIPv6 addresses match! No action required.\n"
	exit 1
else
	# Update the DNS4 entry in /etc/setupVars.conf with the remote Pi-hole's IPv6 address on Unbound port
	printf '\nAddresses do not match! Updating Pi-hole configuration...\n'
	grep -q 'PIHOLE_DNS_4' ${LOCAL_PIHOLE_CONFIG} && sed -i "s/PIHOLE_DNS_4=.*/PIHOLE_DNS_4=${pihole_ipv6_remote}#${UNBOUND_PORT}/" ${LOCAL_PIHOLE_CONFIG} || echo "PIHOLE_DNS_4=${pihole_ipv6_remote}#5353" >> ${LOCAL_PIHOLE_CONFIG}


	# Run pihole -g to pick up changes
    	printf '\nReloading Pi-hole...\n\n'
    	pihole -g

	# All done!
    	printf '\nDone!\n'
    	exit 1
fi