/etc/openvpn/update-systemd-resolved

update-systemd-resolved

#!/bin/bash
#
# This script configures DNS settings for OpenVPN using systemd-resolved
# It uses D-Bus via busctl to communicate with systemd-resolved
# Ensure that systemd-resolved is running before using this script.
# Place this script at: /etc/openvpn/update-systemd-resolved
#
# Example OpenVPN config usage:
# up /etc/openvpn/update-systemd-resolved
# down /etc/openvpn/update-systemd-resolved
#

# Exit if any command fails
set -e

# Validate environment variables
if [ -z "$script_type" ] || [ -z "$dev" ]; then
    logger "[OpenVPN] Missing script_type or dev environment variables"
    exit 1
fi

# Split DHCP option string into components
split_into_parts() {
    part1="$1"
    part2="$2"
    part3="$3"
}

# Configure DNS and search domains in systemd-resolved
configure_systemd_resolved() {
    # Check if systemd-resolved is running
    if ! busctl --no-pager list | grep -q 'org.freedesktop.resolve1'; then
        logger "[OpenVPN] systemd-resolved is not running"
        exit 1
    fi

    local DNS_SERVERS=()
    local SEARCH_DOMAINS=()

    # Parse foreign_option_* variables
    foreign_options=$(printf '%s\n' ${!foreign_option_*} | sort -t _ -k 3 -g)
    for optionvarname in ${foreign_options}; do
        option="${!optionvarname}"
        split_into_parts $option
        if [ "$part1" = "dhcp-option" ]; then
            if [ "$part2" = "DNS" ]; then
                DNS_SERVERS+=("$part3")
            elif [ "$part2" = "DOMAIN" ]; then
                SEARCH_DOMAINS+=("$part3")
            fi
        fi
    done

    # Set DNS servers
    if [ ${#DNS_SERVERS[@]} -gt 0 ]; then
        busctl call org.freedesktop.resolve1 /org/freedesktop/resolve1 org.freedesktop.resolve1.Manager SetLinkDNS \
            "ia(iay)" "$dev" "${#DNS_SERVERS[@]}" $(for dns in "${DNS_SERVERS[@]}"; do echo "(iay) 2 1 $dns 0"; done)
    fi

    # Set search domains
    if [ ${#SEARCH_DOMAINS[@]} -gt 0 ]; then
        busctl call org.freedesktop.resolve1 /org/freedesktop/resolve1 org.freedesktop.resolve1.Manager SetLinkDomains \
            "ia(sb)" "$dev" "${#SEARCH_DOMAINS[@]}" $(for domain in "${SEARCH_DOMAINS[@]}"; do echo "(sb) $domain 0"; done)
    fi
}

# Clear DNS and search domain settings in systemd-resolved
clear_systemd_resolved() {
    # Revert DNS settings for the network device
    if busctl call org.freedesktop.resolve1 /org/freedesktop/resolve1 org.freedesktop.resolve1.Manager RevertLink "i" "$dev"; then
        logger "[OpenVPN] Cleared DNS settings for $dev"
    else
        logger "[OpenVPN] Failed to clear DNS settings for $dev"
    fi
}

# Execute the appropriate action based on script type (up or down)
case "$script_type" in
    up)
        configure_systemd_resolved
        ;;
    down)
        clear_systemd_resolved
        ;;
    *)
        logger "[OpenVPN] Unknown script_type: $script_type"
        exit 1
        ;;
esac