vpnclient_ynh/conf/scripts/route-up.d/30-vpnclient-set-server-ipv6-route

#!/bin/bash

is_serverip6route_set() {
  local server_ip6=${1}

  if [[ -z "${server_ip6}" ]]; then
    return 0
  fi

  if ! ip -6 route | grep -q "^${server_ip6}"; then
    return 1
  fi
}

set_serverip6route() {
  local server_ip6=${1}
  local ip6_gw=${2}
  local wired_device=${3}

  ip route add "${server_ip6}/128" via "${ip6_gw}" dev "${wired_device}"
}

wired_device=$(ip route | awk '/default via/ { print $5; }')

# See https://openvpn.net/community-resources/reference-manual-for-openvpn-2-4/#environmental-variables
# to have a list of variables provided by OpenVPN, i.e:
# - ifconfig_ipv6_remote
# - net_gateway_ipv6

echo "[INFO] Autodetected internet interface: ${wired_device}"
if [[ -n "${ifconfig_ipv6_remote}" ]]; then
  echo "[INFO] Autodetected IPv6 address for the VPN server: ${ifconfig_ipv6_remote}"
else
  echo "[INFO] No IPv6 address for the VPN server detected"
  echo "[INFO] No IPv6 route set"
  exit 0
fi

# Set the new server ipv6 route
if [[ -n "${net_gateway_ipv6}" ]]; then
  if ! is_serverip6route_set "${ifconfig_ipv6_remote}"; then
    set_serverip6route "${ifconfig_ipv6_remote}" "${net_gateway_ipv6}" "${wired_device}"
  fi

  echo "[INFO] Native IPv6 detected"
  echo "[INFO] Autodetected native IPv6 gateway: ${net_gateway_ipv6}"

  if is_serverip6route_set "${ifconfig_ipv6_remote}"; then
    echo "[ OK ] IPv6 server route correctly set"
  else
    echo "[FAIL] No IPv6 server route set" >&2
    exit 1
  fi
else
  echo "[INFO] No native IPv6 detected"
  echo "[INFO] No IPv6 server route to set"
fi