vpnclient_ynh/conf/scripts/route-up.d/40-vpnclient-set-ipv6

#!/bin/bash

is_ip6addr_set() {
  local ip6_addr=${1}
  ip address show dev "${gateway_interface}" 2> /dev/null | grep -q "${ip6_addr}/"
}

ip6_addr=$(yunohost app setting "vpnclient" "ip6_addr")
# cf https://openvpn.net/community-resources/reference-manual-for-openvpn-2-4/#environmental-variables for where 'dev' comes from
gateway_interface=${dev}

if [[ -n "${ip6_addr}" ]] && [[ "${ip6_addr}" != none ]]; then
  if ! is_ip6addr_set "${ip6_addr}"; then
    ip address add "${ip6_addr}/64" dev "${gateway_interface}"
  fi

  echo "[INFO] IPv6 delegated prefix found"
  echo "[INFO] IPv6 address computed from the delegated prefix: ${ip6_addr}"

  if is_ip6addr_set "${ip6_addr}"; then
    echo "[ OK ] IPv6 address correctly set"
  else
    echo "[FAIL] No IPv6 address set" >&2
    exit 1
  fi
else
  echo "[INFO] No IPv6 delegated prefix found"
fi