Enable IPv6s on DigitalOcean

sh

#!/bin/bash -eu
# https://docs.digitalocean.com/products/networking/reserved-ips/how-to/manually-enable/#enable-reserved-ipv6

IFACE_ETH0="eth0"
IFACE_LO="lo"
PREFIX_LEN="128"

# get Droplet metadata
md=$(curl -s 169.254.169.254/metadata/v1.json)

# get reserved IPv6 info from metadata
md_rip6_json=$(echo "${md}" | jq -r '.reserved_ip.ipv6')

case "$(echo "${md_rip6_json}" | jq -r '.active')" in
    "true")
        # if active, set up interface and routes
        rip6=$(echo "${md_rip6_json}" | jq -r '.ip_address')
        ip -6 addr replace "${rip6}/${PREFIX_LEN}" dev ${IFACE_LO} scope global
        echo "Assigned ${rip6}/${PREFIX_LEN} to ${IFACE_LO}"
        ip -6 route replace default dev ${IFACE_ETH0}
        echo "Created default IPv6 route via ${IFACE_ETH0}"
        ;;

    "false")
        # if inactive, clean up interface and routes
        ip -6 addr flush dev ${IFACE_LO} scope global
        echo "Removed all Reserved IPv6 addresses from ${IFACE_LO}"
        # technically, the route can remain even beyond removal,
        # but to keep consistency with existing behavior without
        # a reserved IPv6, we'll clean it up
        if [[ "$(ip -6 route show default dev ${IFACE_ETH0})" != "" && "$(ip -6 addr show dev ${IFACE_ETH0} scope global)" == "" ]]; then
            ip -6 route delete default dev ${IFACE_ETH0}
            echo "Deleted default IPv6 route via ${IFACE_ETH0}"
        fi
        ;;
esac

The script checks if the Droplet has a reserved IPv6 assigned. If it does, the script assigns it to the lo network interface and configures routing rules to allow traffic flow. If the Droplet does not have a reserved IPv6 assigned, the script removes any existing reserved IPv6 addresses from the lo interface and cleans up related routes.

The script requires jq and curl. Run the script directly on the command line to verify it is functioning properly, then create a cron job or systemd timer to run it periodically.