DIY dDNS service script using Hetzner's DNS API

update-ddns.rb

#!/usr/bin/env ruby
#
# Original, including IsoLinearCHiP's improvements: https://gist.github.com/IsoLinearCHiP/d6bc594143102e6acd131fc65c080f64
# Current version, adapted to Hetzner phasing out dns.h.d for console.h.d
# now maintained at https://gist.weitnahbei.de/sixtyfive/7b090861f8e44a8ba3b37c9cde93c3af

API="https://api.hetzner.cloud/v1"

require 'json'
require 'socket'
require 'net/http'
require 'fileutils'
require 'pstore'

FileUtils.mkdir_p "#{Dir.home}/.local/share/update-ddns"
@pstore = PStore.new "#{Dir.home}/.local/share/update-ddns/cache.pstore"

def api(path, records=nil)
  if records
    cmd = "curl -s -X POST -H 'Authorization: Bearer #{@token}' -H 'Content-Type: application/json' -d '{\"records\": #{records.to_json}}' #{API}#{path}"
    `#{cmd}`
  else
    cmd = "curl -s -H 'Authorization: Bearer #{@token}' #{API}#{path}"
    JSON.parse `#{cmd}`
  end
end

def cache(key, value=nil)
  if value
    @pstore.transaction{@pstore[key] = value}
  end
  @pstore.transaction(true){return @pstore[key]}
end

def current_wan_ip
  Socket.getifaddrs
    .map{|iface| [iface.name, iface.addr.ip_address] if iface.addr.ipv4? if iface.addr}
    .compact
    .find{|x| x[0]=='ppp0'}[1]
end

def query
  @token = cache('api_token')
  zone = ARGV[0]
  rrset_name = ARGV[1]
  zone_id = cache('zone_id')
  zone_id ||= cache('zone_id', api('/zones')['zones'].find{|x| x['name'] == @zone}['id'])
  wan_ip = cache('current_wan_ip', current_wan_ip)
  puts wan_ip
  ips_on_record = api("/zones/#{zone_id}/rrsets/#{rrset_name}/A")['rrset']['records'].collect{|x| x['value']}
  if ips_on_record.last != wan_ip
    api("/zones/#{zone_id}/rrsets/#{rrset_name}/A/actions/set_records", [{value: wan_ip, comment: 'dynamically updated'}])
    puts "record updated"
  else
    puts "no update necessary"
  end
end

case ARGV.size
  when 1
    cache('api_token', ARGV[0])
    puts "API token set"
  when 2
    (warn "Error: API token not set"; exit!) unless cache('api_token')
    query
  else
    warn "Usage: update-ddns <zone> <record> | update-ddns <api token>"
    exit!
end