How to get a remote ip on CloudFront + Rails

config-initializers-trusted_proxies.rb

# @see https://docs.aws.amazon.com/ja_jp/AmazonCloudFront/latest/DeveloperGuide/LocationsOfEdgeServers.html
# @see https://morizyun.github.io/ruby/rails-controller-get-ip.html
# @see https://dev.classmethod.jp/cloud/aws/get-ec2-public-ip-range-by-powershell/
# @see https://github.com/rails/rails/blob/c81af6a/actionpack/lib/action_dispatch/middleware/remote_ip.rb#L112-L150
Rails.application.configure do
  ip_ranges_res = Faraday.get('https://ip-ranges.amazonaws.com/ip-ranges.json')
  ip_ranges = JSON.parse(ip_ranges_res.body)
  cloudfront_ips = ip_ranges['prefixes'].select { |v| v['service'] == 'CLOUDFRONT' }.map { |v| IPAddr.new(v['ip_prefix']) } +
                   ip_ranges['ipv6_prefixes'].select { |v| v['service'] == 'CLOUDFRONT' }.map { |v| IPAddr.new(v['ipv6_prefix']) }

  config.action_dispatch.trusted_proxies = cloudfront_ips
end