class ActionDispatch::RemoteIp::GetIp

def ips_from(header) # :doc:
  return [] unless header
  # Split the comma-separated list into an array of strings.
  ips = header.strip.split(/[,\s]+/)
  ips.select! do |ip|
    # Only return IPs that are valid according to the IPAddr#new method.
    range = IPAddr.new(ip).to_range
    # We want to make sure nobody is sneaking a netmask in.
    range.begin == range.end
  rescue ArgumentError
    nil
  end
  ips
end