hijack.rb

def stream(socket)
  curl = Curl::Easy.new(url)

  curl.on_body   { |data| socket.write(data) }
  curl.on_header { |data| socket.write(data) }

  curl.multipart_form_post = true
  curl.http_post
end

def hijack
  request.env['rack.hijack'].call
  socket = request.env['rack.hijack_io']
  Thread.new do
    begin
      stream(socket)
    ensure
      socket.close
    end
  end
end