perform_proxy_request

# File lib/webrick/httpproxy.rb, line 273
    def perform_proxy_request(req, res)
      uri = req.request_uri
      path = uri.path.dup
      path << "?" << uri.query if uri.query
      header = setup_proxy_header(req, res)
      upstream = setup_upstream_proxy_authentication(req, res, header)
      response = nil

      http = Net::HTTP.new(uri.host, uri.port, upstream.host, upstream.port)
      http.start do
        if @config[:ProxyTimeout]
          ##################################   these issues are
          http.open_timeout = 30   # secs  #   necessary (maybe bacause
          http.read_timeout = 60   # secs  #   Ruby's bug, but why?)
          ##################################
        end
        response = yield(http, path, header)
      end

      # Persistent connection requirements are mysterious for me.
      # So I will close the connection in every response.
      res['proxy-connection'] = "close"
      res['connection'] = "close"

      # Convert Net::HTTP::HTTPResponse to WEBrick::HTTPResponse
      res.status = response.code.to_i
      choose_header(response, res)
      set_cookie(response, res)
      set_via(res)
      res.body = response.body
    end