class Gem::Resolv::DNS::Requester

def close
  socks = @socks
  @socks = nil
  socks&.each(&:close)
end

def initialize
  @senders = {}
  @socks = nil
end

def request(sender, tout)
  start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
  timelimit = start + tout
  begin
    sender.send
  rescue Errno::EHOSTUNREACH, # multi-homed IPv6 may generate this
         Errno::ENETUNREACH
    raise ResolvTimeout
  end
  while true
    before_select = Process.clock_gettime(Process::CLOCK_MONOTONIC)
    timeout = timelimit - before_select
    if timeout <= 0
      raise ResolvTimeout
    end
    if @socks.size == 1
      select_result = @socks[0].wait_readable(timeout) ? [ @socks ] : nil
    else
      select_result = IO.select(@socks, nil, nil, timeout)
    end
    if !select_result
      after_select = Process.clock_gettime(Process::CLOCK_MONOTONIC)
      next if after_select < timelimit
      raise ResolvTimeout
    end
    begin
      reply, from = recv_reply(select_result[0])
    rescue Errno::ECONNREFUSED, # GNU/Linux, FreeBSD
           Errno::ECONNRESET # Windows
      # No name server running on the server?
      # Don't wait anymore.
      raise ResolvTimeout
    end
    begin
      msg = Message.decode(reply)
    rescue DecodeError
      next # broken DNS message ignored
    end
    if sender == sender_for(from, msg)
      break
    else
      # unexpected DNS message ignored
    end
  end
  return msg, sender.data
end

def sender_for(addr, msg)
  @senders[[addr,msg.id]]
end