How do you do timed-out persistent/keep alive SSL connections with blocking sockets?

A previous question asked if changing one line of code implemented persistent SSL connections. After seeing that question's responses, and checking the dearth of SSL documentation, the following appear true:

• for the server, a persistent connection is simply doing repeated requests/responses between SSL_accept() and SSL_set_shutdown().

• according to this page, the client has to indicate how many requests there will be by sending the appropriate "Content-length:" header or using an agreed-upon terminating request.

However, there's no guarantee the client will send what it's supposed to. Therefore, it would seem a server using blocking sockets can hang indefinitely on a SSL_read() while waiting for additional requests that never arrive. (SSL_CTX_set_timeout() doesn't appear to cause a subsequent SSL_read() to exit early, so it's not clear how to do timed-out connections as described at this Wikipedia page if sockets are blocking.)

Apparently, a server can indicate it won't do keep-alive by returning a "Connection: Close" header with a response, so I've ended up with the following code, which at least should always correctly do a single request/response per connection:

while TRUE do
  begin  // wait for incoming TCP connection
  if notzero(listen(listen_socket, 100)) then continue; // listen failed
  client_len := SizeOf(sa_cli);
  sock := accept(listen_socket, @sa_cli, @client_len); // create socket for connection
  if sock = INVALID_SOCKET then continue; // accept failed
  ssl := SSL_new(ctx); // TCP connection ready, create ssl structure
  if assigned(ssl) then
    begin
    SSL_set_fd(ssl, sock); // assign socket to ssl structure
    if SSL_accept(ssl) = 1 then // handshake worked
      begin
      request := '';
      repeat // gather request
        bytesin := SSL_read(ssl, buffer, sizeof(buffer)-1);
        if bytesin > 0 then
          begin
          buffer[bytesin] := #0;
          request := request + b开发者_JS百科uffer;
          end;
      until SSL_pending(ssl) <= 0;
      if notempty(request) then
        begin // decide on response, avoid keep-alive
        response := 'HTTP/1.0 200 OK'#13#10'Connection: Close'#13#10 + etc;
        SSL_write(ssl, pchar(response)^, length(response));
        end; // else read empty or failed
      end; // else handshake failed
    SSL_set_shutdown(ssl, SSL_SENT_SHUTDOWN or SSL_RECEIVED_SHUTDOWN);
    CloseSocket(sock);
    SSL_free(ssl);
    end; // else ssl creation failed
  end; // infinite while

Two questions:

(1) Since SSL_accept() must be true to reach SSL_read(), is it true SSL_read() can never hang waiting for the first request?

(2) How should this code be modified to do timed-out persistent/keep alive SSL connections with blocking sockets (if that's even possible)?

---

To quote this letter, "The only way to ensure that indefinite blocking is avoided is to use nonblocking I/O." So, I guess I'll give up trying to timeout blocked SSL_read()s.

---

(1) if the client connects but does not send a request (DoS attack, for instance), then SSL_read() would hang.

(2) try calling setsockopt(SO_RCVTIMEO) on the accepted SOCKET to set a reading timeout on it.