SSL_accept takes 200ms (c / openssl)

Question

Is it normal that SSL_accept(ssl) takes 200 ms?

Running as a windows service, written in c++, using MFC and Boost. Running on an intel xeon e5620 2.4G, with 4GB memory, and Win 7 Pro.

Following is my code. I meanwhile suspected that maybe other methods before SSL_accept (SSL_CTX_* RAND_* etc) might consume long time , but I logged everthing and discovered that SSL_accept is eating all the time.

int verify_callback(int preverify_ok, X509_STORE_CTX *ctx)
{
    return preverify_ok;
}    
void somemethod() {    
    SSL *ssl  = 0;
    SSL_CTX *tlsctx = 0;
    int ret_conn = -1;
    tlsctx = SSL_CTX_new( SSLv23_method());

    SSL_CTX_use_certificate_file(tlsctx, sCert , SSL_FILETYPE_PEM);

    SSL_CTX_use_PrivateKey_file(tlsctx, sKey , SSL_FILETYPE_PEM);

        RAND_write_file(sRandomPem);
        int _rand_loaded = RAND_load_file(sRandomPem, -1 );   

        if(! SSL_CTX_load_verify_locations(tlsctx, sCACert, NULL))
        {
            // TODO //  /* Handle error here */     
        }
        SSL_CTX_set_verify( tlsctx, SSL_VERIFY_PEER, verify_callback );

        ssl = SSL_new(tlsctx);

        int _error = SSL_ERROR_WANT_READ;

        int loopCount  = 0;


        // START MEASURING TIME FROM HERE
        SSL_set_fd(ssl, _sck);
        while(ret_conn != 1 ) 
        {
            loopCount++;

            ret_conn = SSL_accept(ssl);

            _error = SSL_get_error(ssl, ret_conn);
            switch (_error) 
            { 
            case SSL_ERROR_NONE: 
                    break; 
            case SSL_ERROR_WANT_WRITE: 
                    break; 
            case SSL_ERROR_WANT_READ: 
                    break; 
            case SSL_ERROR_WANT_X509_LOOKUP: 
                    break; 
            case SSL_ERROR_SYSCALL: 
                    break; 
            case SSL_ERROR_SSL: 
                    break; 
            case SSL_ERROR_ZERO_RETURN: 
                    break; 
            } 

            if( _error == SSL_ERROR_WANT_READ || _error == SSL_ERROR_WANT_WRITE)
            { 
                Sleep(1);
            } else
            {
                break;
            }
        }

        if( ret_conn < 1)
        {
            Log("SSL_accept -1 ", ERR_error_string(_error, NULL));
            return;
        }
        // MEASURING END HERE, takes ~200ms (on successfully accepting connection)
}

Answer 1

To my knowledge, SSL_accept is a blocking function, which waits for your client to connect. If your client connect 200 ms later than the beginning for the SSL_accept call, then you will measure that waiting time.