如何进行非阻塞 OpenSSL 连接？

Question

I want make a non-blocking OpenSSL connection

On this connection - if no data available for read, then entire program execution flow make stop on SSL_read(). I want so that if no data available for read it give me the returns values like WANT_READ and i know no more data available.

char *sslRead (connection *c)
{
const int readSize = 1024;
char *rc = NULL;
int r;
int received, count = 0;
int ReallocSize = 0;
char buffer[1024];

if (c)
{
    while (1)
    {
        if (!rc)
        {
            rc = malloc (readSize + 1); 
            if (rc == NULL)
                printf("the major error have happen. leave program\n");
        }
        else
        {
            ReallocSize = (count + 1) * (readSize + 1);
            rc = realloc (rc, ReallocSize);
        }

        // if i have no data available for read after reading data, 
        // this call will not return anything and wait for more data

        // i want change this non blocking connections
        received = SSL_read (c->sslHandle, buffer, readSize);

        buffer[received] = '\0';


        if (received <= 0)
        {
            printf(" received equal to or less than 0\n");
            switch (SSL_get_error(c->sslHandle, r))
            {
            case SSL_ERROR_NONE:
                printf("SSL_ERROR_NONE\n");
                break;   
            case SSL_ERROR_ZERO_RETURN: 
                printf("SSL_ERROR_ZERO_RETURN\n");
                break;   
            case SSL_ERROR_WANT_READ: 
                printf("SSL_ERROR_WANT_READ\n");
                break;
            default:
                printf("error happens %i\n", r); 
            }     
            break;
        }

        count++;
    }
}
return rc;

}

here is how i make connection

connection *sslConnect (void)
{
   connection *c;

   c = malloc (sizeof (connection));
   c->sslHandle = NULL;
   c->sslContext = NULL;

   c->socket = tcpConnect ();
   if (c->socket)
   {
    // Register the error strings for libcrypto & libssl
    SSL_load_error_strings ();
    // Register the available ciphers and digests
    SSL_library_init ();

    // New context saying we are a client, and using SSL 2 or 3
    c->sslContext = SSL_CTX_new (SSLv23_client_method ());
    if (c->sslContext == NULL)
    ERR_print_errors_fp (stderr);

    // Create an SSL struct for the connection
    c->sslHandle = SSL_new (c->sslContext);
    if (c->sslHandle == NULL)
    ERR_print_errors_fp (stderr);

    // Connect the SSL struct to our connection
    if (!SSL_set_fd (c->sslHandle, c->socket))
    ERR_print_errors_fp (stderr);

    // Initiate SSL handshake
    if (SSL_connect (c->sslHandle) != 1)
    ERR_print_errors_fp (stderr);
    }
    else
    {
     perror ("Connect failed");
    }

    return c;
}

thanks you very much.

Answer 1

Creating a non-blocking socket is a pre-requisite to a non-blocking connect...

The following steps summarize: (see complete description in site linked below)

1) Call the fcntl() API to retrieve the socket descriptor's current flag settings into a local variable.

2) In that local variable, set the O_NONBLOCK (non-blocking) flag on. (being careful not to tamper with the other flags)

3) Call the fcntl() API to set the flags for the descriptor to the value in our local variable.

( read more on non-blocking sockets techniques here )

Assuming an existing socket, the following implements the steps outlined above:

BOOL SetSocketBlockingEnabled(SOCKET fd, BOOL blocking)
{
     if (fd < 0) return FALSE;  
   #ifdef WIN32
       unsigned long mode = blocking ? 0 : 1;
       return (ioctlsocket(fd, FIONBIO, &mode) == 0) ? TRUE : FALSE;
   #else
       int flags = fcntl(fd, F_GETFL, 0);
       if (flags < 0) return false;
       flags = blocking ? (flags&~O_NONBLOCK) : (flags|O_NONBLOCK);
       return (fcntl(fd, F_SETFL, flags) == 0) ? TRUE : FALSE;
   #endif
}

Once you have a non-blocking socket, then see this post explaining how to do a non-blocking connect