C - BIO_get_fd（）始终无法获得有效的FD(C - BIO_get_fd() always fails to get a valid FD)

 为什么BIO_get_fd（）总是无法在下面的代码中获得有效的FD？ 
 
SSL *pSsl = NULL;

int nRet;
int fdSocket;
fd_set connectionfds;
struct timeval timeout;

BIO_get_ssl(pBio, &pSsl);
if (!pSsl)
    // failed to get SSL pointer of BIO.

SSL_set_mode(pSsl, SSL_MODE_AUTO_RETRY);

BIO_set_conn_hostname(pBio, "HostName");
BIO_set_conn_port(pBio, "PortNumber");

BIO_set_nbio(pBio, 1);

nRet = BIO_do_connect(pBio);

if ((nRet <= 0) && !BIO_should_retry(pBio))
    // failed to establish connection.

if (BIO_get_fd(pBio, &fdSocket) <= 0)
    // failed to get fd but why?

if (nRet <= 0)
{
    FD_ZERO(&connectionfds);
    FD_SET(fdSocket, &connectionfds);

    timeout.tv_usec = 0;
    timeout.tv_sec = 10;

    nRet = select(fdSocket + 1, NULL, &connectionfds, NULL, &timeout);
    if (nRet == 0)
        // timeout has occurred.
}
 
 
 
 通过调用BIO * BIO_new_ssl_connect（SSL_CTX * ctx）预先正确创建我的BIO对象 
 
 
 我的OpenSSL版本是v1.0.1e 
 
 
 我在Ubuntu for ARM上进行交叉编译 
 

Why does BIO_get_fd() always fail to get a valid FD in the following piece of code?
 
SSL *pSsl = NULL;

int nRet;
int fdSocket;
fd_set connectionfds;
struct timeval timeout;

BIO_get_ssl(pBio, &pSsl);
if (!pSsl)
    // failed to get SSL pointer of BIO.

SSL_set_mode(pSsl, SSL_MODE_AUTO_RETRY);

BIO_set_conn_hostname(pBio, "HostName");
BIO_set_conn_port(pBio, "PortNumber");

BIO_set_nbio(pBio, 1);

nRet = BIO_do_connect(pBio);

if ((nRet <= 0) && !BIO_should_retry(pBio))
    // failed to establish connection.

if (BIO_get_fd(pBio, &fdSocket) <= 0)
    // failed to get fd but why?

if (nRet <= 0)
{
    FD_ZERO(&connectionfds);
    FD_SET(fdSocket, &connectionfds);

    timeout.tv_usec = 0;
    timeout.tv_sec = 10;

    nRet = select(fdSocket + 1, NULL, &connectionfds, NULL, &timeout);
    if (nRet == 0)
        // timeout has occurred.
}
 
 
 
My BIO object is properly created beforehand by calling BIO *BIO_new_ssl_connect(SSL_CTX *ctx)
 
 
My OpenSSL version is v1.0.1e
 
 
I'm cross-compiling on Ubuntu for ARM
 

原文：https://stackoverflow.com/questions/16652246