如何在OpenSSL中设置连接超时和操作超时

libcurl 有超时选项像这些：

CURLOPT_CONNECTTIMEOUT - maximum time in seconds that you allow the connection to the server to take.
CURLOPT_TIMEOUT - maximum time in seconds that you allow the libcurl transfer operation to take.

我想在 OpenSSL 中实现类似的超时机制。

下面的代码需要进行哪些更改才能将超时值应用于 BIO_do_connect()、BIO_write() 和 BIO_read()？

我正在连接到服务器并使用 OpenSSL 提供的 BIO_write()/BIO_read() 向服务器发送数据/从服务器接收数据。我的代码基于以下示例代码here.

int main()
{
    BIO * bio;
    SSL * ssl;
    SSL_CTX * ctx;

    int p;

    char * request = "GET / HTTP/1.1\x0D\x0AHost: www.verisign.com\x0D\x0A\x43onnection: Close\x0D\x0A\x0D\x0A";
    char r[1024];

    /* Set up the library */

    ERR_load_BIO_strings();
    SSL_load_error_strings();
    OpenSSL_add_all_algorithms();

    /* Set up the SSL context */

    ctx = SSL_CTX_new(SSLv23_client_method());

    /* Load the trust store */

    if(! SSL_CTX_load_verify_locations(ctx, "TrustStore.pem", NULL))
    {
        fprintf(stderr, "Error loading trust store\n");
        ERR_print_errors_fp(stderr);
        SSL_CTX_free(ctx);
        return 0;
    }

    /* Setup the connection */

    bio = BIO_new_ssl_connect(ctx);

    /* Set the SSL_MODE_AUTO_RETRY flag */

    BIO_get_ssl(bio, & ssl);
    SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);

    /* Create and setup the connection */

    BIO_set_conn_hostname(bio, "www.verisign.com:https");

    if(BIO_do_connect(bio) <= 0)
    {
        fprintf(stderr, "Error attempting to connect\n");
        ERR_print_errors_fp(stderr);
        BIO_free_all(bio);
        SSL_CTX_free(ctx);
        return 0;
    }

    /* Check the certificate */

    if(SSL_get_verify_result(ssl) != X509_V_OK)
    {
        fprintf(stderr, "Certificate verification error: %i\n", SSL_get_verify_result(ssl));
        BIO_free_all(bio);
        SSL_CTX_free(ctx);
        return 0;
    }

    /* Send the request */

    BIO_write(bio, request, strlen(request));

    /* Read in the response */

    for(;;)
    {
        p = BIO_read(bio, r, 1023);
        if(p <= 0) break;
        r[p] = 0;
        printf("%s", r);
    }

    /* Close the connection and free the context */

    BIO_free_all(bio);
    SSL_CTX_free(ctx);
    return 0;
}

我正在 Ubuntu 上对 ARM 进行交叉编译（带有 CodeSourcery Lite 的 Eclipse）。

我最终做了类似以下的事情（伪代码）：

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

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.

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.
}

您也可以对 BIO_read() 使用相同的方法。

你可能会发现这个链接 useful.