c - 非阻塞 BIO_do_connect 在没有互联网连接时阻塞

Question

我正在使用 Openssl-0.9.8x，如下所示:

bio = BIO_new_ssl_connect(ctx);
BIO_get_ssl(bio, & ssl);
SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
BIO_set_nbio(bio, 1);
in_addr_t serverIP =  inet_addr(HTTPS_SERVER_IP);
BIO_set_conn_ip(bio, &serverIP );
BIO_set_conn_port(bio, HTTPS_SERVER_PORT_STR);
while(1) {
    printf("BIO_do_connect start>>>>\n");
    if(BIO_do_connect(bio) <= 0 && BIO_should_retry(bio)) {
        sleep(1);
        printf("BIO_do_connect retry>>>>\n");
    }
    else {
        printf("Connect success.\n");
    }
}

当互联网连接正常时(即它可以连接到服务器)，它工作正常。但是，当 Internet 连接受限时(即无法连接到服务器)，BIO_do_connect() 在重试一次或多次后被阻止。输出如下:

BIO_do_connect start>>>>
BIO_do_connect retry>>>>
BIO_do_connect start>>>>
BIO_do_connect retry>>>>
BIO_do_connect start>>>>

最后在BIO_do_connect(...)中被阻塞了？为什么会这样？

Answer 1

这可能是您使用了SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY)。

来自 0.9.8 手册页:

SSL_MODE_AUTO_RETRY

Never bother the application with retries if the transport is blocking. If a renegotiation take place during normal operation, a SSL_read() or SSL_write() would return with -1 and indicate the need to retry with SSL_ERROR_WANT_READ. In a non-blocking environment applications must be prepared to handle incomplete read/write operations. In a blocking environment, applications are not always prepared to deal with read/write operations returning without success report. The flag SSL_MODE_AUTO_RETRY will cause read/write operations to only return after the handshake and successful completion.

SSL_MODE_AUTO_RETRY 的作用是自动重试否则会返回到应用程序代码的操作(即使在使用阻塞连接时)。当您想要非阻塞操作时使用它没有任何意义。

尝试完全删除该行。

顺便说一句，0.9.8 已不再受支持，不再接收安全更新。您真的应该升级到更新的版本。