我的程序是基于OpenSSL(阻塞模式)开发的,我想将它重构为非阻塞模式 . 它在具有SSL对象的线程中调用SSL_read(),并在具有相同对象的另一个线程中调用SSL_write() .
我从书"Network Security with OpenSSL"学习了OpenSSL非阻塞模式,这个模式有一个例子(data_transfer) .
for (;;)
{
/* check the readability and writability */
check_availability(A, &can_read_A, &can_write_A, B, &can_read_B, &can_write_B);
/* write_waiton_read_A: SSL_write was blocked for SSL_ERROR_WANT_READ
* write_waiton_write_A: SSL_write was blocked for SSL_ERROR_WANT_WRITE
* read_waiton_write_A: SSL_read was blocked for SSL_ERROR_WANT_WRITE
* read_waiton_read_A: SSL_read was blocked for SSL_ERROR_WANT_READ
*/
/* not in the middle of a write on A */
if (!(write_waiton_read_A || write_waiton_write_A) &&
(A2B_len != BUF_SIZE) &&
/*
* a. A is readable.
* b. the read was blocked for "WANT_WRITE" and A
* is writable now.
*/
(can_read_A || (can_write_A && read_waiton_write_A)))
{
read_waiton_read_A = 0;
read_waiton_write_A = 0;
code = SSL_read(A, A2B + A2B_len, BUF_SIZE - A2B_len);
switch (SSL_get_error(A, code))
{
...
case SSL_ERROR_WANT_READ:
read_waiton_read_A = 1;
break;
case SSL_ERROR_WANT_WRITE:
read_waiton_write_A = 1;
break;
...
}
}
...
/* not in the middle of a read on A */
if (!(read_waiton_write_A || read_waiton_read_A) &&
have_data_B2A &&
/*
* a. A is writable.
* b. the write was blocked for "WANT_READ" and A
* is readable now.
*/
(can_write_A || (can_read_A && write_waiton_read_A)))
{
write_waiton_read_A = 0;
write_waiton_write_A = 0;
code = SSL_write(A, B2A, B2A_len);
switch (SSL_get_error(A, code))
{
...
case SSL_ERROR_WANT_READ:
write_waiton_read_A = 1;
break;
case SSL_ERROR_WANT_WRITE:
write_waiton_write_A = 1;
...
}
}
...
}
我从上面的代码中得出结论,如果SSL_REROR_WANT_READ被阻止,我必须等待SSL_read()完成,我不能调用SSL_write(),尽管在这种情况下A是可写的 .
这样对吗?我想我的程序可以同时读取和发送数据,如果SSL_read()被SSL_ERROR_WANT_READ阻止,我可以调用SSL_write()吗?
任何帮助是极大的赞赏 . 首先十分感谢 .
1 回答
你可以尝试,但你会得到的只是
SSL_WANT_READ
.很难理解为什么你甚至在考虑这个问题 .