Uh... Dan, read() always returns 0 on EOF, so SSL_read() will always return
0 too (also setting SSL_ERROR_ZERO_RETURN). That's true for the first read
on EOF and all reads afterwards. Do you think that read() will return 0 if
it's not EOF? If read() would block, it returns -1 and sets errno=EAGAIN.
read()==0 alwats means EOF.
--Noel
----- Original Message -----
From: "Dan Kegel" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, October 26, 2002 1:13 PM
Subject: SSL_set_fd() harmful when using nonblocking sockets?
> With Unix nonblocking sockets, the only way to detect that the
> connection has shut down is to check for a zero return from read
> after poll or select says the socket is ready for reading.
> (Read will cheerfully return zero at any time if you call it
> again after a fully successful read(), so only the first read()
> after poll() should be checked. If you don't believe me, try it.)
>
> Given that, let's look at how OpenSSL detects EOF:
>
> int SSL_get_error(SSL *s,int i)
> {
> ...
> if (i == 0) {
> if (s->version == SSL2_VERSION) {
> /* assume it is the socket being closed */
> return(SSL_ERROR_ZERO_RETURN);
> } else {
> if ((s->shutdown & SSL_RECEIVED_SHUTDOWN) &&
> (s->s3->warn_alert == SSL_AD_CLOSE_NOTIFY))
> return(SSL_ERROR_ZERO_RETURN);
> }
> }
> return(SSL_ERROR_SYSCALL);
> }
>
> Hrmf. Looks like SSL_get_error will return SSL_ERROR_ZERO_RETURN
> or SSL_ERROR_SYSCALL on any zero read. When using SSLV3 or TLS,
> OpenSSL seems to have a case where it won't tell you about
> zero returns from read(), which is confusing.
> And since the user has no idea when OpenSSL is calling read(),
> and there's no way to tell OpenSSL what poll() said,
> *there is no way to properly detect EOF with nonblocking
> sockets in OpenSSL when using SSL_set_fd() / bss_sock.c *.
>
> I'm starting to think that you *must* do the read() yourself
> into a buffer, and use a memory BIO of some sort. Otherwise
> you have too little control over hard EOF detection.
>
> Somebody tell me how I'm wrong, please... I almost certainly haven't
> looked into this enough to know what I'm talking about.
>
> Thanks,
> Dan
> ______________________________________________________________________
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