Blocking on a non-blocking socket?

[Wiebe Cazemier]

Hi Detlef,

----- Original Message -----
> From: "Detlef Vollmann" <dv at vollmann.ch>
> To: openssl-users at openssl.org
> Sent: Friday, 24 May, 2024 12:02:37
> Subject: Re: Blocking on a non-blocking socket?
> 
> That's correct, but if I understand Matt correctly, this isn't the case.
> The idea of SSL_MODE_AUTO_RETRY is that if there's data, but it isn't
> application data but some kind of handshake data, then SSL_read doesn't
> return (after handling the handshake data), but immediately retries.
> If this retry fails with EWOULDBLOCK (or actually BIO_read returns 0),
> then SSL_read returns with 0 and SSL_WANT_READ.

Wouldn't the option then have to be called 'read more than one record at a time'? To me, 'retry' is a bit of a misnomer in that description.

Tracing the code, the retry seems to be considered based on BIO_fd_non_fatal_error(), which looks at EWOULDBLOCK. See [1] and [2].

Wiebe


[1] https://github.com/openssl/openssl/blob/b9e084f139c53ce133e66aba2f523c680141c0e6/crypto/bio/bss_fd.c#L226
[2] https://github.com/openssl/openssl/blob/b9e084f139c53ce133e66aba2f523c680141c0e6/crypto/bio/bss_fd.c#L113