On Fri, Apr 20, 2001 at 11:29:51AM -0400, Tom Biggs wrote:
> I'm implementing code to do OpenSSL handshake/read/write
> for some radically different hardware. These will completely
> replace the standard OpenSSL handshake state machine
> and most of the API functions at the SSL_METHOD level.
>
> I am used to I/O return codes where
> ( > 0 ) means success
> ( == 0 ) means I/O block but otherwise no problem
> ( < 0 ) means error
>
> So far, I've implemented all my routines to work that way.
Usually 0 means EOF. 'I/O block' is a return value of -1 with errno
set to EAGAIN or EWOULDBLOCK, these days (O_NONBLOCK semantics).
You'd see 0 in these situations only if you use O_NDELAY, but you
should not do this: The O_NDELAY semantics make it impossible to tell
the difference between EOF (connection closed) and a EWOULDBLOCK
situation (connection open, but no data available) for read requests.
(While often both O_NDELAY and O_NONBLOCK are available, luckily only
the latter is standardized.)
> According to the manpages for the ssl(3) API functions,
> OpenSSL works a bit differently
> ( > 0 ) means success
> ( == 0 ) means error
> ( < 0 ) means error
>
> In both cases the manpage advises calling SSL_get_error()
> to find the reason.
When SSL_read() etc. return 0 this means that EOF was encountered.
To find out if this is an error, you have to call SSL_get_error();
it might be a legitimate closure.
When SSL_read() etc. return -1, this is not necessarily an error;
it might be an EWOULDBLOCK situation. Again you'll have to
call SSL_get_error() to check.
You don't have to look at SSL_{connect,accept,read,peek,write} return
values in your program; just pass them over to SSL_get_error().
For positive return values, SSL_get_error() will always return
SSL_ERROR_NONE; but for 0 or -1, there's usually not much the
application can find out by itself.
--
Bodo Möller <[EMAIL PROTECTED]>
PGP http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller/0x36d2c658.html
* TU Darmstadt, Theoretische Informatik, Alexanderstr. 10, D-64283 Darmstadt
* Tel. +49-6151-16-6628, Fax +49-6151-16-6036
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