On Wed, 14 Apr 1999, Andrew Cooke wrote:
>
> Hi,
>
> The problem I am seeing does not resolve itself on subsequent calls to SSL_read -
> if it fails to return -1 once, then repeated calls also return 0. In other words,
> on most occassions when the socket closes it returns -1 immediately, but sometimes
> it repeatedly returns 0.
Your presumtion (b) below is wrong. Unless you have requested
otherwise SSL_read/SSL_write is blocking.
And... After a normal socket close (no errors) from the other side
SSL_read *should* continue to return 0 (unless YOU close the
socket after the first 0 return). This is 100% analogues
with UN*X read behaviour.
And by the way it behaves the same way if you are using select and
non-blocking sockets. select will mark the socket as readable and
a read will return 0 if the other side has closed the socket.
So the correct way to handle the returnvalue from SSL_read should
be:
retval = SSL_read();
if(retval == 0)
otherSideClosedConnection();
else(if retval == -1)
errorOccuredDuringRead();
else
processReadData();
>
> If anyone could explain how to persuade SSL to do blocking reads that would give
> me a work-round.
>
> You mention using select - I have *not* been calling select. I presumed that:
>
> (a) Because of blocks/internal buffering select would be unreliable (there may be
> no decrypted data even if some encrypted data are available - if less than a block
> is present, for example).
>
> (b) SSL_read (and BIO in general) is non-blocking and self-contained.
>
> Should I be using select anyway?
>
> Cheers,
> Andrew
>
> Bodo Moeller wrote:
>
> > > What can be regarded as odd is that SSL_read() can return 0 even if it
> > > hasn't reached EOF.
> >
> > This can happen only under strange circumstances, I think.
> > Namely, ssl2_read will return 0 if it has read an empty data block.
> > Probably it should really return -1 and have things arranged so that
> > SSL_get_error tells the application to select() on readability;
> > or it should directly start the next read(), which will possibly
> > block.
>
>
>
>
>
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