Re: [exim] data-phase efficiency

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Autor: Chris Lightfoot
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A: exim-users
CC: Ian FREISLICH, Jeremy Harris
Assumpte: Re: [exim] data-phase efficiency
On Wed, May 25, 2005 at 09:43:00AM +0100, Philip Hazel wrote:
> On Wed, 25 May 2005, Ian FREISLICH wrote:
>
> >        If the underlying BIO is non-blocking, SSL_write() will also return,
> >        when the underlying BIO could not satisfy the needs of SSL_write() to
> >        continue the operation. In this case a call to SSL_get_error(3) with
> >        the return value of SSL_write() will yield SSL_ERROR_WANT_READ or
> >        SSL_ERROR_WANT_WRITE. As at any time a re-negotiation is possible, a
> >        call to SSL_write() can also cause read operations! The calling process
> >        then must repeat the call after taking appropriate action to satisfy
> >        the needs of SSL_write(). The action depends on the underlying BIO.
> >        When using a non-blocking socket, nothing is to be done, but select()
> >        can be used to check for the required condition. When using a buffering
> >        BIO, like a BIO pair, data must be written into or retrieved out of the
> >        BIO before being able to continue.

>
> Fascinating, but I'm afraid that's all completely over my head! I'm
> really not good at the SSL stuff, and remember, Exim supports GnuTLS as
> well as OpenSSL. What is currently there seems to work, and as I have
> far too much other stuff to do, my judgement at the moment is to leave
> well alone.


it's nasty, because it can make a select loop much more
tangled. One alternative would be to fork a process to
proxy between SSL and non-SSL connections, though this has
its own disadvantages.

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