[openssl-dev] Adding async support

[Dmitry Belyavsky]

Dear  Matt,

On Thu, Oct 8, 2015 at 10:06 PM, Matt Caswell <matt at openssl.org> wrote:

>
>
> On 08/10/15 18:56, Dmitry Belyavsky wrote:
>
> >     The second problem is entirely engine dependant. It will be a
> different
> >     solution for different hardware. These patches do not provide a
> solution
> >     to that problem.
> >
> >
> > So I do not understand what you mean by "offload" :-(
> >
> > I understand that it's an engine-dependent, but I can't imagine a
> > corresponding pseudo code.
>
> Ok. So this is the pseudo code I posted before for how an engine might
> be implemented:
>
> static int myengine_aes128_cbc_cipher(EVP_CIPHER_CTX *ctx,
>     unsigned char *out, const unsigned char *in, size_t inl)
> {
>     int jobid;
>
>     jobid = offload_cipher_to_hardware(ctx, out, in , inl);
>
>     /*
>      * jobid holds a reference in the engine back to the work we just
>      * started
>      */
>
>     while(work_not_finished_yet(jobid)) {
>         /* Return control back to the calling application */
>         ASYNC_pause_job();
>     }
>
>     return get_results_from_hardware(jobid);
> }
>
>
> So lets imagine an engine that works via threads and how those pseudo
> code function call might be implemented. It could be something like this:
>
> void initialise_engine(void)
> {
>     start_thread(worker_main);
> }
>
> static int nextjobid = 0;
>
> struct work_st {
>     int jobid;
>     EVP_CIPHER_CTX *ctx;
>     unsigned char *out;
>     unsigned char *in;
>     size_t inl;
>     int ret;
> }
>
> int worker_main(void)
> {
>     struct work_st *work;
>
>     while(true) {
>         work = get_work_off_in_queue();
>         /* This is a long running operation */
>         work->ret = do_aes128_cbc_cipher(work->ctx, work->out, work->in,
> work->inl);
>         put_work_in_finished_set(work);
>     }
> }
>
> int offload_cipher_to_hardware(EVP_CIPHER_CTX *ctx, unsigned char *out,
> unsigned char *in, size_t inl) {
>     struct work_st *work;
>
>     work = malloc(sizeof *work);
>     work->ctx = ctx;
>     work->out = out;
>     work->in = in;
>     work->inl = inl;
>     work->jobid = nextjobid++;
>
>     add_work_to_in_queue(work);
>
>     return work->jobid;
> }
>
> int work_not_finished_yet(int jobid)
> {
>     return !is_work_in_finished_set(jobid);
> }
>
> int get_results_from_hardware(int jobid)
> {
>     struct work_st *work;
>
>     work = get_work_out_of_finished_set(jobid);
>
>     return work->ret;
> }
>
> In a hardware based engine everything in "worker_main" would be
> implemented in the hardware. So the hardware gets on with the long
> running crypto operation, whilst in the software control has returned
> back to the application.
>
> Does that make more sense?
>

Thank you! I finally got it.


-- 
SY, Dmitry Belyavsky
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