[coyotos-dev] IPC Redesign
clandau at macslab.com
Tue May 22 15:24:07 EDT 2007
At 3:03 PM -0400 5/22/07, Jonathan S. Shapiro wrote:
>On Tue, 2007-05-22 at 11:22 -0700, Charles Landau wrote:
>> At 1:59 PM -0400 5/22/07, Jonathan S. Shapiro wrote:
> > >On Tue, 2007-05-22 at 10:30 -0700, Charles Landau wrote:
> > > > I'm approaching this issue from the standpoint of compatibility with
>> >> CapROS. It would be a pity if programs written for one system were
>> >> difficult to port to the other because they use features that are not
>> >> available on the other system.
>> >This is the job of CapIDL.
>> Can I use CapIDL to write a transparent forwarder/proxy that will
>> accept *any* message? How many data words does my proxy need to
>No. CapIDL *explicitly* does not expose low-level representation. That
>isn't its job. The entire point of CapIDL is to isolate the user from
>the low-level representation. The policy decision is that interfaces are
>defined by their IDL, not by their transport-level protocol.
>Setting that aside, fully transparent forwarding is not possible in
>principle, because you need to know what the call/response protocol is,
Excuse me, but didn't the long discussion on cap-talk about membranes
and such come to the opposite conclusion? And doesn't the Horton
protocol involve a transparent forwarder? The only thing you need to
know about the protocol is where the capabilities are.
>All that being said, my view is that the adoption of IDL strongly
>reduces the importance of this issue. Given an IDL specification, it is
>possible to automatically generate a forwarder for any given interface.
Yes, but for a *transparent* forwarder (assuming such a thing is
possible), I don't see how CapIDL can help. And that is a pity,
though perhaps not such a large one.
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