[Click] Information sharing in Click

[Beyers Cronje]

Hi Adam,

The way I do it is via handler calls. So a downstream element will call an
upstream element's read/write handler. Alternatively you could use the
header space of a packet to include custom data per packet. Or you could
extend the packet annotations for your purposes.

Beyers

On 8/2/07, Adam M <click at irotas.net> wrote:
>
> Hi folks,
>
> Sorry for the barrage of questions, but I'm trying to field questions
> from colleagues/managers around here that I don't know the answer to.
> There is concern about the ability for Elements to share information
> with each other outside of the standard push/pull processing. Perhaps
> it's more clear if I give an example.
>
> In our case, we're considering using Click for simulating a wireless
> network. In our simulation, we deal with things like radio transmission
> radius, contention of the physical medium, signal quality, etc.
>
> When packets first arrive in the simulation, we'd like to have them
> analyzed and some results of that analysis stored somewhere. This
> analyzer would likely be an Element, and could either be a pass-through
> or we could hook it up using Tee.
>
> Now, the issue is that the results of this early analysis are needed by
> numerous downstream Elements. For example, some distant downstream
> Element might need to know what our estimate is for signal quality
> between two nodes. What I don't understand is how an Element can serve
> as an information repository that other Elements can query and get a
> response. All of the Click examples I've seen are unidirectional, where
> Element A pushes to B, which pushes to C, etc.
>
> I suspect that all this is possible in Click, but at the moment I don't
> see how to do it. Could someone please explain?
>
> Thanks again,
> Adam
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