FreeLists / openbeosnetteam / [openbeosnetteam] Re: Talking between modules [Was: Change of heart...]

["David Reid" <dreid@xxxxxxxxxxxx>]

> >Hmm, you could do it that way.  How about a simple system where by each
> >module simply adds itself to a list of protocols it can speak, and what =
> the
> >function call is? They all take the same parameters, so it's not a biggi=
> e.
>
> But you have to have a rule somewhere in order to know what protocol you =
> have
> just decapsulated so you know what module you want to talk to.
> So in that case, either the rules would be something separate (e.g. some =
> kind
> of recognition library), or it would be in the lower layer.
> In that case, if you want to add IPv6 for example, you have to update the=
>
> ethernet layer or the recognition library  (with the new rule) *and* add =
> an
> IPv6 module. While if you have a GimmeYourRule function you can call, you=
>  can
> only add an IPv6 module and you don't have to update the ethernet module.=

Well, for instance in ethernet packets you look at the type field and decide
where to send it. I mean there's no reason not to preload the ethernet
module with every type of protocol to look for.  If the net server hasn't
got a suitable module it just silently discards the packet, or sends a
suitable response.

> As for taking the same parameters, well I am all for this whatever scheme=
>  we
> choose. In my previous example we can have HereIsYourData (datastruct &) =
> with
> datastruct holding the guessed protocol identifier, the data itself, and
> whatever useful information we may want.
> We can then either directly call the concerned module or have a generic
> net_input function read the guessed protocol identifier and call the modu=
> le.

Calling direct would be quicker but assumes a degree of knowledge of it's
surrounding that it probablt won't/can't have.  I mean an ethernet module
shouldn't really need to know anything beyond, it's from xx:xx:xx:xx:xx:xx
and was sent to me (or a broad/multi-cast) and it's of type XXXX. That's all
it needs to do it's job.

>
> That's only ideas but they are quite important so please let's debate the=
>  hell
> out of it :o)

OK.

david