Proxying PPP from ATM to Ethernet and vice versa

Hi!

I'm currently developing at some SoHo Router which should be able to
speak
both PPPoE and PPPoA. In fact, the modem is a separate machine (TI SoC
with
ADSL logic onboard), accessible via a dedicated Ethernet NIC.

For PPPoE the modem simply bridges external and internal Ethernet
interfaces,
so the complete PPP dial-in (including authentication) can be done on
the
router itself.

The situation is more tricky with PPPoA. While searching for the most
convenient solution, I got the idea of writing a proxy daemon, doing
nothing
more than forwarding the PPP packets between the two underlying
protocols
(AAL5 and Ethernet). But it's not quite as easy as that. After all
I've been
reading, it looks like at least PPPoE is not just Ethernet frames with
PPP as
payload, but a protocol on it's own. Since my ATM knowledge is more or
less
equal to zero, I have no idea as to how much this applies to PPPoA,
too.

So my proxy would have to initiate PPPoA/PPPoE sessions in both
directions
before it can start with dumb packet forwarding. In order to do so, I
am
searching for some implementations (nobody want's to reinvent the
wheel), but
didn't find much (mostly it's packed with the actual PPP
functionality, as in
the samba.org PPP daemon).

Maybe someone in this group is willing/able to give me some criticism/
advice
about the above thoughts. In general, every feedback is highly
appreciated.


Following some picture (for you to better understand what I was trying
to form
into english sentences, as well as for me to add some 1337 to this
posting :).

,-------------, ,----------,
: ... : .......................... : ... |
|-------------| |----------|
| IP |----------------------------| IP |
|-------------| |----------|
| PPP |----------------------------| PPP |
|-------------| ,----------------, |----------|
| Ethernet |-----| Ethernet | ATM |-----| ATM |
'-------------' '----------------' '----------'

^^^^^^^^^^^ ^^^^^^^^^ ^^^^^^^^
SoHo Router DSL Modem DSL Peer


Greetings, Phil
.

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