application to receive ethernet|IP|UDP a ethernet|ppp|IP|UDP packages over socket

Hello Everyone

I am working on a ADSL modem and have the following situation that I
would like to have some advice one.

My ADSL modem runs on Monta Vista Linux and comes in 2 models; Bridge
and a Router and my question concerns the Bridge.

To monitor the status of the ADSL modem we have an application(host
application) running on a PC/MAC that requests data of the modems
status from a control application that runs on the ADSL modem. When
the host application sends out a request it is in the form of a
broadcast using IP/UDP packet based upon a UDP socket setup. Now my
problem is when the ADSL modem is a bridge and host runs a PPPoE
client to encapsulate the data so that the ISP can receive it. When
having a setup like this a Windows machine sends out 2 packages when
the host application does a broadcast for status of the modem. One
packet is pure: ethernet|IP|UDP while the other one is
ethernet|ppp|IP|UDP and my application only picks up one packet which
is ethernet|IP|UDP and while the one containing ppp gets lost. Since
the 2 packages contains the same request for information its not such
a big deal under Windows. However when running this setup on a MAC
only 1 packet gets sent out from the host application:
ethernet|ppp|IP|UDP and this in NOT received by my control
application(its a UDP socket) and no data is sent back to the host
application.

After the "history" lesson I move onto my questions:
How do I setup a socket on the control application that can receive
both types of packages: ethernet|IP|UDP and a ethernet|ppp|IP|UDP

One option is to have a RAW Ethernet socket:
sock = socket(AF_INET,SOCK_RAW,htons(ETH_P_ALL));
This would collect ALL Ethernet frames and since this is a ADSL modem
there will be quite few of them. I would have to spend a lot of CPU
time looking for my control frames(they have a ID in the UDP data so
it can be done). I do not feel that this solution is the best but an
option that I am exploring.

I have also tried to set up a RAW IP/UDP socket:
sock = socket(AF_INET,SOCK_RAW,IPPROTO_UDP);
However this socket did only collect the IP/UDP and threw away the PPP
packages as it should do

So what I am looking for is like a middle way between RAW Ethernet and
RAW IP/UDP, I want my control application to receive 2 types of
packages: ethernet|IP|UDP and ethernet|ppp|IP|UDP.

Any advice or input would be greatly appreciated.

Regards
Andreas