Implementing a PPP/L2TP stack using Netgraph

[Rayene Ben Rayana]

Hi everybody, 
 
I'm trying to connect an IPv6 streaming client to an IPv6 server through a 
GPRS connection. 
 
The client protocol stack should be like this 
 
RTP / UDP / IPv6 / PPP(client) / L2TP / UDP / IPv4 / PPP (kernel) / 
Bluetooth  
 
For the moment, I've to implement this one to test. 
  
RTP / UDP / IPv6 / PPP(client) / L2TP / UDP / IPv4 / ethernet 
 
Ooof 
 
I've read some man pages and I think that the netgraph's graph should be 
like this. 
 
ng_socket  (/inet6/dgram/UDP) connected to   ng_ppp        (Inet) 
ng_ppp     (bypass)           connected to   PPP daemon    (???) 
ng_ppp     (link1)            connected to   ng_l2tp       (Session_0001) 
ng_l2tp    (ctrl)             connected to   ControlEntity (???) 
ng_l2tp    (lower)            connected to   UDP /IP       (but how) 
IP                            connected to   ng_ether      (Upper) 
 
Doesn't look to be good :( 
 
Please help me. I promise to write a tutorial for the newbies if this works.