Довел до конца lapbether

./x25server 44
X25: socket created
X25: get socket option qbit = 0
X25: set socket facility OK
X25: socket bind to 44
X25: start listen ...
X25: socket listening
X25: socket accept from 33
X25: from client: Hello server !!! (17)
X25: to client: Hi client !!! (14)
X25: client closed
X25: socket closed

./x25client 33 44
X25: socket created
X25: get socket option qbit = 0
X25: set socket facility OK
X25: socket bind to 33
X25: socket connecting to 44 ...
X25: socket connect to 44
X25: to server: 'Hello server !!!' (17)
X25: from server: Hi client !!! (14)
X25: socket closed

http://files.rsdn.org/45405/x25client.c
http://files.rsdn.org/45405/x25server.c

теперь бы ethertap для ядра 3.10 найти :)

С уважением,  Павел