how to check buffer status of a node in a routing protocol

I want to check a buffer status of a node in wireless mesh routing
protocol, where a node periodically checks the occupancy of its
link-layer buffer. The status is determined based on the ratio
between the the number of packets currently buffered to the buffer
size. I am new in NS2 so could anyone suggest me how it will implement
in code,as I am thinking inside routingqueue.cc (rqueue.cc) we have
to add some code.
Plz help me.
Thanks in advance.[/b]