reaching the UDP payload

[Benjamin Gaidioz <bgaidioz@lhpca.univ-lyon1.fr>]

Hi all,

My machine A is sending packets to my machine B through a LinuxDS-Router
and I want to know how long packets wait in the router. 

Packets are UDP packets < 1KB.  I want the kernel (2.2.14) to store time
stamps in the UDP payload during the call to dev_queue_xmit (before
q->enqueue) and qdisc_restart (right after hard_start_xmit).

Problem:
I guess the UDP payload is somewhere in the skb->data, but where?  It does
not seem to be eight bytes after the address pointed by skb->h.uh (the UDP
header).

Thanks for your help.