Measuring Network Packet processing time

Hi all, I’m running xen 4.2 on Linux Kernel 3.7 and I’m trying to figure out the time taken(latency) by a network packet to reach it’s destination VM from the time it arrives at the NIC. What do you think is the best way to do it? I was thinking may be add rdtsc timestamp to the IP options header on arrival, and one more when it reaches to its desired VM and examine the two timestamps. I’ve not figured out a way to do this yet—but do you think this is a viable option or what other methods would you recommend? Thanks, Sunny