Skb tracking event
#{tracking id} (skb {skb address})
The tracking id is a unique id generated by Retis' tracking logic. The socket
buffer address is also returned in the tracking events to help distinguish
between clones (as they share the same tracking id).
When a probe is used with the ftrace option and is hit from a call path where
no trackable object (e.g. struct sk_buff) was directly available at the probe
site, the skb address will be reported as 0. Note that post-processing
commands such as sort reconstruct the skb address from the tracking context,
so the displayed skb address may be non-zero even for such events.