I was looking at the code and they map the datagram directly to user
space and has a skb ring size of 2 frames. data cannot be available for
a re-write until it is acked by the interrupt completion of the ethernet
device.
You need to query the skb-users counter and check when it is
decremented
I don't specifically know about user-space, but Jun Yuan wrote a patch
for me, adding a function called `ecrt_domain_received` that tells you
whether the domain has been received or not (in kernel-space).
I have tested this function with domains spanning into multiple packets and
calling it while
