Andrea Arcangeli wrote: 

All I care about is to assign a mempool ID to the skb (ID 
being unique identifier for the tcp connection I don't care 
how the implementation is). 

It makes sense to provide an API for the NIC driver to allocate skb from the
*right* mempool. This way if I have plenty of hw rings and/or can allow
myself a luxury to associate 1-to-1 connection and ring, there's a nice and
clean memory management model. Even NICs that have only few rings could use
this - for critical (e.g., storage) connections. 

Alex