Which is the preferred relationship?

* N receive queues share one (TCP/UDP) port whence all TX queues send to
this port

or

* Each transmit queue chooses a TCP/UDP port where, on the RX side, each
receive queue listens on its own port for that queue.

I'm betting it's the second case. However, what also confuses me is that
RSS sits between TX and RX and chooses which RX queue a packet gets into.
It's not deterministically set at TX time. Therefore the recommended
approach appears to actually be:

* Each transmit queue chooses a TCP/UDP port by knowing ahead of time how
RSS will hash the packet for delivery to a certain RX queue.

Thanks