==================== Fix netdevim to correctly mark NAPI IDs
This series fixes netdevsim to correctly set the NAPI ID on the skb. This is helpful for writing tests around features that use SO_INCOMING_NAPI_ID.
In addition to the netdevsim fix in patch 1, patches 2 & 3 do some self test refactoring and add a test for NAPI IDs. The test itself (patch 3) introduces a C helper because apparently python doesn't have socket.SO_INCOMING_NAPI_ID.