I'm not sure I understood the comment about monitor interface correctly.
If the driver is configured in monitor mode (or whatever you would call
a mode where it receives all frames), I do expect to see ACK and RTS/CTS
frames in mac80211 (and in the monitor interface in user space for that
matter). I hope that this won't be changed.

We're talking about a virtual monitor interface that is in use while
we're also operating on another virtual interface.

It sounds perfectly reasonable to not indicate these control frame
subtypes when in normal (non-monitor) mode since they are most likely
processed in hardware/microcode/firmware. However, if they provide
additional information (say, signal strength), it could be useful to
send them to mac80211 anyway to provide more information for TX rate
control.

Again, we're only talking about frames we *sent*. There's a flag whether
to pass up control frames or not though which can be set in monitor
mode.

johannes