Re: [RFC 6/6] wifi: mac80211: check vif radio_mask for monitor mode rx

[Felix Fietkau <nbd@nbd.name>]

On 23.08.24 12:23, Johannes Berg wrote:
> On Mon, 2024-08-05 at 21:23 +0200, Felix Fietkau wrote:
>> When restricting a monitor vif to only operate on a specific set of radios,
>> filter out rx packets belonging to other radios. This only works if drivers
>> fill in radio_valid and radio_idx in the rx status.
> 
> Why does the driver need to provide the radio, it already provides the
> frequency?
> 
> But then I wonder if this doesn't go a step too far? This is pretty much
> pretending that monitor only exists on a specific sub-radio, but ...
> what for? Even userspace could filter on the frequency.
> 
> I mean ... I get that you're trying to preserve a notion that you had
> that an interface exists on a given PHY and they're all separate, but
> they're not really separate any more, get used to it?

Well, there's a performance aspect as well. When only monitoring 
specific radios (while operating normally on others), relying on 
filtering in user space or even BPF comes at a cost, since mac80211 
still has to prepare radiotap headers and potentially clone data packets 
received on other radios.

- Felix