Re: [PATCH] brcmfmac: support AP isolation to restrict reachability between stations

On Sat, 2025-04-26 at 13:21 +0530, Gokul Sivakumar wrote:
> IMHO, In CFG80211, if we introduce a bitmap to track which BSS Parameter
> is changed by the userspace in the SET_BSS operation and then used this
> bitmap while handling the request, then the WLAN Driver would reject the
> operation with "EOPTNOTSUPP", instead of doing AP Isolation, because it
> does not support setting the other BSS params in the request.

Not necessarily?

> For Example, considering hostapd (iwd doesn't support SET BSS operation)
> if the user only enabled the config file param "ap_isolate", but didn't
> explicitly set "preamble", hostapd would implicitly set default value
> (0 - LONG_PREAMBLE) in the preamble param while sending the SET_BSS
> operation request to CFG80211.

But presumably that's still the default value in the driver too?

Hostapd could also be fixed too, to not change it if not requested.

> CFG80211 would then mark the bit corresponding to the SHORT_PREAMBLE BSS
> param as "changed" in the bitmap. WLAN Driver on receiving this SET_BSS
> request, would then have to reject the entire operation without enabling
> the user requested "ap_isolation" param, because of the preamble param
> that is not even explicitly requested by the user.

Or the driver can accept short-preamble setting, and reject it only if
it's set to short-preamble, rather than long-preamble.

> However, for other AP BSS Parammeters, we don't have the corresponding
> NL80211 feature flags.

Uh such a long time ago :) I don't remember why we had these. Given the
above do we need new ones? We can I guess, but I'm not sure it's needed
even if we change hostapd - if we do change it then it can just set only
the ones that were set in the config file?

johannes