Re: [PATCH v2 01/11] nl80211: also check for no preauth feature

On Sat, Apr 11, 2020 at 12:25:17PM +0200, Markus Theil wrote:
> Before Linux 5.7 all pre-auth frames are forwared over the nl80211 ctrl
> port, if it is registered. hostap and wpa_supplicant currently do not assume
> this behavior, as pre-auth frames should be handled as ordinary data frames
> in the kernel. Checking against the NL80211_EXT_FEATURE_CONTROL_PORT_NO_PREAUTH
> feature flag allows us to disable this behavior later on ctrl port registration.
> 
> No new capa->flags value is introduced, instead WPA_DRIVER_FLAGS_CONTROL_PORT is
> only set now, if this feature is present. Without this feature, only control
> port tx is possible without breaking pre-auth features.

Wouldn't this break the currently working EAPOL TX over control port
with older kernel versions?

> diff --git a/src/drivers/driver_nl80211_capa.c b/src/drivers/driver_nl80211_capa.c
> @@ -439,7 +439,9 @@ static void wiphy_info_ext_feature_flags(struct wiphy_info_data *info,
>  	if (ext_feature_isset(ext_features, len,
> -			      NL80211_EXT_FEATURE_CONTROL_PORT_OVER_NL80211))
> +			      NL80211_EXT_FEATURE_CONTROL_PORT_OVER_NL80211) &&
> +	    ext_feature_isset(ext_features, len,
> +			      NL80211_EXT_FEATURE_CONTROL_PORT_NO_PREAUTH))
>  		capa->flags |= WPA_DRIVER_FLAGS_CONTROL_PORT;

I was expecting the older capability
NL80211_EXT_FEATURE_CONTROL_PORT_OVER_NL80211 to enable TX-only and then
add RX on top of that if NL80211_EXT_FEATURE_CONTROL_PORT_NO_PREAUTH is
present. Is there a reason for not doing that? There have been two years
of kernel releases with NL80211_EXT_FEATURE_CONTROL_PORT_OVER_NL80211
while this new NL80211_EXT_FEATURE_CONTROL_PORT_NO_PREAUTH was added
just now, so it would seem that this patch would push out deployment of
this capability for couple of years..
 
-- 
Jouni Malinen                                            PGP id EFC895FA