Re: [PATCH 2/2] HE: propagate BSS color settings to nl80211

On Tue, Feb 04, 2020 at 09:04:55AM +0100, John Crispin wrote:
> This patch adds the code required to send the BSS color settings to the kernel.
> 
> It depends on the latest nl80211.h from the linux-wireless tree.

And on a new libnl version as well which is problematic..

> diff --git a/src/drivers/driver_nl80211.c b/src/drivers/driver_nl80211.c
> @@ -4108,6 +4108,9 @@ static int wpa_driver_nl80211_set_ap(void *priv,
> +	bss_color = nla_nest_start(msg, NL80211_ATTR_HE_BSS_COLOR);

This breaks all AP functionality with commonly used libnl versions if
the kernel includes a check for NLA_F_NESTED. And this happens even if
no IEEE 802.11ax is used.

nl80211: kernel reports: NLA_F_NESTED is missing
nl80211: Beacon set failed: -22 (Invalid argument)

This would need the following libnl commit:
https://github.com/thom311/libnl/commit/7de65a051fb37ece16f896a7385073274b77a133

But that is not included in commonly used libnl releases (it was added
in 3.5.0)..

At minimum, this addition of NL80211_ATTR_HE_BSS_COLOR would need to
depend on HE being enabled in the configuration, but even that does not
sound nice. Maybe doing an ugly hack like this would be justifiable
here:

bss_color = nla_nest_start(msg, NL80211_ATTR_HE_BSS_COLOR | NLA_F_NESTED);

This could be conditional based on the used libnl version. Maybe
something with NL_CAPABILITY_VERSION_3_5_0 (which is defined in
netlink/utils.h) or nl_has_capability() at runtime.
 
-- 
Jouni Malinen                                            PGP id EFC895FA