[PATCH] nl80211: add extra-ies only if allowed by driver

[David Bauer]

Hi Johannes,

On 1/30/22 21:14, Johannes Berg wrote:
> On Sun, 2022-01-30 at 20:22 +0100, David Bauer wrote:
>>   
>> -	if (params->extra_ies) {
>> +	if (params->extra_ies && drv->capa.max_scan_ie_len >= params->extra_ies_len) {
>>   		wpa_hexdump(MSG_MSGDUMP, "nl80211: Scan extra IEs",
>>   			    params->extra_ies, params->extra_ies_len);
> 
> I guess that makes sense if capa.max_scan_ie_len is zero, but if not
> perhaps it'd be nice to be able to omit _some_ of the stuff?
> 
> Also, higher layers of the supplicant might expect their elements to be
> added, so I'm not sure what to make of this, that's a bit annoying.
> 
> Perhaps some configurations shouldn't be allowed if the
> capa.max_scan_ie_len is really small?

Good points. I'm not sure how we want this to be handled.

All extra-IEs are added in wpa_supplicant_extra_ies and ultimately
it is here where the resulting buffer size is determined.

We could prioritize there and add extra-IEs ordered until the buffer
is full. Tracing this down to hostapd initializing the interface however
is very complex, so not sure if this road is worth the effort.

That being said, we only touch the IEs present in probe requests, so
the impact on the resulting link should not be of an issue.

What would be your approach on that?

Best
David

> 
> johannes