[PATCH wireless] wifi: cfg80211: Fix "no buffer space available" error in nl80211_get_station() for MLO

[Johannes Berg]

On Fri, 2025-09-05 at 18:18 +0530, Nithyanantham Paramasivam wrote:
> Currently, nl80211_get_station() allocates a fixed buffer size using
> NLMSG_DEFAULT_SIZE. In multi-link scenarios - particularly when the
> number of links exceeds two - this buffer size is often insufficient
> to accommodate complete station statistics, resulting in "no buffer
> space available" errors.
> 
> To address this, modify nl80211_get_station() to return only
> accumulated station statistics and exclude per link stats.
> 
> Pass a new flag (link_stats) to nl80211_send_station() to control
> the inclusion of per link statistics. This allows retaining
> detailed output with per link data in dump commands, while
> excluding it from other commands where it is not needed.

I guess I'll apply the patch for now since it makes things _better_, but
I'm really not convinced that it's actually sufficient, and I'm very
tempted to throw in another patch to make it always false for 6.17.
Convince me not to? I'll reason below:

It seems to me that with many links, even for dump you could easily need
more space than the size available for a single dump message just like
with get, since there's no fundamental difference between the two. So it
seems to me that not only should it be opt-in from userspace to retrieve
the data during dump, but also there should be the ability to split the
dump not only on a per-STA basis but also per-link within the STA, which
requires some logic adjustments on both sides (hence the opt-in.)

Especially if we start seeing more links and/or more data for each link,
this will otherwise become an issue even in dumps.

johannes