Re: mac80211: holding sta_info for non associated stations

[Johannes Berg <johannes@sipsolutions.net>]

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> >  > If i associate to a random AP "x" (what happened automatically as i
> >  > was configured by ifup scripts to do that), and then scan and
> >  > associate to my desired AP "y", i notice that AP "x" was not removed
> >  > from the mac80211 station table. Then, what happened was that during
> >  > ieee80211_stop, when we reach
> >  >
> >  > list_for_each_entry_rcu(sta, &local->sta_list, list) {
> >  >     if (sta->sdata == sdata)
> >  >     ieee80211_sta_tear_down_BA_sessions(dev, sta->addr);
> >  > }
> >  >
> >  > we try to tear down sessions to irrelevant stations (AP "x" in my
> >  > example), which leads to bugs.
> >
> >  Why would that lead to bugs? That station was known, and there are no
> >  sessions for that AP.
> 
> It's like freeing twice the same a pointer. On what level will you
> check that there are no BA session with this ghost  AP?

I don't see the problem. BA sessions are per-STA-info, so what's the
problem with having a STA-info linger around a bit longer maybe?

> >  There might be a problem in that we forget to remove that AP under some
> >  circumstances but it shouldn't matter, we always can have multiple
> >  stations in our table.
> 
> Not in STA mode, should be associated only to one AP at a time. (Hope
> this also cover roaming).

True, but BA sessions ought to also work in AP mode and I don't see
where the code differs.

Maybe I misunderstood the problem?

johannes

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