On 02/02/17(Thu) 22:14, Stefan Sperling wrote:
> I noticed that an 11a/b ath(4) card, which does not support 11g,
> includes 11g rates ("xrates") in association requests it sends on 2GHz:
>
> 20:55:03.490128 802.11 flags=0<>: association request, \
> caps=2041<ESS,SHORT_PREAMBLE,SHORT_SLOTTIME>, ssid (stsp.name), \
> rates 1M* 2M* 5M 6M 9M 11M 12M 18M, xrates 24M 36M 48M 54M, \
> rsn 0x0100000fac040100000fac040100000fac0200000000, \
> <radiotap v0, 1Mbit/s, chan 5, 11g, sig -26dBm, noise -89dBm>
>
> This is wrong. On 2GHz this client should only advertise 11b rates,
> i.e. rates up to and including 11M.
>
> This happens because invalid rates are not discarded from ni->ni_rates
> early enough. By default this rateset includes the 11a rates (which
> overlap with 11g ones). ieee80211_get_assoc_req() copies rateset
> information from ni->ni_rates and includes these bogus rates.
>
> To fix this, call ieee80211_fix_rate() after choosing an AP.
> The most important flag parameter here is DODEL which removes invalid rates.
> DODEL only takes effect if DOSORT and DONEGO are also set, so just pass
> all the flags.
>
> Now this client sends a proper 11b rateset in its assoc request:
>
> 21:49:36.934631 802.11 flags=0<>: association request, \
> caps=2041<ESS,SHORT_PREAMBLE,SHORT_SLOTTIME>, ssid (stsp.name), \
> rates 1M* 2M* 5M 11M, rsn 0x0100000fac040100000fac040100000fac0200000000, \
> <radiotap v0, 1Mbit/s, chan 5, 11g, sig -20dBm, noise -89dBm>
>
> Note that rates get fixed up again after association is confirmed,
> via ieee80211_recv_assoc_resp() -> ieee80211_setup_rates().
> Which is why 11b clients were already working fine in spite of sending
> a bogus rateset in the association request.
Does that mean this second correction is now unnecessary?
ok mpi@
> Index: ieee80211_node.c
> ===================================================================
> RCS file: /cvs/src/sys/net80211/ieee80211_node.c,v
> retrieving revision 1.113
> diff -u -p -r1.113 ieee80211_node.c
> --- ieee80211_node.c 2 Feb 2017 16:47:53 -0000 1.113
> +++ ieee80211_node.c 2 Feb 2017 20:50:36 -0000
> @@ -676,6 +676,12 @@ ieee80211_end_scan(struct ifnet *ifp)
>
> ic->ic_curmode = ieee80211_chan2mode(ic, ni->ni_chan);
>
> + /* Make sure we send valid rates in an association request. */
> + if (ic->ic_opmode == IEEE80211_M_STA)
> + ieee80211_fix_rate(ic, ni,
> + IEEE80211_F_DOSORT | IEEE80211_F_DOFRATE |
> + IEEE80211_F_DONEGO | IEEE80211_F_DODEL);
> +
> if (ic->ic_flags & IEEE80211_F_RSNON)
> ieee80211_choose_rsnparams(ic);
> else if (ic->ic_flags & IEEE80211_F_WEPON)
>
