[Bug 196290] New: [net80211] [iwn] STA is in 11b mode, announces 11n HTINFO to AP, traffic fails

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=196290

            Bug ID: 196290
           Summary: [net80211] [iwn] STA is in 11b mode, announces 11n
                    HTINFO to AP, traffic fails
           Product: Base System
           Version: 11.0-CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: wireless
          Assignee: freebsd-wireless at FreeBSD.org
          Reporter: adrian at freebsd.org

Here's a fun one.

-HEAD as of december 23rd. NIC is iwn(4), Intel 5100.

The STA associates to an 11n AP (FreeBSD) fine, in 2GHz mode. Everything's
okay.

At some point it reassociates or something - i'm not yet sure. But it ends up
in 11b mode. I think this is one of those "VAP loses connection during an
active scan, so it gets stuck in the mode of the last active scan."

So it reassociates at 11b, to the same AP.

The AP sees this (typed in):

CAPS: EPS
FLAG: AQPHTRs
RATES<B2,B4,B11,B22>
RSN<stuff>
HTCAP<cap 0x2c param 0x1b mcasset[0-15] extcap 0x0 txbf 0x antenna 0x0>
WME<stuff>

Now, it's announcing 11b rates, no extended 11g rates, and MCS rates.

The iwn(4) NIC is in 11b mode, so it doesn't ever hear MCS rates. It fails to
ACK them. But the FreeBSD AP still sends them, as it thinks it's an MCS capable
device.

So - I think somewhere in net80211 in STA mode we're getting confused and
announcing 11n rates for a vap that's configured as 11b. iwn(4) configures the
hardware as non-11n and everything fails to work.

Restart wpa_supplicant won't work - the glue currently doesn't reset the media
back to auto, so it stays at 11b. I have to kill wpa_supplicant, do 'ifconfig
wlan0 media auto', then restart it.

I think the bugs here to fix are:

* the vap shouldn't stay as the last scan mode set it if the VAP goes down
during a scan - we should restore the original chanmode;
* wpa_supplicant should likely be explicitly setting the mode to be auto when
restarting its handshaking (unless configured to NOT be auto, then it should
explicitly set it to that);
* net80211 shouldn't be announcing MCS info sets if the vap is configured as
11b. That's plain stupid.

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