Problem with hostap and cards in ad-hoc mode ...

[Daniel Prather]

I'm having the strangest and weirdest problem with a set of devices all
using hotap and in ad-hoc mode.  They've been fine for months, but
recently someone turned on an access point in the area that seems to
have attracted the attention of my ad-hoc cards.  I've completely run
out of ideas for things to do.  

Basically, I setup the cards with a command such as ...

iwconfig wlan0 mode ad-hoc channel 6 essid foo

wlan0     IEEE 802.11b  ESSID:"foo"
          Mode:Ad-Hoc  Frequency:2.437GHz  Cell: 00:0C:41:66:56:C2
          Bit Rate:11Mb/s   Tx-Power=24 dBm   Sensitivity=1/3
          Retry min limit:8   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality:66/92  Signal level:-53 dBm  Noise level:-98 dBm
          Rx invalid nwid:0  Rx invalid crypt:17903  Rx invalid frag:0
          Tx excessive retries:734  Invalid misc:2189197   Missed
beacon:0

The output of iwconfig wlan0 at this point should look something like
this.

So everything was good,right?  These systems have been up for months
with no problem.  So I check again a few days ago and I get this ...

wlan0     IEEE 802.11b  ESSID:"bar"
          Mode:Ad-Hoc  Frequency:2.422GHz  Cell: 00:0D:44:6A:5C:C8
          Bit Rate:11Mb/s   Tx-Power=24 dBm   Sensitivity=1/3
          Retry min limit:8   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality:66/92  Signal level:-53 dBm  Noise level:-98 dBm
          Rx invalid nwid:0  Rx invalid crypt:17903  Rx invalid frag:0
          Tx excessive retries:734  Invalid misc:2189197   Missed
beacon:0

Just as a note, the cell addresses are made up because I can't get the
accurate ones due to this problem.  But anyway, I notice that the essid
has changed, the channel has changed, the cell has changed, and I can no
longer talk to anything else on my ad-hoc network.

So I try the original iwconfig command again that I used to setup the
interface in the first place.  

iwconfig wlan0 mode ad-hoc channel 6 essid foo

What does it do?  Absolutely nothing.  At least, if it's changing
anything, it does it so fast that I can't see it.  It completely ignores
any new settings I pass to it and constantly associates with bar.  If I
turn on manual host_roaming with iwpriv, it'll disassociate with bar,
but I then can't connect to any of the other nodes I have out there (I
can still see them in iwlist wlan0 scan, but I can't talk to them).  

So, is there *anything* I can do?  Is there a way to force the cell
address of an ad-hoc network so that it only talks in one cell?  Or to
forbid it from connecting to a specific AP?  Or ... anything?  bar is
actually an access point too, not another ad-hoc network (at least as
far as iwlist wlan0 scan is concerned).  I just need it to only talk to
things on the same essid as the one I assign and nothing else.

Thanks very much for any help you can provide!

--
Daniel Prather
daniel at citynetwireless.net

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