[B.A.T.M.A.N.] [wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

[B.A.T.M.A.N.] [wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

[Xuebing Wang]

Hi community,

This email is mainly addressed to hostap/wpa_supplicant mailing list.

Descriptions of my issue:
- I am establishing IBSS/adhoc network using OpenWRT 15.05 + ath9k (AR9331).
- When nodes are relatively closely placed, the peers (the term is 
'neighbors' in batman-adv mesh) reach 40, ath9k driver detects "tx hung, 
resetting the chip" (for RESET_TYPE_TX_HANG).
- This ath9k "tx hung" randomly happens among the 40 nodes (in adhoc 
network), and it happens relatively often (seemingly randomly for 
nodes), and randomly makes some nodes un-usable.
- This appears to be an issue with ath9k kernel driver or ath9k hardware 
that it can not handle ~40 peers.
- IBSS/adhoc with 20 peers work well.

Is there a config in wpa_supplicant that we can limit the number of peers?

In the other words, once the number of peers ('iw wlan0 station dump') 
reaches a pre-configured number (e.g. 12 or 16), wpa_supplicant does not 
authenticate any more, for IBSS/adhoc only?
- A subtle detail: once a new beacon with higher RSSI is detected, the 
current connection with lowest RSSI will be de-authenticated, and to 
authenticate this new peer (with higher RSSI in beacon).

Is this "limiting number of peers for IBSS/adhoc" a good work-around for 
40+ peers adhoc network, although the ultimate root cause seemingly is 
with ath9k kernel driver or ath9k hardware?

Also, if there are many (like 40+) peers in IBSS/adhoc network, I am not 
sure how medium access contention and collisions factor in, for 
management frames?

Here is my wpa_supplicant conf file:
------
ctrl_interface=/var/run/wpa_supplicant

# use 'ap_scan=2' on all devices connected to the network
# this is unnecessary if you only want the network to be created when no 
other networks are available
ap_scan=2

network={
     ssid="Net-xxxxxxxx"
     mode=1
     frequency=2462
     proto=WPA2
     key_mgmt=WPA-PSK
     pairwise=CCMP
     group=CCMP
     psk="xxxxxxxx"
}
------

Another approach could be to use user-space shell script to "iw <dev> 
ibss leave" for the lower RSSI stations?
- As I am using batman-adv to build mesh network on the top of 
IBSS/adhoc, a similar approach can be done at batman-adv level.

Suggestions?

Thanks.
Xuebing Wang

Re: [B.A.T.M.A.N.] [wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

[Adrian Chadd]

Hi!

Does it happen if you run 40 IBSS nodes without encryption?

(I wonder if it's a MAC or PHY bug..)


-adrian

Re: [B.A.T.M.A.N.] [wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

[Xuebing Wang]

Thanks.

I did not try 40 IBSS nodes without encryption. I am using software 
encryption for ath9k because of key caching issues discussed in below 
threads:
https://patchwork.kernel.org/patch/9381651/
https://github.com/cozybit/authsae/issues/42

This is a customer site in the field, our temporary work-around is to 
create 2 networks (each is with 20 nodes) by using different SSID.

Because this is customer site in the field, it is not convenient to 
change and test. Does it make sense to test without encryption, 
encryption is a MUST?

Xuebing Wang

On 2017年06月03日 13:18, Adrian Chadd wrote:
> Hi!
>
> Does it happen if you run 40 IBSS nodes without encryption?
>
> (I wonder if it's a MAC or PHY bug..)
>
>
> -adrian
>

Re: [B.A.T.M.A.N.] [wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

[Adrian Chadd]

Hi,

Well, it sounds like something you need a 40 node test network for :)

I was wondering whether it was some kind of MAC bug that was being
triggered because of so many units say, overflowing the keycache or
something. But if it's software encryption then maybe not. I wish I
could help more, but setting up a 40 node network to test is a big
challenge. :)

Is it a gradual thing?  Ie, do you know when it starts to hang? Does
it hang at 40? or gradually as you approach 40?

As for association limits - I thought there was a maximum station
parameter somewhere...


-adrian

Re: [B.A.T.M.A.N.] [wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

[Xuebing Wang]

Hi Adrian,

=> Is it a gradual thing?  Ie, do you know when it starts to hang? Does
it hang at 40? or gradually as you approach 40?

We do not know. What we do know is, 20 peers / neighbors work well.

Jason Toschlog in CC said that he observed similar issues with brcmfmac 
when peers reach 32 (16 peers work for him).

I guess I will setup 32 or 40 nodes here and try limit the max number of 
peers (at wpa_supplicant) for IBSS/adhoc.

Thanks again.

Xuebing Wang

On 2017年06月03日 14:16, Adrian Chadd wrote:
> Hi,
>
> Well, it sounds like something you need a 40 node test network for :)
>
> I was wondering whether it was some kind of MAC bug that was being
> triggered because of so many units say, overflowing the keycache or
> something. But if it's software encryption then maybe not. I wish I
> could help more, but setting up a 40 node network to test is a big
> challenge. :)
>
> Is it a gradual thing?  Ie, do you know when it starts to hang? Does
> it hang at 40? or gradually as you approach 40?
>
> As for association limits - I thought there was a maximum station
> parameter somewhere...
>
>
> -adrian
>

Re: [B.A.T.M.A.N.] [wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

[Xuebing Wang]

Hi Honma-san,

Does max_peer_links apply to IBSS/adhoc (in addition to 802.11s mesh)? 
Thanks.

Xuebing Wang


On 2017年06月03日 12:09, Xuebing Wang wrote:
> Hi community,
>
> This email is mainly addressed to hostap/wpa_supplicant mailing list.
>
> Descriptions of my issue:
> - I am establishing IBSS/adhoc network using OpenWRT 15.05 + ath9k 
> (AR9331).
> - When nodes are relatively closely placed, the peers (the term is 
> 'neighbors' in batman-adv mesh) reach 40, ath9k driver detects "tx 
> hung, resetting the chip" (for RESET_TYPE_TX_HANG).
> - This ath9k "tx hung" randomly happens among the 40 nodes (in adhoc 
> network), and it happens relatively often (seemingly randomly for 
> nodes), and randomly makes some nodes un-usable.
> - This appears to be an issue with ath9k kernel driver or ath9k 
> hardware that it can not handle ~40 peers.
> - IBSS/adhoc with 20 peers work well.
>
> Is there a config in wpa_supplicant that we can limit the number of 
> peers?
>
> In the other words, once the number of peers ('iw wlan0 station dump') 
> reaches a pre-configured number (e.g. 12 or 16), wpa_supplicant does 
> not authenticate any more, for IBSS/adhoc only?
> - A subtle detail: once a new beacon with higher RSSI is detected, the 
> current connection with lowest RSSI will be de-authenticated, and to 
> authenticate this new peer (with higher RSSI in beacon).
>
> Is this "limiting number of peers for IBSS/adhoc" a good work-around 
> for 40+ peers adhoc network, although the ultimate root cause 
> seemingly is with ath9k kernel driver or ath9k hardware?
>
> Also, if there are many (like 40+) peers in IBSS/adhoc network, I am 
> not sure how medium access contention and collisions factor in, for 
> management frames?
>
> Here is my wpa_supplicant conf file:
> ------
> ctrl_interface=/var/run/wpa_supplicant
>
> # use 'ap_scan=2' on all devices connected to the network
> # this is unnecessary if you only want the network to be created when 
> no other networks are available
> ap_scan=2
>
> network={
>     ssid="Net-xxxxxxxx"
>     mode=1
>     frequency=2462
>     proto=WPA2
>     key_mgmt=WPA-PSK
>     pairwise=CCMP
>     group=CCMP
>     psk="xxxxxxxx"
> }
> ------
>
> Another approach could be to use user-space shell script to "iw <dev> 
> ibss leave" for the lower RSSI stations?
> - As I am using batman-adv to build mesh network on the top of 
> IBSS/adhoc, a similar approach can be done at batman-adv level.
>
> Suggestions?
>
> Thanks.
> Xuebing Wang
>

Re: [B.A.T.M.A.N.] [wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

[Simon Wunderlich]

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Hi Xuebing,

are your devices all configured with on AP and one IBSS interface? Or even more 
AP interfaces? What is the multicast rate you used?

One thing you need to consider is that in ath9k if you run AP and IBSS at the 
same time (at least with OpenWRT), the distributed IBSS beaconing is disabled 
and each node will beacon the "normal" ~10 times per second. That means with 
AP and IBSS and 40 nodes, you end up with ~800 beacons per second. That might 
be a problem (especially if all nodes are in the same spot).

To change this, you can try:

 * increase the multicast rate to e.g. 18 mbit/s (note, this may also change 
the batman-adv neighbor range) and verify that the beacons are sent on higher 
rates
 * disable some APs - you don't need so many anyway if they are all on the 
same spot
 * increase the beacon interval on the APs- although some clients may not like 
that.

.. anyway, that is all stuff you can try if you have the feeling the airtime 
is "polluted", so I would suggest to verify if this is the cause first before 
taking counter measures.

Cheers,
     Simon
On Saturday, June 3, 2017 2:30:27 PM CEST Xuebing Wang wrote:
> Hi Adrian,
> 
> => Is it a gradual thing?  Ie, do you know when it starts to hang? Does
> it hang at 40? or gradually as you approach 40?
> 
> We do not know. What we do know is, 20 peers / neighbors work well.
> 
> Jason Toschlog in CC said that he observed similar issues with brcmfmac
> when peers reach 32 (16 peers work for him).
> 
> I guess I will setup 32 or 40 nodes here and try limit the max number of
> peers (at wpa_supplicant) for IBSS/adhoc.
> 
> Thanks again.
> 
> Xuebing Wang
> 
> On 2017年06月03日 14:16, Adrian Chadd wrote:
> > Hi,
> > 
> > Well, it sounds like something you need a 40 node test network for :)
> > 
> > I was wondering whether it was some kind of MAC bug that was being
> > triggered because of so many units say, overflowing the keycache or
> > something. But if it's software encryption then maybe not. I wish I
> > could help more, but setting up a 40 node network to test is a big
> > challenge. :)
> > 
> > Is it a gradual thing?  Ie, do you know when it starts to hang? Does
> > it hang at 40? or gradually as you approach 40?
> > 
> > As for association limits - I thought there was a maximum station
> > parameter somewhere...
> > 
> > 
> > -adrian


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