[wpa_supplicant] Is there a way to limit peers (to about 12) for IBSS/adhoc?

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Hi Community,

There are similar variables in wpa_supplicant to limit peers or stations:
- max_peer_links for 802.11s mesh
- max_num_sta for AP mode (maybe P2P_GO? I do not know)

wpa_supplicant source code and data structures are daunting to me, although I worked on its source code for P2P about 1.5 years ago.

Can anyone point to me what functions I can change to add a variable (similar to max_peer_links or max_num_sta), with the purpose to limit the number of peers for IBSS/adhoc? Probably we do not need to start 4-way handshake once associated stations reach max_peers for IBSS?

Thanks a lot.

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



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