Roaming between 2 APs with WDS

[Dan Williams]

On Wed, 2014-10-08 at 12:35 +0200, V?ctor Andr?s Andr?s wrote:
> Hello. I'm trying to get wifi roaming in a linux embedded device. The 
> network has been build with 2 Ubiquiti AP, with the same ssid and 
> connected with wds to each other.
> Actually, the kernel is 3.11 version. The wireless is Marvell sd8787 
> with the mwifiex driver. Wpa-supplicant / wpa-cli version: 2.2 and iw 
> tool version: 3.15.
> 
> I can connect to the wireless network, but not always connect to nearest 
> AP. And if go to the other AP, the device never try to connect to this 
> AP. It continues connected to the first AP. I think it isn't scanning 
> the differrents situation.

First, roaming works better with "bgscan" options enabled.  This option
tells the supplicant to periodically scan looking for a better AP.  If
scans don't happen (either through "bgscan" or manually via the control
interface) the supplicant will stick with the current AP until the
connection is broken.  The only way the supplicant knows which AP is
better is if a scan has taken place and it knows the RSSI of each AP.

Second, it looks like the driver is broken for signal strength
reporting.  -100dBm signal level is quite awful, and the fact that it
shows *all* APs at that level is pretty much a smoking gun.  This is the
reason the supplicant won't switch APs even if you do trigger a manual
scan, because no AP really has a better signal level than the current
one.

(one other slight possibility: your antenna isn't connected very well,
or isn't connected at all, and you're close to the APs...)

Dan

> If I scan the networks manually with wpa_cli, I get the same signal 
> level for all the networks, -101 ??
> 
> #wpa_cli scan
> #wpa_cli  scan_result
> Selected interface 'mlan0'
> bssid / frequency / signal level / flags / ssid
> 68:72:51:04:f8:06       2412    -101    [ESS]   WIRELESS_A
> f8:8e:85:85:a3:05       2412    -101    [WPA-PSK-CCMP][ESS]     **
> e4:c1:46:b4:bb:a8       2462    -101    [WPA-PSK-CCMP][ESS]     **
> 00:1f:c6:18:da:56       2452    -101    [WPA-PSK-TKIP][ESS]     **
> 30:46:9a:7c:7a:82       2412    -101    [WPA2-PSK-CCMP][ESS]    **
> 00:8e:f2:da:45:35       2462    -101 
> [WPA-PSK-CCMP+TKIP][WPA2-PSK-CCMP+TKIP][ESS]    **
> d4:ca:6d:95:1f:d3       2432    -101    [WPA2-EAP-CCMP][ESS]
> c0:4a:00:79:fc:7a       2462    -101 
> [WPA-PSK-CCMP+TKIP][WPA2-PSK-CCMP+TKIP][ESS]    **
> 00:50:7f:38:79:cd       2437    -101    [WEP][ESS]      **
> 00:1b:11:18:24:2b       2437    -101    [WEP][ESS]      *
> 00:26:5a:6e:15:75       2447    -100    [ESS]   **
> d6:ca:6d:88:4d:e2       2422    -101    [ESS]   **
> 06:02:a4:3d:86:9d       2462    -101    [IBSS]  **
> 68:72:51:04:f8:16       2412    -101    [ESS]   WIRELESS_A
> d6:ca:6d:95:1f:d3       2432    -101    [ESS]   **
> d6:ca:6d:88:4e:a2       2437    -101    [ESS]   **
> 02:0c:42:1a:72:e5       2452    -101    [ESS]   **
> 
> 
> Regards!
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