How do I configure wpa_supplicant to try all hidden SSIDs in quick succession?

warmana · 11-14-2006, 02:07 PM

I have wpa_supplicant working fine in a number of locations, each of which uses (amongst other things) hidden SSIDs.

When wpa_supplicant.conf has just the one network={..} definition for a location, or if that definition is the first one in the .conf file, then association and dhcp allocation works really well and quickly.

But if the wrong network definition is used (say, I forgot to change the .conf file when I moved to another location), the network connection will time out before wpa_supplicant has tried the correct definition.

I know each of the locations has good APs, as association is normally very quick.

I have to use ap_scan=2 to get wpa_supplicant to probe for the location AP. How do I get wpa_supplicant to just try for (say) less than 5 seconds, before trying the next network definition in wpa_supplicant.conf.

This is on Slackware 11.0, using a 2.6 kernel, and an IPW2200 wireless driver (all of which seem to work fine).

Thanks for any help.

marsm · 11-15-2006, 03:22 PM

Skimming through the manuals for wpa_supplicant, wpa_supplicant.conf and wpa_cli I don't immediately see a way of actually doing it 'within' wpa_supplicant. In this case I'd just write a script that generates the appropiate settings for the next network in wpa_supplicant.conf and restarts wpa_supplicant until it's connected.

Hangdog42 · 11-15-2006, 05:16 PM

Quote:

But if the wrong network definition is used (say, I forgot to change the .conf file when I moved to another location), the network connection will time out before wpa_supplicant has tried the correct definition.

Why would you have to change .conf files? You can list multiple networks in the same .conf file without a problem. You can also prioritize them a bit by using a priority line in each network section. Here is an example:

Code:

network={
ssid="HomeSSID"
key_mgmt=NONE
auth_alg=SHARED
group=WEP104
wep_key0=HexWEPKey
wep_tx_keyidx=0
priority=5
}
network={
ssid="AnotherSSID"
key_mgmt=NONE
auth_alg=SHARED
group=WEP40
wep_key0="WEPHexKEy"
wep_tx_keyidx=0
priority=4
}
network={
ssid="AThirdSSID"
key_mgmt=NONE
auth_alg=SHARED
group=WEP40
wep_key0=WEPHexKey
wep_tx_keyidx=0
priority=1
}
network={
ssid="WPA_NETOWRK_SSID"
scan_ssid=1
key_mgmt=WPA-PSK
pairwise=TKIP
group=TKIP
psk="WPA_Passphrase"
priority=1
}

The higher the integer on the priority line, the sooner wpa_supplicant will connect to it.

warmana · 11-17-2006, 01:51 AM

Hangdo42: <nods> Yes, I've tried using the "priority=.." setting. The problem is that because at least two of the networks use hidden SSIDs, I can't get the driver to scan for possible networks (using the ap_scan=0 global option). I have to use ap_scan=2. The sample configuration file has a comment which says:
"Please note that AP scanning with scan_ssid=1 and ap_scan=2 mode are not
using this priority to select the order for scanning. Instead, they try the
networks in the order that used in the configuration file."
And indeed, that is exactly what does happen.
So, if I'm working in the 'second' network location, wpa_supplicant tries the 'first' location first, but dhcp time-out occurs before wpa_supplicant tries the next ('second') location. That's why I was wondering if there is any way to get wpa_supplicant to move to the next network more quickly.

marsm: Yes, that's the same conclusion I reached for now. That, and perhaps see if I can find anything in the code itself.

Thanks for all your suggestions.

Hangdog42 · 11-17-2006, 07:14 AM

Quote:

So, if I'm working in the 'second' network location, wpa_supplicant tries the 'first' location first, but dhcp time-out occurs before wpa_supplicant tries the next ('second') location. That's why I was wondering if there is any way to get wpa_supplicant to move to the next network more quickly.

An alternative way of looking at the problem would be to get dhcpcd to run later in the process, after the configuration has happened. You could either put some insane amount of time delay between when wpa_supplicant is started and when dhcpcd is started or your could just run dhcpcd manually so you know that the wireless card is configured properly before an IP address is requested.

warmana · 11-17-2006, 08:41 AM

Hangdog42: Good idea, I'll look at doing that. Thank you :-)