Johannes Berg wrote:
Because in the case of hidden SSIDs, wpa_supplicant pretty much says to
use ap_scan=2.
There are a few problems here:
1) Historically, some drivers worked better with ap_scan=1 (madwifi),
others worked better with ap_scan=2 (many fullmac drivers)
2) scan_ssid=1 hasn't worked consistently on all drivers because it's
pretty new and many drivers don't support it yet. This is supposed to
make the driver/firmware send out probe request for the SSID in
question.
So basically, we're up shit creek without a paddle. You have to use
ap_scan=2 on some cards because they don't support specific-ssid
scanning (with scan_ssid=1) to find the BSS you want to connect to, but
some cards can handle ap_scan=1+scan_ssid=1 OK.
Fun. I'm pretty sure mac80211 handles ap_scan=1/scan_ssid=1 fine,
sending probe requests for that specific SSID.
yes it does an work fine that way. but ap_scan=2 = no go.
I can get some logs tomorrow for you.
If I remeber correctly wpa_supplicant just says "Got X scan results" and
never find the ssid asked for.
NM has logic to cache the BSSIDs of APs you've connected to before, and
to match those up with an SSID when it sees them in the scan list if the
AP isn't broadcasting the SSID. Unfortunately, that information isn't
available to wpa_supplicant because wpa_supplicant doesn't have an
interface to handle that sort of thing. Therefore, when faced with an a
request to connect to a hidden network, wpa_supplicant must rely
_entirely_ on the driver Doing The Right Thing with scan_ssid=1 or
ap_scan=2, and that almost never works due to inconsistency in driver
implementation.
Who invented hidden SSIDs anyway? Well, I guess I can actually test this
now that I finally have a second mac80211-based wireless card, although
iwl4965 is special wrt. scanning. I guess the trick will be to make
ap_scan=2 work although ap_scan=1/scan_ssid=1 works much better :(
well a "fix" would be for nm to try ap_scan=2 when it fails fall back to
ap_scan=1 + scan_ssid=1 bt thats nothing more than a hack.
We can fix that in nl80211 by making sure that scan_ssid is implemented
right away and whoever has nl80211 support needs to support that so that
we can rely on it...
yes that should finally fix it ... but until then we need something that
works.
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