On Tue, 2014-02-11 at 17:33 +1100, James Cameron wrote: > G'day, > > I'd appreciate a sanity check, as I'm not sure what I am doing. > > We saw for years that scan results for an OLPC XO-1 laptop would be > unreliable in large groups. APs would not be easily found. We > presumed other causes until recently. > > Using monitor mode on another computer, and "iwlist eth0 scan" on the > XO-1, I found probe responses from an AP, and ACKs from the host to > the AP, but the output omitted the AP. > > Further, the AP would be missing if there was a probe response from > another XO-1 running mesh, and an ACK from the host to that XO-1. > > Enabling debugging, lbs_ret_scan was reporting "scan response: invalid > IE fmt" because the probe response had a zero length SSID IE. > > Is a zero length SSID IE valid? (We can't change the wireless firmware > at this stage.) I think technically a zero-length IE would be valid, but I'm not sure about a zero-length *SSID* IE. Is that zero length SSID IE coming from an AP, or from an XO? If the scan was a passive scan, then a zero-length SSID IE *would* be valid, since the passive scans usually just listen for beacons, and hidden APs wouldn't report a real SSID. So perhaps what's happening here is if there is a hidden AP, the firmware sometimes gets the beacon from the AP before the AP responds to the XO's probe request? In any case, I think the patch is OK. Dan > Background data and dmesg fragments: > http://dev.laptop.org/ticket/12757 > > Patch being tested (lacks signoff and any review): > http://dev.laptop.org/git/olpc-kernel/commit/?h=x86-3.3&id=e98f01abce522fb70a3852b23b62205244ef69b8 > -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
