On 07/03/2015 08:38 PM, Johannes Berg wrote: > On Fri, 2015-07-03 at 18:51 +0200, Zefir Kurtisi wrote: >> Folks, >> >> I have difficulties using iw for a specific use case or fail to >> understand the documentation correctly. >> >> My platform is a recent OpenWRT, running ath9k. >> >> First use case is scanning for a given ssid in managed mode. >> According do iw's documentation (and the attribute description in >> nl80211.h), issuing >> >> iw dev wlan0 scan flush ssid <SSID> >> >> should do exactly this, but I keep receiving a full list of visible >> APs. > > This is telling it to scan for that particular network, and that's what > it's going to do, but it's still going to report everything that it > heard, for example when hearing beacons while scanning. > Ah, that explains it. Though, intuitively when providing an SSID to scan for, I'd expect other networks seen not to be displayed. If this is of general interest, I could work out some extension to iw and provide a related patch. >> The second issue is about scanning in AP mode. Where I want to go is >> having two >> APs operating on arbitrary DFS channels with periodic scans to >> discover each >> other. What I observe is >> a) passive scanning: iw dev wlan0 scan flush ap-force passive >> => does not work - no scan results are provided >> b) active scanning: iw dev wlan0 scan flush ap-force >> * finds only a subset of APs compared to a scan in managed mode >> * finds only APs on non-DFS channels >> >> Again, I might be missing some relevant documentation, but to me the >> observed results look rather like 'not yet implemented' than inherent >> limitations. >> > > Not sure - but you do need to realize that the AP isn't really allowed > to go off-channel for any period of time (like scanning) so this isn't > really guaranteed to work well. Especially passive scanning seems like > a really bad idea. As to why it's not actually working, I have no idea. > Your confirmation that scanning in AP mode is not reliable helps a lot. As for the 'bad idea', this is a special case: the APs don't provide a service at all, they only need to discover each other reliably in a mobile environment. I assumed AP background scanning would do the trick out of the box, but now will move to a time multiplexed AP / STA operation. > johannes Thanks a lot, Zefir -- 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
