2010/12/27 Bernhard Schmidt <bschm...@freebsd.org>: > Hi, > > I recently received some complains about the infamous 'ifconfig scan hang' > issue again. Finally looking into that I noticed a bunch of inconsistences, > the most obvious one is that ifconfig(8) is talking about doing a background > scan by default, which is simply not true according to the implementation. > > Anyways.. the generic use-case which triggers the 'hang' is, if 'ifconfig > scan' is called while a scan is already in progress, net80211 will not start a > new one which means that no scan flags are updated, though, ifconfig will loop > until it receives a notification about the scan being done. This does always > happen after an 'ifconfig up', because net80211 will move the VAP into scan > state by default, with the scan flags set in such a way that a scan is done > until there is something to connect to. This also means that no notifications > about the scan being done are sent to upper layers, because the scan is not > finished.. > > If we successfully moved from scan to run state, how so ever, and now want to > call 'ifconfig scan' we're faced with another issue. Doing a scan while being > associated means we have to move off our current channel, to do this without > loosing any imported frames/information, we make use of the power save > feature. Now if we want to send any traffic while doing the scan, the scan is > temporary suspended, frames are sent, then the scan is restarted after > receiving a beacon and there is no frame to send. For this to work though, we > need to actually request a background scan so appropriate flags are set and > the scan is actually restarted. Without this, we hang until the bgscan timer > fires of at that next bgscanintval. > > I have a patch available which addresses both of the issues. It requests a > background scan by default and also honors the return value of > start_scan_locked(): > - for head > http://techwires.net/~bschmidt/scan_hang_head.diff > - for 8-stable/8.2-*: > http://techwires.net/~bschmidt/scan_hang_stable.diff > > Please test and let me know if it works, or not.
Bernard, thanks a lot for working on this. There is any receipt for easilly reproduce this type of bug, or I should just go with 'ifconfig scan' repeteadly? I recall I could trigger it, but not 100% of times, so if you have more hints about how this problem could be reproduced, I'd be glad to hear. Thanks, Attilio -- Peace can only be achieved by understanding - A. Einstein _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
