On Fri, Jan 22, 2010 at 4:11 PM, Guy, Wey-Yi <wey-yi.w.guy@xxxxxxxxx> wrote: > On Fri, 2010-01-22 at 15:44 -0800, Luis R. Rodriguez wrote: >> On Fri, Jan 22, 2010 at 11:46 AM, Johannes Berg >> <johannes@xxxxxxxxxxxxxxxx> wrote: >> > On Fri, 2010-01-22 at 11:20 -0800, Luis R. Rodriguez wrote: >> > >> >> > Previously, we would switch the channel completely to the new operating >> >> > channel before even probing the AP. That way, we would virtually always >> >> > receive a beacon from the new AP between the time we started the >> >> > association process (probe,auth,assoc) and configuring the driver. >> >> > >> >> > Now with the new changes that use the off-channel work, we may return to >> >> > the old "operating" channel, which may be no particular channel, between >> >> > all these steps. Thus, if there's no beacon between any of probe >> >> > request/response, auth "request"/"response", assoc request/response, we >> >> > never get one, and this situation happens. >> >> > >> >> > I see two solutions, apart from this special-case patch fixing >> >> > >> >> > First, we could go back to the original behaviour if we have just one >> >> > virtual interface. But that still leaves us with the race, we might do >> >> > all three frame exchanges within a beacon interval and still miss the >> >> > beacon, we just tend to not do that and get a beacon. >> >> >> >> Curious, what symptoms were seen when the dtim was not propagated >> >> prior to association, did the STA just not wake up for the right dtim >> >> interval when in PS mode? >> > >> > Yes, I don't really know exactly what happens, >> >> OK -- Wey, can you elaborate a little as to how you found this and >> what you were seeing? Does the device not go into PS mode at all? > > We are doing Power consumption test with different DTIM value, the test > is based on test scripts, so we disable the NetworkManager to make sure > we can control which AP we need to associated with. During the test, we > notice when AP change it DTIM value, a lot time STA will used the old > DTIM value in Power Save mode which cause problem. Ah I see. What if there was no old dtim value before? > We believe the correct fix is mac80211 should wait for both probe > response and beacon arrived before start the association process. > > Hope this explain what we found. Indeed, thanks a lot. Luis -- 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
