On Sun, 2014-06-22 at 18:22 -0600, Steve Brown wrote: > I have an RTL8188CUS dongle. My test setup is a Beaglebone black w/ > wireless-testing of a few days ago on a debian rootfs. It is set up as > an unencrypted station. The AP uses a Ubiquiti SR71-A (AR9160), has been > in service for some time, is running compat-wireless-2014-05-22 and > isn't suspect. > > After scp'ing several 10MB files in either direction, traffic stops. > Well, not all the traffic. If I ping the AP, Wireshark on a separate > computer and monitor interface shows that the ping from the station gets > on the air and so does the AP's ack, but no ping reply is sent by the > AP. ARP broadcasts from the station are ack'ed and responded to, just > not the pings. If I run tcpdump on the station's interface, it shows the > ARP packets and their response and any other broadcast traffic, just not > the ping or reply. Lastly, this only occurs in HT mode. > > I've compared the Wireshark dumps of the pings from before the interface > hangs up and after and can't see any difference. > After looking at some more wireshark output, the problem seems to be that the aggregation sessions deadlock when a second one starts before the first one completes. That would explain why it only occurs in HT mode. The sequence on the air before the deadlock is: STA->AP block ack req STA->AP ping req AP->STA block ack resp AP->STA ping resp AP->STA block ack req STA->AP block ack resp The sequence on the air after the deadlock is: AP->STA block ack req STA->AP block ack req AP->STA block ack resp STA->AP block ack resp STA->AP ping req ... STA->AP ping req (repeats) I noticed a fix for a similar problem with ath9k in the description of patch: ath9k: prevent aggregation session deadlocks 08c96abd611beadf2af414a306fe0fb02ba706ff Steve -- 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
